Recent changes in the construction method of piles to minimize noise, along with the development of high-strength reinforcement, have provided an economical high performance RC pile development to compensate for the disadvantages of existing PHC piles. In this study, a methodology for the development of cross - section details of high performance RC piles of various performances is presented by freely applying high strength steel and concrete. This study suggested a technique for calculating bending moments for a given axial force corresponding to the allowable crack widths and this can be used for serviceablity check. In calculating the design shear force, the existing design equation applicable to the rectangular or the I section was modified to be applicable to the hollow circular section. In particular, in the limit state design method, the shear force is calculated in proportion to the axial force, and the procedure for calculating PV diagram is established. Last, the section details are determined through PM diagrams that they have the similar flexural and axial-flexural performances of the PHC pile A, B and C types with a diameter of 500 mm. To facilitate the application of the selected standard sections to the practical tasks, the design PM diagram and design shear forces are proposed in accordance with the strength design method and limit state design method.

Diagonally reinforced concrete coupling beams (DRCBs) have been widely adopted in reinforced concrete (RC) bearing wall systems. DRCBs are known to act as a fuse element dissipating most of seismic energies imparted to the bearing wall systems during earthquakes. Despite such importance of DRCBs, the damage estimation of such components and the corresponding consequences within the knowledge of performance based seismic design framework is not well understood. In this paper, drift-based fragility functions are developed for in-plane loaded DRCBs. Fragility functions are developed to predict the damage and to decide the repair method required for DRCBs subjected to earthquake loading. Thirty-seven experimental results are collected from seventeen published literatures for this effort. Drift-based fragility functions are developed for four damage states of DRCBs subjected to cyclic and monotonic loading associated with minor cracking, severe cracking, onset of strength loss, and significant strength loss. Damage states are defined in a consistent manner. Cumulative distribution functions are fit to the empirical data and evaluated using standard statistical methods.

본 연구는 초고성능 콘크리트의 성능을 보다 향상시키기 위해 현재 콘크리트 보강에 사용하는 섬유들을 조합한 복합 섬유를 제작하여 복합섬유 혼입 초고성능 콘크리트의 강도 특성을 분석하였다. 복합섬유 4종과 단일섬유 3종을 각각 혼입하여 유동성과 압축, 휨강도 실험을 진행하였다. 복합섬유와 단일섬유 혼입 시험체 모두 유동성 평가를 만족하였으며, 단일섬유가 조금 더 우수한 성능을 나타내었다. 강도 평가결과 파라아라미드 섬유와 강섬유를 조합한 복합섬유 2종이 가장 우수한 결과를 나타내었으며, 복합섬유 직경 차이에 따라 압축 및 휨강도 보강효과가 다르게 나타난 것을 확인할 수 있었다. 압축강도 감소를 최소화하며 휨강도를 증가시킨 결과를 통해, 복합섬유는 단일섬유 간의 단점을 서로 보완할 수 있을 것으로 판단되며, 본 연구를 통해 차후 콘크리트의 다양한 재료적 특성을 보강하는 복합섬유도 충분히 제작 가능할 것으로 판단된다.

UHPFRC 15 M 분절형 박스거더에 대한 비선형 재료 및 비선형 기하학적 유한요소해석을 수행하였다. UHPFRC의 인장 및 압축 영역에서의 구성방정식은 공시체 시험을 기반으로 하였고, 체적 대비 강섬유 혼입률이 각각 1.0%, 1.5% 및 2.0%에 대해 해석을 수행하였다. UHPFRC를 위한 3차원 8 node hexahedron brick model과 1차원 embedded steel element를 기반으로 모델링하였다. UHPFRC 박스거더 단면에서 하부플랜지에 14개, 24개, 32개의 15.2mm 강연선을 모델링하여 실험결과와 비교하였다. 하중과 변위관계, 선형거동에서 비선형거동으로 변하는 시점에서 하중 및 중립축 변화 과정이 실험결과와 비교해 볼 때 정확하게 산출되었다. 따라서, 압축 및 인장구역에서 구성방정식을 반영한 재료적 비선형해석, UHPFRC 분절형 박스의 기하학적 비선형 해석이 유효함을 알 수 있다.

Now that problems with force-based seismic design have been clearly identified, design is inclined toward displacement-based methods. One such widely used method is Direct-Displacement-Based Design (DDBD). Yet, one of the shortcomings of DDBD is considering higher-mode amplification of story shear, moments, and displacements using equations obtained from limited parametric studies of regular planar frames. In this paper, a different approach to account for higher-mode effects is proposed. This approach determines the lateral secant stiffness of the building frames that fulfill the allowable inter-story drift without exceeding the desired story displacements. Using the stiffness, an elastic response spectrum analysis is carried out to determine elastic higher-mode force effects. These force effects are then combined with DDBD-obtained first-mode force effects using the appropriate modal superposition method so that design can be performed. The proposed design procedure is verified using Nonlinear Time History Analysis (NTHA) of twelve planar frames in four categories accounting for mass and stiffness irregularity along the height. In general, the NTHA response outputs compared well with the allowable limits of the performance objective. Thus, it fulfills the aim of minimizing the use of NTHA for planar frame buildings, thereby saving computational resources and effort.

Existing reinforced concrete building structures have seismic vulnerabilities under successive earthquakes (or mainshock-aftershock sequences) due to their inadequate column detailing, which leads to shear failure in the columns. To improve the shear capacity and ductility of the shear-critical columns, a fiber-reinforced polymer jacketing system has been widely used for seismic retrofit and repair. This study proposed a numerical modeling technique for damaged reinforced concrete columns repaired using the fiber-reinforced polymer jacketing system and validated the numerical responses with past experimental results. The column model well captured the experimental results in terms of lateral forces, stiffness, energy dissipation and failure modes. The proposed column modeling method enables to predict post-repair effects on structures initially damaged by mainshock.

Existing reinforced concrete building structures have seismic vulnerabilities due to their seismically-deficient details resulting in non-ductile behavior. The seismic vulnerabilities can be mitigated by retrofitting the buildings using a fiber-reinforced polymer column jacketing system, which can provide additional confining pressures to existing columns to improve their lateral resisting capacities. This study presents dynamic responses of a full-scale non-ductile reinforced concrete frame retrofitted using a fiber-reinforced polymer column jacketing system. A series of forced-vibration testing was performed to measure the dynamic responses (e.g. natural frequencies, story drifts and column/beam rotations). Additionally, the dynamic responses of the retrofitted frame were compared to those of the non-retrofitted frame to investigate effectiveness of the retrofit system. The experimental results demonstrate that the retrofit system installed on the first story columns contributed to reducing story drifts and column rotations. Additionally, the retrofit scheme helped mitigate damage concentration on the first story columns as compared to the non-retrofitted frame.

Following a 5.8 magnitude earthquake on September 12, 2016 in Gyeongju Province, a magnitude 5.4 earthquake occurred in the northern region of Pohang City on November 15, 2017 in South Korea. Only 7.9 % of the building structures are earthquake-resistant, according to the recent survey conducted by the government agencies in October 2017. In this paper, the linear analysis seismic performance evaluation procedure of the existing school structures presented in the revised methodology(Seismic Performance Evaluation Procedure and Rehabilitation Manual for School Facilities) was introduced. In this paper, the linear analysis evaluation procedure presented in the revised methodology was introduced and the seismic performance index of the example structure was evaluated using the linear analysis evaluation procedure. The seismic retrofit was verified by the linear and nonlinear dynamic analyses using Perform 3D. The analysis results show that the dissipated inelastic energy is concentrated on the retrofitted shear wall and the maximum inter-story drift of the stadium model structure with damping system satisfies the requirement of the current code.

The objective of this study was to evaluate the effectiveness of various crack inducers to be used in the advanced reinforced concrete pavement (ARCP) by conducting yard tests. Some of cracks are induced in ARCP to reduce the stresses in steel bars and to form more uniformly spaced cracks so that the required steel bar amount can be decreased and at the same time the pavement performance can be improved. In this study, an experimental ARCP was constructed for the length of 22.4 m, width of 1.12 m, and thickness of 0.26 m. The anchor lugs were placed at both ends of ARCP to pretend continuities of the system. 8 crack inducers with a uniform spacing of 2.8 m were installed in different manners when placing concrete, so the test length of the experimental ARCP was 19.6 m. The variables of crack inducers included the shape, material, installed depth, and installing method. The basic shape of the crack inducer represented a round face and a flat opposite face with a height of 50 mm and a width of 10 mm. The slightly different shaped crack inducers were installed for inducing cracks at both ends of ARCP. The crack inducers were primarily made of glass fiber reinforced plastic (GFRP) but a crack was induced using a polyethylene sheet inducer. The installed depths of the crack inducers were 30, 40 and 70 mm to the top of the crack inducer from the pavement surface. Most crack inducers were preinstalled on the transverse steel bar locations before concrete pouring, but 2 crack inducers were installed just after concrete placement when concrete was still fresh. The temperature measurement sensors of i-Buttons and thermocouples were installed at the top, middle and bottom of slab to measure the temperature variations of slab. The displacement transducers were also installed at the crack locations to measure the crack width movements. The experimental results showed that the cracks were induced at all the locations where the crack inducers were placed. In addition to the induced cracks, just one crack was formed naturally. The crack patterns on the surface of pavement were all comparable. The crack width measurement data showed that there were slight differences in the crack width movements among the cracks but all the cracks including both the induced and naturally formed cracks moved little within a 0.1 mm range. Therefore, any type of the crack inducers employed in this study can be used to initiate cracks in ARCP.

The contemporary high-tech structures have become enlarged and their functions more diversified. Steel concrete structure and composite material structures are not exceptions. Therefore, there have been on-going studies on fiber reinforcement materials to improve the characteristics of brittleness, bending and tension stress and others, the short-comings of existing concrete. In this study, the purpose is to develop the estimated model with dynamic characteristics following the steel fiber mixture rate and formation ration by using the nerve network in mixed steel fiber reinforced concrete (SFRC). This study took a look at the tendency of studies by collecting and analyzing the data of the advanced studies on SFRC, and facilitated it on the learning data required in the model development. In addition, by applying the diverse nerve network model and various algorithms to develop the optimal nerve network model appropriate to the dynamic characteristics. The accuracy of the developed nerve network model was compared with the experiment data value of other researchers not utilized as the learning data, the experiment data value undertaken in this study, and comparison made with the formulas proposed by the researchers. And, by analyzing the influence of learning data of nerve network model on the estimation result, the sensitivity of the forecasting system on the learning data of the nerve network is analyzed.

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.

Recently, redevelopment and reconstruction projects have caused problems such as depletion of natural aggregates, and the use of recycled aggregate is being reevaluated as an optimal alternative. Therefore, in this study, the mechanical and deformation characteristics of Environment-Friendly Recycled Coarse Aggregate (here after, EFRCA) concrete reinforced with para-aramid fiber with high strength and high elasticity are examined. The experimental main parameters were EFRCA replacement ratio (0, 30 and 50%) and para-aramid fiber volume fraction (0, 0.75 and 1.0%). Experimental results show that the EFRCA concrete has lower compressive strength than plain concrete. However, compared with the natural aggregate, the EFRCA concrete, which exhibited low material properties, showed almost the same performance as plain concrete, such as increased flexural strength and improved ductility by incorporating para-aramid fibers. Through the experiment, it is considered that the most suitable para-aramid volume fraction is 0.75%. Based on these results, the experimental results related to the performance degradation of EFRCA concrete containing para-aramid fibers are secured and basic data for determining the reuse possibility and reinforcement method of structures are presented.

It is a well known that concrete is strong for compression and weak for tension. For reinforcing the weakness and improving the performance about concrete, various methods are used. Fiber reinforced concrete that is one of them has been investigated in this study. The function of fiber in concrete is to improve the stress strain relation and toughness, crack control. It’s applied from normal strength concrete to ultra-high performance concrete. But it is essential to disperse fiber uniformly and to prevent aggregation of fiber in concrete, in order that fiber reinforced concrete show the sufficient performance. The various properties of fiber affect the essential properties, for instance, length and diameter of fiber, source, etc. So, this study evaluated the ultra-high performance concrete with mixed in composite fiber.

Diagonally reinforced concrete coupling beams (DRCB) play an important role in coupled shear wall systems since these elements dissipate most of seismic input energy under earthquake loading. For reliable seismic performance evaluation using nonlinear response history analysis, it is important to use an accurate analytical model for DRCBs. In this study, the Pinching4 model is used as a base model to simulate the cyclic behavior of DRCBs. For simulating the cyclic behavior of DRCBs using the Pinching4 model, the analytical parameters for backbone curve, pinching and cyclic deterioration in strength and stiffness should be computed. To determine the proper values of the constituent analytical parameters efficiently and accurately, this study proposes the empirical equations for the analytical parameters using regression analyses. It is shown that the hysteretic behavior of coupling beams can be simulated efficiently and accurately using the proposed numerical model with the proposed empirical equations of model parameters.