• Architectural research
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• v.20 no.1
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• pp.17-25
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• 2018

Countermeasures against earthquake disasters such as the seismic capacity evaluation and/or retrofit schemes of buildings, especially existing low-rise reinforced concrete buildings, have not been fully performed since Korea had not experienced many destructive earthquakes in the past. However, due to more than 1200 earthquakes with low or moderate intensity in the off-coastal and inland of Korea during the past 20 years, and due to the recent moderate earthquakes in Korea, such as the 2016 Gyeongju Earthquake with M=5.8 and the 2017 Pohang Earthquake with M=5.4, the importance of the future earthquake preparedness measures is highly recognized in Korea. The main objective of this study is to provide the basic information regarding seismic capacities of existing low-rise reinforced concrete buildings in Korea. In this paper, seismic capacities of 14 existing low-rise reinforced concrete public buildings in Korea are evaluated based on the Japanese Standard for Evaluation of Seismic Capacity of Existing Reinforced Concrete Buildings. Seismic capacities between existing buildings in Korea and those in Japan is compared, and the relationship of seismic vulnerability of Korean buildings and Japanese buildings damaged due to severe earthquakes are also discussed. Results indicated that Korean existing low-rise reinforced concrete buildings have a narrow distribution of seismic capacities and they are relatively lower than Japanese buildings, and are also expected to have severe damage under the earthquake intensity level experienced in Japan. It should be noted from the research results that the high ductility in Korean existing low-rise buildings obtained from the Japanese Standard may be overestimated, because most buildings investigated herein have the hoop spacing wider than 30 cm. In the future, the modification of strength and ductility indices in the Japanese Standard to propose the seismic capacity evaluation method of Korean buildings is most needed.

• Computers and Concrete
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• v.26 no.4
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• pp.317-325
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• 2020

A precise estimation of the natural time period of buildings improves design quality, causes a significant reduction of the buildings' weight, and eventually leads to a cost-effective design. In this study, in order to optimise the reinforced concrete frames design, some symmetrical and unsymmetrical buildings composed of solid and hollow members have been simulated using finite element software SAP 2000. In numerical models, different parameters such as overturning moment, story drift, deflection, base reactions, and stiffness of the buildings were investigated and the results have been compared with strength and serviceability limit criteria proposed by Australian Standard (AS 3600 2018). Comparing the results of the numerical modelling with existing standards and performing a cost analysis proved the merits of hollow box sections compared to solid sections. Finally, based on numerical simulation results, two equations for natural time period of moment resisting reinforced concrete buildings have been presented. Both derived equations reflected higher degree of correlation and reliability with different complexities of building when compared with existing standards and relationships provided by other scholars. Therefore, these equations will assist practicing engineers to predict elastic behaivour of structures more precisely.

• 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.

• Structural Engineering and Mechanics
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• v.30 no.5
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• pp.535-558
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• 2008

This study evaluates seismic performance of the school buildings with the selected template designs in Turkey considering nonlinear behavior of reinforced concrete components. Six school buildings with template designs were selected to represent major percentage of school buildings in medium-size cities located in high seismic region of Turkey. Selection of template designed buildings and material properties were based on field investigation on government owned school buildings in several cities in western part of Turkey. Capacity curves of investigated buildings were determined by pushover analyses conducted in two principal directions. The inelastic dynamic characteristics were represented by equivalent single-degree-of-freedom (SDOF) systems and their seismic displacement demands were calculated under selected ground motions. Seismic performance evaluation was carried out in accordance with recently published Turkish Earthquake Code that has similarities with FEMA-356 guidelines. Reasons of building damages in past earthquakes are examined using the results of performance assessment of investigated buildings. The effects of material quality on seismic performance of school buildings were investigated. The detailed examination of capacity curves and performance evaluation identified deficiencies and possible solutions for template designs.

• Wind and Structures
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• v.29 no.3
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• pp.209-223
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• 2019

The assessment of wind-induced vibration for tall reinforced concrete (RC) buildings requires the accurate estimation of their dynamic properties, e.g., the fundamental vibration periods and damping ratios. In this study, RC frame-shear wall systems designed under gravity and wind loadings have been evaluated by utilising 3D FE modelling incorporating eigen-analysis to obtain the elastic periods of vibration. The conducted parameters consist of the number of storeys, the plan aspect ratio (AR) of buildings, the core dimensions, the space efficiency (SE), and the leasing depth (LD) between the internal central core and outer frames. This analysis provides a reliable basis for further investigating the effects of these parameters and establishing new formulas for predicting the fundamental vibration periods by using regression analyses on the obtained results. The proposed constrained numerically based formula for vibration periods of tall RC frame-shear wall office buildings in terms of the height of buildings reasonably agrees with some cited formulas for vibration period from design codes and standards. However, the same proposed formula has a high discrepancy with other cited formulas from the rest of design codes and standards. Also, the proposed formula agrees well with some cited experimentally based formulas.

• Journal of the Korean Society of Industry Convergence
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• v.15 no.1
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• pp.29-36
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• 2012

Reinforced concrete shear walls and X-type steel braces were applied in seismic retrofit techniques for seismic performance evaluation of school buildings constructed in accordance with standard design announced by the ordinance of the ministry of construction in 1980s. Seismic performance evaluation was based on FEMA 356 using response spectrum as elastic analysis and conducted to pushover analysis with nonlinear static analysis. The maximum displacement ratio between floors in 4th and 3rd floors of the existing school buildings was less than 1.0%, which was functioning level in FEMA 356. However, because plastic hinge occurs somewhat in structural members according to the results of pushover analysis, partial reinforcement will be required. X-direction of the maximum lateral displacement of reinforced concrete shear walls than X-type steel braces was 45% and 32% in 4th and 3rd floors of school buildings, and Y-direction was 18% and 17%, respectively.

• Advances in concrete construction
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• v.2 no.4
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• pp.261-280
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• 2014

In many parts of the world, reinforced concrete (RC) buildings, designed and built in accordance with older codes, have suffered severe damage or even collapse as a result of recent near-fault earthquakes. This is particularly due to the deficiencies of most of the older (and even some of the recent) codes in dealing with near fault events. In this study, a tested three-storey frame designed for gravity loads only was selected to represent those deficient buildings. Nonlinear time history analyses were performed, followed by damage assessment procedures. The results were compared with experimental observation of the same frame showing a good match. Damage and fragility analyses of the frame subjected to 204 pulse-type motions were then performed using a selected damage model and inter-storey drifts. The results showed that the frame located in near-fault regions is extremely vulnerable to ground motions. The results also showed that the damage model better captures the damage distribution in the frame than inter-storey drifts. The first storey was identified as the most fragile and the inner columns of the first storey suffered most damage as indicated by the damage index. The findings would be helpful in the decision making process prior to the strengthening of buildings in near-fault regions.

• Journal of the Korean Society of Safety
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• v.25 no.3
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• pp.100-106
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• 2010

Most of the school buildings were built before the seismic code was established. To consider the sunlight and ventilation to the partition walls are built about 1m height beside columns at typical school buildings. For the reason, columns which is consisted school building occur brittle failure shape by the reduced effective depth. In this study, experimental test for retrofitting effect by Aramid Fiber Reinforced Polymers(AFRP) strips on masonry infilled reinforced concrete(RC) frames is performed. The test results were to ensured enough time to evacuate due to the enhancement of ductility and strength of school buildings to withstand earthquakes using AFRP strips.

• Journal of the Korea Concrete Institute
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• v.27 no.2
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• pp.147-155
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• 2015

A new SRCF (Steel Reinforced Concrete Frame) external connection method for seismic strengthening of medium-and low-rise reinforced concrete buildings is reported in this paper. The SRCF method, proposed in this study, is capable of carrying out the seismic retrofitting construction while residents can live inside building. The method is one of the strength design approach by retrofit which can easily increase the ultimate lateral load capacity of concrete buildings controlled by shear. The pseudo-dynamic test, designed using a existing school building in Korea, was carried out in order to verify the seismic strengthening effects of the proposed method in terms of the maximum load carrying capacity and deformation. Test results revealed that the proposed SRCF strengthening method installed in RC frame enhanced conspicuously the strength and deformation capacities, and the method can resist markedly under the large scaled earthquake intensity level.

• Structural Engineering and Mechanics
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• v.82 no.1
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• pp.55-67
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• 2022

The precast reinforced concrete frame system is a method for industrialization of construction. However, the seismic performance factor of this structural system is not explicitly clarified in some existing building codes. In this paper, the seismic performance factor for the existing precast concrete building frame systems with cast-in-situ reinforced shear walls were evaluated. Nonlinear behavior of the precast beam-column joints and cast-in-situ reinforced shear walls were considered in the modeling of the structures. The ATC-19's coefficient method was used for calculating the seismic performance factor and the FEMA P-695's approach was adopted for evaluating the accuracy of the computed seismic performance factor. The results showed that the over-strength factor varies from 2 to 2.63 and the seismic performance factor (R factor) varies from 5.1 to 8.95 concerning the height of the structure. Also, it was proved that all of the examined buildings have adequate safety against the collapse at the MCE level of earthquake, so the validity of R factors was confirmed. The obtained incremental dynamic analysis (IDA) results indicated that the minimum adjusted collapse margin ratio (ACMR) of the precast buildings representing the seismic vulnerability of the structures approximately equaled to 2.7, and pass the requirements of FEMA P-695.