• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.52-62
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• 2015

This study aims at developing a new seismic resistant method by using precast concrete wall panels for existing low-rise, reinforced concrete beam-column buildings such as school buildings. Three quasi-static hysteresis loading tests were performed on one unreinforced beam-column specimen and two reinforced specimens with U-type precast wall panels. Top shear connection of the PC panel was required to show the composite strength of RC column and PC wall panel. However, the strength of the connection did not influence directly on the ultimate loading capacities of the specimens in the positive loading because the loaded RC column push the side of PC wall panel and it moved horizontally before the shear connector receive the concentrated shear force in the positive loading process. Under the positive loading sequence(push loading), the reinforced concrete column and PC panel showed flexural strength which is larger than 97% of the composite section because of the rigid binding at the top of precast panel. Similar load-deformation relationship and ultimated horizontal load capacities were shown in the test of PR1-LA and PR1-LP specimens because they have same section dimension and detail at the flexural critical section. An average of 4.7 times increase in the positive maximum loading(average 967kN) and 2.7 times increase in the negative maximum loading(average 592.5kN) had resulted from the test of seismic resistant specimens with anchored and welded steel plate connections than that of unreinforced beam-column specimen. The maximum drift ratios were also shown between 1.0% and 1.4%.

• Journal of the Korea Concrete Institute
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• v.27 no.5
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• pp.489-499
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• 2015

This study suggested shear strength prediction model for retrofitted single-layered RC squat wall by providing column element as additional boundary element. This model revised existing shear strength prediction model of shear wall to consider detail and shear deformation capacity of column by assuming the length that concentrated shear deformation of the column is occurred. It was able to suggest additional compatibility condition related to shear strain of retrofitted of retrofitted shear wall at the ultimate state by using this length. Therefore, this study proposed a flow chart for predicting shear strength of the retrofitted shear wall considering this additional condition. Moreover, this study also proposed a method for predicting initial stiffness of the retrofitted shear wall by transforming the wall's resisting mechanism against to lateral load to a single diagonal strut mechanism. The proposed methods can predict shear strength and initial stiffness of not only the retrofitted shear wall of this study, also infilled RC shear wall in RC frame.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.5
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• pp.13-22
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• 2010

Masonry infill walls are frequently used as interior partitions and exterior walls in low- or middle- rise RC buildings. In the design and assessment of buildings, the infill walls are usually treated as non-structural elements and they are ignored in analytical models because they are assumed to be beneficial to the structural responses. Therefore, their influences on the structural response are ignored. In the case of buildings constructed in the USA in highly seismic regions, infill walls have a lower strength and stiffness than the boundary frames or they are separated from the boundary frames. Thus, the previously mentioned assumptions may be reasonable. However, these systems are not usually employed in most other countries. Therefore, the differences in the seismic behaviors of RC buildings with/without masonry infill walls, which are ignored in structural design, need to be investigated. In this study, structural analyses were performed for a masonry infilled low-rise RC moment-resisting frame. The infill walls were modeled as equivalent diagonal struts. The seismic behaviors of the RC moment-resisting frame with/without masonry infill walls were evaluated. From the analytical results, masonry infill walls can increase the global strength and stiffness of a structure. Consequently, the interstory drift ratio will decrease but seismic forces applied to the structure will increase more than the design seismic load because the natural period of the structure decreases. Partial damage of the infill walls by the floor causes vertical irregularity of the strength and stiffness.

• 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.

• Computers and Concrete
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• v.7 no.6
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• pp.523-532
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• 2010

If an infill wall in a reinforced concrete frame is shorter than the column height and there is no initial gap between the column and the infill wall, the short column effect can occur during an earthquake shaking. This form of damage is frequently observed in many earthquake-damaged buildings all around the world and especially in Turkey. In this study, an effective method, which consists of placing additional infill wall segments surrounding the short column, to prevent this type of failure is examined. The influence of adding infill wall in the reduction of the shear force in the short column is also investigated. A parametric study is carried out for one-storey infilled frames with one to five bays using the percentage of the additional infill wall surrounding the short column and the number of spans as the parameters. Then the investigation is extended to a case of a multistorey building damaged due to short column effect during the 1998 Adana-Ceyhan earthquake in Turkey. The results show that the addition of the infill walls around the potential short columns is an effective way to significantly reduce the shear force.

• Journal of the Earthquake Engineering Society of Korea
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• v.13 no.1
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• pp.35-43
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• 2009

Two types of piloti-type high-rise RC building structures having irregularity in the lower two stories were selected as prototypes, and nonlinear time history analysis was performed using OpenSees to verify the analysis technique and to investigate the seismic capacity of those buildings. One of the buildings studied had a symmetrical moment-resisting frame (BF), while the other had an infilled shear wall in only one of the exterior frames (ESW). A fiber model, consisting of concrete and reinforcing bar represented from the stress-strain relationship, was adapted and used to simulate the nonlinearity of members, and MVLEM (Multi Vertical Linear Element Model) was used to simulate the behavior of the wall. The analytical results simulate the behavior of piloti-type high-rise RC building structures well, including the stiffness and yield force of piloti stories, the rocking behavior of the upper structure and the variation of the axial stiffness of the column due to variation in loading condition. However, MVLEM has a limitation in simulating the abrupt increasing lateral stiffness of a wall, due to the torsional mode behavior of the building. The design force obtained from a nonlinear time history analysis was shown to be about $20{\sim}30%$ smaller than that obtained in the experiment. For this reason, further research is required to match the analytical results with real structures, in order to use nonlinear time history analysis in designing a piloti-type high-rise RC building.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.105-117
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• 2015

The purpose of this study is to develop a new seismic resistant method by using precast concrete wall panels for existing low-rise, reinforced concrete beam-column buildings such as school buildings. Three quasi-static hysteresis loading tests were experimentally performed on one unreinforced beam-column specimen and two reinforced specimens with L-type precast wall panels. The results were analyzed to find that the specimen with anchored connection experienced shear failure, while the other specimen with steel plate connection principally manifested flexural failure. The ultimate strength of the specimens was determined to be the weaker of the shear strength of top connection and flexural strength at the critical section of precast panel. In this setup of L-type panel specimens, if a push loading is applied to the reinforced concrete column on one side and push the precast concrete panel, a pull loading from upper shear connection is to be applied to the other side of the top shear connection of precast panel. Since the composite flexural behavior of the two members govern the total behavior during the push loading process, the ultimate horizontal resistance of this specimen was not directly influenced by shear strength at the top connection of precast panel. However, the RC column and PC wall panel member mainly exhibited non-composite behavior during the pull loading process. The ultimate horizontal resistance was directly influenced by the shear strength of top connection because the pull loading from the beam applied directly to the upper shear connection. The analytical result for the internal shear resistance at the connection pursuant to the anchor shear design of ACI 318M-11 Appendix-D except for the equation to predict the concrete breakout failure strength at the concrete side, principally agreed with the experimental result based on the elastic analysis of Midas-Zen by using the largest loading from experiment.