Experimental study of steel pipe and reinforced concrete wall connections under lateral loading

Abstract

Abstract This study investigated the lateral load resistance performance of connection joint of a reinforced concrete (RC) wall structure connected to steel pipes. Four cases of connections were examined: a case where the anchor plate, which is a combination of the widely used base plate and anchor stud, was exposed at the upper section of the RC wall; a case where it was embedded at a depth of 100 mm; a case where the steel pipe was embedded directly into the RC wall and filled with concrete; and a case where the steel pipe was not filled with concrete but had its ends blocked with base plates. Steel pipe–anchor plate or steel pipe–steel pipe connections were made with screw joints in all cases. Although all four cases resisted a greater load than the design load, their performance and failure modes differed. The load resistance performance was better when the base plate was embedded in the RC wall than when it was exposed above the RC wall, but this was found to increase strain and cracking of the RC wall. Breakage of the screw joint led to the yielding of the steel pipe. In contrast, if the screw joint did not break, a shear breakout failure of the RC wall occurred without the steel pipe yielding. The change in failure mode with the breakage of the screw joint was confirmed through a finite element analysis that modelled the screw joint as a hinge. Moreover, the presence of a base plate was determined to slightly affect the breakage of the screw joint. The breakage was severe when there was a base plate and insignificant in the contrary case. Furthermore, rib reinforcing was found to alleviate screw joint breakage even when a base plate was present. Therefore, the connection method where the steel pipe was directly embedded in the RC wall has a greater probability of shear breakout failure even without the screw joint breaking, and the degree of breakage was found to be unpredictable by the relationship suggested by contemporary anchor design formulae. Hence, to employ the method of directly embedding a steel pipe in an RC wall, a design formula that can adequately predict the concrete shear breakout capacity due to the insufficient edge distance needs to be developed.