• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.1
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• pp.85-93
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• 2016

In this study, finite element analyses of masonry infilled frames using a general purpose FE program, ABAQUS, were conducted. Analysis models consisted of the bare frame, infilled frames with masonry wall thickness of 0.5B and 1.0B, respectively. The masonry walls were constructed using the concrete bricks which were generally used in Korea as infilled wall. The material properties of frames and masonry for the analysis were obtained from material tests. However, four times increased the tensile strength was used for 1.0B wall, which is seemingly due to the differences in locating the bricks. The force-displacement relation and development of crack from the FE analysis were very similar to those from the experiments. From the FEA results, contact force between the frame and masonry, distribution of shear force and bending moments in frame members were analyzed. Obtained contact stress shows a trianglur distribution, and the contact length for 0.5B speciment and 1.0B specimen were close to the value estimated using ASCE 41-06 equation and ASCE 41-13 equation, respectively. Obtained shear force and bending moment distribution seems to replicate actual behavior which originates from the contact stress and gap between the frame and masonry.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.5 s.57
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• pp.133-141
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• 2009

50 year-old masonry buildings which had been constructed using lime mortar have caused lots of problems because of using different material, cement mortar, when they repair them. Also, there is little information on structural capacities and details of masonry buildings built using lime mortar. In addition, it is difficult to evaluate the structural capacities of the buildings which were often constructed by untrained labors. To preserve the original masonry construction, the study on their construction materials and methodologies has to be carried out. This paper provides basic information for establishing standard details of masonry works using lime mortar in order to overcome these problems when cultural properties are repaired or retrofitted. To do this, compression tests of lime mortar were preformed with the parameters of mixing ratios, mixing material, curing time and curing conditions etc. Based on the test results, the differences between lime mortar and cement mortar were specified and the structural characteristics of lime mortar were also presented in this paper.

• Earthquakes and Structures
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• v.2 no.3
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• pp.233-256
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• 2011

This paper investigates the applicability of newly developed Cu-Al-Mn shape memory alloy (SMA) bars to retrofitting of historical masonry constructions by performing quasi-static tests of half-scale brick walls subjected to cyclic out-of-plane flexure. Problems associated with conventional steel reinforcing bars lie in pinching, or degradation of stiffness and strength under cyclic loading, and in their inability to restrain residual deformations in structures during and after intense earthquakes. This paper attempts to resolve the problems by applying newly developed Cu-Al-Mn SMA bars, characterized by large recovery strain, low material cost, and high machinability, as partial replacements for steel bars. Three types of brick wall specimens, unreinforced, steel reinforced, and SMA reinforced specimens are prepared. The specimens are subjected to quasi-static cyclic loading up to rotation angle enough to cause yielding of reinforcing bars. Corresponding nonlinear finite element models are developed to simulate the experimental observations. It was found from the experimental and numerical results that both the steel reinforced and SMA reinforced specimens showed substantial increment in strength and ductility as compared to the unreinforced specimen. The steel reinforced specimen showed pinching and significant residual elongation in reinforcing bars while the SMA reinforced specimen did not. Both the experimental and numerical observations demonstrate the superiority of Cu-Al-Mn SMA bars to conventional steel reinforcing bars in retrofitting historical masonry constructions.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.4
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• pp.116-124
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• 2011

RC frames with unreinforced masonry infiledl walls are common in worldwide. Since infilled walls are normally considered as non-structural elements, their presence is often ignored by engineers. In this study, to improve the seismic performance of masonry walls, hexagonal block was developed and the influence of masonry infilled wall on the seismic performance of reinforced concrete(RC) frames that were designed in accordance with current code provisions without the consideration of earthquake loadings are investigated. Two 1/2 scale, single story, single bay, frame specimens were tested. The parameters investigated included that the strength of infilled wallls with respect to that of the lateral load history. The experimental results indicate that infilled walls can significantly improve the lateral stiffness and strength of RC frames. The lateral loads developed by the infilled frame specimen is higher than that of the bare frame. It also indicates that infilled walls can be potentially used to improve the performance of existing nonductile frames. For this purpose. methods should be developed to avoid irreparable damage and catastrophic failure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.3
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• pp.113-121
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• 2015

Building using masonry accounts for most of the smaller houses in Korea but due to brittle behavior and low ductility the frequency of usage has decreased in recent years. Despite this, this form of building has been gaining attention overseas for its low cost in construction and environment-friendliness of the materials. As such, many studies are being conducted to resolve the disadvantages in structure. This study produced an specimen for masonry-filled wall and the intersection to confirm the difference in structural movement depends on the existence or lack of expansion joint and verified the reinforcement effect from inserting a connecting steel item (steel plate, stainless steel twist bar). The experiment results show that the specimen with a steel plate inserted saw an increase in durability and an improvement in the strength of the specimens, while the specimen that had stainless steel twists bar inserted saw an increase in ductility that did not cause brittle failure, indicating that the reinforcement effects of inserting a connecting steel item are effective.

• Earthquakes and Structures
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• v.5 no.2
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• pp.143-160
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• 2013

This paper presents the results of an experimental program concerning the efficiency of a specific strengthening technique which utilizes a small steel link element connected to the R/C frame through bracing elements. Brittle types of failure, especially at the connections between steel and concrete elements, can be avoided by appropriate design of the local details. Five single storey one bay R/C frames scaled 1:3 were constructed according to older codes with substandard details. The first one was a typical bare reference frame. The other four were identical to the first one, strengthened by steel bracing elements. The behavior of the strengthened frames is described with respect to the reference bare frame. The concrete frames were constructed according to older code provisions by the use of smooth steel bars, low strength concrete, sparsely spaced stirrups and substandard details. The strengthening scheme aimed to the increase of both strength and deformation capacity of the original R/C frame. The inelastic deformations are purposely concentrated to a short steel link element connecting the steel bracing to the R/C frame. The results show that the steel link element can increase considerably the strength and the energy dissipation capacity of the frame.

• Structural Engineering and Mechanics
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• v.18 no.1
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• pp.59-78
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• 2004

This paper is devoted to illustrate some numerical procedures to solve the boundary equilibrium problems of three-dimensional solids that are subjected to thermal strains. The constitutive equations take into account the bounded tensile strength of the material and they are presented in the framework of non-linear elasticity and small strains. The associated equilibrium problem is solved numerically by means of the finite element method and the numerical techniques, i.e. the Newton-Raphson method and the secant method, are revised in order to assure the solution convergence of the discretized problem. Some numerical examples are illustrated.

• Journal of the Korea Concrete Institute
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• v.18 no.4 s.94
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• pp.535-542
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• 2006

In Seoul, more than 80 percent of residential buildings are constructed with unreinforced masonry(URM) buildings in early 1970 to 1990. In general, URM buildings have the advantages of reducing the construction time and easy to construction. However, URM buildings do not have enough strength against the lateral force. Moreover, low rise buildings have not adopted seismic designs, and for that reason a critical damage is expected with an earthquake. And also, the necessity of the seismic performance evaluation of existing building structures is raised through the Taiwan earthquake in 1999. The purpose of this study is to provide basic information for unreinforced masonry building in Korea by application of the proposed seismic evaluation method. In this study, seismic capacities of 50 existing unreinforced masonry buildings are evaluated based on the proposed method. Also, relationships of seismic capacities between Korean earthquake damage ratios of korean unreinforced masonry buildings are estimated. Results of this study were as follows; 1)Seismic retrofit was needed $8{\sim}48%$ in Korean unreinforced masonry buildings. 2)Korean unreinforced masonry buildings were expected to have severe damage under the earthquake intensity level experienced in Japan.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.3
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• pp.121-129
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• 2017

In this paper, the shake table test for the masonry infilled reinforced concrete frame with non-seismic details was carried out in order to evaluate its dynamic behaviour and damage under seismic condition. The tested specimens were the RC frame and the masonry infilled RC frame and the dynamic characteristics, such as a resonant period, acceleration response, displacement response and base shear force response, were compared between them. As a result of the shake table test, RC frame specimen had flexural cracks at the top and bottom of the column and shear cracks at the joints. In the case of masonry infilled RC frame, the damage of the frame was relatively minor but the sliding cracks and diagonal shear cracks on the masonry wall were severe at the final excitation. The resonant period of infilled RC frame specimen was shorter than that of the RC frame specimen because the masonry infill contributed to increase the stiffness. The maximum displacement response of the infilled RC frame specimen was decreased by about 20% than the RC frame specimen. It was analyzed that the masonry infill wall applied in this study contributed to increase the lateral strength of the RC frame with non - seismic detail by about 2.2 times and the stiffness by about 1.6 times.

• Advances in concrete construction
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• v.2 no.4
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• pp.249-259
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• 2014

Mortar is a masonry product which is matrix of concrete. It consists of binder and fine aggregate and moreover, it is an essential associate in any reinforced structural construction. The strength of mortar is a special concern to the engineer because mortar is responsible to give protection in the outer part of the structure as well as at a brick joint in masonry wall system. The purpose of this research is to investigate the compressive strength and tensile strength of mortar, which are important mechanical properties, by replacing the cement and sand by stone dust. Moreover, to minimize the increasing demand of cement and sand, checking of appropriateness of stone dust as a construction material is necessary to ensure both solid waste minimization and recovery by exchanging stone dust with cement and sand. Stone dust passing by No. 200 sieve, is used as cement replacing material and retained by No. 100 sieve is used for sand replacement. Sand was replaced by stone dust of 15%, 20%, 25%, 30%, 35%, 40%, 45% and 50% by weight of sand while cement was replaced by stone dust of 3%, 5%, and 7% by weight of cement. Test result indicates that, compressive strength of specimen mix with 35% of sand replacing stone dust and 3% of cement replacing stone dust increases 21.33% and 22.76% respectively than the normal mortar specimen at 7 and 28 days while for tensile it increases up to 13.47%. At the end, optimum dose was selected and crack analysis as well as discussion also included.