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Numerical evaluation of the hysteretic behavior of concentrically braced frames and buckling restrained brace frame systems ارزیابی عددی رفتار هیسترتیک سیستم های قاب های مهاربندی همگرا و قاب مهاربندی کمانش تاب Mohammad Naghavia,⁎, Rohola Rahnavardb,⁎, Robert J. Thomasb,⁎, Mohsen Malekinejadc a Department of Civil Engineering, Javid Institute for Higher Education of Jiroft, Iran b Department of Civil and Environmental Engineering, Clarkson University, Potsdam, NY, USA c Department of Civil Engineering, Islamic Azad University, Sirjan branch, Iran This paper presents a numerical investigation of buckling restrained brace (BRB) frames (BRBF) and a comparison with concentrically braced frames (CBF). A simplified core-spring finite element model was used to model BRB elements. Four types of CBF (X, V, inverted V, and two-story X) and four types of BRBF (diagonal, V, inverted V, and two-story X) were modeled in ABAQUS. A static nonlinear pushover analysis considering two cyclic loading protocols showed that the buckling restraint allows the BRB elements to undergo significant plasticity without forming plastic hinges, thereby dissipating a proportionally larger amount of energy and delaying yielding in the frame elements. Results indicated dramatic improvements in energy dissipation and ductility in BRBF models as compared to equivalent CBF models. Seismic response modification factors for BRBF models also showed greater values over CBF models. Time-history analysis evaluated the performance of CBF and BRBF under historical earthquake loadings and supported the same conclusions. The best performance was observed for V, inverted V, and two-story X BRBF configurations; the diagonal BRBF configuration performed better than equivalent CBF models, but did not perform nearly as well as the other BRBF models. منبع article_Numerical_evaluation_of.pdf

Behavior of stiffened and unstiffened steel plate shear walls considering joint properties Hong-Chao Guo a,b,n , Ji-Ping Hao c , Yun-He Liu a,b a State Key Laboratory Base of Eco-hydraulic Engineering in Arid Area, Xi′an University of Technology, No.5 Jinhua Road, Xi′an 710048, PR China b Department of Civil Engineering and Architecture, Xi′an University of Technology, No.5 Jinhua Road, Xi′an 710048, PR China c Department of Civil Engineering, Xi′an University of Architecture and Technology, No.13 Yanta Road, Xi′an 710055, PR China article info Article history: Received 23 April 2015 Received in revised form 24 August 2015 Accepted 7 September 2015 Keywords: Shear wall Stiffener Semi-rigid Energy dissipation Spring element abstract Steel plate shear wall (SPSW) systems have dual characteristics, the frame and infill wall action. The connection flexibility of frame joint not only changes the force and moment distribution, but also increases the lateral displacement and weakens the overall stability in SPSW structure. This paper presents the influence of hinged, rigid and semi-rigid connection joints on the behavior of SPSW structures. The bearing capacity, energy dissipation mechanism, failure mode, stress and deformation development process of the semi-rigid composite frame with steel plate shear walls under different stiffener forms were studied using experimental tests and finite element analysis. It was observed that with stiffeners the specimen yield load increased about 20% on the elastic stage, the ultimate bearing capacity of the diagonal stiffener was about 5% larger than the cross stiffener on the plastic stage, but the overall failure modes were basically the same. Additionally, the quantitative indications of the effect of joint stiffness on load carrying capacity were presented Thin-Walled Structures Volume 97, December 2015, Pages 53-62 guo2015.pdf

A numerical study of coupled timber walls with slip friction damping devices Ashkan Hashemi Reza Masoudnia Pierre Quenneville AbstractIn rocking timber structures, the traditional connections such as nailplates may need to be replaced by damping devices to provide the required lateral resistance and dissipate the seismic energy. This study seeks to investigate the seismic behaviour of coupled timber walls with slip friction connections. Slip friction connections present a low damage solution as they do not suffer from stiffness degradation and can be used after a seismic event. The seismic response of the described system is compared to those with equivalent nailplates. Displacement control quasi-static and also dynamic time-history analyses showed that the performance of the systems with friction devices is significantly improved under seismic loading compared to similar systems with equivalent nailplate connections. The systems with nailplates incurred significant inelastic damages while the systems with friction devices exhibited superior performance in terms of strength degradation and absorbed seismic energy. The introduced concept presents a feasible solution for timber structures when a low damage design is targeted. Keywords Timber walls; Cross Laminated Timber; Slip friction; Low damage; Energy dissipation Construction and Building Materials Volume 121, 15 September 2016, Pages 373–385 1-s2.0-S0950061816308996-main.pdf

Effect of Wedge Shape Deflector on Dissipating Energy in Triangular Flip Buckets Original Article, C09 Mona Omidvarinia, S.H.Musavi Jahromi Journal. Civil Eng. Urban. 3(2): 56-61. 2013 Abstract: Ski jumps are a major element of each dam spillway because these are the only structures able to accomplish satisfactory energy dissipation for takeoff velocities in excess of some 20 m/ s. When water flows over spillways or the dam bottom outlets, flow has a height velocity. In such conditions it has a lot of kinetic energy. In order to dissipate this destructive energy, energy dissipater should be constructed. If geology condition in downstream is appropriate, flip bucket can be used, particularly for height dams. This structure to loss kinematic energy is a cheap method and safer than other ordinary energy dissipaters such as hydraulic basins and roller buckets to employ deflector, is one way to increase energy dissipation in this structure. Deflector is a wedge-shaped structure which creates changes in part of flow trajectory. To investigate the effect of deflector on energy dissipation, an experimental setup has been developed in the Hydraulic Laboratory of Shahid Chammran, Iran. In this research program, the 45 degree bucket with 7 cm approach channel at the end of ogee spillway was divided into two trajectories by deflector. Data analysis showed that the clash between these two trajectories increases energy dissipation in flip bucket. Maximum observed energy dissipation was 70.3% that it occurred in the Froude number 6.7, deflector angle of 25 degree and the side with 12-cm-length. Keywords:Energy Dissipation, Flip Bucket Spillway, Deflector, Physical Model منبع: [Hidden Content] دانلود: [Hidden Content] JCEU-C9-2013.pdf

Cyclic Testing of Chevron Braced Steel Frames with IPE Shear Panels Seyed Mehdi Zahrai, School Civil Engineering, the University of Tehran and Research Associate at the University of Ottawa, mzahrai@ut.ac.ir (Received , Revised , Accepted ) Abstract. Despite considerable life casualty and financial loss resulting from past earthquakes, many existing steel buildings are still seismically vulnerable as they have no lateral resistance or at least need some sort of retrofitting. Passive control methods with decreasing seismic demand and increasing ductility reduce rate of vulnerability of structures against earthquakes. One of the most effective and practical passive control methods is to use shear panel system working as a ductile fuse in the structure. Shear Panel System, SPS, is located vertically between apex of two chevron braces and flange of floor beam. Seismic energy is highly dissipated through shear yielding of shear panel web while other elements of structure remain almost elastic. In this paper, lateral behavior and related benefits of this system with narrow-flange link beams is experimentally investigated in chevron braced simple steel frames. For this purpose, five specimens with IPE (narrow-flange I section) shear panels were examined. All of the specimens showed high ductility and dissipated almost all input energy imposed to the structure. For example, maximum SPS shear distortion of 0.128-0.156 rad, overall ductility of 5.3-7.2, response modification factor of 7.1-11.2, and finally maximum equivalent viscous damping ratio of 35.5-40.2% in the last loading cycle corresponding to an average damping ratio of 26.7-30.6% were obtained. It was also shown that the beam, columns and braces remained elastic as expected. Considering this fact, by just changing the probably damaged shear panel pieces after earthquake, the structure can still be continuously used as another benefit of this proposed retrofitting system without the need to change the floor beam. Keywords: IPE shear panel, vertical link beam, chevron braced simple frame, cyclic testing, ductility ratio, energy dissipation, response modification factor. منبع: [Hidden Content] دانلود: [Hidden Content] papers_Zahrai-SCS-Revised_1.pdf

Toward buckling free tension-only braces using slack free connections Seyed Amin Mousavi a, Seyed Mehdi Zahrai a,⁎, Murat Saatcioglu b a School of Civil Engineering, College of Engineering, The University of Tehran, P.O. Box 11155-4563, Tehran, Iran b Department of Civil Engineering, The University of Ottawa, Ottawa KIN 6N5, Canada a r t i c l e i n f o a b s t r a c t Article history: Received 15 July 2014 Received in revised form 25 August 2015 Accepted 28 August 2015 Available online xxxx Keywords: Tension-only brace Buckling free Hysteretic behavior Energy dissipation Seismic behavior Slack free connection This study introduces a slack free connection (SFC) by which pinchingwould be removed fromhysteretic behavior of tension-only braces (TOBs). SFC through its mono-directional behavior, eliminates undesirable pinching of the tension-only bracing and changes it to a reliable lateral load resisting system with high energy dissipation capability. A Matlab/Simulink-based model, called Macro-Simulink model, is developed to simulate hysteretic behavior of TOBs with orwithout SFC. Derived Macro-Simulink model is also able to account for hysteretic behavior of the frame. The frame itself can have either deteriorated or non-deteriorated hysteretic behaviors. The Macro- Simulink model is verified through different techniques including earlier experimental results, explicit finite element modeling, and other pre-verified analytical/numerical tools. It is observed that initial pre-tension load only affects initial stiffness of the TOB and has no contribution on its nonlinear hysteretic behavior. Obtained results of this study indicate that energy dissipation capacity of TOBs with SFC would be improved up to 6 times compared with that of conventional TOBs. Moreover contribution of SFC is more pronounced in the case of frames with highly deteriorated behaviors. As a result TOB with SFC can be considered for retrofit purposes as well. منبع [Hidden Content] دانلود: [Hidden Content] EoGZ7fgV.pdf

Analytical study on cyclic behavior of chevron braced frames with shear panel system considering post-yield deformation S.M. Zahrai and A. Moslehi Tabar Abstract: An analytical investigation is performed on chevron braced frames using the shear panel system (SPS) and verified based on experimental results. This paper aims to determine key issues influencing the cyclic behavior and energy dissipation capacity of this kind of ductile braced frame. An extended analytical model is presented to evaluate the lateral stiffness of the SPSs at different levels of nonlinear deformation. The expressions developed in this model may be used to select the geometric properties of the SPS based on the desired ductility. Finally, the results obtained from testing on five full-scale braced specimens are used to verify the validity of the proposed model. The experimental specimens showed approximately 30% hysteretic damping ratio and their SPSs reached a plastic rotation of about 0.15 rad. Key words: shear panel, inelastic deformation, earthquake, damping, energy dissipation, post-yield behavior, ductility. . دانلود: [Hidden Content] منبع: [Hidden Content] QSN7obHy.pdf

NONLINEAR DYNAMIC RESPONSE AND DUCTILITY REQUIREMENTS OF A TYPICAL STEEL PLATE SHEAR WALL SUBJECTED TO EL CENTRO EARTHQUAKE* P. MEMARZADEH, M. M. SAADATPOUR AND M. AZHARI** Dept. of Civil Engineering, Isfahan University of Technology, Isfahan 8415683111, I. R. of Iran Email: mojtaba@cc.iut.ac.ir Abstract– In the present research, an explicit dynamic analysis is conducted on a typical multistorey Steel Plate Shear Wall (SPSW) designed according to AISC requirements. The SPSW model is subjected to a base earthquake acceleration record to simulate the time history response of the structure. The analysis utilizes a finite element method involving both material and geometric nonlinearities. The energy dissipation behavior and distribution of storey shear over height of the model are investigated through time history response of the system. In addition, this paper proposes a new definition of energy ductility, which can be used in the investigation of the dynamic response of SPSWs. The ductility demand based on the proposed definition as well as shear resistance contribution of the web plate and Vertical Boundary Elements (VBE) of SPSW are evaluated. Keywords– Shear wall, steel plate, dynamic response, transient, energy dissipation, energy ductility دانلود: [Hidden Content] منبع: [Hidden Content] PaperM_2031.pdf

DUCTILITY BEHAVIOR OF A STEEL PLATE SHEAR WALL BY EXPLICIT DYNAMIC ANALYZING P. Memarzadeh Faculty of Civil Engineering, Islamic Azad University, Najafabad Branch, Iran Email: p-memar@iaun.ac.ir, parham_memarzadeh@yahoo.com The 14 th World Conference on Earthquake Engineering October 12-17, 2008, Beijing, China ABSTRACT : AISC-341 provides requirements for designing of SPSWs by means of a capacity-design method in which boundary elements are designed for forces corresponding to the fully yield strength of the web plate. In present research, an explicit dynamic analysis is conducted to a typical multi-storey SPSW designed according to AISC requirements. The SPSW model is subjected to a base earthquake acceleration record to simulate the time history response of the structure. The analysis utilizes a finite element method involving both material and geometric nonlinearities. The energy dissipation and ductility behavior of the structure are investigated through time history response of the system. KEYWORDS: Steel Plate, Shear Wall, Transient, Ductility, Energy Dissipation PaperC_5125.pdf