Low Yield Strength Steel Research Articles

A Review on Slit Steel Shear Walls: Development, Implementation, and Performance

Over centuries, natural phenomena have claimed a large number of lives and caused large amounts of damage. However, they were the reason for the development of knowledge and science. In engineering, there is no doubt that earthquakes were the driving force behind many design philosophies and advanced technologies. In this regard, steel plate shear walls (SPSWs) represent one of the technologies employed in both new constructions and existing structures to bolster lateral load resistance. In addition to its high elastic stiffness and strength, SPSWs often experience significant pinching during their hysteretic response unless heavily stiffened. Thus, numerous investigations have been performed recently to enhance the seismic behavior of SPSWs during severe ground shaking. The shear walls of steel plates have been studied in various ways, including stiffened and unstiffened steel plates, low yield strength steel plates, SPSWs perforated with circular holes or vertical slits, steel walls with stiffened and unstiffened openings. A stiffened SPSW panel dissipates significantly more energy than an unstiffened panel, as well as exhibiting a ductile and stable behavior. In view of its high elongation, the SPSW with low yield point has the best damping capacity. It has been demonstrated that steel walls perforated with circular holes have improved energy dissipation, in addition to allowing utilities to pass through their openings. Vertical slits on steel plate shear walls produce an exceptionally full hysteresis loop with improved performances. Slit steel walls (SSWs) can sustain a drift of over 3% while experiencing minimal hysteresis degradation. Additionally, a frame with a SSW can endure up to 6% drift without significant damage, surpassing expected ductility levels of a special moment frame, particularly with efficient slit geometry.

Numerical Analysis of Infill Plate Performance on Steel Plate Shear Wall (SPSW)

Steel Plate Shear Wall (SPSW) is one of the systems that can be used to minimize the effect of earthquakes on buildings. The main energy-absorbing element of the steel plate shear wall system is on the thin steel plate that are located on the center of the steel frame. This thin steel plate is called infill plates. This infill plate will later experience buckling and form a series of tension field action. This paper will prove that the infill plates in the steel plate shear wall system provides significant strength contribution in resisting lateral loads.The analysis was carried out by comparing the strength provided by steel plate shear wall system and simple beam-column steel frame system (without infill plate) with some aspect ratio variation (width per height). The material used for the infill plates was low yield strength (LYS) steel plate of 1.30 mm thick, while the column (vertical boundary element) used WF 400.200.8.12, and the beam (horizontal boundary element) used WF 350.175.7.11. The loading used a monotonic pushover loading of 2% drift (68.8 mm) for each specimen.The analysis result proved that the steel plate shear wall system (frame with infill plates) had significant strength advantage compared to the plateless frame system. The aspect ratio (L/h) on infill plates were also affects the strength of the entire system, where the greater the aspect ratio, the greater the strength. The strength value of the SPSW specimen at 2% drift loading on aspect ratio L/h = 1.00, 1.50, 2.00, 2.50 respectively was 614.95 kN, 634.88 kN, 646.69 kN, and 688.03 kN. Meanwhile, the strength increment percentage between steel plate shear wall systems compared to plateless frame systems in each aspect ratio was 21.67%, 32.39%, 42.48%, and 54.20%.

Compressive performance of an innovative tall pier with composite box section

To improve the seismic performance of tall-pier bridges, an innovative tall pier with a composite box section, composed of four-limb concrete-filled steel tube (CFST) columns and low-yield-strength (LYS) steel plates, was proposed based on the principle of capacity design and the replaceable fuse concept. Both axial and eccentric compression tests were conducted on a series of specimens to study the compressive performance of the composite tall pier. Parametric analysis was performed to investigate the effects of load eccentricity, slenderness ratio, thickness, and yield strength of the LYS steel plates on the compressive capacity using validated finite element (FE) models. The main results indicate that the composite tall pier fails with global bending deformation and elastoplastic instability under axial or eccentric compression. The compressive capacity and initial stiffness of the composite tall pier decrease significantly with an increase in eccentricity or slenderness ratio, and the influences of eccentricity and slenderness ratio are essentially independent. Additionally, the increase in the thickness of the steel plates enhanced the flexural stiffness and compressive capacity, and reduced the uneven loading distribution for the pier. Under axial compression, the pier can be simplified as a CFST lattice column connected by steel beams and LYS steel plates. Finally, practical formulas for the compressive capacity are proposed considering the connection and restraint effects of the LYS steel plates on the CFST columns, which can be used to predict the compressive capacity of the novel composite tall pier.

Investigation of extremely low cycle fatigue behavior of low yield strength steel LY225 under different stress states

• Monotonic tensile and ELCF tests were conducted for LY225 low yield point steel. • ELCF fracture behavior between LY225 steel and Q235 steel was compared. • The LCVGM parameters of LY225 steel were calibrated based on the experimental results. • Buckling and ELCF behavior of LY225 steel dog bone specimen were experimental studied. • The LCVGM can well simulate the post buckling ELCF fracture of dog bone specimen. Low yield point steel is frequently utilized in the energy dissipation components of structures because of its good seismic performance. A low yield point steel LY225 subjected to different stress states is experimental investigated in the study by the monotonic tensile tests and extremely low cycle fatigue tests. The test results demonstrate that LY225 steel shows cyclic hardening characteristic as well as dimple fracture failure mode. In addition, LY225 steel exhibits higher deformability and energy dissipation capacity than Q235 low carbon steel, especially in pure shear stress state, the deformation capacity and extremely low cycle fatigue life of LY225 steel are more than twice that of Q235 steel. The Lode parameter enhanced cyclic void growth model (LCVGM) comprehensively considering the influence of stress triaxiality and Lode parameter can be employed to predict the extremely low cycle fatigue fracture. The LCVGM parameters of LY225 steel were determined based on the experimental results. It indicates that the fracture failure of LY225 steel is free from the influence of Lode parameter due to its good shear performance. The monotonic tensile test and extremely low cycle fatigue test were carried out on the LY225 dog bone specimens, and the fracture failure phenomenon after buckling occurred in the test. The post buckling crack initiation and growth process were numerically simulated by the LCVGM of LY225 steel. The prediction accuracy of the LCVGM was verified by comparing the test results and simulations. This study may provide valuable information about the fracture behavior of LY225 steel under various stress conditions, as well as an effective approach to analyze the post buckling fracture process on the member level.

Development of Timber Buckling Restrained Brace for Mass Timber-Braced Frames

This research presents the development of a mass timber buckling restrained brace (T-BRB) that combines a low yield strength steel core with a mass timber casing to create a new ductile fuse. The T-BRB is an essential element of a mass timber buckling restrained braced frame (BRBF), which is a promising mass timber wood lateral force–resisting system. Critical elements of T-BRB design that are important for good performance include casing stiffness, casing material, number and spacing of bolts, timber spacer and casing gap, steel core yield strength, and friction between steel core and casing interface. Compressive tests on engineered wood blocks using glued laminated timber, laminated veneer lumber, parallel strand lumber, and mass plywood panel (MPP) were conducted to determine elastic stiffness, maximum load, and ultimate displacement. MPP loaded parallel to the wide face of laminations (X-direction) outperformed other materials with respect to high elastic stiffness, which is an important property of the casing because it controls buckling of the steel core. Six 3.66 m (12 ft)–long T-BRBs with a targeted yield strength of 274 kN (61.5 kip) were tested utilizing three T-BRB casing designs with varying MPP lamination layups. A 3.9% strain was achieved under a strain-based loading protocol. For a fatigue-based loading protocol, after two cycles at 2.0% strain, more than 26 additional cycles at 1.5% strain were attained. The hysteresis curves for all six T-BRBs remained stable throughout the tests and the cumulative inelastic deformation exceeded two times the value required by the standard.

Cyclic behavior of an energy dissipation semi-rigid moment steel frames (SMRF) system with LYP steel curved dampers

The use of displacement-dependent steel curved dampers as fuse or interchangeable element in the beam-to-column connection region is one of the newest methods for improving the seismic performance of semi-rigid moment steel frames (SRMF). In the present study, performance of low-yield strength curved dampers in MRSF has been investigated. These dampers are inactive and install in the beam-to-column connection region. Variable parameters of this study involve the damper width (75, 100 and 125 mm), damper thickness (10, 15, 20, 25 and 30 mm) and the damper steel type (SN400YB and LY160). Evaluation of MRSF models were performed using finite element method by ABAQUS. For validation, a MRSF with curve dampers was modeled that had been experimentally tested and reported in previous experimental research and a good agreement was observed. The results show that the use of low-yield strength steel in curved steel dampers, depending on the damper thickness, can lead to an increase in the hysteresis equivalent damping ratio, ductility parameter and total energy dissipated compared to the steel with higher yield stress.

Accurate prediction of shear buckling capacity of low-yield-strength steel considering plastic deformations

Owing to a high plastic deformation capacity, low-yield-strength steel (LYS) shear panel dampers have been widely used in structural seismic engineering. Meanwhile, there is still no effective method to evaluate the shear buckling capacity of LYS shear panel dampers under plastic deformation. Thin-walled cylinders approximated as shear panels are adopted to experimentally analyse the plastic buckling. The effects of the shape aspect ratio and the width-to-thickness ratio on the deformation capacity are discussed. The buckling behaviour is directly judged and analysed by measuring the out-of-plane deformation of the specimens. By analysing different plastic modulus during buckling, it is found that the critical plastic buckling stress can only be predicted accurately when the variable deformation theory incorporated with the stable plastic deformation is adopted. The critical buckling strain of the LYS can be evaluated by the width-to-thickness ratio solely. This study will be of significant value in the analysis of the buckling capacity of LYS in the plastic-deformation range.

Hysteretic Behavior of Composite Vertical Connection Structures used in Prefabricated Shear Wall Systems

An innovative composite vertical connecting structure (CVC) with capacity carrying and energy-dissipating ability is proposed in this study, which could be used in prefabricated composite shear wall structural systems to enhance the resilience and seismic performance of structural system. The CVC structure is mainly composed of three parts, including the connecting zone, the capacity bearing zone characterized by high strength and elastic deforming ability, and the energy-dissipating zone assembled by replaceable metal dampers. The low-yield strength steel and high-strength steel are used, respectively, for the metal dampers in the energy-dissipating zone and the concrete-filled high-strength steel tubes in the bearing capacity zone to enhance the energy dissipation and self-centering abilities of CVC structures. The working mechanism is analyzed and validated through finite element models built in ABAQUS. The hysteretic behavior is simulated to evaluate their performance. First, the metal dampers are designed. The theoretical and finite elemental parametric analysis are carried out. According to the simulation results, the “Z-shaped” metal dampers exhibit better energy-dissipating ability than the rectangular shape, in which the “Z-shaped” metal dampers with 45∘show the best performance. Simultaneously, the results of the models calculated by the finite element method and theoretical analysis work very well with each other. Furthermore, seven FE models of shear walls with CVC structures are designed. Monotonic and cyclic loading simulations are conducted. The failure modes and comprehensive mechanical performance are investigated and evaluated according to their calculated force–displacement curves, skeleton curves, and ductility coefficients. The results indicate that the CVC structure delivered preferable lateral-bearing capacity and displacement ductility. Finally, according to available design standards, the lateral stiffness of CVC structures could be conventionally controlled and some practical design recommendations are discussed.

Experimental and numerical investigation of low-yield-strength (LYS) steel plate shear walls under cyclic loading

Steel plate shear walls (SPSWs) are lateral load resisting systems with a significant energy dissipation potential under cyclic loading. This research performed experimental and numerical investigation of the cyclic behavior of low-yield-strength (LYS) SPSW. Two specimens with 1:3 scale three-story single-bay SPSW with unstiffened infill plates were tested using cyclic loading. The steel plate shear walls had two types of moment-resistant and pinned beam-to-column connections. Also, low-yield-strength (LYS) and high-yield-strength (HYS) steel were used for the infill plates and boundary frames, respectively. The results indicated that the test specimens had good stiffness, high ductility, significant energy dissipation, and stable cyclic behavior. Also, the results revealed that the type of beam-to-column connection affects ductility, strength, and energy dissipation and has a negligible effect on the initial stiffness. In addition, the nonlinear finite element (FE) models were developed to predict the hysteresis behavior of SPSWs. In the FE models, the nonlinear behavior of geometric and materials, large deformations, and initial geometric imperfections were considered. The nonlinear FE models of SPSWs were verified against experimental results. The hysteresis curves, failure modes, and base shear capacity FE models were compared with the experimental results. The numerical investigation showed that the cyclic behavior of the SPSW could be simulated using a simplified FE model. It is demonstrated that rigid and pinned beam-column connection can influence the strength performance and total energy dissipation of an SPSW system and material properties of the infill plate components, especially LYS steel, can further advance the impact of such connection.

Performance of Low-yield Strength Plates in Beam-column Connections against Progressive Collapse

In many studies about progressive collapse in steel moment frames, the effect of connections in all of structural frames has not been investigated. This is while the connections can have a significant impact on structure behavior against abnormal loads. This study highlights the effect of mechanical and geometric properties of beam-column connections in steel moment frames against progressive collapse. For this purpose, variable parameters include beam-column connection type (Welded Flange Plate connection or WFP and Welded Unreinforced Flange-Welded web connection or WUF-W), mechanical properties of beam-column connection (St37 building steel and low-yield strength plates) and the column removal location in different stories (without removing column and removing column on the ground, first and second floors). Three-storey steel frames which are designed to withstand earthquakes are examined. Finite element ABAQUS software is used for simulation. Moreover, the alternative load path method in which the structure response is examined against the column removal is used to evaluate steel frames response against progressive collapse. The results show that the use of low-yield strength steel plates depending on connection type can be efficient in improving the behavior of steel moment frames against progressive collapse.

High ductile fracture of a low-yield-strength steel with a part-through curve crack

Low-yield-strength (LYS) steels possess ultra-high ductility and low yield ratio which indicates a wide prospect of the application for energy absorption. When a LYS steel-based damper or buffer is activated by a seismic wave or a crash impact, the structural integrity usually has a high risk of failure. Hence, the fracture resistance of LYS steels should be a key parameter for their structural design and integrity assessment. Here, we report both an experimental and a numerical investigation on the fracture behavior of an LYS steel with the yield stress of 100 MPa (LYS100), where a part-through corner or surface crack is machined in specimens and the critical loading capacities of the specimens are determined by our experiments. The suitable material parameters of the extended finite element method for LYS100 are determined based on our experimental results, which can be used to describe the fracture behavior of LYS100. Our results show that the fracture toughness of LYS100 can be up to around 1019 N/mm, which is almost twice as high as that of Q235 and one order bigger than that of gray cast iron. These findings will be a great help toward understanding the fracture properties of LYS steels and designing high-performance damping structures.

Feasibility of the evaluation of the deformation capacity of the shear panel damper by FEM

Taking advantage of large plastic deformation of low yield strength steel is beneficial for improving the seismic performance of the shear panel damper (SPD). To pre-evaluate the seismic performance of the SPD by simulations is very important for rapid design. However, the deformation capacity of the SPDs cannot be effectively judged by the finite element method (FEM). Here, SPDs which are designed based on different methods are analyzed and compared by simulations and experiment simultaneously. The stress/strain distribution and the stress/strain concentration factor of all specimens are first analyzed and compared based on simulation results. Furthermore, the deformation capacity of some SPDs is verified by experimental results. The relationship between the stress, or stress concentration factor, and deformation capacity of SPDs are obtained and discussed according to the simulation and test results. Not only is the relationship between the stress concentration factor and deformation capacity established quantitatively, but the optimization design method, which is most favorable for large deformation of the SPD, is also qualitatively analyzed in this research. The research results show that it is helpful for the rational pre-evaluation of the limit performance of the SPD based solely on FEM.

Hysteretic mechanical property of low-yield strength shear panel dampers in ultra-large plastic strain

The low-yield strength steel (LYS) has been a promising material to make shear panel damper in seismic engineering due to the large plastic deformation capacity. To take advantage of the energy absorption ability of the low-yield-strength steel shear panel damper (LYSPD), it is essential to obtain the accurate prediction for the stress-strain relationship of LYS especially for the high plastic deformation. However, most of the existing constitutive models for LYS are based on the plastic strain not more than 6%. Here, an improved constitutive model is developed to describe the plastic behavior in a large range of plastic strain up to 60%. First of all, the large plastic behavior with the necking effect under monotonic tension loading is considered and verified by test. Secondly, together with several constitutive models for describing the shear plastic behavior of LYS with and without consideration of cyclic hardening, the accuracy of these models are verified by the cyclic incremental test results of LYSPD. Moreover, an accurate model is calibrated by using the yield stress evolution of the two-surface theory. The developed model could be used to describe the mechanical properties for large plastic strain and to judge the stability of the structure in improved accuracy.

Ultra-low cycle fatigue performance evaluation of the miniaturized low yield strength steel shear panel damper

Merited as rapid assembly and replacement, the miniaturization design of the low yield strength steel shear panel damper has been attracted more attention of researchers. Functioned as damping structure, enough response displacement realized by large deformation capacity with enough low cycle fatigue life is very important for seismic design. Several types of tests are conducted to clarify the performance of the damper. The deformation capacity and low-cycle fatigue performance of the damper material are investigated through monotonic and constant amplitude cyclic shear tests. The deformation capacity of the actual damper affected by width to thickness ratio is verified by incremental amplitude cyclic shear tests. Combined with the constant amplitude cyclic shear tests of the damper, the failure degradation process from damper material to damper structure is systematically analyzed. According to the seismic design requirement, the deformation capacity of the damper when the fatigue cycle number is between 10 and 30 is discussed in detail. Both the accurate prediction and the simple and rapid prediction on the applicable deformation capacity of the damper are proposed according to the analysis of low-cycle fatigue life. This study provides an in-depth understanding of the damage evolution of a miniaturized damper which plays a significant role in the optimization design and practical application of the damper.

Plastic Behavior of Metallic Damping Materials under Cyclical Shear Loading.

Metallic shear panel dampers (SPDs) have been widely adopted in seismic engineering. In this study, axial and torsional specimens of four types of metallic damping materials, including three conventional metallic steels as well as low yield strength steel 160 (LYS160), were tested in order to investigate the material response under repeated large plastic strain and low cycle fatigue between 10 and 30 cycles. The present study demonstrated that both the deformation capacity and fatigue performance of LYS160 were underestimated by the conversion from the traditional uniaxial tensile test. The main difference in the failure mechanism between LYS160 and the three conventional materials was determined from the scanning electron microscopy data. The dominant failure mode in LYS160 is stable interlaminate slip and not bucking. Our results provide physical insights into the origin of the large deformation capacity, which is an important foundation for the lightweight design of SPDs.

The Lightweight Design of a Seismic Low-Yield-Strength Steel Shear Panel Damper.

The lightweight design and miniaturization of metallic dampers have broad application prospects in seismic engineering. In this study, the superplastic property and the maximum energy dissipation capacity per unit mass of low-yield-strength steel (LYS) are investigated via comparison with those of several common metallic damping materials by tests. Additionally, the boundary constraints of an LYS shear panel damper are studied further. Our experimental results suggest that LYS is an excellent damping material for achieving the lightweight design goal. A novel design of a lightweight damper, having excellent deformation ability and robust mechanical properties, is presented. The findings of this study are expected to be useful in understanding the lightweight design of dampers.

Experimental Evaluation of Hysteretic Behavior of Rhombic Steel Plate Dampers

Rhombic mild-steel plate damper (also named rhombic added damping and Stiffness (RADAS)) is a newly proposed and developed bending energy dissipation damper in recent years, and its mechanical properties, seismic behavior, and engineering application still need further investigations. In order to determine the basic mechanical performance of RADAS, fundamental material properties tests of three types of mild-steel specimen including domestically developed mild-steel material with low yield strength were carried out. Then, a quasistatic loading test was performed to evaluate the mechanical performance and hysteretic energy dissipation capacity of these rhombic mild-steel dampers manufactured by aforementioned three types of steel materials. Test results show that yield strength of domestically developed low yield strength steel (LYS) is remarkably lower than that of regular mild steel and its ultimate strain is also 1/3 larger than that of regular mild steel, indicating that the low yield strength steel has a favorable plastic deformation capability. The rhombic mild-steel plate damper with low yield strength steel material possesses smaller yield force and superior hysteretic energy dissipation capacity; thus they can be used to reduce engineering structural vibration and damage during strong earthquakes.

Hysteresis Characteristics of Shear Panel Damper Using SLY120

Shear panel dampers (SPD) are a type hysteresis damper used in structures to absorb seismic energy whereby damages to the major structural components could be minimized. It dissipates seismic energy by metallic deformation of the panel, welded between two plates called flanges and upper and lower end plates; and fatigue resistance around the welding part. The disadvantage of such dampers is that they absorb seismic energy only when they go through inelastic deformation. To overcome this restriction of hysteretic dampers, low yield strength steel is used as the material for hysteretic damper because low yield point steel has excellent ductility performance. Nonlinear finite element analysis was carried out to predict the large deformation and hysteretic behavior of SPD using low yield point steel (SYP120). The developed nonlinear SPD analysis model was verified with quasi static loading test.

J1010503 高エネルギ吸収型サイスミックタイを設置した火力発電ボイラ構造物の振動低減効果([J101-5]制振(1))

This paper deals with a high energy absorbing seismic tie, which is energy absorbing device installed between boiler and its support structure. In our previous paper, I-section seismic tie as new type has been developed by optimizing the design parameters (sectional height, web thickness and flange thickness), changing its material from current carbon steel SS400 to low yield strength steel LY225. Cyclic load tests using 1/3 scale models of the tie have been done to verify energy absorption of the high energy absorbing seismic tie. In this paper, vibration reduction effects for thermal power boiler structure with the high energy absorbing seismic ties are examined by time history analysis using an analytical model which simulates boiler structural vibration characteristics.

Comparison of three different methods for determination of damage in solid materials

Material failure is most often caused by cyclic fatigue loading. Prior to failure, material damage growth can be observed by means of various methods. Through experimental research, it has been determined that individual methods are appropriate only for specific types of materials and that analysis results also depend on the method of material loading. Therefore, a question is being raised on which method to choose for a specific material and method of loading. For this purpose, the paper presents the results of the damage initiation process and damage growth for high yield strength material Armox 500T, as well as for annealed low yield strength steel 42CrMo4. The measured data on material response are evaluated by means of three different methods which are based on the elastic modulus, plastic strain energy, and maximum stress.Parameters and damage values were obtained from the measurement data by means of various damage evaluation methods. After that, an overview was made of the differences between these methods. The results were used to determine the deficiencies and benefits of each method and the most appropriate method for subsequent tests was selected. The most frequently applied damage identification method, i.e. the elastic modulus method, proves to be inappropriate for high yield strength materials.