•A TYRSFB was proposed to esnhance the post-yielding stiffness of the RSFB.•The theoretical top force–displacement curves of RSFB and TYRSFB were derived.•Quasi-static tests and numerical simulations ...were conducted on the TYRSFB.•Influences of steel rod configuration on the performance of the TYRSFB were studied.
The lower post-yielding stiffness of a buckling-restrained brace (BRB) was improved by constructing a two-level yielding BRB by setting an additional unit with a certain stiffness after the yielding of a traditional BRB. In this paper, a pinned steel rod with an initial gap is added at the outside of each buckling-restrained column (BRC) in a rocking steel frame with BRCs (RSFB) to improve the stiffness, lateral carrying capacity and ductility of the RSFB after BRCs yielding, which is named as a two-level yielding RSFB (TYRSFB). This paper studies the seismic performance of the TYRSFB and determines the influence of key constructional parameters of steel rods on structural performance. First, the top force–displacement curves of the TYRSFB are derived. Then, quasi-static tests and numerical simulations are conducted on the TYRSFB and RSFB, and the results show that the proposed TYRSFB can achieve the anticipated seismic performance. Moreover, the numerical simulation results are basically consistent with the calculation results of the proposed theoretical formulas. Finally, parametric studies based on the theoretical formulas and numerical models show that changing the value of the distance between steel rods and the central column, the initial gap, the ratio of the cross-sectional area and the length between the steel rod elastic and energy dissipating portions will influence the structural lateral carrying capacity, ductility and failure mode.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•The hysteretic response curves of the fuse connections subjected to cyclic loading were plump.•The fuse angles can concentrate the inelasticity effectively in a wide deformation range.•The retest ...with replaced angles exhibited a similar performance to the initial test.•The fuse connection achieved an initial stiffness close to that of a typical welded beam-to-column connection.
In this study, an innovative replaceable fuse connection for beam members in moment resisting steel frames was proposed. Steel angles are designed as fuse elements for energy dissipation and post-earthquake replacement. The load carrying mechanism of the connection was explored. In order to examine the feasibility of the notion, a total of six full-scale subassemblies of beam-to-column connections were tested. The test parameters that affect the performance of the fuse connection were studied, and the repairability was validated by a retest specimen with replaced fuse angles. Test results demonstrated that the hysteretic response curves of the test connections subjected to cyclic loading were plump, and the fuse angles can concentrate the inelasticity effectively in a wide deformation range. The novel connections equipped with fuse angles can achieve an initial elastic stiffness close to that of a conventional welded beam-to-column connection. In addition, theoretical equations for predicting the elastic stiffness and resistance of the connection were developed, and their sufficiency was validated by test results.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this study, a hybrid metaheuristic algorithm called Hybrid Tabu Search (HTS) is proposed for the weight optimization of planar steel structures. The effectiveness of HTS lies in improving the ...initial conditions of a tabu search algorithm with a greedy search algorithm and a swap operator used in the phase of section selection. The effectiveness of the proposed method is tested and validated on three different benchmark examples. C♯ software is developed to perform the structural analyses. Numerical results obtained by using HTS showed that the proposed method achieved significantly lighter frame weights in most of the benchmark examples. When the method was examined in terms of computational efficiency, HTS was at a level that can compete with other algorithms examined within this study, although it did not provide a significant advantage.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
AbstractStructures are expected to be robust enough to avoid widespread local failure caused by extreme loading events, so that the complete or disproportional collapse of buildings can be averted. ...In the last decades, numerous studies have been conducted regarding preventing the progressive collapse of structures. In the steel frame tests that have been conducted, two-dimensional (2D) systems have normally been adopted. In addition, in previous studies, a concentrated load applied on a removed column has commonly been substituted for the gravity load from the superstructure; in light of the frame tests conducted by the authors, this may have substantially understated the collapse resistance of steel frames. In this study, two large-scale two-bay by two-bay steel frames were tested under a central column removal scenario subjected to concentrated loading and 12-point loading conditions. Flush end-plate joints were used to bridge over the primary beams and columns, and the secondary beams were connected to surrounding columns and primary beams through double-angle cleat joints. Based on the tests, the load-displacement responses and failure modes of three-dimensional (3D) steel frames were obtained. The individual contributions of collapse-resisting mechanisms, including flexural and catenary action in the respective primary and secondary beams, are discussed in detail. In this way, the influence of 3D frame effects and loading methods on progressive collapse were identified.
•Full-scale shaking table test first conducted on SCMP-BTSF system is reported.•Shear plate walls (SW) is used as replaceable seismic fuse in SCMP-BTSF system.•The SCMP-BTSF test structure displayed ...self-centering behavior and acceptable seismic performance.•Test results show that damage in SCMP-BTSF is consistent with design and only occurs in SWs.•No cracks were observed in concrete floor slabs after shake table tests.
Recent numerical study and cyclic testing results have suggested that the self-centering modular panels (SCMP) offer a promising prefabricated structural panel technology for enhanced seismic performance of beam-through steel frames (BTSFs). Several types of seismic fuse devices, including tension-only braces and slit steel plate shear walls (SWs) for energy dissipation, have been studied for their viability in adoption by SCMP. To further investigate the dynamic response and resilience behavior of this seismic-force-resisting system, shaking table tests have been conducted on a 2-story SCMP-BTSF building model with SWs as seismic fuse device. Two far-field ground motion records with various intensity levels were used in the shake table tests. The presented experimental testing study is the first shaking table test of SCMP-BTSF, which is a newly proposed pre-fabricated structure system with self-centering features. Nonlinear finite element (FE) model was also established to perform time history analysis of the test structure and assist with specimen design. The shake test results show that the structure response under frequent ground motions meets the inter-story drift limit given in Chinese code - GB 50011–2010 (Code for Seismic Design of Buildings, abbreviated as CSDB hereafter). When the hazard level was greater than that of frequent ground motions, the system exhibited flag-shaped hysteresis curves of the story shear as expected. It is observed that the SWs dissipated seismic energy through yielding and buckling of steel slats between slits, while other structural members and PTFs remained elastic. No cracks were seen in the concrete floor slabs after all shake table tests. After replacing SWs, the test structure showed nearly identical dynamic properties and seismic responses to the original test structure.
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•A new probabilistic assessment framework is proposed to evaluate the failure probability of structures under blast loads.•The accuracy and efficiency of the proposed framework is verified by the ...direct Monte Carlo simulation method.•Collapse risk of a 10-story steel frame under VBIED is analyzed.•The effective measures in protecting structures are determined based on the results of reliability analysis.
This study investigates the failure probability of steel frame structures against terrorist attack from Vehicle Borne Improvised Explosive Device (VBIED). A two-step approach is used to evaluate the collapse potential of structures against blast loads. In the first step, the damage degree and responses of structural members under blast loads are determined based on an equivalent single–degree of freedom system. In the second step, the post-blast collapse behavior of steel frame structures is investigated using a 3-D nonlinear macro-based numerical model. To improve the computational efficiency, the failure probability is calculated using subset simulation method cooperated with an advanced Delayed Rejection Adaptive Markov Chain Monte Carlo simulation algorithm. The variability of blast load, vertical gravity load and structural material properties are considered. The computational framework is applied to a prototype 10-story steel frame to study the failure risk against VBIED. The results show that the reliability assessment framework used in this study provides an accurate and more efficient prediction of failure risk of structures against blast loads compared with the direct Monte Carlo simulation method. The framework also presents an approach for determination of effective measures in protecting structures against blast loads.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
► We provided results of experimental study on masonry infilled steel frames. ► Investigations were carried out on different types of masonry infill used in Croatia. ► A new structural solution for ...masonry infill is proposed. ► Comparison between particular structural solutions is provided.
This paper presents results of a part of the Croatian project “Seismic design of infilled frames” and deals with masonry infilled steel frames. The behaviour of steel frames infilled with masonry, commonly used in Croatia, was experimentally investigated under quasi-static cyclic loading. Besides, a new structural solution is proposed. Nine one-bay, one-storey masonry-infilled steel frames with three different masonry infill types: perforated clay blocks (C), lightweight AAC blocks (A) and newly proposed combination of these materials (CA), were built and tested. Proposed combined masonry infill (CA) allowed partial separation of the masonry from the frame at certain drift levels and prevented the infill’s detrimental effects.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
AbstractThe self-centering energy-dissipative (SCED) brace is a new steel bracing member that provides both damping and recentering capability to a structure, while reducing or eliminating residual ...building deformations after major seismic events. Previous SCED brace designs exhibited full self-centering capability over frame lateral deformations ranging from 1.5 to 2.0% of a typical building story height owing to the elongation capacity of the tendons comprising the system. To overcome this limitation, a new enhanced-elongation telescoping SCED (T-SCED) brace has been developed that allows for self-centering response over two times the range achieved with the original SCED bracing system. A prototype design of this proposed system was fabricated and tested quasi-statically and dynamically in a full-scale vertical steel frame. It exhibited full self-centering behavior in a single story frame that was laterally deformed to 4% of its story height. This new T-SCED brace also satisfied standard testing protocols for buckling restrained braces.
This study presents a simple hysteretic model to reproduce the stress–strain relationship of superelastic NiTi shape memory alloys (SMAs). The proposed model explicitly includes the functional ...degradation of SMAs, which has been ignored in earthquake engineering applications. This effect causes a reduction in the transformation stress and accumulation of residual strain. Because SMA devices are mainly used for seismic retrofit and account for a small portion of the structural system, their numerical model should not increase the computational time needed to perform nonlinear dynamic analyses. Computational efficiency can be achieved by representing their stress–strain response in a phenomenological way. Additionally, practitioners who may not have a professional background in materials science can easily manipulate the proposed model for the appropriate reproduction of model parameters such as transformation stress and residual strain. The ability to properly reproduce the experimental stress–strain response is validated for the test results of 65 NiTi SMA specimens. The amount of forward and reverse transformation stress degradation and the amount of residual strain accumulation per cycle, which are observed in the experimental results, are captured with reasonable accuracy in the proposed model. Additionally, the response of SMA braces in a four‐story steel moment frame is modeled using the proposed model to examine the residual story drift of the SMA braced frame under a set of ground motions. At higher intensity levels, the functional degradation of SMA braces increased the residual story drift up to 60% in comparison to the SMA‐braced model without functional degradation.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
