• Title/Summary/Keyword: masonry infill

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Influence of masonry infill on reinforced concrete frame structures' seismic response

  • Muratovic, Amila;Ademovic, Naida
    • Coupled systems mechanics
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    • v.4 no.2
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    • pp.173-189
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    • 2015
  • In reality, masonry infill modifies the seismic response of reinforced concrete (r.c.) frame structures by increasing the overall rigidity of structure which results in: increasing of total seismic load value, decreasing of deformations and period of vibration, therefore masonry infill frame structures have larger capacity of absorbing and dissipating seismic energy. The aim of the paper is to explore and assess actual influence of masonry infill on seismic response of r.c. frame structures, to determine whether it's justified to disregard masonry infill influence and to determine appropriate way to consider infill influence by design. This was done by modeling different structures, bare frame structures as well as masonry infill frame structures, while varying masonry infill to r.c. frame stiffness ratio and seismic intensity. Further resistance envelope for those models were created and compared. Different structures analysis have shown that the seismic action on infilled r.c. frame structure is almost always twice as much as seismic action on the same structure with bare r.c. frames, regardless of the seismic intensity. Comparing different models resistance envelopes has shown that, in case of lower stiffness r.c. frame structure, masonry infill (both lower and higher stiffness) increased its lateral load capacity, in average, two times, but in case of higher stiffness r.c. frame structures, influence of masonry infill on lateral load capacity is insignificant. After all, it is to conclude that the optimal structure type depends on its exposure to seismic action and its masonry infill to r.c. frame stiffness ratio.

Analytical Study of the Effect of Full and Partial Masonry Infills on the Seismic Performance of School Buildings (조적채움벽 및 허리벽이 학교 건물 내진 성능에 미치는 영향에 대한 해석적 연구)

  • Kim, Tae Wan;Min, Chan Gi
    • Journal of the Earthquake Engineering Society of Korea
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    • v.17 no.5
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    • pp.197-207
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    • 2013
  • The seismic performance of school buildings has been a matter of common interest socially and academically. The structural system of the school buildings is representative of the domestic low-rise reinforced concrete moment resisting frames, which apply extensively infills in their masonry walls. The masonry infilled walls are divided into full masonry infill in the transverse direction and partial masonry infill in the longitudinal direction. The masonry infilled walls are usually not included in structural analysis during the design process, but affect significantly the seismic performance because they behave with surrounding frames simultaneously during earthquakes. Many researchers have studied the effect of the masonry infilled walls, but several issues have been missed such as the increase of asymmetry by adding the full masonry infill, the size of the mean strength of the full masonry infill, and short column effect by the partial masonry infill. The issues were analytically investigated and the results showed that they should be checked at least by nonlinear pushover analysis in the seismic performance evaluation process. The results also confirm the weakness of the guideline of Korean Educational Development Institute where the seismic performance is basically assessed without structural analysis.

Seismic behavior of soft storey mid-rise steel frames with randomly distributed masonry infill

  • Quayyum, Shahriar;Alam, M. Shahria;Rteil, Ahmad
    • Steel and Composite Structures
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    • v.14 no.6
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    • pp.523-545
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    • 2013
  • In this study, the effect of presence and distribution of masonry infill walls on the mid-rise steel frame structures having soft ground storey was evaluated by implementing finite element (FE) methods. Masonry infill walls were distributed randomly in the upper storey keeping the ground storey open without any infill walls, thus generating the worst case scenario for seismic events. It was observed from the analysis that there was an increase in the seismic design forces, moments and base shear in presence of randomly distributed masonry infill walls which underlines that these design values need to be amplified when designing a mid-rise soft ground storey steel frame with randomly distributed masonry infill. In addition, it was found that the overstrength related force modification factor increased and the ductility related force modification factor decreased with the increase in the amount of masonry infilled bays and panels. These must be accounted for in the design of mid-rise steel frames. Based on the FE analysis results on two mid-rise steel frames, design equations were proposed for determining the over strength and the ductility related force modification factors. However, it was recommended that these equations to be generalized for other steel frame structure systems based on an extensive analysis.

Experimental study of masonry infill reinforced concrete frames with and without corner openings

  • Khoshnoud, Hamid Reza;Marsono, Kadir
    • Structural Engineering and Mechanics
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    • v.57 no.4
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    • pp.641-656
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    • 2016
  • Reinforced concrete frame buildings with masonry infill walls are one of the most popular structural systems in the world. In most cases, the effects of masonry infill walls are not considered in structural models. The results of earthquakes show that infill walls have a significant effect on the seismic response of buildings. In some cases, the buildings collapsed as a result of the formation of a soft story. This study developed a simple method, called corner opening, by replacing the corner of infill walls with a very flexible material to enhance the structural behavior of walls. To evaluate the proposed method a series of experiments were conducted on masonry infill wall and reinforced concrete frames with and without corner openings. Two 1:4 scale masonry infill walls with and without corner openings were tested under diagonal tension or shear strength and two RC frames with full infill walls and with corner opening infill walls were tested under monotonic horizontal loading up to a drift level of 2.5%. The experimental results revealed that the proposed method reduced the strength of infill wall specimens but considerably enhanced the ductility of infill wall specimens in the diagonal tension test. Moreover, the corner opening in infill walls prevented the slid shear failure of the infill wall in RC frames with infill walls.

Seismic Performance Evaluation of Reinforced Concrete Frame with Unreinforced Masonry Infill (비보강 조적 끼움벽체를 가지는 철근콘크리트 골조 구조물 내진성능평가)

  • Cho, Won-Sun;Lee, Sang-Hyun;Chung, Lan;Kim, Hye-Jin;Kim, Seung-Jin;Yu, Eun-Jong
    • Journal of the Architectural Institute of Korea Structure & Construction
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    • v.28 no.3
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    • pp.31-41
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    • 2012
  • Unreinforced masonry infill walls have been frequently used as interior partitions and exterior walls in RC moment frame structures in Korea for a long time. In the seismic design and evaluation of RC moment frames, the masonry infill walls have been usually treated as non-structural elements and ignored in analytical model. In this study, the parametric nonlinear static (pushover) analyses and experimental tests are performed on RC frame with/without unreinforced masonry infill walls. The effects of column shear strength, beam-column stiffness ratios and the amount of axial force applied on the column, are investigated in numerical analyses. Numerical analysis and experimental results indicate that the masonry infill increases the stiffness and strength, but reduces ductility.

Pushover Analysis of a 5-Story RC IMRF with Masonry Infill Walls Considering Inelastic Shear Behavior of Beam-Column Joint (보-기둥 접합부 비탄성 전단거동을 고려한 조적벽체를 가진 5층 철근콘크리트 중간모멘트골조의 푸쉬오버해석)

  • Kang, Suk-Bong;Lim, Byeong-Jin
    • Journal of the Architectural Institute of Korea Structure & Construction
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    • v.28 no.8
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    • pp.11-20
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    • 2012
  • In this study, the effects of the inelastic shear behavior of beam-column joint, the vertical distribution of lateral load considering higher modes and masonry infill walls on the response of RC IMRF are evaluated in the pushover analysis, where 5-story structures were designed in accordance with KBC2009. M-${\phi}$ relationship for beam and column was identified with fiber model. An analytical model for inelastic beam-column joint was suggested and the behavior of the joint was reproduced with simple and unified joint shear behavior model. An inelastic masonry infill wall was simulated with two diagonal braces. Negligence of inelastic shear behavior of the joint caused overestimate of the maximum strength of the structures. The structures with masonry infill walls showed greater initial stiffness and maximum strength than those for the structure without the walls and the differences disappeared after the failure of the walls.

Load-displacement Response of Gravity Load Designed Reinforced Concrete Moment Frames with Various Height of Masonry Infill Walls (조적채움벽 높이에 따른 철근콘크리트 중력골조의 하중-변위 응답)

  • Han, Ji Min;Lee, Chang Seok;Han, Sang Whan
    • Journal of the Earthquake Engineering Society of Korea
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    • v.24 no.1
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    • pp.39-47
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    • 2020
  • Lightly reinforced concrete (RC) moment frames may suffer significant damage during large earthquake events. Most buildings with RC moment frames were designed without considering seismic loads. The load-displacement response of gravity load designed frames could be altered by masonry infill walls. The objective of this study is to investigate the load-displacement response of gravity load designed frames with masonry infill walls. For this purpose, three-story gravity load designed frames with masonry infill walls were considered. The masonry infilled RC frames demonstrated larger lateral strength and stiffness than bare RC frames, whereas their drift capacity was less than that of bare frames. A specimen with a partial-height infill wall showed the least drift capacity and energy dissipation capacity. This specimen failed in shear, whereas other specimens experienced a relatively ductile failure mode (flexure-shear failure).

Seismic response of RC frame structures strengthened by reinforced masonry infill panels

  • Massumi, Ali;Mahboubi, Behnam;Ameri, Mohammad Reza
    • Earthquakes and Structures
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    • v.8 no.6
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    • pp.1435-1452
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    • 2015
  • The performance of masonry infilled frames during the past earthquakes shows that the infill panels play a major role as earthquake-resistant elements. Experimental observations regarding the influence of infill panels on increasing stiffness and strength of reinforced concrete structures reveal that such panels can be used in order to strengthen reinforced concrete frames. The present study examines the influence of infill panels on seismic behavior of RC frame structures. For this purpose, several low- and mid-rise RC frames (two-, four-, seven-, and ten story) were numerically investigated. Reinforced masonry infill panels were then placed within the frames and the models were subjected to several nonlinear incremental static and dynamic analyses. In order to determine the acceptance criteria and modeling parameters for frames as well as reinforced masonry panels, the Iranian Guideline for Seismic Rehabilitation of Existing Masonry Buildings (Issue No. 376), the Iranian Guideline for Seismic Rehabilitation of Existing Structures (Issue No. 360) and FEMA Guidelines (FEMA 273 and 356) were used. The results of analyses showed that the use of reinforced masonry infill panels in RC frame structures can have beneficial effects on structural performance. It was confirmed that the use of masonry infill panels results in an increment in strength and stiffness of the framed buildings, followed by a reduction in displacement demand for the structural systems.

Earthquake Resistance of Masonry Infilled Wall (조적 채움벽의 내진성)

  • 이한선;우성우;유은진
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.93-98
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    • 2000
  • The objective of this study is to investigate the results of researches which have been conducted throughout the world and in Korea concerning the behavior modes of masonry infill panels and frames. The influence of masonry infill panels on the seismic behavior of RC frames must be considered in the design and evaluation procedure though current code provisions do not generally require explicitly this consideration. However, since the level of the earthquake intensity in Korea is assumed to be moderate, the masonry infill panels may cause the different effect to the structure from those in high seismicity region and this difference should be studied in depth in the future.

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Seismic response of masonry infilled RC frames: practice-oriented models and open issues

  • Lima, Carmine;De Stefano, Gaetano;Martinelli, Enzo
    • Earthquakes and Structures
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    • v.6 no.4
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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.