Performance of CFS Beam-to-Beam Bolted Connection Using Clip Angle and Flange Strip: Experimental Investigation

Abstract

This paper presents an experimental investigation on the strength, load versus deflection, and load versus rotation behavior of cold-formed steel (CFS) beam-to-beam connections using a combination of clip angle and flange strip through the use of bolts and self-drilling screws in the webs and flanges, respectively. A total of 24 tests with four different aspect ratios in the loaded leg and three different aspect ratios in the anchored leg for two different clip angle thickness were carried out under four-point bending to study the strength and different failure modes under flexure. The dimension and number of screws in the flange strip connecting the top flanges of the channels to provide restraint against end lateral displacement and rotation at both ends of connection were kept constant. The results indicate that the end rotation depends on the number of bolts in the clip angle connected to the loaded channel and the thickness of the clip angle. A higher degree of stiffness was exhibited by the three-bolt configuration for both thicknesses of the clip angle. The optimum anchored aspect ratio with regard to the strength was found to be 1.0 and 1.5 for the clip angle thicknesses of 0.8 and 1.5 mm, respectively. Three different failure modes were observed in the clip angle: local buckling, distortional buckling, and bearing in the bolt hole. The ultimate strength increased up to 70% due to the flange strip connection provided at the top of flanges by the application of self-drilling screws. Comparison of the experimental results with literature study indicates the literature approach is ultraconservative in both serviceability and ultimate state. Based on the test results, a new design method was developed for determining the nominal shear strength with consideration of deformation. The load and resistance factor design (LRFD) resistance factor and allowable strength (ASD) safety factor were found to support the modified design equation.