Pengfei Li

Theoretical and Experimental Study on Natural Frequency of Externally Prestressed Box-Girder with Corrugated Steel Webs

Abstract: Based on the characteristics of box girder with corrugated steel webs, the existing prestressing force, the effect of shear deformation of composite girder on the deflection, “folding effect” in longitudinal direction of corrugate steel webs and the arrangement of external tendons were considered comprehensively. With the experiment results of five literatures integrated, N/fcA (the axial compression ratio) was selected as regression parameter to develop a regression equation for the effective cross-section stiffness of the girder. Then a formula for natural frequency of the externally prestressed box girder with corrugated steel webs was proposed. Finally, the in-situ measurement on an actual bridge and a laboratory dynamic test on the model box girder with seven prestressing levels were conducted. The test results showed that the natural frequency of box girders with corrugated steel webs increased along with the growing external force. In contrast to other related formulas, the calculated results of the formula proposed in this paper showed the same tendency with measured results and the maximum error is 1%.

Effect of Parameters on Soil-Structure Interaction of a Buried Corrugated Steel Arch Bridge

Based on an actual corrugated steel plate arch bridge, considering soil-structure interaction, by using the finite element program of ANSYS, a 2-D finite element model was set up to analyze the soil pressure and structural deformation under different load conditions in detail. Since this type of structure relies on the soil-structure interaction to share the load, as the structural parameters have a strong effect on the mechanical characteristics of the structure. So the soil pressure and deformation of the structure were analyzed by changing the parameters, such as the cross-section of corrugated steel plate, the elastic modulus, internal friction angle and Poisson’s ratio of the backfill soil. The analysis shows that soilstructure interaction redistributes stress in the surrounding soil and reduces the adverse influence of excessive structural displacement. Results reveal that the stiffness decrease of the corrugated steel plate is positive to the soil-structure interaction and reduces the vertical soil pressure. The increase of elastic modulus of backfill soil is positive with respect to soilstructure interaction and leads to smaller soil pressure to the steel arch. Larger internal friction angle of the backfill soil increases the difference of soil pressure within and outside the span and has slightly negative effect to the soil-structure interaction. Soil with smaller Poisson’s ratio has some positive effect in reducing soil pressure to the steel arch.

Experimental Study on Mechanical Properties of Improved Multi-Grid Composite Wall

Two types of improved multi-grid composite wall called point contact multi-grid composite wall and light-steel skeleton multi-grid composite wall were proposed in this paper. In order to study the mechanical properties of improved multi-grid composite wall, the low-cycle reduplicative loading tests of 1/2 scale improved multi-grid composite wall were carried out. Through the analysis of testing phenomenon and final test results, the main failure patterns and failure processes of the walls were summarized, and the mechanical characteristics of improved multi-grid composite wall were discussed, then the seismic performance including bearing capacity, ductility, and hysteretic characteristics were researched. The experimental foundations were provided for the further theoretical research and application of improved multi-grid composite wall in practical application.

Calculation Method of the Horizontal Displacement on the Multi-Grid Composite Wall-Shear Wall Structure

The multi-grid composite wall-shear wall structure (the hybrid structure discussed in this paper) is a new dual structural system consisting of the multi-grid composite walls and the RC shear walls. Because of the shear deformation of the composite walls subject to arbitrary loads, it is not accurate to calculate the horizontal displacement of the hybrid structure by using the displacement formulations of the frame-shear wall structure. And therefore, a displacement calculation method for the hybrid structure subjected to horizontal loads should be proposed. In this paper, the composite walls are viewed as shear-flexural type cantilever walls and the shear walls as flexural type cantilever walls. Based on the Timoshenko beam theory, the displacement differential equation of the hybrid structure is proposed by the continuum method. The analytical solutions of the displacement equation for the hybrid structure subject to the inverse triangle load are obtained with boundary conditions. The example indicates that the lateral displacement curve of the hybrid structure from the proposed method exhibits a shear-flexural type characteristic in which the shear deformation should not be ignored.

Structure-Soil Interaction of Buried Corrugated Steel Arch Bridge

Corrugated steel plate and surrounding soils are working together to share the load in buried corrugated steel structures. It is complicated to consider the structure-soil interaction, so the finite element method has already become the chief means of complicated structure analysis. Based on a practical project, considering structure-soil interaction, by using the finite element program of ANSYS, the paper set up a 2-D FE model and analyzed the soil pressure, the structural deformation and the internal force under different load conditions in detail. The analysis shows that structure-soil interaction has brought about stresses redistribution of surrounding soils, and adverse effects of soil pressure and displacement were limited. The variation range of soil pressure on the crown of arch increases with the load increases and the peak value of soil pressure approach to the code value and a rebound appears in the vehicle load range. The tendencies of vertical soil displacement are nearly the same to different load conditions, and the peak value of moments has an obvious change and can be influenced greatly by deflective load.

Influence of External Tendons on Dynamic Characteristics of Box Girder with Corrugated Steel Webs

Based on Miyamoto’s method, the natural frequency of prestressed box girder with corrugated steel webs considering the impact of external tendons was obtained. And the result was modified based on the finite element model. It shows that: the external tendons will reduce the natural frequency of bridge with reduced range of about 3%. Beneficial references were provided to the layout of external tendons in order to avoid the resonance between the box girder with corrugated steel webs and the external tendons.