Non-seismic-designed reinforced concrete (RC) pier walls often include lap splices in potential plastic hinge regions. This study develops an analytical model to capture the post-yield load–deformation response of lap-spliced RC pier walls subjected to earthquake loading. The parameters of the model were calibrated using experimental results, and linear regression was conducted to propose predictive equations for these parameters. The accuracy of the model was validated by comparing it to the load–deformation responses of specimens not included in the calibration database. Subsequently, the developed model was applied to probabilistic bridge models supported by RC pier walls. A multi-parameter seismic demand model was constructed, taking into account geometric, material, and structural uncertainties, using Lasso regression. This model achieved R² values of 0.73 for in-plane loading and 0.75 for out-of-plane loading. The improvements in performance metrics and the results of the sensitivity analysis emphasize the need to develop a multi-parameter seismic demand model to ensure more reliable seismic demand predictions.

Current seismic design provisions prohibit the use of a weak panel zone from using special moment frame (SMF) connections due to concerns that large deformations in these zones may lead to brittle connection failures. However, several experimental studies have demonstrated that moment connections with weak panel zones can exhibit adequate ductility and energy dissipation capacity for SMF connections. This study aims to investigate the impact of weak panel zones on the seismic performance of SMFs utilizing welded unreinforced flange-welded web (WUF-W) connections, as outlined in AISC 358-22. The analysis will consider both four-story and twelve-story SMFs. Each frame will be modeled with either strong or weak panel zones. The findings indicate that SMFs with weak panel zones demonstrate greater ductility and collapse strength compared to their counterparts with strong panel zones.

본 연구는 수소 저장 용기의 지진 취약도 분석 시 요구되는 막대한 계산 자원 문제를 해결하고자, 기하학적 대칭성을 활용한 1/4 대칭 유한요소 모델(Quarter Model)을 개발하고 그 타당성을 검증하였다. 표준화된 AC 156 인공지진을 이용한 비선형 시간 이력 해석을 통해 Full Model과 응답을 비교한 결과, Quarter Model의 해석 시간을 Full Model의 20%를 가지고 해석을 완료하였으 며, 이에 따른 신뢰성 확보를 위해 최상단 변위를 통해 이를 검증하였을 때 0.13%의 미미한 오차를 보이며 변위 시간 이력 양상 역시 동일한 거동을 보이며 효율성 확보라는 연구 목표를 달성했다. 또한, 고유진동수, 강재와 콘크리트 주요부의 최대 응력에서 모두 높은 수준의 일치도를 보여 정량적 신뢰도를 입증하였다. 이를 통해 제안된 모델은 해석 정확도를 유지하면서 계산 비용을 획기적으로 절감 하는 효율적인 방법론임을 확인하였다. 다만 이는 균질 등방성 재료인 강재에 한정된 대칭 모델이며, 그 외의 재료 사용 시 추가적인 연구를 통한 모델 구축이 필요할 것으로 판단된다.

This study investigates the seismic performance of beam-column connections using Thin-Walled Steel Composite (TSC) beams and Prestressed Reinforced Concrete (PSRC) columns. TSC beams are constructed from U-shaped thin steel plates that are filled with concrete, allowing for composite action with slabs through the use of shear connectors. They are widely applied in industrial buildings due to excellent strength, stiffness, and constructability. However, slender web plates are prone to local buckling, which may compromise their performance during seismic events. To mitigate this issue, internal supports have been introduced to enhance web stability and concrete confinement. Cyclic loading tests on three specimens—with and without internal supports—demonstrated that the supports increased moment capacity, improved energy dissipation, and effectively reduced buckling. Even slender sections demonstrated performance comparable to that of compact sections. All specimens reached peak strength at a 2.44% rotation angle, with damage localized near the supports. A practical connection detail was also proposed, taking into account constructability and structural reliability. The results provide valuable guidance for the seismic design of composite systems in large-scale structures.

원자력발전소에 설치되는 안전관련 기기는 높은 수준의 내진성능을 확보하여야 한다. 본 연구에서는 대표적인 안전관련 기기 인 전기 캐비닛을 대상으로, 열반(multi-bay) 구성 및 콘크리트 기초 열화와 같은 실제 설치 조건을 고려하여 내진성능을 평가하였다. 실제 현장에서는 전기 캐비닛이 열반 형태로 설치되는 경우가 많으며, 지지부 열화의 대표적 형태로 앵커 위치에서의 콘크리트 균열이 자주 발견된다. 이러한 조건을 반영하기 위하여, 앵커 위치에 균열 폭 0.5 mm 및 1.0 mm를 모사한 균열 기초와 건전한 기초를 대상 으로 실험체를 제작하였다. 실험체는 단순화한 전기 캐비닛 모델로서 단독(single-bay) 및 2기 열반(two-bay) 구성을 적용하였으며, 선설치 앵커로 고정 후 진동대를 이용한 한계상태 내진성능 실험을 수행하였다. 실험 결과, 균열이 없는 조건에서는 2기 열반 구성이 단독 구성보다 높은 내진성능을 보였다. 그러나 균열 조건에서는 2기 열반 구성에서 내진성능이 저하되는 경향이 나타난 반면, 단독 구성은 유의미한 성능 저하가 관찰되지 않았다.

In this study, in order to identify the vibration characteristics of the process control cabinet, as a basic study for evaluating the seismic performance of nuclear power plant structures, a cabinet vibration test equipment, sliding base, and measurement system were constructed. The reliability of the base was verified by utilizing ODS and phase data to determine how the cabinet deforms under seismic conditions. In addition, the cabinet was subjected to excitation frequencies from 8 Hz to 15 Hz in order to examine the changes in the natural frequency of the cabinet according to the two types of sliding base motion and the cabinet door open/close status. The vibration characteristics of the empty cabinet were investigated experimentally to examine the cabinet excitation characteristics and changes in natural frequency. Since the structural rigidity of the cabinet changes depending on the excitation conditions and door opening/closing, the natural frequency and response size of the cabinet change. Since the door opening is a condition that greatly amplifies the cabinet vibration response, it causes structural defects and greatly affects the changes in natural frequency.

최근 지구온난화로 인한 피해가 심각해짐에 따라 화석연료 사용을 줄이고자 친환경 수소 에너지의 활용이 증가하고 있다. 이에 따라 수소의 저장 및 운송을 위한 수소 저장 용기의 수요가 확대되고 있으나, 현재 널리 사용되고 있는 강재 기반 저장 용기는 부식과 같은 내구성 저하 현상에 취약하다. 따라서 선행 연구는 지지부 부식에 따른 내진 성능 저하 문제를 해결하기 위해 부식 저항성 이 뛰어난 CFRP를 지지부 기둥을 적용하여 설계 하중에서 적용성을 검토하였다. 이때 본 연구는 CFRP의 강도-중량비가 높음을 고려 하여 기존 강재 구조물 지지부 ㄱ 단면 대비 높은 강성을 가진 H 단면과 ㅁ 단면을 지지부 기둥에 적용하여 연구를 수행하였다. 이때 실제와 가까운 해석 결과를 도출하기 위해 고유진동수 추출해석을 진행하여 감쇠 계수를 적용 시켰고, AC 156 인공 지진을 설계 하중 으로 적용한 결과, ㅁ 단면을 적용한 강재 기둥의 접합부 응력은 222.34 MPa로 기존 ㄱ 형강 대비 78.93%로 설계 하중에 만족함을 보였다. ㅁ 단면 적용 CFRP 기둥은 파손 지수(DI)를 통해 평가하였고, 이때 최대 DI는 수지 인장에서 발생하였으며, 그 값은 0.708로 파괴 기준 대비 29.2% 낮아 설계 하중에 만족함을 보였다. 또한, 기초 슬래브에서 쪼갬 인장 응력과 휨 인장 응력을 통한 평가를 진행 하였고, 현장 실험 결과와 마찬가지로 설계 하중에 휨 인장 파괴가 발생하는 것으로 확인하였다. 하지만 파단 시점은 CFRP에서 1.54배 오래 설계 하중에 견디는 것을 확인하여, 그 적용성을 확인하였다. 결론적으로 지진의 발생 빈도가 높아짐에 따라 수소 저장 용기의 안전성 확보가 시급하다. 따라서 기존 강재 대상 구조물의 부식으로 인한 강성 저하 문제를 해결하기 위해, 높은 내구성 및 부식 저항성 재료의 적용은 필수적이다. 동시에 기초 슬래브의 안전성 확보에 대한 연구가 추가적으로 수행되어야 한다.

Existing reinforced concrete buildings with seismically deficient columns experience reduced structural capacity and lateral resistance due to increased axial loads from green remodeling or vertical extensions aimed at reducing CO2 emissions. Traditional performance assessment methods face limitations due to their complexity. This study aims to develop a machine learning-based model for rapidly assessing seismic performance in reinforced concrete buildings using simplified structural details and seismic data. For this purpose, simple structural details, gravity loads, failure modes, and construction years were utilized as input variables for a specific reinforced concrete moment frame building. These inputs were applied to a computational model, and through nonlinear time history analysis under seismic load data with a 2% probability of exceedance in 50 years, the seismic performance evaluation results based on dynamic responses were used as output data. Using the input-output dataset constructed through this process, performance measurements for classifiers developed using various machine learning methodologies were compared, and the best-fit model (Ensemble) was proposed to predict seismic performance.

Reinforced concrete (RC) piloti buildings are vulnerable in the event of earthquake because the stiffness in the 1st story columns is weak to compare with the members in upper stories. In this study, seismic performances of RC piloti structures were evaluated considering with different types of floor plane layouts according to core eccentricity. With four types of floor plane layouts, five stories plioti structures were evaluated by two approaches, a nonlinear pushover analysis and a nonlinear time-history analysis. In order to improve seismic performances by satisfying the collapse prevention (CP) level, two ductile reinforcing methods by carbon fiber sheets and steel jackets were applied. Due to eccentricities in stiffness and mass with directions of plane and vertical stories, piloti structures were greatly influenced by higher order modes, so the seismic performances by the time-history analysis were significantly different from by the static pushover analysis.

This paper aims to quantify the retrofit effect of the Bolt Prefabricated Concrete-Filled Tube reinforcement method on non-seismic school reinforced concrete building through static cyclic loading experiments. To achieve the objective, two-story specimens including a non-retrofitted frame(NRF) and a Bolt Prefabricated Concrete-Filled Tube Reinforcement Frame(BCRF) were tested under static cyclic loading, and the lateral resistant capacities were compared in terms of maximum strength, initial stiffness, effective stiffness, and total energy dissipation. In addition, the load-displacement curves were compared to the story drift limit specified in Seismic Performance Evaluation and Retrofit Manual for School Facilities to investigate if the retrofitted frame was satisfied in target performance(life safety). Experimental results showed that BCRF successfully met the target performance, with a 200% increase in maximum strength and a 300% increase in energy dissipation capacity. Additionally, both initial stiffness and effective stiffness improved by more than 30% compared to NRF. Furthermore, BCRF exhibited an effect that delayed the occurrence of bond failure.

과거 지진 발생 시 구조요소에 비해 비구조요소에서 더 많은 피해가 발생하였다. 비구조요소의 손상은 건물 및 시설의 기능에 영향을 줄 뿐만 아니라 인명피해를 유발할 수 있다. 건축물 내진설계 기준에서는 피난경로상의 비구조요소는 내진설계 또는 검토가 필요하다. 국내에서는 경주지진 이후 피난경로에 위치할 수 있는 천장 시스템의 내진성능 검증이 활발히 진행되고 있다. 그러나 옥외 계단, 문 등에 설치되는 캐노피 시스템의 내진설계 및 검증은 미흡한 실정이다. 지진으로 인해 캐노피가 위치유지를 하지 못하여 탈락 하거나 손상될 경우, 피난경로가 차단되어 인명피해로 이어질 수 있으므로 내진설계 및 내진성능을 평가할 필요가 있다. 따라서 본 연구에서는 모듈형 캐노피 시스템을 개발하고, 주요 요소에 대한 구조실험을 수행하였으며, 기존의 캐노피 시스템과 그 성능을 비교분 석 하였다.

The seismic performance of lead-rubber bearings (LRBs) is significantly affected by both the axial force and loading rate they experience. Accurate assessment of LRBs’ seismic performance, therefore, requires realistic simulation of these forces and rates, as well as of the response of the isolated structure during seismic events. This study conducted a series of real-time hybrid simulations (RTHS) to evaluate the seismic behavior of LRBs in such conditions. The simulations focused on a two-span continuous bridge isolated by LRBs atop the central pier, exposed to horizontal and vertical ground motions. In the RTHS framework, the LRBs were physically tested in the laboratory, while the remainder of the bridge was numerically modeled. Findings from these simulations indicated that the vertical ground motion had a minimal effect on the lateral response of the bridge when isolated by LRBs.

Structures compromised by a seismic event may be susceptible to aftershocks or subsequent occurrences within a particular duration. Considering that the shape ratios of sections, such as column shape ratio (CSR) and wall shape ratio (WSR), significantly influence the behavior of reinforced concrete (RC) piloti structures, it is essential to determine the best appropriate methodology for these structures. The seismic evaluation of piloti structures was conducted to measure seismic performance based on section shape ratios and inter-story drift ratio (IDR) standards. The diverse machine-learning models were trained and evaluated using the dataset, and the optimal model was chosen based on the performance of each model. The optimal model was employed to predict seismic performance by adjusting section shape ratios and output parameters, and a recommended approach for section shape ratios was presented. The optimal section shape ratios for the CSR range from 1.0 to 1.5, while the WSR spans from 1.5 to 3.33, regardless of the inter-story drift ratios.

In densely populated urban areas, reinforced concrete residential buildings with an open first floor and closed upper floors are preferred to meet user demands, resulting in significant vertical stiffness irregularities. These vertical stiffness irregularities promote the development of a soft-story mechanism, leading to concentrated damage on the first floor during seismic events. To mitigate seismic damage caused by the soft-story mechanism, stiffness-based retrofit strategies are favored, and it is crucial to determine an economically optimal level of retrofitting. This study aims to establish optimal seismic retrofit strategies by evaluating the seismic losses of buildings before and after stiffness-based retrofitting. An equivalent single-degree-of-freedom model is established to describe the seismic response of a multi-degree-of-freedom model, allowing for seismic demand analysis. By convolving the seismic loss function with the hazard curve, the annual expected loss (EAL) of the building is calculated to assess the economic losses. The results show that stiffness-based retrofitting increases first-story lateral stiffness by 20-40%, enhancing structural seismic performance, but also results in a rise in EAL compared to the as-built state, indicating lower cost-effectiveness from an economic perspective. The research concludes that retrofit options that increase first-story lateral stiffness by at least 60% are more appropriate for reducing financial losses.

Reinforced concrete (RC) moment frames are widely used to resist lateral loads associated with wind and earthquakes. However, most older RC moment frames performed poorly against past earthquakes. In moment frames, beam-column connections play a crucial role in system performance. Among the connections, corner connections are more vulnerable because they are restrained by only two beams and are affected most strongly by bidirectional loading. High-performance fiber-reinforced cementitious composites (HPFRCC) were used in previous studies to improve the seismic performance of older beam-column connections. This study aims to evaluate the level of improvement of seismic behavior of older beam-column connections under bidirectional loading after retrofitted with HPFRCC by comparing the seismic behavior of the HPFRCC connections to beam-column connections used in intermediate (IMF) and special moment frames (SMF). Test results revealed that the seismic behavior of the HPFRCC connections was almost close to that of SMF connections.

저층 건축물의 횡-비틀림 거동은 고차모드 효과를 증폭시킬 수 있으며, 내진성능평가 시 관련 기준은 고차모드 지배 구조물에 대해 비선형정적해석과 함께 선형동적해석을 추가로 수행하도록 규정하고 있다. 선형동적절차에는 상당한 안전계수가 적용되므로, 이는 과도한 내진보강설계로 이어질 수 있다. 이를 방지하기 위해 엔지니어들은 내진보강 시 고차모드 효과를 줄이기 위해 시행착오법을 사용해 왔다. 그러나 시행착오법에는 많은 시간과 노력이 소요되며, 결정된 보강안이 최적인지 확인하기 어렵다. 본 연구는 저층 건 축물의 수학적 모델을 수립하고 응답스펙트럼해석을 통해 고차모드 효과에 비틀림이 독립적으로 미치는 영향을 파악하였다. 이를 바탕으로 효율적인 내진보강 설계를 위해 활용될 수 있는 도표와 절차를 제시하였다. 제시된 절차를 통해 최소한의 내진보강으로 횡- 비틀림 거동하는 저층 건축물의 고차모드 효과를 효율적으로 감소시킬 수 있음을 확인하였다.

Performance-Based Seismic Design (PBSD) is an approach that evaluates how structures will perform under different levels of seismic activity. It focuses on ensuring that buildings not only withstand earthquakes but also meet specific performance objectives, such as minimizing damage or maintaining functionality after the event. Unlike traditional methods, PBSD allows for more tailored, cost-effective designs by considering varying degrees of acceptable damage based on the structure's importance and use. PBSD was introduced in Korea in 2016 to replace elastic design, which is inevitable to over-design to cope with all variables such as earthquakes and winds. When PBSD is applied to the structural design new building, One of the challenges of PBSD is the complexity involved in creating accurate inelastic analysis models. The process requires significant time and effort to analyze the results, as it involves detailed simulations of how structures will behave under seismic stress. Additionally, organizing and interpreting the analysis data to meet performance objectives can be labor-intensive and technically demanding. In order to solve this problem, a post-processor program was developed in this study. A post-processor was developed based on Excel program using Visual Basic for Applications(VBA). Because analysis outputs of Perform-3D, that is a commercial software for structural analysis and design, are very complicated, generation of tables and graphs for report is significant time and effort consuming task. When the developed post-processor is used to make the seismic design report, the required task time is significantly reduced.

The purpose of this study is to experimentally analyze the seismic performance of a vertical irregular beam-column specimen reinforced with RBS (Replaceable Steel Brace System), a steel brace system. To evaluate the seismic performance of RBS, three specimens were manufactured and subjected to cycle loading tests. The stiffness ratio of beam-upper column of the non-retrofitted specimen was 1.2, and those of the two retrofitted specimens were 1.2 and 0.84. The stiffness ratio of the beam-lower column of all specimens was 0.36. And the stiffness ratio were used for variable. As a result of the experiment, the specimen retrofitted with RBS showed improved maximum load, effective stiffness and energy dissipation capacity compared to the non-retrofitted specimen with the same beam-upper column stiffness ratio. The specimen with 0.84 beam-upper column stiffness ratio showed improved performance compared to the specimen with 1.2 stiffness ratio.

This study proposes an economically affordable method for retrofitting non-seismic detailed roof reinforced concrete beam-column joints (BCJs). The proposed method presents an innovative arrangement of steel plates designed to delay the propagation of joint shear cracks by externally applying compressive stress to the area surrounding the BCJs. Two full-scale sub-assemblage specimens for each exterior and interior roof BCJ, i.e., control and retrofitted specimens, were subjected to reversed cyclic loading to evaluate the proposed method. The retrofitted specimens displayed a preferable ductile behavior to the corresponding control specimen, with an enhancement in lateral strength by at least 100%. Furthermore, retrofitted specimens dissipated up to 13 times more energy than the control specimen by initiating a plastic hinge on beams or columns. These results indicated the effectiveness of the proposed method in preventing joint shear failure and improving the seismic behavior of roof BCJs.