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Lüders deformation is one type of discontinuous yielding in ferrite–pearlite steel. The yield-point phenomenon and localized plastic bands are two features of the Lüders phenomenon. It is believed that the yield-point phenomenon is related to the formation of plastic bands, but the correlation between them is unclear. In this study, this correlation was investigated by examining the global and local deformation behaviors in the tension processes of four ferrite–pearlite steels (carbon content, 0.05–0.3%; pearlite fraction, 1.2–32%) via an extensometer and digital image correlation (DIC) technique. The main obtained results are as follows: (1) the degree of yield drop decreased with an increase in the pearlite fraction (the magnitude of the yield stress drop was 8.6–0 MPa), and (2) a plastic band was formed at a certain stress level smaller than the upper yield stress; when the stress level was larger than 92% of the upper yield stress, the upper yield point disappeared.

The goal was to evaluate the hysteretic performance of buckling‐resistant braces with low yield point steel LYP160, the monotonic tensile and cyclic loading tests of LYP160 test specimens were conducted and the cyclic constitutive relationship was obtained. According to the load–displacement curves of the specimens, the low‐yield point steel was characterized by good ductility and energy absorption ability. With consideration of the Chaboche model for the materials, the cyclic hardening parameters of low‐yield point steel were obtained. On this basis, the hysteretic properties of buckling‐resistant braces under cyclic loads were simulated and analyzed. After the analysis and comparison of buckling‐resistant braces specimens with isotropic core plate and segmented variable section core plate, it can be found that: when the conventional buckling‐resistant braces with an isotropic core plate were loaded to L/100, the lateral deformation of the buckling‐resistant brace (BRB) would reach 17 mm. Additionally, serious squeezing could be observed on the lateral restraining members. The conventional BRB would become ineffective due to the accumulation of deformation at both ends of the BRB. When the segmented buckling‐resistant brace was applied, the core plate with variable section would buckle first in the middle area, other parts could continue to consume energy thanks to the action of the limit plate. It would avoid the situation that other areas would be unable to consume energy after the core plate yields at one area first. Under the action of cyclic loads, no stiffness degradation was noted in the segmented buckling‐resistant brace. Segmented buckling‐resistant braces demonstrated superior ductility and energy dissipation capacity. The monotonic tensile and cyclic loading tests of low‐yield point steel LYP160 test specimens were carried out. On this basis, the hysteretic properties of the conventional BRB and the segmented BRB with LYP160 were simulated and analyzed.

Two types of corrugated steel plate shear walls, namely low-yield point (LYP) and convention, are investigated in terms of strengthening reinforced concrete (RC) frames. Within LYP corrugated steel plate shear walls, two layouts are considered: half and full plate. A total of 24 models are considered to assess their performance in the aspect of ultimate strength, stiffness, and mechanical analysis. The objective of this research is to compare and analyze the effectiveness of LYP corrugated steel plate shear walls in enhancing the seismic resistance of RC frames. Based on force analysis and finite element modelling, the equivalent support model is proposed to verify the validity of the models. The deviation was between 1.76 and 14.27%. The findings reveal that LYP corrugated steel plate shear walls demonstrate comparable bearing capacity to conventional methods, with the added advantage of improved ductility. The maximum top displacement increases by 35% and 68% in the case of half and full plate. Although there is minimal variation (9.86%) in stiffness, these characteristics collectively contribute to enhanced seismic resistance and overall performance of the reinforced concrete frames.

Structural damage caused by mainshock can further be aggravated by aftershocks, which can lead to structural collapse. The current practices on the seismic design of structures generally only consider mainshock effects. This manuscript therefore presents the investigation on damage-based yield point spectra (YPS) of a single-degree-of-freedom (SDOF) system under sequential earthquakes. The collected sequence-type ground motions are recorded from 16 earthquake events and classified to four classes. The aftershocks in sequence are scaled according to different relative intensity levels. The modified Park-Ang model, which consists of maximum displacement and hysteretic energy dissipation, is employed to calculate YPS. The effects of period, ductility factor, damage index, site category, aftershock intensity, and structural damping are statistically studied. The results prove that the strong aftershock ground motion has more distinct influences on the YPS. In particular, the yield strength coefficient demand under seismic sequence increases by 10%–50%. The yield strength coefficient demand determined by the damage-based YPS is greater than that determined by the ductility-based YPS—the former is 10%–40% higher than the latter. Finally, the empirical expression of damage-based YPS is established by statistical mean method and regression analysis.

During the last three decades, interest in the application of steel shear walls has increased worldwide. Steel shear walls are used as stiffened and unstiffened walls. One of the main shortcomings of the steel plate shear wall (SPSW) is the infill plate buckling mainly under lateral wind and seismic loads. One of the useful solutions to prevent lateral buckling is the use of walls with corrugated plates. In this research, the behavior of a steel shear wall consisting of two corrugated plates was investigated in the two material cases of the conventional ASTM A36 steel and the low-yield-point (LYP) steel. The use of steel with low yield strength improves the seismic performance of the steel shear wall system. In this study, the effect of the corrugation angle and aspect ratio of the plate were investigated. The results showed that the effect of corrugation angle on the structural parameters of walls with LYP steel is greater than that of walls with A36 steel. By increasing the corrugation angle from 30° to 60°, the elastic stiffness of A36 and LYP walls decreased about 24 and 36%, respectively, and the response modification factor (R u ) of A36 and LYP walls decreased by about 24 and 56%. The corrugation angle has a lower effect on the ultimate strength and energy absorption. Investigating the effect of aspect ratio showed that increasing the aspect ratio improves the seismic performance of the wall.

An efficient retrofitting technique is expected to improve the seismic performance of a lateral force-resisting system without increasing the seismic demand on the structure, which can unfavorably lead to irreparable damages during a seismic event. On this basis, the present study aims to introduce an optimal strategy for seismic retrofitting of steel plate shear wall (SPSW) systems using low yield point (LYP) steel material and to demonstrate its effectiveness through systematic investigations. To this end, detailed nonlinear static, cyclic, and dynamic analyses, as well as fragility analyses, have been performed on single- and multi-story, code-designed as well as retrofitted SPSWs. The aim is to identify the most efficient retrofitting approach and to demonstrate its effectiveness in enhancing the seismic performance and lowering the seismic vulnerability of the system. It is shown that replacing the original, conventional steel infill plate in an SPSW system with an LYP steel plate having twice the original thickness can improve not only the buckling capacity and serviceability, but also the structural performance and seismic response of the system, without increasing the demand on the structure and creating overstrength concerns. Fragility analysis also shows that the vulnerability, as well as probability, of damage to system can be considerably lowered as a result of the implementation of such a retrofitting strategy.

An eccentrically braced composite frame with a low-yield-point (LYP) steel shear link is an efficient energy dissipation system that exhibits good mechanical properties. However, existing experimental studies have not fully demonstrated the superiority and applicability of the structural system. We present a structural mechanics and finite element model analysis of an eccentrically braced composite frame with a vertical shear link. The effect of the design parameters on the seismic performance of the structure is analyzed. First, a theoretical model of the mechanics of the structural system is established to provide a comprehensive description of the key parameters. Then, a finite element model is developed using the computer program ABAQUS to analyze the mechanical and energy dissipation mechanisms. Finally, the beam-to-column stiffness ratio, shear link web thickness, shear link web width and length, and diagonal brace stiffness are analyzed to determine their effects on the mechanical properties of the structural system. Furthermore, some design parameter values are suggested.

To enable rapid recovery of a steel bridge column after an earthquake, a novel tubular-section steel bridge column equipped with low-yield-point (LYP) steel tubular plates in the root replaceable pier is proposed. For the purpose of discussing the seismic behavior of the novel steel bridge column, quasi-static tests and finite element simulation analyses of the specimens were carried out. The effects of parameters such as the axial compression ratio, eccentricity, and thickness and material strength of the tubular plate in the energy-dissipating zone are discussed. Experimental results from seven specimens that were subjected to four failure modes are presented. The damage to the quasi-static specimens is localized to the replaceable energy-dissipating pier. The seismic behavior of the novel steel bridge columns is significantly influenced by the axial compression ratio and eccentricity of specimens. Numerical results show that the high stress area of the specimens is mainly concentrated in the connection zone between the LYP steel tubular plate and the bottom steel plate, which is consistent with the position of the quasi-static specimen when it was prone to fracture. Finally, a calculation formula is proposed to facilitate the capacity prediction of this new steel tubular bridge column under repeated loading.

The microstructural origin of the double yield points of metallocene linear low-density polyethylene (mLLDPE) precursor films has been studied with the assistance of the synchrotron radiation small- and wide-angle X-ray scattering (SAXS/WAXS). It has been shown that the microstructural origin of the double yield points is highly related to the initial orientation of the original precursor film. For less oriented mLLDPE precursor films, the rearrangement of lamellae and the appearance of the monoclinic phase are the microstructural origins of the first yield point. In comparison, for the highly-oriented mLLDPE precursor film, only the orthorhombic-monoclinic phase transition appears at the first yield point. The melting-recrystallization and the formation of the fibrillary structure happen beyond the second yield point for all studied mLLDPE precursor films. Finally, the detailed microstructural evolution roadmaps of mLLDPE precursor films under uniaxial tensile deformation have been established, which might serve as a guide for processing high-performance polymer films by post-stretching.

The article presents a method of determining the yield point, applying calculations based on the Kolmogorov-Sinai (K-S) metric entropy model. Data used in metric entropy calculations was obtained during a static tensile test of the AW-7020 aluminium alloy. The methodology of K-S entropy calculations was presented and illustrated by a selected example from a data collection. Analyzing the results obtained, the values of an arbitrary yield point were compared for R selected samples with the values R