Seismic Performance and Strength Prediction of Precast RC Shear Walls with Openings for Cavity Structures Crossing Underground Utility Tunnels

Abstract

Additional loads from new buildings spanning existing underground utility tunnels, together with seismic action, may induce uneven settlement and structural damage in tunnel systems. To mitigate this risk, a precast cavity structure is proposed to replace the soil above the tunnel, isolating load transfer and controlling settlement. In the proposed structure, precast reinforced concrete shear walls with openings serve as key vertical load-carrying and lateral-force-resisting members. To clarify the cyclic behavior, two shear walls with openings were designed to possess the same geometry and reinforcement details but were tested under reversed cyclic loading in two orthogonal in-plane orientations. The failure modes, hysteretic behavior, backbone curves, stiffness degradation, and energy-dissipation capacity were analyzed. The results show that flexural-shear failure occurred in both wall limbs under horizontal cyclic loading, whereas flexural-shear failure developed only in the right wall limb under vertical cyclic loading. The initial stiffness, peak load, peak drift ratio, and ultimate drift ratio under horizontal cyclic loading were 1.87, 2.06, 1.76, and 1.64 times those under vertical cyclic loading, respectively, indicating that the performance of the shear wall with opening is more unfavorable under vertical cyclic loading. Further, existing models were used to predict the loading-carrying capacity. The results indicate that the strut-and-tie model (STM) and GB 50010-2010 gave the best and acceptable overall predictions, respectively. The findings provide experimental evidence for component design and seismic performance evaluation of cavity replacement structures used in projects spanning underground utility tunnels.