Web Stiffeners Research Articles

Ultimate strength assessment of randomly pitted stiffened panels considering stiffener corrosion

Stiffened panels are renowned for their exceptional load-bearing capabilities due to their high strength-to-weight ratio and are extensively utilized in ship and marine structures. Nevertheless, they are susceptible to failure under compression, particularly in marine environments where corrosion leads to material and structural degradation. Stiffener corrosion was not involved adequately in current studies, with an unclear synergistic effect of corrosion damage with structural configurations. This paper introduces a numerical modeling approach to develop finite element (FE) models of panels with random pitting corrosion, considering both corrosion on the plating and stiffeners. These FE models are validated against existing experiments and empirical formulae and employed to investigate the effect of random pitting damage on the ultimate strength of panels. The study examines the impact of various structural parameters, such as plate aspect ratio, plate slenderness ratio, stiffener slenderness ratio, and the height-to-thickness ratio of stiffener web, on ultimate strength under different levels of pitting damage. Additionally, the load-bearing behavior and failure modes of damaged panels are analyzed. An artificial neural network (ANN) is developed to predict the ultimate strength of pitted panels. The findings indicate that the ultimate strength of panels with stiffener corrosion in the form of random pitting corrosion leads to a more significant reduction by about 17.7% than that without stiffener corrosion, potentially altering the failure mode. The proposed ANN model accurately predicts the ultimate strength of pitted panels with and without stiffener corrosion, with a mean relative error of approximately 1.1% compared to FE analysis results.

Hysteretic behavior of eccentric RHS beam-to-column joints under cyclic in-plane bending

This paper conducted experimental and numerical studies on the hysteretic behavior of eccentric rectangular hollow section (RHS) beam-to-column joints under cyclic in-plane bending. The study began with the design of both stiffened and unstiffened joints, followed by hysteresis tests that revealed failure modes like web weld tearing and stiffener fracture. The seismic performance of the joints was evaluated using hysteresis curves, skeleton curves, ductility coefficients, strength degradation coefficients, and energy dissipation coefficients. Compared to unstiffened joints, the stiffened joints exhibited a 30 % increase in peak load and a 18 % improvement in maximum energy dissipation coefficient. Subsequently, finite element (FE) analysis was performed, and the influence of key parameters on the hysteretic behavior was studied using validated FE models. The results indicated that the hysteretic behavior was positively correlated with the flange width ratio of beam to column, the ratio of beam section height to column flange width, and the thickness ratio of beam to column, while it was negatively correlated with the width-to-thickness ratio of the column. Finally, a mathematical model for the hysteretic behavior of both stiffened and unstiffened joints was developed and validated through experimental and FE comparison, offering practical applicability in engineering design.

An experimental study on web-bearing resistance of cold-formed steel sigma-shaped sections with web holes under interior-two-flange loading case

Cold-formed steel (CFS) sigma-shaped sections used as flooring joists and bearers are commonly fabricated with web holes to accommodate building services. These sections featuring web stiffeners and curved lips exhibit lower web-bearing resistance than traditional lipped channel sections. However, the web-bearing resistance of CFS sigma-shaped sections with web holes has not been thoroughly investigated. To address this gap, a detailed experimental investigation was conducted, testing 29 CFS sigma-shaped sections with web holes under an interior-two-flange (ITF) loading case. For comparison, specimens without web holes were also tested. Variables such as hole diameter ratio, hole location, bearing length, and flange condition were examined. A finite element (FE) model was developed and validated against the test results. The results indicated that the web-bearing resistance for specimens with web holes was reduced by 24.0% on average. To assess the accuracy of existing design specifications, the test results were compared against the design strengths predicted by the American Iron and Steel Institute (AISI) (2016), Australian and New Zealand Standards (AS/NZS) (2018), European Standard (EC3) (2006), and Uzzaman et al. (2012). The comparison revealed that the design strength predicted by Uzzaman et al. (2012) agreed well with the test results.

Behavior of Extended Single-Plate Shear Connections Subjected to Combined Shear and Compression Forces Using Finite Element Analysis

Extended single-plate shear connections can be subjected to compression loads in addition to shear loads during extreme events like wind and earthquakes. However, the existing interaction equations found in the AISC Steel Construction Manual, in literature, and in design examples—which are being used in design for combined loading cases—have not been formally validated for use by experimental testing or finite element analysis. This research aims to study the behavior of these connections when subjected to combined loading of shear and compression force by performing a nonlinear finite element analysis in ABAQUS. The variables considered in the study are column web stiffness, connection configurations, and different bracing conditions of the beam. The results from these analyses were compared to the available interaction equations in the AISC Manual and in literature to assess their applicability under different conditions. Shear-compression interaction plots were generated from the results that show the shear strength decreases with an increase in compression force in the connection. The effect of the compression force on the shear strength depends on the column web’s rigidity and the bracing condition of the beam.

Experimental study on seismic performance of replaceable shear links with low-yield-point steel

Based on the design concept of controllable seismic damage during earthquakes and rapid functional recovery after earthquakes, a replaceable shear link with low-yield-point steel was proposed. Quasi-static cyclic loading tests and numerical analysis were conducted on six specimens. The failure mode, seismic performance, energy dissipation behavior, and shear distribution of each specimen were carefully considered to investigate the effects of web steel, web stiffening configuration and stiffener-plate stiffness ratio. The results showed that the stiffened specimens showed full-sectional shear yielding behavior, while the non-stiffened specimens exhibited coupling behavior of web yielding and buckling. Specimens with reasonable design parameters had excellent ductility and energy dissipation capacity, with the plastic shear angle exceeding 0.157 rad and the maximum equivalent viscous damping coefficients greater than 0.51 (80% of the theoretical maximum value). Owing to the cyclic strengthening of the low-yield-point steel web and the contributions of stiffeners and flanges, the specimens showed obvious overstrength behavior, with the overstrength factor ranging from 1.99 to 2.39. The cross-stiffening configuration was conducive to enhancing the seismic performance of shear links. Smaller web width-to-thickness ratios were recommended to match with smaller stiffener-plate stiffness ratios. Extended cross stiffeners and diagonal stiffeners resulted in earlier cracking of the web welds, which adversely affected the ductility of the specimens.

Optimization of Cold-Formed Thin-Walled Cross-Sections in Portal Frames

Portal frames with built-up cold-formed cross-sections hold significant potential; however, there is a notable gap in the analysis of cross-section types and connections. In this study, an optimization algorithm was developed for the closed cross-sections of portal frame members. An optimization algorithm was tested against optimized open cold-formed cross-sections. The results indicated a portal frame volume up to 38% lower where members were assembled of optimal closed cross-sections when compared to frames with optimal open cross-sections. Parametric analysis was carried out, where two types of cross-sections were examined: Type A, with four web stiffeners bent inwards, and Type B, with four web stiffeners bent outwards. The optimization was conducted using a Genetic Algorithm in MATLAB R2022b. Portal frames with optimal Type B cross-sections had a volume that was up to 22% lower when compared to frames with optimal Type A cross-sections. Significant differences were noted between the optimal beam and column cross-sections, with the optimal column cross-section thickness being on average 74% greater, but the optimal beam cross-section height being on average 81% greater than those of the respective counterparts. In this article, a practical assembly solution for the connection of the frame members was proposed for the optimized novel closed cross-section types in portal frames. However, the strength and stiffness of these connections were not analyzed in this research.

Research on post-fire mechanical properties of thin-walled cold-formed steel and its influence on the Σ-shaped columns after fire exposure

This paper conducts a comprehensive investigation into the post-fire mechanical properties of thin-walled cold-formed steel (CFS) and evaluates the design method for the post-fire load-bearing capacity of CFS lipped channel section with web stiffener (Σ-shaped) columns. A total of 144 tensile tests were conducted to determine the mechanical properties of CFS after exposure to heating treatment. The study considered the effects of varied material strengths (Q235 and Q420), plate thicknesses (1.5 mm and 2.5 mm), extraction positions (flat plate, 90° corner, and 45° corner), as well as heating temperatures ranging from 20 °C to 800 °C. The research indicates that the heating temperature does not have a prominent influence on the elastic modulus of CFS, whereas its impact on yield strength is pronounced. After exposure to 800 °C, the yield strength of CFS can be reduced by 40 %, but the strain-hardening effect by cold-working still existed, which enhanced the yield strength by up to 20 %. This paper presents a predictive formula for the reduction factor of the mechanical properties. To assess the influence of post-fire mechanical properties on the load-bearing capacity of CFS columns, a finite element model of Σ-shaped columns was developed and calibrated. The simulation results indicate that the post-fire strain-hardening effect at corners would enhance the load-bearing capacity by less than 6 %. Finally, based on a parametric analysis, it was demonstrated that the Direct Strength Method (DSM) applied for distortional-local interaction buckling columns was still effective once the post-fire mechanical properties were incorporated when slenderness factor λdl > 1.5.

AN APPROACH OF WEB STIFFENER CALCULATION IN THIN-WALLED COLUMNS

This article presents an analytical approach for calculating web stiffeners in thin-walled columns. A novel method is introduced, which treats each bending point in the cross-section web as a separate stiffener. The advantages of this calculation method are discussed, highlighting its increased versatility in designing cross-section geometry. The load-bearing strength of axially compressed thin-walled closed cross-section columns, calculated using this method, is compared to analytical calculations based on the Eurocode 3-1-3 methodology and to the finite element method analysis. Calculation results of columns with cross-sections including shallow web stiffeners were up to 9.22% less conservative when compared to the Eurocode 3-1-3 methodology. The results demonstrate great compliance of the proposed method for column crosssections with deep stiffeners. Finite element method (FEM) analysis was performed to verify the calculated load bearing strengths of the columns according to both calculation methodologies. FEM analysis confirmed the reliance of the calculated results and showed, that the load bearing strengths calculated using the newly presented methodology were ranging from 88.77% to 97.86% of load bearing strength calculated using finite element method. These results proved, that the proposed method provides an accurate load bearing strength of thin-walled columns with web stiffeners.

An advanced design diagram of stiffened plate subjected to combined in-plane and lateral loads considering initial deflection effects

This study presents an advanced methodology for stiffened plates subjected to combined in-plane longitudinal compression and lateral loads. The proposed methodology is based on comprehensive numerical parametric analyses, and it utilises newly developed design curves for the lateral pressure limit and tailored empirical formulae for stiffened plates to increase the precision of ship structural designs. Plate–stiffener combination (PSC) members are used for the limit state analysis, which introduces various positions and initial deflection shapes specific to the PSC models. Local buckling-shaped deflections of the stiffener web are also incorporated into the analysis, which closely mirrors the real-world welding conditions of stiffened plates and provides deeper insight into their load-bearing capacities. These findings highlight the importance of accurately selecting the positions and initial deflections of stiffeners in PSC-based analyses to ensure that structural predictions are safe and reliable. The proposed method is grounded in conservative PSC models and represents a significant advancement in ship structural design in terms of safety and practicality.

DATA-DRIVEN ASSESSMENT OF SHEAR STRENGTH OF SINUSOIDAL CORRUGATED STEEL WEBS

The construction industry increasingly recognizes the value of steel beams with corrugated webs for their enhanced resistance to buckling, superior shear capacity, and the elimination of the need for web stiffeners. While a wealth of research focuses on beams with trapezoidal corrugated webs, investigations into sinusoidal corrugated webs (SCWs) remain comparatively sparse. This work investigates the variability in the prediction of the various models and assesses the interactions among different influencing parameters affecting the shear strength of sinusoidal corrugated steel web beams. A comprehensive database of 66 experimental data on SCW beams is assembled and rigorously examined to facilitate this analysis. The collected database is used to test the prediction accuracy of the existing design models provided by codes or proposed models in the literature. The Eurocode3 and DASt-Ri. 015 code models are considered in this study. The results of the evaluated prediction models showed considerable scatters, emphasizing the ongoing need for research to enhance the accuracy of these predictive models for better application in construction practices.

DATA-DRIVEN ASSESSMENT OF SHEAR STRENGTH OF SINUSOIDAL CORRUGATED STEEL WEBS

The construction industry increasingly recognizes the value of steel beams with corrugated webs for their enhanced resistance to buckling, superior shear capacity, and the elimination of the need for web stiffeners. While a wealth of research focuses on beams with trapezoidal corrugated webs, investigations into sinusoidal corrugated webs (SCWs) remain comparatively sparse. This work investigates the variability in the prediction of the various models and assesses the interactions among different influencing parameters affecting the shear strength of sinusoidal corrugated steel web beams. A comprehensive database of 66 experimental data on SCW beams is assembled and rigorously examined to facilitate this analysis. The collected database is used to test the prediction accuracy of the existing design models provided by codes or proposed models in the literature. The Eurocode3 and DASt-Ri. 015 code models are considered in this study. The results of the evaluated prediction models showed considerable scatters, emphasizing the ongoing need for research to enhance the accuracy of these predictive models for better application in construction practices.

Shear buckling resistance models for plate girders – Review and improvements

The paper reviews the shear buckling resistance models for plate girders and proposes an improved model based on the EN 1993–1-5 formulation for evaluating the failure load of a plate girder loaded in shear. The code-based shear resistance models proposed by Basler, Rockey et al. and Höglund are discussed. The Höglund model is further expanded, and the location of the plastic hinges in the flanges is modified, taking into account the relative sizes of the web, flanges, and transverse and longitudinal stiffeners, to produce a consistent tension field model of the plate girder shear post-buckling behaviour.A database was created from the experimental tests on thin steel plate girders loaded in shear that were conducted over time. The proposed model's results are validated by comparison with the shear resistances reported for this database's 261 tests. Statistical analysis shows that the proposed modifications are as accurate as the EN1993–1-5 formulation with the extra advantage of preventing several unsafe results for steel plate girders with high flange-to-web ratios.

Digital simulation of distortion-induced fatigue in steel bridges with different geometrical configurations

Distortion-induced fatigue cracks at web gaps often occur in multi-girder steel bridges under vehicle loads. This paper presents full size digital simulations of steel girder bridges with different geometrical configurations, to explore the distortion-induced fatigue cracking performance. In the digital simulations, four geometrics are considered, in addition to two web gap details, namely the vertical stiffener web gap and the horizontal gusset plate web gap. Introducing multi-layer and multi-pass welds residual welding stress fields, digital fatigue simulation results show that the distortion-induced fatigue cracks at both web gaps are Mode I-II-III combined cracks dominated by Mode I. The coupling of the three modes is more prominent at the vertical stiffener web gap compared to the horizontal gusset plate web gap. In the skewed bridge, curved bridge, and skewed-curved bridge, the significant bending-torsional coupling effect, the structural asymmetry, and the stress deformation asymmetry cause an increment in distortion ranges, fatigue crack growth rates, and the proportions of Mode II and III cracks. The fatigue strength categories for vertical stiffener web gap and horizontal gusset plate web gap in straight, skewed, curved and skewed-curved bridges are category 125, 112, 110 and 110, and category 160, 140, 100 and 100 of the Chinese specification and Eurocode, respectively. Therefore, the geometrical configuration is an important factor affecting the distortion-induced fatigue behavior, which should be considered in the fatigue design and maintenance of steel girder bridges.

Improved deep neural network for predicting structural response of stiffened cylindrical shells to far-field underwater explosion

This paper is focused on the application of the machine learning for predicting structural response of ring stiffened cylindrical shells subjected to far-field underwater explosion. Three deep neural network (DNN) models are combined to predict the progressive plastic deformation behaviour of stiffened cylindrical shells subjected to the shock wave produced by a TNT charge. In the DNN regression models, the input variables include the charge mass, stand-off distance, detonation depth, cylindrical shell thickness, stiffener web and flange. These three DNN models composed of multi hidden layers are trained based on the data collection originated from a series of simulations performed by the ABAQUS finite element solver. Grid search is introduced to the hyperparameter tuning for deep learning, improving the prediction performance of machine learning methods. The DNN models are compared to the models trained using another three methods: multiple linear regression, decision tree and k-nearest neighbour. An improved Adam optimisation algorithm is used to increase the accuracy of prediction. The challenges encountered during the predictions are discussed to provide a more comprehensive insight into the advantage of the proposed DNN models. The DNN regression models can well predict the permanent plastic deformation and strain of stiffened cylindrical shells.

Transverse Analysis of Box Girders with Corrugated Steel Webs

The utilisation of box girders with corrugated steel webs (CSWs) represents an innovative approach to bridge superstructure design that has garnered substantial popularity worldwide, with a notable prevalence in both Asia and Europe. Compared with traditional box girders, they avoid web cracking, improving the prestressing efficiency and bridge spanning ability. As an innovative box girder, a corrugated web can increase the cantilever length and transverse stiffness, and at the same time, it reduces the dead weight of the bridge deck. However, little research has been conducted on the mechanical properties of this novel spine-like box girder with CSWs, especially its transverse performance, although it has been used in many applications. In this paper, the effect of the web form on the behaviour of box girders is introduced. Therefore, three representative three-dimensional (3D) finite-element models (i.e., corrugated web box girder, flat web box girder, and ordinary equivalent concrete web box girder) have been established to quantitatively investigate the influence of corrugated web stiffness on transverse stress under the action of gravity and vehicle loads. Generally, significant differences in the mechanical performance of box girders with CSWs have been observed compared with conventional box girders with concrete webs. Additionally, parametric studies to investigate the influences of the corrugation dimensions (in term of the corrugation height, web thickness, panel width, web height and elastic modulus) on the transverse stiffness of such bridges are analyzed. The results show that a new stiffness formula can be put forward to consider the effect of web height, and a high-strength steel web needs to be developed urgently for box girders with CSWs in the near future. Overall, the results of this investigation can be used as a reference for transverse designing and segmental construction of similar projects.

Experimental and numerical studies on the ultimate bending moment of welded plate girder with perforated web

ABSTRACT Combined opening girders with high stiffener webs used in the superstructure areas of passenger ships are prone to complex buckling phenomena under combined longitudinal and vertical loads caused by overall longitudinal bending and vertical forces from the deck cargo. In addition, the deformation and stress induced during structural assembly and welding make the buckling behaviour more difficult to predict. In response to this situation, thermal elastic–plastic and nonlinear finite element methods were used to simulate the welding and loading process and related experiments were conducted to provide a comparison. We further extended the investigation of the buckling behaviour of girders to the combined opening plate frame and investigated the buckling behaviour using experiments. This research on the buckling behaviour of combined opening girders and plate frames could provide a reference for the optimal design of these members in actual ship structures.

Free vibration analysis of hygrothermally stable stiffened composite plates with plate-stiffener interfacial debonding

Stiffeners are frequently utilized in many engineering projects because they boost strength while adding only a small amount of weight to the overall structure. The environments that the stiffened composite constructions are typically exposed to are harsh, which can result in damage like interlayer delamination and debond at the plate-stiffener interface, which can cause catastrophic failure. As a result, it is necessary to examine these structures’ dynamic behavior in addition to their stability performance. The current study attempts to investigate the free vibration response of stiffened composite plates with plate-stiffener interfacial debonding under hygrothermal circumstances using a robust finite element (FE) model. The skin and stiffener flange are simulated in the current work using a 9-noded heterosis element to prevent the shear-locking issue. Additionally, to considerably enhance computational performance, the stiffener web is formulated as a 3-noded isoparametric beam element with the torsion correction factor. Additionally, a dummy node is created to represent the debond, and a fictitious spring is added to stop the nodes from interpenetrating one another. Three schemes of hygrothermally stable laminates (θ/(90- θ))s, (22.5/−67.5)s and (77.5/−12.5)s are considered to identify the stiffened plate configuration with improved free vibration characteristics. Further, extensive parametric analyses are conducted on the obtained stiffened plate with improved performance in a hygrothermal environment by considering debond at the skin-stiffener interface. The vibrational behavior of the debonded plate is shown to be significantly more affected by moisture than by temperature. Additionally, the debond has a more obvious impact on the vibration characteristics in the plate with a centrally attached stiffener than in the plate with an eccentricity attached stiffener. As a result, the established FE formulation is anticipated to be trustworthy and computationally effective while effectively analyzing the debonded stiffened panel’s free vibration behavior in a hygrothermal environment.

Seismic Performance of Iwf Flexural Link in Chevron Eccentrically Brace Frames (V-EBFs) with Different Stiffener Space

Eccentrically Braced Frames (EBFs) are the structural systems that are recommended to be constructed in Earthquake Hazard Areas. This system combines good characteristics in withstanding the seismic load, i.e., stiffness, ductility, and dissipation energy. Link is a component in EBFs that play the role of the seismic energy dissipator. As far, several studies have been conducted to enhance the link performance, but the information is still limited. This study observed the structural performance of the IWF flexural link, where this link will experience failure at the flange due to seismic energy dissipation. The investigation was conducted by establishing three Finite Element (FE) models of flexural link. Each link was designed with the same length, i.e. 1000 mm. Three-link models were distinguished by the differences in web stiffener configuration, i.e., non-stiffener link, 250 mmstiffener spacing link, and 100 mm-stiffener spacing link, respectively. All models were examined under cyclic loading with yield displacement controlled. The research discovered that adding the web stiffener on the IWF flexural link significantly escalated the EBFs’ seismic performance, i.e., strength, stiffness, ductility, and dissipation energy. The best seismic performance was presented by a 100 mm-stiffener spacing link. Accordingly, it is indicated that arranging the web stiffeners at the narrow space in the IWF link can be suggested to improve the seismic performance of EBFs.

Design optimisation for cold rolled steel beam sections with web and flange stiffeners

This paper presents the analysis and design optimisation of the cold rolled steel sections for flexural strength considering the effect of cold working exerted on the section during the roll forming process. The sections included channel and zed shapes with complex longitudinal web and flange stiffeners. Nonlinear Finite Element (FE) modelling was developed to model the flexural strength of the channel and zed beams and validated against the four-point bending experiments for these sections. The material properties of steel at the section's flat parts, corners, and stiffener bends were obtained from tensile tests and were incorporated into the FE simulations to account for the true material properties at these regions due to the cold working during the roll forming process. The strength enhancement at the section corners and stiffener bends obtained from tensile tests were also compared with the predicted values from design standards. The section strength was then optimised using FE modelling results based on the Design Of Experiments (DOE) and response surface methodology. Optimal designs for the channel and zed sections with maximum strength in distortional buckling could be obtained while changing the stiffeners' position, shape, sizes, and considering true material properties at section corners and stiffener bends. It revealed that, for the two sets of channel and zed sections with the depths of 145 mm and 170 mm, the optimal designs provided up to 43% and 39% increase in flexural strength for the channel and zed sections, respectively; however, when the true material properties at the section corner and the stiffener's bend regions was included, the increase in flexural strength increased up to 50% and 41%, respectively. Including flange stiffeners to the sections with longitudinal web stiffeners generally increased further the section strength. However, the levels of increase were largely dependent on the section depths and material properties.

Influence of transverse stiffening on the lateral-torsional buckling resistance of built-up I-girders

Recent studies have shown that the AISC 360 Specification substantially overpredicts the strength of certain built-up steel I-girders subjected to high moment gradient. These strength overpredictions have been attributed to various effects, including (1) the direct scaling of the uniform bending lateral-torsional buckling (LTB) strength curve by the elastically-derived moment gradient factor, Cb, without considering the yielding induced at the larger predicted strengths, (2) reduction in the elastic LTB strength due to web shear and corresponding elastic distortional buckling effects, (3) compression flange lateral bending due to amplification of the initial flange sweep, and (4) intensification of the compression flange lateral bending due to web distortion. This paper scrutinizes the impact of transverse stiffening on the elastic and inelastic LTB resistance of a suite of I-girders previously evaluated experimentally and numerically without transverse stiffening through full-nonlinear shell finite element analysis test simulations. The results provide further insight into the sources of the AISC Specification overpredictions and the practical aspects of adding transverse web stiffeners to increase the LTB strength.