일반적으로 지중구조물은 지상구조물보다 지진하중 작용 시 상대적으로 작은 영향을 받는다. 그러나 많은 연구자들은 심각한 지중구조물 손상에 대해 보고하고 있으며 동적 흙-구조물 상호작용에 대한 지속적인 연구를 수행하고 있다. 본 연구에서는 유한요소해석 프로그램을 활용한 흙-구조물 상호작용을 지중구조물에 적용하고 지중구조물 하중저감기법인 ETI의 지오폼을 해석변수로 경감효과 및 최적 지오폼을 제안하고자 한다. 해석연구에 고려된 지오폼은 EPS 12, EPS 15, EPS 19이다. 해석 결과로부터 지진하중시 최대 50%까지 지중하중이 경감되었으며, 수평처짐은 26%, 수직처짐은 8%이 경감되었다. 본 해석연구를 토대로 ETI 공법을 적용한 지중구조물이 정적 및 지진하중 하에서도 하중의 영향을 경감시키는 것을 확인할 수 있었다.

콘크리트 구조물 표면에 발생하는 균열은 사용자에게 심리적인 불안감을 제공하며, 장기간 열려있는 큰 폭의 균열은 구조 물의 사용성능 및 내구성에 영향을 준다. 국내에서는 건축물을 포함한 시설물의 노후화에 따른 안전관리를 위해 균열정도를 파악하는 조사가 인력에 의한 육안조사로 수행되고 있지만 인력의 고비용성과 객관성 미흡 등의 문제점이 대두되고 있다. 이를 해결하기 위해 영상분석을 통한 균열 추출 등 다양한 연구가 수행되고 있으나 균열인식 정확도 향상에 2차원 영상 분석만으로는 한계가 있다. 따라서, 본 연구에서는 기존 2차원 영상 분석의 한계를 극복하기 위하여 3차원 특성을 정확하게 파악할 수 있는 3차원 광삼각 스캐닝기법을 활용하여 콘크리트 구조물 표면의 균열정보를 획득하는 기법을 개발하였다. 본 하 드웨어의 개발과 더불어 균열 패턴분석을 위한 획득된 균열의 세분화와 균열의 특성분석 알고리즘을 개발하였으며, 이를 실제 콘크리트 빔의 균열 탐지 적용을 통해 검증하였다.

In current research, it was attempted a preliminary design and evaluation of non-uniform ultra high-strength concrete (UHSC) truss members. UHSC used here has the compressive strength of 180 MPa, the tensile strength of 8 to 20 MPa, and the tensile strain after cracks up to 2%. By the three-dimensional finite element stress analysis as well as strut-tie approach on concrete solid beams, the non-uniform truss shape of UHSC truss was designed with the architectural esthetic concept. In a series of examples, to compare with conventional concrete members, the proposed UHSC truss members have advantages in capabilities of the slender design with minimum weight with high performances under transverse loadings as well as the aesthetically non-uniform design for spatial structures.

The purpose of this study was to develop a carbon fiber sheet with embedded fiber optic sensor for maintenance and performance improvement of aged concrete bridges. The carbon fiber sheet reinforcement method can separate the concrete and the carbon fiber sheet, so it is necessary to investigate the bond performance level. However, separation of concrete and carbon fiber sheet and investigation of concrete scaling phenomenon are carried out by human, so it is difficult to secure objectivity and accurate investigation. Therefore, in this study, a method to confirm the bond level of carbon fiber sheet by reinforcing with a carbon fiber sheet with a fiber optic sensor was examined. In this study, we investigated the strain of fiber optic sensor embedded in carbon fiber sheet to identify the separate point of carbon fiber sheet. The strain measured by fiber optic sensor was measured by numerical analysis. The strain rate of the carbon fiber sheet was compared with that of the carbon fiber sheet. As a result, it was confirmed that the strain was changed at the point where the carbon fiber sheet was separated, and the strain occurred in the carbon fiber sheet was examined to predict the separate point.

In this study, natural period formular is presented for a RC shear wall structure with H-, T-, and L-shaped wall sections. The natural period formular proposed by Goel and Chopra and adopted in ASCE 7-10 was modified by using the ratio of the flange and web wall area. The natural periods of structures with H-shaped wall were numerically obtained, the results indicated that the ASCE 7-10 could not consider the natural period variation according to the length of the flange wall, but the proposed formula could do. Especially, ASCE 7-10 estimated much longer periods than eigenvalue analysis, and this implies that conservative seismic design is difficult. The periods by eigenvalue analysis exist between the upper and lower bounds given by the proposed formula, and conservative design is possible by using the proposed lower bound value. In order to verity the effectiveness of the proposed method, actual residential buildings with various types of flange walls are considered. Ambient vibration tests, eigenvalue analyses, and nonlinear dynamic analyses were conducted and the periods were compared with the values by ASCE 7-10 and the proposed formula. The results showed that the proposed formula could estimate more accurately the periods than ASCE 7-10.

PURPOSES: In this study, a three-dimensional nonlinear finite element analysis (FEA) model for airport concrete pavement was developed using the commercial program ABAQUS. Users can select an analysis method and set the range of input parameters to reflect actual conditions such as environmental loading.METHODS : The geometrical shape of the FEA model was chosen by considering the concrete pavement located in the third-stage construction site of Incheon International Airport. Incompatible eight-node elements were used for the FEA model. Laboratory test results for the concrete specimens fabricated at the construction site were used as material properties of the concrete slab. The material properties of the cement-treated base suggested by the Federal Aviation Administration(FAA) manual were used as those of the lean concrete subbase. In addition, preceding studies and pavement evaluation reports of Incheon International Airport were referred for the material properties of asphalt base and subgrade. The kinetic friction coefficient between the concrete slab and asphalt base acquired from a preceding study was used for the friction coefficient between the layers. A nonlinear temperature gradient according to slab depth was used as an input parameter of environmental loading, and a quasistatic method was used to analyze traffic loading. The average load transfer efficiency obtained from an Heavy falling Weight Deflectomete(HWD) test was converted to a spring constant between adjacent slabs to be used as an input parameter. The reliability of the FEA model developed in this study was verified by comparing its analysis results to those of the FEAFAA model.RESULTS : A series of analyses were performed for environmental loading, traffic loading, and combined loading by using both the model developed in this study and the FEAFAA model under the same conditions. The stresses of the concrete slab obtained by both analysis models were almost the same. An HWD test was simulated and analyzed using the FEA model developed in this study. As a result, the actual deflections at the center, mid-edge, and corner of the slab caused by the HWD loading were similar to those obtained by the analysis.CONCLUSIONS : The FEA model developed in this study was judged to be utilized sufficiently in the prediction of behavior of airport concrete pavement.

본 연구에서는 콘크리트 석션식 지지구조물을 사용한 해상풍력발전시스템의 지진응답 해석을 수행하여 그 거동 특성을 파악한다. 전체 시스템을 RNA, 타워, 지지구조물로 구성된 구조계와 이에 접하고 있는 유체 및 지반의 부분구조로 분리하여 운동방정식을 유도한다. 구조계에 작용하는 유체의 동수압과 지반의 상호작용력을 산정하고, 이를 구조계의 운동방정식과 결합하여 전체 시스템의 지배방정식을 도출한 후, 이 방정식의 해를 구하여 해상풍력발전시스템의 지진응답을 계산한다. 해 석 결과로부터 지반-구조물 상호작용은 콘크리트 석션식 지지구조물에 의해 지지된 해상풍력발전시스템의 지진응답을 크게 증가시킬 수 있음을 확인할 수 있다. 특히, 지반의 유연성으로 인해 시스템의 고차 고유모드 응답이 증가할 수 있으므로, 해 상풍력발전시스템의 동적거동 산정 시에는 반드시 지반-구조물 상호작용의 효과를 고려하여야 할 것이다.

3D프린팅 공법은 설계 데이터 및 제품의 특성에 따라 액체 또는 분말가루 형태의 폴리머, 금속 등의 재료를 사용한다. 3D프린팅 공법의 제조방식은 적층방식으로 입체구조물을 층층이 쌓아올려 3차원형상을 제조하는 방식을 말한다. 3D프린팅 기술은 30년(1980년대) 전에 개발된 기술이지만 최근 몇 년 사이에 업계의 관심이 집중되고 있다. 3D프린팅 기술의 적용범위는 기계 산업분야에서 의료분야, 항공 분야, 건설 및 토목분야 등으로 그 범위가 점점 확대되어가 고 있다 컨투어크래프팅(Contour Crafting)은 미국 남가주대학에서 15년(2000) 전에 세라믹재료를 이용하여 개발된 3D프린팅 공법이다. Trowel 구조를 도입하여 3D프린팅 공법의 핵심적 단점인 외부표면을 매끄럽게 하면서 3D자유형상을 제작하는 것이다. 현재의 이 공법은 시멘트를 이용 하여 구조물의 부가구성물뿐만이 아니라 전체구조물을 자동으로 만드는 것을 목적으로 한다. 또한 각층의 두께 및 폭이 일반 3D프린팅 공법과 비교할 수 없이 크고 넓게 함으로 건설 및 토목분야의 적용이 가능하다. 특히, 콘크리트재료를 이용하여 토목용 2차구조물 제작에 대한 기초적인 조사 및 개념을 상세히 설명된다

As an alternative to conventional explosive methods for demolition of concrete structures and rocks, the use of non-explosive demolition agents can be considered to reduce noise, vibration, and dust emissions during the demolition process. In this study, we conduct finite element analysis for crack initiation and propagation caused by the expansion of non-explosive demolition agents in square concrete structures. The predicted crack patterns are compared with the experimental results in the literature. The minimum values of the required expansion pressure of non-explosive demolition agents are also estimated, which depend upon the arrangement of non-explosive demolition agents and empty holes. Furthermore, we investigate the effect of empty holes on the fragmentation of concrete structures, and discuss the effective arrangement of non-explosive demolition agents and empty holes for fragmentation improvement.

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.

PURPOSES: This study is primarily focused on evaluating the effects of the non-linear stress-strain behavior of RAP concrete on structural response characteristics as is applicable to concrete pavement. METHODS : A 3D FE model was developed by incorporating the actual stress-strain behavior of RAP concrete obtained via flexural strength testing as a material property model to evaluate the effects of the non-linear stress-strain behavior to failure on the maximum stresses in the concrete slab and potential performance prediction results. In addition, a typical linear elastic model was employed to analyze the structural responses for comparison purposes. The analytical results from the FE model incorporating the actual stress-strain behavior of RAP concrete were compared to the corresponding results from the linear elastic FE model. RESULTS : The results indicate that the linear elastic model tends to yield higher predicted maximum stresses in the concrete as compared to those obtained via the actual stress-strain model. Consequently, these higher predicted stresses lead to a difference in potential performance of the concrete pavement containing RAP. CONCLUSIONS : Analysis of the concrete pavement containing RAP demonstrated that an appropriate analytical model using the actual stress-strain characteristics should be employed to calculate the structural responses of RAP concrete pavement instead of simply assuming the concrete to be a linear elastic material.