Plate Girder Web Panels Research Articles

Experimental Testing of Shear Web Panels of Steel Plate Girders Strengthened by Fiber-Reinforced Polymer Composites

Experimental Testing of Shear Web Panels of Steel Plate Girders Strengthened by Fiber-Reinforced Polymer Composites

Formation of post-buckling shear mechanisms in stiffened web panels of slender steel plate girders

A series of validated finite element models are used to investigate the formation of mechanisms in stiffened slender web panels of steel plate girders under pure shear. The prototype girder is based on the seminal tests by Basler and has a web slenderness of 267. Six model cases are analyzed with variations in web panel aspect ratio (1, 1.5, and 3), steel yield strength (Grades 36 and 50), initial imperfection magnitude, and flange thickness. When loaded in shear, the web panels exhibit a 3-stage response: (1) elastic behavior, (2) web mechanism formation, and (3) panel mechanism. In Stage 1, the web initially exhibits an elastic in-plane shear response with no distinct buckling bifurcation. During this stage, the web’s initial out-of-plane imperfections become engaged in second-order bending along its compression diagonal. Concurrently, tension develops in the opposite diagonal as a non-uniform membrane stress field, with highest intensities at locations where second-order bending is low. In Stage 2, a web mechanism is formed when connected bands of thru-thickness von Mises yielding develop across the tension diagonal. These bands emerge at locations where tension membrane stresses interact with locations of maximum second-order bending stress in the buckled shape. The shear load at the end of web mechanism formation is recommended as a target for plastic limit state design because it marks a significant decrease in shear stiffness. In Stage 3, von Mises yielding continues to saturate the web panel, and the bounding flanges and transverse stiffeners become increasingly engaged in load redistribution from the plastified web. Any hardening increase in shear resistance during the panel mechanism stage is modest in magnitude (up to ∼10% for some cases in this study) and is heavily dependent on the sizing of the flanges and stiffeners to carry redistributed forces.

Interpretable soft computing predictions of elastic shear buckling in tapered steel plate girders

The complexity of the shear buckling in tapered plate girders has motivated researchers to conduct experimental and numerical investigations to understand the underlying mechanisms controlling such phenomenon, and subsequently develop related design-oriented expressions. However, existing predictive models have been developed and validated using limited datasets and/or traditional regression techniques—restricting both the model utility, when considering a wider range of design parameters, and the model generalizability, due to associated uncertainties. To address these issues, the present study employed a powerful soft computing technique—multi-gene genetic programming (MGGP), to develop design expressions to predict the elastic shear buckling strength of tapered end plate girder web panels. A dataset of 427 experimental and experimentally validated numerical results was used in training, validating, and testing the developed MGGP models. Guided by mechanics and findings from previous studies, the key parameters controlling the strength were identified, and MGGP were employed to reveal the interdependence between such parameters and subsequently develop interpretable predictive models. The prediction accuracy of the developed models was evaluated against that of other existing models using various statistical measures. Several filter and embedded variable importance techniques were used to rank the model input parameters according to their significance in predicting the elastic shear buckling strength. These techniques include the variable importance random forest and the relative influence gradient boosting techniques. Moreover, partial dependence plots were employed to explore the effect of the input variables on the strength. The results obtained from this study demonstrated the robustness of the developed MGGP expression for predicting the elastic shear buckling strength of tapered plate girder end web panel. The developed model also exhibited a superior prediction accuracy and generalizability compared to currently existing ones. Furthermore, the developed partial dependence plots facilitated interpreting the influence of all input variables on the predicted elastic shear buckling strength.

Numerical investigation on ultimate shear strength of long steel plate girder web panels at high temperatures

In this article, elastic shear buckling and ultimate shear strength of long steel plate girder web panels subjected to pure shear loading are investigated at both ambient and elevated temperatures by the finite element method (FEM). Ninety-six plate girders with compact, non-compact and slender long web panels are numerically analyzed and compared. From linear eigenvalue analysis, it is shown that AISC 360-16 predictions are more conservative than FEM results such that the difference is about 40% for all ranges of web panel slenderness. According to nonlinear analysis results at ambient temperature, there must be reduction factors applied to AISC 360-16 non-conservative predictions for considering the strength degradation caused by large slenderness values and effects due to initial geometrical imperfection. Furthermore, it is observed that the adopted equation of AISC 360-16 for fire situations yields values that are more non-conservative such that the difference reaches almost 18%. In this regard, the FEM results are used to develop a new equation for predicting the ultimate shear strength of long web panels by taking into account strength degradation caused by large slenderness values, high temperature and initial geometrical imperfections.

Shear design curves of unstiffened plate girder web panels at high temperatures

Owing to the lack of an analytical research on the evaluation of mode change of web panels in addition to the need for shear design curves of unstiffened plate girder web panels exposed to shear buckling especially at elevated temperatures, the present article considers the mentioned topics. To this end, the web panel shear design relationships mentioned in AISC360-16 are modified to be used in fire conditions. This is achieved by direct utilization of steel stress-strain reduction factors in EN1993-1-2 at elevated temperatures. Analytical equations and design curves are developed to estimate the ultimate shear strength, failure mode and critical limiting temperature for the web panels under the action of a specific shear load. The results based on the curves are compared to the findings of current paper numerical analysis, existing experimental and numerical studies, indicating a good agreement between the results.

FRP strengthening of web panels of steel plate girders against shear buckling. Part-II: Fatigue study and cyclic series of tests

The result of an experimental programme investigating a novel technique to strengthen web plates of steel plate girders against breathing fatigue due to shear buckling deformations is presented. An experimental test series is present in which six specimens were manufactured to simulate the end panel of a plate girder; these were strengthened with an optimized FRP retrofit panel that was developed in an earlier phase of the research project, and tested for plate girder web shear buckling deformation mitigation under repeated cyclic loading, as well as ultimate load capacity enhancement. Test results and non-linear finite element modelling demonstrated the efficiency of this technique for stiffening the web against these deformation and thus reducing the critical stresses, consequently increasing the fatigue life of the girders by a factor ranging between three and seven, depending on the applied stress range and the fatigue resistance assessment method. The research demonstrates the applicability of this novel FRP strengthening technique to prolong and extend the fatigue life of existing plate girder bridges.

FRP strengthening of web panels of steel plate girders against shear buckling Part-I: Static series of tests

The result of an experimental programme investigating a novel technique to strengthen web plates against breathing fatigue is presented in this paper; the programme was divided into five phases, including: (1) the development of a novel preformed corrugated FRP panel for strengthening thin-walled steel plate girder webs against buckling, (2) selecting the adequate adhesive and epoxy using double-lap shear and tension specimens, (3) producing the FRP panel, and (4, 5) testing its performance in two main experimental series; the initial (static) series and the final (cyclic) series. Only the initial series which involved tests on 13 steel plates strengthened with the proposed preformed corrugated FRP panel and subjected to in-plane shear will be reported in this paper. This series investigated the performance of different forms of strengthening under static load, in preparation for a subsequent series of cyclic tests to investigate their fatigue performance. Test results showed the efficiency of the technique at increasing the stiffness of the strengthened specimens in comparison to the unstrengthened ones and reducing the critical stresses which will serve as a precursor for the anticipated increase in the fatigue life of the girders.

Ultimate shear behavior of web panels of HSB800 plate girders

Shear design equations for steel plate girders adopted in many steel design codes were based on classical failure theories for web panels that were fundamentally developed for mild steels. The most salient characteristic of mild steels is that they exhibit a clear yield point followed by the so-called yield plateau in the stress–strain curve. HSB800, which is a high-strength steel recently developed in Korea, neither has a clear yield point nor the yield plateau. This study investigated the ultimate shear behavior of web panels of HSB800 plate girders through nonlinear finite element analysis. Two different stress–strain models were examined for the material nonlinear analysis: bi-linear model and multi-linear model. It was found that the two material models exhibited similar ultimate shear behaviors. The FEA results indicated that existing design equations developed for mild steel are not directly applicable to HSB800. A new shear design equation was developed for HSB800 plate girders from the FEA results using bi-linear model.

The shear strength of end web panels of plate girders with tension field action

This paper describes a series of shear tests of plate girders fabricated from steel plates with a nominal yield stress of 235MPa for the web and 315MPa for flanges. The ultimate shear strength and performance of end web panels with a single double-sided transverse stiffener at support of plate girders undergoing a significant tension field action were investigated experimentally and theoretically. According to shear test results, post-buckling strength in the shear buckling mode has a significant effect on the ultimate shear strength of end web panels of plat girders. Design shear strength formulae for the direct strength method (DSM) for end web panels of plate girders were developed based on shear test results. The results verify that DSM shear curves can accurately predict the ultimate shear strength of web panels of plate girders showing a significant post-buckling behavior in the shear buckling mode.

Web Buckling and Ultimate Strength of Composite Plate Girders Subjected to Shear and Bending

The paper is concerned with ultimate load behavior of steel–concrete composite plate girders subjected to combined action of shear and bending. An analytical method is presented to predict the interactive response of the girder. The method considers the tension field action in the plate girder web panel and shear failure of concrete slab. The method is approximate and can be applied to composite plate girders at the preliminary stages of design. Strength of composite plate girders is investigated by varying the moment/shear ratio. It is shown that ultimate load capacity of composite plate girder is influenced by moment/shear ratio. The predicted results are compared with the corresponding finite-element values.

Failure loads of web panels loaded in pure shear

The effect of tension field action on the ultimate shear strength of web panels has been considered using different approaches. These approaches lead to wide range of predicted shear capacities especially for slender web panels that have large web width–thickness ratios. Therefore, this study aims to investigate the actual behavior of web panels loaded in pure shear. Nonlinear analysis has been conducted using three-dimensional finite element model of plate girder web panels. The study covers a wide range of web width–thickness ratios, web-panel aspect ratios as well as flange bending stiffness. Results show that both short as well as long web panels have substantial post local buckling capacities. However, this additional capacity decreases by increasing the web panel aspect ratios. Moreover, the diagonal tension field is often formed off the web panel diagonal. In addition there is no remarkable effect of the flange bending stiffness on the ultimate shear strength. Based on the numerical results an empirical equation is proposed. Finally comparison has been done with AAHSTO, AISC, and Eurocode-3 as well as different theories.

Design of intermediate transverse stiffeners for shear web panels

The function of intermediate transverse stiffeners attached on plate girder web panels is to provide simple supports so as to reduce the panel aspect ratio, thereby increasing the shear buckling strength. This study investigates the moments of inertia of the transverse stiffeners required to maintain the simple support condition not just for elastic buckling but also for postbuckling through linear buckling and nonlinear finite element analyses. From nonlinear regression analyses of the FEA results, a set of design equations are formulated and compared with the current provisions in AISC and AASHTO LRFD specifications. It is found that the design equation for elastic buckling in AISC and AASHTO LRFD specifications is too conservative especially when the aspect ratio is greater than 1.0. Also, the design equation for postbuckling in AISC and AASHTO specifications results in designs that are too conservative due to oversimplification.

강합성 박스거더 복부판의 탄성전단강도 연구

It is same such as the provision of shear buckling strength of steel composite box girder web panel and plate girder web panel in Korea Highway Bridge Design Standards(2012). But the web panel of steel composite box girder is different from the web of plate girder in that the upper slab and lower flange are connected to the web. So a different shear behavior of the girders is expected. In this study, To calculate a reasonable elastic shear buckling strength of steel composite box girder web panel, ABAQUS program was used. The results from F.E.A and previous studies are compared. It is shown that the web shear buckling strength of steel composite box girder of Korea Highway Bridge Design Standards(2012) is the most conservative.

An analytical method for ultimate shear strength of composite plate girders with web openings

The paper presents an analytical method to determine the ultimate shear capacity of composite plate girders containing web openings. Since one of the flanges of the steel girder is connected to reinforced concrete slab through shear connectors the behavior differs from that of a bare steel plate girder. The analysis of such behavior is complex and hence it is necessary to have a simple method for design office use. A simple analytical method to determine the shear strength of the girder is presented herein. The method considers the effects of composite action between the concrete deck and steel part of the girder and the presence of openings in the webs. Contributions to the shear strength of the girder by tension field action in the plate girder web panel and shear failure of concrete slab are accounted for in the proposed method. The accuracy of the method is assessed by comparing the predicted values with the corresponding experimental results. Effects of web openings on ultimate shear capacity of composite girders are investigated.

Collapse Behavior of Composite Plate Girders Loaded in Shear

This paper is concerned with the ultimate shear capacity of steel-concrete composite plate girders in which one of the flanges of the steel girder is connected to reinforced concrete slab through shear connectors so that the steel girder and the slab act compositely as a single unit. The analysis of such girders becomes complex and it is necessary to have a simple method for design office use. Therefore, an attempt is made in this paper to propose an analytical method to determine the shear strength of a web panel in the girder. The method considers the tension field action in the plate girder web panel and shear failure of concrete slab. The method is approximate and can be applied to composite plate girders at the preliminary stages of design. The predicted results are compared with the corresponding experimental values for girders tested by other researchers and also with finite-element predictions. The predictions are found to be accurate enough for any design office use.

SHEAR STRENGTH OF PLATE GIRDER WEB PANEL WITH OPENING AT ELEVATED TEMPERATURE

For flexibility of accommodating building service plants, openings are often introduced to the web of steel beams which affects the structural behaviour of the beams. The available design methods developed only for the ambient temperature situation. This paper is concerning with the effect of web opening in the ultimate shear capacity of the web panel at elevated temperature. The investigation will include the plate girders web panel containing centrally circular or square holes. In order to provide accurate assessment to the shear load carrying capacity of plate girder web panel with openings, a finite element model was established with both material and geometrical non-linearity by using ANSYS software package. Accuracy of the model is assessed by applying it to plate girders tested earlier by other researchers. Comparison of analytical results with the available experimental results for yielding patterns, ultimate load values and load–deflection relationships show good agreement between the finite element and experimental results thus validating the accuracy of the proposed model. A parametric study is undertaken to gain additional insight into the overall behaviour, failure modes, and deformation capacity for circular and square shapes of web panel openings with various sizes at elevated temperature. From these analyses, it is concluded that, variation of the ultimate shear capacity of plate girders with respect to the size of openings for girders with circular or square openings dropped continuously with increasing the temperature and the size of opening; and the drop in load carrying capacity increases significantly as the temperature increase and the opening size gets larger in size. Finally, an equation based on the results of numerical finite element analyses proposed to anticipate the reduction of the ultimate shear force due to circular or square opening size.

Further Insights into Postbuckling of Web Panels. I: Review of Flange Anchoring Mechanism

This study revisits the anchoring mechanism believed to be the source of the postbuckling strength of plate girder web panels. In classical tension field theories, it has been implicitly assumed that a tension field cannot develop in the web panel without recourse to the anchoring mechanism of the flanges and/or adjacent panels. The contribution of the flange anchoring mechanism in practical plate girders differs from theory to theory. It has been found during this study that the anchoring mechanism hardly develops, no matter how heavy the flanges are, without transverse stiffeners that have sufficient axial stiffness necessary to keep the flanges from moving the web panel inwards during the anchoring action. In practical plate girders, the contribution of the flange anchoring mechanism to the postbuckling strength is negligibly small not because the flanges are too flexible to function as anchors but because the transverse stiffeners are axially too flexible to support the flanges. Taking advantage of the flange anchoring mechanism in practical designs is beyond the realm of possibility because it requires an inconceivably high axial stiffness of the transverse stiffeners.

Non-linear analysis of perforated steel plates subjected to localised symmetrical load

Although the literature contains a number of studies which have been developed to describe the non-linear behaviour of ordinary plates, few works are available on perforated plates, and studies on non-linear behaviour of perforated plates under localised symmetrical load are not studied in depth. The aim of this paper is to provide some insights into the elasto-plastic behaviour of plate girder web panels with circular holes under localised symmetrical load. Numerical analyses of square and rectangular perforated plates with centred and eccentric holes were developed. Results provide new insights into post-critical mechanisms in perforated plates subjected to localised loads when the length of the symmetrical compressive load, hole diameter and steel yield limit vary. An increase in the critical slenderness of the plate (a value at which transition from elastic to plastic collapse occurs) and a corresponding reduction in the elastic critical load occur when the dimensions of the hole increase. A further increase in the critical slenderness occurs when the length of the localised load is reduced. High-performance steel may be subject to buckling with a lower possibility of post-critical mechanisms: a reduction in critical slenderness occurs when the steel grade increases. Lastly, numerical analyses of slender and thick perforated plates were developed and their results compared.

Ultimate shear strength of long web panels

Both the Basler model and the Rockey model developed during the early 1960s and 1970s predict reasonably well the postbuckling strength of plate girder web panels subjected to pure shear for panels having an aspect ratio (stiffener spacing/web depth) less than or equal to 1.5. The accuracy of these models deviates significantly when applied to panels with an aspect ratio equal to or greater than 3.0. The majority of all steel structures in the world have been designed and built based on these two major theories or their derivatives that recognize the reserve strength afforded by tension field action in the postbuckling stage. However, no single theory has ever emerged that explains the seemingly elusive stress distributions present in web panels during postbuckling until Yoo and Lee shed light on the true mechanics of web panel postbuckling behavior in shear. This paper revisits the validity of an arbitrary limit imposed by Basler on the maximum aspect ratio of a transversely stiffened web panel and develops a new method of predicting the ultimate shear strength of web panels with high aspect ratios.

Experimental behaviour of a thermally restrained plate girder loaded in shear at elevated temperature

This paper outlines an experimental investigation of twelve simply supported steel plate girders subjected to shear loading at elevated temperature. Three different series of steel plate girders have been tested at three constant elevated temperature levels. Additional axial restraints were applied onto beams to simulate the thermal restraint effects of adjacent cooler parts of steel-framed structure in fire. Based on test results and observations, the pre- and post-buckling behaviours of plate girder web panels at high temperature were discussed. In addition, finite element modelling of the web panels was conducted and numerical models generally agreed well with test results. It was observed that the ultimate shear capacity decreased significantly under a thermal restraint effect.