Large-scale experimental study on the mechanical behavior of a steel-UHPC composite truss arch under high compressive stress state after cyclic construction

Abstract

To break through the three technical bottlenecks of traditional arch bridges, namely, excessive self-weight, high cost and difficult construction, a low-carbon and high-performance steel-ultra high performance concrete (UHPC) composite truss (SUCT) arch bridge was proposed. After the completion of the cyclic construction, the stress superposition effect makes the stress states of the inner and outer arches different. After the completion of the bridge, the SUCT arch has a high compressive stress reserve to make full use of the compressive strength of UHPC. In this paper, the most unfavorable asymmetric loads were applied to the SUCT arch (16 m) after cyclic construction to study its mechanical performance under high compressive stress state. The cracking behavior, failure mode, and deflection and strain responses were mainly discussed. The nominal cracking and crushing stresses were analyzed. The damage evolution law of the SUCT arch and other composite arches was compared, and the corresponding design suggestions were put forward. The results indicate that the SUCT arch exhibits a brittle failure mode of small eccentric compression, with visible cracks (≤0.04 mm) and crushing only occurring at the spring on the loading side. The stress superposition effect causes the inner arch to crack and crush before the outer arch. The bearing capacity of the SUCT arch is controlled by the compressive strength of UHPC, which can give full play to the excellent compressive performance of UHPC. When the maximum crack width is 0.02 mm, the nominal cracking stresses of the inner and outer arches are 3.5 times and 4.9 times of the elastic ultimate strength, respectively, and the nominal crushing stress of the inner arch (178 MPa) is 2.5 times of the design value of the compressive strength, indicating that the SUCT arch has excellent crack resistance and compressive performance. The compressive safety reserve of the SUCT arch is obviously lower than that of crack resistance, which indicates that the design of SUCT arch bridges is mainly controlled by compression. When designing the SUCT arch, the reinforcement ratio of the longitudinal steel bars and the requirement for the tensile strength of UHPC can be appropriately reduced, and the compressive strength can be appropriately improved, especially in the spring area. Furthermore, the sliding connector can be further optimized to reduce the stress superposition effect, so that the stress states of the inner and outer arches tend to be consistent, and the bearing capacity and crack resistance can be further improved. This study can be used to guide the design and application of new arch bridges.