Numerical Investigation on the Dynamic Performance of Steel–Concrete Composite Continuous Rigid Bridges Subjected to Moving Vehicles

Assembly construction is the main feature of industrialized bridges, and π-shaped section steel–concrete composites that are continuously rigid have been widely used in engineering fields in recent years; however, their dynamic responses and corresponding impact coefficients in positive and negative moment regions need to be further studied. First, considering the interface slip model, we established a finite element model for the π-shaped continuous region section of the steel–concrete composite on the Sutai Expressway Tongfu No. 3 viaduct. Second, the bridge deck unevenness parameters were generated by preparing a MATLAB program with random calculations and were added to the bridge deck as the excitation load along with the vehicle load. Such parameters are defined on the basis of considering the vertical degrees of freedom of the four wheels and of one vehicle rigid body. Finally, we analyzed the displacement or stress impact coefficients as the dynamic response index of the bridge by adjusting the vehicle travel speeds, vehicle weights, interface slip stiffness values, and deck unevenness values. The results show that the change in vehicle travel speed and the change in vehicle load weight have some influence on the change in the dynamic effect of the combined beam, but this change is not significant. Moreover, the unevenness and interface slip strength changes have a large effect on the dynamic effect of the combination beam, which can significantly change the impact coefficient of the combination beam bridge. The worse the unevenness of the bridge deck is, the lower the grade of interface slip for the steel–concrete composite bridges and the higher the impact coefficient. We calculated the recommended impact coefficient values of the steel–concrete composite bridge based on the specifications for various countries, and they range from 1.16 to 1.4; such values are similar to the finite element calculation results.

Interface Slip of the Steel Beam Strengthened with the CFRP Sheet under Temperature and Creep

This paper studied the interface slip between the CFRP sheet and the steel beam under the action of temperature and creep. The formulas of the interface slip were established by using the elastic method and energy variational method, respectively, and the accuracy of the formulas was verified by finite element analysis Abaqus. The results showed that when the creep was not taken into account, the interface slip was the maximum at the end of the beam and the minimum at the middle of the span. When the temperature increased to 5°C, the slip increased about 0.005 mm. And when the thickness of the CFRP sheet increased to 0.05 mm, the slip increased about 0.003 mm. When the creep was taken into account, the interface slip increased with the increase of load and decreased with the increase of stiffness. When the stiffness reached about 10 ka, the variation of the stiffness on the slip was basically unchanged.

Soil–building Interaction under Surface Horizontal Strain Induced by Underground Mining

Underground mining will cause the ground to deform, leading to the destruction of buildings. Horizontal strain is one of the most important causes of damage to strip foundation buildings. However, related research is insufficient, making the mechanism of building damage caused by horizontal strain unclear and resulting in several difficulties in performing coal mining under villages. In this study, interface slip and soil pressure caused by the horizontal strain of ground transfer between soil and buildings are investigated, and stress concentration in buildings driven by soil movement is considered the primary cause of building damage. The influences of the mechanical parameters of the soil and the geometric parameters of building on stress distribution inside a building are analyzed by establishing a stress distribution model of a building under different ground horizontal strain. Softening the foundation or designing deformation joints inside a building can reduce the influence of horizontal strain on the building. This research can provide an important reference for performing coal mining safely under villages and designing building protection against ground horizontal strain.

Strengthening of reinforced concrete beams: RC versus UHPFRC layers

<p>Strengthening of Reinforced Concrete (RC) beams is of high importance for the structural upgrade of existing buildings. The majority of the existing RC structures need to be upgraded either because they are designed with old or without seismic code provisions or because of existing damages. In this study the effectiveness of the use of traditional RC layers is compared with the use of Ultra High Performance Fibre Reinforced Concrete (UHPFRC) layers. Experimental investigation has been conducted on beams strengthened with these two techniques and the effectiveness of the examined methods has been evaluated via comparisons of the load-deflection and the interface slip results.</p>

Experimental investigation on composite beams under combined negative bending and torsional moments

In this study, straight composite steel-concrete beams were tested to investigate their mechanical performance under combined negative bending and torsional moments. Two specimens were used in this study, and different ratios between the applied negative bending and torsional moments were induced. Load and deflection relationships, strain development on the steel main girder and shear connectors (stud), and the slip development on the steel-concrete interface were recorded in the test and reported in this paper. The results indicate that increase of torsional moment will result in the significant decrease of the load-carrying capacities (e.g. yield load and ultimate load) of the specimens. It was also found that the normal strains of stud shear connectors in such beams are very large and non-negligible compared to their shear strains. In addition, the maximum interface slip was found occurring at around the 1/4 span, and the support conditions and serious crack of the concrete were considered to be the main causes. The research results obtained in this study can provide references for the design and analysis of steel-concrete composite beams subjected to the combined negative bending and torsional moments.