• 한국지진공학회논문집
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• 제23권5호
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• pp.249-259
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• 2019

To study the seismic resistance of the shear capacity of the RC beam-column joints of two-story and four-story RC buildings, sample buildings are designed with ordinary moment resisting frame. For the shear capacity of joints, the equations of FEMA 356 and NZ seismic assessment are selected and compared. For comparison, one group of buildings is designed only for gravity loads and the other group is designed for seismic and gravity loads. For 16 cases of the designed buildings, seismic performance point is evaluated through push-over analysis and the capacity of joint shear strength is checked. Not only for the gravity designed buildings but also for seismic designed buildings, the demand of joint shear is exceeding the capacity at exterior joints. However, for interior joint, the demand of joint shear exceeds the capacity only for one case. At exterior joints, the axial load stress ratio is lower than 0.21 for gravity designed buildings and 0.13 for seismic designed buildings.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.808-813
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• 2009

Top-down method is widely used for urban area construction for its advantages in reducing environmental problems such as dust and noise, and saving construction cost depending on given conditions of a construction site. Because the excavation and construction of super- and sub-structures of the building have to be proceeded simultaneously, a column has to be embedded prior to excavation. This column is called a pillar column or pre-founded column. Usually a wide flange section is used for these columns. To place the columns, usually the diameter of casing holes needs to be larger than the section of the wide flange itself in order to accommodate a couple of tremie pipes for pouring concrete. In this paper, a newly developed method of using circular pipe as an alternative to the existing wide flange section is discussed. The crucial part of the new method is to develop a connection between the circular column and concrete flat slabs. For shear force transfer from concrete slab to the concrete filled tube (CFT) column, shear jackets with studs and shear bands are proposed. The studs are welded on the jackets at shop and placed around the circular column on site. The shear bands are welded on the outer side of the CFT at shop and inserted into ground with the CFT. Test results and application of the method to a construction site are also provided in this paper.

• Structural Engineering and Mechanics
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• 제73권2호
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• pp.167-179
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• 2020

This study provides a simplified method for the evaluation of shear lag stress in rectangular box T-joints. The occurrence of shear lag phenomenon in the box T-joint generates stress concentration localized at both web-flange junctions of the beam, which leads to cracking or failure in the weld region of the joint. To prevent such critical circumstance, peak stress at the weld region is required to be checked during a preliminary design stage. In this paper, the shear lag stresses in the T-joints were evaluated using least-work solution in which the longitudinal displacements of the beam flange and web were presumed. The evaluation process considered particularly the effect of column flange flexibility, which was represented by an axial spring model, on the shear lag stress distribution. A simplified method for stress evaluation was provided to avoid solving complex mathematical problems using a stress modification factor β_s from a parametric study. The results showed that the proposed method was valid for predicting the shear lag stress in the box T-joints manually, as well compared with finite element results. The results are further summarized, discussed, and clarified that more flexible column flange caused higher stress concentration.

• 한국강구조학회 논문집
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• 제29권5호
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• pp.377-387
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• 2017

이 연구에서는 강판 매입형 합성기둥의 Push-out Test를 통해 강재와 콘크리트의 부착면적에 따른 영향을 알아보았다. 이로써 부착면적이 넓을수록 부착응력은 작아진다는 경향이 조사되었다. 또한 소규모 매입형 합성기둥의 경우에는 설계기준에서 제시하는 공칭부착 응력값이 과소하게 적용되는 것을 확인하였다. 다음으로 H형강 매입형 합성기둥의 Push-out Test를 통해 전단연결재의 수와 간격에 따른 영향을 알아보았다. 이로써 전단연결재의 전단거동을 파악할 수 있었다.

• Structural Engineering and Mechanics
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• 제41권1호
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• pp.43-65
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• 2012

The primary objective of this study was to identify concrete contribution to the initial shear strength of reinforced concrete (RC) hollow columns under lateral loading. Seven large-scale RC rectangular hollow column specimens were tested under monotonic or cyclic lateral loads. The most important design parameter was column length-to-depth aspect ratio ranging between 1.5 and 3.0, and the other test variables included web area ratio, hollow section ratio, and loading history. The tests showed that the initial shear strength reduced in a linear pattern as the column aspect ratio increased, and one specimen tested under cyclic loading achieved approximately 83% of the shear strength of the companion specimen under monotonic loading. Also, several pioneering shear models proposed around the world, all of which were mainly based on tests for columns with solid sections, were reviewed and compared with the test results of this study, for their possible applications to columns with hollow sections. After all, an empirical equation was proposed for concrete contribution to the initial shear strength of RC hollow columns based on fundamental mechanics and the test results.

• 콘크리트학회논문집
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• 제24권5호
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• pp.517-524
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• 2012

이 논문에서는 푸쉬오버해석을 통해 보-기둥 접합부 비탄성 전단거동과 고차모드를 고려한 횡하중 수직분포 형태가 구조물 거동에 미치는 영향을 알아보기 위해 지반조건 $S_B$ 내진설계범주 C에 대해서 5층 철근콘크리트 보통모멘트골조를 KBC2009에 맞게 구조설계 하였다. 보 및 기둥 부재의 휨모멘트-곡률 관계는 섬유모델(fiber model)로 확인하였으며 보-기둥 접합부 모멘트-회전각 관계는 simple and unified joint shear behavior model과 보-기둥 접합부 모멘트 평형관계를 이용하여 확인하였다. 푸쉬오버해석 결과 보-기둥 접합부를 강체로 고려하는 경우 구조물의 강성도 및 강도가 과대평가 되었으나 반응수정계수는 접합부 비탄성거동과 관계없이 KBC2009 보통모멘트골조 계수를 만족하여 구조 설계 과정에서 보-기둥 접합부의 비탄성 전단거동을 고려하지 않아도 문제가 없을 것으로 판단된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.470-473
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• 2006

Past experiences from recent earthquakes indicate that shear failures of beam-column connections were one of the main reasons causing significant damages and collapses of RC structures subjected to earthquake loadings. Many researchers and engineers have conducted to propose an effective way to improve the joint shear strength of RC connections. This paper presents an analytical model for the RC exterior beam-column joints strengthened with CFRP sheets. In the analytical model, the effect of shear behavior of the RC beam-column joint, bond slip of the beam longitudinal reinforcements and CFRP sheets were considered and incorporated into the non-linear structural analysis program. Final analytical results were compared with those from the experiment of eight exterior RC beam-column specimens. The analytical results showed that the developed connection model is very useful to investigate the hysteretic joint behavior and overall load-displacement response of the RC beam-column connections strengthened with CFRP sheets.

• 한국구조물진단유지관리공학회 논문집
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• 제26권2호
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• pp.51-58
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• 2022

플랫 플레이트는 매우 경제적인 구조시스템으로서 고층건물과 아파트, 지하 주차장등에 널리 쓰인다. 하지만 기둥-슬래브 접합부가 뚫림전단에 취약하기 때문에 건물의 연쇄붕괴로 이어질 수 있는 단점이 있다. 이에 본 연구에서는 뚫림전단강도 증가, 연성능력 향상, 시공성면에서 뛰어난 나선형 철근 전단 보강재가 제안되었으며, 실험을 통해 나선형 철근 전단보강재의 강도를 평가하였다. 현행 기준은 전단보강된 슬래브-기둥 접합부의 뚫림전단강도를 정확하게 예측하지 못하고 있다. 그 이유는 전단보강재가 설치되는 슬래브의 두께가 얇을경우 정착길이가 확보되지 못하여 전단보강재가 항복강도에 이르기 전에 파괴가 일어나기 때문이다. 이에 본 연구에서는 유한요소해석 프로그램 LUSAS ver14.3을 이용하여 나선형 전단보강재의 보강성능에 영향을 미치는 변수를 분석하여 강도보정계수를 도출하였다. 또한 CEB-FIP 데이터뱅크에 수록된 실험체의 회귀분석을 통해 전단보강된 슬래브-기둥 접합부의 뚫림전단강도 산정식을 제안하였다.

• Geomechanics and Engineering
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• 제32권6호
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• pp.567-581
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• 2023

Enhanced vertical load capacity of the ground reinforced with the stone columns drew great attention by the researchers as it deals with many of the geotechnical difficulties associated with the weak ground. Recently, it has been found that the stone columns are also prone to fail under the shear load when employed beneath the embankments or the foundations susceptible to lateral loads. In this study, the effect of various encasement conditions on the lateral deflection of stone columns is investigated. A method of dual layers of encasement has been introduced and its the effect on lateral load capacity of the stone columns has been compared with those of the single encased stone column and the un-encased stone columns. Large shear box tests were utilised to generate the shear deformation on the soil system under various normal pressure conditions. The stiffness of the soil-stone column combined system has been compared for various cases of encasement conditions with different diameters. When subjected to lateral deformation, the encased columns outperformed the un-encased stone columns installed in loose sand. Shear stress resistance is up to 1.7 times greater in dual-layered, encased columns than in unencased columns. Similarly, the secant modulus increases as the condition changes from an unencased stone column to single-layer encasement and then to dual-layer encasement, indicating an improvement in the overall soil-stone column system.

• Structural Engineering and Mechanics
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• 제9권6호
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• pp.601-613
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• 2000

Existing models for the shear strength degradation of reinforced concrete members present varied conceptual approaches to interpreting test data. The relative superiority of one approach over the others is difficult to determine, particularly given the sparseness of ideal test data. Nevertheless, existing models are compared using a suite of test data that were used for the development of one such model, and significant differences emerge. Rather than relying purely on column test data, the body of knowledge concerning degradation of concrete as a material is considered. Confined concrete relations are examined to infer details of the degradation process, and to establish a framework for developing phenomenologically-based models for shear strength degradation in reinforced concrete members. The possibility of linking column shear strength degradation with material degradation phenomena is explored with a simple model. The model is applied to the results of 7 column tests, and it is found that such a link is sustainable. It is expected that models founded on material degradation phenomena will be more reliable and more broadly applicable than the current generation of empirical shear strength degradation models.