Ru-Cheng Xiao

Nonlinear aerostatic stability analysis of Jiang Yin suspension bridge

Abstract A nonlinear aerostatic stability analysis of the Jiang Yin suspension bridge over the Yangtse River in China is carried out in this paper. We propose a new nonlinear method to analyze aerostatic stability of suspension bridges, based on both the three components of wind loads and geometric nonlinearity. A computer program NASAB, based on the proposed method, has been developed. The accuracy and efficiency of the computer program is examined by numerical examples. The effects of some important parameters on the aerostatic stability of the Jiang Yin bridge are studied. The results show that considering the effect of wind angle of attack on the slope of the curve of pitch moment coefficient is significant for the aerostatic stability analysis of the bridge. The displacement response under the displacement-dependent wind loads exhibits strong nonlinearity. The aerostatic instability of the bridge can exhibit asymmetric flexural–torsional instability in space. Wind angle of incidence and wind loads of cable have major effect on the aerostatic stability of the bridge.

Aerostatic stability analysis of suspension bridges under parametric uncertainty

This paper presents a new method (series method) for the deterministic aerostatic stability analysis of suspension bridges. The geometric nonlinearity in the deflection theory and the three components of displacement-dependent wind loads are taken into account in the method. The accuracy and efficiency of the method are verified through the comparisons with existing nonlinear and linear methods. Second, an efficient and accurate algorithm is proposed to perform aerostatic stability analysis with parametric uncertainty. The proposed algorithm integrates the concepts of the direct Monte Carlo simulation and the series method. A numerical example is used to verify the proposed algorithm. Finally, a sensitivity analysis on the aerostatic stability with respect to changes in the system parameters is performed using response surface method (RSM). The results show that RSM is simple, practical and accurate.

Series method for analyzing 3D nonlinear torsional divergence of suspension bridges

A simplified method for analyzing 3D nonlinear torsional divergence of suspension bridges is proposed in this paper. The geometric nonlinearity in the deflection theory and the three components of displacement-dependent wind loads are taken into account in the method. This method is a two-step process: the calculation of deflection response under the displacement-dependent wind loads, and the calculation of the critical wind velocity. The response under the displacement-dependent wind loads is calculated from Fourier series. The critical wind velocity is calculated by means of an iterative method. It is found that a small number of iteration cycles and Fourier coefficients are sufficient enough for convergence. The advantages of the proposed method are showed by a comparing the numerical results of this method with those obtained from the linear method and nonlinear finite element methods.

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.

Probabilistic free vibration analysis of beams subjected to axial loads

Abstract A stochastic finite-element-based algorithm for the probabilistic free vibration analysis of beams subjected to axial forces is proposed in this paper through combination of the advantages of the response surface method, finite element method and Monte Carlo simulation. Uncertainties in the structural parameters can be taken into account in this algorithm. Three response surface models are proposed. Model I: star experiment design using a quadratic polynomial without cross-terms; Model II: minimum experiment design using a quadratic polynomial with cross-terms; Model III: composite experiment design using a quadratic polynomial with cross-terms. A separate set of finite element data is generated to verify the models. The results show that the Model II is the most promising one in view of its accuracy and efficiency. Probabilistic free vibration analysis of a simply supported beam is performed to investigate the effects of various parameters on the statistical moments of the frequency response of beams. It is found that the geometric properties of beams have significant effects on the variation of frequency response.

Wind-induced load capacity analysis and parametric study of a long-span steel arch bridge under construction

Wind-induced instability of long-span steel arch bridges is a serious engineering concern, particularly during construction. Using the Lupu Bridge with a main span length of 550-m as an example, this paper investigates the wind-induced load capacity of a long-span steel arch bridge during two construction stages I and II. Construction stage I is a maximum-cantilevered system before closure of main arch ribs. Construction stage II is a system in which all parts of the bridge have been completed except the stiffening girder of the main span. Three components of wind loads acting on both steel girder and arch ribs are considered in the analysis. The results show that the arch bridge at construction stage II is more susceptible to wind-induced instability than at construction stage I. Finally, various significant parameters affecting wind-induced load capacity are discussed.

NASAB: a finite element software for the nonlinear aerostatic stability analysis of cable-supported bridges

This paper presents the development and applications of the finite element software, NASAB, which can be used for linear, geometrically nonlinear, and materially nonlinear analyses of structure and nonlinear aerostatic stability analysis of cable-supported bridges. The software program consists of two main parts: a programming part and a computational part. The windows programming part written in FORTRAN90 was designed mainly to present the NASAB software in a user-friendly environment. The computational part was written in FORTRAN77. The use of FORTRAN77 is to effectively take advantage of existing codes, thus speeding up code design and implementation. The usefulness of FORTRAN programming language to develop a user-friendly interface including pre-processing and post-processing has been demonstrated by the present version of the software.