• Structural Engineering and Mechanics
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• 제70권4호
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• pp.421-429
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• 2019

This paper presents an analytical model for the estimation of initial lateral stiffness of steel moment resisting frames with masonry infills. However, rather than focusing on the single bay-single storey substructure, the developed model attempts to estimate the global stiffness of multi-storey and multi-bay frames, using an assembly of equivalent springs and taking into account the shape of the lateral loading pattern. The contribution from each infilled frame panel is included as an individual spring, whose properties are determined on the basis of established diagonal strut macro-modeling approaches from the literature. The proposed model is evaluated parametrically against numerical results from frame analyses, with varying number of frame stories, infill openings, masonry thickness and modulus of elasticity. The performance of the model is evaluated and found quite satisfactory.

• Computers and Concrete
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• 제10권1호
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• pp.1-18
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• 2012

This paper presents the details of studies conducted on hollow concrete block masonry (HCBM) units and wall panels. This study includes, compressive strength of unit block, ungrouted and grouted HCB prisms, flexural strength evaluation, testing of HCBM panels with and without opening. Non-linear finite element (FE) analysis of HCBM panels with and without opening has been carried out by simulating the actual test conditions. Constant vertical load is applied on the top of the wall panel and then lateral load is applied in incremental manner. The in-plane deformation is recorded under each incremental lateral load. Displacement ductility factors and response reduction factors have been evaluated based on experimental results. From the study, it is observed that fully grouted and partially reinforced HCBM panel without opening performed well compared to other types of wall panels in lateral load resistance and displacement ductility. In all the wall panels, shear cracks originated at loading point and moved towards the compression toe of the wall. The force reduction factor of a wall panel with opening is much less when compared with fully reinforced wall panel with no opening. The displacement values obtained by non-linear FE analysis are found to be in good agreement with the corresponding experimental values. The influence of mortar joint has been included in the stress-strain behaviour as a monolith with HCBM and not considered separately. The derived response reduction factors will be useful for the design of reinforced HCBM wall panels subjected to lateral forces generated due to earthquakes.

• Earthquakes and Structures
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• 제8권1호
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• pp.225-251
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• 2015

This paper presents a state-of-the-art review of the nonlinear modelling techniques available today for describing the structural behaviour of masonry infills and their interaction with frame structures subjected to in-plane loads. Following brief overviews on the behaviour of masonry-infilled frames and on the results of salient experimental tests, three modelling approaches are discussed in more detail: the micro, the meso and the macro approaches. The first model considers each of the infilled frame elements as separate: brick units, mortar, concrete and steel reinforcement; while the second approach treats the masonry infill as a continuum. The paper focuses on the third approach, which combines frame elements for the beams and columns with one or more equivalent struts for the infill panel. Due to its relative simplicity and computational speed, the macro model technique is more widely used today, though not all proposed models capture the main effects of the frame-infill interaction.

• Earthquakes and Structures
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• 제6권4호
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• pp.409-436
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• 2014

Although it is widely accepted that the interaction -between masonry infill and structural members significantly affects the seismic response of reinforced concrete (RC) frames, this interaction is generally neglected in current design-oriented seismic analyses of structures. Moreover, the role of masonry infill is expected to be even more relevant in the case of existing frames designed only for gravitational loads, as infill walls can significantly modify both lateral strength and stiffness. However, the additional contribution to both strength and stiffness is often coupled to a modification of the global collapse mechanisms possibly resulting in brittle failure modes, generally related to irregular distributions of masonry walls throughout the frame. As a matter of principle, accurate modelling of masonry infill should be at least carried out by adopting nonlinear 2D elements. However, several practice-oriented proposals are currently available for modelling masonry infill through equivalent (nonlinear) strut elements. The present paper firstly outlines some of the well-established models currently available in the scientific literature for modelling infill panels in seismic analyses of RC frames. Then, a parametric analysis is carried out in order to demonstrate the consequences of considering such models in nonlinear static and dynamic analyses of existing RC structures. Two bay-frames with two-, three- and four-storeys are considered for performing nonlinear analyses aimed at investigating some critical aspects of modelling masonry infill and their effects on the structural response. Particularly, sensitivity analyses about specific parameters involved in the definition of the equivalent strut models, such as the constitutive force-displacement law of the panel, are proposed.

• 한국구조물진단유지관리공학회 논문집
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• 제24권4호
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• pp.81-90
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• 2020

기존 비보강 조적벽체의 내진 성능과 에너지 효율을 동시에 보강하기 위한 TCP 보강 공법을 개발하였다. TCP는 경량 모르타르 내 격자형 탄소섬유 시트와 모세관 튜브를 매립하여 일체로 타설한 패널로 조적벽체에 부착하여 탄소섬유 시트에 의한 내진보강과 모세관 튜브에 온수를 공급함으로써난방 또는 단열 등의 에너지 보강을 동시에 달성할수 있는 보강 공법이다. 본 연구에서는 TCP의 내진 보강 효과를 파악하기 위하여 TCP 보강 유무에 따른 조적 벽체를 대상으로 정적가력실험을 실시하였다. 실험 결과, TCP 보강에 의해 최대 강도 및 변위가 약 1.4배증가하였으며, 초기 강성과 에너지 흡수능력에 효과가 있음을 보였다. 또한, 손상에 따른 조적 벽체의 변형이 제어됨에 따라 취성 파괴를 예방할수 있을 것으로 판단된다.

• Steel and Composite Structures
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• 제19권2호
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• pp.309-325
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• 2015

A convenient procedure for seismic retrofit of existing buildings is to use passive control methods, like using friction dampers in steel frames with bracing systems. In this method, reduction of seismic demand and increase of ductility generally improve seismic performance of the structures. Some of its advantages are development of a stable rectangular hysteresis loop and independence on environmental conditions such as temperature and loading rate. In addition to friction dampers, masonry-infill panels improve the seismic resistance of steel structures by increasing lateral strength and stiffness and reducing story drifts. In this study, the effect of masonry-infill panels on seismic performance of a three-span four-story steel frame with Pall friction dampers is investigated. The results show that friction dampers in the steel frame increase the ductility and decrease the drift (to less than 1%). The infill panels fulfill their function during the imposed drift and increase structural strength. It can be concluded that infill panels together with friction dampers, reduced structural dynamic response. These infill panels dissipated input earthquake energy from 4% to 10%, depending on their thickness.

• 한국지진공학회논문집
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• 제25권6호
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• pp.293-303
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• 2021

Seismic fragility functions for unreinforced masonry buildings were derived based on the incremental dynamic analysis of eight representative inelastic numerical models for application to Korea's earthquake damage estimation system. The effects of panel zones formed between piers and spandrels around openings were taken into account explicitly or implicitly regarding stiffness and inelastic deformation capacity. The site response of ground motion records measured at the rock site was used as input ground motion. Limit states were proposed based on the fraction of structural components that do not meet the required performance from the nonlinear static analysis of each model. In addition to the randomness of ground motion considered in the incremental dynamic analysis explicitly, supplementary standard deviation due to uncertainty that was not reflected in the fragility assessment procedure was added. The proposed seismic fragility functions were verified by applying them to the damage estimation of masonry buildings located around the epicenter of the 2017 Pohang earthquake and comparing the result with actual damage statistics.

• Computers and Concrete
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• 제13권6호
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• pp.749-764
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• 2014

Structural safety has always been a key preoccupation for engineers responsible for the design of civil engineering projects. One of the mechanisms of structural failure, which has gathered increasing attention over the past few decades, is referred to as 'progressive collapse' which happens when one or several structural members suddenly fail, whatever the cause (accident, attack, seismic loading(.Any weakness in design or construction of structural elements can induce the progressive collapse in structures, during seismic loading. Masonry infill panels have significant influence on structure response against the lateral load. Therefore in this paper, seismic performance and shear strength of R.C frames with brick infill panel under various lateral loading patterns are investigated. This evaluation is performed by nonlinear static analysis. The results provided important information for additional design guidance on seismic safety of RC frames with brick infill panel under progressive collapse.

• Earthquakes and Structures
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• 제16권3호
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• pp.265-277
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• 2019

Framed masonry wall structures represent a typical high-rise structural system that are also seismically vulnerable. During ground motions, they are excited in both in-plane and out-of-plane terms. The interaction between the frame and the infill during ground motion is a highly investigated phenomenon in the field of seismic engineering. This paper presents a numerical investigation of two distinct static out-of-plane loading methods for framed masonry wall models. The first and most common method is uniformly loaded infill. The load is generally induced by the airbag. The other method is similar to in-plane push-over method, involves loading of the frame directly, not the infill. Consequently, different openings with the same areas and various placements were examined. The numerical model is based on calibrated in-plane bare frame models and on calibrated wall models subjected to OoP bending. Both methods produced widely divergent results in terms of load bearing capabilities, failure modes, damage states etc. Summarily, uniform load on the panel causes more damage to the infill than to the frame; openings do influence structures behavior; three hinged arching action is developed; and greater resistance and deformations are obtained in comparison to the frame loading method. Loading the frame causes the infill to bear significantly greater damage than the infill; infill and openings only influence the behavior after reaching the peak load; infill does not influence initial stiffness; models with opening fail at same inter-storey drift ratio as the bare frame model.

• 한국산학기술학회논문지
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• 제14권12호
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• pp.6504-6513
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• 2013

본 연구에서 농촌주택을 대상으로 농촌주택의 구법과 재료의 지역별 시기별 변화 특징 분석결과, 지붕형태는 팔작지붕/우진각지붕(1970)-평지붕(1980)-맞배지붕(1990), 지붕구조재료는 한식목조/간이한식목조-파라펫눈썹지붕/경사슬래브-양식목조-경량철골조, 지붕마감재료는 초가/한식기와-슬레이트-시멘트/강판-아스팔트슁글/샌드위치패널/몰탈방수, 벽체구조재는 한식목조/간이한식목조-시멘트조적조-RC조-경량철골조/양식목조, 벽체마감재료는 흘미장/회벽-치장벽돌쌓기/시멘트미장위 페인트마감-자연석치장/사이딩/타일, 담장재료는 전시기별로 돌담과 시멘트블록, 마당재료는 흙바닥, 콘크리트가 사용된 것으로 나타났다. 지역별 변화특징으로 주택구조, 지붕형태, 지붕구조재료, 벽체마감재료, 외부공간에서 담장재료와 마당재료는 북부지역, 중부지역, 남부지역별로 농촌주택 특징변화의 차이가 나타났으며, 지붕구조재료, 벽체구조재료는 지역별로 유사한 변화양상이 나타나는 것으로 분석되었다.