In order to establish accurate compressive constitutive model of Hybrid Fiber-Reinforced Concrete (HFRC), 10 groups of HFRC specimens containing polyvinyl alcohol (PVA), polypropylene (PP), and steel fibers are designed and compressive testing is conducted. On the basis of summarizing and comparing the existing research, accuracy of various stress-strain constitutive model is compared and the method of calculating fitting parameters is put forward, peak stress, peak strain, and elastic modulus of specimens with different fiber proportion are analyzed, the calculation expressions of each fitting parameter are given. The results show that, under the condition that the volume of the hybrid fiber is 2% with the proportion of the steel fiber increase, the strength of the specimen increases, the peak strain decreases slightly, and the elastic modulus increases significantly. In specimens mixed with PVA-PP hybrid fiber, with the increase of PVA fiber proportion, the peak stress and elastic modulus of the material are improved, and the peak strain are decreased. The existing stress-strain expressions agree well with the tests. Accuracy of exponential model proposed in this paper is the highest, which can be applied in engineering and nonlinear finite element analysis of components.

A curved bridge test model with a scale ratio of 1:10 was constructed to investigate the influence of site conditions on curved bridges with longitudinal slopes based on a similar theory. The natural ground motions of five different groups, namely, Sites A–E, were selected from the Pacific Earthquake Engineering Center (PEER) seismic database, and the shaking table model test was conducted under horizontal unidirectional and bidirectional excitations. Results showed that the structural response of the curved bridge is sensitive to the ground motion of different site conditions. Spatial characteristics are observed in the main girder structural response of the curved bridge. When the curved bridge is parallel to the direction of the principal ground motion, the rotation effect of the main girder is greater than that perpendicular to the direction of the principal ground motion. The rotation effect of the main girder leads to evident beam end and bearing displacements at the low pier. The seismic excitation direction and pier height notably affect the displacement response of the pier, and the tangential displacement response of the fixed pier is sensitive to seismic excitation.

A low tower cable-stayed bridge with a span of 30m+60m+120m+60m+ 30m had been built before Guidelines for Seismic Design of Highway Bridge was promulgated. Because of its importance and specificity, it is necessary to do research on seismic performance of the bridge. Based on three-dimensional finite element model, it is found that the bearing deformation across the bridge is very big, and it might be destroyed if earthquake happened. In this article, a new damper (Metal Alloy Brace) is used to achieve seismic strengthening. Under frequently occurred earthquake excitation, MAB will supply a small stiffness, but its hysteretic curve is plump, so the structural deformation is reduced. Under rare earthquake excitation, MAB can supply so big stiffness that the structural deformation is limited, and the damper will also dissipate much energy. Through comparing, it is found that MAB is better that caging device. And the damper has no problem with leakage and metamorphism. So, MAB has a good prospect in seismic strengthening.

Taking Zhoutouzui Immersed Tunnel as an example, finite-infinite element model of immersed tunnel-joint-soil is developed. Through numerical calculation, dynamic response of the tunnel and its joints is studied in detail under different joint stiffness. The objectives of these researches are to provide strong technical support for immersed tunnel projects in China, provide theoretical and experimental basis for revision of the seismic code, accumulate information to establish the analysis theory and design method, and understand the possible damage mechanism of underwater tunnel structures.

The frequency content of earthquake ground motion is one of the important factors which affect the dynamic response of structural systems. Because of the uncertainty of characteristic period T_g and amplification coefficient β, the results of seismic response under the ground motions will be affected by its uncertainty. So, the research on this topic becomes so necessary. Based on the ground motions during the 2008 Wenchuan earthquake, the uncertainty of T_g and β is analyzed and the maximum value, the minimum value, the mean value, the standard deviation and the coefficient variation are presented finally.