Due to the aging of a building, 38.8% (about 2.82 million buildings) of the total buildings are old for more than 30 years after completion and are located in a blind spot for an inspection, except for buildings subject to regular legal inspection (about 3%). Such existing buildings require users to self-inspect themselves and make efforts to take preemptive risks. The scope of this study was defined as the general public's visual self-inspection of buildings and was limited to structural members that affect the structural stability of old buildings. This study categorized possible damage to reinforced concrete to check the structural safety of buildings and proposed a checklist to prevent the damage. A damage assessment methodology was presented during the inspection, and a self-inspection scenario was tested through a chatbot connection. It is believed that it can increase the accessibility and convenience of non-experts and induce equalized results when performing inspections, according to the chatbot guide.

Existing reinforced concrete building structures constructed before 1988 have seismically-deficient reinforcing details, which can lead to the premature failure of the columns and beam-column joints. The premature failure was resulted from the inadequate bonding performance between the reinforcing bars and surrounding concrete on the main structural elements. This paper aims to quantify the bond-slip effect on the dynamic responses of reinforced concrete frame models using finite element analyses. The bond-slip behavior was modeled using an one-dimensional slide line model in LS-DYNA. The bond-slip models were varied with the bonding conditions and failure modes, and implemented to the well-validated finite element models. The dynamic responses of the frame models with the several bonding conditions were compared to the validated models reproducing the actual behavior. It verifies that the bond-slip effects significantly affected the dynamic responses of the reinforced concrete building structures.

As the damage caused by earthquakes gradually increases, seismic retrofitting for existing public facilities has been implemented in Korea. Several types of structural analysis methods can be used to evaluate the seismic performance of structures. Among them, for nonlinear dynamic analysis, the hysteresis model must be carefully applied because it can significantly affect the behavior. In order to find a hysteresis model that predicts rational behavior, this study compared the experimental results and analysis results of the existing non-seismic reinforced concrete frames. For energy dissipation, the results were close to the experimental values in the order of Pivot, Concrete, Degrading, and Takeda models. The Concrete model underestimated the energy dissipation due to excessive pinching. In contrast, the other ones except the Pivot model showed the opposite results with relatively little pinching. In the load-displacement curves, the experimental and analysis results tended to be more similar when the column axial force was applied to columns.

The purpose of this study is to pushover analyze existing reinforced concrete(RC) frames strengthened by L-type precast concrete(PC) wall panels. Cyclic loading tests were performed on the partially infilled reinforced concrete(RC) frames by L-type PC wall panels. Based on the results of experimental test, the nonlinear pushover analysis was practiced by using a computer program. The analysis models were designed with two ways according to the test result. The PC wall panel and the RC column exhibited almost composite behavior by using brace when push loading applied. The two structures also exhibited independent behavior when pull loading applied. The results of pushover analysis models generally conform to the experimental results. The ratios of the maximum lateral load measured in the strengthened specimens from the analysis varied between 0.93 and 1.01 in forward cycles, and between 0.84 and 0.90 in backward cycles. The initial stiffness values of the analysis were less than the test values for all strengthened specimens. The ratio of the initial stiffness obtained through testing compared to the values from the analysis varied between 0.72 and 0.90.

The purpose of this study is to make a generalized analytical based on the proposed experiments on reinforced concrete(RC) partially infilled frames by U-type precast concrete(PC) wall panels with openings. RC frame and PC wall panels were connected with different strengths. Therefore, we developed modified strut-tie model(STM) with two seismic retrofitting specimens and conducted a nonlinear analysis by using a computer analysis program. Based on the test results, truss member of modified STM was designed, applying the strut-tie model theory of ACI 318M-11 Appendix- A. As a result, the modified STM analysis results were very similar to the experimental results. As a result of the load-displacement curve comparison, the failure load were similar within 5∼17% of error range. In particular, the experimental results and the results of modified STM analysis show that the failure behavior almost matched.

Cyclic loading test was performed on the partially infilled reinforced concrete(RC) frames by L-type precast concrete(PC) wall panels with the connections of two different strength. Based on the results of experimental test, the nonlinear analysis was practiced with modified strut-tie model(STM) method by using a computer program. Truss member of modified STM was designed, applying the strut-tie model theory of ACI 318M-11 Appendix-A. Modified STM was designed with two ways according to the test result. PC wall panel and RC frame were assumed to composite when push loading applied. The PC and RC structures were also assumed to behave non-composite and those two structures connected with link(top connector) when pull loading applied. The connection was designed by using elastic link of program. The results of analytical modified STM process generally conform to the experimental results. The failure load and the failure mode of the specimens could be predicted using modified STM. The ratio of failure load measured in specimens to analytical values were between 0.83∼1.16. The member or connection which was failed in experiment yield in the results of modified STM. The failure mode perfectly matched.

When reinforcing an existing reinforced concrete beam-column building with a precast concrete panel, special connection between the PC member and the RC member is required to solve the time dependent deformation of the RC member and to receive the large shear forces. The aim of this study is to obtain the shear strength of upper connection between the existing RC beam-column and infilled PC wall panels in experimentally and theoretically. Thus, the static shear loading tests were conducted on the 6 specimens with the plate connection. Shear failure was resulted from the weakest portion of interior PC panel, exterior RC, and the connection, when the PC portion which located at the center of specimen was pulled upward from the bottom. T he experimental result was compared with analytical result from ACI 318M-14 Chapter 17 for the shear strength of post-installed anchor and PCI Handbook 7th edition 6.8 Structural Steel Corbel (PCI Design Handbook 7th edition, 2010) for the strength of cast-in H-beam. The analytical and experimental results show final failure at the same location. The failure loading of experiment showed larger than average 6% to that of the analysis.

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.

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%.

In this study, shaking table test was carried out to evaluate the seismic behavior and performance of low-rise reinforced concrete (RC) piloti structures with and without retrofit. The specimens were designed considering the characteristics of existing building with pilotis such as natural period, distribution factor of strength and stiffness between columns and core wall on the first soft story. The test for the non-retrofit specimen showed that damage was concentrated on the stiffer member on the same floor as the core wall failed by shear fracture whereas columns experienced slight flexural cracks. Considering the failure mode of the non-retrofit specimen, the retrofit method using steel rod damper was presented for improving the seismic performance of piloti structures. The results of the test for retrofit specimen revealed that the retrofit method was effective for controlling the damage as the main RC structural members were not destroyed and most of input energy was dissipated by hysteretic behavior of the damper.

The interest for the stability of the structures against earthquake, which is increasing recently, is rapidly increasing. But, currently, school buildings among the reinforced concrete(RC) structures in Korea are not designed with seismic design or there are many cases of being designed with the old seismic design code, so it is estimated to have not only lives but also a great deal of economic damage are likely to occur when an earthquake occurs. In this study, proposed horizontal friction system(HFS) with rotary friction damper installed as a method to reinforce strength and hardness and to increase ductility for the low story structure of 5 stories or lower such as school buildings. For the seismic retrofitting design with horizontal friction system in which rotary friction damper is installed, Peak displacement response ratio according to elastic and inelastic behavior and ductility demand is calculated to decide elastic stiffness and strength of the HFS, design model and procedure to decide the capacity of HFS thereof is decided, and the feasibility and performance are reviewed through pushover analysis.

In this study, the seismic performance of RC school buildings which were not designed according to earthquake-resistance design code were evaluated by using response spectrum and push-over analyses. From the results of analysis, the efficiency of the seismic retrofitting methods RC shear wall, steel frame, RC frame and PC wing wall for existing RC school buildings was evaluated and analysised. The analysis result indicate that the inter-story drift concentrated in the first floor and most plastic hinge forms in the column of the first story. And results of analysis of the efficiency of the seismic retrofitting indicate that inter-story drift significantly reduced and ductile behavior is expected.

본 연구에서는 기존 철근콘크리트건물 보-기둥 접합부의 내진 성능을 개선하기 위하여 탄소섬유를 사용하여 구조물을 보강한 후 실험을 수행하였다. 이를 위하여 6개의 철근콘크리트 보-기둥 접합부를 제작하였으며, 지진하중과 같은 반복하중이 작용할 때 보강재료 및 보강영역 등을 변수로 하여 실험을 수행하여 각 보강변수에 따른 보강효과를 평가하였다. 본 실험을 통하여 구조물의 내진 성능 및 연성능력을 증진시킬 목적으로 새로운 보강재료(탄소섬유판, 탄소섬유봉, 탄소섬유쉬트)로 설계된 보강 실험체(RPC-CP2, RPC-CR, RJC-CP, RJC-CR)들은 내력증진은 물론이고 안정적인 이력거동을 확보할 수 있었다.

This study researched problems of safety inspection method and current legislative system for the structure safety evaluation of Rahmen structure affected by remodeling. The elements of weight increase were examined in terms of differences of load moment, shear force, compressive stress and amount of steel before and after remodeling by structure analysis. The thorough examination for impacts of weight increase is indispensable to change of use or extension.

본 연구는 해외각국의 RC건물의 내진화기술 가운데, 일본의 기존 RC건물에 대한 내진성능의 평가수법인 내진진단규준의 현황을 소개함과 동시에 그 적용사례 및 지진대책에의 활용가능성을 분석검토하여, 향후 한국실정에 맞는 RC건물의 내진화기술의 개발에 기초적인 자료로서 활용하고자 하는 것이 주목적이다. 이를 위해 본 연구에서는 일본의 동경도에서 최근 실시되어진 지진경험이 없는 RC건물의 내진성능을 내진진단규준에 의한 진단결과인 구조내 진지표(Is)치를 중심으로 통계학적으로 분석하여, 이미 조사되어진 타 지역의 내진성능과 비교검토하였고, 또한 확률론에 입각하여 대상지역의 Is치의 분포특성과 이미 지진 피해를 받은 지역 건물의 Is치 분포특성을 비교검토하여 지진피해율을 추정하였다. 본 연구의 결과는 지진에 대한 보강건물의 효율적인 선정 등, 지진대책에 기본적인 자료로서 활용이 가능하며, 또한 일본의 내진성능 평가방법, 통계학적인 분석방법, 확률론에 입각한 지진피해율 평가방법 등의 방법론은 향후 한국의 RC건물에 대한 내진화기술의 개발에 활용이 가능하다고 사료된다.

When reinforcing an existing reinforced concrete beam-column building with a precast concrete panel, special connection between the PC member and the RC member is required to solve the time dependent deformation of the RC member and to receive the large shear forces. The aim of this study is to obtain the shear strength of upper connection between the existing RC beam-column and infilled PC wall panels in experimentally and theoretically. Thus, the static shear loading tests were conducted on the 6 specimens with the plate connection. Shear failure was resulted from the weakest portion of interior PC panel, exterior RC, and the connection, when the PC portion which located at the center of specimen was pulled upward from the bottom. The experimental result was compared with analytical result from ACI 318M-14 Chapter 17 for the shear strength of post-installed anchor and PCI Handbook 7th edition 6.8 Structural Steel Corbel (PCI Design Handbook 7th edition, 2010) for the strength of cast-in H-beam. The analytical and experimental results show final failure at the same location. The failure loading of experiment showed larger than average 6% to that of the analysis.

When reinforcing an existing reinforced concrete beam-column building with a precast concrete panel, special connection between the PC member and the RC member is required to solve the time dependent deformation of the RC member and to receive the large shear forces. The aim of this study is to obtain the shear strength of upper connection between the existing RC beam-column and infilled PC wall panels in experimentally and theoretically. Thus, the static shear loading tests were conducted on the 6 specimens with the plate connection. Shear failure was resulted from the weakest portion of interior PC panel, exterior RC, and the connection, when the PC portion which located at the center of specimen was pulled upward from the bottom. The experimental result was compared with analytical result from ACI 318M-14 Chapter 17 for the shear strength of post-installed anchor and PCI Handbook 7th edition 6.8 Structural Steel Corbel (PCI Design Handbook 7th edition, 2010) for the strength of cast-in H-beam. The analytical and experimental results show final failure at the same location. The failure loading of experiment showed larger than average 6% to that of the analysis.

이 연구의 목표는 학교 건물과 같은 저층 보-기둥 철근콘크리트 구조 건물에서 프리캐스트 벽패널을 사용한 새로운 내진보강 방법 을 개발하는데 있다. 1개의 무 보강 보-기둥 실험체와 U형 PC 패널로 보강한 2개의 보강 보-기둥 실험체에 대한 정적 이력 하중실험을 진행하 였다. 앵커 접합부 실험체는 전단 파괴될 것으로 해석되었고 철판 용접 접합부 실험체는 휨 파괴할 것으로 예측되었다. 실험체의 종국 내력은 상부 접합부의 전단 내력과 PC 패널 절곡 부 휨 위험단면에서 휨 내력 중 약한 것으로 결정되었다. 이 실험체에서, 한쪽 RC기둥이 가 하중(미는 실험 하중)을 받아 PC 패널 부재를 밀게 된다면, 다른 쪽 내부 수직부재는 상부 전단 접합부로부터 부 하중(당기는 실험 하중)을 받게 되어있었 다. 가 하중을 받는 2개의 부재는 합성 휨 거동이 지배적이므로 합성단면의 휨 내력이 실험체의 최종 내력을 결정하게 되지만, 이 경우 최종 내 력에 대하여 상부 전단 접합부 강도의 직접적인 영향은 없다고 볼 수 있다. 그러나 부 하중(당기는 하중)을 받는 RC 기둥과 PC 패널 부재는 비 합성 거동이 지배적이고 실험체의 최종 내력은 상부 전단 접합부 전단내력의 크기에서 직접 영향을 받는 것으로 파악되었다. ACI 318M-11 Appendix-D 앵커 전단설계에 기초한 전단내력 그리고 실험에서 얻은 최대하중을 적용하여 마이다스 젠 탄성설계에 의하여 계산한 전단 외력 에 대한 비교 해석결과는 실험결과와 일치하는 해석결과를 보여주었다.

In this study, impact performance of steel fiber-reinforced concrete was evaluated using existing impact formulae. The existing formulae were evaluated as to whether they can predict impact performance of steel fiber-reinforced concrete well.

이 연구의 목표는 학교 건물과 같은 저층 보－기둥 철근콘크리트 구조 건물에서 프리캐스트 벽패널을 사용한 새로운 내진보강 방법을 개발하는 것이다. 1개의 무 보강 보－기둥 실험체와 U형 PC 벽패널로 보강한 2개의 보강 보－기둥 실험체에 대한 정적 이력 하중실험을 진행하였다. 앵커접합 PR1-UA 실험체와 철판접합 PR1-UP 실험체는 무 보강 실험체보다 평균 2.8배(평균 591.8 kN)의 강도 증가를 보여 주었다. 최대 변위비도 1.4%에서 2.7%사이 값을 보여주었다. RC 골조 우측 상단에서 좌측방향으로 가력 할 때 우측에 있는 RC 기둥과 보강 PC 패널의 수직 요소는 완전 합성상태로 가정하였고, 좌측에 있는 RC 기둥과 PC 패널은 완전 비 합성 거동하는 것으로 가정하여 해석한 결과 전체적인 휨 거동은 실험 결과와 대체적으로 부합하는 것으로 판단되었다.