Design of composite hybrid plate girder bridges based on reliability and optimization

A practical and efficient reliability-based optimization approach to the design of both unstiffened and stiffened composite hybrid plate girders for highway bridges is presented. The steel weight of the built up plate girder is adopted as the objective to be minimized and all constraints specified in the AASHTO bridge code are considered in the optimization process. The solution is obtained by coupling an optimization program with a reliability analysis program. Numerical examples illustrate the application of the approach to reliability-based optimum design of unstiffened and stiffened composite plate girders. Sensitivity analyses are also performed for finding the rates of change of the optimum solution with respect to changes in problem preassigned parameters.     

Longitudinally stiffened hybrid steel plate girders subjected to patch loading

Hybrid girders subjected to patch loading have been analyzed in a detailed fashion for the case in which the plates that assemble the girders are transversally stiffened. Scant work, however, is available for the case in which the girders are hybrid and, simultaneously, longitudinally stiffened. The driving force for developing the present research work is to complete the knowledge of the patch loading field for the particular structural alternative of a hybrid steel plate girder assembled with a longitudinal stiffener. In the current paper, a numerical database of 255 simulations on longitudinally stiffened steel girders subjected to patch loading developed by the authors is presented. The results obtained are used for assessing the resistance of longitudinally stiffened hybrid steel plate girders subjected to patch loading. Some discrepancies between the numerical and EN1993-1-5 results are pinpointed. A design proposal which enhances the current EN1993-1-5 formulation is given at the end of the paper.     

Hybrid steel plate girders subjected to patch loading, Part 1: Numerical study

Extensive research focused on the structural behavior of hybrid steel plate girders is nowadays available in the literature. Furthermore, extensive research devoted to the resistance of homogeneous girders to patch loading has been performed in the last decades. Investigations dealing simultaneously with both fields are, however, rather scarce. The driving force behind developing the present research work has been the aim of completing the knowledge of the patch loading field for the particular structural alternative of hybrid steel plate girder. In the current paper, experimental results found in the literature as well as additional numerical simulations developed by the authors are summarized. The results presented can be used for assessing the resistance of hybrid steel plate girders subjected to patch loading. An in-depth exploit of such results is presented in a companion paper.     

Investigation on the Collapse Behavior of Diagonal Stiffened Composite Plate Girders Subjected to Shear Loading

In this study, a new analytical method is presented to estimate the shear capacity of diagonally stiffened steel–concrete composite plate girders. This method is formulated based on tension field action in steel girder web and failure mechanism of concrete slab deck. To validate the accuracy of the proposed method, the obtained results are compared with three-dimensional finite element analysis of composite plate girders with different configuration of stiffeners. The results of analytical and numerical investigations indicate that the proposed method can accurately estimate the ultimate shear capacity of composite plate girders. In addition, it is shown that the diagonal stiffeners on one hand can reduce the buckling effects of shear panel of girders and on the other hand can increase the strength of elastic shear buckling and ultimate shear capacity of girders well in comparison with the unstiffened thin steel plate girders.     

Imperfection sensitivity of plate girder webs subjected to patch loading

This paper is aimed at studying the influence of initial geometric imperfections on the postbuckling behavior of longitudinally stiffened plate girder webs subjected to patch loading. A sensitivity analysis is conducted herein using two approaches (deterministic and probabilistic) in order to investigate the effect of varying imperfection shape and amplitude on both, the postbuckling response and ultimate strength of plate girders under patch loading. This sensitivity analysis is performed by means of nonlinear finite element analysis. At first, the initial shape imperfections are modeled using the buckling mode shapes resulting from an eigenvalue buckling analysis. Thereafter, the amplitude of the buckling shapes for the various modes is varied, and then introduced in the nonlinear analysis. The results show the influence of these modes and amplitudes on the resistance to patch loading.     

An Approach to Preliminary Design of Precast Pretensioned Concrete Bridge Girders

Abstract: This paper presents an approach to the preliminary design of simple span precast pretensioned highway bridge girders using mathematical optimization methods. This type of bridge system is competitive for short and medium spans but also can accommodate long-span bridges if girder splicing and continuity are introduced. The bridge design problem is formulated as a nonlinear programming problem and is solved by the projected lagrangian algorithm. Several design objectives are investigated either separately or simultaneously with the aim of achieving cost-efficient bridge designs. The approach is used to generate a new set of five optimal girder sections and then to determine the girder spacing and span length capability of each precast girder. The five sections types (A, B, C, D, and E) proposed herein are more cost-effective than the corresponding Canadian standard sections because for similar depths they achieve greater span length and girder spacing while requiring less concrete and prestressing steel. This study also enables identification of the governing design requirements (serviceability and/or ultimate limit states active constraints) that may be adopted as optimality criteria when simplified preliminary designs of this bridge type for different design codes and girder sections are required.     

西堠门悬索桥分体式钢箱梁锚箱传力路径和疲劳性能分析

西堠门悬索桥吊索与分体式钢箱梁的连接,是通过在钢丝绳吊索端锚头上设置锚杯和叉形板,再由销轴将之分别与设置于两个钢箱梁翼端锚箱上的耳板插连来实现的。耳板整体穿过钢箱梁翼端倾斜表面,插入钢箱梁内,周边焊接。耳板两侧设置加劲板,箱内设置纵、横隔板,形成框式结构。对吊索和钢锚箱的索梁锚固部位足尺模型试验结果进行分析,研究吊索拉力的传力途径及耳板与锚箱构造的疲劳性能,进而分析吊索钢箱梁锚箱的可靠性和合理性。     

Computer-Aided Design of Prestressed Concrete Cellular Bridge Decks

Abstract: This paper illustrates the application of an effective optimization procedure for the design of prestressed concrete cellular bridge decks consisting of single- and two-cell box girders or voided slab systems. An approximate live load moment analysis using the finite-strip method and finite-difference techniques that determines moment sensitivities to changes in the deck depth and flange thickness is proposed for box girder decks. The optimization process is much simplified by eliminating the need of finite-strip reanalysis at each iteration. The optimal design is formulated as a nonlinear programming problem and solved by the projected lagrangian method. The resulting solutions may be used as preliminary designs for short- and medium-span highway bridges, for which cellular decks represent competitive solutions. Optimization results show that voided slab decks are more economical than box girder decks for the short span range and wide decks, and single-cell box girders are a cost-effective alternative for medium span range and narrow decks.     

Ultimate load behaviour of webs in steel-concrete composite plate girders

The paper is concerned with the tension field action in webs of steel-concrete composite plate girders. A three-dimensional finite element model has been used to carry out nonlinear analyses on composite plate girders. The results obtained from the finite element analyses are compared with those from experiments. It is observed from the comparative study that the proposed nonlinear finite element model is capable of predicting the ultimate load behaviour of steel-concrete composite plate girders to an acceptable accuracy. Results are presented to explain the development of the tension field action in the webs and to illustrate a measure of the contribution by the concrete slab acting compositely with the girder to the changes in tension field compared to a plain steel girder.     

Ultimate load behaviour of webs in steel–concrete composite plate girders

The paper is concerned with the tension field action in webs of steel–concrete composite plate girders. A three-dimensional finite element model has been used to carry out nonlinear analyses on composite plate girders. The results obtained from the finite element analyses are compared with those from experiments. It is observed from the comparative study that the proposed nonlinear finite element model is capable of predicting the ultimate load behaviour of steel–concrete composite plate girders to an acceptable accuracy. Results are presented to explain the development of the tension field action in the webs and to illustrate a measure of the contribution by the concrete slab acting compositely with the girder to the changes in tension field compared to a plain steel girder.     

Structural Health Monitoring in Incrementally Launched Steel Bridges: Patch Loading Phenomena Modeling

In this paper, a realistic nonlinear 3D simulation of an incrementally launched steel bridge girder is presented. The numerical simulation accounts for three sources of nonlinearity: geometry, material and boundary conditions. For the sake of depicting the capabilities of the presented numerical model in structural verifications, the study is focused on the patch loading field, a structurally complex phenomenon. Patch loading (or concentrated loading) is one of the most typically encountered structural verifications on incrementally launched steel I-girders. The presented realistic simulation is based upon an experimentally calibrated numerical model and may provide relevant information at both design and construction stages. For the former, the predictive capabilities of the model for inferring the potential failure due to patch loading are depicted. For the latter, the results obtained are displayed in a way that may be useful for planning a Structural Health Monitoring (SHM) deployment aimed at controlling the patch loading-related phenomena in incrementally launched steel plate girders.     

钢筋混凝土曲线箱梁非线性分析

本文使用分层退化壳单元对钢筋混凝土曲线箱梁弯曲、扭转时的材料和几何非线性行为进行了研究,总结出了钢筋混凝土曲线箱梁非线性荷载-位移曲线的变化规律.从计算结果的比较分析中,总结出了用分层板(壳)单元分析钢筋混凝土曲线箱梁时经济、合理的分层数目.     

波浪腹板工形梁局部承压承载力设计方法研究

波浪腹板工形梁的局部承压性能目前国内外研究较少。在总结前人对平腹板和梯形波折腹板梁局部承压极限承载力研究工作的基础上,对波浪腹板工形梁的局部承压性能及设计方法进行研究。通过有限元数值分析,揭示波浪腹板工形梁在局部压力作用下的破坏形式以及腹板几何初始缺陷对局部承压性能的影响,在几何参数分析的基础上建立局部承压极限承载力的简化计算公式。最后针对同时承受局部荷载和弯矩的波浪腹板工形梁,建立截面弯矩与局部压力之间的M-P承载力相关计算公式,并通过有限元数值计算进行验证。     

Transversally stiffened plate girders subjected to patch loading. Part 1. Preliminary study

In this paper, an experimental programme of six steel plate girders subjected to patch loading as well as results of forty eight numerically-tested prototypes are presented. Results of ultimate load capacity as well as structural responses from these girders are provided. In addition, experimental and numerical values of ultimate load capacity are compared with those predicted by EN1993-1–5. With such results, the response of transversally stiffened steel plate girders is discussed throughout the paper. Particular emphasis is given to the influence of the transverse stiffening on the ultimate load capacity of the girders. It is observed that girders with largely spaced transverse stiffeners present a considerably different response from girders with closely spaced transverse stiffeners. The structural response for the former case has been thoroughly studied in the last decades whereas little attention has been paid for the latter. Further analysis of this particular topic is provided in a companion paper.     

Incorporation of corrosion effects in reliability-based optimization of composite hybrid plate girders

Available data suggest that corrosion may have significant effects on the reliability of structural components and systems including highway bridges, offshore platforms, and hydraulic structures. Therefore, reliability-based design and/or optimization of a structure or component placed during its intended service life in a corrosive environment must take the effects of this environment into account. A reliability-based optimization approach to the design of composite hybrid plate girders under corrosion effects is developed herein. The proposed approach incorporates all constraints specified in the AASHTO bridge code considering time-dependent corrosion effects. Numerical examples illustrate the application of the proposed approach to time-dependent reliability-based optimum design of both unstiffened and stiffened composite hybrid plate girders for highway bridges.     

波形钢腹板PC组合箱梁抗扭性能试验

通过试验的方法,研究波形钢腹板PC组合箱梁在偏心荷载作用下,挠度、横向位移、刚性扭转角、箱梁截面的翘曲应变、翘曲应力及波形钢腹板的附加剪应力的分布规律,以了解悬臂波形钢腹板PC组合箱梁在扭转作用下的力学性能。研究表明:波形钢腹板翘曲应变很小,可忽略不计;翘曲应力在底板上呈现明显的直线分布规律,且最大值出现在底板的角点处;波形钢腹板上的剪应力分布较均匀,附加剪应力在腹板上的分布也有类似的规律。     

Nonlinear finite element method models for ultimate strength analysis of steel stiffened-plate structures under combined biaxial compression and lateral pressure actions—Part II: Stiffened panels

The present paper (Part II) is a sequel to the previous paper (Part I) [Paik JK, Seo JK. Nonlinear finite element method models for ultimate strength analysis of steel stiffened-plate structures under combined biaxial compression and lateral pressure actions—Part I: Plate elements. Thin-Walled Struct 2008, this issue, doi:10.1016/j.tws.2008.08.005.] on the application of nonlinear finite element methods for ultimate strength analysis of steel stiffened-plate structures under combined biaxial compression and lateral pressure actions. In contrast to Part I dealing with plate elements, the present paper (Part II) treats stiffened panels surrounded by strong support members such as longitudinal girders and transverse frames. In similar to Part I, some important factors of influence such as structural dimensions, initial imperfections, loading types and computational techniques in association with ultimate limit states are studied. Some useful insights in terms of nonlinear finite element method modeling are developed using ANSYS code together with the ALPS/ULSAP semi-analytical method, the latter being for the purpose of a comparison.     

Experimental and Numerical Study on Buckling Behavior of a Rigidly Stiffened Plate with Tee Ribs

In the bridge structures, stiffened plates are usually designed as rigidly stiffened when the orthotropic steel box girder is used as the main load-bearing structure. Therefore, the buckling mode of stiffened plates is plate buckling which occurs in subpanel supported by stiffeners. The orthotropic steel box girder is used as the main girder for Egongyan Rail Special Bridge, which is a self-anchored suspension bridge. Plates of the steel girder are rigidly stiffened with unequal spacing open ribs, and the most slender stiffened plate is the mid web stiffened with Tee ribs. In order to ensure the safety of the bridge, the buckling behavior of the web and orthotropic steel box girder under axial compression, including ultimate strength, post-buckling behavior and failure modes, should be clearly investigated by experimental and numerical methods. The design, loading and testing methods of the 1:4 scale model of the orthotropic steel box girder are introduced in detail firstly. The orthotropic steel box girder and the stiffened web finite element (FE) models are validated by the test results, and the effects of residual stress and the magnitude of geometric imperfections are discussed roughly. Based on the validated web FE model, a detailed parametric study is performed to systematically investigate the effects of residual stress and geometric imperfections on buckling behavior of the web. The effect of shapes of geometric imperfections discussed is highlighted. Through tracing stress states, the failure modes of stiffened plate are in agreement with the experimental phenomenon to some extent. Results show that shapes of geometric imperfections have significantly influenced post-buckling behavior and failure modes of the web, but slightly affected the ultimate strength. It is advised that residual stress and geometric imperfections should be controlled to make full use of excellent performance of steel materials.     

Wet concrete loading of profiled trough girders

Profiled trough girders act as the permanent formwork for reinforced concrete beams, and form a member known as a composite profiled beam. During the construction phase, the pouring of wet concrete may influence the strength and stiffness of the profiled girder. The method of profiled composite construction is thus described herein and the influence of the wet concrete loading of profiled trough girders is studied. A series of three profiled trough girders were tested under wet concrete loads, and their deformations were monitored. A folded plate finite element method is then developed to model the in-plane and out-of-plane deformations that the trough wall is subjected to during this wet concrete loading.     

Der Einfluss von Zwischenhölzern auf das Biegedrillknickverhalten zweiteiliger Brettschichtholzträger

The influence of intermediate links on the lateral torsional buckling of two‐part glued laminated girders. The lateral torsional buckling behaviour of two‐part laminated girders can be influenced very advantageously by means of intermediate links. The reason for it represents mainly the shearing connecting of the two elements in their longitudinal direction. Furthermore the intermediate links cause an elastic torsional coupling which is the reason why the lateral torsional buckling of the single parts of the girder also is determined by vertical displacements besides the usual torsions and horizontal displacements which require further deformation energy. In this paper the bifurcation loads are determined for a girder with different types of the intermediate links by means of a finite element analysis. In addition nonlinear elasticity calculations according to theory of second order are carried out to get the forces and moments of the links. The results of the investigations demonstrate that connections between the two parts of the girder are the reason that the buckling loads rise significantly. The arithmetical consideration of the connections at the supports alone shows already very positive consequences on the buckling behaviour of the girder.