Material Properties And Numerical Analysis Of Bridge Approach Filled With High Performance Lightwight Concrete

The reasonable transition of the junction location of the infrastructure under the track is one of the research hotspots. The using of light weight concrete for the backfilling of subgrade behind the abutment back is a method to solve the problems of bridge approach essentially. While there is little research about the application of light weight concrete in railway engineering. In order to meet the requirements of load and structure of railway bridge approach, the mechanism properties of the fiberglass reinforcement high performance light weight concrete (HPLWC) were studied by laboratory tests. Moreover, the static analysis and dynamic analysis of HPLWC bridge approach were taken out by the PLAXIS 2D and ABAQUS. The analysis results show that:(1)The mechanical strengths of HPLWC are higher than that of ordinary lightweight concrete. With the increase of fiberglass content, the mechanical strengths of HPLWC increase first and then decrease. There are optimal values of fiberglass content. The optimal values of fiberglass content of HPLWC with different densities are different, and the optimal values increase with the increase of density. The reinforcing effect of fiberglass can improve the plasticity properties of HPLWC. The modification effec is not very obvious for the HPLWC with low density (less than 400kg/m3).(2)The using of light weight concrete for the backfilling of subgrade behind the abutment back can effectively reduce the horizantal displacement of abutment, but it could increase the rotation angle of abutment in a certain degree. However, the values of rotation of abutment can meet the requirements of design code. The relationship between the backfilling material density and the additional stress in bridge foundation is linear correlation. The using of light weight concrete for the backfilling of subgrade behind the abutment back can effectively reduce the settlement of foundation surface and existed subgrade. When the filling material is graded broken stone, the shape of subgrade surface settlement longitudinal disribution curves is a typical concave shape. And under the assumption in this theis, the deflection angles of subgrade surface exceeded the limits, moreover, the radius of curvature of subgrade surface settlement longitudinal distribution curves could not meet the requirement of design code. When the filling material is HPLWC, the shape of settlement of subgrade surface longitudinal disribution curves is a typical linear slope shape.(3)The relationship between the vertical acceleration and the train speed is linear correlation. The decay rate of acceleration in HPLWC is smaller than that in common soil subgrade. With the increase of HPLWC density, the acceleration decrease. Train speed and HPLWC density have only little effect on the decay law of acceleration along the depth, while the structural types of bridge approach have obviou effect on the decay law. From the bridge to subgrade, the amplitude of vibration acceleration gradually increases. Train speed has little effect on the longitudinal distribution law of acceleration amplitude. The accelerations of the straight trapezoid are larger than that of the reverse trapezoid. The decay law of dynamic stresses along the depth is familliar with the law of acceleration. Train speed and HPLWC density have only little effect on the lateral distribution law. The larger the elastic modulus of bridge approach materials is, the more uniform the lateral distribution of dynamic stresses is. The longitudinal distribution law of dynamic displacement is famillar with the law of acceleration. The larger the elastic modulus of bridge approach materials is, the smaller the dynamic displacement amplitude is. The reverse trapezoid is the recommended design of structural type. The vibration of bridge approach belongs to low-frequency vibration. The frequency range of main vibration is from 0 to 45 Hz.(4)The staitic and dynamic analysis results of bridge approach showed that all the evluation indexes of HPLWC bridge approach could meet the requirment of design code, and the indexes are better than that of GBS bridge approach. The maximum value of HPLWC density control range is 800kg/m3.In gerneral, the HPLWC has better plastic properties. The HPLWC when applied in the backfilling of subgrade behind the abutment back could reduce the effect on the abutment, and it has good dynamic properties. So, the HPLWC has good application protential in the bridge approach engineering of high-speed railway. The research above may offer reference for the design of bridge approach filled with the HPLWC.