Effects of design factors on the cyclic response of sloped RBS moment connections

Abstract

Abstract Non-orthogonal structural framing is essential in modern architectural design; and sloping beams are often required in structures, particularly at the roof level. In this paper, a sensitivity study is conducted to statistically evaluate the effect of beam slope angle along with different design factors on the cyclic response of Reduced Beam Section (RBS) moment connections. To this end, 3D finite element models are developed and verified based on two sets of experimental studies. The verified models are then used to carry out a sensitivity analysis employing the design of experiment (DOE) method. Thirteen design factors, related to the connection material or geometry, are considered. The analyzed RBS connection models, which are generated based on DOE, conform to the AISC seismic design requirements for RBS connections in special moment frames. The cyclic response of RBS connection models is assessed by evaluating different response variables, including initial stiffness, rupture index, plasticity index, moment capacity, yield moment, hysteretic energy dissipation, and strength degradation rate. The results show the relative significance of each factor and interaction effects on the cyclic response of RBS connections. Based on the results, slope angle and beam depth are the most significant factors influencing all the response variables. The beam slope angle and beam depth both have increasing effects on the cyclic response characteristics. With up to 80% contribution, the effect of beam slope angle is found to be significant and greater than the beam depth effect. RBS connections with smaller beam slope angle and beam depth experience lower strain demands and less potential for fracture.