Seismic performance of corner post-corner fitting connections in assembled-type light steel modular house

As an essential form of temporary construction, assembled-type light steel (ATLS) modular houses play a vital role, particularly in emergency response and disaster relief operations. The seismic performance of their structural connections is fundamental to ensuring overall safety. This study systematically investigates the influence of the connecting plate thickness of the corner fitting, bolt grade, internal stiffeners within the corner fitting, bolt arrangement, and bolt preload on the seismic behavior of corner post-to-corner fitting connections through full-scale quasi-static tests. The experiments revealed three primary failure modes: local buckling of the corner post, bolt pull-out, and a composite failure involving both. The results indicate that increasing the thickness of the connecting plate on the corner fitting from 8 mm to 12 mm enhanced the positive and negative yield loads by 20.27 % and 26.59 %, respectively. The incorporation of internal stiffeners in the corner fitting increased the connection stiffness by approximately 18 %. In contrast, the bolt grade and preload magnitude had a relatively limited effect on the connection's bearing capacity. The mechanical behavior is analyzed using a validated finite element model. All tested connections are classified as semi-rigid according to EC3 ( 0.5 k b E I b / L b ≤ S j , ini ≤ k b E I b / L b ). A component-based spring model is developed to predict the initial rotational stiffness and shows good agreement with test results, with average discrepancies of 6.3 % under positive and 7.1 % under negative loading, and a maximum error below 12 %. Based on this, a method for calculating the ultimate moment capacity is proposed, providing a theoretical basis and practical reference for the seismic design of ATLS modular houses.