Jian-Jing Jiang

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.

BOND-SLIP MODELS FOR FRP SHEET/PLATE-TO-CONCRETE INTERFACES

A meso-scale finite element model is first presented for simulating the debonding behavior of FRP-to-concrete bonded joints in simple shear tests. In this model, both the FRP plate/sheet and the concrete are modeled using elements of mesoscopic sizes so that the shapes and paths of cracks during the entire debonding process can be appropriately captured. Results obtained from this model are next presented to provide insight into the debonding failure process. Finally, based on a finite element parametric study and existing test results, three bond-slip models of different levels of sophistication are presented. These proposed models are far more accurate than all existing bond-slip models.

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.

Nonlinear FE Model for RC Shear Walls Based on Multi-Layer Shell Element and Micro-Plane Constitutive Model

Nonlinear simulations for structures under disasters have been widely focused in recent years. However, precise modeling for the nonlinear behavior of reinforced concrete (RC) shear walls, which are the major lateral-force-resistant structural member in high-rise buildings, still has not been successfully solved. In this paper, based on the principles of composite material mechanics, a multi-layer shell element model is proposed to simulate the coupled in-plane/out-plane bending or the coupled bending/shear nonlinear behaviors of RC shear wall. The multi-layer shell element is made up of many layers with different thickness. And different material models (concrete or steel) are assigned to various layers so that the structural performance of the shear wall can be directly connected with the material constitutive law. And besides the traditional elasto-plastic-fracture constitutive model for concrete, which is efficient but does not give satisfying performance for concrete under complicated stress condition, a novel concrete constitutive model, referred as micro-plane model, which is originally proposed by Bazant et al., is developed to provide a better simulation for concrete in shear wall under complicated stress conditions and stress histories. Three 10-story buildings under static push-over load and dynamic seismic load, with various shear wall arrangements, were analyzed with the shear wall model proposed in this study. The simulation results show that the multi-layer shell elements can correctly simulate the coupled in-plane/out-plane bending failure for tall walls and the coupled in-plane bending-shear failure for short walls. And with micro-plane concrete constitutive law, the cycle behavior and the damage accumulation of shear wall can be precisely modeled, which is very important for the performance-based design of structures under disaster loads.

Advanced aerostatic stability analysis of cable-stayed bridges using finite-element method

Based on the concept of limit point instability, an advanced nonlinear finite-element method that can be used to analyze the aerostatic stability of cable-stayed bridges is proposed. Both geometric nonlinearity and three components of wind loads are considered in this method. The example bridge is the second Santou Bay cable-stayed bridge with a main span length of 518 m built in China. Aerostatic stability of the example bridge is investigated using linear and proposed methods. The effect of pitch moment coefficient on the aerostatic stability of the bridge has been studied. The results show that the aerostatic instability analyses of cable-stayed bridges based on the linear method considerably overestimate the wind-resisting capacity of cable-stayed bridges. The proposed method is highly accurate and efficient. Pitch moment coefficient has a major effect on the aerostatic stability of cable-stayed bridges. Finally, the aerostatic failure mechanism of cable-stayed bridges is explained by tracing aerostatic instability path.

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.

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.

Three-Dimensional Stress and Stress Intensity for Tensioned Flat Plates with Edge Cracks

Abstract The stress in the thickness direction is an important factor influencing the fracture behavior of structural members. A stress σ y tensioned flat plate with edge cracks is widely used as an analysis model. The stresses σ x and σ y for the plate model can be acquired from Neubers solution. However, the solution is applicable only for a perfect plane stress or plane strain state. As a consequence of the thickness of the plate a three-dimensional (3-D) stress state will arise near the crack tip, resulting in a variation of the distribution of σ x and σ y stresses. A full analysis for the 3-D stress fields for a tensioned flat plate with edge cracks has been therefore carried out. The results show that the 3-D stress field near the crack tip is mainly determined by two factors: the thickness of the plate and the curvature radius at the crack tip. A further analysis has been carried out for the stress intensity near the crack tip. In this paper we give some equations matching to the 3-D stress and stress intensity, which describe precisely the stress state near the crack tip, and which can be applied effectively in engineering analysis.