Girder Web Research Articles

Evaluation of novel combined CFRP-steel retrofit for repairing distortion-induced fatigue

Distortion-induced fatigue damage at crossframe-to girder connections affects many steel bridges built before the mid-1980s. This type of damage is associated with a prevalent detailing practice at the time which avoided welding connection plates to girder flanges to avoid fatigue cracks. The lack of connectivity and out-of-plane motion of the crossframe produce a flexible gap region in the girder web where fatigue cracks often develop, requiring frequent inspections, costly maintenance, and repairs.This paper presents a study evaluating the use of CFRP in conjunction with steel sections to repair complex patterns of distortion-induced fatigue cracks in steel bridge web gaps, without the need for bolting to the flange or concrete deck removal. A steel girder-to-crossframe subassembly was tested in distortion-induced fatigue to evaluate the performance of the retrofit measure. Realistic crack patterns were introduced by applying fatigue loading, and the efficacy of the repair method was evaluated by monitoring crack growth with the repair in place. Twelve test trials were performed: five in the unretrofitted condition to propagate the cracks, and seven in the retrofitted condition to evaluate performance of the repair. The study evaluated multiple crack patterns, different configurations of the retrofit, presence or absence of mechanical anchorage to the flange, footprint of the CFRP relative to the steel retrofit elements, and different surfaces connected by the CFRP.The results showed that the combined CFRP-steel retrofit measure was effective in preventing distortion-induced fatigue crack initiation and propagation.

Web shear buckling of steel–concrete composite girders in negative-moment regions

Steel–concrete composite girder webs used to connect flanges in bridges are generally slender, which introduces stability problems. The assumption in existing codes that the web is simply supported on four sides is excessively conservative and unreasonable. In this study, web shear buckling of steel–concrete composite girders in negative-moment regions were experimentally and numerically investigated. The failure modes, shear-buckling loads, and ultimate loads of the specimens were analysed. Based on the surface strain and out-of-plane deflection of the web, the web shear-buckling load was determined and compared with the theoretical results. A three-dimensional non-linear finite element model is developed and validated based on the experimental results. Using the validated numerical model, the elastic shear-buckling behaviour of the webs of composite girders under actual boundary conditions were investigated. The numerical results showed that the boundary conditions of the composite girder web can be regarded as simply supported on two opposite edges, fixed on one edge, and restrained by the bottom flange on one edge. A formula for calculating the web shear-buckling coefficient of composite girders was proposed based on the numerical results.

Bending characteristics of composite box girder considering all surfaces shear deformation based on Hamiltonian system

The composite box girder does not satisfy the assumption of flat section in the actual force behavior. The transverse force generated by the bending is transmitted to the shear key through the web, and then transmitted to the wing plate by the shear key. The shear deformation of the channel steel box girder web makes the shear stress of the composite box girder section unevenly distributed on the wing plate. The selection of displacement function caused by shear deformation is often unclear in physical meaning, and analysis and verification that conform to the actual deformation and stress distribution law of the structure are rarely carried out. Aiming at this problem, a microplate shear flow analysis method is proposed. Considering the influence of shear deformation, the shear lag warping displacement function of the composite beam is derived, and the displacement function is corrected according to the self-balance condition of the warping normal stress, which makes up for the defect of the unclear physical meaning of the displacement function. On the problem of solving the control differential equations. For the first time, it is proposed to use Hamiltonian theory to solve the problem, which avoids the problem of solving high-order differential equations in the classical elasticity solving method and the functional variational method based on the energy principle. The stress distribution of the composite box girder under the action of concentrated load and uniform load is analyzed.

Application of a digital image correlation bridge inspection methodology on geometrically complex bifurcated distortion‐induced fatigue cracking

AbstractDistortion‐induced fatigue cracking is a concern for many aging steel bridges in the United States. Human visual inspections to characterize fatigue cracks have many drawbacks including inconsistencies in identification, significant time and monetary costs, and safety risks posed to the lives of both inspectors and the traveling public due to lane closures. Digital image correlation (DIC) is a vision‐based technology which has shown promise for identifying and characterizing fatigue cracks. Three‐dimensional DIC measurements can capture full‐field displacements and strains, allowing for detection and characterization of both in‐plane and distortion‐induced fatigue cracks. This paper describes an experimental study in which a half‐scale steel girder to crossframe subassembly was subjected to distortion‐induced fatigue loading to produce multiple geometrically complex cracks. A DIC‐based crack characterization methodology was applied to quantify the cracks, which was successful at characterizing cracks propagating in the girder web but struggled to characterize horizontal cracks. Additional work is needed to improve the accuracy of the DIC‐based crack characterization methodology to use as an automated bridge inspection tool.

Panting Fatigue of Trapezoidal Corrugated Steel Webs with Mixed-Mode Cracks

Trapezoidal corrugated steel webs under panting fatigue are represented by repeated cyclical out-of-plane deflections of their subpanel with mixed-mode cracks. Compared to stiffened flat webs, notable fatigue crack formation could take place along with local deflection. Fatigue tests were conducted for nine composite girders with slender webs and varied corrugation dimensions. Nearly all test girders showed notable local and interactive shear buckling at the corrugated web panel and the panting fatigue cracks are formed under repeated cyclical deflection while the compression and tension flanges remain intact. Fatigue cracks are initiated at the junction between the vertical (longer) edge of the subpanel and the boundary of the out-of-plane deflection region. The crack propagation paths appear to deviate from the original vertical edge due to buckling induced out-of-plane deflection under mixed-mode stress condition. The test results demonstrate that the Category B’ and Category E suggested by the AASHTO LRFD bridge fatigue design provisions related to the principal stress range and the nominal membrane shear stress range respectively can be considered for the prediction of the fatigue life of trapezoidal Corrugated steel webs in test girders. An appropriate allowance of both the shear stress along the vertical web edge and tension stress from the diagonal plastified tension band is given for the mixed-mode stress intensity factor. The proposed fatigue life prediction allowing for mixed-mode crack growth mostly compares well with test results and its further improvement for the case with higher web panel slenderness ratio is discussed.

Side-Surface Openings Effect on Aerodynamic Performance of Box Girders in Tandem

Abstract A butterfly web girder is a box girder that has discretely distributed side-surface openings. Due to these openings, butterfly web girders show better aerodynamic performance than conventi...

Shear Lag and Local Buckling Interaction in Orthotropic Deck of Steel Bridges

Abstract The term of shear lag is related to the discrepancies between the approximate theory of the bending of beams and their real behaviour, and it refers to the increases of the bending stresses near the flange-to-web junctions, and the corresponding decreases in the flange stresses away from these junctions. In the case of wide flanges of plated structures, shear lag caused by shear strains, which are neglected in the conventional theory, may be taken into account by a reduced flange width concentrated along the webs of the steel girders. The effects of the shear lag, plate buckling and interaction of both effects should be taken into account at the ultimate, serviceability or fatigue limit states in the design of structures with wide flanges. In EN 1993-1-5, the concept of taking shear lag into account is based on the effectives width of the flange which is defined in order to have the same total normal force in the gross flange subjected to the real transverse stress distribution as the effective flange subjected to a uniform stress. Some aspects concerning the shear lag phenomenon and a design example of effectives width calculation and the shear lag effects for a steel pedestrian bridge deck are presented in this paper.

The ultimate shear capacity of longitudinally stiffened steel-concrete composite plate girders

This paper presents the ultimate shear strength of longitudinally stiffened steel-concrete composite plate girders (LS-CPGs) under shear loading. The tension field action in the girder web, shear capacity of concrete slab, and the position of longitudinal stiffeners are considered in driving an analytical method to predict the ultimate shear strength of the girder. The accuracy of the proposed method is evaluated by finite-element (FE) models. A three-dimensional FE model has been generated, considering both the geometric and material nonlinearity of LS-CPGs. The results show that longitudinal stiffeners increase the ultimate shear strength of LS-CPG. The comparison between the analytical and corresponding FE results shows that the proposed analytical method can accurately predict the ultimate shear strength of LS-CPGs.

NUMERICAL STUDY OF FLANGE BUCKLING BEHAVIOR OF HIGH-STRENGTH STEEL CORRUGATED WEB I-GIRDERS

Steel plate girders with trapezoidal corrugated webs (TCWPGs) have been used over the last years around the world in many roadway and railway steel bridges as they can introduce several important advantages compared to flat web plate girders. The proper design of corrugated web girders depends mainly on the flexural and shear capacity of them. However, the flexural capacity is more important. Also, not many researchers studied the flexural capacity of such girders especially, when flange local buckling failure type (FLB) occurs in these corrugated web girders. In this paper, the flange local buckling behavior of steel trapezoidal corrugated web girders built up from high-strength steel (HSS) plates has been investigated to get the advantages of both the technique of corrugated web plates (CWPs) and the high-strength steel material (HSSs) together. A new numerical parametric study on four important parameters has been carried out to explain and investigate the flange local buckling behavior of high-strength steel corrugated web girders, considering mainly the influences of the flange to web thickness ratio, unsupported length of the compression flange, the corrugation angle and the initial imperfection magnitude of the compression flange on the behavior of girders with corrugated webs built up from HSSs. Using the commonly used finite element software ABAQUS, the results of the FE models have been obtained to be analyzed and discussed. Finally, some important advices have been introduced to aid the structural engineers to design such girders under flexural loading in economical manner.

On the out-of-plane stiffness of I-section girders with corrugated webs using elastic finite element analyses

Corrugated web girders (CWGs), nowadays, are widely used as bridge girders all over the world thanks to their superior shear resistance compared to I-girders with transversely-stiffened flat webs (IPGs). Additionally, it has been recently found that the out-of-plane stiffness of CWGs increases their lateral-torsional buckling resistance. However, based on the authors' experience, the literature does not contain a calculation method which ensures that the out-of-plane stiffness of CWGs is higher than that of IPGs. Accordingly, this paper is devoted to provide such method for design purpose. This investigation is based on the elastic buckling analyses of CWGs, by using ABAQUS solver, which provide the critical finite element (FE) strengths. Then, two critical moment predictions are calculated; the first one uses the method derived by Moon, et al. (2009), whereas the other one is that calculated typically for IPGs. While the first considers an enhanced warping constant due to the corrugations, the later does not. From the comparisons, the strengths considering the prediction of Moon, et al. (2009) are found to represent well FE strengths in some cases; meaning that the out-of-plane stiffness of CWG is higher than that of its equivalent IPG. Accordingly, the contribution of CW in the warping constant is divided by that of the entire cross-section of IPGs to find the effective ratio that yields higher out-of-plane stiffness for CWGs compared to IPGs. Based on these statistics, a condition is put forward which ensures that CWGs own higher out-of-plane stiffness. This paper proves that CWGs do not always have higher out-of-plane stiffness compared to their equivalent IPGs, but ensuring this requires to link the dimensions of CW, especially the value of corrugation depth, with the flange width.

An analytical method to assess the structural responses of ship side structures by raked bow under oblique collision scenarios

With the development of the shipping industry, the number of ships at sea has increased significantly. According to the statistical data, oblique ship collisions are much more frequently happened than that of head-on ship collisions. However, there are less researches on oblique ship collisions than those of head-on ship collisions. The responses of hull structure during oblique collision scenarios are different from those in head-on collision scenarios, and might have wider structural damages, which demonstrate the significance of research on oblique collision scenarios and structural damage. In this paper, the oblique collision scenarios are firstly investigated through numerical simulations. Finite element software LS_DYNA is used for the numerical simulations. Six typical oblique collision scenarios are defined, on purpose of finding the main deformation characteristics of the struck ship. Two basic assumptions were made accordingly. Then, a simplified analytical method is proposed to predict the structural response of ship side structures by raked bow under oblique collision scenarios. The new analytical method includes the deformation mechanism of the side plating, the web girder and the transverse frame. The resistance and energy dissipation of these components are used in an integrated way to evaluate the overall crashworthiness of the side structure of the struck ship. The numerical simulation results match well with the results of analytical calculations, which validates the accuracy of the proposed analytical method. The proposed analytical method can provide an effective way to evaluate the structural crashworthiness of ship side structures in oblique collision scenarios during the structural design stage.

Effects of Shear Lag in Steel Box Girders of a Crane Runway

Abstract The term of shear lag is related to the discrepancies between the approximate theory of the bending of beams and their real behaviour. It refers to the increases of the bending stresses near the flange-to-web junctions and the corresponding decreases in the flange stresses away from these junctions. In the case of wide flanges of plated structures, shear lag caused by shear strains, which are neglected in the conventional theory, may be taken into account by a reduced flange width concentrated along the webs of the steel girders. In EN 1993-1-5, the concept of taking shear lag into account is based on effective width of the flange which is defined in order to have the same total normal force in the gross flange subjected to the real transverse stress distribution as the effective flange subjected to a uniform stress equal to the maximum stress of the real transverse distribution. Some aspects concerning the shear lag phenomenon and a working example for a box girder of a heavy crane runway to illustrate the determination of the shear lag effect are also presented.

Flange-induced buckling of plate girders of high strength steel

Design practice shows that the simple web slenderness limit given in EN 1993-1-5 to prevent flange-induced buckling does not usually govern the web design other than for very slenderness class 4 plate girder webs in steel grades S235 to S355. However, the same formula applied to plate girders designed in S690 or S700 high strength steel (HSS) gives much lower slenderness limits that can govern web design and restrains the possibilities for reducing their thickness to profit from the high steel resistance. This paper reviews the background of the simplified web slenderness limit currently used. The results obtained with this formula are compared with numerical results from full non-linear analysis of steel and steel-concrete composite girders that present different buckling modes of the web. The case of hybrid plate girders adopting HSS only on the flanges and the possible benefits of transverse stiffeners are also investigated.

Strength evaluation of deteriorated girder ends. I: Experimental study on naturally corroded I-beams

Corrosion is a common cause for steel bridge deterioration, primarily attributed to malfunctioning deck expansion joints. Aged joints fail to prevent water or deicing mixtures from penetrating into the bearing area triggering a corrosive process which locally damages the steel beams. Topologically non-uniform and highly uncertain, the appearance of corrosion makes the residual bearing capacity quite challenging to be accurately assessed by inspectors and engineers. The present study, the first part of a companion set of two papers, aims to evaluate and improve the efficiency of current strength assessment policies for un-stiffened rolled I-beams, based on field corroded girders tested in the laboratory. A total of six full scale loading tests are reported on naturally corroded girders, which were extracted from structurally deficient bridges in the state of Massachusetts. The test results indicate that provisions underestimate the capacities of five out of the six specimens, while the sixth test highlights the harmful effect of a web's deviation from plumbness. An alternative load path is also revealed for specimens with holes extending along the bottom at the girder web.

Stress states and shear failure mechanisms of girders with corrugated steel webs

The corrugated steel web girder (CSWG) has been widely used since its light self-weight and high shear stability. Previous studies on the shear response focus on the shear buckling behavior of corrugated steel webs that dominates shear strength of the girder. However, there is a lack of theoretical explanation for this phenomenon. Besides, research on the post-buckling performance of CSGBs is quite limited though that has been observed by several researchers. In this paper, a theoretical approach adopting the rotated stress field method was proposed to analyze stress states in girders with corrugated steel webs under shear and was verified by experimental data. The results could explain the shear strength determined by shear buckling behaviour theoretically. Then, nonlinear finite element analyses were performed on 24 I-beam specimens to investigate the post-buckling performance and ultimate failure mechanisms of the CSWG. The post-buckling performance is provided by a frame system composing the tension zone in the web, the flanges and the stiffeners. When plastic hinges form in the flanges, the girder collapses and the possible collapse mechanisms include the quasi mid-section mechanism, the mid-section mechanism and the girder mechanism. Level of the residual shear strength after buckling and the collapse mechanism are significantly affected by the flange bending stiffness and the web width/height ratio.

Influence of patch load length on resistance of I-girders. Part-I: Experimental research

Problem of behaviour and ultimate strength of the centrically patch-loaded steel I-girders without longitudinal stiffeners and with largely spaced transverse stiffeners is analysed. The research is focused on two parameters - load length and initial geometrical imperfections of a girder web. This paper presents the experimental research, while the companion paper includes a numerical analysis of the problem.The experimental campaign is described in detail. Results, comments and conclusions from seven tests are presented. The observed increase of the ultimate strength with the load length increase is not quantified due to the scatter of results which is typical for all previous experimental studies in this field. The scatter of results is a consequence of the intricate initial geometrical imperfections of the web which were measured on the most of the specimens. Following conclusions from the experimental research are used in the companion paper to develop reliable numerical models of the experimentally tested girders. It is necessary to model in detail the contact between load block and loaded flange, to account for the variation of contact pressure during the load application. The initial geometrical imperfections of the web in the load introduction zone have more significant influence on the development of lateral web deformation and thereof the ultimate strength, compared to the web imperfections adjacent to the unloaded flange.Finally, based on the performed experimental research, the companion paper presents a detailed parametric numerical analysis of the problem and proposes a correction factor for the load length.

Optimisation of Trapezoidal Corrugated Plate Girder

Trapezoidal Corrugated web girders is a newly developed structural design. The major advantage of such design of web is that the corrugated webs enhance the stability of beam against buckling, which results in a very economical design by the reduction in the use of web stiffeners. The flanges are made up of flat plates and welded to the trapezoidal web sheet with the modern manufacturing process and modern advance welding technology. The flanges are mainly used to provide flexural strength to the beam and web are used to increase the shear capacity of the beam. Main reason for the failure of the web is the steel yielding or web buckling. Other possible failure reasons are lateral torsional buckling of the girder and local flange buckling, separately or in combination. This paper presents a new technological solution of such a system, composed by web made of trapezoidal shape. The buckling strength of the girder is studied under different geometrical modifications performing a nonlinear finite element analysis in ANSYS.

Performance of Steel Plate Girders with Inclined Stiffeners

Slender webs in steel plate girders are prone to local and shear buckling at relatively low shear and thus, need be stiffened to increase the strength and stability of the girders. The conventional way is to provide vertical stiffeners at specified intervals, but this practice serves only to prevent the buckling of web. Provision of inclined stiffeners, in addition to improving buckling resistance, forms a truss-like girder which allows those stiffeners to carry some percentages of forces exerted in the girder. This paper, therefore, presents the ultimate performance of thin-webbed plate girders containing inclined stiffeners. Five simply supported plate girders of practical size were tested to failure under concentrated load applied at the mid-span. This study focuses on the effects of different inclination angles of intermediate stiffeners, 𝜃 on the load carrying capacity and post-buckling behaviour. Five different inclination angles, viz., 90°, 75°, 60°, 45° and 30°, measured from the bottom flange, were accounted for in the test series. Considerable variations of strength, failure characteristic and load-deflection response can be observed due to effects of such inclinations. Test results have shown significant increases in the ultimate strength from 11% to the extent of 50% as the angle of inclined stiffeners reduced. All the girders exhibited shear-dominated behaviour in the web panels at failure.

A Generalized Formula for Elastic Shear Buckling of Trapezoidal Corrugated Web Girder

Trapezoidal corrugated web girder is widely used. The elastic shear buckling stress is an important parameter in the design and calculation of trapezoidal corrugated web girder. Accordingly, much research has been devoted on the analysis of typical elastic global shear buckling, elastic local buckling and elastic interactive shear buckling, and the corresponding formulae existing in a variety of literature. The results of finite element analysis suggest that there is a certain deviation in the calculated values based on classical elastic shear buckling formulae. The boundary conditions of corrugated web play an important role in the calculation of elastic shear buckling. And it is found that the shear buckling modes of the actual trapezoidal corrugated web may be called the atypical buckling, which is different from typical local buckling, global buckling and interactive buckling. The existence of the atypical buckling may result in some calculation deviations for the existing formulae of elastic shear buckling. Based on the classical elastic shear buckling formulae, a generalized formula for elastic shear buckling of trapezoidal corrugated web girder is obtained by numerical simulation. It intuitively reflects the relationships among various buckling modes. The formula has high calculation reference value and will promote the research of elastic shear buckling of trapezoidal corrugated web girder.

Assessment of the suitability of eurocode design model for corrugated web girders with slender flanges

Currently, corrugated web girders (CWGs) are important structural components in bridges. Besides, they act as crane carrying girders and extensively as frame members. Despite that considerable improvement has been made in the last decade in understanding the flexural response of CWGs, the effect of using slender flanges has been limited. In the literature, the beams are too short to exhibit the lateral-torsional buckling (LTB) mode, and they merely focus on the local buckling (FLB) of the flanges. Accordingly, this paper focuses on the influence of slender flanges on the LTB behaviour of CWGs, with the main goal of assessing the suitability of the current EC3 design model. Currently, these girders have been examined through numerical modelling with the aid of ABAQUS software. Firstly, the numerical models have been carefully validated. Then, parametric studies have been carried out considering the influences of the material grade besides the cross-sectional dimensions on the structural response of CWGs that act as crane carrying girders or frame components. The results show that FLB might be accompanied by a slight LTB in intermediate-length girders, while FLB and LTB take place in short and long girders, respectively. The strengths of the current girders have been checked against the predictions of EC3 and it is found that it should be enhanced for the efficient design of such girders. Therefore, a modification has been proposed for such design model, which has shown to provide better strengths compared with numerical and available test strengths which in turn provides weight savings. Additionally, several conclusions have been presented to structural engineers to help in designing efficient cross-sections.