Design of steel brace connection to an RC frame using Uniform Force Method

Steel bracing is a viable alternative to a shear wall when designing or retrofitting reinforced concrete frames for seismic loads. Directly connecting the bracing system to the RC frame is the most cost effective method of joining the two systems together. In this paper, the design basis for such a connection is set out and controlled for accuracy and safety. To this end, numerical models of steel brace/RC frame connections are developed and verified against experimental results obtained from similar connections. The numerical models are then used to evaluate the efficiency of the analytical Uniform Force Method (UFM) used for connecting braces to steel frames and adopted here for connecting braces to RC frames. It is found that the UFM can be applied effectively and conservatively to design brace/RC frame connections. A detailed investigation on the level of overdesign is also carried out through parametric analyses of the main problem variables including the brace angle and dimensions of the gusset plate. It is found that, for most practical cases, the error in using the UFM analytical approach is less than 20%. Finally, necessary considerations for design of different components of the brace-frame connection are set out.