Fire insulation edge reinforcements for structural members

Abstract

Fire insulation reinforcements protect structural members from exceedingly high temperatures during fires. The reinforcements are supported on the flange sections of structural members as well as flat surfaces to effectively hold the fireproofing coating in place during fires so as to better insulate the flat surfaces and outer edges from damage during fires.

Parent Case Text

This application is a continuation-in-part of our copending U.S. patent application Ser. No. 454,077, filed Mar. 25, 1974, now abandoned.

Description

BACKGROUND OF THE INVENTION

This invention relates generally to fire protective coatings and more particularly to a wire mesh and fireproof coating to provide a fire insulation reinforcement for structural members.

Structural members, such as steel beams, walls, containers and the like, are often fireproofed with coatings to protect against the heat produced in an unplanned fire. Without this protection, the member would soon reach temperature levels where the accompanying loss in strength will result in the structural member failing under load. Most construction structural members have flange edges such as "I" beams, "H" beams, channels and angles. These edges are the most difficult parts of the member to protect against heating because the flow of heat from the fire comes in three directions (top, bottom, and perpendicular to the edge) instead of the two directions possible on flat planar surfaces. The flow of heat is represented in FIG. 1 by the arrows.

Some thin coatings presently used for fire protection are intumescent in nature. These coatings swell into a carbonaceous foam when heated which insulates against the fire. However, during fires these materials may lose their bonding properties and sections of the material may fall from the member thereby exposing the bare member to the fire. This type of coating poses even greater problems in providing protection to the edge member because the intumescence takes place in only one direction, i.e., perpendicular to the coated surface and thus large cracks or fissures are likely to occur in the foamed material at the edges of the steel flanges. No lateral intumescence really occurs and when the foam intumesces outward, the surface area does not change, forcing fissures to occur at the surface.

The primary method used for steel member edge protection has traditionally been to cover the edges with sufficient coating material to overcome the problem. Often during fire tests (ASTM E-119) of such protection systems, the temperature level recorded in the edges of the test specimen was the highest, and hence controlled the length of the test.

It is very difficult to apply extra fireproofing material to the edges of structural members whether the material is cast into place (concrete) or sprayed in place (cementitious mixtures, fibers, or intumescent mastics). The reason is because of the inconvenience of the shapes involved (casting) and the difficulty of building up a localized thin strip (spraying) along the edge. Rather, the practice has been to uniformly apply more material to the entire perimeter of the structural shape to insure that the edges are protected. A disadvantage of this method is that it causes more material to be used than necessary, increases weight, and increases costs (both material and spray time).

Accordingly, it is an object of this invention to provide fire insulation reinforcements which will provide reliable thermal protection to structural members, be easy to apply, and thoroughly reinforce the entire fireproofing coating both in the virgin state and during a fire when the intumesced char layer forms.

A further object of this invention is to provide an insulated edge reinforcement which gives better thermal performance of fireproofed structural members in a fire.

A still further object of this invention is to provide insulated reinforcements which permit reduced overall coating thickness and waste through eliminating overspray from trying to build up fireproofing coating thicknesses on the edges of the flanges.

And yet another object of this invention is to provide an insulated reinforcement which increases reliability and safety through the reinforcement of the fireproofing coating thereby preventing early bonding failures of the fireproofing material in a fire.

SUMMARY OF THE INVENTION

This invention provides an insulated reinforcement for use on structural members. The reinforcement is supported on the structural member and the fireproofing material placed thereabout so as to protect and insulate the surface and respective edges of the members from damage due to heat during unplanned fires. The reinforcement secures an insulation strip against the end of the structural flange. Fireproofing material is applied over the mesh and insulation strip in a thickness sufficient to protect the flanges and webs of the structural member.

Other objects, details, uses and advantages of this invention will become apparent as the following description of the exemplary embodiments thereof presented in the accompanying drawings proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings show present exemplary embodiments of this invention in which:

FIG. 1 is a fragmentary perspective view of a structural I-beam showing the direction of beam heat;

FIG. 2 is a fragmentary perspective view of one embodiment of the insulated edge reinforcement of this invention;

FIG. 3 is a view similar to FIG. 2 showing a precast edge reinforcement;

FIG. 4 is a fragmentary end view showing means for securing an open leg insulated edge reinforcement to a structural member;

FIG. 5 is a chart showing the comparison of edge temperatures versus flange center and web temperatures resulting from the use of this invention;

FIGS. 6-9 show other exemplary embodiments of this invention particularly showing alternate shape configurations;

FIG. 10 is a fragmentary perspective of a flat surface, such as a wall, having the fire insulation reinforcement of this invention secured thereto; and

FIG. 11 is a sectional view taken along line 11--11 of FIG. 10.

DESCRIPTION OF ILLUSTRATED EMBODIMENTS

Reference is now made to FIG. 1 of the drawings which illustrates a typical structural member 10, such as a structural steel I-beam. It is seen that the I-beam 10 includes a plurality of flange sections 12 having end edges 14 and 16. As previously indicated, the direction of the flow of heat from a fire is indicated by the arrows. It can be seen that the web 11 and flange 12 each have two-directional heating, i.e., perpendicular to the structural surfaces. The end or edge of the flange 12 is seen to have three-dimensional heating, the third direction being perpendicular to the edge of the flange.

The insulated edge reinforcement system 20 is shown in two basic forms in FIGS. 2 and 3. The FIG. 3 form has a precast edge of coating material or a steel edge and the FIG. 2 form does not. Both forms perform the same functions, however.

Referring now to FIG. 2, the edge reinforcement 20 is constructed of a meshlike member such as wire mesh 18. The wire mesh 18 is formed in a press brake or similar machine to the shape required for the member to be protected. Welded wire mesh is preferred and may either be with or without galvanizing. The mesh size may be any suitable opening from one-fourth inch to 1 inch or greater. The wire diameter should be small enough to reduce cost and permit easy forming, but large enough to hold the formed shape firmly. One edge reinforcement having excellent fireproofing capabilities was constructed of one-half inch mesh and 19 gauge wire.

Sheet insulation 22 is sliced or cut into strips and laid into the formed wire mesh 18. Any suitable fibrous insulation such as U.S. Gypsum Thermafiber may be used. It is noted that board insulations will also work. A practical limit on the thermal conductivity for the insulation used is approximately 0.2 Btu/ft-hr-.degree.F. The size of the insulation strip 22 is preferably at least twice the flange 12 thickness in depth and preferably at least equal to the flange thickness in thickness.

In the precast form of FIG. 3, the formed wire 18A with the insulation 22A in place is placed edge first into a mold (not shown) containing the casting material. The edge reinforcement 20A is left in the mold until hardening of the edge material 24 occurs. The reinforcement with the precast edge 24 is then stripped from the mold and is ready for shipping and installation. For some cases, a metal edge 24 may be stapled or welded on the reinforcement 20A in place of the precast edge.

The reinforcements 20 may be made with either open legs or closed legs during the forming operation. The legs are considered as that part of the wire mesh which extends inwardly from the flange edge to the web. If a closed leg form is used, the insulated reinforcement 20 is merely slipped over the flange by hand after slightly spreading the legs apart. It is held in place on the flange by the spring tension in the wire legs until the fireproofing coating is sprayed over the system. If the open leg form is used, the reinforcement 20 is slipped on the flange and a crimping tool 26 is used to tighten the wire against the flange surface as shown in FIG. 4.

The crimping tool 26 is seen to comprise a pair of forcing members or handles 28 and 30 pivotally connected together at 32. The handle 28 includes an outer peripheral shoulder 34 and a vertically projecting shoulder 36. The peripheral shoulder 34 acts against one leg of the wire mesh 18 and holds the mesh 18 against the flange 12. The shoulder 36 abuts against the precast edge 24 along the exterior side of the insulation strips 22. One end or shoulder 38 of the handle 30 engages the opposite leg of the wire mesh 18. Thus, when the handles 28 and 30 are pressed or forced together, force is applied through the shoulders 34 and 38 to bend the open legs of the wire mesh 18 into a clamping condition relative to the flange 12.

After the insulated reinforcement 20 is in place, any suitable fireproofing material (not shown) is applied over the reinforcement 20 in a thickness which is sufficient to protect the flanges and webs of the structural member 10. These thicknesses are in practice determined by actual fire tests (i.e., ASTM E-119). However, the edges 14-16 of the reinforced flange do not now have to be built up in thickness; they merely have to be covered with enough material to produce a neat continuous coating.

If an unplanned fire should occur, the insulated reinforcement 20 works in the following manner. First of all, the presence of the insulation 22 inside the wire mesh 18 retards the perpendicular flow of heat into the edge of the flange 12, thus keeping it cooler for a longer period of time. The wire mesh 18 itself holds the fireproofing material together all around the edges 14-16 and flange 12 as the material decomposes, intumesces, etc. This is especially important since the steel primers and paints which the coatings are applied over usually lose their bonding strength at temperature levels far below that which the steel itself may be safely allowed to reach, approximately 1000.degree.F. In the presence of bonding strength failure, the fireproofing material has nothing holding it onto the steel except its own structural integrity. The wire reinforcement 18 provides this integrity if needed.

Finally, if an intumescent coating is used, there is a very high possibility of fissures and cracks forming at the edges of the flanges and uncovering bare steel. Should this happen, up to a 30 percent increase in heat flux into the flange may occur if only 1 percent of the steel surface is exposed. However, with the reinforcement member 20, instead of these fissures uncovering bare steel in this area, only the insulation 22 will be exposed and the heat transfer to the edge of the steel flange will be many times less than if the steel itself were exposed. Naturally, this permits much better fire performance of the overall coating system. Another advantage of the mesh 18 is that if fissures form on the flange surfaces, they will stop when the wire mesh 18 is reached. The material under the mesh swells beneath it and provides some protection to the steel directly below the fissure.

FIG. 5 represents a comparison of the edge temperature versus the flange center and web temperatures using the edge reinforcement of this invention. In this test, a 10WF49 beam was reinforced as hereinabove described and coated with an intumescent fire protective coating developed at Avco Systems Division, in Lowell, Mass., and marketed under the name AVCO FM 59. The test was run in an environment in which the furnace temperature was 1950.degree.F., the radiant heat flux was 16.2 Btu/ft.sup.2 -sec. and the convective heat flux was 1-2 Btu/ft.sup.2 -sec. Temperatures were measured in the web, flange web joint and at the edges of the top and bottom flanges and are respectively designated on the chart by triangle, square, circle and hexagon. The effectiveness of the edge reinforcement protection is demonstrated by the overall fire performance of the beam and by the fact that the beam remained fairly uniform in temperature distribution throughout the test. The edges, therefore, were successfully afforded the same protection as the rest of the beam.

Referring now to FIGS. 6-9, it is seen that the edge reinforcement member of this invention may be formed in varying shapes depending on the desired end use. Different wire meshes may be employed, as well as different types of insulation. The insulation can be placed on the edge of the flange by any suitable means such as contact cement and the wire slipped over the insulation later. If a precast or metal edge is used, the type of material can be varies as long as it bonds well to the fireproofing material which is applied over it. The actual shape of the wire mesh will depend on the end use.

As particularly seen in FIG. 6, the wire mesh 18B is seen to be formed in a T-shape over the end of the insulation 22. FIG. 7 shows the T-shape wire mesh 18B being utilized with a precast edge or metal edge 24B. The edge 24B conforms to the T end of the wire mesh 18B and is held thereby.

FIG. 8 represents another embodiment in which the wire mesh 18C is formed with an enlarged or bulb portion 40. The purpose of the bulb is to permit firm anchoring of a maximum amount of fireproofing material under the mesh near the flange edge.

The embodiment of FIG. 9 is very similar to the FIG. 2 embodiment. The difference in this instance is that the wire mesh 18D is formed with surface standoff dimples 42. Thus, when the mesh 18D is placed over the flange, the dimples 42 will engage the flange with the majority of the wire mesh 18 being supported away from the surface of the flange. This permits better anchoring of the fireproofing material under the mesh.

The fire insulation reinforcement of this invention is also applicable for use on large flat surfaces such as walls, large cylindrical containers and the like. Referring now to FIGS. 10 and 11, a fragmentary view of a wall 44 is seen to be fire protected by a fire insulation reinforcement designated generally as 46. The fire insulation reinforcement 46 is formed in the same manner as previously described. In the case where large walls or the like are to be protected, the wire mesh 48 is mechanically attached to the wall by any suitable means. As an example, if the wall 44 is of steel plate, the wire mesh 48 may be secured thereto by spot welds 50. If the member will not support a weld, suitable means, such as support pins or the like, may be utilized to support the wire mesh in place. The fireproof coating 52 is then applied over the wire mesh 48 such that the wire mesh is in effect encased in the fireproof material 52. Hence, if a fire should occur the material 52 will intumesce. When the material intumesces, the fireproofing material very often will lose the bonding capabilities it has with the structural member. In addition, fissures may occur in the material. If the wire mesh 48 was not used, sections of the fire protective material might fall off thereby exposing the structural member. However, the wire mesh 48 holds the fireproofing material 52 in place even though the material has lost its bonding effect. Similarly, if a fissure should develop, the fissure would be stopped in the wire mesh level and would not extend to the structural member.

It is seen that the fireproof reinforcements of this invention overcome the disadvantages of prior methods of fireproofing structural members. The fireproof reinforcement of this invention is simple in structure, easily applied to the flange portions and provides effective fireproofing when used with the fireproofing material, such as intumescent coatings and the like. Accordingly, it is seen that the objectives hereinbefore set forth have been accomplished.

While present exemplary embodiments of this invention have been illustrated and described, it will be recognized that this invention may be otherwise variously embodied and practiced by those skilled in the art.

Claims

What is claimed is:

1. In combination with a structural member having flange portions terminating in an edge susceptible of receiving heat from three directions, a fire insulation structure comprising:

insulation means secured in an abutting relationship to said edge, the insulation means having thickness equal to the thickness of said edge and a depth greater than the thickness of said edge; and

a mesh means around the periphery of said insulation means, said mesh means having leg portions extending beyond the insulation means, said leg portions being engageable with the flange portions of the structural member to secure said insulation means in an abutting relationship with the edge of the flange wherein a fireproof coating is applied over the entire structural member and mesh means thereby substantially reducing the amount of heat flow directed to the end and edges of the flange during fire conditions.

2. The structure set forth in claim 1 in which said mesh means is a wire mesh wherein said wire mesh holds the fireproofing coating together all around the edge and flange as the coating decomposes.

3. The structure as set forth in claim 2 further comprising an edge member secured to the exterior of said wire mesh and insulation means so as to provide an easily fireproofable edge surface for the structural member.

4. The structure defined in claim 2 wherein said structural member includes a flange terminating in said end and edge to which the insulation is secured.

5. The structure as set forth in claim 4 in which the leg portions of said wire mesh frictionally engage opposite surfaces of the portions flange thereby holding said insulation means in place against the flange edge.

6. In a combination with a structural member having an end terminating in an edge susceptible of receiving heat from three directions, and having a fireproof coating over its entire surface, a fire insulation structure comprising:

insulation means interposed between the fireproof coating and said edge in an abutting relationship to said edge, the insulation means having a thickness equal to the thickness of said edge, and a depth greater than the thickness of said edge, wherein said insulation reducing the amount of heat flow directed to said edge.