Seismic Behavior of Double-Layer Space Frames with Concrete Slabs Under Different Support Conditions

The connection between the space frame and its supporting columns is a critical aspect of structural design. The way these two elements are joined significantly influences the overall stability, load transfer, and behavior of the entire structure. This study investigates the seismic behavior of composite double-layer space frames with reinforced concrete (RC) slabs under three alternative support configurations: simple point supports, inverted-pyramid supports, and crosshead-beam supports. A detailed finite element (FE) model was developed in ABAQUS to conduct a nonlinear time-history analysis under recorded earthquake excitation. The selected record captures the temporal variation in ground motion and enables an accurate assessment of structural response under dynamic loading. The Concrete Damage Plasticity model was incorporated into the analysis of the concrete slab. The steel was modeled using an elastic–plastic material behavior to mimic the formation of plastic hinges. Maximum lateral displacements, base shear forces, and hysteretic behavior were studied to evaluate the comparative performance of the systems. The results show that the inverted-pyramid configuration reduced vertical (Y-direction) displacement by 33.6% compared to the simple point support. At the same time, the crosshead-beam system exhibited similar levels of vertical displacement. However, it exhibited significantly enhanced energy-dissipation capacity, with hysteretic force ranges up to 1250 kN, compared to approximately 922 kN and 860 kN for the simple point and inverted configurations, respectively. In the X-direction (lateral displacement), the simple support and inverted-pyramid cases showed comparable responses, whereas the crosshead-beam configuration exhibited greater displacement, indicating reduced lateral stiffness. Overall, the results of this study indicate that the inverted-pyramid system improves displacement control, and the crosshead-beam configuration provides superior hysteretic energy dissipation. These findings highlight the importance of selecting appropriate support configurations in the seismic design of composite space frame systems.