Cumulative Plastic Strain Energy Research Articles

Pseudo-static topology optimization using the evolutionary-type method for reinforced concrete shear walls

For improved ductility in seismic-design reinforced concrete shear walls, a methodology referred to as pseudo-static topology optimization is incorporated to guide the design process. This approach involves a stepwise elimination of elements from the initial structural configuration, under specified conditions such as reciprocating loads, displacement constraints and volume limitations. The primary objective of this optimization is to maximize the structural capacity for energy dissipation. This is achieved by creating a sensitivity analysis based on variations in cumulative plastic strain energy resulting from element deletions. The final optimized topologies exhibit bar structures with exceptional capacity for energy dissipation. These optimized configurations evolve with changes in height–width ratios and axial compression ratios, shifting from structures with uniform energy dissipation to those with a two-level distribution. Furthermore, the orientation of the main bars changes from folded bars on both sides to inclined straight bars, depending on the specific conditions.

Proposal and application of structural soundness monitoring system for the buckling‐restrained brace using steel mortar planks

AbstractA structural soundness monitoring system for building steel structures is effective for a quick inspection just after large earthquakes. A damage‐controlled structure can be monitored effectively because damage is strictly concentrated in energy‐absorbed members, and that, in this case, the physical quantity suitable for monitoring is displacements of those energy absorbed members. Buckling‐restrained braces (also, the BRB using steel mortar planks, BRBSM), one of the energy‐absorption members, can be directly monitored by the monitoring sensor; it will be possible to quickly evaluate the extent of damage and make a prompt decision on the replacement. Focusing on functionality of a structural soundness monitoring system, a damage evaluation method of the BRB using steel mortar planks and its corresponding monitoring system are verified conducting by a cyclic loading test. It is demonstrated that the cumulative plastic strain energy can be estimated approximately using this system, and this system is adapted to a mid‐rise steel building.

Effects of the clearance between the core plate and restraining part on the structural performance of the buckling‐restrained brace using steel mortar planks

AbstractThe clearance between the core plate and the restraining part of the buckling‐restrained brace using steel mortar planks (BRBSM) considerably affects the failure mode and hysteretic characteristics of the brace. A clearance adjustment construction is proposed for the BRBSM which can control the clearance through partially pasting clearance adjustment materials and polishing the mortar plank surface. First, the clearance adjustment construction workflow and quality control are demonstrated, and it is verified that the clearance can be assured by fabricating specimens. Further, the effects of the difference in clearance between the core plate and restraining part on the structural performance of the BRBSM in terms of failure behaviour, increase strength ratio, buckling mode and cumulative plastic strain energy ratio are evaluated by conducting a cyclic axial loading test.

Optimum Strength Distribution for Structures with Metallic Dampers Subjected to Seismic Loading

A key aspect of the seismic design of structures is the distribution of the lateral strength, because it governs the distribution of the cumulative plastic strain energy (i.e., the damage) among the stories. The lateral shear strength of a story i is commonly normalized by the upward weight of the building and expressed by a shear force coefficient αi. The cumulative plastic strain energy in a given story i can be normalized by the product of its lateral strength and yield displacement, and expressed by a plastic deformation ratio ηi. The distribution αi/α1 that makes ηi equal in all stories is called the optimum yield-shear force distribution. It constitutes a major aim of design; a second aim is to achieve similar ductility demand in all stories. This paper proposes a new approach for deriving the optimum yield-shear force coefficient distribution of structures without underground stories and equipped with metallic dampers. It is shown, both numerically and experimentally, that structures designed with the proposed distribution fulfil the expected response in terms of both damage distribution and inter-story drift demand. Moreover, a comparison with other distributions described in the literature serves to underscore the advantages of the proposed approach.

Buckling‐restrained brace with high structural performance

AbstractThe authors have studied the buckling‐restrained brace providing a stable hysteretic characteristic even under high‐strain conditions. The structural performance of the buckling‐restrained brace is represented by the evaluation formula that is the lower limit of the cumulative plastic strain energy ratio. However, as earthquakes are becoming much longer, so it is necessary to research and develop a new buckling‐restrained brace with a higher energy dissipation capacity. In this paper, our past studies are reviewed and the conditions of high‐performance of buckling‐restrained braces extracted. The buckling‐restrained brace considered was tested. As a result, a buckling‐restrained brace with a larger cumulative plastic strain energy ratio is proposed.

Performance Evaluation of Buckling-Restrained Braces Installed in a Mid-Rise Steel Structure

The authors have continuously studied buckling-restrained braces using steel mortar planks (BRBSM). The performance of energy absorption and fatigue against cyclic loading has been evaluated. Although past studies have clarified the structural performance of BRBSM as single member, it is necessary to study not only the performance of BRBSM as single member but also the performance of BRBSM installed in a building structure. In this paper, a frame model of mid-rise steel structure with BRBSM subjected to earthquake motions with various characteristics is analyzed. Comparing the results of the analysis and the past tests, the seismic behavior of a structure is discussed. Especially, the seismic performance of BRBSM installed in the building structure is evaluated. In addition, the seismic performance of two types of BRBSM; basic and developed high-performance types, is compared and evaluated about cumulative plastic strain energy ratio and cumulative fatigue. As a result, the performance capacities of the both types of BRBSM exceed the required values of BRBSM under severe earthquake motions about cumulative plastic strain energy ratio and cumulative fatigue. The basic-type BRBSM has the fatigue capacity against 2 to 5 times severe earthquake motions. The required values of high-performance-type BRBSM are about a half of accumulated fatigue capacity compared with the basic-type one. The high-performance-type BRBSM is applicable against quite many cyclic loadings of low strain amplitude, and able to be used for long-term service.

PREDICTIONS OF STRESS-STRAIN CURVE AND FATIGUE LIFE FOR AISI 316 STAINLESS STEEL IN CYCLIC STRAINING

In this study, experimental observations have been performed to understand the cyclic stress-amplitude response, the cyclic hardening/softening characteristics and the cyclic fatigue properties of AISI 316 stainless steel. Based on the experimental observations, these results are found so that the tested AISI 316 stainless steel possesses cyclic hardening characteristics. The shape of the stable hysteresis loop is symmetrical in tension and compression. The Massing cyclic stress-strain behavior is obviously absent. For the case of the absence of the Massing behavior, the power-law type equation is successfully applied to simulate the shape of the stable hysteresis loop at all applied levels of fully-reversed cyclic straining. For the �������� -based and ���������������� �������� -based fatigue life curves, the typical expressions are developed via cyclic fatigue properties. Besides, a power-law type relationship is also used to develop the fatigue life curve. In contrast to the typical expression, it is found that the power-law relationship is a viable and valid expression in fatigue life predictions. Similarly, the power-law relationship is also used to describe the correlation between the cumulative plastic strain energy W_f with the corresponding the fatigue life cycle N_f. Based on the comparison between the predicted and experiment cycles, it is confirmed that the predicted value of W_f calculated on the basis of the simulated hysteresis loop is capable of yielding reasonable life predictions via the W_f- N_f curve.

Estimation of reliability of structures subject to fatigue loading using plastic strain energy and thermodynamic entropy generation

Plastic strain energy dissipation and thermodynamic entropy generation are explored as means of estimating the likelihood of fatigue crack initiation in reliability assessment of structures. A set of experimental data for aluminum alloy 7075-T651 used in airframe structures are presented to determine the correlation between plastic strain energy dissipation and the thermodynamic entropy generation versus fatigue crack initiation. Cumulative plastic strain energy and thermodynamic entropy generation measured from hysteresis energy and temperature rise proved to be valid physical indices for estimation of the probability of crack initiation. Crack initiation is considered as evidence of fatigue damage and loss of structural integrity. A Bayesian estimation and validation approach is used to determine systematic errors in the developed models as well as other model uncertainties. It was shown that the results from both methods are good predictors of crack initiation and comparable, but the entropy generation method was associated with fewer uncertainties than the plastic strain energy method. Comparisons of the energy-based and entropy-based models are presented and advantages of using one over the other are discussed.

Experimental Study of Hysteretic Steel Damper for Energy Dissipation Capacity

This study aims to evaluate energy absorption capacity of hysteretic steel damper for earthquake protection of structures. These types of steel dampers are fabricated from mild steel plate with different geometrical shapes on the side part, namely, straight, concave, and convex shapes. The performance of the proposed device was verified experimentally by a series of tests under increasing in-plane cyclic load. The overall test results indicated that the proposed steel dampers have similar hysteretic curves, but the specimen with convex-shaped side not only showed stable hysteretic behavior but also showed excellent energy dissipation capabilities and ductility factor. Furthermore, the load-deformation relation of these steel dampers can be decomposed into three parts, namely, skeleton curve, Bauschinger part, and elastic unloading part. The skeleton curve is commonly used to obtain the main parameters, which describe the behavior of steel damper, namely, yield strength, elastic stiffness, and postyield stiffness ratio. Moreover, the effective stiffness, effective damping ratio, cumulative plastic strain energy, and cumulative ductility factor were also derived from the results. Finally, an approximation trilinear hysteretic model was developed based on skeleton curve obtained from experimental results.

Effect of Stress Ratio on the Cumulative Value of Energy Dissipation

Aim of this work is to analyze the stress-strain loops recorded during the study c45 steel under programmable stress for constant amplitude loads of the stress ratio: R = -2.0, R = -1.0 and R = -0.5. The results presented in the paper of cumulative plastic strain energy show that the nature of the relationship ΣΔWpl-N for loads of different values of stress ratio R is similar. Course of changes of relationship ΣΔWpl-N for loads with R = -0.5 and R = -2.0 shows a similar nature and range of changes in the value ΣΔWpl, despite significantly different parameters of load.

Specimen-size dependency and modelling of energy evolution during high-temperature low-cycle fatigue of pressure vessel steel

High-temperature low-cycle fatigue testing was conducted on pressure vessel steel using standard and miniature specimen sizes and the fatigue toughness required for macrocrack propagation was investigated. A definite specimen-size dependency was observed for both the threshold cumulative plastic strain energy and cycles required for macrocrack propagation, which was explained to be influenced by geometric conditions. An analytical modelling prediction was developed that accounted for specimen-size dependency and was successfully applied to predict fatigue toughness to macrocrack propagation.

RESPONSES TO STRONG GROUND MOTIONS AND DESIGN APPROACH OF STEEL FRAMES COMBINED WITH DIAGONAL BRACINGS

Steel diagonal bracing systems combined with moment frame can develop a preferable resistance against earthquakes. Lot of research works have been made on the hysteretic behavior of bracing systems already. However, real responses of these systems to earthquakes have not been made clear yet.In this paper, the distribution of the cumulative plastic strain energy (structural damage) in one story and the damage distribution between stories during an earthquake are made clear and a simple design formula based on the energy balance is proposed.

高性能硬質ポリウレタンフォームにより小型・軽量化した座屈拘束ブレース

The authors developed a buckling-restrained brace for using steel framed houses. The buckling-restrained brace is small-sized and light-weighted with a restraining part of hard polyurethane or mortar. Conducting static and cyclic axial loading tests, elastoplastic and stiffening properties are difined. Specimens with the restraining parts of various restraining forces were fabricated. The authors considere the test data on cumulative ductility factors and cumulative plastic strain energy, and evaluate its performance.

Buckling-restrained brace using steel mortar planks; performance evaluation as a hysteretic damper

The authors developed a buckling-restrained brace that enables increased design freedom at both ends of the core plate and strict quality control while providing stable hysteresis characteristics even under high strains. The buckling-restrained brace can be formed by welding a core plate covered with unbonded material to a pair of mortar-filled channel steels (steel mortar planks) as a restraining part. The use of this approach enables visual confirmation of the status of the mortar filling and also facilitates standardizing structural members and member-by-member quality control. Specimens of a buckling-restrained brace with different steel mortar plank heights are fabricated to adjust the restraining force, along with specimens with different core plate width-to-thickness ratios. The tests were conducted to reveal the hysteretic characteristics of the braces, as well as their cumulative plastic strain energy, elastoplastic properties, and stiffening properties. A performance evaluation formula as well as a buckling-restrained brace design method using the test results is proposed. Copyright © 2006 John Wiley & Sons, Ltd.

An Effective Plastic Strain Component for Low Cycle Fatigue in Metals

Low cycle fatigue tests were performed on several kinds of metal materials, and fatigue life was considered in terms of cyclic hardening property. The cumulative plastic strain energy to failure increases with a decrease in the plastic strain range controlled. The rate of the increase in that amount is influenced by the slip character of materials. Such a difference in the rate is reasonably interpreted by considering the shape of stress-strain hysteresis loop dependent on the slip character. A new criterion for low cycle fatigue was proposed on the basis of the effective plastic strain, εpe which is obtained through an analysis of the profile of the hysteresis loop. A simple equation of εpe·Nf= Constant is established in the life range from 103 to 107 cycles. This means that fatigue failure results from the linear accumulation of the effective plastic strain during strain cycling.

Cyclic Plastic Strain Energy and Low-Cycle Fatigue Strength of Nickel-Chrome Steel

Low-cycle fatigue strength of nickel-chrome steel under various cyclic loading conditions, such as constant strain cycling, constant load cycling with and without mean stress, was discussed in relation to the cyclic plastic strain energy. Main results obtained were as follows : (1) The lowcycle fatigue strength depends on the maximum tensile stress σmax as well as on the cyclic plastic strain energy ; (2) in the case of fatigue-type fracture, a unique relation-ship was found between the maximum tensile stress and the cumulative plastic strain energy to fracture, while in the case of unstable deformation-type fracture, another unique relationship existed between the unstable stress and the total plastic strain energy to the initiation of the cyclic unstable deformation. These relations are approximately shown by two straight lines in a log-log diagram. The line of unstable deformation-type failure lies considerably lower than the extrapolated part of the line of fatigue-type fracture.