Large-scale model test on the construction process of a stiff skeleton arch bridge with the span of 600 m

The Tian'e Longtan Bridge, with a span of 600 m, is the world's longest arch bridge, surpassing similar structures by 34.8 %. To ensure the construction safety of Tian'e Longtan Bridge, a largescale model test was conducted using the stress equivalence principle, with a scale ratio of 1:10. The experiment simulates the entire construction process of gradually wrapping concrete by layers and segments on a stiff skeleton, with data collected from 401 stress points and 28 displacement points, revealing the evolution of structural deformation and stress during arching process. The results show that during the pouring of encasing concrete, the maximum compressive stress in the steel tubes is 235.5 MPa, located at the upper chord of the midspan, while that of the encasing concrete is 10.6 MPa and located at the bottom plate of the 3/8 span. The maximum stress ratios that cannot be transmitted between the concrete on both sides of the interface between layers and segments are 6.8 % and 5.8 %, respectively, which demonstrates the reliable stress transmission at the interfaces. The elastic deflection at midspan is 53.2 mm when the bottom slab is closed, while only an additional deflection of 3.3 mm occurs during subsequent construction of the web slab and top slab, which indicates that most deflection occurs before the closure of the bottom plate. The deflection at the arch crown caused by shrinkage and creep is 42.3 mm. In contrast, the calculation result based on the uniaxial shrinkage and creep theory is 54.7 mm, 29.3 % larger than the test result.