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

Hamid Reza Khoshnoud,Kadir Marsono 국제구조공학회 2016 Structural Engineering and Mechanics, An Int'l Jou Vol.57 No.4

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.

끼움벽 보강 골조의 내진성능

김선우(Kim Sun-Woo),이영오(Lee Young-Oh),윤현도(Yun Hyun-Do) 대한건축학회 2007 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.27 No.1

Many reinforced concrete moment resisting frame buildings in seismic zones lack strength and ductility. A infill wall system may provide an economic advantage for the retrofit of these structures. The objective of this research is to evaluate structural strengthening performance of lightly reinforced concrete frame retrofitted with infill wall experimentally. In order to evaluate the performance of this type of system, four one story-one bay non-ductile frame were constructed and rehabilitated with a recycled concrete block masonry wall and two CIP(cast-in-place) walls. Especially, HPFRCC (High performance fiber-reinforced cement composite) was used in infill wall to improve ductility of infill wall-frame system. From the test results, infill wall-frame specimen exhibited a marked increase in shear strength compared to non-ductile RC frame specimen. But the ductility and story-drift at maximum load were decreased when shear strength of infill wall larger than that of existing RC frame except for IWF-H specimen retrofitted with HPFRCC infill wall. Therefore, it is difficult for RC infill wall-frame to satisfy requirement condition of maximum story-drift and ductility capacity in view of failure mode of all infill-wall frame specimens. Based on the seismic performance of test infill-wall specimen, it is confirmed that adequate reinforcement is added to assure sufficient seismic performance.

Reducing the In-plane Effect of Infill on Steel Moment Frame

A. Keyvani Borujeni,T. Mahdi 한국강구조학회 2017 International Journal of Steel Structures Vol.17 No.3

In this paper, four large-scale one-story steel moment-resisting frame specimens have been tested. The first specimen is a onestory steel moment-resisting frame without masonry infill walls. The second is similar to the first but with infill wall having full physical contact to the frame. The other two are non-structural infill walls. The first non-structural infill wall has a complete decoupling from the frame, while the second has a full contact at the top of the wall and separated from the columns. The results of this paper have shown that life safety performance level for non-structural infill wall having a complete decoupling from the frame has satisfied the allowable story drift. This was not the case for infill wall having full physical contact to the frame or nonstructural infill walls sepatared from two sides.

Influence of openings of infill wall on seismic vulnerability of existing RC structures

Hakan Dilmaç 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.75 No.2

The contribution of infill wall is generally not considered in the structural analysis of reinforced concrete (RC) structures due to the lack of knowledge of the complex behavior of the infilled frame of RC structures. However, one of the significant factors affecting structural behavior and earthquake performance of RC structures is the infill wall. Considering structural and architectural features of RC structures, any infill wall may have openings with different amounts and aspect ratios. In the present study, the influence of infill walls with different opening rates on the structural behaviors and earthquake performance of existing RC structures were evaluated. Therefore, the change in the opening ratio in the infill wall has been investigated for monitoring the change in structural behavior and performance of the RC structures. The earthquake performance levels of existing RC structures with different structural properties were determined by detecting the damage levels of load-carrying components. The results of the analyzes indicate that the infill wall can completely change the distribution of column and beam damage level. It was observed that the openings in the walls had serious impact on the parameters affecting the behavior and earthquake performance of the RC structures. The infill walls have a beneficial effect on the earthquake performance of RC structures, provided they are placed regularly and there are appropriate openings rate throughout the RC structures and they do not cause structural irregularities.

조적채움벽을 갖는 RC 벽‐슬래브 골조의 내진성능 연구

김찬호,이승제,허석재,엄태성 한국지진공학회 2022 한국지진공학회논문집 Vol.26 No.3

This study investigated the seismic performance of reinforced concrete (RC) wall-slab frames with masonry infills. Four RC wall-slab frames with or without masonry infill were tested under cyclic loading. The RC frames were composed of in-plane and out-of-plane walls and top and bottom slabs. For masonry infill walls, cement bricks were stacked applying mortar paste only at the bed joints, and, at the top, a gap of 50 mm was intentionally left between the masonry wall and top RC slab. Both sides of the masonry walls were finished by applying ordinary or fiber-reinforced mortars. The tests showed that despite the gap on top of the masonry walls, the strength and stiffness of the infilled frames were significantly increased and were different depending on the direction of loading and the finishing mortars. During repeated loading, the masonry walls underwent horizontal and diagonal cracking and corner crushing/spalling, showing a rocking mode inside the RC wall-slab frame. Interestingly, this rocking mode delayed loss of strength, and as a result, the ductility of the infilled frames increased to the same level as the bare frame. The interaction of masonry infill and adjacent RC walls, depending on the direction of loading, was further investigated based on test observations.

Improvement of Fire Resistance for Timber Framed Walls by Reinforcement of Heavy Timber Frame

박주생,황권환,김광모 한국가구학회 2010 한국가구학회지 Vol.21 No.6

Fire resistance of new hybrid timber framed wall systems was evaluated in this study. These wall systems are composed of two major structural parts. One part is a heavy timber frame part designed to take charge of whole vertical load using heavy timber post and beam, and the other is an infill wall structure, designed to take charge of whole horizontal load and to provide an established level of fire resistance. A basic concept of this hybrid wall is adopted from a typical furniture structure with frame. A timber post and beam frame is constructed with Japanese Larch solid timber post(180mm by 180mm) and beam(180mm by 240mm). As infill wall systems, two types of walls are applied. One is a typical light timber framed wall with solid blocking and another is a structural insulated panel wall, in which polystyrene insulation is filled between two structural panels to make single structure. For all tested walls, two layers of 12.5mm thick type-X gypsum boards are used on fire exposed side. Prior to tests for hybrid walls, only infill walls are tested without heavy timber frame. All fire resistance tests are carried out in accordance with KS F 2257, and temperatures on several points within wall structure and unexposed wall surface are measured during fire tests. It is considered that the reinforcement of heavy timber frame is significantly efficient for improving the fire resistance of timber framed walls.

Improvement of Fire Resistance for Timber Framed Walls by Reinforcement of Heavy Timber Frame

Park, Joo-Saeng,Hwang, Kweon-Hwan,Kim, Kwang-Mo Korea Furniture Society 2010 한국가구학회지 Vol.21 No.6

본 연구에서는 두 개의 주요 구조부분으로 구성된 새로운 하이브리드 목조 벽체의 내화성능을 평가하였다. 수직하중을 전적으로 담당하는 기둥-보 형태의 기본 골조에 두 가지 형태의 벽체가 채워졌을 때 이 전체를 내력 벽체로 가정하고 그 내화성능을 평가하고자 하였다. 하이브리드 벽체의 기본 개념은 뼈대를 갖는 전형적인 가구의 구조로부터 채용되었다. 기본이 되는 기둥-보 골조는 국산 낙엽송 소재로서, 기둥은 $180mm{\times}180mm$, 보는 $180mm{\times}240mm$ 단면의 부재가 사용되었다. 기둥-보 골조의 내부에 채워지는 벽체는 두 종류로서, 하나는 블러킹이 사용된 일반적인 경골목구조 벽체이고, 또 하나는 구조용 패널 사이에 스티로폼 단열재가 채워져 일체화된 구조를 이루는 구조용 단열 패널 벽체이다. 내화성능 시험에 사용된 모든 벽체는 2겹의 방화석고보드를 화염 노출면에 부착하였다. 모든 벽체는 우선 기둥-보 골조가 없는 상태에서 표준화염 조건에서 내화성능 시험을 수행하였고 다시 기둥-보 골조와 결합된 형태로 내화성능 시험을 수행하였다. 시험에 적용된 화염조건은 KS F 2257의 조건을 적용하였고 시험 중 구조체 내부 각 부위의 온도변화도 측정하였다. 본 연구를 통해 기둥-보 골조의 보강이 목구조 벽체의 내화성능 향상에 상당히 기여하는 것으로 확인되었다. Fire resistance of new hybrid timber framed wall systems was evaluated in this study. These wall systems are composed of two major structural parts. One part is a heavy timber frame part designed to take charge of whole vertical load using heavy timber post and beam, and the other is an infill wall structure, designed to take charge of whole horizontal load and to provide an established level of fire resistance. A basic concept of this hybrid wall is adopted from a typical furniture structure with frame. A timber post and beam frame is constructed with Japanese Larch solid timber post(180mm by 180mm) and beam(180mm by 240mm). As infill wall systems, two types of walls are applied. One is a typical light timber framed wall with solid blocking and another is a structural insulated panel wall, in which polystyrene insulation is filled between two structural panels to make single structure. For all tested walls, two layers of 12.5mm thick type-X gypsum boards are used on fire exposed side. Prior to tests for hybrid walls, only infill walls are tested without heavy timber frame. All fire resistance tests are carried out in accordance with KS F 2257, and temperatures on several points within wall structure and unexposed wall surface are measured during fire tests. It is considered that the reinforcement of heavy timber frame is significantly efficient for improving the fire resistance of timber framed walls.

The investigation of seismic performance of existing RC buildings with and without infill walls

Hakan Dilmac,Hakan Ulutas,Hamide Tekeli,Fuat Demir 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.22 No.5

One of the important factors is the infill walls in the change of the structural rigidity, ductility, dynamic and static characteristics of the structures. The infill walls are not generally included in numerical analysis of reinforced concrete (RC) structural system due to lack of suitable theory and the difficulty of calculating the recommended models. In seismic regions worldwide, the residential structures are generally RC buildings with infill wall. Therefore, understanding the contribution of the infill walls to seismic performance of buildings may have a vital importance. This paper investigates the effects of infill walls on seismic performance of the existing RC residential buildings by considering requirements of the Turkish Earthquake Code (TEC). Seismic performance levels of residential RC buildings with and without walls in high-hazard zones were determined according to the nonlinear procedure given in the code. Pushover curves were obtained by considering the effect of masonry infill walls on seismic performance of RC buildings. The analysis results showed that the infill walls beneficially effected to the rigidity, roof displacements and seismic performance of the building.

Seismic performance of RC frame structures strengthened by HPFRCC walls

Hyun Do Yun,황진하,Mee Yeon Kim,최승호,박완신,Kang Su Kim 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.75 No.3

An infill wall made of high-performance fiber-reinforced cementitious composites (HPFRCC) was utilized in this study to strengthen the reinforced concrete (RC) frame structures that had not been designed for seismic loads. The seismic performance of the RC frame structures strengthened by the HPFRCC infill walls was investigated through the experimental tests, and the test results showed that they have improved strength and deformation capabilities compared to that strengthened by the RC infill wall. A simple numerical modeling method, called the modified longitudinal and diagonal line element model (LDLEM), was introduced to consider the seismic strengthening effect of the infill walls, in which a section aggregator approach was also utilized to reflect the effect of shear in the column members of the RC frames. The proposed model showed accurate estimations on the strength, stiffness, and failure modes of the test specimens strengthened by the infill walls with and without fibers.

조적채움벽 높이에 따른 철근콘크리트 중력골조의 하중-변위 응답

한지민,이창석,한상환 한국지진공학회 2020 한국지진공학회논문집 Vol.24 No.1

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).