New Steel Beam is Undersized and Sags Causing a Large Crack in an Exterior Brick Wall GENERAL INFORMATION Date of Site Inspections: May 26, 1998 Location: 2304 Willow Park Drive, Charlotte, NC Prepared for: Mr. and Mrs. Timothy Dancause | Top | Table of Contents | INTRODUCTION Dear Timothy and Patricia: The purpose of this letter is to summarize the things that we have been talking about with respect to the causes of the structural damage and suggested corrective measures. The analysis and repair procedures outlined below are based on information that we have so far gained during visits to the site. In particular, we have not obtained all the information that we would like to have about conditions in the crawl space; for example, the size, location, and quality of existing piers, footings, and girders under the steel and laminated beams. If conditions are significantly different than our assumptions, the repair recommendations described below may not be entirely appropriate. | Top | Table of Contents | DISPLACEMENT DAMAGE AND JACKING PROCEDURES Vertical displacement of one inch or more has occurred in the exterior wall and adjacent interior walls and floors. The displacement has caused a 20 foot long crack to open up in the brick veneer and much cracking to occur around window frames. It has also caused cracks to develop in the interior walls, interior doors to bind, and floors to sag. Our investigation indicates that the some of the displacement can be attributed to deflection of the steel beam and some to careless shoring of the existing structure when the exterior and interior walls were removed. We feel that it is important to have an open mind about why the displacement occurred. It creates an awareness that simply jacking up the center of the steel beam may not be all that is required to bring the floors and walls back into original alignment. We think it is highly likely that it will be necessary to jack and shim the walls and floors at several different points. It may also be necessary to lift building components differently with respect to one another. This procedure would be necessitated if the brick veneer has fallen more than the wood stud wall behind it, or the bathroom floor has dropped more than the adjacent exterior stud wall. As long as the jacking crew proceeds cautiously and intelligently, we think that all structural components can be put back into their original position with little further damage to your home. The estimated jacking force at the center of the steel beam is 20,000 pounds. The estimated jacking force at the kitchen support is 2,500 pounds and at the other support it is 5,000 pounds. The estimated jacking force at each end of the laminated beam is 5,000 pounds. (The jacking force has been increased by 50 percent over the calculated reactions, because it usually takes more force to raise building components than it does to hold them in position.) | Top | Table of Contents | STEEL BEAM, END SUPPORTS AND COLUMN By installing a column under the W 8 x 24 steel beam at the end of the kitchen counter, the steel beam is able to support calculated live and dead loads with a minimum amount of deflection (.075 inches). To keep the beam from twisting under the load, it should be laterally braced as well as possible along its entire length. It is especially important that very strong lateral bracing be achieved at the juncture of the laminated beam and steel beam. According to our calculations, the end reaction at the kitchen end of the steel beam is 1500 pounds. The reaction at the other end of the steel beam is 3700 pounds. The Building Code requires that the ends of the steel beam be supported with four 2 x 4’s or equivalent. According to our calculations, this is more than sufficient support. The beam should extend over the supports by at least three inches to prevent the ends of the wood supports from crushing. It is important that the end supports be solidly blocked from beam to piers. The piers should be 16"" x 16"" and the footings should be 2'-6"" x 2'-6"" x 10"". The bottom of the footings should be installed at least one foot below grade. The beam reaction at the end of the kitchen counter is 12,700 pounds. The beam can be supported with a 6"" x 6"" wood post or a 4"" x 4"" x 3/16"" tube steel column. Both columns can have an unsupported length of 12' and support the load properly. The columns can extend through the floor to piers or they can rest on the subfloor. The advantage of having the columns rest on the subfloor is that it will not be necessary to cut a hole through the floor or cut and resupport the girder underneath. If a steel column is used, the bearing plate at the base of the column should be at least 6"" x 6"" to keep the subfloor from crushing. If the column is installed so that it bears on the subfloor, solid blocking will be required between the subfloor and pier below. The column pier should be 2'-6"" x 2'-6"" and the footing should be 3'-6"" x 3'-6"" x 12"". The footing is based on average soil conditions. Poor soil would require a larger footing. The footing should be installed at least one foot below grade. The wood or steel column should be anchored at the top and bottom with proper connectors to make sure it stays in place. | Top | Table of Contents | LAMINATED BEAM AND SUPPORTS According to our calculations, there is a 3800 pound reaction at each end of the laminated beam. The connection at the steel beam should be made with a Simpson Top Flange Hanger that has a capacity of at least 3800 pounds. The other end of the laminated beam should be supported with three 2 x 4’s. The beam should overlap the support at least 3 inches to prevent crushing. A 16"" x 16"" pier and 2'-6"" x 2'-6"" x 10"" footing should be installed under the end support. The floor joists should be reattached to the laminated beam with Simpson Joist Hangers. As mentioned earlier, the connections at each end of the laminated beam should be constructed so that the beam provides lateral support for the steel beam. | Top | Table of Contents | MISCELLANEOUS The laminated beam and several joists were severely coped out at the end supports. This has reduced the shear strength of the members below minimum requirements. The Simpson hangers should take care of this problem. A couple of the floor joists were also severely notched to accommodate mechanical and electrical equipment. These joists should be replaced or sistered with new joists. It should be possible to level the new floor by replacing the existing shims between the piers and girder with thinner shims. Once this is done, you should anticipate that it will take a while for the floor to settle into position. The steel column is a type of column that can be exposed. You may find, however, that it has a cold appearance and you will want to enclose it. Tubular steel columns come in a variety of sizes. The size that I specified is the minimum size needed. It may be that a larger size column is more aesthetically pleasing to the eye. | Top | Table of Contents | CONCLUSION When Jones Construction has decided how they plan to do the work and before they start, you may want to have us review their plans and procedures with them. This should not involve a lot of our time and will help ensure that they have not overlooked something important. Enclosed is a bill for the time we have expended on the project to date. Please do not hesitate to call us if we can be of further assistance. | Top | Table of Contents | William A. Stanton, P.E. | Top | Table of Contents | | Structural Inspections | Residential & Commercial Services |