CEMCO On-Line CSI Specifications Available Here:09 22 1605 42 00
General Steel Framing:
What are the bracing requirements for Non-load bearing framing?
Non-load bearing framing is braced by the normal attachment of wall facing materials to both stud flanges. However, the use of wall facing materials for bracing should be given consideration during construction. When bracing is required sheathing is applied to the exterior stud flange and the inside flange is left unbraced until the interior is finished. Prior to the installation of interior board, lateral loads can cause stud damage due to lack of interior bracing.Bracing in the form of steel strapping and solid blocking, installed horizontally on the interior flanges at a maximum of four (4) feet on center, in conjunction with the sheathing will brace and restrain the stud framing during construction. If mechanical bracing is required it can be either solid blocking with steel strapping running horizontally on both sides of the studs and attached to each flange or cold rolled channel run horizontally through the stud punch outs and attached to each stud web with clip angles. The maximum spacing for mechanical bracing of non-load bearing framing is four (4) feet on center.
What are the bracing requirements for Load Bearing (combined axial and transverse) studs?Load bearing wall framing with combined loading is subject to vertical loads during construction and prior to being fully braced by the wall facing materials. To insure the framing is adequately braced during construction, mechanical bracing is required to be installed concurrently with the framing. Mechanical bracing can be either solid blocking with steel strapping, run cold rolled channel horizontally through the stud punch-outs and attached to each stud web. The maximum spacing for mechanical bracing of steel framing with combined loading is four (4) feet on center.
What are the bracing requirements for floor joist?The top flange of floor joist shall be laterally braced by the application of floor fastened to the joist. The diaphragm effect of the floor must be judge to be structurally adequate for the lateral bracing of the top flange. In addition, joist bridging should start and end with two (2) spaces of solid bridging. Between the start and end spaces, a repetitive pattern of solid bridging at ten (10) feet on center and strapping on the laterally unbraced flange can be used. Joist bridging should be placed as follows:
Span1' - bridging required 14 ft1' - one row at mid-point 14 to 20 ft1' - two rows at third points Over 20ft1' - one row every 6 ft
In an engineering sense, when is 50-ksi materials required in lieu of 33-ksi materials?
The 33-ksi or 50-ksi refers to the “grade of steel” or its yield point. This is a material property for strength, not for stiffness or resistance to deflection. Generally speaking, 50-ksi materials tend to be more likely required in high load applications (heavy floors, heavily loaded load bearing studs, load bearing headers). 50-ksi steel is generally available in the 16 gauge (54 mil) and thicker steel. 33-ksi is generally available in 18 gauge (48 mil) and thinner steel. 50-ksi is rarely required in curtain wall applications.
What floor live loadshould I use for a joist application?
The nation’s model building codes, BOCA, SBC and UBC all have minimum required floor live loads (PSF). The 3 codes, for example, use a 40 PSF floor LL for residential, 50 PSF floor live load for offices and a 125 PSF floor live load for light storage. Since these are minimum required loads, higher loads may be required for a specific project.
Stamped shop drawings maybe required for some projects. How much time is required to get a full engineering package with a state stamp?
Lead times for engineering consultants vary depending on backlog. In addition, after the engineering consultant receives that contract documents (architectural drawings, structural drawings and owner’s specification), a proposal or contract (which includes cost and schedule) is prepared by the engineer. The proposal also requires a signature from the customer in order to formally begin the work; this can take a few days. Using 1 week as an average backlog, it is best for the customer to allow for 3 weeks of preparation for a final stamped engineering package. Contact Cemco for obtaining stamped engineering packages.
Are screws connections required by the industry instead of welded connections?
The AISI Specification for the Design of Cold-Formed Steel Structural Members (1996) included design guidelines for both screws and welded connections. In other words, both methods, generally speaking, are equally acceptable. What usually determines screw versus welded connections are project specific conditions or the contractor’s preference for means of fastening.
What allowable deflection should be specified for non-load bearing applications?
The main purpose of specifying an allowable stud deflection for non-load bearing framing is actually for determining what is an acceptable deflection for the wall facing materials. A metal stud is ductile and therefore can perform at a wide range of deflections. The wall facing materials tend to be more brittle and thus have a more stringent maximum allowable deflection. The model building codes UBC, BOCA and SBC allows L/120 for brittle finishes and l/240 for walls with flexible facing material. The project architect or project specifications should note what the allowable deflection is for a given wall facing material.
I am interested in getting involved with the use of light gauge steel framing. How do I get started?
Order the Cemco catalog, CD-ROMand visit our Web Site at www.cemcosteel.com
Call Cemco Technical Service at(800) 416-2278 for further assistance.
I am building a steel joist/load bearing wall system. Do the joists need to be in line with the load bearing studs below?
The short answer is yes. Typically the top track will not have sufficient bending strength to allow offset joist. However, if the joist will be offset from the load bearing studs below, a structurally adequate distribution member needs to be provided between the joists above and the load bearing studs below. It is advised to have the project engineer specify the distribution member system.
What are the basic functions of the AISI and ASTM organizations and standards as they apply to the light gauge steel framing (LGSF) industry?
The American Iron and Steel Institute (AISI) publishes the Specification for the Design of Cold-Formed Steel Structural Members. This Specification provides engineers, other professionals and industry the various formulae for the load carrying capacity of light gauge steel framing. The American Society for Testing and Materials (ASTM) provides the minimum and consistent requirements for the material properties used in steel framing systems. In addition, ASTM provides basic guidelines or requirements for the installation of steel framing members.
