Yu Zhiwu

Behavior of concrete and concrete-filled circular steel tubular stub columns at constant high temperatures

Based on reanalyzing test results of uniaxial compressive behavior of concrete at constant high temperatures in China, with the compressive cube strength of concrete from 20 to 80 MPa, unified formulas for uniaxial compressive strength, elastic modulus, strain at peak uniaxial compression and mathematical expression for unaxial compressive stress-strain relations for the concrete at constant high temperatures were studied. Furthermore, the axial stress-axial strain relations between laterally confined concrete under axial compression and multiaxial stress-strain relations for steel at constant high temperatures were studied. Finally, based on continuum mechanics, the mechanics model for concentric cylinders of circular steel tube with concrete core of entire section loaded at constant high temperatures was established. Applying elasto-plastic analysis method, a FORTRAN program was developed, and the concrete-filled circular steel tubular (CFST) stub columns at constant high temperatures were analyzed. The analysis results are in agreement with the experiment ones from references.

Research on Optimized Design of Internal Spatial Organizations on Theories of Space Syntax

Introducing theoretical techniques of space syntax, this paper explored internal spatial organizations of passenger stations at high-speed railways by theoretical research and case analysis. Space accessibility and intelligibility were quantitatively analyzed by extracting connectivity, integration and intelligibility from the space syntax. Thus, internal spatial organizations of passenger stations at high-speed railways were evaluated and optimized on a quantitative basis. Besides, errors resulting from designs based on experience were avoided and design methods for spatial organizations of passenger stations at high-speed railways were proposed. Engineering, design and application of bedpan.

Evaluation and Research of Site Selection Based on Performance of Urban Spatial Structures

As a node of transport network, high-speed railway transport hub is concerned with urban spatial structures in terms of its site selection and equipped with transport functions. As a critical node of cities, it imposes direct impacts upon quality and image of urban space, thus affecting structures and efficiency of urban space. Based on performance density, performance stretch ability and OD ratio, this paper calculated weighted coefficients of these three indices for evaluating performances of urban spatial structures, established a system for assessing site selection of high-speed railway transport hub and further simplified the evaluation system to obtain standard rating scales. This evaluation system may analyze specific location of a high-speed railway transport hub in detail and is the basis for location planning of the hub.

The reasonableness of vibration equation being used to solve wave equation

The solution of longitudinal wave of a column through vibration equation taken as an example, the vibration equation was proved to converge to wave equation when the discrete spatial size converges to be infinitesimal. Concept of calculation wave velocity was proposed. Waves propagation could be seen in the vibrations solution obtained with central difference method when calculation wave velocity equal to physical wave velocity. The physical meaning of stability requirement of central difference method was revealed, that is, calculation wave velocity must be equal to or greater than physical wave velocity.

Comparison of vibration equation's solution with wave equation;s theory solution

Newmark method was used to calculate base reaction force of column under longitudinal vibration and the comparison of this methods solution under commonly used calculation condition with wave equations theory solution showed the great importance of choosing time step size when guaranteeing the correctness of vibration equations solution.

Experimental research on the mechanical properties of steel after high temperature

Publisher Summary The chapter provides an overview of an experimental research on the mechanical properties of steel after high temperature. According to the experimental research, experimental phenomena and mechanical properties of steel after high temperature is influenced by several factors including peak temperature and peak temperature exposure time. With the exposure temperature up, the yield strength and the tensile strength tend to decrease as a whole, while the elastic modulus of steel and Possions ratio remains constant. The exposure time hardly has any influence on steel. Based on the experimental research, formulas for Possions ratio-stress ratio curves and stress-strain curves of steel after high temperature, and empirical calculation formulas for yield strength and tensile strength are suggested in the chapter. The calculated results show good agreement with the experimental results. Research achievements offered in the chapter have reference for further non-linear finite element analysis and design of concrete-filled steel tubular structure and steel structure after fire.