• 한국구조물진단유지관리공학회 논문집
• /
• 제9권1호
• /
• pp.283-292
• /
• 2005

강판으로 부분 보강된 철근콘크리트 보의 조기파괴하중을 추정하기 위하여 변수연구를 수행하였다. 설계변수는 전단철근의 유무, 비보강길이의 비, 인장철근에 대한 보강 강판의 철근비, 전단지간 대 보강된 보의 유효깊이 비로 하였다. 유한요소해석 결과, 강판으로 부분 보강된 철근콘크리트 보의 조기파괴를 지배하는 1차 적인 요인은 비보강길이이지만 보강철근비, 전단지간 대 유효깊이의 비 등도 영향을 주는 것으로 나타났다. 설계변수의 조합작용을 고려한 근사식을 기존의 실험결과와 비교한 결과 거의 일치하였다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1998년도 봄 학술발표회논문집(II)
• /
• pp.585-591
• /
• 1998

In the case of reinforced concrete beams strengthening by steel plate, sometimes these beams collapse due to the stress concentration at the ends of steel plates before the design expected failure. This kind of failure is called premature failure. This study analyzes the behavior of strengthened RC beams to control premature failure of these plated beams with either changing the geometries at the ends of plates or strengthening steel plates beside the ends. The results from the former cases show that, the effect of expanded plates sections at the ends was very small, and the beams which are rounded the ends of plates effectively increased the initial rip-off loads about 14% compared with control beam but the ultimate loads was almost same. However, the beams in the latter cases effectively increased the initial and the ultimate rip-off loads with changing failure mode, especially around 14~19% in the ultimate rip-off load comparing with control beam.

• Steel and Composite Structures
• /
• 제20권6호
• /
• pp.1193-1203
• /
• 2016

This paper focuses on the analytical behavior of modular circular concrete-filled tubular (CFT) column with enhanced bracing details. To design a full-scale bridge pier of multiple circular concrete-filled tubes, numerical analysis was used to evaluate structural performance according to load directivity. In previous research (Ma et al. 2012, Shim et al. 2014), low cycle fatigue failure at bracing joints was observed, so enhanced bracing details to prevent premature failure are proposed in this analysis. The main purpose of this research is to investigate seismic performance for the diagonal direction load without premature failure at the joints when the structure reaches the ultimate load. The ABAQUS finite-element software is used to evaluate experimental performance. A quasi-static loading condition on a modular bridge pier is introduced to investigate structural performance. The results obtained from the analysis are evaluated by comparing with load-displacement responses from experiments. The concrete-filled tubes with enhanced bracing details showed higher energy dissipation capacity and proper performance without connection failure for a diagonal load.

• Structural Engineering and Mechanics
• /
• 제66권4호
• /
• pp.543-555
• /
• 2018

Fiber Reinforced Polymer (FRP), which has a high strength to weight ratio, are now regularly used for strengthening of deficient reinforced concrete (RC) structures. While various researches have been conducted on FRP strengthening, an area that still requires attention is predicting the debonding failure load of prestressed FRP strengthened RC beams. Application of prestressing increases the capacity and reduces the premature failure of the beams largely, though not entirely. Few analytical methods are available to predict the failure loads under flexure failure. With this paucity, this research proposes a method for predicting debonding failure induced by intermediate crack (IC) for prestressed FRP-strengthened beams. The method consists of a numerical study on beams retrofitted with prestressed FRP in the tension side of the beam. The method applies modified Branson moment-curvature analysis together with the global energy balance approach in combination with fracture mechanics criteria to predict failure load for complicated IC-induced failure. The numerically simulated results were compared with published experimental data and the average of theoretical to experimental debonding failure load is found to be 0.93 with a standard deviation of 0.09.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
• /
• pp.993-1000
• /
• 2009

In general, a drilled shaft embedded in weathered rock has a large load bearing capacity. Therefore, most of the load tests are performed only up to the load level that confirms the pile design load capacity, and stopped much before the failure load of the pile is attained. If a reliable failure load value can be extracted from the premature load test data, it will be possible to greatly improve economic efficiency as well as pile design quality. The main purpose of this study is to propose a standard for judging the reliability of the failure load of piles that is obtained from extrapolated load test data. To this aim, eleven static load test data of load-displacement curves were obtained from testing of piles to their failures from 3 different field sites. For each load-displacement curve, loading was assumed as 25%, 50%, 60%, 70%, 80%, and 90% of the actual pile bearing capacity. The limited known data were then extrapolated using the hyperbolic function, and the failure load was re-determined for each extrapolated data by the ASCE 20-96 method (1997). Statistical analysis was performed on the reliability of the re-evaluated failure loads. The results showed that if the ratio of the maximum-available displacement to the failure-load displacement exceeds 0.6, the extrapolated failure load may be regarded as reliable, having less than a conservative 20% error on average. The applicability of the proposed standard of judgment was also verified with static load test data of driven piles.

• Structural Engineering and Mechanics
• /
• 제77권2호
• /
• pp.273-291
• /
• 2021

The strut-and-tie method (STM) has been widely accepted and used as a rational approach for the design of disturbed regions ('D' regions) of reinforced concrete members such as in corbels and deep beams, where traditional flexure theory does not apply. This paper evaluates the applicability of the equilibrium based STM in strength predictions of deep beams (with rectangular and circular cross-section) and corbels using the available experiments in literature. STM is found to give fairly good results for corbel and deep beams. The failure modes of these deep members are also studied, and an optimum amount of distribution reinforcement is suggested to eliminate the premature diagonal splitting failure. A comparison with existing empirical and semi empirical methods also show that STM gives more reliable results. The nonlinear finite element analysis (NLFEA) of 50 deep beams and 20 corbels could capture the complete behaviour of deep members including crack pattern, failure load and failure load accurately.

• KIEAE Journal
• /
• 제10권1호
• /
• pp.25-31
• /
• 2010

An experimental investigation of composite beams composed of wide flange steel and precast concrete is presented. The bottom flange of the steel section is encased in precast concrete. The composite beams tested in this study were designed to reduce the depth of the slab and beam. The slabs are constructed on top of the edges of the Structural Composite Hybrid System, instead of on top of the steel flange, decreasing the depth of the beams. When concrete is cast on the metal deck plate located on the edges of the precast concrete, the weight of the concrete slabs and other construction loads must be supported by the contacts between the steel and the precast concrete. This interface must not exhibit bearing failures, shear failures, and failures caused by torque due to the loading of the precast concrete. When the contact area between the concrete and the bottom flange of the steel beam is small, these failures of the concrete are likely and must be prevented. The premature failure of precast concrete must not also be present when the weight of the concrete slabs and other construction loads is loaded. This paper presents a load carrying capacity of Structural Composite Hybrid System in order to observe the failure mode. The symmetrically distributed loading that caused the failure of the composite beam was found. The paper also provides design recommendations of such type of composite structure.

• 한국공간구조학회논문집
• /
• 제22권4호
• /
• pp.99-107
• /
• 2022

Existing reinforced concrete building structures constructed before 1988 have seismically-deficient reinforcing details, which can lead to the premature failure of the columns and beam-column joints. The premature failure was resulted from the inadequate bonding performance between the reinforcing bars and surrounding concrete on the main structural elements. This paper aims to quantify the bond-slip effect on the dynamic responses of reinforced concrete frame models using finite element analyses. The bond-slip behavior was modeled using an one-dimensional slide line model in LS-DYNA. The bond-slip models were varied with the bonding conditions and failure modes, and implemented to the well-validated finite element models. The dynamic responses of the frame models with the several bonding conditions were compared to the validated models reproducing the actual behavior. It verifies that the bond-slip effects significantly affected the dynamic responses of the reinforced concrete building structures.

• 콘크리트학회논문집
• /
• 제22권4호
• /
• pp.461-472
• /
• 2010

이 논문은 새로운 수직 접합부를 가진 프리캐스트 벽체의 거동에 관한 연구이다. PC 벽체를 이용한 리모델링 건설을 위해서는 효율적이고 경제적인 조립 방법이 필요하다. C형 수직 접합부를 가진 PC 벽체 시스템은 수직방향의 벽체 사이의 휨모멘트를 전달하도록 하고, 반면에 벽체 중심에 있는 전단키는 전단력을 부담하도록 하였다. 제안된 수직 접합부는 벽체 단부에 서로 다른 방향의 슬롯 때문에 조립이 용이하다. 횡력을 받는 일자형 PC 벽체 시스템을 강성, 강도 그리고 파괴 모드에 대해 기존의 RC 벽체와 비교하였으며, 힘과 처짐과의 관계와 접합부의 조기파괴에 관해 알아보았다. 실험 결과 벽체 단부에 설치된 수직 철근이 먼저 항복하였고, 최종 변형은 접합부의 조기 파괴에 의해 결정되었다. 그리고 벽체에서 효과적인 전단력 전달을 위한 대각선 철근은 그다지 효과적이지 않았다. 단면 해석을 통해 구한 강도와 변형은 실험값과 대체로 일치하였다. 특히, 개폐거동에 의한 변형이 가장 큰 비율을 차지하였다.

• Computers and Concrete
• /
• 제33권3호
• /
• pp.251-264
• /
• 2024

The present study pertains to the effects of variations in the location and size of drilled web openings on the behavior of fixed-fixed reinforced concrete (RC) beams. For this purpose, a reference bending beam with a transverse opening in each half span was tested to failure. Later, the same beam was modeled and analyzed with the help of finite element software using ABAQUS. Upon achieving close agreement between the experimental and numerical results, the location and size of the web opening were altered to uncover the effects of these factors on the shear strength and load-deflection behavior of RC beams. The experimental failure mode of the tested beam and the numerical results were also verified by theoretical calculations. In numerical analysis, when compared to the reference (D0) specimen, if the distance of the opening center from the support is 0 or h or 2h, reduction in load-bearing capacity of 1.5%-22.8% or 2.0%-11.3% or is 4.1%-40.7%. In other words, both the numerical analyses and theoretical calculations indicated that the beam behavior shifted from shear-controlled to flexure-controlled as the openings approached the supports. Furthermore, the deformation capacities, energy absorption values, and the ductilities of the beams with different opening diameters also increased with the decreasing distance of the opening from supports. Web compression failure was shown to be the predominant mode of failure of beams with large diameters due to the lack of sufficient material in the diagonal compression strut of the beam. The present study indicated that transverse openings with diameters, not exceeding about 1/3 of the entire beam depth, do not cause the premature shear failure of RC beams. Finally, shear damage should be prevented by placing special reinforcements in the areas where such gaps are opened.