Alternative Formula for Rigid Pavement Stress Calculation in Corner Load Conditions

The design of rigid pavements is historically based on the classical Theory of proposed by Westergaard in 1929, which considers the rigid pavement as a thin plate resting on an elastic ground with a Winkler reaction, imposing the congruence of vertical displacements at the points of contact between the pavement structure and the ground. Westergaard’s Theory provides expressions for the calculation of maximum stress in concrete slabs for interior, edge and corner load conditions. This work focuses on the development of a Finite Element model, implemented in the ANSYS® environment and calibrated on the basis of the results of the in-scale experimental model developed by Lall and Lees in 1983. The implementation of the FE model was performed through a set of steps capable of reproducing physical and mechanical conditions of the true model, which was further intended to be used for numerical analysis. After the FE model was developed, it was possible to carry out multiple simulations pursuing three main aims: to evaluate the effect of the variation of material properties on the slab stress state, to compare the maximum stresses for the interior and edge load conditions considering Westergaard’s Theory, the experimental data and the results of the numerical model, and to use the developed and calibrated model to formulate an alternative mathematical expression, which would allow calculating the stress in corner load conditions.

Key Characteristics of a Floating Slab Track Based on Longitudinal Interaction Analysis

The passage of railway vehicles produces mechanical vibrations across an extensive range of frequencies. A floating slab track (FST) has recently been proposed and constructed in Korea to reduce the vibrations and noise that result from typical railway operation. The main objective of this study is to investigate the behavior of an FST by means of an interaction analysis of a track-slab-isolator. Key FST parameters considered in this study are additional rail stress, slab stress and displacement, and stopper displacement. The FST parameters include slab length and thickness, isolator stiffness, and longitudinal stiffness. The sensitivity of the key characteristics of each FST parameter is examined. This study also determines the maximum length of an FST based on the maximum additional rail stress criterion. Finally, a formula to predict maximum additional rail stress is proposed for the design of FST systems.

Analysis of Stress and Deflection about Steel-Concrete Composite Girders Considering Slippage and Shrink & Creep Under Bending

Steel-concrete composite beams are composed of concrete slabs and steel girders by shear connectors. Due to the limited rigidity of shear connector, and the shrink & creep property of concrete, relative slippage exists between the concrete slab and steel girder under bending, and it is difficult to analyze the effect of those factors by the ordinary beam theory, the finite element method(FEM) and so on. A differential equation of equilibrium is constituted corresponding to the compatibility of deformation and the equilibrium of forces of steel-concrete composite beams under particular assumed condition. Finite difference method (FDM) and variation principle are used to solve the differential equation. An example of steel-concrete composite T girder is given to analyze the effect of slippage and concrete shrink & creep on its stress and deflection. The concrete slab stress increases with increased rigidity in the shear connectors. The stress of the steel girder and the deflection of the composite girder decrease with increment in the rigidity of the shear connectors.

Model Tests Study on the Bending Properties of the External Pre-Stressed Combination Box Girders with Corrugated Steel Webs

In order to study actual work performance of the external pre-stressed combination box girder with corrugated steel webs, and to analyse the integral stress of box girder influenced by the corrugated steel webs, and understand the construction of the type combination box girder, this document studied the model test of the external pre-stressed combination box girder with corrugated steel webs, tried to find out the bending rule for the combination box girder and the model test result influenced by the different connections style. And the model test result was based on the assumption of “flat section” and within the elastic range, when the concentrated loads loaded on the box girder, the deflection was linear with the loads, and the corrugated slab stress was zero, which indicated the slab can not bended and the moment was supported by the top and the bottom slab, and the corrugated slab only supported the shear, and the shear lag effect only influenced local area. The conclusion of the model test will provide the reference for the bending capacity research, design and construction.

Influence of Structural Parameters on Mechanical Properties of Double-Block Ballastless Track

A high degree of integrity is the most remarkable feature that makes double-block ballastless track different from other ballastless track structure. Based on the beam/plate theory on elastic foundation, influences of several structural parameters (such as size of track slab and support layer, support stiffness of the subgrade, etc) on stress of the ballastless track system under the axle load of 300kN were studied in order to obtain further understanding of the mechanic performance of double-block ballastless track under the train load. Results show that: structure of double-layer combined structure should be adopted to decrease the stress of each layer of ballastless track; the width of support layer should be less than 3.6m; because the ratio of track slab stress to support layer stress is larger than the ratio of their strength, the width of track slab in the double-layer separated structure should be 280mm or less.