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.

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.

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.

변동풍력의 연직분포를 고려한 건축물의 풍하중 평가

류혜진(Ryu, Hye-Jin),신동현(Shin, Dong-Hyeon),하영철(Ha, Young-Cheol) 대한건축학회 2019 大韓建築學會論文集 : 構造系 Vol.35 No.7

The wind tunnel test makes it possible to predict the wind loads for the wind resistant design. There are many methods to evaluate wind loads from data obtained from the wind tunnel test and these methods have advantages and disadvantages. In this study, two of these methods were analyzed and compared. One is the wind load evaluation method by fluctuating displacement and the other is the wind load evaluation method considering vertical profile of fluctuating wind force. The former method is evaluated as the sum of the mean wind load of the average wind force and the maximum value of the fluctuating wind load. The latter method is evaluated as the sum of the mean wind load and maximum value of the background wind load, and the maximum value of the resonant wind load. Two methods were applied to the wind tunnel test to compare the evaluated wind loads according to the two methods, with a maximum difference of about 1.2 times. The wind load evaluated by the method considering vertical profile of the fluctuating wind force (VPFWF) was larger than the wind load evaluated by the method by fluctuating displacement (FD). Especially, the difference of the wind load according to the two methods is large in the lower part of the building and the wind load is reversed at a specific height of the building. VPFWF of evaluating resonant wind loads and background wind loads separately is more reasonable.

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.

기존말뚝과 보강말뚝의 하중분담 특성에 관한 실험적 연구

조성훈(Seonghun Cho),최기선(Kisun Choi),조삼덕(Samdeok Cho),유영찬(Youngchan You),최창호(Changho Choi) 한국지반환경공학회 2014 한국지반환경공학회논문집 Vol.15 No.12

최근 공동주택 수직증축 리모델링 사업 등 기초구조물을 보강하기 위한 기술적 수요가 증가하고 있다. 본 논문에서는 기존 구조물을 지지하는 기존말뚝에 보강말뚝을 추가로 설치할 경우 추가하중에 의한 기존말뚝과 보강말뚝의 하중분담 특성을 연구하였다. 정사각형의 기초판에 설치된 기존말뚝 4본에 허용하중을 재하한 후, 기초판 중앙에 보강말뚝 1본을 추가로 설치하고 추가하중을 재하하였다. 실험결과로부터 기존말뚝에 재하되는 하중이 허용지지력을 초과한 이후에 기존말뚝과 보강말뚝이 하중을 균등하게 분담하는 것으로 분석되었다. 기존말뚝에 허용하중 재하 후, 허용하중 대비 60 %, 80 %, 100 %까지 제하(unloading)하고, 보강말뚝을 설치한 후 추가하중을 재재하(reloading)하는 실험을 수행하였다. 연구 결과 제하 하중의 양이 증가함에 따라 재재하 시 기존말뚝과 보강말뚝이 하중을 균등하게 분담하는 재재하 하중이 감소하는 경향을 파악하였다. Recently, there are increasing technical needs for foundation retrofit project such as vertical extension of apartment building. This paper focuses on the load distribution characteristics of existing and reinforcing piles when reinforcing pile is installed to the existing foundation. Allowable bearing load was initially applied on the foundation slab supported with four existing piles and then, one reinforcing pile was installed at the center of foundation slab and additional load was applied. The experimental results showed the Load Distribution Ratio (LDR) between existing and reinforcing piles converged after the applied load exceeded allowable bearing capacity of all piles. Laboratory tests were also performed for the cases of 60 %, 80 %, 100 % unloading level of allowable bearing load. After unloading step, one reinforcing pile was installed at the center of foundation slab and additional load was applied. The results showed that reloading load level at which LDR between existing and reinforcing piles converged decreased as the amount of unloading load increased.

자전거 프레임의 소재 및 종류에 따른 피로특성

권경배,정성균,Kwon, Kyoung-Bae,Cheong, Seong Kyun 한국안전학회 2017 한국안전학회지 Vol.32 No.5

Bicycles are very popular sporting goods in these days. Thus, the durability of bicycles is very important for the safety of bicyclists. It is well known that a bicycle frame is a major component which is essential to the safety and performance of a complete bicycle. In this study, the durability of bicycle frames were experimentally investigated under the fatigue load. Eighty bicycle frames with different types and materials were prepared and tested according to EN standards. Three kinds of fatigue loads, that is, pedalling, vertical and horizontal fatigue load, which occur constantly during riding a bicycle, were applied to the bicycle frames. The experimental results show that the horizontal fatigue load was the severest mode to pass EN standard. The pass ratio of horizontal fatigue load test was 45.2%, while the pass ratio of vertical fatigue load test was 100%. Most of cracks were found at the right side of bottom bracket shell and at the intersection area between head tube and down tube. It seems that the experimental results can be applied to improve the safety and performance of a bicycle frame.

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.

Performance of Tunnel Feet-Lock Pipe (TFP) in Sharing Vertical Foundation Load

Lijun Chen,Jianxun Chen,Yao Li,Yanbin Luo,Yongjun Mu,Taotao Hu,Chuanwu Wang 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.3

During the tunnel construction in soft ground, the insufficient bearing capacity of tunnel foundation usually causes a series of settlement problems. Tunnel feet-lock pipe (TFP) has been widely used to take the vertical load acting at the foundation of a tunnel foot. However, the detailed bearing performance of TFP is still not clear, and there is a lack of quantitative research. In this paper, a simple analytical approach is adopted to evaluate the performance of the TFP, and the main parameters affecting the supporting performance of the TFP are analyzed. The results show that the ϕ42 − ϕ140 TFP with the angle of 10° can take 3.8% −40.4% of vertical load. TFP has an effective length of 1.7 m − 2.8 m, which is related to the relative stiffness between the TFP and the stratum. With the increase of the installation angle, the TFP shares more vertical load. This trend is more obvious when the angle of the TFP is greater than 20°. If the proportion coefficient of the subgrade reaction coefficient is doubled, the vertical load shared by the TFP can be increased by 34% − 38%. For every 10 cm increase in overbreak behind the steel rib, the vertical load shared by TFP is reduced by 16%.