Thin Steel Plate Research Articles

An Analytical Study on Structural Performance Evaluation of Coupled Steel Plate Shear Wall Systems

The purpose of this study was to evaluate the structural performance of coupled steel plate shear walls (SPSWs) using finite element analysis (FEA). SPSW systems have good ductility and energy dissipation capacity and are known to have the advantage that the structure weight can be reduced by using thin steel plate. Although a coupled SPSW system is composed of two SPSW systems and a coupling beam that connects them, there have been almost no studies on the structural performance of coupled SPSW systems. Therefore, in this study, after the effectiveness of the FEA model was verified based on a previous experimental study, parametric analytical studies were conducted using variables such as bay width and coupling beam length. The parametric studies showed that the model with a medium bay width achieved better structural performance and ductility capacity than other models. Also, in comparison to models with different coupling beam lengths, although the model with a short coupling beam showed superior strength, variation of coupling beam length did not result in a significant difference.

Characterising primary fragment in debris cloud formed by hypervelocity impact of spherical stainless steel projectile on thin steel plate

Hypervelocity impact of a projectile on a thin plate generates a debris clouds. Largest chunk (mass) of the projectile material (called primary fragment) in the cloud poses significant ballistic threat to subsequent structure. Primary fragment characteristics (mass, velocity and exit angle) are used in assessing subsequent structure damage potential. Non-dimensional empirical equations are proposed in this paper for estimation of these characteristics. A set of simulations has been carried out using smoothed particle hydrodynamics (SPH) technique of Autodyn. Two stage light gas gun test data has been compared for validation of simulation. Simulation results for spherical projectile made of stainless steel impacting mild steel plate with impact velocity of 2–4 km/s and obliquity of 0°–60° has been analysed. Constants and radicals of the proposed equations are determined by multi variable regression of the simulation data. Comparison of the simulation data with the proposed equations shows a very good fit.

A PVDF-Based Sensor for Internal Stress Monitoring of a Concrete-Filled Steel Tubular (CFST) Column Subject to Impact Loads.

Impact loads can have major adverse effects on the safety of civil engineering structures, such as concrete-filled steel tubular (CFST) columns. The study of mechanical behavior and stress analysis of CFST columns under impact loads is very important to ensure their safety against such loads. At present, the internal stress monitoring of the concrete cores CFST columns under impact loads is still a very challenging subject. In this paper, a PVDF (Polyvinylidene Fluoride) piezoelectric smart sensor was developed and successfully applied to the monitoring of the internal stress of the concrete core of a CFST column under impact loads. The smart sensor consists of a PVDF piezoelectric film sandwiched between two thin steel plates through epoxy. The protection not only prevents the PVDF film from impact damages but also ensures insulation and waterproofing. The smart sensors were embedded into the circular concrete-filled steel tube specimen during concrete pouring. The specimen was tested against impact loads, and testing data were collected. The time history of the stress obtained from the PVDF smart sensor revealed the evolution of core concrete internal stress under impact loads when compared with the impact force–time curve of the hammer. Nonlinear finite element simulations of the impact process were also carried out. The results of FEM simulations had good agreement with the test results. The results showed that the proposed PVDF piezoelectric smart sensors can effectively monitor the internal stress of concrete-filled steel tubular columns under impact loads.

Free vibration of thin rectangular steel plates with geometrically-nonlinear load-displacement behavior

This paper provides means for obtaining the first three significant vibration modes for rectangular plates based on mass participation ratios. A non-dimensional frequency parameter is presented which results into the vibration frequency of rectangular plates at each of these three significant modes. Various aspect ratios and four combinations of boundary conditions at the plate edges are studied. A correlation between the nonlinear load-deformation behavior of the plate and its vibrational behavior is also presented accordingly. It is demonstrated that the vibration frequency of the studied rectangular plates increases significantly upon increasing the applied lateral pressure if the large deformation effects are considered in the analysis. The easy-to-follow method of frequency calculation presented in this paper is useful for assessing the dynamic characteristics of rectangular plates with or without lateral pressure that are subject to vibration.

Investigation on the Effect of Thermo-Mechanical Tensioning on Weld Induced Out-of-Plane Distortions

Fabrication of ship structures involving welding of thin plates, poses a real challenge in limiting the out-of-plane distortion due to buckling. In this study, the effect of thermo-mechanical tensioning (TMT) on minimizing out-of-plane distortion due to buckling in fabrication of stiffened panels has been investigated through experimental and numerical studies. Experiments were conducted using 3-mm-thick plates. The pretensioning of the plates was done along the stiffener welding lines using the shrinkage forces of the tensioning lugs. The lug width was decided based on the possible width of the tensile stress zone due to the welding of stiffener. The tensioning lugs were heated to a temperature so that the plastic deformation of the lugs are minimized thereby required tensioning of the plate could be achieved. Through the implementation of TMT, a noticeable reduction in the out-of-plane distortions were observed. The influence of the sequence of lug removal on the buckling distortions was studied numerically. Fairly good agreement was obtained between experimental and numerical results. The process of TMT was found to be quite effective as an active in-process distortion mitigation technique for fabrication of thin stiffened panels. 1. Introduction Fusion welding is one of the widely used processes of joining. It is extensively used in heavy fabrication industries such as railways, shipbuilding. Fusion welding being a thermal process, it may lead to structural distortions and residual stresses due to nonuniform thermal expansion and contraction of the weld metal and the adjoining the base material. Welding distortions adversely affect the dimensional accuracy of the welded structures and as a consequence act negatively on productivity because of the postweld corrective work that becomes necessary. On the other hand, residual stresses due to fusion welding are the major contributors in crack generation and impairing the fatigue life of the structure. Therefore instead of postweld treatments, in-process active distortion and residual stress mitigation techniques are more beneficial to enhance product quality and productivity. in ship building industry, thin plates are widely used to reduce the weight and thereby cost of fuel (Huang et al. 2004). Welding of these thin plates are more prone to buckling because of their lesser buckling strength. Masubuchi was the first to report about the weld-induced buckling distortions caused by compressive residual stresses in thin plates (Masubuchi 1953). Further Watanabe and Satoh (1958) made an attempt to find out the minimum half wavelength, below which a plate does not buckle, and maximum radius of curvature after buckling for bead welding of thin steel plates. The effect of thermal tensioning on the mitigation of weld-induced buckling distortions was studied by Michaleris and Sun (1997). They employed both finite element analysis and experimental technique in their study. Thermal tensioning was done by simultaneous cooling the bottom of the weld zone by water spraying and heating of the adjacent areas with resistive heating blankets. it was observed that too high a temperature gradient had a detrimental effect on the weld-induced buckling distortions and too low a value of the same resulted in insufficient tensioning. Also it was concluded that the cooling time should be as low as possible for the process to be effective and economic (Michaleris & Sun 1997). Deo and Michaleris (2003) evaluated experimentally the influence of transient thermal tensioning on the reduction of buckling distortions. They also compared the case of Time Temperature Transformation (TTT) at 200 and 250°C with the case of plates welded with only mechanical restraints. It was observed that the buckling distortions cannot be mitigated only with the use of mechanical restraints. The introduction of tensile stresses in the direction of welding through the side heating reduced the compressive residual stresses at the free edges of the plate to a value below the critical buckling stress.

Local buckling of steel plates in concrete-filled steel tubular columns at elevated temperatures

Local buckling remarkably reduces the strength of steel plates in rectangular thin-walled concrete-filled steel tubular (CFST) columns at ambient temperature. This effect is more remarkable at elevated temperature. However, there have been very limited experimental and numerical investigations on the local and post-local buckling behavior of steel plates in CFST columns at elevated temperatures. This paper presents numerical studies on the local and post-local buckling behavior of thin steel plates under stress gradients in rectangular CFST columns at elevated temperatures. For this purpose, finite element models are developed, accounting for geometric and material nonlinearities at elevated temperatures. The initial geometric imperfections and residual stresses presented in steel plates are considered. Based on the finite element results, new formulas are proposed for determining the initial local buckling stress and post-local buckling strength of clamped steel plates under in-plane stress gradients at elevated temperatures. Moreover, new effective width formulas are developed for clamped steel plates at elevated temperatures. The proposed formulas are compared with existing ones with a good agreement. The effective width formulas developed are used in the calculations of the ultimate axial loads of rectangular CFST short columns exposed to fire and the results obtained are compared well with the finite element solutions provided by other researchers. The initial local buckling and effective width formulas can be implemented in numerical techniques to account for local buckling effects on the responses of rectangular thin-walled CFST columns at elevated temperatures.

Thermo-Mechanical Analysis of Activated Tungsten Inert Gas Welding (A-TIG) of Type 316LN Stainless Steel Thin Plates

Abstract In the present study, thermo-mechanical behavior of 316LN stainless steel thin plates during activated tungsten inert gas (A-TIG) welding was investigated using SYSWELD®. A-TIG welding was carried out with more reduced heat input for fabricating 3-mm-thick 316LN stainless steel plates than that of the conventional TIG welding process. Induced transient temperature during welding was measured using a K-type thermocouple. A pulse-echo ultrasonic test was carried out using a 2-MHz probe employing critically refracted longitudinal waves for measuring residual stresses across the weld joint. A digital height gauge was used to quantify the distortion caused during welding. There was a good agreement between the predicted and measured thermal cycles, residual stresses, and distortion. The concentrated heat intensity of A-TIG welding induced higher surface temperature in the weld center, produced a narrow weld bead, and exhibited a sharp temperature gradient at the weld/base metal interface. Peak residual stress and distortion of the A-TIG weld joint were found to be less than that of the TIG weld joint.

Experimental and Numerical Research on Steel Plate Shear Wall with Infill Plate Connected to Beam Only

Steel plate shear walls consist of thin infill steel plates attached to beams, called (horizontal boundary elements, HBEs), and columns (vertical boundary elements, VBEs) in structural steel frames. The thin unstiffened web plates are expected to buckle in shear at low load levels and develop tension field action, providing ductility and energy dissipation through tension yielding of the web plate. HBEs are designed for stiffness and strength requirements and are expected to anchor the tension field formation in the web plates. VBEs are designed for yielding of web plates and plastic hinge formation at the ends of the HBEs. This design approach may result in very large demand on boundary frame members, especially VBEs in most cases. Several methods such as using LYP, perforating the infill plate and omitting connection of infill plate to columns have been proposed to reduce the moment and axial force demands on the VBEs. Study the behavior of steel plate shear walls omitting the connection of infill plate and columns is the main purpose of this research. A classic analysis base on PFI method along with quasi static cyclic experimental study has been performed in order to investigate the behavior of such a system. The results of the experimental study are used to verify numerical models. Behaviors of proposed system (overall capacity and initial stiffness) were compared with those of the conventional SPSWs. Results show that both parameters are reduced in comparison to the conventional SPSWs.

Numerical simulation and experimental validation of residual stress and welding distortion induced by laser-based welding processes of thin structural steel plates in butt joint configuration

Thin plates are extensively used in automotive, shipbuilding, and railway industries. Welding technology is the main assembling method to manufacture thin plate structures because of its high productivity and ease of use. Consequently, residual stress and distortion induced by welding are an inevitable part of the manufacturing process in welding thin plate structures. Relatively low stiffness, and a high amount of heat input are the main reasons for distortion of the welded structures. In order to decrease the heat input, laser-based welding processes that generate highly localized heat with a very high intensity can be a good choice as an alternative to traditional fusion welding. To predict residual stress and distortion in welding thin plate structures, a three dimensional, thermo-metallurgical-mechanical finite element method was developed. The results of three different laser-based welding processes including aspects of Autogenous Laser Welding (ALW), Cold Wire Assisted Laser Welding (CWLAW), and Hybrid Laser-Arc Welding were compared with traditional Submerged Arc Welding (SAW) from both predicted and experimental perspectives. SYSWELD commercial code was used for the simulations in which both large and small deformation theories were employed to predict the residual stress and the final deformation. Experiments were executed to verify the simulation results. A digital high-resolution microscope was used to visualize and measure the weld cross- sectional shape and bead geometry. To measure the residual stress, an X-ray diffractometer was employed. A digital Vernier Caliper and a 3D laser-handheld scanner were used to measure displacement in the z-direction. Moreover, the mechanical properties of welds obtained by different welding processes were also verified by tensile and micro-hardness tests. It was concluded that lower heat input can markedly influence the final distortion of the welded structure. This conclusion can strongly support the idea of replacing traditional arc welding method with a laser-based one. Simulation and experimental results were matched fairly.

Design of Transverse Fillet Welds in the Lapped Joints of Thin Steel Plates

Transverse fillet welds in the lapped joints have been tested and the results compared against the predictions of the North American Specification for the Design of Cold-Formed Steel Structural Members, AISI S100, to address the strength discontinuity in the transverse fillet weld design method at the thickness of 2.54 mm (0.1 inches). The tests performed by the authors and those available in the literature, have not shown any significant discontinuity in the weld strength when the connected plates get thicker than 2.54 mm (0.1 inches). It has also shown that the current design method could be nonconservative for thin plates. Accordingly, potentials to improve strength predictions have been discussed and a modified design method is proposed. The proposed design method is in a good agreement with the experimental results and resolves the inconsistencies in the current design methods. Finally, a reliability analysis based on the available test results has been performed and resistance factors for the proposed design method are provided.

Simulation Study on the Deflection Response of the 921A Steel thin plate under Explosive Impact Load

The Ship cabin would be subject to high-intensity shock wave load when it is attacked by anti-ship weapons, causing its side board damaged. The time course of the deflection of the thin plate made of 921A steel in different initial conditions under the impact load is researched by theoretical analysis and numerical simulation. According to the theory of elastic-plastic deformation of the thin plate, the dynamic response equation of the thin plate under the explosion impact load is established with the method of energy, and the theoretical calculation value is compared with the result from the simulation method. It proved that the theoretical calculation method has better reliability and accuracy in different boundary size.

NUMERICAL SIMULATION ANDCONSTRUCTAL DESIGN APPLIED TO THE STUDY OF ELASTIC BUCKLING IN THIN STEEL PLATES WITH OBLONG PERFORATIONS

ABSTRACTBuckling is an instability phenomenon that can happen when a slender plate is subjected to axial compression loads. In addition, perforated plates are often necessary in the engineering field. Throughout this article, the Constructal Design Method, which is based on the Constructal Theory, has been used to evaluate the influence of the hole on thin steel plates under elastic buckling. For that, the different types of holes analyzed were both transversal and longitudinal oblong. They were all placed in the center of the plate. The geometry of the hole varied according to the degree of freedom H0/L0, which relates the dimensions of each type of different hole. The size of the perforation are varied by means the hole volume fraction (f) parameter, that represents the relation between the volume of the hole and the total volume of the plate (without hole). The main goal is to achieve the greatest critical load for the perforated plates. To do so, the ANSYS software, based on the Finite Element Method (FEM), has been used to numerically analyze the elastic buckling in each case. It has been observed the importance of the geometry when seeking superior performances: through a simple fluctuation of the geometry of the hole, once the volume fraction was kept constant, it was possible to achieve a significant increase on the critical loads. Key words: Buckling; Computational Modeling; Critical Load; Constructal Design.

Fast mean and variance computation of the diffuse sound transmission through finite-sized thick and layered wall and floor systems

A method is developed for computing the mean and variance of the diffuse field sound transmission loss of finite-sized layered wall and floor systems that consist of solid, fluid and/or poroelastic layers. This is achieved by coupling a transfer matrix model of the wall or floor to statistical energy analysis subsystem models of the adjacent room volumes. The modal behavior of the wall is approximately accounted for by projecting the wall displacement onto a set of sinusoidal lateral basis functions. This hybrid modal transfer matrix-statistical energy analysis method is validated on multiple wall systems: a thin steel plate, a polymethyl methacrylate panel, a thick brick wall, a sandwich panel, a double-leaf wall with poro-elastic material in the cavity, and a double glazing. The predictions are compared with experimental data and with results obtained using alternative prediction methods such as the transfer matrix method with spatial windowing, the hybrid wave based-transfer matrix method, and the hybrid finite element-statistical energy analysis method. These comparisons confirm the prediction accuracy of the proposed method and the computational efficiency against the conventional hybrid finite element-statistical energy analysis method.

Behaviour of Steel Plate Shear Wall in Multi Span Moment Frame with Various Infill Plate Connection to Column

Steel plate shear walls consist of thin infill steel plates attached to beams, called (horizontal boundary elements, HBEs), and columns (vertical boundary elements, VBEs) in structural steel frames. The thin unstiffened web plates are expected to buckle in shear at low load levels and develop tension field action, providing ductility and energy dissipation through tension yielding of the web plate. HBEs are designed for stiffness and strength requirements and are expected to anchor the tension field formation in the web plates. VBEs are designed for yielding of web plates and plastic hinge formation at the ends of the HBEs. This design approach may result in very large demand on boundary frame members, especially VBEs in most cases. Several methods such as using LYP, perforating the infill plate and omitting connection of infill plate to columns have been proposed to reduce the moment and axial force demands on the VBEs. The main purpose of this research is to study the behavior of steel plate shear walls with various connection of infill plate to columns in multi span moment frames. A numerical study has been performed in order to investigate the behavior of such a system. The results of proposed system were compared with those of the conventional SPSWs. Results show that reducing the infill plate connection to columns will reduce the axial forces in columns.

Theoretical analysis of fracture in double overlap bonded joints with FRP composites and thin steel plates

The effective stress transfer between the fiber reinforced polymers (FRP) and the steel substrate is crucial for the successful retrofit of existing steel structures with FRP composites. However, there are no standard tests for FRP-to-steel interfaces, wherefore different test configurations have been used in recent years to assess the bond behaviour in these interfaces. The present study shows that the choice of test configuration is highly important and leads to different transfer stresses between the FRP and steel composites and consequently, has a direct influence on the strength of the bonded joint. Therefore, it is important to understand the debonding process that occurs in each test and avoid misinterpretations, erroneous analyses and dangerous characterizations of the interfacial behaviour of these interfaces. The current study presents a new analytical approach for the prediction of the debonding of FRP-to-steel interfaces when double-lap pull or double-strap tests are used.

A Study on the Optimal Placement of Permanent Magnet in Hybrid Magnetic Levitation System for Thin Steel Plate by Electromagnet Installed in the Levitation and Horizontal Direction and Permanent Magnet

Thin steel plates are generally conveyed while in contact with rollers in the conveyance process. This leads to deterioration in the quality of the plate surface, such as flaws and peeling of the plated layer. The researchers in our laboratory have been involved in examining noncontact magnetic levitation control of the conveyance of a rectangular thin steel plate. We proposed hybrid electromagnetic levitation system which consists of electromagnets for levitation and horizontal positioning control and permanent magnets. In this study, the gap, number and optimal position of permanent magnets for suppressing the displacement of a magnetically levitated thin steel plate were investigated using thin steel plates by genetic algorithm. After that we examine effectiveness of optimal position of permanent magnets.

Study on Material Removal Mechanism in EDM Process through Observation of Resolidification of Molten Metal

Material removal from molten metal was observed in order to investigate the material removal mechanism in the electrical discharge machining (EDM) process. Since material removal occurs intermittently not only during the discharge duration but also just after the discharge duration, we hypothesize for the latter case that degassing of the solution gas in the molten metal, which will occur when the molten metal resolidifies, is one of the possible mechanisms of material removal. A thin steel plate was melted by its own Joule heating and material removal occurring during the cooling process was observed using a color high-speed video camera. The temperature distribution on the plate surface was measured from the ratio of the intensities of RGB signals of the video image. It was found that material removal occurred in atmospheric pressure air, whereas it did not occur in vacuum. It was also found that the material removal occurred at a location when the local temperature fell below the melting point of the material. Therefore, the mechanism of the observed material removal was considered to be degassing of the solution gas in the molten metal.

Period Calculation of Thin Steel Plate Shear Walls and the Effect of Connection Type and Degree of Opening on it

Since four decades ago, Steel plate shear wall-SPSW- is a new system resistant to against lateral loads, which has attracted the attention of researchers and designers because of its numerous advantages. The behavior coefficient which has direct dependence on the reflection coefficient is in one way or another based on the period or the natural period of vibration of the resistant system, and considering the short life of this system, there has been no serious study on its period, and in ASCE 7 code, this system has been referred to other systems. In this study, the natural period of vibration of different frames and variant number of floors is examined for thin steel plate shear wall, the results of linear and nonlinear analyses -are compared, and then empirical relationships are presented. Moreover, the effects of connection type and different openings on the period degree of this system were being examined. The results supported the appropriateness of the offered empirical relationship in ASCE 7 code for short and midframes of thin steel plate shear wall in ASCE 7 code; however, it seems that the empirical relationship of tall frames should be increased twice.

Investigation of deformation in laser quenching forming for thin steel plate based on process monitoring

Investigation of deformation in laser quenching forming for thin steel plate based on process monitoring

Experimental Investigation of Polyurea‐Coated Steel Plates at Underwater Explosive Loading

To improve the survivability of ship structures at underwater explosion, thin steel plates coated with polyurea were used to investigate the blast protection effect. During the experimental tests of bare steel plates at different standoff, an appropriate distance was selected as the reference standoff to perform the tests of coated plates. Experimental tests of different coating locations (front versus back) and coating thickness were carried out to study the influencing factors of blast resistance for metal substrate plates. Compared with the bare steel plates, the polyurea coating was found to reduce the deformation of the test plates at blast tests in both cases of the front and back surface locations of the polyurea layer. An increase in the coating thickness also mitigates substantially the deformation of plates. In addition, the properties of the material and the substrate‐coating bond strength may also affect the protective effect of the polyurea coating.