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The research on the development of a reliable analytical model for seismic analysis of steel structures is presented. The non-linear damage cumulation hysteretic model incorporating the deterioration of stiffness, strength and strain hardening for structural steel is proposed and validated. The complete loading history, energy dissipation and the effect of the maximum plastic strain are taken into account in the model. The constants in the model are determined from regression analysis of experimental results of simple standard tensile and cyclic tests. Finite element formulations for beam and structural solid element considering the damage cumulation are derived. A computer program capable of calculating the hysteretic model of steel members, predicting the damage state and crack initiation, and carrying out non-linear time history seismic analysis of steel structures is developed. Solutions obtained from the model are in good agreement with experimental results. It was demonstrated that the damage cumulation effect is considerable and important in structural seismic analysis.

Arc-length-type and energy-type methods are two main strategies used in structural nonlinear tracing analysis, but the former is widely used due to the explicitness and clarity in conception, as well as the convenience and reliability in calculation. It is very important to trace the complete load-deflection path in order to know comprehensively the characteristics of structures subjected to loads. Unfortunately, the nonlinear analysis techniques are only workable for tracing the limit-point-type equilibrium path. For the bifurcation-point-type path, most of them cannot secure a satisfactory result. In this paper, main arc-length-type methods are reviewed and compared, and the possible reasons of failures in tracing analysis are briefly discussed. Some improvements are proposed, a displacement perturbation method and a force perturbation method are presented for tracing the bifurcation-point-type paths. Finally, two examples are analyzed to verify the ideas, and some conclusions are drawn with respect to the arc-length-type methods.

In this paper, shaking table tests of two shallow reticulated shells under earthquake loading were described. Local and global dynamic instabilities were observed in the test and time–history curves for stresses of members and nodal displacements were given respectively. It was shown that there were sudden changes in these curves, which were regarded as the signs of local and global dynamic instability. Based on test results, the law of structural dynamic instability was summarized, the definition of dynamic instability and several practical criteria proposed by the authors were illuminated. Finally, some calculation results from theoretical analyses of the two models under static and dynamic loading were given. By comparison of them, it can be seen that there are many common properties that reflect the stability behaviors and can be used to determine the state of static and dynamic stability of structures.

In order to consider the effects of damage cumulation on the structural responses, a damage model for steel structural members based on plastic strains of the material has been proposed. Adopting the hypotheses of elasto-plastic damage hinges and the damage concentrated at the ends of a steel member, a hysteresis model for plane steel members with effects of damage cumulation has been built. The proposed model can consider the following effects: strain hardening effect and strength degeneration effect caused by damage cumulation. Finally, by means of this model, an elasto-plastic stiffness matrix is built for plane steel members with damage cumulation effects.

In this paper the curved-shell finite-element method is adopted to analyze the ultimate strength of compressed stiffened plates with different stress gradients, the interaction curves \IP\N′\N/\IP\dy\N′\N-\IM\N′\N/\IM\dp\N′\N of thin-walled square box sections, and the interactive instability of axially and eccentrically loaded square box columns. The principal modes of initial imperfections are taken into account in analysis. Comparison between the results of the prevailing specifications and the theory of this paper is presented. Errors of the specifications are checked. Equations for calculating the ultimate strength of centrically loaded and bending stiffened plates and thin-walled square box sections are proposed based on the theoretical results. A simple interaction equation is presented for calculating the ultimate strength of eccentrically loaded sections. And, finally, effective design methods for axially and eccentrically loaded columns are suggested. The results of the suggested methods are in good agreement with those of the finite-element method.

A piezoelectric cantilever (PEC) consists of a piezoelectric layer, e.g., leadzirconate titanate (PZT) bonded to a non-piezoelectric layer, e.g., silica. Compared to other current biosensing technologies, PEC's ability to withstand damping in water and its all-electric, self-exciting, self-sensing features make it stand out for in-liquid biosensing applications that is in-situ, real-time, multiplexed, and high throughput.The scaling analysis of PECs shows that reducing a PEC's dimension can increase its mass sensitivity dramatically. The goal of the thesis study is to fabricate miniaturized piezoelectric micro-cantilever sensors (PEMS) with femtogram mass detection sensitivity (10-15 gram/Hz) for biological and chemical sensing applications. To achieve the goal, the thesis study encompasses three major components: (1) fundamental studies on the sensor physics to allow an optimal sensor design, (2) lead zirconate titanate (PZT) sol-gel thin film development, (3) microfabrication of the PZT PEMS.For the fundamental study, the effects of the sensor's geometry on its detection sensitivity were examined both theoretically and experimentally to show that a proper nonpiezoelectric extension enhances a PEMS detection sensitivity. Using a unique sol-gel method using ethylene glycol as the solvent, dense, smooth, and defect-free PZT thin films were obtained with superb dielectric and ferroelectric properties, an intrinsic dielectric constant εint=2100 and a saturation polarization Ps=55 μC/cm2. Integrating with silicon based micro-fabrication technologies, PZT/SiO2 PEMS 300 to 40 m long were successfully fabricated exhibiting resonance peaks with high quality factors ranging from 120 to 320. Mass detection sensitivities of 6.7 ×10-16 g/Hz and 9.1 ×10-16 g/Hz (mass of a single virus or a fraction of a single cell) were obtained with 40 m and 60 m PZT/SiO2 PEMS, respectively, in humidity detection---the smallest and most sensitive PZT based PEMS ever reported.

Publisher Summary The chapter analyzes and models several cast steel joints used in Pudong Cadre Institute. It is hard to evaluate by simple joints because too many members are connected in a same joint. For the reason of aesthetics and mechanics, cast steel joints were preferred. Stress distribution is calculated using the finite element method. Some suggestions are proposed on element number, details of geometric modeling, and so on. Cast steel joints are mechanically more advantageous under complex joint details connecting many members. Cast steel joints with good properties, simple construction, as well as low cost will win engineers' favor. Comparison with traditional joints, the distinct advantage of cast steel joints is their ability to avoid stress concentration, and optimize geometric shape of joints dependent on stress distribution and value. The chapter explains that a cast steel joint can suit the complexity of the joint style.

Publisher Summary The chapter discusses structural scheme selection of a super tall building. On structural scheme selection of a high-rise building, designers first advise several structural systems based on their experience after analyzing the proposed project. Then several specialists determine the optimal alternative. However, this method has some disadvantages of higher random, dependence on individual capacity, bigger work, uncertainty, and more difficulty to contrast. It primarily depends on comparing with existing buildings rather than depending on computing. Therefore, for structural scheme selection of a super tall building, this method will yield diverse general economic benefits. The chapter presents another way. At first, architects confer with designers and find several preliminary schemes satisfying project demands. Then, a multilevel structural model on structural scheme selection of a super tall building is proposed. The chapter also provides division of technical economic index into three parts: mechanic behavior index, seismic behavior index, and economic performance index.

Publisher Summary This chapter presents the results of the tests undertaken on the full-scale truss composed of arch-beam and cable used in the roof structure of Shanghai Pudong International Airport Terminal. These tests were undertaken in the stages of prestressing and loading conditions respectively. The terminal buildings are composed of four successive function areas called R1, R2, R3, and R4 respectively. Each roof structure is a large span steel-truss system with no lateral bracing at all. The steel truss is composed of arch-beam and prestressing cable called cable-beam. The prestressing process has two stages: buildup of the integrity structural rigidity and accretion of the integrity structural rigidity. A total number of one hundred and eleven strain gauges and three tensometers were distributed on the roof truss and anchor rod, and eleven displacement transducers were used to measure the vertical deflections of the truss and the horizontal displacements of the supports. The tension-only element is adopted for the end segments of the cable, where a couple of forces are added to simulate the tension from the anchor device.

A finite element approach is presented in this paper for analysis of nonlinear behaviour of steel frames under local fire conditions. The effects of geometric nonlinearity, temperature dependent material nonlinearity and variations in temperature distribution across sections of frame members are considered. Based on the principle of virtual work, the temperature - induced load vector and temperature - dependent geometric stiffness matrix are derived. Following the common procedure of finite element methods, a. computer program is developed for calculating either the ultimate load at a specified temperature or critical temperature at a specified load level. The effectiveness of the approach is verified by a good prediction on the behavior of a steel frame experienced fire experiment.

Publisher Summary This chapter discusses the model of the spatial roof structure of the 80,000-seat stadium in Shanghai, made up of radial cantilevering main trusses and annular linking girders, and is tested under four different combinations of loads. A comprehensive investigation of static behavior of this saddle-shaped spatial truss structure is explained. Topics covered are: design of the structural model, structural behaviors under different load cases, computational model selection, comparison of the finite element method (FEM) predictions and the test results, and spatial work behaviors of this overall truss system. Based on both theoretical and experimental analysis, proposals on design and analysis of the real structure are put forward.