Steel Plate Elements Research Articles

Preliminary Investigation on Steel Jacketing Retrofitting of Concrete Bridges Half-Joints

An innovative strengthening system for dapped-end beams is studied numerically and experimentally in this paper. The system is developed for the half-joint regions of bridge beams also commonly called “gerber saddles”, but it can be adapted to different scenarios. The strengthening system consists of two steel plates that are clamped on both sides of the webs of the beams by means of bolts. The purpose of the system is to transfer the highest possible amount of shear from the concrete webs to the steel plate elements reducing the resistance demand of the concrete half joint. Shear is transferred by friction from concrete to steel plates. The system is designed to be applied on existing bridges without heavy work interesting the carriageway, therefore reducing the interference with the traffic. Some interesting considerations emerge from the study, including the influence of the flange web connection on the structural behavior and the possible presence of brittle failure mechanisms that are difficult to model numerically using f.e.m. simulations.

Lateral Cyclic Performance of Hybrid Fabricated Beam‐Columns

AbstractIn this paper, a high‐capacity fabricated hollow section is proposed as a lightweight replacement for concrete‐filled composite members which are commonly used as beam‐columns in seismic zones. The lateral cyclic performance of the fabricated hollow beam‐column comprising of mild steel plates (grade 250) and high strength steel (HSS) tubes (grade 750) is investigated. A finite element model is developed and validated against available experimental data. To incorporate the cyclic hardening and softening of both steel materials, a combined plasticity model obtained from low‐cycle material tests is incorporated in the finite element model. A comprehensive sensitivity analysis is undertaken to propose an optimum slenderness design for the thin‐walled steel elements with ductile failure. While the high strength steel tube elements can significantly increase the axial and lateral capacity of the hybrid section, the cyclic failure mechanism is governed by mild steel plate elements, rather than a sudden failure in the high strength steel tubes.

A simplified method for calculating non-uniform temperature distributions in thin-walled steel members protected by intumescent coatings under localized fires

This paper presents a method to calculate the non-uniform temperature field of steel members protected by intumescent coatings under localized fires. In this proposed method, the steel member is divided into a number of segments along the length according to the localized fire temperature field, and each segment divided into plate elements with different surrounding fire temperatures. The temperature of each plate element is assumed uniform and is calculated by the lumped mass equation with the thermal conductivity of intumescent coatings approximated using a three-stage thermal conductivity model. Heat conduction between different steel plate elements is ignored. Comparisons of steel temperature results between measured results and the proposed simplified temperature calculation method show very good agreement in temperature distributions along the steel member length, in the cross-section and detailed temperature–time relations at critical and high temperature locations, with differences in calculated and measured average temperatures in different segments being less than 7.2 %. Comparisons of load carrying capacities of axially-loaded steel members using measured temperature distributions and calculated temperature distributions show small (<6%) differences.

Modelling and slenderness design of high-capacity hybrid beam–columns under lateral cyclic loading

The ‘dual-steel’ concept involves combining High-Strength Steel (HSS) and mild steel to control the energy dissipation and overall failure of structures under seismic loads. In this study, the performance and design of a hybrid hollow beam–column were investigated with a focus on the seismic resistance. The hollow section was fabricated with mild steel plates (grade 250) and HSS tubes (grade 750) and can be used as a lightweight replacement for conventional composite members. A finite-element (FE) model was developed and validated against available experimental data. To consider the cyclic softening of HSS tubes, a combined kinematic and isotropic plasticity model was incorporated into the FE model. The cyclic performance of the hybrid hollow sections was compared with that of equivalent concrete-filled square composite members, and the strength and weight reduction benefits were assessed. Furthermore, considering the current and modified slenderness limits, a sensitivity study was performed on the section geometry. An optimum design for the section geometry was proposed, in which the HSS tube elements significantly increase the axial and lateral capacities of the hybrid section and the mild steel plates provide the required ductility to mitigate seismic deformations. The overall failure mechanism of this design is governed by mild steel plate elements, rather than a sudden failure initiated in the HSS tubes.

SEISMIC RESPONSE OF REINFORCED CONCRETE FRAMES WITH STEEL PLATE SHEAR WALLS

This study aimed to evaluate the effect of using steel plate shear walls (SPSWs) on the earthquake response of reinforced concrete (RC) moment resisting frames. For this, two types of RC frames, namely, ductile and nominally ductile RC frames were used. Each frame structure had five storeys and three-bays. The first storey height was 4 m while the height of the other storeys was 3 m. To upgrade the performance of the existing structures under seismic actions, a special unstiffened SPSW system was incorporated into the middle-bays of each frame. SPSWs consist of an infill steel plate, horizontal and vertical boundary elements such as beams (as HBEs) and columns (as VBEs). The structures were modeled analytically using a finite element method and evaluated by both nonlinear static (pushover) and time history analyses. In the pushover analysis, the first mode load distribution and uniform load distribution were used. In the dynamic time history analysis, a set of ground motion records was employed. As a seismic hazard level, 2% probability of exceedance in 50-year period was taken into consideration. The seismic response of the ductile and nominally ductile RC frames with and without SPSWs was examined comparatively. The results indicated a considerable enhancement in the earthquake performance of both the ductile and the nominally ductile RC frame structures with SPSWs.

Minimum life-cycle cost-based optimal design of yielding metallic devices for seismic loads

The yielding metallic devices have been used to improve the performance of building structures at design level intensities. They dissipate large levels of vibration energy through yielding of disposable steel plate elements but they may also enhance acceleration response related damage of mechanical and electrical components. This paper addresses the optimal design of these devices that minimizes the expected life-cycle object cost considering the story drift and acceleration related damages over the entire spectrum of seismic intensities that can occur on a building site. Genetic algorithm is used to calculate the optimal design parameters of the devices. The uncertainties associated with the frequency of occurrence of earthquakes of different intensities and random characteristics of the structural response are included in the life-cycle failure cost and the object cost calculations. It shown that these devices can be used effectively to reduce the overall life-cycle object cost and can be considered as good protective investment for structural designs in seismic regions.

A study on time-variant corrosion model for immersed steel plate elements considering the effect of mechanical stress

In this study, the effect of low levels of elastic stress on corrosion behavior of Q235B steel in an aerated 3.5% NaCl solution was investigated through measurements of linear polarization resistance (LPR), potentiodynamic polarization characteristics and electrochemical impedance spectra (EIS). Through theoretical analysis and experimental results, new corrosion models which can distinguish the effect of mechanical stress on the corrosion process of actual marine structures have been respectively proposed on the basis of three representative existing corrosion models. The effect of corrosion models on lifetime assessment was studied by employing a steel plate element subjected to the combined effects of corrosion and mechanical stress. Analytical expressions have been obtained for the structure's lifetime, which is identified with the time when the stress reaches the yield level. An example was presented to demonstrate the combined effects of corrosion and elastic stress on the lifetime assessment of marine structures.

Elevated temperature mechanical properties of hollow flange channel sections

The fire performance of cold-formed steel members is an important criterion to be verified for their successful use in structural applications. However, lack of clear design guidance on their fire performance has inhibited their usage in buildings. Their elevated temperature mechanical properties, i.e., yield strengths, elastic moduli and stress–strain relationships, are imperative for the fire design. In the past many researchers have proposed elevated temperature mechanical property reduction factors for cold-formed steels, however, large variations exist among them. The LiteSteel Beam (LSB), a hollow flange channel section, is manufactured by a combined cold-forming and electric resistance welding process. Its web, inner and outer flange elements have different yield strengths due to varying levels of cold-working caused by their manufacturing process. Elevated temperature mechanical properties of LSBs are not the same even within their cross-sections. Therefore an experimental study was undertaken to determine the elevated temperature mechanical properties of steel plate elements in LSBs. Elevated temperature tensile tests were performed on web, inner and outer flange specimens taken from LSBs, and their results are presented in this paper including their comparisons with previous studies. Based on the test results and the proposed values from previous studies and fire design standards, suitable predictive equations are proposed for the determination of elevated temperature mechanical properties of LSB web and flange elements. Suitable stress–strain models are also proposed for the plate elements of this cold-formed and welded hollow flange channel section.

Analysis and modelling of CFT members: Moment curvature analysis

The evaluation of the ultimate behaviour of Concrete Filled Tubular (CFT) members subjected to non-uniform bending moment is the main objective of this work. To this aim eight experimental tests have been performed at the Materials and Structures Laboratory of the Department of Civil Engineering of Salerno University. In particular, Square Hollow Section (SHS) CFT members have been investigated under monotonic loading conditions. The three point bending scheme is adopted for testing specimens, where an hydraulic actuator is used for the transmission of the transverse load at midspan under displacement control and an LVDT is used to measure the corresponding maximum transverse displacement. In addition, longitudinal deformations along the cross section perimeter have been measured by means of strain gauges, aiming to the experimental evaluation of moment–curvature relationship.This paper presents the structural details of the tested specimens and the corresponding experimental results. In addition, a fibre model able to predict the ultimate response of CFT members is also presented and compared with the experimental results. The presented fibre model accounts for all the effects influencing the ultimate behaviour of composite members, such as local buckling, confining effects on concrete, bi-axial stress state of the steel plate elements constituting the hollow profile and hardening of its corners due to cold forming process.The comparison between experimental and numerical results shows a good agreement pointing out the accuracy of the proposed fibre model.

Delivering the Emirates Air Line, London, UK: design and construction of the steel main towers

This paper presents the design, fabrication and erection process of the three main towers of the Emirates Air Line cable car, which spans the River Thames in London, UK. The towers consist of geometrically complex arrangements of a circular hyperboloid shaft topped by a tapering elliptical hyperboloid head. The shafts are formed of interlocking, alternatively and differently pitched, spiralling, doubly curved, structural steel plate elements of varied typologies. The paper presents the extraordinary technical demands including the plate forming process, the complex array of loadings, the nature of the wind responses investigated including impacts of aerodynamic effects from cyclic wind loading, specific requirements for advanced connection stiffness modelling to ensure the extremely tight movement criteria, the challenges of erection over the river Thames and the details of site assembly to tight tolerances. This paper is one of a series of four which describe the delivery of the Emirates Air Line project.

Shear Capacity of Steel Plates with a Square Opening

Steel plate elements are frequently encountered in structural applications, where thin plates are susceptible for local buckling at low loads, while thick plates may reach their strength limit. An opening of any size and shape on such structural plates may significantly affect the stiffness, strength, and the failure characteristic of the entire plate. The objective of this study is to quantify the shear capacity of plates containing a centrally placed square opening. The finite element method based numerical investigation considered the behavior of simply-supported rectangular steel plates, with and without a square opening and subjected to in-plane shear loading, experiencing buckling, post-buckling, and yielding until failure. The model employed representative material model, initial geometric imperfections and large deflection analysis. The investigation established the shear strength reduction factors due to opening of different parametric dimensions, and compared such results with the reduction factors based on the current cold-formed steel design code provisions. This paper establishes an enhanced shear strength reduction factor design equation, incorporating the impact of a centrally located square opening, for the shear capacity of un-stiffened steel plates.

Stiffened plates of rectangular industrial ducts

This paper deals with the design of steel plate elements of rectangular industrial ducts. Because of the practical aspect ratios and the stiffener arrangements, such a plate element is often treated as a long plate (one way slab), fixed supported at the edges and subjected to transverse pressure. The design pressure and the deflection limit determine the plate thickness and the stiffener spacing. Current design practice considers the geometrical nonlinearity, however, uses the strength criterion of first yield. This investigation postulates that consideration of partial yielding of the plate may result in an economical design option, while meeting the serviceability criterion. The study is based on nonlinear finite element analyses of long plates subjected to increasing transverse pressure. Dimensionless parameters that characterize the behavior of such plates were identified and varied in a parametric study. Based on these analyses, design equations have been established for plate thickness and for stiffener spacing corresponding to three different scenarios namely; 0%, 16.5%, and 33% of through thickness partial yielding of the plate. Results show that allowing for 16.5% yielding results in 50% increase in stiffener spacing, at the expense of about 40% increase in deflections. Partially yielding plates can satisfy the serviceability limits states and can lead to economical stiffened plate systems for large rectangular industrial ducts.

Čelični plošni elementi opterećeni u svojoj ravnini: faktori izbočivanja i kritična naprezanja

Čelični plošni elementi opterećeni u svojoj ravnini: faktori izbočivanja i kritična naprezanja

Analysis of side-plated reinforced concrete beams with partial interaction

Existing reinforced concrete (RC) beams can be strengthened with externally bolted steel plates to the sides of beams. The effectiveness of this type of bolted side-plate (BSP) beam can however be affected by partial interaction between the steel plates and RC beams due to the mechanical slip of bolts. To avoid over-estimation of the flexural strength and ensure accurate prediction of the load-deformation response of the beams, the effect of partial interaction has to be properly considered. In this paper, a special non-linear macro-finite-element model that takes into account the effects of partial interaction is proposed. The RC beam and the steel plates are modelled as two different elements, interacting through discrete groups of bolts. A layered method is adopted for the formulation of the RC beam and steel plate elements, while a special non-linear model based on a kinematic hardening assumption for the bolts is used to simulate the bolt group effect. The computer program SiBAN was developed based on the proposed approach. Comparison with the available experimental results shows that SiBAN can accurately predict the partial interaction behaviour of the BSP beams. Further numerical simulations show that the interaction between the RC beam and the steel plates is greatly reduced by the formation of plastic hinges and should be considered in analyses of the strengthened beams.

Tests and models for engineered wood product connections using small steel tube fasteners

Laminated Strand Lumber (LSL) is a type of engineered wood product widely used as a substitute for sawn structural lumber. This is because LSL can be manufactured to have superior mechanical and physical performance to competing products, including high resistance to splitting, high strength and dimensional stability. The authors studied connections in LSL with behaviour of similar connections in sawn Spruce lumber as a benchmark. Proneness to splitting is the Achilles heel of most wood-based construction materials and especially products like sawn lumber and glued-laminated-timber. This characteristic makes it especially difficult to make connections that are mechanically efficient. However, when constructing with LSL it is possible to create connections that not only have desirable response characteristics, but also achieve labour efficiencies. The particular type of connection studied by the authors uses small diameter steel tube fasteners inserted in tight-fitting holes in conjunction with steel plate elements located in slots in ends of joined members and links them together. Tube fasteners are driven perpendicular to the axes of wood members and pass through both those members and steel link elements. Tests were conducted under static tensile loads with multiple-fastener arrangements obeying spaced and end distance rules typical for solid bolts in sawn softwood lumber. The response was highly ductile and failure occurred mainly in the fasteners. Consequently the so-called European Yield Model (EYM) for doweled timber connections yields good predictions of connection strengths. A detailed finite element analysis was also performed to assist interpretation of test results and validate predictions from the EYM beyond the range of test data. The finite element model was developed using the ABAQUS software and results from that model agreed closely with experimental findings in both qualitative and quantitative aspects.

Use of Fiber-Reinforced Polymer Composite Elements to Enhance Structural Steel Member Ductility

An innovative use of fiber-reinforced polymer composite materials to control the manifestation of local buckling in a steel section during plastic hinging is discussed in the present work. This discussion focuses on a technique wherein the constituent plate components in a steel I-shaped cross section are braced against local plate buckling modes through the imposition of thin longitudinal strips whose function is to enforce a nodal line along a plate element. This work demonstrates that such an approach increases the critical load for individual steel plate elements and helps to constrain plastic flow for these same elements so that the structural ductility of the overall cross section is enhanced. The research work discussed herein is analytical in nature. Detailed nonlinear finite element models are created using traditional techniques implemented on the commercially available software system ADINA. Specifics pertaining to bond-line response are not treated.

Effects of plate slenderness on the ultimate strength behaviour of foam supported steel plate elements

Plate elements in fully profiled sandwich panels are generally subjected to local buckling failure modes and this behaviour is treated in design by using the conventional effective width method for plates with a width to thickness (b/t) ratio less than 100. If the plate elements are very slender (b/t > 1000), the panel failure is governed by wrinkling instead of local buckling and the strength is determined by the flexural wrinkling formula. The plate elements in fully profiled sandwich panels do not fail by wrinkling as their b/t ratio is generally in the range of 100 to 600. For this plate slenderness region, it was found that the current effective width formula overestimates the strength of the fully profiled sandwich panels whereas the wrinkling formula underestimates it. Hence a new effective width design equation has been developed for practical plate slenderness values. However, no guidelines exist to identify the plate slenderness (b/t) limits defining the local buckling, wrinkling and the intermediate regions so that appropriate design rules can be used based on plate slenderness ratios. A research study was therefore conducted using experimental and numerical studies to investigate the effect of plate slenderness ratio on the ultimate strength behaviour of foam supported steel plate elements. This paper presents the details of the study and the results.

Ultimate strength of cracked plate elements under axial compression or tension

In addition to corrosion, fatigue cracking is another important factor of age related structural degradation, which has been a primary source of costly repair work of aging steel structures. Cracking damage has been found in welded joints and local areas of stress concentrations such as at the weld intersections of longitudinals, frames and girders. Fatigue cracking has usually been dealt with as a matter under cyclic loading, but it is also important for residual strength assessment under monotonic extreme loading, because fatigue cracking reduces the ultimate strength significantly under certain circumstances. In this paper, an experimental and numerical study on the ultimate strength of cracked steel plate elements subjected to axial compressive or tensile loads is carried out. The ultimate strength reduction characteristics of plate elements due to cracking damage are investigated with varying size and location of the cracking damage, both experimentally and numerically. Ultimate strength tests on cracked steel plates under axial tension and cracked box type steel structure models under axial compression are undertaken. A series of ANSYS nonlinear finite element analyses for cracked plate elements are performed. Based on the experimental and numerical results obtained from the present study, theoretical models for predicting the ultimate strength of cracked plate elements under axial compression or tension are developed. The results of the experiments and numerical computations obtained are documented. The insights developed will be very useful for the ultimate limit state based risk or reliability assessment of aging steel plated structures with cracking damage.

Ultimate shear strength of plate elements with pit corrosion wastage

The aim of the present paper is to investigate the ultimate strength characteristics of steel plate elements with pit corrosion wastage and under in-plane shear loads. A series of the ANSYS nonlinear finite element analyses for plate elements under in-plane shear loads are carried out, varying the degree of pit corrosion intensity and the plate geometric properties. Closed-form design formulae for the ultimate strength of pitted plates under edge shear, which are essentially needed for the ultimate limit state based risk or reliability assessment of corroded structures, are derived by the regression analysis of the computed results. The insights developed from the present study will be very useful for damage tolerant design of plated structures with pit corrosion wastage.

Ultimate shear strength of plate elements with pit corrosion wastage

The aim of the present paper is to investigate the ultimate strength characteristics of steel plate elements with pit corrosion wastage and under in-plane shear loads. A series of the ANSYS nonlinear finite element analyses for plate elements under in-plane shear loads are carried out, varying the degree of pit corrosion intensity and the plate geometric properties. Closed-form design formulae for the ultimate strength of pitted plates under edge shear, which are essentially needed for the ultimate limit state based risk or reliability assessment of corroded structures, are derived by the regression analysis of the computed results. The insights developed from the present study will be very useful for damage tolerant design of plated structures with pit corrosion wastage.