Longitudinal Stiffeners Research Articles

Analytical and numerical calculation of the buckling stress for panels with closed‐section stiffeners

AbstractThe forthcoming second generation of EN 1993‐1‐5 is bringing changes in terms of buckling and interpolation curves that allow the positive effects of torsional stiffness of closed‐section stiffeners to be taken into account. Regarding the determination of the critical buckling stress for global plate buckling, analytical or numerical methods may be used. FprEN 1993‐1‐5 provides a simplified analytical equation for determining the critical buckling stress of an equivalent orthotropic plate, which can also be found in the informative Annex A of EN 1993‐1‐5. The given equation does not take into account the torsional stiffness of longitudinal stiffeners with closed cross‐sections. The latter are often used in plated structures due to fabrication and strength benefits. This paper compares two methods for determining the elastic critical plate buckling stress that consider the positive effect of the torsional stiffness of closed‐section stiffeners. First, a newly proposed analytical method that accounts for the torsional stiffness of closed‐section stiffeners is derived on the same basis as the current equation in Annex A. Secondly, a numerical linear buckling analysis is performed on a large number of stiffened panels. The advantages and disadvantages of both methods are pointed out. Finally, both values are used to determine the ultimate resistance of plates and with GMNIA results from previous studies.

Research on Seismic Performance and Reinforcement Methods for Self-Centering Rocking Steel Bridge Piers

To study the seismic performance of self-centering circular-section rocking steel bridge piers whose functions can be restored after an earthquake, a high-precision finite element (FE) analysis model of such a bridge piers was established. The hysteresis behavior of concrete-infilled and hollow rocking steel bridge piers was compared. In response to the characteristics of the local deformation of the wall plates and elliptical deformation of the bottom surface, two reinforcement methods for the pier bottom, namely thickening the wall plate and adding longitudinal stiffeners in the plastic zone of the pier bottom, were proposed. The pseudo static analysis of bridge piers was carried out considering the effects of overall design parameters and reinforcement parameters of the pier bottom. The results indicate that the FE model used in this paper can obtain accurate horizontal load-displacement curves of rocking steel bridge piers. The hysteresis curves of the rocking steel bridge piers and infilled concrete rocking steel bridge piers is close, and directly using hollow steel bridge piers can improve the economic efficiency of the design. Compared to adding longitudinal stiffeners, the reinforcement form of thickened wall plates at the pier bottom has a better effect in improving the seismic performance of bridge piers. The reinforcement of the pier bottom has little effect on the energy dissipation capacity of the bridge pier, but it helps to reduce residual displacement and improve lateral stiffness.

DETERMINATION OF THE RIB-TO-CROSSBEAM STRESSES IN ORTHOTROPIC STEEL DECKS

For long span bridges, the orthotropic steel deck (OSD) is the most popular option for the bridge deck. Normal OSDs consist out of the steel bridge deck, the longitudinal stiffeners (ribs), and the transversal beams. All of the elements are welded together. The welds create geometrical discontinuities that will result in concentrations, which lead to fatigue damage under repetitive loading. In this research, a simplified calculation method for determining the dimensions of OSDs is developed. This method shares the same notion as the Pelikan-Esslinger method, which is using an idealized orthotropic plate. Solving the idealized orthotropic plate, the internal forces of the actual OSD may be acquired. To calculate the distortional stresses, the shear deformation is treated as an independent variable and added to the simplified calculation method. The system of partial differential equations is derived through the equilibrium relationships of the substituting plate. Three rigidity coefficients are required in this method, namely the flexural rigidity coefficient, the torsional rigidity coefficient, and the shear rigidity coefficient. The former two are the same as in the Pelikan-Esslinger method. By performing a frame analysis, the formulas of the shear rigidity coefficient are achieved. Then, a simple local model is proposed for calculating the nominal distortional stress under the weld of the wall of the rib. To summarize, this research shows the possibility of optimizing the prevailing design the rib-to-crossbeam connection. The proposed fatigue life assessment method and simplified calculation method could be adopted in the future.

Structural Stability of Tailwater Penstock in Xiamen Pumped Storage Power Station

To study the external water pressure that can be borne by the steel lining of the tailwater penstock of a pumped storage power station, the optimization of the steel lining shape provides the basis for ensuring its normal operation. In this paper, based on the finite element method and finite element analysis software ABAQUS, the calculation and analysis model of different stiffening ring schemes for tailrace penstock is established, structural stability is calculated and the influence of different stiffening schemes is compared and analyzed. The results show that the structural stability can meet the requirements of the code by setting the T-shaped stiffening ring and longitudinal stiffening rib. With the addition of longitudinal stiffeners, the steel lining tends to the stress characteristics of the two-way slab, and the overall stress deformation tends to be balanced, which can improve the external pressure resistance of the steel lining in the gradual change section to a certain extent.

Laboratory Results of a Real-Time SHM Integrated System on a P180 Full-Scale Wing-Box Section.

The final objective of the study herein reported is the preliminary evaluation of the capability of an original, real-time SHM system applied to a full-scale wing-box section as a significant aircraft component, during an experimental campaign carried out at the Piaggio Lab in Villanova D'Albenga, Italy. In previous works, the authors have shown that such a system could be applied to composite beams, to reveal damage along the bonding line between a longitudinal stiffening element and the cap. Utilizing a suitable scaling process, such work has then been exported to more complex components, in order to confirm the outcomes that were already achieved, and, possibly, expanding the considerations that should drive the project towards an actual implementation of the proposed architecture. Relevant topics dealt with in this publication concern the application of the structural health monitoring system to different temperature ranges, by taking advantage of a climatic room operating at the Piaggio sites, and the contemporary use of several algorithms for real-time elaborations. Besides the real-time characteristics already introduced and discussed previously, such further steps are essential for applying the proposed architecture on board an aircraft, and to increase reliability aspects by accessing the possibility of comparing different information derived from different sources. The activities herein reported have been carried out within the Italian segment of the RESUME project, a joint co-operation between the Ministry of Defense of Israel and the Ministry of Defense of Italy.

Experimental study on torsional behavior of tapered high strength thin-walled concrete-filled double-skin steel tubular columns

Comparing with traditional straight concrete-filled double-skin steel tubular (CFDST) members, tapered CFDST members have been increasingly used in the domain of power industry due to esthetics and special spatial experience. In addition, the utilization of high strength materials can reduce cross-sectional area and further lower construction cost. In this paper, the torsional behavior of tapered high-strength thin-walled CFDST (THSTW-CFDST) columns with or without longitudinal stiffeners was investigated and a total of twenty tapered THSTW-CFDST specimens were tested. The failure modes, torque-torsional angle curves and torsional capacity of the THSTW-CFDST columns were investigated. The results demonstrate that the installation of stiffeners can significantly improve the local stability of thin-walled steel tubes, but reduce the torsional capacity of the members. Compared with THSTW-CFDST specimens without stiffeners, the torsional capacities of those with stiffeners have been apparently reduced. Based on the experimental results, the finite element (FE) model was developed and verified, and then utilized to ascertain the force-transfer mechanism and the stress development process of each component of THSTW-CFDST columns. In addition, the effects of the various parameters including hollow ratio, diameter-to-thickness ratio, inner steel tube strength to outer steel tube strength ratio, concrete strength the torsional behavior of THSTW-CFDST members were quantitatively assessed. Finally, the accuracy of the existing methods for predicting the torsional capacity of THSTW-CFDST members was evaluated.

Misalignment effect on the ultimate strength of welded stiffened panels under uniaxial compression

Longitudinal stiffener misalignment (LSM) is inevitable in the manufacturing process of stiffened hull panels, affecting the geometric appearance and bearing capacity. However, the knowledge of the effect of LSM on the ultimate strength of stiffened panels is limited. In this paper, continuous numerical simulations are first conducted regarding forced alignment, welding process and ultimate strength analysis by using the nonlinear finite element method. A simplified model is then derived considering LSM and initial deflection based on a comparative study of the ultimate strength and collapse patterns. Influences of various combinations of LSM and initial deflection on the strength characteristics and failure behaviors are documented and discussed. According to the parametric analysis, it is found that the LSM imperfection decreases the ultimate strength, but the degree of reduction depends on the shape and amplitude of the panel initial deflection. The maximum reduction rate is 8.71% occurring in the case where the deflection shape with slight amplitude is symmetric. On the basis of 120 numerical results, an empirical formula is proposed for predicting the residual strength as a function of the dimensionless misalignment degree together with panel and column slenderness.

Buckling behavior of orthotropic steel deck stiffened by slender bulb flats for large span bridges

Slender bulb flat stiffeners with a large height-to-thickness ratio were proposed for the orthotropic steel decks (OSDs) in a large span suspension bridge. The buckling behavior of the panels stiffened with bulb stiffeners under pure compression was experimentally and numerically studied in this paper. Four specimens consisting of four longitudinal stiffeners and a top deck plate were fabricated and subjected to axial compression loading tests. Finite element models were established and validated by the result tests. A parametric analysis was conducted to study the effects of residual stresses and geometric imperfections on buckling behavior. A buckling failure of overall stiffener buckling before the yielding and ductile post-buckling behavior were observed in the tests. A buckling strength of 311∼337 MPa was obtained in the tests. The ratio of buckling stress to yield strength ranging from 0.80 to 0.86 was slightly lower than that of closed ribs, which shows a potential use of the slender bulb flat in large span suspension bridges. The numerical results showed that the residual stresses can decrease the load-bearing capacity by 10%. The residual stresses have a higher influence on the resistance than the regular geometrical imperfections. The standard vehicle load has negligible influence on the buckling resistance, but overload may cause a certain decrease.

Experimental and numerical study on the failure modes of ship stiffened plate structure under projectile perforation

Four sets of experiments were carried out on penetrating the ship stiffened plate structures which were made of panel plates with different thicknesses and stiffeners with different sizes. Ballistic characteristics of projectiles were recorded by a high-speed camera system. Through analysis, it has been found that stiffeners can reduce the overall plastic deformation of the panel and make projectile attitude change significantly. The failure modes of stiffened plates, which are obviously different from the homogeneous plates, change accordingly with the change of impact points. In order to analyze the problem better, the stiffened plate is assumed to be composed by four parts, namely main panel plate, transverse large stiffener ventral plate, transverse large stiffener flange plate and longitudinal weak stiffener. The penetration process has been simulated by 3D analysis using ANSYS/LS-DYNA which was verified by experiments, and numerical simulations were carried out. Through the numerical and experimental results, a variety of failure modes have been observed. Failure modes of stiffened plates are found to be composed by four types and summarized.

Compensating steel web-opened beams for the loss in cyclic shear capacity by longitudinal stiffeners

Compensating steel web-opened beams for the loss in cyclic shear capacity by longitudinal stiffeners

Patch loading resistance of slender plate girders with multiple longitudinal stiffeners

StahlbauVolume 92, Issue 4 p. 214-214 Empfehlungen der Redaktion Patch loading resistance of slender plate girders with multiple longitudinal stiffeners First published: 03 April 2023 https://doi.org/10.1002/stab.202370404Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. Volume92, Issue4April 2023Pages 214-214 RelatedInformation

Topology Optimization of Stiffened Steel Plate Shear Wall Based on the Bidirectional Progressive Structural Optimization Method

Many studies on structural topology optimization of steel plate shear walls have been conducted. However, research on topology optimization using the bidirectional evolutionary structural optimization method is limited. Accordingly, this study optimized the topology of the stiffening effect of steel plate shear walls (SPSWs) based on this method. A finite element model of the SPSW was established using Abaqus software through the “sandwich” modeling method. An optimization region was expanded into two optimization regions. As the optimization targets, SPSWs with different aspect ratios were selected. Elastoplastic optimization of a single-layer SPSW was performed through the horizontal displacement cyclic loading, and the distribution law of the stiffening effect was obtained. The stiffeners on the SPSW were arranged according to the SPSW-A075 scheme. Monotonic and reciprocating loading simulation tests were performed on the unstiffened SPSW and common transverse and longitudinal stiffeners to analyze their mechanical properties. The results show that the optimized layout of the stiffened SPSW demonstrated better seismic performance and energy dissipation capacity. The buckling bearing capacity increased by 2.17–2.61 times, and the stiffness and initial stiffness improved significantly.

On the Fatigue Strength of Welded High-Strength Steel Joints in the As-Welded, Post-Weld-Treated and Repaired Conditions in a Typical Ship Structural Detail

Weld quality and life extension methods of welded details in ship structures made of high-strength and ultra-high-strength steels are of high importance to overcome the issues related to the fatigue characteristics of welded high-strength steels. The current work experimentally and numerically investigated the fatigue strength of a longitudinal stiffener detail, typically present in the bulkhead connections of ship hull. Two high-strength steel grades, namely EQ47TM and EQ70QT steels, were studied in welded plate connections using gas metal arc welding with rutile-cored wires. Fatigue tests were carried out on both small-scale specimens under axial and large-scale beam specimens under four-point bending loading. In addition to the joints tested in the as-welded condition, the high-frequency mechanical impact (HFMI) treatment was considered as a post-weld treatment technique in the fatigue test series. Furthermore, the large-scale beam specimens were pre-fatigued until substantial fatigue cracks were observed, after which they were re-tested after weld repairing and post-weld treatments to investigate the potential to rehabilitate fatigue-cracked ship details. The joints in the as-welded condition were performed in accordance with the current design recommendations. Due to the severe transition from the base material to the weld reinforcement in the joints welded with the rutile-cored wire, a successful HFMI treatment required geometrical modification of weld toe using a rotary burr to avoid any detrimental sub-cracks at the HFMI-treated region. Alternatively, the use of solid filler wires could potentially overcome these issues related to the welding quality. Repaired and post-weld-treated welds performed well in the re-tests, and the fatigue strength was almost twice higher than that of tests in the as-welded condition.

Effect of Longitudinal Stiffeners on Flexural Behavior of Box Beams: A State-of-the-Art Review

Effect of Longitudinal Stiffeners on Flexural Behavior of Box Beams: A State-of-the-Art Review

Numerical Analysis of CFST Column with PBL Stiffeners under Axial Compression

PBL stiffeners, made of thin-walled steel plates with circular openings and welded to the steel tube of a square concrete-filled steel tubular (CFST) column, can improve the combined effect effectively by co-carrying axial compressive forces and confining the concrete core. A numerical simulation study based on the previous test was conducted to study the ultimate strength of the CFST stub column with PBL stiffeners. Finite element models of CFST with different stiffeners were made and verified by the test results of typical failure modes and load–strain curves of specimens. The parameter study was conducted, including PBL stiffener detailing (i.e., material strength, stiffener thickness, opening diameter, and opening spacing). Finally, based on the study and analysis results, an ultimate bearing capacity prediction formula was proposed, which can reasonably predict the bearing capacity of a square CFST column with longitudinal or diagonal stiffeners, while the methods in ACI, BS5400, EC4, AIJ, and DBJ were more conservative.

Experimental and numerical investigation on patch loading capacity of longitudinally stiffened hybrid titanium-clad bimetallic steel plate girder

Plate girders are important load-bearing components of bridge and industrial structures. Corrosion significantly affects durability and service life of plate girders. Bimetallic steel consisting of corrosion-resistance metal and metal with superior mechanical properties provides an engineering solution for the mitigation of corrosion. The titanium-clad bimetallic steel (TCBS) was innovatively introduced into the plate girder as the web to solve the corrosion issue, where the nonlinear resistance performance and failure mode of a longitudinally stiffened hybrid TCBS plate girder under patch loading were investigated experimentally. The test results prove that the longitudinally stiffened hybrid TCBS plate girder has stable load-bearing performance, which is similar to that of the conventional mild steel plate girder. Effects of the shape and magnitude of the initial geometric imperfection on the resistance behavior of the longitudinally stiffened hybrid TCBS plate girder were investigate numerically. A parametric study on the effects of the material properties, longitudinal stiffener location, relative flexural rigidity of the longitudinal stiffener, web panel aspect ratio, and web height-to-thickness ratio on the resistance and critical buckling behaviors of a longitudinally stiffened hybrid TCBS plate girder was performed. Considering the strain strengthening properties of TCBS, the ultimate resistance and ductility of longitudinally stiffened hybrid TCBS plate girders can be significantly improved without affecting the buckling performance. The effect of key parameters on the longitudinally stiffened hybrid TCBS plate girder is consistent with that of the conventionally stiffened mild steel plate girder. Therefore, it is a feasible solution to apply TCBS to the plate girder web, which performs a beneficial effect on the durability of the plate girder.

Web Bend-Buckling of Steel Plate Girders Reinforced by Two Longitudinal Stiffeners with Various Cross-Section Shapes

This work performs an investigation into the optimal position of two longitudinal stiffeners with different cross-section shapes such as open section (L-shaped and T-shaped) and closed section (rectangular and triangular shapes) shapes of stiffened plate girders under bending loading through an optimization procedure using a gradient-based interior point (IP) optimization algorithm. The stiffener optimum locations are found by maximizing the bend-buckling coefficient, kb, generated from eigenvalue buckling analyses in Abaqus. The optimization procedure efficiently combines the finite element method and the IP optimization algorithm and is implemented using the Abaqus2Matlab toolbox which allows for the transfer of data between Matlab and Abaqus and vice versa. It is found that the proposed methodology can lead to the optimum design of the steel plate girder for all stiffener cross-section types with an acceptable accuracy and a reduced computational effort. Based on the optimization results, the optimum positions of two longitudinal stiffeners with various cross-section shapes are presented for the first time. It is reported that the optimum locations of two longitudinal stiffeners with open cross-section shapes (T- and L-shaped) are similar to that of flat cross-section, while the optimum positions of two longitudinal stiffeners with closed cross-section types (rectangular and triangular sections) are slightly different. One of the main findings of this study is that the bend-buckling coefficient of the stiffened girder having stiffeners with triangular cross-section shape is highest while that with flat cross-section shape is lowest among all considered stiffener types and this latter case has minimum requirement regarding the web thickness.

Patch loading resistance of slender plate girders with multiple longitudinal stiffeners

AbstractThere is currently no reliable and simple design method available in international literature for the determination of the patch loading resistance of slender plate girders having multiple longitudinal stiffeners. The current research focuses on the patch loading resistance of girders having multiple longitudinal stiffeners. An advanced numerical model is developed and verified by own laboratory test results. A numerical parametric study is executed to investigate the load‐carrying capacity of girders having typical bridge geometries. Analysing the numerical simulation results, the structural behaviour obtained is classified based on the stiffener stiffness. Effect of the different geometrical parameters on the patch loading resistance is evaluated with special focus on the stiffener stiffness and distance between the longitudinal stiffeners. The failure modes depending on stiffener stiffness are investigated and the local buckling type failure is characterised by minimum stiffness. For this specific failure mode, an improved design method is developed, giving reliable resistance within the analysed parameter range. The presented resistance model is consistent with the design philosophy of EN 1993‐1‐5. The applicability of the improved design equation has been investigated for multiple stiffener places in unequal distances, which is the common case in praxis, and for bending and transverse force (M–F) interaction.

Shear flow capacity of stiffened flanges in steel box girders

The purpose of this paper is to model the shear flow capacity of stiffened flange in a steel box girder. The present study uses an energy-based variational approach to analyze the steel box girder. A new parameter is introduced that is strongly correlated to the shear lag response of stiffeners to flanges. This parameter is named as shear flow parameter. The shear flow parameter decreases with increasing stiffener area to flange area ratio. Along with increasing the stiffness of the flange, stiffeners also reduce the shear flow capacity of the flange plate. It is observed that the reduced shear flow capacity causes more shear lag in the flange, increasing the stress at the web-flange junction. As a result of a high percentage of longitudinal stiffeners, steel box girders have a small effective width ratio, high negative shear lag effect, and significant deflection. This approach is in close agreement with experimental results, finite element results and theoretical results.

Considerations about the fatigue strength assessment of local cut-out in the double bottom floor

The aim of this paper is to obtain the effect on the fatigue strength assessment of the different geometrical variables involved in the design of the local cut-out, resulting from the intersection between the longitudinal stiffener and the double bottom floor of a bulkcarrier vessel; a common ship structural detail considered to be prone to fatigue failure. Based on finite element models, different combinations between cut-out geometries and longitudinal stiffeners, in terms of size and shape, are analysed to establish the structural behaviour, expressed in accordance with the location and value of hot spot and fatigue life. A novel and valuable scantling tool, known as fatigue sensitivity curves, is developed that determines fatigue life under loading conditions that differ from the design load and reduce fatigue strength. A series of experimental tests are carried out to investigate the fatigue crack growth and validate the numerical results, from the most effective combination of the local weight determination.