汉代建筑大木作技术特征(之三)——柱(础)、梁枋、平坐腰檐

该文对汉代建筑大木作之柱(础)、梁枋、平坐腰檐等技术进行研究,联系考古发掘实物资料,现代研究论著等,进行系统的分析、论证。

Novel hybrid FRP tubular columns for sustainable mining infrastructure:Recent research at University of Wollongong

This paper introduces, for applications in the mining industry, an innovative hybrid column form which consists of an inner steel tube, an outer fibre-reinforced polymer(FRP) tube and an annular concrete infill between them. The two tubes may be concentrically placed to produce a section form more suitable for columns, or eccentrically placed to produce a section form more suitable for beams. The FRP is combined with steel and concrete in these hybrid structural members in such a way that the advantages of FRP are appropriately exploited while its disadvantages are minimized. As a result, these hybrid members possess excellent corrosion resistance as well as excellent ductility and seismic resistance. This paper summarizes existing research on this new form of structural members, and discusses their potential applications in mining infrastructure before presenting a summary of the recent and current studies at University of Wollongong(UOW) on their structural behaviour and design.

A review of flexibility-based finite element method for beam-column elements

For material nonlinear problem,elements derived with the flexibility-based method are more accurate than classical elements derived with the stiffness-based method. A review of the current state of the art of the flexibility-based finite element method is provided to enhance the robustness of structure analysis. The research on beam-column elements is the mainstream in the research on flexibility-based finite element method at present. The original development of flexibility-based finite element method is reviewed, and the further development of this method is then presented in several specific aspects, such as geometrically nonlinear analysis and dynamic analysis. The further research needed to be carried out in the future is finally discussed.

Mechanical characteristics of columnar jointed rock at dam base of Baihetan hydropower station

Irregular columnar jointed structure is a primary irregular columnar morphological tensile fracture. In order to study the geometric features of irregular columnar joints and the new problems in geotechnical engineering, hydraulic and hydropower engineering caused by columnar jointed basaltic mass, Voronoi graph from geometry was introduced to simulate the irregular columnar jointed basaltic mass at Baihetan hydraulic station. Discrete element software UDEC was used to simulate the whole process of rigid bearing plate test. Anisotropic constitutive of columnar joints was adopted to analyze the stress diffusion of rock mass at dam base of Baihetan. The results show that, the compaction property and hysteresis effect are well simulated based on discrete element simulation of Voronoi joint structure by UDEC. Four stages of cyclic loading and unloading process are imaged clearly. The results from in situ rigid bearing plate tests are explicated and the stress diffusion rule of anisotropic body is affected by structure surface. The elements in the stress state of 4-5 MPa are the most, about more than 35% of the total. Appropriate constitutive must be proposed to columnar jointed rock mass with different styles. It has important significance to realize the nonlinear mechanical behavior of irregular columnar jointed basaltic mass.

Structural Analysis Programme Based on the Equivalent Column＇s Method

The focus of this article is to accomplish a program using MatLab software, which will determine the global behavior of the structure, the stress, stability and frequency of the tall building with ＂n＂ levels. The program starts with the global analyses based on the equivalent column theory. The central core consists of reinforced concrete shear walls of the elevator＇s tubes and of the staircase, design to resist the lateral loads. Applying the equivalent column＇ s theory, the bracing system will be replaced by an equivalent column, considered to be a vertical cantilever fixed at the base and the loads will be applied in the shear center axis. The program using mathematical and physical relations, has as input dates the geometrical and stiffness characteristics of the plan of the building and as output dates the critical load, the fundamental frequency, the maximum stresses and deformations of the structure.

Constructal optimization of cylindrical heat sources with forced convection based on entransy dissipation rate minimization

Based on constructal theory and entransy theory,the optimal designs of constant-and variable-cross-sectional cylindrical heat sources are carried out by taking dimensionless equivalent resistance minimization as optimization objective.The effects of the cylindrical height,the cylindrical shape and the ratio of thermal conductivity of the fin to that of the heat source are analyzed.The results show that when the volume of the heat source is fixed,there exists an optimal ratio of the center-to-centre distance of the fin and the heat source to the cylinder radius which leads to the minimum dimensionless equivalent thermal resistance.With the increase in the height of the cylindrical heat source and the ratio of thermal conductivity,the minimum dimensionless equivalent thermal resistance decreases gradually.For the heat source model with inverted variable-cross-sectional cylinder,there exist an optimal ratio of the center-to-centre distance of the fin and the heat source to the cylinder radius and an optimal radius ratio of the smaller and bigger circles of the cylindrical fin which lead to a double minimum dimensionless equivalent thermal resistance.Therefore,the heat transfer performance of the cylindrical heat source is improved by adopting the cylindrical model with variable-cross-section.The optimal constructs of the cylindrical heat source based on the minimizations of dimensionless maximum thermal resistance and dimensionless equivalent thermal resistance are different.When the thermal security is ensured,the optimal construct of the cylindrical heat source based on minimum equivalent thermal resistance can provide a new alternative scheme for the practical design of heat source.The results obtained herein enrich the work of constructal theory and entransy theory in the optimal design field of the heat sources,and they can provide some guidelines for the designs of practical heat source systems.

Intrinsic mode characteristic analysis and extraction in underwater cylindrical shell acoustic radiation

Target dimension is important information in underwater target classification. An intrinsic mode characteristic extraction method in underwater cylindrical shell acoustic radiation was studied in this paper based on the mechanism of shell vibration to gain the information about its dimension instead of accurate inversion processing. The underwater cylindrical shell vibration and acoustic radiation were first analyzed using mode decomposition to solve the wave equation. The characteristic of acoustic radiation was studied with different cylindrical shell lengths, radii, thickness, excitation points and fine structures. Simulation results show that the intrinsic mode in acoustic radiation spectrum correlates closely with the geometry dimensions of cylindrical shells. Through multifaceted analysis, the strongest intrinsic mode characteristic extracted from underwater shell acoustic radiated signal was most likely relevant to the radiated source radius. Then, partial information about unknown source dimension could be gained from intrinsic mode characteristic in passive sonar applications for underwater target classification. Experimental data processing results verified the effectiveness of the method in this paper.