• Title/Summary/Keyword: seismic-performance

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Behaviour of asymmetric building with double variable frequency pendulum isolator

  • Soni, D.P.;Mistry, B.B.;Panchal, V.R.
    • Structural Engineering and Mechanics
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    • v.34 no.1
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    • pp.61-84
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    • 2010
  • Presented in this paper is the behaviour of asymmetric building isolated by the double variable frequency pendulum isolator (DVFPI). The DVFPI is an adoption of single variable frequency pendulum isolator (VFPI). The geometry and coefficient of friction of top and bottom sliding surfaces can be unequal. The governing equations of motion of the building-isolation system are derived and solved in incremental form. The analysis duly considers the interaction of frictional forces in the two principal directions developed at each sliding surface of the DVFPI. In order to investigate the behaviour of the base isolation using the DVFPI, the coupled lateral-torsional response is obtained under different parametric variations for a set of six far-fault earthquake ground motions and criterion to optimize its performance is proposed. Further, influences of the initial time period, coefficient of friction and frequency variation factors at the two sliding surfaces are investigated. The numerical results of the extensive parametric study help in understanding the torsional behaviour of the structure isolated with the double sliding surfaces as in the DVFPI. It is found that the performance of the DVFPI can be optimized by designing the top sliding surface initially softer and smoother relative to the bottom one.

Evaluation of Condensation Resistance of Steel Stud Wall Corner Details in Modular Buildings (스틸 스터드 모듈러 건축물 접합부위의 결로방지성능 개선방안 평가)

  • Oh, Ji Hyun;Yang, Si Won;Cho, Bong Ho;Kim, Sun Sook
    • Journal of the Korean Solar Energy Society
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    • v.34 no.3
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    • pp.107-114
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    • 2014
  • Modular systems are widely used in various building types including housing, dormitory, and barracks. Steel studs have many advantages over other materials as construction components of modular buildings in terms of seismic performance, durability and maintenance. However, steel stud modular systems also have weakness in condensation resistance due to high thermal conductivity of steel. The purpose of this study is to investigate the condensation resistance of steel stud wall corner details in modular buildings by thermal simulation. The condensation resistance was evaluated by temperature difference ratio according to ISO 13788. The result showed that there was little difference between the alternatives of adding cavity and insulation. Separation of interstitial steel studs showed outstanding effect on the improvement of temperature difference ratio.

Evaluation of ground motion scaling methods on drift demands of energy-based plastic designed steel frames under near-fault pulse-type earthquakes

  • Ganjavi, Behnoud;Hadinejad, Amirali;Jafarieh, Amir Hossein
    • Steel and Composite Structures
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    • v.32 no.1
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    • pp.91-110
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    • 2019
  • In the present study, the effects of six different ground motion scaling methods on inelastic response of nonlinear steel moment frames (SMFs) are studied. The frames were designed using energy-based PBPD approach with the design concept using pre-selected target drift and yield mechanism as performance limit state. Two target spectrums are considered: maximum credible earthquake spectrum (MCE) and design response spectrum (DRS). In order to investigate the effects of ground motion scaling methods on the response of the structures, totally 3216 nonlinear models including three frames with 4, 8 and 16 stories are designed using PBPD approach and then they are subjected to ensembles of ground motions including 42 far-fault and 90 near-fault pulse-type records which were scaled using the six different scaling methods in accordance to the two aforementioned target spectrums. The distributions of maximum inter-story drift over the height of the structures are computed and compared. Finally, the efficiency and reliability of each ground motion scaling method to estimate the maximum nonlinear inter-story drift of special steel moment frames designed by energy-based PBPD approach are statistically investigated, and the most suitable scaling methods with the lowest dispersion for two groups of earthquake ground motions are introduced.

Summarized IDA curves by the wavelet transform and bees optimization algorithm

  • Shahryari, Homayoon;Karami, M. Reza;Chiniforush, Alireza A.
    • Earthquakes and Structures
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    • v.16 no.2
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    • pp.165-175
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    • 2019
  • Incremental dynamic analysis (IDA), as an accurate method to evaluate the parameters of structural performance levels, requires many non-linear time history analyses, using a set of ground motion records which are scaled to different intensity levels. Therefore, this method is very computationally demanding. In this study, a new method is presented to estimate the summarized (16%, 50%, and 84% fractiles) IDA curves of a first-mode dominated structure using discrete wavelet transform and bees optimization algorithm. This method reduces the number of required ground motion records for the prediction of the summarized IDA curves. At first, a subset of first list ground motion records is decomposed by means of discrete wavelet transform which have a low dispersion estimating the summarized IDA curves of equivalent SDOF system of the main structure. Then, the bees algorithm optimizes a series of factors for each level of detail coefficients in discrete wavelet transform. The applied factors change the frequency content of original ground motion records which the generated ground motions records can be utilized to reliably estimate the summarized IDA curves of the main structure. At the end, to evaluate the efficiency of the proposed method, the seismic behavior of a typical 3-story special steel moment frame, subjected to a set of twenty ground motion records is compared with this method.

Numerical simulation of Y-type perfobond rib shear connectors using finite element analysis

  • Kim, Kun-Soo;Han, Oneil;Gombosuren, Munkhtulga;Kim, Sang-Hyo
    • Steel and Composite Structures
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    • v.31 no.1
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    • pp.53-67
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    • 2019
  • This study presents finite element analysis (FEA) on a Y-type perfobond rib shear connection using Abaqus software. The performance of a shear connection is evaluated by conducting a push-out test. However, in practice, it is inefficient to verify the performance by conducting a push-out test with regard to all design variables pertaining to a shear connector. To overcome this problem, FEA is conducted on various shear connectors to accurately estimate the shear strength of the Y-type perfobond rib shear connection. Previous push-out test results for 14 typical push-out test specimens and those obtained through FEA are compared to analyze the shear behavior including consideration of the design variables. The results show that the developed finite element model successfully reflects the effects of changes in the design variables. In addition, using the developed FEA model, the shear resistance of a stubby Y-type perfobond rib shear connector is evaluated based on the concrete strength and transverse rebar size variables. Then, the existing shear resistance formula is upgraded based on the FEA results.

An Experimental Study on the Improvement of Structural Performance for Concrete Structure Spraying Composite Polyurea (복합폴리우레아를 도포한 콘크리트 구조물의 구조성능 개선에 관한 실험적 연구)

  • Cho, Dong-Ho;Kim, Jin-Bong;Kim, Tae-Wan;Eun, Hee-Chang
    • Journal of the Architectural Institute of Korea Structure & Construction
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    • v.35 no.1
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    • pp.21-28
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    • 2019
  • This study investigates the applicability of composite polyurea to contain fiber reinforcement like fiber glass, steel fiber and carbon nanotube. Polyurea as elastomer is an excellent water-proofing material with many mechanical characteristics such as high tensile strength, ductility, high rate of expansion and contraction, and so on. The reinforcing fibers can be utilized for improving the load-carrying capacity of concrete structures. The polyurea plays a role to improve the ductility and toughness. Composite polyurea takes the mechanical advantages of the fibers and the polyurea. The test variables include the type of reinforcing fiber, its spraying thickness, and its weight ratio contained in the composite polyurea. It is observed that the load-carrying capacity, and the ductility and toughness are improved with the increase in the spraying thickness and the weight ratio contained in the composite polyurea. It is expected that the composite polyurea can be widely utilized in enhancing the structural and seismic performance.

A Study on the Effect of Steel Fiber in Reinforced Concrete Coupling Beam Subjected to Cyclic Loading (반복하중을 받는 철근콘크리트 연결보에서 강섬유의 보강효과에 관한 연구)

  • Kim, Jin-Sung;Bae, Baek-Il;Choi, Chang-Sik
    • Journal of the Architectural Institute of Korea Structure & Construction
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    • v.35 no.10
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    • pp.181-190
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    • 2019
  • In this study, four reinforced concrete coupling beams were subjected to cyclic lateral loading test to evaluate the structural performance of coupling beam according to volume fraction of steel fiber. For this purpose, the volume fraction of steel fiber(0%, 1%, 2%) and transverse reinforcement spacing were determined as the main parameter. According to the test results, the maximum strength of D-40C-s100-0 was 1.15, 1.13, 1.05 times higher than D-40C-s300-0, D-40C-s300-1, D-40C-s300-2, respectively. The maximum strength of coupling beams with mitigated rebar details increases as the volume fraction of steel fiber increases. Although steel fiber 2% reinforced specimen(D-40C-s300-2) did not satisfy the amount of transverse reinforcement required for seismic design of coupling beam, the overall performance including to maximum strength, ductility and energy dissipation capacity was similar to the control specimen(D-40C-s100-0). As a result, the use of steel fiber with 2% reinforcement can partially replace the transverse reinforcement in diagonally reinforced concrete coupling beam.

Ultimate shear strength prediction model for unreinforced masonry retrofitted externally with textile reinforced mortar

  • Thomoglou, Athanasia K.;Rousakis, Theodoros C.;Achillopoulou, Dimitra V.;Karabinis, Athanasios I.
    • Earthquakes and Structures
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    • v.19 no.6
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    • pp.411-425
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    • 2020
  • Unreinforced masonry (URM) walls present low shear strength and are prone to brittle failure when subjected to inplane seismic overloads. This paper discusses the shear strengthening of URM walls with Textile Reinforced Mortar (TRM) jackets. The available literature is thoroughly reviewed and an extended database is developed including available brick, concrete and stone URM walls retrofitted and subjected to shear tests to assess their strength. Further, the experimental results of the database are compared against the available shear strength design models from ACI 549.4R-13, CNR DT 215 2018, CNR DT 200 R1/2013, Eurocode 6 and Eurocode 8 guidelines as well as Triantafillou and Antonopoulos 2000, Triantafillou 1998, Triantafillou 2016. The performance of the available models is investigated and the prediction average absolute error (AAE) is as high as 40%. A new model is proposed that takes into account the additional contribution of the reinforcing mortar layer of the TRM jacket that is usually neglected. Further, the approach identifies the plethora of different block materials, joint mortars and TRM mortars and grids and introduces rational calibration of their variable contributions on the shear strength. The proposed model provides more accurate shear strength predictions than the existing models for all different types of the URM substrates, with a low AAE equal to 22.95%.

Nonlinear Behavior of Composite Modular System's Joints (합성 모듈러 시스템 접합부의 비선형 거동 평가)

  • Choi, Young hoo;Lee, Jong il;Lee, Ho chan;Kim, Jin koo
    • Journal of the Earthquake Engineering Society of Korea
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    • v.25 no.4
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    • pp.153-160
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    • 2021
  • The connection of the steel structure serves to transmit external forces to the main components. The same is true for the behavior of modular systems composed mainly of steel or composite members. In this study, the joint performance of the composite and steel modules proposed was evaluated. The analytical models of the two joint types were constructed and were subjected to cyclic loading to assess the safety and the energy dissipation capacity of the joint types. The analysis results of the joints showed that the joints of the modular systems remain stable when the joint rotation reached the seismic performance limit state of the 0.02 rad required for steel intermediate moment frame. It was also observed that the joint of the composite modular system showed higher energy dissipation capacity compared with the steel modular system.

Probability-based prediction of residual displacement for SDOF using nonlinear static analysis

  • Feng, Zhibin;Gong, Jinxin
    • Earthquakes and Structures
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    • v.22 no.6
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    • pp.571-584
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    • 2022
  • The residual displacement ratio (RDRs) response spectra have been generally used as an important means to evaluate the post-earthquake repairability, and the ratios of residual to maximum inelastic displacement are considered to be more appropriate for development of the spectra. This methodology, however, assumes that the expected residual displacement can be computed as the product of the RDRs and maximum inelastic displacement, without considering the correlation between these two variables, which inevitably introduces potential systematic error. For providing an adequately accurate estimate of residual displacement, while accounting for the collapse resistance performance prior to the repairability evaluation, a probability-based procedure to estimate the residual displacement demands using the nonlinear static analysis (NSA) is developed for single-degree-of-freedom (SDOF) systems. To this end, the energy-based equivalent damping ratio used for NSA is revised to obtain the maximum displacement coincident with the nonlinear time history analysis (NTHA) results in the mean sense. Then, the possible systematic error resulted from RDRs spectra methodology is examined based on the NTHA results of SDOF systems. Finally, the statistical relation between the residual displacement and the NSA-based maximum displacement is established. The results indicate that the energy-based equivalent damping ratio will underestimate the damping for short period ranges, and overestimate the damping for longer period ranges. The RDRs spectra methodology generally leads to the results being non-conservative, depending on post-yield stiffness. The proposed approach emphasizes that the repairability evaluation should be based on the premise of no collapse, which matches with the current performance-based seismic assessment procedure.