U.S. patent application number 14/203861 was filed with the patent office on 2015-09-17 for band hardness and transverse control.
The applicant listed for this patent is Michael J. McLain, Timothy Pendley. Invention is credited to Michael J. McLain, Timothy Pendley.
Application Number | 20150259936 14/203861 |
Document ID | / |
Family ID | 54065575 |
Filed Date | 2015-09-17 |
United States Patent
Application |
20150259936 |
Kind Code |
A1 |
Pendley; Timothy ; et
al. |
September 17, 2015 |
BAND HARDNESS AND TRANSVERSE CONTROL
Abstract
This invention provides fall protection systems, in metal
building construction, and methods of installing such systems, a
given such system comprising a suspension fabric, supported by a
grid-work of longitudinal and lateral support bands. The fall
protection system uses safety clips to attach lateral bands to
intermediate purlins, such that the safety clips accommodate
flow-through longitudinal movement of the lateral bands through the
safety clips. The invention further provides relatively softer,
more extensible, support bands. The system, using the softer
support bands, in combination with the flow-through longitudinal
movement of the safety bands through the safety clips, distributes
the impact of a falling load over an increased number of members of
the structural members of the building resulting in enhanced
capacity for the fall protection system to catch and hold falling
loads.
Inventors: |
Pendley; Timothy; (Madera,
CA) ; McLain; Michael J.; (Green Bay, WI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Pendley; Timothy
McLain; Michael J. |
Madera
Green Bay |
CA
WI |
US
US |
|
|
Family ID: |
54065575 |
Appl. No.: |
14/203861 |
Filed: |
March 11, 2014 |
Current U.S.
Class: |
182/138 ;
29/428 |
Current CPC
Class: |
E04D 13/1625 20130101;
E04G 21/3266 20130101; Y10T 29/49826 20150115 |
International
Class: |
E04G 21/32 20060101
E04G021/32 |
Claims
1. A fall protection system in a building roof structure, for
protecting workers involved in installation of such roof structure,
such building roof structure including structural roof elements
including at least first and second rafters, a space between said
first and second rafters defining a first distance between said
first and second rafters, each said rafter having a length, a top,
and opposing first and second ends, said roof structure further
comprising an cave, having a length, and extending between the
first ends of said first and second rafters, a ridge, having a
length, and extending between the second ends of said first and
second rafters, and a second distance between said cave and said
ridge, said cave and said ridge being disposed on, extending
transverse to, and being connected to, the tops of said first and
second rafters, and a plurality of intermediate purlins extending
between said first and second rafters and spaced from each other
between said cave and said ridge, said intermediate purlins being
disposed on, and extending transverse to, the tops of said first
and second rafters, said fall protection system comprising: (a) a
first set of support bands extending from said first rafter to said
second rafter and being connected to said building structural roof
elements, said first set of support bands being spaced along the
lengths of said first and second rafters; (b) a second set of
support bands extending from said cave toward said ridge and under
said intermediate purlins, said bands of said second set of support
bands having first and second end portions and being spaced along
the lengths of said eave and said ridge; and (c) a suspension
fabric overlying, and being supported by, said first and second
sets of support bands, and being attached to said building
structural roof elements, said first and second sets of support
bands collectively defining a grid of crossing bands, a first band
of said second set of support bands, next adjacent said first
rafter, having at least one of (i) a yield strength of 45 ksi to 85
ksi, or (ii) a tensile strength of 60 ksi to 90 ksi, or (iii) an
elongation of 12 percent to 40 percent, said first band being
attached to said building roof structure for restraint of
longitudinal movement of said band at less than all of said
intermediate purlins.
2. A fall protection system as in claim 1, said first band having
at least one of (i) a yield strength of 45 ksi to 75 ksi, or (ii) a
tensile strength of 65 ksi to 85 ksi, or (iii) an elongation of 22
percent to 37 percent.
3. A fall protection system as in claim 1, said first band having a
hardness of 50 Rockwell B to 85 Rockwell B.
4. A fail protection system as in claim 2, said first band having
hardness of 55 Rockwell B to 60 Rockwell B.
5. A fall protection system as in claim 1, said first band having a
hardness of 64 Rockwell B to 79 Rockwell B.
6. A fail protection system as in claim 1, said first band having a
hardness of 70 Rockwell B to 75 Rockwell B.
7. A fall protection system as in claim 1 wherein said first band
is attached to said building roof structure, for restraint of
longitudinal movement, at locations spaced from each other by at
least 10 feet.
8. A fall protection system as in claim 1 wherein said first band
is attached to said building roof structure, for restraint of
longitudinal movement, at locations spaced from each other by at
least 20 feet.
9. A fall protection system as in claim 1 wherein said first band
is attached to said building roof structure, for restraint of
longitudinal movement, at locations spaced from each other by at
least 25 feet.
10. A fall protection system as in claim 4 wherein said first band
is attached to said building roof structure only at said first and
second end portions.
11. A fall protection system as in claim 1, a safety clip being
attached to a bottom flange of said one of said intermediate
purlins, said safety clip, either alone or in combination with said
one intermediate purlin, defining an opening at or adjacent said
intermediate purlin, said first band extending through such opening
and wherein sides of such opening confine said first band in such
opening relative to lateral movement of said first band while
accommodating generally unrestricted longitudinal movement of said
first band through such opening.
12. A fail protection system as in claim 11, said first band having
at east one of (i) a yield strength of 45 ksi to 75 ksi, or (ii) a
tensile strength of 65 ksi to 85 ksi, or (iii) an elongation of 22
percent to 37 percent, or (iv) a hardness of 60 Rockwell B to 79
Rockwell B.
13. A fall protection system as in claim 3, said first band
comprising a safety band, said band grid comprising a said safety
band next adjacent each side of each rafter in any portion of said
building roof structure where said band grid supports said
suspension fabric.
14. A fail protection system as in claim 12, said first band
comprising a safety band, said band grid comprising a said safety
band next adjacent each side of each rafter in any portion of said
building roof structure where said band grid supports said
suspension fabric.
15. A fall protection system as in claim 14 said suspension fabric
extending, as a generally flat sheet, across an open expanse
bounded by said first rafter, said ridge, said second rafter, and
said eave, said suspension fabric being supported by said first and
second sets of bands and being restrained against movement along
such structural roof elements by attachments of said suspension
fabric to said first and second rafters, to said eave proximate a
first end of said suspension fabric and to another one of such
structural roof elements proximate a second opposing end of said
suspension fabric.
16. A fall protection system as in claim 14, said fall protection
system being of sufficient strength to catch and support a weight
of 400 pounds, distributed over a diameter of approximately 30
inches, when dropped from a height of about 54.5 inches.
17. A fall protection system in a building roof structure, for
protecting workers involved in installation of such roof structure,
such building roof structure including structural roof elements
including at least first and second rafters, a space between said
first and second rafters defining a first distance between said
first and second rafters, each said rafter having a length, a top,
and opposing first and second ends, said roof structure further
comprising an eave, having a length, and extending between the
first ends of said first and second rafters, a ridge, having a
length, and extending between the second ends of said first and
second rafters, and a second distance between said eave and said
ridge, said eave and said ridge being disposed on, extending
transverse to, and being connected to, the tops of said first and
second rafters, and a plurality of intermediate purlins extending
between said first and second rafters and spaced from each other
between said eave and said ridge, said intermediate purlins being
disposed on, and extending transverse to, the tops of said first
and second rafters, said fall protection system comprising: (a) a
first set of support bands extending from said first rafter to said
second rafter and being connected to said building structural roof
elements, said first set of support bands being spaced along the
lengths of said first and second rafters; (b) a second set of
support bands extending from said eave toward said ridge and under
said intermediate purlins, said bands of said second set of support
bands having first and second end portions and being spaced along
the lengths of said eave and said ridge; and (c) a suspension
fabric overlying, and being supported by, said first and second
sets of support bands, and being attached to said building
structural roof elements, said first and second sets of support
bands collectively defining a grid of crossing bands, a first band
of aid second set of support bands, next adjacent said first
rafter, having at least one of (i) a yield strength of 50 ksi to 60
ksi, and (ii) a hardness of 60 Rockwell B to 79 Rockwell B, said
first band being attached to said building roof structure for
restraint of longitudinal movement of said band at less than all of
said intermediate purlins, a safety clip being attached to a bottom
flange of said one of said intermediate purlins, said safety clip,
either alone or in combination with said one intermediate purlin,
defining an opening at or adjacent said intermediate purlin, said
first band extending through such opening and wherein sides of such
opening confine said first band in such opening relative to lateral
movement of said first band while accommodating generally
unrestricted longitudinal movement of said first band through such
opening.
18. A fall protection system as in claim 17 wherein said first band
is attached to said building roof structure only at said first and
second end portions.
19. A fall protection system as in claim 17 said first band having
an elongation of 22 percent to 37 percent.
20. A fall protection system as in claim 17, said first band having
a tensile strength of 65 ksi to 65 ksi.
21. A fall protection system as in claim 17 wherein said first band
is attached to said building roof structure, for restraint of
longitudinal movement, at locations spaced from each other by at
least 10 feet.
22. A fall protection system as in claim 17 wherein said first band
is attached to said building roof structure, for restraint of
longitudinal movement, at locations spaced from each other by at
least 20 feet.
23. A fall protection system as in claim 17, said first band
comprising a safety band, said band grid comprising a said safety
band next adjacent each side of each rafter in any portion of said
building roof structure where said band grid supports said
suspension fabric.
24. A method of providing fall protection, as a fall protection
system, in a building which is under construction, for protecting
workers involved in construction of such building, the building
having building structural roof elements in place, including at
least first and second rafters, spaced from each other by a first
distance between the first and second rafters, each rafter having a
length, an upper surface, and opposing first and second ends, the
roof structure further comprising an eave, having a length, and
extending between the first ends of the first and second rafters,
the building structural roof elements further comprising a ridge,
having a length, and extending between the second ends of the first
and second rafters, and a second distance between the eave and the
ridge, the eave and the ridge being disposed on, extending
transverse to, and being connected to, the tops of the first and
second rafters, and a plurality of intermediate purlins extending
between the first and second rafters and spaced from each other
between the eave and the ridge, the intermediate purlins being
disposed on, and extending transverse to, the tops of the first and
second rafters, the method comprising: (a) installing a first set
of longitudinal support bands extending from the first rafter to
the second rafter and connecting the longitudinal support bands to
the building structural roof elements, the longitudinal support
bands being spaced along the lengths of the first and second
rafters: (b) installing a second set of lateral support bands
extending from the cave toward the ridge and under the intermediate
purlins, the lateral support bands being spaced along the lengths
of the cave and the ridge and supporting the longitudinal support
bands, including installing, as the lateral support bands next
adjacent the rafters, bands having at least one of (i) a yield
strength of 45 ksi to 85 ksi, or (ii) a tensile strength of 60 ksi
to 90 ksi, or (iii) an elongation of 12 percent to 40 percent; (c)
installing a suspension fabric over the first and second sets of
support bands and under the intermediate purlins such that the
suspension fabric is supported by the first and second sets of
support bands; (d) positioning one or more safety clips about the
lateral support bands which are next adjacent the rafters, and
attaching the respective safety clips to respective ones of the
intermediate purlins, each safety clip, either alone or in
combination with the respective intermediate purlin, defining an
opening at or proximate the intermediate purlin, such that the
respective lateral bands are attached to the respective purlins, at
least in part, by the safety clips and are confined, by walls of
the openings, proximate the respective intermediate purlins,
against lateral movement, while experiencing generally unrestricted
longitudinal movement through the openings; and (e) positioning the
remaining lateral bands up against the overlying intermediate
purlins and fastening such remaining lateral bands to the
respective overlying intermediate purlins.
25. A method as in claim 24 wherein the lateral support bands about
which the safety clips are positioned have at least one of (i) a
yield strength of 50 ksi to 65 ksi, or (ii) a tensile strength of
65 ksi to 85 ksi, or (iii) an elongation of 22 percent to 37
percent.
26. A method as in claim 24 wherein the lateral support bands about
which the safety clips are positioned have hardnesses of 50
Rockwell B to 80 Rockwell B.
27. A method as in claim 25 wherein the lateral support bands about
which the safety clips are positioned have hardnesses of 50
Rockwell B to 80 Rockwell B.
28. A method as in claim 24 wherein the lateral support bands about
which the safety clips are positioned have hardnesses of 60
Rockwell B to 79 Rockwell B.
29. A method as in claim 24 wherein the lateral support bands about
which the safety clips are positioned have hardnesses of 70
Rockwell B to 75 Rockwell B.
30. A method as in claim 24 wherein the first band is attached to
the building roof structure, for restraint of longitudinal
movement, at locations spaced from each other by at least 20
feet.
31. A method as in claim 27 wherein the first band is attached to
the building roof structure only at the first and second end
portions.
32. A method as in claim 24 wherein the first band has at least one
of (i) a yield strength of 50 ksi to 65 ksi, or (ii) a tensile
strength of 65 ksi to 85 ksi, or (iii) an elongation of 22 percent
to 37 percent, or (iv) a hardness of 50 Rockwell B to 80 Rockwell
B.
33. A method as in claim 32, the first and second sets of support
bands define a band grid and wherein the lateral bands next
adjacent each rafter is a safety band, the band grid comprising a
such safety band, extending through a such safety clip at each
intermediate purlins next adjacent each side of each rafter in any
portion of the building roof structure where the hand grid supports
the suspension fabric.
34. A method as in claim 33, the fall protection system being of
sufficient strength to catch and support a weight of 400 pounds,
distributed over a diameter of approximately 30 inches, when
dropped from a height of about 50.5 inches.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to buildings, building components,
building subassemblies, and building assemblies, and to methods of
constructing buildings. This invention relates specifically to
components, subassemblies, and assemblies, as parts of the
building, and to the issue of worker safety during the construction
of buildings.
[0002] From time to time, injuries occur during construction of
buildings, including to workers who fall from elevated heights. The
focus of this invention is to enable a building contractor to
reduce, desirably to eliminate, the number of incidents of worker
injuries resulting from workers falling from elevated heights while
working on construction of the building.
[0003] Governmental safety organizations, for example the
Occupational Safety and Health Administration (OSHA) in the US,
have promulgated required safety standards, and safety practices to
generally provide safety systems which capture and support workers
who are working at substantial heights above supporting surfaces,
to protect such workers, namely to stop a fall, and to support such
workers if/when such workers do fall. But it is up to the industry
to create fall protection systems which meet the required
standards.
[0004] Pre-engineered metal building systems are the predominant
method of non-residential low rise construction for buildings.
Existing fall protection standards have substantial impact on the
contractors involved in such pre-engineered metal building
systems.
[0005] One way a worker can be protected, according to the
standards, is for the worker to wear a safety harness which is
tied, by a strap, to the building structure at elevation such that
the harness/strap combination stops any fall which the worker
experiences before the worker encounters an underlying surface such
as a floor or the ground. Use of such safety harness is known as
"tying off". But tying the harness to the building limits the
worker's mobility, as well as the worker's range of movement. Thus,
tie-off harnesses are not viewed favorably in the industry because
of worker inefficiency.
[0006] Another way workers can be protected is for the building
contractor to erect safety nets in order to provide leading edge
protection against falls. Cost and maintenance of such safety nets,
as well as the equipment and expense required for erecting and
dismantling the net and associated equipment, and moving and
storing the net and equipment, can be a substantial increment in
the per square foot cost of especially the roof insulation system
being installed.
[0007] With the anticipation of expanded enforcement efforts by
OSHA, building erectors have increased incentive to find ways to
meet the existing fall protection requirements.
[0008] Another acceptable fall protection system is a passive
system wherein a fabric, such as a solid sheet, a woven sheet, or a
net-like material, is suspended at or below the work area,
optionally supported by a grid of crossing support bands, far
enough above any underlying supporting surface to catch and support
a worker who falls, thereby to act as a passive fall-protection
system.
[0009] OSHA has defined a drop test procedure whereby a such
passive fall protection system can be tested. According to the test
procedure, a 400 pound weight is dropped onto the fall protection
system under stated conditions to determine whether a given system
meets the required safety standards. For purposes of complying with
government regulations, any system used as a fall protection system
need only meet the OSHA-mandated standards related to dropping such
400 pound weight. Of course, the real humanitarian objective is to
prevent worker injuries if/when a worker falls from an elevated
work location. Thus, any fall protection system which is effective
to catch and safely hold a falling worker has operational value,
even if such system does not meet OSHA standards.
[0010] According to one aspect of the prior art, currently in use
in the metal building industry, and intended to meet government
fall protection standards, a purported fall protection system uses
crossing longitudinal and lateral metal bands extending under the
eave, under the ridge, and under the intermediate purlins, and a
fabric is installed above the bands and under the purlins,
extending across the entirety of a respective bay of the building
being constructed, and secured to the building structure at the
edges of such fabric, thereby providing a suspended fabric intended
to catch and support a falling worker in that bay. Insulation is
ultimately installed on the top surface of the fabric whereby the
fabric ultimately functions as the vapor-barrier portion of the
building insulation system in the finished building.
[0011] Testing has shown that currently-available such systems meet
the government-mandated drop test standard at certain locations in
the bay of a metal building under construction, while failing such
drop test at other locations. Typically, such systems fail the drop
test adjacent an edge of the bay, where any worker accidental fall
is most likely to occur. Thus, the user cannot be assured that a
falling worker will be caught and supported at whatever location
he/she falls from the elevated work location. Such failure can
result in worker injury, along with the numerous detrimental
results of such injury, as well as resulting government citations
associated with the resulting injury, and associated monetary fines
and/or assessments, civil lawsuits, and the like.
[0012] Accordingly, there is a need for a novel passive fall
protection system for use during construction of metal buildings
which effectively catches and supports a falling worker working at
an elevated height anywhere in the corresponding bay being worked
on, and which system meets all governmental safety standards.
[0013] There is also a need to provide a portion of a building
insulation system which functions to provide effective fall
protection during construction of the building, while meeting the
existing governmental fall protection requirements.
[0014] There is further a need for methods of mounting fall
protection systems to building structural members during
construction of such metal buildings, fall protection systems which
effectively catch and support a worker falling from an elevated
height, and which systems meet all governmental safety
standards.
[0015] These and other needs are alleviated, or at least
attenuated, or partially or completely satisfied, by novel
products, systems, and methods of the invention.
SUMMARY OF THE INVENTION
[0016] This invention provides fall protection systems comprising a
suspension fabric, supported by a grid-work of longitudinal and
lateral support bands, used to protect workers working at heights
against falls onto underlying support surfaces, during construction
of such metal buildings. The fall protection system uses safety
clips to attach lateral bands to intermediate purlins, such that
the respective lateral bands are attached to less than all, or
none, of the intermediate purlins, whereby the relatively longer
unfastened lengths of the lateral bands, at critical locations in
the fall protection system, enables the system to distribute the
force/shock of a load dropping onto the system over relatively
longer lengths of the respective lateral bands, and to the eave and
ridge as well as to the intermediate purlins, thus reducing the
magnitude of a remainder portion of the shock/force of the fallen
load which must be absorbed by the fabric. In addition, the
invention provides relatively softer, more extensible, support
bands. The system, using the softer support bands, in combination
with flow-through longitudinal movement of the safety bands through
the safety clips, thus distributes the impact of a falling load
over an increased number of members of the structural members of
the building resulting in enhanced capacity for the fall protection
system to catch and hold falling loads.
[0017] In a first family of embodiments, the invention comprehends
a fall protection system in a building roof structure, for
protecting workers involved in installation of such roof structure,
the building roof structure including structural roof elements
which include at least first and second rafters, a space between
the first and second rafters defining a first distance between the
first and second rafters, each rafter having a length, a top, and
opposing first and second ends, the roof structure further
comprising an eave, having a length, and extending between the
first ends of the first and second rafters, a ridge, having a
length, and extending between the second ends of the first and
second rafters, and a second distance between the eave and the
ridge, the eave and the ridge being disposed on, extending
transverse to, and being connected to, the tops of the first and
second rafters, and a plurality of intermediate purlins extending
between the first and second rafters and spaced from each other
between the eave and the ridge, the intermediate purlins being
disposed on, and extending transverse to, the tops of the first and
second rafters, the fall protection system comprising a first set
of longitudinal support bands extending from the first rafter to
the second rafter and being connected to the building structural
roof elements, the first set of longitudinal support bands being
spaced along the lengths of the first and second rafters; a second
set of lateral support bands extending from the eave toward the
ridge and under the intermediate purlins, the bands of the second
set of lateral support bands having first and second end portions
which are spaced along the lengths of the eave and the ridge; and a
suspension fabric overlying, and being supported by, the first and
second sets of support bands, and being attached to the building
structural roof elements, the first and second sets of support
bands collectively defining a grid-work of crossing bands, a first
band of the second set of support bands, next adjacent the first
rafter, having at least one of (i) a yield strength of 45 ksi to 85
ksi, or (ii) a tensile strength of 60 ksi to 90 ksi, or (iii) an
elongation of 12% to 40%, the first band being attached to the
building roof structure for restraint of longitudinal movement of
the band at less than all of the intermediate purlins.
[0018] In some embodiments, the first band has at least one of (i)
a yield strength of 45 ksi, to 75 ksi, or (ii) a tensile strength
of 65 ksi to 85 ksi, or (iii) an elongation of 22% to 37%.
[0019] In some embodiments, the first band has a hardness of 50
Rockwell B to 85 Rockwell B, optionally 55 Rockwell B to 80
Rockwell B, optionally 64 Rockwell B to 79 Rockwell B, optionally
70 Rockwell B to 75 Rockwell B.
[0020] In some embodiments, the first band is attached to the
building roof structure, for restraint of longitudinal movement, at
locations spaced from each other by at least 10 feet, optionally at
least 20 feet, optionally at least 25 feet.
[0021] In some embodiments, the first band is attached to the
building roof structure only at the first and second end
portions.
[0022] In some embodiments, the first band, when in a generally
horizontally-extending orientation, has a generally
horizontally-extending length, a generally horizontally-extending
width, and a generally vertically-extending thickness, a safety
clip being attached to a bottom flange of the one of the
intermediate purlins, the safety clip, either alone or in
combination with the one intermediate purlin, defining an opening
at or adjacent the intermediate purlin, the first band extending
through the opening and sides of the opening confine the first band
in the opening relative to lateral movement of the first band while
accommodating generally unrestricted longitudinal movement of the
first band through the opening.
[0023] In some embodiments, the first band has at least one of (i)
a yield strength of 45 ksi to 75 ksi, or (ii) a tensile strength of
65 ksi to 85 ksi, or (iii) an elongation of 22% to 37%, or (iv) a
hardness of 60 Rockwell B to 79 Rockwell B.
[0024] In some embodiments, the first band comprises a safety band,
and the band grid comprises a safety band next adjacent each side
of each rafter in any portion of the building roof structure where
the band grid supports the suspension fabric.
[0025] In some embodiments, the suspension fabric extends, as a
generally flat sheet, across an open expanse bounded by the first
rafter, the ridge, the second rafter, and the eave, the suspension
fabric being supported by the first and second sets of bands and
being restrained against movement along the structural roof
elements by attachments of the suspension fabric to the first and
second rafters, to the save proximate a first end of the suspension
fabric and to another one of the structural roof elements proximate
a second opposing end of the suspension fabric.
[0026] In some embodiments, the fall protection system is of
sufficient strength to catch and support a weight of 400 pounds,
distributed over a diameter of approximately 30 inches, when
dropped from a height of about 50.5 inches.
[0027] In a second family of embodiments, the invention comprehends
a fall protection system in a building roof structure, for
protecting workers involved in installation of the roof structure,
the building roof structure including structural roof elements
including at least first and second rafters, a space between the
first and second rafters defining a first distance between the
first and second rafters, each rafter having a length, a top, and
opposing first and second ends, the roof structure further
comprising an save, having a length, and extending between the
first ends of the first and second rafters, a ridge, having a
length, and extending between the second ends of the first and
second rafters, and a second distance between the save and the
ridge, the save and the ridge being disposed on, extending
transverse to, and being connected to, the tops of the first and
second rafters, and a plurality of intermediate purlins extending
between the first and second rafters and spaced from each other
between the save and the ridge, the intermediate purlins being
disposed on, and extending transverse to, the tops of the first and
second rafters, the fall protection system comprising a first set
of support bands extending from the first rafter to the second
rafter and being connected to the building structural roof
elements, the first set of support bands being spaced along the
lengths of the first and second rafters; a second set of support
bands extending from the eave toward the ridge and under the
intermediate purlins, the bands of the second set of support bands
having first and second end portions and being spaced along the
lengths of the eave and the ridge; and a suspension fabric
overlying, and being supported by, the first and second sets of
support bands, and being attached to the building structural roof
elements, the first and second sets of support bands collectively
defining a grid of crossing bands, a first band of the second set
of support bands, next adjacent the first rafter, having at least
one of (i) a yield strength of 50 ksi to 60 ksi, and (ii) a
hardness of 60 Rockwell B to 79 Rockwell B, the first band being
attached to the building roof structure for restraint of
longitudinal movement of the band at less than all of the
intermediate purlins, the first band, when in a generally
horizontally-extending orientation, having a generally
horizontally-extending length, a generally horizontally-extending
width, and a generally vertically-extending thickness, a safety
clip being attached to a bottom flange of the one of the
intermediate purlins, the safety clip, either alone or in
combination with the one intermediate purlin, defining an opening
at or adjacent the intermediate purlin, the first band extending
through the opening and wherein sides of the opening confine the
first band in the opening relative to lateral movement of the first
band while accommodating generally unrestricted longitudinal
movement of the first band through such opening.
[0028] In some embodiments, the first band is attached to the
building roof structure only at the first and second end
portions.
[0029] In some embodiments, the first band has an elongation of 22%
to 37%.
[0030] In some embodiments, the first band has a tensile strength
of 65 ksi to 85 ksi.
[0031] In some embodiments, the first band is attached to the
building roof structure, for restraint of longitudinal movement, at
locations spaced from each other by at least 10 feet, optionally by
at least 20 feet.
[0032] In some embodiments, the first band comprises a safety band,
the hand grid comprising a safety band next adjacent each side of
each rafter in any portion of the building roof structure where the
band grid supports the suspension fabric.
[0033] In a third family of embodiments, the invention comprehends,
a method of providing fall protection, as a fall protection system,
in a building which is under construction, for protecting workers
involved in construction of such building, the building having
building structural roof elements in place, including at least
first and second rafters, spaced from each other by a first
distance between the first and second rafters, each rafter having a
length, an upper surface, and opposing first and second ends, the
roof structure further comprising an eave, having a length, and
extending between the first ends of the first and second rafters,
the building structural roof elements further comprising a ridge,
having a length, and extending between the second ends of the first
and second rafters, and a second distance between the eave and the
ridge, the eave and the ridge being disposed on, extending
transverse to, and being connected to, the tops of the first and
second rafters, and a plurality of intermediate purlins extending
between the first and second rafters and spaced from each other
between the cave and the ridge, the intermediate purlins being
disposed on, and extending transverse to, the tops of the first and
second rafters, the method comprising installing a first set of
longitudinal support bands extending from the first rafter to the
second rafter and connecting the longitudinal support bands to the
building structural roof elements, the longitudinal support bands
being spaced along the lengths of the first and second rafters;
installing a second set of lateral support bands extending from the
cave toward the ridge and under the intermediate purlins, the
lateral support bands being spaced along the lengths of the cave
and the ridge and underlying the longitudinal support bands,
including installing, as the lateral support bands next adjacent
the rafters, bands having at least one of (i) a yield strength of
45 ksi to 85 ksi, or (ii) a tensile strength of 60 ksi to 90 ksi,
or (iii) an elongation of 12% to 40%; installing a suspension
fabric over the first and second sets of support bands and under
the intermediate purlins such that the suspension fabric is
supported by the first and second sets of support bands;
positioning one or more safety dips about the lateral support bands
which are next adjacent the rafters, and attaching the respective
safety clips to respective ones of the intermediate purlins, each
safety clip, either alone or in combination with the respective
intermediate purlin, defining an opening at or proximate the
intermediate purlin, such that the respective lateral bands are
attached to the respective purlins, at least in part, by the safety
dips and are confined, by walls of the openings, proximate the
respective intermediate purlins, against lateral movement, while
experiencing generally unrestricted longitudinal movement through
the openings: and positioning the remaining lateral bands up
against the overlying intermediate purlins and fastening such
remaining lateral bands to the respective overlying intermediate
purlins.
[0034] In some embodiments, the lateral support bands about which
the safety clips are positioned have at least one of (i) a yield
strength of 50 ksi to 65 ksi, or (ii) a tensile strength of 65 ksi
to 85 ksi, or (iii) an elongation of 22% to 37%.
[0035] In some embodiments, the lateral support bands about which
the safety clips are positioned have hardnesses of 50 Rockwell B to
80 Rockwell B, optionally 60 Rockwell B to 79 Rockwell B,
optionally 70 Rockwell B to 75 Rockwell B.
[0036] In some embodiments, the first band is attached to the
building roof structure, for restraint of longitudinal movement, at
locations spaced from each other by at least 20 feet.
[0037] In some embodiments, the first band is attached to the
building roof structure only at the first and second end
portions.
[0038] In some embodiments, the first band has at least one of (i)
a yield strength of 50 ksi to 65 ksi, or (ii) a tensile strength of
65 ksi to 85 ksi, or (iii) an elongation of 22% to 37%, or (iv) a
hardness of 50 Rockwell B to 80 Rockwell B.
[0039] In some embodiments, the first and second sets of support
bands define a band grid wherein the lateral bands next adjacent
the rafters are safety bands, the band grid comprising a safety
band next adjacent each side of each rafter in any portion of the
building roof structure where the band grid supports the suspension
fabric.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] illustrative embodiments of the invention are described
hereinafter, by way of example only, with reference to the
accompanying drawings.
[0041] FIG. 1 shows a perspective view, from above the eaves, of a
typical metal building structure, including columns, rafters,
eaves, ridges, and intermediate purlins.
[0042] FIG. 2 is a perspective view, from above the roof, of part
of a bay of a metal building, showing columns, rafters, purlins, an
eave, and a grid-work of crossing bands.
[0043] FIG. 3 is a perspective view as in FIG. 2 showing a
suspension fabric partially extended over the band grid-work and
under the eave and under the purlins, in a single bay.
[0044] FIG. 4 is a diagrammatic end view of a roof structure of a
metal building, showing longitudinal band spacing with respect to
the eaves, the ridges, and the intermediate purlins.
[0045] FIG. 5 is an edge view showing a lateral band fastened,
attached to the bottom flange of the eave.
[0046] FIG. 6 shows a cross-section of an intermediate purlin, and
a Tek screw, with washer, positioned to extend the screw through
the fabric and into the purlin bottom flange.
[0047] FIG. 7 shows an end view of the safety clip designed and
configured to be mounted to the bottom flange of an intermediate
purlin.
[0048] FIG. 8 shows a bottom view of a safety clip of FIG. 7.
[0049] FIG. 9 shows an end view of a safety clip as in FIGS. 7 and
8 mounted to the bottom surface of the bottom flange of an
intermediate purlin, through an intermediate washer, using a single
Tek screw as in FIG. 6, and a safety band passing through the
opening in the safety clip, and being confined against free
lateral/transverse movement beyond the confines of the loop of the
safety clip.
[0050] FIG. 10 shows an end view as in FIG. 9, illustrating an
alternate safety clip design mounted to an intermediate purlin
using first and second screws.
[0051] FIG. 11 shows the safety clip mounted to the bottom, surface
of the bottom flange of the intermediate purlin as in FIG. 9, but
from an angle parallel to the bottom flange of the purlin and
perpendicular to the length of the purlin.
[0052] FIG. 12 shows a portion of a bay of a suspension system area
which includes the safety clip viewed as in FIG. 9, and first and
second next-adjacent lateral bands extending from eave to ridge,
the first band being secured against longitudinal movement only at
ridge and eave, the second band being secured against longitudinal
movement at every purlin.
[0053] FIG. 13 shows a portion of a suspension system as in FIG. 12
wherein the first band is secured, against longitudinal movement,
to one of the intermediate purlins.
[0054] FIG. 14 shows a portion of a suspension system as in FIG. 13
wherein the second band is secured: against longitudinal movement,
to fewer than all of the intermediate purlins
[0055] The invention is not limited in its application to the
details of construction, or to the arrangement of the components,
or to the methods of construction, set forth in the following
description or illustrated in the drawings. The invention is
capable of other embodiments or of being practiced or carried out
in various other ways. Also, it is to be understood that the
terminology and phraseology employed herein is for purpose of
description and illustration and should not be regarded as
limiting. Like reference numerals are used to indicate like
components.
[0056] FIG. 1 illustrates the primary structural members of a
typical metal building 10 having first and second roof slopes 12A
and 12B. Vertical support for the structural elements of the roof,
designated generally as 12, is provided by upstanding columns 14
positioned along side walls and end walls of the building. Rafters
16 overlie the tops of the columns and are supported by the
columns. Rafters 16 span the width of the building, creating a
series of open spaces between rafters 16, the open spaces being
commonly referred to as "bays" 18 in the construction arts, the
bays representing distances between respective ones of the rafters.
Each rafter has an upper surface 16A, and opposing first 16B and
second 160 ends.
[0057] According to the embodiments illustrated in FIGS. 1-4, eaves
20, expressing "C"-shaped cross-sections, are positioned at the
down-slope ends of the rafters 16. Lengths of the eaves extend
along the length of the building, above the outer wall of the
building. The eaves provide lateral support to the skeletal
structure of the building between respective ones of the columns
14, at the outer building wall. A given cave extends between the
first ends 16B of respective ones of the rafters.
[0058] Ridge members 22, expressing "Z"-shaped cross-sections as
illustrated in FIG. 4, have lengths which overlie, and are attached
to, the upper surfaces of rafters 16. The ridge members are
positioned at the up-slope ends of the rafters, and run the length
of the building parallel to the eaves, typically above the central
portion of the building. The ridge members provide lateral support
to the skeletal structure of the building between respective ones
of rafters 16, typically at an internal portion of the building,
away from the building side walls in the illustrated embodiments. A
given ridge member extends between the second ends 16C of the
respective ones of the rafters. Where the roof has a single pitch
direction, the ridge can be positioned proximate one of the outer
walls of the building.
[0059] The ridge members and the eave members overlie, extend
transverse to, and are attached to, the upper surfaces of the
respective rafters 16, and are spaced from each other by distances
which generally correspond to the lengths of the respective rafters
between ends 16B and 16C.
[0060] Intermediate purlins 24 express "Z"-shaped cross-sections.
The intermediate purlins overlie, extend transverse to, and are
attached to, upper surfaces 16A of the respective rafters. Purlins
24 are spaced from each other along the lengths of the rafters. The
purlins extend parallel to each other and parallel to any ridges
and eaves and, overall, span the length of the bay, whereby the
purlins are displaced from each other and from any ridges and eaves
along the spaces between the respective eave and the ridge.
[0061] As shown in FIG. 2, the fail protection support system,
namely the suspension system, of this invention includes a
supporting grid-work formed by crossing elongate steel bands,
including longitudinal support bands 26 and lateral support bands
28. Support bands 26, 28 of the grid-work are supported by various
ones of the building structural members, as described herein, and
the collective grid-work generally defines an imaginary plane,
extending into the sheet of the drawing illustrated in FIG. 4. Such
imaginary plane extends parallel to a set of imaginary straight
lines, spaced from each other and extending between the lower
surfaces of the eaves 20, the ridge 22, and intermediate purlins
24, and further extending parallel to imaginary straight lines
which connect the upper surfaces of the rafters.
[0062] Support bands 26, 28 support a high strength fabric 32, the
fabric being shown partially unfolded in FIG. 3 and, in FIG. 4, the
fabric is suggested by the dashed line under the eave, ridge, and
intermediate purlins, and above longitudinal bands 26, bands 26
being shown in FIG. 4 in end view. Fabric 32 in the illustrated
embodiments also serves as a vapor barrier for the insulation
system which is ultimately installed at the roof of the
building.
[0063] Starting with the structural skeleton of the building as
illustrated in FIG. 1, a fall protection system of the invention is
installed generally as follows. Longitudinal metal bands 26 are
extended from the upper surface of a first one of the rafters to
the upper surface of a second one of the rafters at angles which
are typically, but not necessarily, perpendicular to the respective
rafters. The number of longitudinal bands 26 depends to some degree
on the distance between the respective ones of the intermediate
purlins 24. In the invention, typically only a single longitudinal
band 26 is used between each pair of next-adjacent purlins 24.
However, in certain systems, which can be engineered based on the
technology disclosed herein, two or more longitudinal bands may be
used where such additional band use may be cost-effective and/or
when use of such additional band may be needed in order to satisfy
the respective governmental standard. Of course, the greater the
number of bands used, the greater the cost of the band system.
Accordingly, the user is motivated to have the system engineered so
as to use as few of such longitudinal bands as possible while
meeting the required safety standards.
[0064] A length of a given longitudinal band 26 extends across a
given bay and is extended across the upper surface of each rafter
overlain by the respective band, and is attached to the upper
surfaces, or other surfaces, of the respective rafters. Where the
longitudinal band 26 extends across multiple bays, the longitudinal
band is secured, for restrained longitudinal movement, to the upper
surfaces of those rafters which are most remote from one another.
Optionally, but not necessarily, the longitudinal band may be
secured to one or more intermediate rafters.
[0065] Longitudinal bands 26 are fastened to the rafters or rake
channels (not shown) which correspond with the end portions of the
bands by conventional attachment means such as by self-drilling
screws. Longitudinal bands 26 are pulled tight between the rafters
so as to, in part, and at this stage of installation, begin to
define the afore-mentioned band grid, and the imaginary plane of
support provided by the band grid, immediately under the
intermediate purlins. Band attachment tools, known in the art, may
be used in attaching the bands, either temporarily or permanently,
to the rafters or rake channels, thus to instill a suitable,
conventionally known, level of tension in bands 26 as the bands are
being installed.
[0066] Each cave has a top flange 34, a bottom flange 36, and an
upstanding web 38 extending between the top and bottom flanges, and
connecting the top flange to the bottom flange. The top and bottom
flanges are arranged such that the profile of the cave defines a
"C"-shaped structure, perhaps best seen in FIG. 5.
[0067] While the cave profiles shown define generally perpendicular
turns between the flanges 34 and 36, and upstanding web 38, actual
cave profiles typically define a modest acute angle (not shown)
between the bottom flange and the upstanding web and a
corresponding modest obtuse angle (not shown) between the top
flange and the upstanding web. Such acute and obtuse angles adapt
the cave to the specific slope of the roof for which the eaves are
designed, while providing that the upstanding web conform to the
vertical orientation of the respective side wall of the
building.
[0068] Correspondingly, each ridge has a top flange 40, a bottom
flange 42, and an upstanding web 44 extending between the top and
bottom flanges, and connecting the top flange to the bottom flange.
The top and bottom flanges are arranged such that the profile of
the ridge defines a "Z"-shaped structure, as illustrated in FIG.
4.
[0069] Similarly, each intermediate purlin has a top flange 46, a
bottom flange 48, and an upstanding web 50 extending between the
top and bottom flanges, and connecting the top flange to the bottom
flange. The top and bottom flanges are arranged such that the
profile of the respective purlin defines a "Z"-shaped structure,
illustrated in FIGS. 4 and 6.
[0070] Lateral bands 28 are installed after the longitudinal bands
26 are in place. Lateral bands 28 extend transverse to, typically
perpendicular to, the longitudinal bands. Lateral bands 28
generally underlie and support longitudinal bands 26. Lateral bands
28 may be first attached to the respective ridge 22. Bands 28 may
be attached to any suitable surface of the ridge which enables the
band to pass, from the location of attachment, under and in
tensioned contact with, the bottom flange of the ridge. For
example, a lateral band can be attached to the bottom surface of
the bottom flange of the ridge, with intervening fabric 32, and
extend from there toward the cave.
[0071] As an alternative, one end of a given lateral band can
extend up alongside, and be fastened to, the surface of the
upstanding ridge web which faces away from the cave on the
respective slope of the roof. The band passes alongside, and turns
about, the edge of the bottom flange of the ridge which faces away
from the respective cave, and then passes under, and in general
contact with, the bottom surface of the bottom flange, again with
intervening fabric, and extends from there toward the cave.
[0072] As a still further example of attachment of a lateral band
to the ridge, the band can be attached to the top surface of the
top flange, turn about the upper edge of the top flange which is
away from the respective eave, extend from there down toward the
bottom ridge flange, turn about the edge of the bottom flange and
pass alongside, and in general contact with, the bottom surface of
the bottom flange, and extend from there toward the cave, again
with the fabric between the band and the ridge.
[0073] The lateral bands are extended, from the bottom surface of
the bottom flange of the ridge toward the respective cave, passing
under the longitudinal bands, and pulled tight to minimize sag in
both the lateral bands and the respective overlying longitudinal
bands. The so-tightened lateral bands are in general contact, again
with intervening fabric, with the bottom surface of the bottom
flange of the respective cave. With the so-tightened lateral bands
in contact with the bottom surface of the bottom flange of the
respective cave, the lateral bands are fastened to the cave so as
to maintain the tension in the lateral bands, thus to lift the
lateral bands toward the bottom flanges of the overlying
intermediate purlins.
[0074] The number of lateral bands 28 to be used between a
respective pair of next-adjacent rafters, and the spacing between
the lateral bands, varies with the distance between the rafters.
Typically, the lateral bands are 36 inches to 40 inches apart,
optionally up to 48 inches apart in some cases.
[0075] Traditional banding stock used for bands 26 and 28 is a
hot-dip zinc/aluminum alloy-coated Grade 80 structural steel, 0.023
inch thick, having longitudinal tensile yield strength of at least
93 ksi, such Grade 80 banding sometimes being referred to in the
industry as "full hard". Such steel banding is typically about 1
inch wide and continuous length. Such traditional "full hard" steel
banding is available from Steelscape, A BlueScope Steel Company,
Kalama, Wash. as ZINCALUME.RTM. Steel Grade 80 (Class 1).
[0076] Representative properties of such Grade 80 (Class 1 banding,
0.023 inch thick, from Steelscape are as follows:
[0077] Yield strength--100.1 ksi average, 51.3-64.0 ksi range
[0078] Tensile strength--102.2 ksi average, 95.4-105.3 ksi
range
[0079] Elongation in 2 inch sample--10% average, 9.6-10.3%
range
[0080] Hardness, Rockwell B Scale--93.4 average, 92-95 range
[0081] "Ksi" means "thousands of pounds per square inch".
[0082] It is known that, when a fall protection system of the prior
art, using 0.023 inch Grade 80 banding, 1 inch wide, is tested
using the government-mandated test procedure, even if the system
successfully passes the test, namely catches and holds the falling
object, the suspension fabric tears at the screws which fasten the
fabric and bands to the purlins. Typically, the longitudinal
banding, and sometimes the lateral banding, closest to the falling
object, also breaks.
[0083] As a corrective measure, some commercially available alleged
fall protection systems require the use of two Tek screws, at least
two inches apart, through the lateral banding and into the bottom
flange of each respective eave. The purpose of the second screw is
believed to be to provide additional strength to the attachment of
the band to the eave, to prevent the band from tearing past the
screws, or tearing the screw diagonally out the side of the band,
when an object impacts the fall protection system fabric,
[0084] The determination of passing or failing the
government-defined drop test is whether the falling object proceeds
through the fabric, known as a test failure, or is successfully
held and supported by the fabric, which is a successful, passing of
the test.
[0085] The inventors herein have discovered, by their experience,
by their testing, that existing commercially available alleged fall
protection systems, even those using the two-screw attachment, fail
the government-defined drop test when the force is applied adjacent
a rafter, or anywhere the impact is passed directly to fewer than 4
bands surrounding the point of impact. Accordingly, the invention
contemplates novel lateral bands.
[0086] Known prior-art-alleged fall protection systems specify that
each lateral band be attached by a Tek screw to the bottom flange
of each intermediate purlin, whereby a substantial fraction of the
force of a worker falling, or the force of a drop test, is
transferred through the respective lateral bands to the next
adjacent purlins.
[0087] Where the force of a drop/impact/fall is applied at the
lateral band which is next-adjacent a rafter, that force may be
transferred by a single one of such lateral bands to the building
structural roof members.
[0088] In the invention, these lateral bands which are the closest
ones of the lateral bands to the opposing sides of the rafters are
referred to as safety bands 28S, in part because the safety bands
are the bands which are the most likely ones of the lateral bands
to receive the stress of having a worker fall onto the suspension
fabric used in the fall protection system. Further, the inventors
have discovered that the safety bands, when stressed by a fall,
absorb more of the force than when any other lateral band is
stressed by a fall. The inventors contemplate that the force of a
fall/drop test away from the rafters can be dispersed among at
least four bands which surround the drop location: whereas by
contrast, when such force is imposed close to the rafter, only 3
bands are disposed around the drop site, whereby those 3 ban in
that instance, do the work done by 4 bands at locations further
away from the rafter.
[0089] The safety bands 28S are graphically delineated in FIG. 8 by
dashed extensions of such bands on the right side of the
drawing.
[0090] FIG. 5 shows the attachment of a lateral band to an eave 20.
FIGS. 7-14 show an inventive approach to supporting the lateral
bands, and thus the band grid system, from intermediate purlins
24.
[0091] FIGS. 7 and 8 illustrate a safety dip 52 for use in
supporting ones of the lateral bands from ones of the intermediate
purlins. As illustrated in FIGS. 7 and 8, safety clip 52 has an
upper leg 54, a lower leg 56, and a bight 58 joining the upper and
lower legs. Apertures 60 in upper and lower legs 54, 56: are
aligned with each other, thus providing a passage which can receive
a screw for fastening the safety clip to the lower flange of an
overlying purlin.
[0092] FIG. 9 shows an end view of a safety clip 52 fastened to the
bottom surface of a bottom flange 48 of one of the intermediate
purlins 24. FIG. 11 shows the safety clip so fastened to the bottom
surface of the bottom flange of the purlin from an end view/profile
view, of the purlin. Still referring to FIGS. 9 and 11, a Tek screw
66 extends through the apertures 60 in the safety clip and thence
into the bottom flange of the purlin, making the secure attachment
to the purlin. As seen in FIG. 9, when the screw attaches the
safety clip to the purlin, the force applied in tightening the
screw doses the space between the ends of the upper and lower legs
54, 56, thus creating a flange 67 adjacent openings 60, as well as
defining a closed loop 62, surrounding an opening 64 which extends
through the safety clip.
[0093] The safety clip is oriented relative to the ridge and eave
such that opposing ends of opening 64 are disposed, respectively,
toward the corresponding ridge 22 and eave 20. Accordingly, the
passage which extends through opening 64 extends in the same
direction as lateral bands 28.
[0094] FIG. 9 shows one of the lateral bands 28 extending through
opening 64. As illustrated in FIG. 9, safety clip 52 supports the
lateral band in close proximity to the bottom of the respective
purlin. The walls of loop 62, which define the opening and thus
surround band 28, limit the lateral movement of band 28 relative to
loop 62, such that the walls of the loop keep that portion of the
band, which is facing the walls, confined to the space defined by
the loop. Thus, the band cannot move laterally outside the confines
of the walls of the loop.
[0095] However, safety clip 52 places no limitations on the ability
of the lateral band 28 to move longitudinally with respect to the
safety clip. Thus, other than incidental friction between the walls
of the loop, such as at the bottom of the lateral band and the top
of the lower leg of the safety clip, longitudinal movement of the
lateral band relative to the safety clip is generally
unhindered.
[0096] FIG. 10 illustrates an alternate embodiment of the safety
clip, enumerated as 52A. Safety clip 52A is made of the same
material as safety clip 52, typically the same steel banding that
is used for the lateral bands. But rather than folding the clip
material on itself as in the embodiments of FIGS. 7-9, in the
embodiment illustrated in FIG. 10, the material of safety clip 52A
is formed in the shape of a flanged shallow "U". Thus, safety clip
52A, as installed, has a centrally-recessed element flanked on both
sides by flanges extending from the upper ends of the recessed
element. Each flange has an aperture 60, receiving a Tek screw 66
through an intervening washer 68, the screw extending through the
washer, through the flange, through the fabric, and into and
through the lower flange of the intermediate purlin. With the
safety clip 52A thus anchored at flanges 67 on both ends of the
safety clip, opening 64, and the corresponding passage, is defined
in part by the safety clip and in part by the lower flange of the
purlin.
[0097] Safety clip 52A operates very similar to safety clip 52 in
that the installation of safety clip 52A limits lateral movement of
band 28 while providing generally unrestricted longitudinal
movement of the lateral band relative to the safety clip.
[0098] So, rather than building a fall protection system to
transfer the impact force on the lateral band to the closest
purlins by screwing the lateral band to the bottom flange of each
purlin as in the prior art, the invention uses a longer length of
banding, defined through the loop of at least one safety clip, on
at least some of the lateral bands, to absorb some of the
laterally-expressed energy of the impact force as well as, in some
bands, to transfer a substantial portion of the laterally-expressed
impact force to the ridge and eave of the roof, and/or to one or
more of the intermediate purlins which are displaced from the point
of impact by at least one purlin.
[0099] FIG. 12 illustrates a typical embodiment of the fall
protection systems of the invention wherein a safety band 28S is
next adjacent a rafter 16. In that embodiment, the safety band
extends from ridge to eave and is secured by Tek screws 66 to the
ridge and the eave. Between the ridge and the eave, the safety band
passes through a safety clip 52 at each intermediate purlin between
the ridge and the eave.
[0100] Thus, the safety band is secured against longitudinal
movement of the band only at the ridge and at the eave. Between the
ridge and the eave, the safety band is free to move longitudinally
through each of the safety clips, while being restricted against
lateral movement beyond the boundaries of loops 62 at the
respective purlins/safety bands.
[0101] FIG. 12 also illustrates that longitudinal bands 26 are
supported by lateral bands 28, in that the lateral bands underlie
the longitudinal bands. Referring again to FIGS. 2 and 3, it is
seen again that the longitudinal bands are secured against
longitudinal movement only at rafters 16.
[0102] A distinctive feature of this invention is that the banding
stock used for at least safety bands 28S is softer and more
yielding than banding stock which is traditionally used for bands
26 and 28, though the physical dimensions of such bands remain
generally the same, at 1 inch width, 0.023 inch thickness. Thus,
banding stock used for safety bands 28S has
[0103] Yield strength, average--45-85 ksi, optionally 45-75 ksi,
optionally 50-65 ksi, optionally 55-60 ksi
[0104] Tensile strength, average--60-90 ksi, optionally 5-85 ksi,
optionally 55-79 ksi, optionally 70-75 ksi
[0105] Elongation in 2 inch sample--12%-40%, optionally 22%-37%
[0106] Hardness, Rockwell B Scale--50-80, optionally 60-79.
optionally 70-75.
[0107] "Ksi" means "thousands of pounds per square inch".
[0108] Yield, tensile and elongation properties are determined
using an Instron Tensile Tester according to ASTM A370-12a.
Briefly, a two-inches-long section of a dog-bone shaped sample is
placed in the jaws of the test machine, and stretched by the
machine until the sample breaks. Yield and ultimate tensile are
recorded by the testing machine. Elongation is measured manually
according to the test procedure after the sample breaks.
[0109] Banding material illustrated for use as the safety bands in
this invention is available as a hot-dip zinc/aluminum alloy-coated
Grade 50 structural steel, from Steelscape, A BlueScope Steel
Company, Kalama, Wash. as ZINCALUME.RTM. Steel Grade 50 (Class
1).
[0110] Choosing to not be bound by theory, the inventors herein
contemplate that the softer steel banding absorbs more of the
force, and especially the shock effect of the impact, than the
harder Grade 80 steel, while being strong enough to provide the
needed support of fabric 32 and to transfer a remainder portion of
the force of a dropping object to structural roof members of the
building. Thus, while the prior art attempts to use the strength of
the steel to transfer a portion of the force of the impact of the
falling load to the roof structural members, in the invention, and
at that lateral band which receives the greatest stress when
participating in catching a falling load, which is that band
next-adjacent the rafter, the invention relies, in first part, on
the elongation properties of the softer banding used for the
"safety" bands to absorb more of the force of the impact. The
invention further relies, in second part, on use of the safety
clips to expose a longer length of the safety band to the impact
force, and to transfer the impact force to a greater number of
elements of the roof structural members, whereby a greater fraction
of the impact force is transferred away from the point of impact so
that a lesser fraction of the impact force remains to be dissipated
in the suspension fabric at and adjacent the point of impact.
[0111] In light of the benefits provided by using the softer
banding material for the lateral bands 28, the invention provides
novel dissipation of the force of impact. Accordingly, the novelty
of the invention can be extended such that, the remaining bands,
including the remaining lateral bands 28 and the longitudinal bands
26, use the same softer steel banding.
[0112] Thus, in a first set of embodiments of the invention, the
softer steel banding material is used in only the lateral band
closest to the rafters while a relatively harder e.g. the full
hard, banding material is used in the remaining lateral bands and
in the longitudinal bands. This first option focuses attention on
that lateral band which has the greatest likelihood of having to
absorb and transfer all, or almost all: of the force which gets
transferred to the purlins adjacent the impact site.
[0113] In a second set of embodiments of the invention, the softer
steel banding material is used in all of the lateral bands while a
relatively harder, e.g. full hard, banding material is used in all
of the longitudinal bands. This second option focuses attention on
the relatively shorter length distance between attachments of the
lateral bands to the purlins, whereby relatively shorter lengths of
lateral band, compared to relatively longer lengths of longitudinal
banding, are tasked with absorbing and transferring impact forces
to their next adjacent roof structural elements. Namely, the
lateral banding transfers impact force to the next adjacent
purlins, which are e.g. 5 feet apart. Thus, the lengths of the
lateral bands which transfer impact force to roof structural
members are typically about 5 feet.
[0114] By contrast, the longitudinal bands are anchored to the roof
structure only at the rafters, which are commonly 25 feet apart.
Thus, the lengths of the longitudinal bands which transfer the
impact force to roof structural members are typically about 25
feet, about 5 times longer than the transfer portions of the
lateral bands.
[0115] In a third set of embodiments of the invention, the
relatively softer' Grade 50 banding material is used in all of the
longitudinal bands and all of the lateral bands. This third set of
embodiments takes full advantage of the relatively greater
elongation properties of the Grade 50 banding, to permanently
elongate, while effectively passing, to the roof structural
members, enough of the remainder portion of the impact force of the
falling object that suspension fabric 32 is able to dissipate the
remainder of the impact force without catastrophic failure of the
fabric.
[0116] Banding used in the invention is distinguished from steel
bar stock in that steel bar stock is stiff and rigid. By contrast,
the banding used in the invention is thin and flexible such that
the banding is typically shipped to the user in rolls. When the
banding stock is cut to the e.g. specified 1-inch width, and the
resulting bands are loosely draped over rafters spaced e.g. 25 feet
apart, mid-sections of the bands readily drape downwardly by
multiple feet from the elevations of the rafters. Further, such
banding is completely incapable of supporting itself or the
overlying suspension fabric until substantial tensile force, which
can be manually applied using hand tools, is applied to the
banding.
[0117] Certain fabrics are known in the art for use as suspension
fabrics in roof insulation systems, and such fabrics may be
acceptable in the fall protection systems of the invention,
provided that the bands used in the band grid-work of the invention
are sufficiently dose together. An exemplary fabric, which the
inventors have tested and found satisfactory for use with the band
grid-work disclosed herein is available as Type 1070 Vapor Retarder
fabric from Intertape Polymer Group, Bradenton, Fla. The Type 1070
fabric is a woven HDPE scrim having the following characteristics
as specified by the fabric supplier:
[0118] Nominal thickness--9 mils (0.23 mm)
[0119] Nominal weight--4.3 oz/yd' (149 g/m.sup.2)
[0120] Grab Tensile--Warp 136 lb (605 N)/Weft 126 lb (559 N)
[0121] Strip Tensile--Warp 100 lb/in (877)/Weft 90 lb/in (799)
[0122] Tongue Tear--Warp 50 lb (222 N)/Weft 45 lb (200 N)
[0123] Mullen Burst--245 psi (1690 kPa)
[0124] Moisture vapor transmission--0.02 perms.
[0125] A typical bay 18 is about 25 feet wide, between pairs of
next-adjacent rafters. Within a given bay, lateral bands 28 extend
parallel to each other, parallel to the respective rafters which
define the bay, and are generally spaced apart by about 36 inches
to 40 inches, but no more than 48 inches. Thus, a desired spacing
between lateral bands 28 is 36-40 inches; but up to 48 inches is
accepted where the increase from 40 inches e.g. up to 48 inches can
reduce the number of bands.
[0126] A leading edge of fabric 32 can be placed inside the eave. A
leading edge of the fabric enters the eave above bottom flange 36,
passes across the top of the bottom flange to web 38, passes along
the inside surface of web 38 and up to upper flange 34 and thence
toward the ridge to the eave opening which faces the ridge. By
traversing such path inside the cavity defined inside the eave, the
fabric can substantially encase the edge of any insulation which is
to be installed on top of the fabric in the space between the eave
and the next-adjacent purlin.
[0127] In the alternative, the edge of the fabric, at the save, can
be trapped between the lateral banding and the lower surface of the
bottom flange of the eave as suggested in FIGS. 3 and 5.
[0128] When a falling/dropping impact force arrives on the
suspension fabric, the force received by the suspension fabric has
a first directional force component and a second
velocity/shock/suddenness component. The force component of the
impact is resisted by, absorbed by, the deflection characteristics
of the materials in the fall protection system. The
velocity/shock/suddenness component of the impact addresses the
rate at which the respective materials can deflect as the force of
the impact is applied to the respective building elements.
[0129] Where a safety band 28S, mounted to a purlin by a safety
clip 52, is one of the closest lateral bands to the point of
impact, a first portion of that force is transferred, as first
tensile forces, into the full length of the longitudinally-mobile
portion of the respective safety band and is absorbed by tensile
elongation of the safety band.
[0130] A second portion of that received force is transferred, by
the safety band through the safety clips closest to the location of
the impact, and thence to the purlins which are closest to the
location of the impact.
[0131] A third portion of that received force is transferred, by
the safety band, to the purlins, the ridge, or the eave which are
next adjacent the purlins which are closest to the location of the
impact, such that greater than two, typically at least four,
longitudinally-extending structural members of the roof participate
in dissipating substantial portions of the impact of the
fall/drop.
[0132] A fourth portion of that force is transferred to respective
closest ones of the longitudinal bands, which transfer their
received tensile forces to the respective next adjacent
rafters.
[0133] A fifth remainder portion of that force is distributed about
the respective affected area of the suspension fabric. While
choosing to not be bound by theory, the inventors herein
contemplate that the fabric absorbs both a portion of the
directional component of the force of the impact and a
velocity/shock/suddenness component of the force of the impact.
[0134] Turning again to the responses of the bands, the tensile
forces so imposed on the longitudinal bands and the respective
lateral band or bands are distributed along the full lengths of the
respective longitudinal bands and along that portion of the
respective lateral hand or bands which is/are between the two
purlins which are next adjacent the location on the fall protection
system where the impact of the drop is received. Thus, the
elongation properties of both the longitudinal bands and the
lateral bands are utilized in transferring portions of the impact
force to the roof structural elements, namely one or more
intermediate purlins, and optionally to ridges or eaves, and to the
rafters.
[0135] The benefit of using the full lengths of the safety bands to
absorb the impact force of the fall/drop is that more of the force
is dissipated by band elongation rather than that force being
retained in the fabric or transferred to the next adjacent purlins.
In addition, a portion of the force can be transferred, by the
safety band, to additional ones of the purlins, and additional
portions of the force can be transferred to the eave and to the
ridge. Thus, the use of the safety clips to accommodate
longitudinal mobility of the safety band results in dissipating
more of the force of the impact in an increase number of elements
of the roof structure. By increasing the number of elements of the
roof structure which participate in dissipating the force of the
impact, the amount of the force which must be dissipated by the
fabric and by the bands is reduced. Such reduction in the amount of
the force which must be dissipated by the bands and the fabric
provides increased opportunity for the fabric to survive the force
of the impact without catastrophic failure of the fabric which is
by definition, a failure of the fall protection system.
[0136] FIG. 12 further shows, in its typical configuration of the
fall protection system of the invention, that lateral bands 28
which are not safety bands, namely which are not a lateral band
next adjacent a rafter, can, and commonly are, attached to each
purlin in a conventional manner, namely by screwing a Tek screw 66,
with accompanying washer, through a hole in the lateral band,
thence through the suspension fabric, and thence through the lower
flange of the respective purlin, The suspension fabric is thus
trapped between the lower flange of the purlin and the respective
washer/screw combination, which tightly clamps the suspension
fabric to the lower surface of the lower flange of the purlin.
[0137] FIG. 13 shows another embodiment of the fall protection
system of the invention wherein the safety band is secured to the
intermediate purlins using the safety clip at less than all of the
purlins. FIG. 14 illustrates that some of the lateral bands which
are not safety bands can be mounted to the bottom flange of a
purlin using the safety clip. Thus, the designer of a given system
has the flexibility to specify the safety clips for some but not
all of the intersections of any one of the lateral bands. But there
is both a materials cost and a labor cost attendant to use of the
safety clip whereby the system designer assesses trade-offs between
band strength and cost, fabric strength and cost, and the all-in,
namely materials plus labor, cost of installing respective ones of
the safety clips. The typical system, however, is shown in FIG. 12
where the safety bands pass through safety clips at each
intermediate purlin and the remaining lateral bands are screwed
directly to the purlins, through the fabric, at each intermediate
purlin.
[0138] Thus, referring to the combination of FIGS. 5, 5A, and 6-14,
a full implementation of the invention contemplates suspending some
or all of the safety bands 28S from the purlins using safety clips
52 as illustrated in FIGS. 9-14.
[0139] Thus, in a given embodiment, the safety bands are suspended
from most, if not all, of the intermediate purlins by safety clips,
and the remaining lateral bands (non-safety bands) are fastened to
the intermediate purlins, either directly through the suspension
fabric through a washer, or fastened to some or all of the
intermediate purlins using safety clips. The remaining lateral
bands (non-safety bands) may be fastened to each of the
intermediate purlins directly through the fabric to the lower
flange of the purlin using a screw.
Method
[0140] Installation of a fall protection system of the invention
begins after the columns, rafters, ridges, eaves, and intermediate
purlins are in place about at least a given bay. Typically,
installation of the fall protection system begins after erection
emplacement of all of the columns, rafters, ridges, eaves, and
purlins.
[0141] Installation of the fall protection system begins by
installing longitudinal bands 26. A given longitudinal band is
installed by unwinding band material from a roll and extending the
band material over the tops of the respective rafters and across a
given bay or bays. At least one longitudinal band is extended,
between each next-adjacent pair of purlins to at least the next
rafter, and is cut to length. The longitudinal bands are manually
stretched tight with hand tools, and the so-tightened bands are
fastened to the respective rafters with Tek screws. As illustrated
in the drawings, the longitudinal bands typically extend
perpendicular to the rafters. The so-partially-installed,
tightened, longitudinal bands extend from rafter to rafter at
generally the height of the tops of the rafters, but some nominal
amount of sag of the longitudinal bands exists between the rafters
at this stage of installation.
[0142] Typically, the purlins are spaced no more than 5 feet apart.
In this invention, typically a single band is installed between
each pair of next-adjacent purlins so long as the purlin spacing is
no more than the typical maximum of 5 feet. Where the purlin
spacing approaches, or exceeds, the typical 5-feet maximum, an
additional longitudinal band 26 may be used in one or more of the
spaces between the purlins
[0143] Once the longitudinal bands 26 have been emplaced and
tightened, banding for lateral bands 28 is unrolled under the
longitudinal bands, and one end of the banding is secured to the
respective ridge or purlin, or to an opposing eave. The lateral
banding material is extended to the eave of the respective bay and
then tightened sufficiently to raise both the lateral banding and
the overlying longitudinal bands into close proximity with the
intermediate purlins. This process is repeated along the width of
the bay, e.g. between the rafters, until the desired number of
lateral bands has been emplaced across the width of the bay.
[0144] With the band grid system thus temporarily in place, a
zigzag-folded roll of the suspension fabric is elevated to the
height of the rafters, typically adjacent a rafter at an end of the
building or bay. The fabric is then unrolled on top of the band
grid in one of the spaces between next-adjacent ones of the purlins
such that one end of the fabric faces the eave and the opposing end
of the fabric faces the ridge. The ends of the fabric are then
pulled, individually, toward the eave and the ridge, working the
leading ends of the fabric under the intervening intermediate
purlins and above the band grid. The initial phase of the process
of so-extending the fabric is illustrated in FIG. 3.
[0145] With the fabric having been generally extended the full
length and width of the bay over which the fabric is to be
suspended, namely over the band grid and under the intermediate
purlins, the lateral bands are then attached to the intermediate
purlins, beginning at the ridge and working toward the eave. The
method of such attachment at each intersection of band and purlin
is determined by the fall protection system which has been designed
for, specified for, that particular building, in a typical design;
the safety bands 28S are attached to each purlin using safety clips
52.
[0146] For example, a safety clip such as that shown in FIGS. 7 and
8 is slipped transversely across the safety band such that an edge
of the safety band is located proximate bight 58. The safety clip,
with resident safety band proximate bight 58, is positioned against
the lower surface of the suspension fabric with apertures 60
aligned with the lower flange of the corresponding intermediate
purlin. A self-drilling Tek screw 66 is then driven through
apertures 60, through fabric 32, and into the lower flange of the
purlin. As the screw is driven tight against the bottom surface of
the fabric, driving the fabric against the bottom surface of the
lower flange of the purlin, the space between legs 54 and 56, of
clip 52, closes, thus defining the two-layer flange 67 illustrated
in e.g. FIGS. 9 and 11. Screws 66 are driven through the remaining
lateral bands 28 at each purlin, fastening the lateral bands
directly to the purlins as illustrated in FIG. 13.
[0147] Once the attachments to the intermediate purlins have been
completed, the temporary attachments of the bands to the eave are
released, and screws 66 are installed through the lateral bands at
the eave.
[0148] Sides of the fabric are then cut around the purlins at each
rafter, as known in the art, and edges of the fabric are secured to
the top surfaces of the rafters such as by adhesive, also as known
in the art.
[0149] With both the longitudinal and lateral bands so secured to
the roof structure; with the fabric so secured to the ridge and
eave by the lateral bands and secured to the rafters by e.g.
adhesive, installation of the fall protection system of the
invention is thus complete and ready to protect workers who
subsequently install other elements of the building while working
at the roof elevation; such elements as the roof insulation and the
roof panels.
[0150] Suspension fabric 32; which in the preferred embodiment
consists of a vapor barrier material, is trimmed to size before
installation. The suspension fabric is installed one bay 18 at a
time and, in the case of large buildings or buildings with high
gables, fabric 32 for each half of the bay may be divided at ridge
22 and may be installed separately.
[0151] The suspension fabric has been cut, prior to installation,
to a size having a dimension a few inches longer than the
dimensions of the bay to be overlaid, and is Z-folded for easy
spreading above the band grid. For this purpose a zigzag type fold,
as shown in FIG. 3, is easiest to work with, although other rolling
or folding arrangements can also be used and are within the scope
of the invention.
[0152] The fall protection systems of the invention are designed to
be of sufficient strength to catch and support a man's weight,
generally between 250 and 400 pounds. The system is tested by
dropping a 400 lb, weight with the center of gravity of the weight,
before the weight is dropped, being 42 inches above a worker's
walking height, thus 42 inches plus the height of the purlins,
namely about 50.5 inches above the fabric. To pass the test, the
system must stop the falling weight at any point in the bay which
is so protected. In one test specified by OSHA, 400 lb. of washed
gravel or sand is placed into a reinforced bag that can tolerate
being dropped repeatedly. The test bag is 30 inches in diameter.
The 400 pound bag is hoisted above the fall protection system to a
height of 42 inches above the plane of the intermediate purlins,
measuring from the center of the so-filled bag. A cord supporting
the weight of the bag is then released, allowing the weight to free
fall in one concentrated load. The weight can be dropped onto any
part of the fall protection system to test different areas.
[0153] Although the invention has been described with respect to
various embodiments, it should be realized this invention is also
capable of a wide variety of further and other embodiments within
the spirit and scope of the appended claims.
[0154] Those skilled in the art will now see that certain
modifications can be made to the apparatus and methods herein
disclosed with respect to the illustrated embodiments, without
departing from the spirit of the instant invention. And while the
invention has been described above with respect to the preferred
embodiments, it will be understood that the invention is adapted to
numerous rearrangements, modifications, and alterations, and all
such arrangements, modifications, and alterations are intended to
be within the scope of the appended claims.
[0155] To the extent the following claims use means plus function
language, it is not meant to include there, or in the instant
specification, anything not structurally equivalent to what is
shown in the embodiments disclosed in the specification.
* * * * *