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.
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.