가력유형별 군중하중의 크기에 관한 실험적 연구

김진식 ( Kim Jin-sik ),신윤호 ( Shin Yun-ho ),최수경 ( Choi Soo-kyung ) 한국건축시공학회 2016 한국건축시공학회 학술발표대회 논문집 Vol.16 No.2

This study is to categorize the loading of multiple persons on a vertical building elements into three types to test the size of crowd pressure under each loading patterns. The loading patterns is divided under the combination of loading method and loading persons. The loading method is categorized into the method of instantaneous loading of hand on a force plate and the method of continuous loading. The loading persons has been composed of 1~5 persons under the loading patterns. The loading patterns is also divided into lateral loading, longitudinal loading, and agglomeration loading. The subject group has been composed of 12 males in 20s. The load measurement device(size 1800×600×36mm, capacity 20kN, rigidity 28kN/cm) has been designed and manufactured directly. To eliminate the difference of individual, the size of crowd pressure has been converted into the strength to weight ratio (maximum load/weight) for computation. The strength to weight ratio in lateral loading was about 0.91 under instantaneous loading and about 0.47 under continuous loading. The strength to weight ratio in longitudinal loading was about 0.65 under instantaneous loading and about 0.36 under continuous loading. The strength to weight ratio in agglomeration loading was about 0.65 under instantaneous loading and about 0.36 under continuous loading.

진동타입말뚝의 해석기법 개발 및 평가

이승현,장인성,Lee. Seung Hyun,Jang. In Sung 한국방재학회 2013 한국방재학회논문집 Vol.13 No.6

진동타입기에 의해 시공되는 말뚝의 해석을 위한 해석기법을 개발하고 해석기법의 신뢰성을 평가해보기 위해 시스템변수를 달리하여 해석을 수행하였다. 말뚝의 동적 주면마찰 하중전이곡선을 결정짓는 부주면마찰력의 크기는 정적 연직하중이 작용하지 않는 경우에 대한 해석을 통해 시행착오적으로 구할 수 있을 것으로 생각된다. 진동타입기에 의해 시공되는 말뚝의 연직변위량은 정적 연직하중의 크기에 비례하는 결과를 보였다. 진동타입시 말뚝의 가속도는 부주면 마찰력 및 정적 연직하중과는 무관하며 기진력의 크기에 의존함을 알 수 있었다. 정적 연직하중의 증가에 따른 말뚝주면 하중전이곡선의 변화양상을 비교해 볼 때 진폭은 거의 일정하나 곡선이 전체적으로 상향으로 이동함을 알 수 있었다. 말뚝선단 하중전이곡선에 대하여 최대 하중값은 부주면 마찰력 및 정적 연직하중의 크기와 무관하게 일정함을 알 수 있었다. Technique for analyzing a pile installed by vibratory pile driver was developed and analyses were performed with varying system variables in order to evaluate reliability of the developed technique. Negative skin friction which defines dynamic skin load transfer curve seems to be obtained by trial and error method for the situation without static vertical load. Vertical displacment of the pile was proportional to the static vertical load. It can be seen acceleration of the pile was dependent on excitation force regardless of the negative skin friction and the static vertical load. Comparing the shapes of skin load transfer curves with static vertical load, amplitudes of the curves were nearly the same but it can be seen that the curves shift to upward. Maximum values of the toe load transfer curves were constant regardless of the negative skin friction and the static vertical load.

Seismic performance of Bujian Puzuo considering scale ratio and vertical load effects

Yong-Hui Jiang,Jun-Xiao He,Lei Zhu,Lin-Lin Xie,Shuo Fang 국제구조공학회 2024 Structural Engineering and Mechanics, An Int'l Jou Vol.90 No.5

This study investigated the influence of scale ratio and vertical load on the seismic performance of Puzuo joints in traditional Chinese timber structures. Three low-cyclic reversed loading tests were conducted on three scaled specimens of Bujian Puzuo in Yingxian Wooden Pagoda. This study focused on the deformation patterns and analyzed seismic performance under varying scale ratios and vertical loads. The results indicated that the slip and rotational deformations of Bujian Puzuo were the primary deformations. The scale of the specimen did not affect the layer where the maximum interlayer slip occurred, but it did decrease the proportion of slip deformation. Conversely, the reducing vertical load caused the layer with the maximum slippage and the position of the damaged Dou components to shift upward, and the proportion of slip deformation increased. When the vertical load was decreased by 3.7 times, the maximum horizontal bearing capacity under positive and negative loadings, initial stiffness, and energy dissipation of the specimen decreased by approximately 60%, 58.79%, 69.62%, and 57.93%, respectively. The horizontal bearing capacity under positive loading and energy dissipation of the specimen increased by 35.63% and 131.54%, when the specimen scale was doubled and the vertical load was increased by 15 times.

Effect of Functional Ankle Instability and Surgical Treatment on Dynamic Postural Stability and Leg Stiffness Variables during Vertical-Drop Landing

( Kyoung Kyu Jeon ),( Kew Wan Kim ),( Che Cheong Ryew ),( Seung Hyun Hyun ) 한국운동역학회 2018 한국운동역학회지 Vol.28 No.2

Objective: The purpose of this study was to investigate the effect of functional ankle instability (FAI) and surgical treatment (ST) on postural stability and leg stiffness during vertical-drop landing. Method: A total of 21 men participated in this study (normal [NOR]: 7, FAI: 7, ST: 7). We estimated dimensionless leg stiffness as the ratio of the peak vertical ground reaction force and the change in stancephase leg length. Leg length was calculated as the distance from the center of the pelvis to the center of pressure under the foot. Furthermore, the analyzed variables included the loading rate and the dynamic postural stability index (DPSI; medial-lateral [ML], anterior-posterior [AP], and vertical [V]) in the initial contact phase. Results: The dimensionless leg stiffness in the FAI group was higher than that of the NOR group and the ST group (p = .018). This result may be due to a smaller change in stance-phase leg length (p = .001). DPSI (ML, AP, and V) and loading rate did not show differences according to the types of ankle instability during drop landing (p > .05). Conclusion: This study suggested that the dimensionless leg stiffness was within the normal range in the ST group, whereas it was increased by the stiffness of the legs rather than the peak vertical force during vertical-drop landing in the FAI group. Identifying these potential differences may enable clinicians to assess ankle instability and design rehabilitation protocols specific for the impairment.

Effect of Functional Ankle Instability and Surgical Treatment on Dynamic Postural Stability and Leg Stiffness Variables during Vertical-Drop Landing

전경규,김규완,현승현,류재청 한국운동역학회 2018 한국운동역학회지 Vol.28 No.2

Objective: The purpose of this study was to investigate the effect of functional ankle instability (FAI) and surgical treatment (ST) on postural stability and leg stiffness during vertical-drop landing. Method: A total of 21 men participated in this study (normal [NOR]: 7, FAI: 7, ST: 7). We estimated dimensionless leg stiffness as the ratio of the peak vertical ground reaction force and the change in stance-phase leg length. Leg length was calculated as the distance from the center of the pelvis to the center of pressure under the foot. Furthermore, the analyzed variables included the loading rate and the dynamic postural stability index (DPSI; medial-lateral [ML], anterior-posterior [AP], and vertical [V]) in the initial contact phase. Results: The dimensionless leg stiffness in the FAI group was higher than that of the NOR group and the ST group (p = .018). This result may be due to a smaller change in stance-phase leg length (p = .001). DPSI (ML, AP, and V) and loading rate did not show differences according to the types of ankle instability during drop landing (p > .05). Conclusion: This study suggested that the dimensionless leg stiffness was within the normal range in the ST group, whereas it was increased by the stiffness of the legs rather than the peak vertical force during vertical-drop landing in the FAI group. Identifying these potential differences may enable clinicians to assess ankle instability and design rehabilitation protocols specific for the impairment.

Vertical Cyclic Performance of Precast Frame with Hook-end U-shaped High-damping Rubber Joint

Kai-Siong Woon,Farzad Hejazi 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.5

High-damping rubber (HDR) has been commonly used to dissipate cyclic energy and reduce the bumping effect of a building structure. Studies on the application of HDR in precast reinforced concrete structures have mainly focused on the effects caused by lateral cyclic loads, but joints in precast structures are also highly susceptible to damage when frames are subjected to vertical cyclic loads. Therefore, this research aimed to develop a new hook-end U-shaped joint by using HDR so that the formation of cracks on precast frames could be minimized and the accumulated energy dissipation capacities could be enhanced under the actions of a vertical cyclic load. The developed joint was experimentally tested and compared with a single dowel beam-column-connected precast frame. Results revealed that the performance of the joint was similar to that of hysteresis loops and yield force. But, its maximum force and strength ratio were slightly lower than that of the control precast frame. A nonlinear 3D numerical model was also created and subjected to a vertical cyclic load to predict the behavior of the precast frame with the proposed and single dowel beam-column connections. Differences between numerical and experimental results were identified by comparing numerical data with experimental data.

Effect of Functional Ankle Instability and Surgical Treatment on Dynamic Postural Stability and Leg Stiffness Variables during Vertical-Drop Landing

Jeon, Kyoung Kyu,Kim, Kew Wan,Ryew, Che Cheong,Hyun, Seung Hyun Korean Society of Sport Biomechanics 2018 한국운동역학회지 Vol.28 No.2

Objective: The purpose of this study was to investigate the effect of functional ankle instability (FAI) and surgical treatment (ST) on postural stability and leg stiffness during vertical-drop landing. Method: A total of 21 men participated in this study (normal [NOR]: 7, FAI: 7, ST: 7). We estimated dimensionless leg stiffness as the ratio of the peak vertical ground reaction force and the change in stance-phase leg length. Leg length was calculated as the distance from the center of the pelvis to the center of pressure under the foot. Furthermore, the analyzed variables included the loading rate and the dynamic postural stability index (DPSI; medial-lateral [ML], anterior-posterior [AP], and vertical [V]) in the initial contact phase. Results: The dimensionless leg stiffness in the FAI group was higher than that of the NOR group and the ST group (p = .018). This result may be due to a smaller change in stance-phase leg length (p = .001). DPSI (ML, AP, and V) and loading rate did not show differences according to the types of ankle instability during drop landing (p > .05). Conclusion: This study suggested that the dimensionless leg stiffness was within the normal range in the ST group, whereas it was increased by the stiffness of the legs rather than the peak vertical force during vertical-drop landing in the FAI group. Identifying these potential differences may enable clinicians to assess ankle instability and design rehabilitation protocols specific for the impairment.

Experimental analysis of thermal gradient in concrete box girder bridges and effects of polyurethane insulation in thermal loads reduction

Farzad Raeesi,Sajad Heydari,Hedayat Veladi 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.83 No.5

Environmental thermal loads such as vertical and lateral temperature gradients are significant factors that must be taken into account when designing the bridge. Different models have been developed and used by countries for simulating thermal gradients in bridge codes. In most of the codes only vertical temperature gradients are considered, such as Iranian Standard Loads for Bridge code (ISLB), which only considers the vertical gradient for bridge design proposes. On the other hand, the vertical gradient profile specified in ISLB, has many lacks due to the diversity of climate in Iran, and only one vertical gradient profile is defined for whole Iran. This paper aims to get the both vertical and lateral gradient loads for the concrete box girder using experimental analysis in the capital of Iran, Tehran. To fulfill this aim, thermocouples are installed in experimental concrete segment and temperatures in different location of the segment are recorded. A three dimensional finite element model of concrete box-girder bridge is constructed to study the effects of thermal loads. Results of investigation proved that the effects of thermal loads are not negligible, and must be considered in design processes. Moreover, a solution for reducing the negative effects of thermal gradients in bridges is proposed. Results of the simulation show that using one layer polyurethane insulation can significantly reduce the thermal gradients and thermal stresses.

Study on mechanical behaviors of column foot joint in traditional timber structure

Wang, Juan,He, Jun-Xiao,Yang, Qing-Shan,Yang, Na Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.66 No.1

Column is usually floating on the stone base directly with or without positioning tenon in traditional Chinese timber structure. Vertical load originated by the heavy upper structure would induce large friction force and compression force between interfaces of column foot and stone base. This study focused on the mechanical behaviors of column foot joint with consideration of the influence of vertical load. Mechanism of column rocking and stress state of column foot has been explored by theoretical analysis. A nonlinear finite element model of column foot joint has been built and verified using the full-scale test. The verified model is then used to investigate the mechanical behaviors of the joint subjected to cyclic loading with different static vertical loads. Column rocking mechanism and stress distributions of column foot were studied in detail, showing good agreement with the theoretical analysis. Mechanical behaviors of column foot joint and the effects of the vertical load on the seismic behavior of column foot were studied. Result showed that compression stress, restoring moment and stiffness increased with the increase of vertical load. An appropriate vertical load originated by the heavy upper structure would produce certain restoring moment and reset the rocking columns, ensuring the stability of the whole frame.

Study on mechanical behaviors of column foot joint in traditional timber structure

Juan Wang,Jun-Xiao He,Qingshan Yang,Na Yang 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.66 No.1

Column is usually floating on the stone base directly with or without positioning tenon in traditional Chinese timber structure. Vertical load originated by the heavy upper structure would induce large friction force and compression force between interfaces of column foot and stone base. This study focused on the mechanical behaviors of column foot joint with consideration of the influence of vertical load. Mechanism of column rocking and stress state of column foot has been explored by theoretical analysis. A nonlinear finite element model of column foot joint has been built and verified using the full-scale test. The verified model is then used to investigate the mechanical behaviors of the joint subjected to cyclic loading with different static vertical loads. Column rocking mechanism and stress distributions of column foot were studied in detail, showing good agreement with the theoretical analysis. Mechanical behaviors of column foot joint and the effects of the vertical load on the seismic behavior of column foot were studied. Result showed that compression stress, restoring moment and stiffness increased with the increase of vertical load. An appropriate vertical load originated by the heavy upper structure would produce certain restoring moment and reset the rocking columns, ensuring the stability of the whole frame.