Shape and Mechanical Behavior of Geotextile Tubes

Nowadays, geotextile tubes hydraulically filled with dredged materials have been used in the application of cofferdam, sea reclamation and deepwater channel regulation in China. The shape and mechanical behaviors during the process of filling, consolidation and stacked are one of the main problems concemed by designers and researchers.This paper uses the method of elliptic integrals to study the behaviors of filling and deduces the regressive formulas of shape features and circumferential tension. The results show that the proposal regressive formulas are only the function of pressure at bottom; they are very convenient and suitable for the filling design. When the filling materials are sandy, the shape and mechanical behaviors nearly remain during the process of consolidation. The behaviors of stacked geotextile tubes are very complex, because they are involved in the properties of the filling material, geotextile and foundation.Using the commercial finite element analysis program ABAQUS, this paper establishes the entire 2- D finite element load model to investigate, which include the part of filling material, geotextile and foundation. The numerical results suggest that the maximun circumferential tension varies with the properties of filling materials and foundations, whereas the largest tensile force occurs during the filling process.

Axial Mechanical Properties of Timber Columns Subjected to Freeze-Thaw Cycles

The behaviour of timber columns subjected to freeze-thaw cycles under axial compression is presented in this paper.A total of forty specimens,including twenty circular timber columns and twenty square timber columns,were tested under axial compression.The failure modes,ultimate bearing capacity,ductility coefficient,load-displacement curves and load-strain curves were obtained and analyzed.The number of freeze-thaw cycles(from 0 to 80)and the specimens’height(from 225 mm to 360 mm)were considered as the main parameters.After freeze-thaw cycles,there was no obvious change on the surface of the timber columns.The test results showed that freeze-thaw cycles could reduce the ultimate bearing capacity of the timber columns,and the average reduction of the ultimate bearing capacity of the specimen reached 28%.The ductility coefficient of the square specimens subjected to freeze-thaw cycles almost remains constant compared with that of the square timber columns left untreated.While the ductility coefficient of the circular timber columns increases after freeze-thaw cycles.In addition,based on the extensive experimental analysis,a regression formula is derived to predict the ultimate bearing capacity of the timber columns after being subjected to freeze-thaw cycles,which is proved to be reasonable accurate.

TYRE DYNAMICS MODELLING OF VEHICLE BASED ON SUPPORT VECTOR MACHINES

Various methods of tyre modelling are implemented from pure theoretical to empirical or semi-empirical models based on experimental results. A new way of representing tyre data obtained from measurements is presented via support vector machines （SVMs）. The feasibility of applying SVMs to steady-state tyre modelling is investigated by comparison with three-layer backpropagation （BP） neural network at pure slip and combined slip. The results indicate SVMs outperform the BP neural network in modelling the tyre characteristics with better generalization performance. The SVMsqyre is implemented in 8-DOF vehicle model for vehicle dynamics simulation by means of the PAC 2002 Magic Formula as reference. The SVMs-tyre can be a competitive and accurate method to model a tyre for vehicle dynamics simuLation.