Multistory Rigid Frames with Composite Girders Under Gravity and Lateral Forces

Much work has been done in the area of composite design using the strength of the concrete floor slab and steel girders acting together by means of shear connectors. The major portion of the work done to date has pertained to beams or girders, simply supported or continuous, acted upon by vertical loads. Little information is found in the literature on the design and use of composite girders in multistory rigid frames, when horizontal loads govern the design of the girders. The use of composite design of girders in multistory rigid frames subjected to severe horizontal loads can lead to substantial material savings.9 Using recent research involving the response of composite sections in positive moment regions adjacent to columns, stiffness factors can be developed for use in analysis and subsequent design. This paper compares preliminary designs, with and without composite girders, of a 12-story, two-bay, asymmetrical rigid frame subjected to wind loading. The effects of governing design parameters, such as varying story height, longitudinal steel in the negative moment region, and the length of composite partial slab width adjacent to columns, are discussed and a recommended procedure for designing with composite girders is presented.