모래지반에서 재하방법이 반복수평하중을 받는 말뚝의 거동에 미치는 영향

백규호,김영준,이승연 한국지반공학회 2011 한국지반공학회논문집 Vol.27 No.3

The behavior of laterally cyclic loaded piles is affected by the magnitude and number of cycles of cyclic lateral loads as well as loading method (1-way or 2-way loading). In this study, calibration chamber tests were carried out to investigate the effects of loading method of cyclic lateral loads on the behavior of piles driven into sand. Results of the chamber tests show that the permanent lateral displacement of 1-way cyclic loaded piles is developed in the same direction as the first loading, whereas that of 2-way cyclic loaded piles is developed in the reverse direction of the first loading. 1-way cyclic lateral loads cause a decrease of the ultimate lateral load capacity of piles, and 2-way cyclic lateral loads cause an increase of the ultimate lateral load capacity of piles. The change of ultimate lateral load capacity with loading method of cyclic lateral loads increases with increasing number of cycles. It is also observed that the 1-way cyclic loads generate greater maximum bending moment than 2-way cyclic loads for piles in cyclic loading step and generates smaller maximum bending moment for piles in the ultimate state. It can be attributed to the difference in compaction degree of the soil around the piles with loading method of cyclic lateral loads. In addition, it is founded that 1-way and 2-way cyclic lateral loads cause a decrease in the maximum bending moment of piles in the ultimate state compared with that of piles subjected to only monotonic loads.

모래지반에서 반복수평하중을 받는 항타 말뚝의 수평거동

백규호 한국지반공학회 2010 한국지반공학회논문집 Vol.26 No.12

The behavior of laterally cyclic loaded piles is different from that of piles under monotonic loading and depends on soil and load characteristics. In this study, model pile load tests were performed using a calibration chamber to investigate the effects of load characteristics on the behavior of laterally cyclic loaded piles in sand. Results of the model tests show that the ultimate lateral load capacity of laterally cyclic loaded piles decreases linearly with increasing the number of cycles and increases slightly with increasing the magnitude of cyclic lateral loads. When the piles reach the ultimate state, the maximum bending moment developed in the piles decreases linearly with increasing the number of cycles and it occurs at a depth of 0.36 times pile embedded length for all the number of cycles. However, both the magnitude and depth of the maximum bending moment of piles in the ultimate state increase slightly as the magnitude of cyclic lateral loads increases. It is also observed that the cyclic lateral loading generates a decrease in the ultimate lateral load capacity and maximum bending moment for piles in the ultimate state. In addition, based on the model test results, a new empirical equation for the ultimate lateral load capacity of laterally cyclic loaded piles in dense sand is also proposed. A comparison between predicted and measured load capacities shows that the proposed equation reflects satisfactorily the model test results.

Elastic Lateral Buckling of Cantilever Litesteel Beams Under Transverse Loading

Cyrilus Winatama Kurniawan,Mahen Mahendran 한국강구조학회 2011 International Journal of Steel Structures Vol.11 No.4

The LiteSteel Beam (LSB) is a new hollow flange channel section developed by OneSteel Australian Tube Mills using its patented dual electric resistance welding and automated continuous roll-forming technologies. The LSB has a unique geometry consisting of torsionally rigid rectangular hollow flanges and a relatively slender web. Its flexural strength for intermediate spans is governed by lateral distortional buckling characterised by simultaneous lateral deflection, twist and web distortion. Recent research on LSBs has mainly focussed on their lateral distortional buckling behaviour under uniform moment conditions. However, in practice, LSB flexural members are subjected to non-uniform moment distributions and load height effects as they are often under transverse loads applied above or below their shear centre. These loading conditions are known to have significant effects on the lateral buckling strength of beams. Many steel design codes have adopted equivalent uniform moment distribution and load height factors based on data for conventional hot-rolled, doubly symmetric I-beams subject to lateral torsional buckling. The non-uniform moment distribution and load height effects of transverse loading on cantilever LSBs, and the suitability of the current design modification factors to include such effects are not known. This paper presents a numerical study based on finite element analyses of the elastic lateral buckling strength of cantilever LSBs subject to transverse loading, and the results. The applicability of the design modification factors from various steel design codes was reviewed, and suitable recommendations are presented for cantilever LSBs subject to transverse loading.

사질토 지반에서 수평하중에 따른 단일강관말뚝의 거동특성에 관한 실험적 연구

김대현(Kim, Daehyeon),이태광(Lee, Tae-Gwang),김선학(Kim, Sun-Hak) 한국산학기술학회 2015 한국산학기술학회논문지 Vol.16 No.5

해상풍력기초를 설계함에 있어 사용하중에 대해 극한적인 조건뿐만 아니라 지속적인 동적하중에 대해 기초의 거동을 정확하게 파악하여 안정적이고 경제적인 기초를 개발할 필요성이 있다. 이를 위하여 강관말뚝을 일정비율로 축소시켜 모형 말뚝을 제작하고, 모형토조에 모래층을 500mm의 높이로 포설한 후 모형말뚝을 모델링하여 정적 및 반복 수평재하실험을 실시하였다. 그 결과, 정적수평재하시 모형말뚝의 길이/직경(L/D)이 클수록 하중에 따른 변위는 증가하는 반면, 반복수평재하 시 하중재하 횟수가 증가할수록 반복수평하중 1회당 발생하는 말뚝의 수평변위는 감소하였고 지반이 조밀할수록 반복수평하 중에 의한 말뚝의 극한수평지지력의 증가율이 작아지는 것으로 나타났다. 또한 휨모멘트의 분포형상은 지반의 상대밀도에 상관없이 유사한 형태를 보였으며, 최대휨모멘트는 지표면으로부터 170mm지점에서 발생하는 것으로 나타났다. 그리고 지반 의 상대밀도가 증가할수록 정적수평재하와 반복수평재하 조건에서 발생하는 최대휨모멘트는 증가했다. In order to fulfill the needs of reliable and economically feasible foundation, engineers should consider not only the working load that can endure extreme conditions but also apprehending precise behavior of continuous dynamic load while designing the foundation of offshore wind power generators. To actualize the foundation, a model pile was made in miniature. Also, calibration chamber was made and a 500mm height of sand-bed was made to perform “static lateral load experiment” and “repetitive loading experiment”, total of two Lateral load tests. As a result, in Static Lateral load test, the bigger length/diameter of model pile led an increase in load displacement. However, when performing “Cyclic Lateral load test”, the increase in number of under loading led the decrease in horizontal displacement from each repeated lateral load. While performing Static Lateral load test and repeated loading experiment, we could observe the decreasing in the rate of ultimate lateral load capacity increase of the pile. Also, it turned out that the higher relative density of the ground, the lower ultimate lateral load capacity by repeated horizontal loading.

A Theoretical Study of Estimating the Elastic Responses of Framed Self-Centering Wall Structures under Lateral Loading

Xiaobin Hu,Chen Lu,Xiaoqing Zhu,Xiangdong Xie 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.12

The framed self-centering wall (FSCW) structure is a newly-emerged special type of seismic-resistant system. However, the related studies rarely concern the theoretical investigation of the FSCW structures subjected to lateral loading, which is of great importance for seismic design of the FSCW structures. In view of this, the analytical model of the FSCW structures is firstly developed, then the fundamental equations that govern the elastic responses of FSCW structures under lateral loads are formulated and the corresponding analytical solutions are derived. Meanwhile, the developed analytical model is validated by the finite element method, which shows that the developed model has a good reliability in predicting the elastic responses of FSCW structures sustaining lateral loading. Utilizing the proposed method, the effects of the post-tensioned (PT) tendon and dampers on the behaviors of the FSCW structure under lateral loading are investigated. Moreover, a comparative study of mechanical performance between the FSCW structure and conventional structures under lateral loading is conducted. The results show that, in terms of the lateral displacement and shear force responses of the frame, the mechanical performance of the FSCW structure subjected to lateral loading generally falls in between those of the conventional frame-shear wall structure and the moment-resisting frame structure.

모형실험에 의한 무리 콘크리트 말뚝의 수평거동 특성

권오균(Kwon, Oh-Kyun),박종운(Park, Jong-Un),김진복(Kim, Jin-Bok),임동현(Lim, Dong-Hyun) 한국지반환경공학회 2012 한국지반환경공학회논문집 Vol.13 No.8

본 연구에서는 모형실험을 실시하여 수평하중 작용 시 무리말뚝의 거동을 평가하였다. 암반을 모사한 콘크리트 블럭에 모형말뚝을 말뚝직경(D)의 1배로 근입시키고, 상부에 모래를 1m 깊이로 포설한 2×3 배열의 무리말뚝에 대하여 모형실험을 실시하였다. 그리고 말뚝길이는 11D, 15D와 20D의 세 종류이다. 각 조건에 대한 모형실험의 결과를 수평하중-변위 곡선으로 나타냈으며, 지반 속에서 발생한 말뚝의 변위를 측정하였다. 모형실험 결과, 말뚝 길이/직경의 비(L/D)가 작아질수록 항복하중은 커지고, 항복하중에서의 수평변위는 증가하는 경향을 나타냈다. 도로교설계기준의 수평변위 기준인 15mm에서의 하중을 비교한 결과, L/D가 11, 15, 20에서의 항복하중은 각각 11.7, 6.2, 3.4kN으로 나타났다. 모든 실험 조건에 대하여 지반 속에서 발생한 말뚝의 수평변위는 거의 직선적으로 나타났고, 모형 말뚝이 콘크리트 블록에 소켓된 지점에서 파괴가 발생하였다. The lateral behavior characteristics of concrete group pile under the lateral load were examined by the laboratory model tests in this study. Piles were socketed 1D(D : pile diameter) in the concrete block, and model tests were executed on 2×3 group piles, of which the length were 11D, 15D and 20D. All results of loading tests under each condition was presented by the lateral load-displacement curves, and the displacements in the ground under the lateral loads were measured. As a results of model tests, as the ratio of pile length/diameter(L/D) was decreased, the yielding load and the lateral displacement at that load were increased. The yielding load was evaluated as the load at lateral displacement of 15 mm. The yielding loads at the pile length of 11D, 15D and 20D were 11.7, 6.2kN and 3.4kN. The lateral displacements of pile in the ground under each condition were measured linearly and the failure occurred at the location where the piles were socketed in concrete block.

긴장력이 도입된 콘크리트 충전 강관말뚝을 사용한 복합말뚝의 수평거동 특성

박노원,백규호 한국지반공학회 2018 한국지반공학회논문집 Vol.34 No.12

Concrete filled steel tube (PCFT) piles, which compose PHC piles inside thin steel pipes, were developed to increase the flexural strength of the pile with respect to the horizontal load. In order to compare the flexural strength of PCFT pile with that of steel pipe pile, several flexural tests were performed on the PCFT and steel pipe piles with the same diameter and the P-M curves for both piles were constructed by the limit state design method. Four test piles were also installed and lateral pile load tests were performed to compare the lateral load capacities and lateral behaviors of the hybrid composite piles using PCFT piles and the existing piles such as HCP and steel pipe piles. The flexural test results showed that the flexural strength of PCFT piles was 18.7% higher than that of steel pipe piles with thickness of 12mm and the same diameter, and the mid-span deflection of piles was 50% lower than that of steel pipe piles at the same bending moment. From the P-M curves, it can be seen that the flexural strength of PCFT piles subjected to the vertical load is greater than that of steel pipe piles, but the flexural strength of PCFT piles subjected to the pullout load is lower than that of steel pipe piles. In addition, field pile load tests showed that the PCFT hybrid composite pile has 60.5% greater lateral load capacity than the HCP and 35.8% greater lateral load capacity than the steel pipe pile when the length of the upper pile in hybrid composite piles was the same.

동적 수평하중에 의한 단일 경사말뚝의 거동특성

김지성,노정섭,강기천,Kim, Jiseong,Noh, Jeongseob,Kang, Gi-Chun 한국지반공학회 2017 한국지반공학회논문집 Vol.33 No.9

본 연구는 모형시험을 통해 반복수평하중이 작용하는 단일경사말뚝의 거동 특성을 파악하고자 한다. 반복하중은 일방향과 양방향으로 작용 시켰으며, 지반의 상대밀도를 달리하여 수평저항력과 휨모멘트의 변화 등을 분석하였다. 그 결과, 일방향 및 양방향 반복수평하중이 작용할 경우 Out batter, Plumb, In batter 순으로 수평저항력과 최대 휨모멘트는 증가하였다. 최대 휨모멘트 발생위치는 일방향 보다 양방향 반복수평하중을 가할 때 조금 더 깊은 곳에서 나타났다. 또한, 상층의 모멘트는 Out batter, Plumb, In batter 순으로 모멘트가 증가하나 하층의 경우 Out batter, Plumb, In batter 순으로 감소하였고 일방향에 비해 양방향 반복수평하중이 작용할 때 상 하층의 모멘트 변화가 작게 나타났다. The purpose of this study is to investigate the behavior of a single batter pile with repeated lateral loading through model tests. Repeated loads were applied in one direction and two directions, and lateral resistance and bending moment were analyzed by varying the relative density of the ground. As a result, lateral resistance and maximum bending moment were increased in the order of Out batter, Plumb, and In batter when one-way and two-way dynamic lateral loads were applied. The depth at the maximum bending moment was more deeper with the loading. The moments at bottom layer were decreased in the order of Out batter, Plumb, and In batter but upper moments were increased with the same order. Also, various bottom and upper moments were small when the two-way dynamic lateral load was applied compared to one-way lateral load.

들기 작업시 중량물의 비대칭 무게중심 및 상체 옆으로 기울임에 따른 허리근육의 Peak EMG 진폭 비교

한승조(Han, Seung-Jo),김선욱(Kim, Sun-Uk) 한국산학기술학회 2012 한국산학기술학회논문지 Vol.13 No.10

본 연구의 목적은 중량물 들기 작업시 비대칭 무게중심과 상체 옆으로 기울임 여부가 어떻게 L5/S1 주변 허 리 근육의 Peak EMG 진폭에 영향을 미치는지를 알아보는 것이다. 요통을 포함한 근골격계질환은 무겁지 않은 물체 의 지속적인 반복 취급뿐만 아니라, 일회성의 커다란 부하도 신체 조직의 부담으로 작용하여 발생할 수 있다. 11명의 20대 대학생 남성은 15.8kg의 물체를 들어올리는 Task를 3회 실행하였다. 이 때 대칭 무게중심의 물체를 상체를 기울 이지 않고 들어 올리는 경우, 비대칭 무게중심의 물체를 상체를 기울이지 않고 들어 올리는 조건, 그리고 비대칭 무 게중심의 물체를 상체를 기울여서 들어 올리는 경우에 따라 6개의 L5/S1 주변의 근육들로부터 Peak EMG 진폭이 수 집되어 분석되었다. 결과는 비대칭 무게중심을 지닌 물체 취급시 무게중심에서 먼 쪽의 허리 근육에서 Peak EMG 진 폭이 발생하고, 그 진폭의 크기는 대칭 무게중심 물체를 취급하는 경우보다 크게 나타났다. 또한, 비대칭 무게중심의 물체를 취급할 경우 물체나 상체를 물체의 무게중심 방향으로 기울이는 것은 기울이지 않을 때보다 대측성 등근육에 서 Peak EMG 진폭 증가시켰다. 이러한 연구 결과는 비대칭 무게중심의 중량물을 들어 올리는 작업에서 요통 발생을 예방하기 위한 행정적인 조치로써 가능하면 상체를 전두면 기준으로 기울이지 않는 작업자 자세 조언이 필요함을 말 해준다. This study was aimed at the relationship between peak EMG amplitude on low back muscles acting on L5/S1 and load center of gravity, trunk lateral bending while lifting an object. Musculoskeletal disorders including low back pain can occur even when handling heavy objects only once as well as when doing non-heavy materials repeatedly. 11 male subjects with average 23 age were required to lift a 15.8kg object symmetrically three times. Peak EMG amplitudes on 6 muscles related with L5/S1 were recorded and analyzed. The lifting conditions consisted of lifting symmetric load with no trunk lateral bending, asymmetric load with no trunk lateral bending, and asymmetric load with trunk lateral bending to the load center of gravity within an object. The results showed that peak EMG amplitude on back muscles contralateral to load center of gravity was observed greater in comparison with the symmetric load. Also, in case of lifting asymmetric load the posture with trunk lateral bending increased peak EMG amplitude on muscles contralateral to load center of gravity more than with no trunk lateral bending. This research can be used as one administrative intervention in order to reduce the low back pain incidence with suggesting workers that they keep the trunk not bending to load center of gravity if possible when lifting a heavy asymmetric object.

블록식 방파제의 수평저항력 평가를 위한 실내모형실험 II : 보강형 싱글블럭의 반복수평 하중에 대한 저항

강기천,김지성,Kang, Gichun,Kim, Jiseong 한국지반신소재학회 2021 한국지반신소재학회 논문집 Vol.20 No.4

항만구조물의 경우 정적인 하중 뿐만 아니라 파압과 같이 반복적인 하중을 받는 구조물임에 따라 반복적인 하중을 받는 구조물의 특성을 파악하는 것이 중요하다. 따라서 본 연구는 반복 수평하중에 의한 말뚝으로 보강된 블록식 방파제의 거동특성을 실내모형실험을 통해 구하였다. 말뚝의 근입 깊이가 깊어질수록 수평저항력이 증가하는 경향이 나타났으며, 하중이 반복될수록 수평저항력의 기울기는 점차 완만하게 나타났다. 휨모멘트는 후열말뚝이 전열말뚝보다 크게 나타났다. 지반내에서의 말뚝의 휨모멘트는 Broms(1964)의 사질토지반에서 말뚝두부 자유일 때와 유사하게 나타났다. In the case of harbor structures, it is important to understand the characteristics of structures that are subjected to repeated loads as they are structures that receive repetitive loads such as wave pressure as well as static loads. In this study, the lateral resistance according to the pile embeded depth of the block breakwater reinforced with piles by cyclic lateral loads was obtained through an model experiment. As the depth of embedment of the pile increased, the lateral resistance showed a tendency to increase. As the load was repeated, the gradient of the lateral resistance gradually appeared to be gentle. The bending moment of the rear pile was larger than that of the front pile. The bending moment of piles in the ground was similar to that when the pile head was free in the cohesionless of Broms (1964).