Narrow Results

This study investigates the relationship between the temperature and the modal frequencies of bridges through a series of model experiments using a concrete continuous beam bridge model and a steel cable-stayed bridge model in a controlled-temperature chamber. The experimental results show that, for a given boundary condition and in the absence of freezing, a change in temperature affects the structural frequencies of the bridge as it alters the elastic modulus of the bridge materials. The structural frequency tends to linearly decrease with increasing temperature and with the decrease in the frequency of steel bridges smaller than that of concrete bridges. For the particular case of wet concrete bridges, the temperature dependencies of modal frequencies vary dramatically near the freezing point, which is attributable to the freeze–thaw process of concrete pore water. The effect of air humidity on structural frequency is less significant than that of temperature when the boundary conditions remain unchanged. Furthermore, temperature changes may alter the boundary conditions of bridges, thereby affecting the structural frequencies.

In order to realistically restore the mechanical properties of the arch bridge under load and damage processes, a coupled dual nonlinear analysis method is established for the arch-bridge load–carrying capacity by considering the effects of bidirectional force transfer and adaptive section stiffness. First, based on the geometric nonlinear theoretical method of bidirectional force transfer, the macroscopic structural deformation of arch ribs under different loading conditions and load levels is preliminarily calculated, including the bending and axial deformation of each section of the arch, which is used to characterize the development of plasticity. According to deformation or strain, the fiber model analysis method is used to determine the true moment–curvature and axial force–curvature development paths of key sections, and then the elastic–plastic flexural and compressive stiffnesses of each section under different deformation states are derived. The elastic–plastic stiffness is substituted back to the geometric nonlinear equations to obtain the deformation and internal force along the arch ribs considering the cross-sectional plasticity. Finally, the above process is cycled until the equivalence condition is satisfied between the structural internal force/deformation and cross-sectional ones. In order to verify the rationality and accuracy of such a coupling method, a model test is carried out on a stiff skeletal concrete suspension chain line arch with a span of 12m, whose results match satisfactorily with that of calculated by the coupling dual nonlinearity method. Compared with the method suggested in the code JTG3362-2018, the proposed method can better predict the development of deflection of different arch rib sections, as well as the actual internal force state. The bending moment calculated as per the code is 7–16% larger than the test result at the ultimate capacity state, while the method of this paper is within 5%.

A new method to simulate soil-structure interaction effects in shaking table tests has recently been presented by the authors. In this method, analog circuits or digital signal processors are used to produce soil-foundation interaction motions in real time. Their expressions of soil-structure interaction motions are based on published rigorous formulations of impulse response functions or flexibility functions of foundations resting on or embedded in homogeneous or layered soils of semi-infinite extent. In this paper the method is further extended to take the "far field" soil non-linearity into account. An example of non-linear soil-structure interaction simulation using the present method is also described.

According to the differential equation of thin elastic vibrating sheet and the similarity theory, the similar relationships between model and prototype are established. A high accuracy non-contact laser displacement measuring system is developed to obtain the surface deformation of the ice-like material. A speed measurement and positioning system is established for the moving air cushion load. At different speed of moving load, a series of experiments are carried out in towing channel which the depth of water is variable. At critical speed the maximum deformation of ice-like material can be caused.

The composite box-girder bridge with corrugated steel webs is a new type of bridge structure. It was originally often used for continuous beam and continuous rigid frame bridges, and with its ever-expanding applied range and rising requirement of the span, domestic and foreign designers also begin to apply it in larger span bridges such as cablestayed bridge and partially cable-stayed bridge. In the consideration that partially cablestayed bridge appeared later and its structure itself is relatively new, the application of this bridge type with corrugated steel webs as box girder webs in domestic and overseas is not widespread. It is necessary to conduct a comprehensive research on the mechanical properties of partially cable-stayed bridge with corrugated steel webs. Combined with existing research results, this paper relies on one domestic and newly built partially cablestayed bridge with corrugated steel webs called Zhengzhou to Dengfeng Fast Track Chaoyanggou Reservoir Bridge (hereinafter referred to as “Zhengzhou Chaoyanggou Reservoir Bridge”) as engineering background. The research on the shear lag effect for partially cable-stayed bridge with corrugated steel webs is conducted through experimental study and finite element analysis, which is helpful to deeply understand the mechanical properties and application of this structure.