SHI Zhou, WANG Chi, LI Jiahui, FENG Chuanbao, HU Zunsen, QU Guozhao, ZHAO Ziyue
Journal of Railway Engineering Society. 2026, 43(7): 29-35.
Research purposes: Steel truss arch bridges with separated girder systems exhibit substantial structural rigidity and favorable seismic performance. However, the arch-crossbeam joint at the arch base features an intricate interlaced arrangement of transverse and longitudinal diaphragms, resulting in complex mechanical behavior and load transfer mechanisms. To investigate the structural response characteristics of the arch-crossbeam joint under seismic and other operational conditions, based on the Beijing-Hangzhou Grand Canal Bridge of the Weifang-Suqian Railway with a main span of 300 m in a high seismic intensity zone, this paper employs localized refined simulation analysis to study the arch-crossbeam joint's mechanical properties, stress distribution patterns, and force transmission mechanisms.
Research conclusions: (1) Under rare earthquake conditions, the structural load effect is more significant, and the stress level of the plates is higher than that under the main-plus-auxiliary load case by 60% to 130%. The stress concentration of the joint is distributed at the junction of the arch web plate and the bridge deck, as well as at the locations of geometric changes and support constraints. The maximum stress at the junction between the bottom of the outer arch web and the crossbeam under rare earthquakes reaches 450 MPa, which is still within the safe range. (2) The stress distributions of the arch rib plates under the two working conditions are generally similar, gradually decreasing along the arch axial direction from the bridge deck upward. The stress exhibits local peak distributions along the axial direction due to the influence of diaphragms. Among these, the web of the arch rib experiences the most unfavorable stresses, with a maximum stress reaching -429 MPa. The stresses in the webs on both sides of the arch rib are markedly greater than those in the internal webs, establishing them as the primary load-bearing components. Stresses in the vertical direction for the top and middle welds, as well as the crossbeam bottom plate, are approximately zero, confirming that the joint primarily transmits horizontal loads. (3) Under two working conditions, the outer arch rib web plates transmit 53.6% and 52.0% of the horizontal force, respectively, being the main force transmitting components. The internal arch rib web plates transfer less than 10% of the load, indicating weak force transmission. The arch rib crossbeam welds transmit 97.2% and 96.6% of the horizontal force through shear, respectively, making them the main ways of horizontal force transmission. (4) The research findings offer valuable insights for optimizing the design of long-span arch-girder composite bridges in high seismic intensity regions.