Pseudo-Static Tests on Top Joints of Hybrid Precast Utility Tunnel

This paper introduces a new type of hybrid precast MUT, consisting of precast composite top slab and double-skin sidewalls with reserved rebar. The seismic behavior of the top joints was examined through pseudo-static tests. Four full-scale specimens, including both exterior and interior precast joints, in addition to two corresponding cast-in-place (CIP) joints, were fabricated and subjected to reversed cyclic loading. The results showed that both the precast and CIP joints exhibited flexure failure, characterized by the formation of a plastic hinge at the end of the sidewall. The hysteresis curves of both precast and CIP joints exhibited comparable shapes and quantities of hysteresis loops. The load-carrying capacities for exterior precast joints and corresponding CIP joints were 141.25 kN and 143.5 kN, exhibiting a difference of less than 1.6%. The load-carrying capacities for interior precast and corresponding CIP joints were 60.5 kN and 62.75 kN, displaying a variance of less than 3.6%. The precast specimens demonstrated comparable levels of ductility, energy dissipation, and structural integrity as the CIP specimens. These findings provide validation for designing and analyzing the hybrid precast utility tunnel using identical principles and models as applied CIP structures.

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