• Steel and Composite Structures
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• 제37권3호
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• pp.341-351
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• 2020

Steel plate shear wall with self-centering energy dissipation braces (SPSW-SCEDB) is a lateral force-resisting system that exhibits flag-shaped hysteretic responses, which consists of two pre-pressed spring self-centering energy dissipation (PS-SCED) braces and a wall plate connected to horizontal boundary elements only. The present study conducted a series of cyclic tests to study the hysteretic performances of braces in SPSW-SCEDB and the effects of braces on the overall hysteretic characteristics of this system. The SPSW-SCEDB with PS-SCED braces only exhibits excellent self-centering capability and the energy loss caused by the large inclination angle of PS-SCED braces can be compensated by appropriately increasing the friction force. Under the combined effect of the two components, the SPSW-SCEDB exhibits a flag-shaped hysteretic response with large lateral resistance, good energy dissipation and self-centering capabilities. In addition, the wall plate is the primary energy dissipation component and the PS-SCED braces provide supplementary energy dissipation for system. The PS-SCED braces can provide up to 90% self-centering capability for the SPSW-SCEDB system. The compressive bearing capacity of the wall plate should be smaller than the horizontal remaining restoring force of the braces to achieve better self-centering effect of the system.

• Steel and Composite Structures
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• 제20권4호
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• pp.777-799
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• 2016

One of the major components for performance based seismic design is accurate estimation of critical seismic demand parameters. While nonlinear seismic analysis is the most appropriate analysis method for estimation of seismic demand parameters, this method is very time consuming and complex. Single mode pushover analysis method, N2 method and multi-mode pushover analysis method, modal pushover analysis (MPA) are two nonlinear static methods that have recently been used for seismic performance evaluation of few lateral load-resisting systems. This paper further investigates the applicability of N2 and MPA methods for estimating the seismic demands of ductile unstiffened steel plate shear walls (SPSWs). Three different unstiffened SPSWs (4-, 8-, and 15-storey) designed according to capacity design approach were analysed under artificial and real ground motions for Vancouver. A comparison of seismic response quantities such as, height-wise distribution of floor displacements, storey drifts estimated using N2 and MPA methods with more accurate nonlinear seismic analysis indicates that both N2 and MPA procedures can reasonably estimates the peak top displacements for low-rise SPSW buildings. In addition, MPA procedure provides better predictions of inter-storey drifts for taller SPSW. The MPA procedure has been extended to provide better estimate of base shear of SPSW.

• 콘크리트학회논문집
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• 제17권6호
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• pp.1001-1009
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• 2005

고층 건물의 구조계획에서 벽체의 유용성은 오래전부터 인식되어 왔다. 구조물에서 적절한 위치에 벽체를 배치하며, 벽체는 구조물에 작용하는 횡하중에 매우 효과적으로 저항할 수 있다. 특히 병렬 전단벽 시스템의 구조물의 횡력저항 시스템으로서 가장 선호되는 구조이고 이러한 구조는 커플링보에 의해 벽체가 연결되게 된다. 커플링보는 강도, 강성, 연성 및 에너지 소산능력이 충분한 부재이어야 한다. 이러한 요구들을 만족시키기 위해 FBP를 적용한 철골 커플링보를 제안한다. FBP의 적용 여부를 변수로 하여 총 2개의 시험체를 계획하고 실험을 실시하였다. 이러한 실험 연구를 통하여 FBP를 적용한 철골 커플링보의 장점에 대해 서술하였고, 파괴모드를 제안하였다.

• Earthquakes and Structures
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• 제14권5호
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• pp.411-424
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• 2018

This study explores the inelastic behavior of systems with flexible base. The use of a single degree of freedom system (ESDOF) with equivalent ductility to represent the response of flexible base systems is discussed. Two different equations to compute equivalent ductility are proposed, one which includes the contribution of rigid body components, and other based on the overstrength of the structure. In order to asses the accuracy of ESDOF approach with the proposed equations, the behavior of a 10-story regular building with reinforced concrete (RC) moment resisting frames is studied. Local and global ductility capacity and demands are used to study the modifications introduced by base flexibility. Three soil types are considered with shear wave velocities of 70, 100 and 250 m/s. Soil-foundation stiffness is included with a set of springs on the base (impedance functions). Capacity curves of the building are computed with pushover analysis. In addition, non linear time history analysis are used to asses the ductility demands. Results show that ductility capacity of the soil-structure system including rigid body components is reduced. Base flexibility does not modify neither yield and maximum base shear. Equivalent ductility estimated with the proposed equations is fits better the results of the numerical model than the one considering elastoplastic behavior. Modification of beams ductility demand due to base flexibility are not constant within the structure. Some elements experience reduced ductility demands while other elements experience increments when flexible base is considered. Soil structure interaction produces changes in the relation between yield strength reduction factor and structure ductility demand. These changes are dependent on the spectral shape and the period of the system with fixed and flexible base.

• Steel and Composite Structures
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• 제28권3호
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• pp.309-318
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• 2018

Buckling Restrained Braced (BRB) frames have been widely used as an efficient seismic load resisting system in recent years mostly due to their symmetric and stable hysteretic behavior and significant energy dissipation capacity. In this study, to provide a better understanding of the behavior of BRB frames with various beam-column connections, a numerical study using non-linear finite element (FE) analysis is conducted. All models are implemented in the Abaqus software package following an explicit formulation. Initially, the results of the FE model are verified with experimental data. Then, diverse beam-column connections are modeled for the sake of comparison from the shear capacity, energy dissipation and frame hysteresis behavior points of view until appropriate performance is assessed. The considered connections are divided into three different categories: (1) simple beam-column connections including connection by web angle and connection by seat angle; (2) semi-rigid connection including connection by web and seat angles; and (3) rigid beam-column connections by upper-lower beam plates and beam connections with web and flange splices. Results of the non-linear FE analyses show that these types of beam-column connections have little effect on the maximum story drift and shear capacity of BRB frames. However, the connection type has a significant effect on the amount of energy dissipation and hysteresis behavior of BRB frames. Also, changes in length and thickness of the angles in simple and semi-rigid connections and changes in length and thickness of plates in rigid connections have slight effects (less than 4%) on the overall frame behavior.

• 한국지진공학회논문집
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• 제20권7_spc호
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• pp.553-560
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• 2016

After an earthquake occurred in the Gyeongju, 2016, many low-story buildings have been questioned in terms of the seismic performance since mostly they have been exempted from the seismic design requirement since 1988. In this study, a 3-story moment resisting frame (MRF) building was analyzed and evaluated the seismic performance. Due to the insufficient seismic performance required for the seismic performance levels, three different seismic retrofit schemes were proposed and their seismic performances were re-evaluated. While steel brace and open shear wall retrofit systems mainly focused on the strength retrofit, the VES damper retrofit system is mainly to enhance the energy dissipation capacity of the system and resultes in the increased ductility. The original building and 3 retrofitted buildings were evaluated using the nonlinear static and nonlinear dynamic analyses and suggestions were proposed. Through the analysis of nonlinear time history and push-over using MIDAS/Gen program, damages of the building in terms of top story and average story drift and effect of reinforcement were analyzed.

• Steel and Composite Structures
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• 제22권1호
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• pp.141-159
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• 2016

Commonly in steel frames, steel beam and concrete slab are connected together by shear keys to work as a unit member which is called composite beam. When a composite beam is subjected to positive bending, flexural strength and stiffness of the beam can be increased due to "composite action". At the same time despite these advantages, composite action increases the strain at the beam bottom flange and it might affect beam plastic rotation capacity. This paper presents results of study on the rotation capacity of composite beam connected to Rectangular Hollow Section (RHS) column in the steel moment resisting frame buildings. Due to out-of-plane deformation of column flange, moment transfer efficiency of web connection is reduced and this results in reduction of beam plastic rotation capacity. In order to investigate the effects of width-to-thickness ratio (B/t) of RHS column on the rotation capacity of composite beam, cyclic loading tests were conducted on three full scale beam-to-column subassemblies. Detailed study on the different steel beam damages and concrete slab damages are presented. Experimental data showed the importance of this parameter of RHS column on the seismic behavior of composite beams. It is found that occurrence of severe concrete bearing crush at the face of RHS column of specimen with smaller width-to-thickness ratio resulted in considerable reduction on the rate of strain increase in the bottom flange. This behavior resulted in considerable improvement of rotation capacity of this specimen compared with composite and even bare steel beam connected to the RHS column with larger width-to-thickness ratio.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 봄 학술발표회논문집(II)
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• pp.427-432
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• 1998

The objective of this research is to observe the actual response of low-rise nonseismic moment-resisting reinforced frame subjected to varied levels of earthquake ground motions. First of all, the reduction scale for the model was determined as 1 : 5 considering the capacity of the shaking table to be used. This model was, then, subjected to the shaking table motions simulating Taft N21E component earthquake ground motions, whose peak ground accelerations(PGA's) were modified to 0.12g, 0.2g, 0.3g, and 0.4g. The global behavior and failure mode were observed. The lateral accelerations and displacements at each story and local deformations at the critical portions of structure were measured. The base shear was measured by using specially made load cells. Before and after each earthquake simulation test, free vibration tests were performed to find the changes in the natural period and damping ratio of the model.

• Wind and Structures
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• 제12권2호
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• pp.89-101
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• 2009

The Monte Carlo procedure was used to simulate wind load effects on a light-frame low-rise structure of irregular shape and a main wind force resisting system. Two analytical models were studied: rigid-beam and rigid-plate models. The models assumed that roof diaphragms were rigid beam or rigid plate and shear walls controlled system behavior and failure. The parameters defining wall stiffness, including imperfections, were random and included wall stiffness, wall capacity and yield displacements. The effect of openings was included in the simulation via a set of discrete multipliers with uniform distribution. One and two-story buildings were analyzed and the models can be expanded into multiple-floor structures provided that the assumptions made in this paper are not violated.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.625-628
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• 2000

Recently, composite structural systems have been developed actively due to its structural advantages of combining different materials. The objective of this paper is to investigate the structural behavior of composite connection which consist of steel beams and reinforced concrete columns (RCS). Five 2/3 scale joint specimens with variables mainly consist of shear resisting details, were tested under reversal loads. The results showed that RCS beam-column joints maintain ductility, strength compared to other RCS joints and exhibited excellent energy dissipating capacity when subjected to inelastic deformations under reversal load.