Improving the Cyclic Behavior and Post‐Fire Performance of the Prequalified ConXL Connection

ABSTRACT Although box columns offer significant advantages, they also have limitations, particularly regarding the design of connection plates and their shear strength at connections. The introduction of ConXL, recognized as a prequalified solution under AISC regulations, addresses these issues. This well‐known connection offers several benefits, including improved industrialization and quality control, elimination of continuity plates, faster construction times, and streamlined inspections. This paper presents an innovative approach that utilizes T‐stubs to enhance the performance of ConXL with unfilled box columns. The study evaluates the behavior of both conventional and enhanced ConXL connections under ambient conditions as well as elevated temperatures to assess their seismic performance and resistance after fire exposure. The findings reveal that all variants of ConXL exhibited stable hysteresis curves. Even when exposed to temperatures up to , these connections maintained a rotational capacity exceeding 0.04 rad without developing plastic hinges at the joints. It is feasible to remove concrete if it leads to a necessary increase in column thickness; an appropriate equation for this adjustment was proposed. Additionally, incorporating T‐stubs significantly improved the behavior of ConXL connections at higher temperatures. Comparative analyses showed that the use of T‐stubs increased the ultimate strength of the system by factors of 1.08, 1.11, 1.10, and 1.87 for , , , and , respectively. Furthermore, an equation was proposed for predicting system behavior based on these findings.