• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.199-206
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• 2005

In many other countries framed structures with inadequate lateral strength and stiffness have been strengthened by providing reinforced concrete infilled wall. There is a general agreement among researchers those infilled walls have 3-5times greater lateral strength compared with bare frame. The main objective of this research is to investigate the behavior and strength of reinforced concrete frames infilled with concrete block and cast-in-place reinforced concrete panels used for strengthening the structure against seismic action. For this purpose three 1/3 scale, one-bay, one-story reinforced concrete infilled frames were tested under reversed cyclic loading simulating the seismic effect. The results indicate that infilled walls increase both strength and stiffness significantly under lateral loads. Especially Strength capacity and initial stiffness of CIP infilled wall increased 3.8 times and 6.6 times higher than lightly reinforced concrete frame.

• Journal of the Korea Concrete Institute
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• v.21 no.3
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• pp.327-335
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• 2009

In the seismic region, non-ductile structures often form soft story and exhibit brittle collapse. However, structure demolition and new structure construction strategies have serious problems, as construction waste, environmental pollution and popular complain. And these methods can be uneconomical. Therefore, to satisfy seismic performance, so many seismic retrofit methods have been investigated. There are some retrofit methods as infill walls, steel brace, continuous walls, buttress, wing walls, jacketing of column or beam. Among them, the infilled frames exhibit complex behavior as follows: flexible frames experiment large deflection and rotations at the joints, and infilled shear walls fail mainly in shear at relatively small displacements. Therefore, the combined action of the composite system differs significantly from that of the frame or wall alone. Purpose of research is evaluation on the seismic performance of infill walls, and improvement concept of this paper is use of SHCCs (strain-hardening cementitious composites) to absorb damage energy effectively. The experimental investigation consisted of cyclic loading tests on 1/3-scale models of infill walls. The experimental results, as expected, show that the multiple crack pattern, strength, and energy dissipation capacity are superior for SHCC infill wall due to bridging of fibers and stress redistribution in cement matrix.

• Journal of the Korea Concrete Institute
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• v.24 no.1
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• pp.3-14
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• 2012

This paper describes experimental results on the seismic performance of SHCC (strain-hardening cement composite) infill wall for improving damage tolerance capacity of non-ductile frame. To investigate the effect of tensile strain capacity and cracking behavior of SHCC materials on the shear behavior of SHCC infill wall, three infill walls were fabricated and tested under cyclic loading. The test parameter in this study is a type of cement composites; concrete and SHCCs. The two types of SHCC materials were prepared for infill walls. In order to induce crack damages into the mid-span of the infill wall, each infill wall had two 100-mm-deep-notches on both sides. Test results indicated that SHCC infill walls showed superior crack control capacities and much larger drift ratios at the peak loads than RC (reinforced concrete) infill wall, as expected. In particular, due to the bridging actions of the reinforcing fibers, SHCC matrix used in this study would delay the stiffness degradation of infill wall after the first inclined cracking. Moreover, from the damage classes based on the cracks' maximum width in the infill walls, it was observed that PIW-SHD specimen possessed nearly threefold seismic capacities compared to PIW-SLD specimen. Also, from the results on the strain of diagonal reinforcements, it can be concluded that the SHCC matrix would resist a part of tensile stresses transferred along steel rebar in the infill wall.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.55-56
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• 2010

Infill walls have been investigated experimentally and theoretically by many researchers during last decades. The objective of this research is to evaluate structural strengthening performance of lightly reinforced concrete with reduced the inside cross-section of Strain-hardening cement composites(SHCC) experimentally.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.3 s.55
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• pp.209-216
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• 2009

Flexible frames on their own offer little resistance to lateral forces, resulting often in large deflections and rotations at the joints. On the other hand, walls subjected to lateral loads fail mainly in shear at relatively small displacements. Therefore, when the nonductile frames and wall act together, the combined action of the composite system differs significantly from that of the frame or wall alone. The objective of the study is to evaluate seismic response of infill walls with notched midsection. Reinforcement detail of wall was main variable in the experiment. Also SHCC was used in order to prevent damage concentration into notched midsection of walls. Test results, SHCC infill walls show the multiple crack patterns as expected. However, PIW-ND specimen exhibits less story drift, stiffness and energy dissipation capacity than those of PIW-NC specimen.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.9
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• pp.4216-4222
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• 2011

In this study the inelastic behavior of the existing school buildings with infilled masonry walls is analysed by pushover method. The shear stiffness and strength of masonry wall is calculated from the prior experimets and verified by inelastic analysis. The height of infilled masonry wall affects the structural behavior. The higher the masonry wall height, the higher the initial shear stiffness and strength of masonry wall. As the cracks are developed, the strength of masonry wall is much decreased. The proposed inelastic analysis method shows similar results with the experiments and can be used as inelastic analysis model of reinforced concrete buildings with infilled masonry walls.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.89-92
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• 2008

The seismic behavior of the lightly reinforced concrete frames (LRCFs) was controlled by the nonductile behavior of the critical regions. These critical regions require retrofit to improve the seismic behavior of the lightly reinforced concrete frames. Critical column end regions must be retrofit to increase the global ductility capacity. The objective of this research is to evaluate structural strengthening performance of lightly reinforced concrete frame with Strain hardening cement composite(SHCC) experimentally. The experimental investigation consisted of a cyclic load tests on 1/3-scale models of precast infill walls. Reinforcement detail of infill wall was variables in the experiment. The experimental results, as expected, show that the multiple crack pattern, strength, ductility and energy dissipation capacity are superior for specimen with SHCC infill wall due to bridging of fibers and stress redistribution in cement matrix.

• Journal of the Korean Institute of Educational Facilities
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• v.19 no.4
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• pp.21-28
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• 2012

This study proposes a procedure for evaluating the seismic performance and retrofit of a typical reinforced building (R/C) school buildings contructed in the 1980s. The procedure is derived from the Japanese Standard for Evaluation of Seismic Capacity of Existing Reinforced Concrete Buildings and Nonlinear Static Procedure (NSP) specified in Federal Emergency Management Agency (FEMA 356). In this study, the Japanese Standard was applied for evaluating the additionally required seismic performance in the existing school building. Cast-in-place (CIP) reinforced concrete infill walls and steel braces were used to seismically retrofit the existing school building located in the region of Hongsung in Chungnam. In the pushover analysis, i.e NSP, the hinge properties of columns, beams, infill walls and steel braces were carefully calibrated based on the existing experiment results in the available literatures. The predicted seismic performance for the retrofitted building was compared to that for the virgin building. Based on the seismic evaluation with the Japanese Standard and the FEMA 356 criteria, the addition of CIP reinforced concrete infill walls and steel braces have superior constructablility and can improve effectively the seismic performance of the existing school buildings constructed in 1980s.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.243-253
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• 2011

This paper describes an analytical study on seismic performance of domestic reinforced concrete (RC) school building not designed by seismic provision. The seismic index and the seismic performance of the building were evaluated through Japanese standard and Midas Gen, respectively. Seismic index (Is) of the RC school buildings in the X-direction is below 0.4. Based on the seismic index, for seismic-strengthening the building, infill shear wall or steel brace with a capacity of 1,300 kN was used. According to nonlinear static analysis results, the contribution of the seismic-strengthening to the shear resistance of the school building was measured to be greater than 30%. However, as expected, shear strength of school building strengthened with infill wall dropt rapidly after peak load and much narrower ductile behavior range was observed compared to steel brace strengthened building. Also, the building strengthened with steel brace showed 30% larger spectral displacement than that strengthened with infill shear wall. In nonlinear dynamic analysis, for the time history analysis, the maximum displacement showed tendency to decrease as amount of reinforcement increased, regardless of strengthening method. It was recommended that variable soil properties and earthquake record should be considered for improving seismic performance of buildings in seismic zone.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.247-250
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• 2005

The aim of Cast-In-Place(CIP) method is to upgrade the strength, ductility and stiffness of the structure to the required level. The main objective of this research is to investigate the shear and the flexural strength of reinforced concrete frames infilled with CIP reinforced concrete wall. For this three 1/3 scale, one-bay, one story reinforced concrete infill wall were tested under reversed cyclic loading simulating the seismic effect. Results of tests of CIP shear wall were reviewed to evaluate the current design provisions and to establish the feasible retrofitting method.