Ultimate load carrying capacity of the Lu Pu steel arch bridge under static wind loads

This paper investigates the ultimate load carrying capacity of the Lu Pu Bridge under static wind loads through the spatial finite element model. Both geometric and material nonlinearities are involved in the analysis. The Lu Pu Bridge is a long-span half-through-type steel arch bridge with a 550 m-long central span under construction in Shanghai, China. This will be the longest central span of any arch bridge in the world. Three load combinations are used in the ultimate load capacity analysis of the bridge. Combination I: combined dead and live loads over the entire bridge. Combination II: combined dead and wind loads. Combination III: combined dead load, wind load and live load over the entire bridge. Ultimate load capacity of the bridge is first investigated under load combinations I and II. Attention is paid mainly to investigate the load capacity of the bridge under load combination III. In the case of load combination III, the influences of several parameters (i.e., loading sequence, three components of wind loads and wind loads of individual bridge element) on the ultimate load capacity of the bridge are discussed. It is concluded that wind loads result in significant reduction in the ultimate load capacity when applied wind loads become large.     

Optimization of practical trusses with constraints on eigenfrequencies, displacements, stresses, and buckling

In this paper we consider the optimization of general 3D truss structures. The design variables are the cross-sections of the truss bars together with the joint coordinates, and are considered to be continuous variables. Using these design variables we simultaneously carry out size optimization (areas) and shape optimization (joint positions). Topology optimization (removal and introduction of bars) is only considered in the sense that bars of minimum cross-sectional area will have a negligible influence on the performance of the structure. The structures are subjected to multiple load cases and the objective of the optimizations is minimum mass with constraints on (possibly multiple) eigenfrequencies, displacements, and stresses. For the case of stress constraints, we deal differently with tensile and compressive stresses, for which we control buckling on the element level. The stress constraints are imposed in correlation with industrial standards, to make the optimized designs valuable from a practical point of view. The optimization problem is solved using SLP (Sequential Linear Programming).     

电力系统储能问题初步探讨

电网负荷有高峰和低谷特性。针对电力系统的负荷峰谷特性，探讨了如何用电池贮能系统调节电力负荷，从而提高电力系统的经济效益。认为用蓄电池调节电网的峰谷负荷差在技术上是可行的；还介绍了日本在这方面的概况。     

有源电力滤波器抑制谐波的机理分析

研究了中低压电网中由非线性负载产生谐波的机理，提出所有由非线性负载直接引起的谐波是电流谐波，因而治理非线性负载引起的谐波应首先考虑治理谐波电流。同时，从补偿和滤波两种思想出发，指出并联型谐波补偿有源电力滤波器(APF)的补偿作用和串联型基波补偿APF的滤波作用可适用于非线性负载谐波电流的抑制。仿真结果验证了理论分析的正确性。     

重载轻型桁架斜拉式组合挂篮的研究

主要介绍了重载轻型桁架斜拉式组合挂篮的结构形式、特点，分析了其计算模型，并通过工程算例的验证，表明了该种挂篮结构合理、构思独特．与其它结构形式的挂篮相比，它受力较为均匀、节省材料、减轻自重，是一种较为理想的新型挂篮结构，有实际应用价值．     

单层网壳结构在简单荷载下动力稳定分析

根据网壳结构的动力稳定判别准则，采用精确的空间梁单元切线刚度矩形式及大转角理论，通过二个典型算例，分别考查在突加阶跃荷载，简谐荷载及三角形脉冲荷载作用下，单层网壳结构的动力稳定性能，并得到了一些主要结论。     

单跨圆弧梁的设计与计算

介绍了圆弧梁在均布荷载作用下的内力计算和配筋计算。     

大功率混合型APF用于大型冶炼厂谐波治理

为消除电力系统谐波及其巨大危害,根据大型冶炼厂谐波治理的特点,提出了一种新颖的拓扑结构-大功率混合型有源滤波器,它将串联谐振注入型有源滤波器与无源滤波器并联混合,由电容静态补偿无功功率,由有源和无源部分共同抑制谐波。实践证明该装置具有较好的滤波效果和一定的无功补偿能力。     

Vibration Control of Wind-Excited Tall Buildings Using Sliding Mode Fuzzy Control

A sliding mode fuzzy control (SMFC) is proposed to design a controller for the third-generation benchmark problem on wind-excited buildings. A distinctive feature in vibration control of large civil infrastructure is the existence of large disturbances, such as wind, earthquake, and sea wave forces. Those disturbances govern the behavior of the structure; however, they cannot be precisely measured, especially for the case of wind excitations. Since the structural accelerations are measured only at a limited number of locations without the measurement of the wind forces, the structure of the conventional control may have the feedback loop only. The general structure of the SMFC, proposed herein, is composed of a compensation part and a convergent part. The compensation part prevents the system from diverging, and the convergent part directs the system to the sliding surface. The compensation part uses not only the structural response measurement but also the disturbance measurement, so the SMFC has a feedback loop and a feedforward loop. To realize the virtual feedforward loop for the wind-induced vibration control, a disturbance estimation filter is introduced. The structure of the filter is constructed based on an autoregressive model for the stochastic wind force. This filter estimates the wind force at each time instance based on the measured structural responses and the stochastic information of the wind force. For verification of the proposed algorithm, numerical simulation is carried out on the benchmark problem for wind-excited buildings. The results indicate that the present control algorithm is efficient for reducing the wind-induced vibration.     

Identification and Validation of a Discrete Element Model for Concrete

The use of a three-dimensional discrete element method (DEM) is proposed to study concrete structures submitted to dynamic loading. The aim of this paper is to validate the model first in the quasistatic domain, and second in dynamic compression, at the sample scale. A particular growing technique is used to set a densely packed assembly of arbitrarily sized spherical particles interacting together, representing concrete. An important difference from classical DEMs where only contact interactions are considered, is the use of an interaction range. First, the correct identification of parameters of the DEM model to simulate elastic and nonlinear deformation including damage and rupture is made through quasistatic uniaxial compression and tension tests. The influence of the packing is shown. The model produces a quantitative match of strength and deformation characteristics of concrete in terms of Young’s modulus, Poisson’s coefficient, and compressive and tensile strengths. Then, its validity is extended through dynamic tests. The simulations exhibit complex macroscopic behaviors of concrete, such as strain softening, fractures that arise from extensive microcracking throughout the assembly, and strain rate dependency.