• 대한토목학회논문집
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• 제8권4호
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• pp.1-9
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• 1988

전보(前報)에서는 전하중단계(全荷重段階)에서 RC비틀림 부재(部材)의 하중이력곡선(荷重履歷曲線)을 이론적으로 추정하는데 목적을 두었다. 본(本) 논문(論文)은 전보(前報)에 연속되는 연구로서 비틀림실험(實驗) 내용(內容)을 상세히 소개하는 동시에 RC 비틀림부재(部材)의 벽(壁)두께 및 철근비(鐵筋比)가 비틀림강도(強度)에 미치는 영향을 비롯하여, 그의 균열특성에 대해서도 실험결과에 바탕을 두어 비교(比較) 고찰(考察)하는 데 목적을 둔다.

• Structural Engineering and Mechanics
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• 제68권4호
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• pp.443-457
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• 2018

In this article, a comparative study has been made to investigate the scattering behaviour of three layered structure model on torsional surface wave. For such model intermediate layer is taken as fiber reinforced composite, resting over a dry sandy Gibson substratum and underlying by different anelastic media. We consider two distinct mediums for topmost layer. In the first case, topmost layer has been taken as fluid saturated homogeneous porous layer, while in the second case the fluid saturated porous layer has been replaced by a transversely isotropic layer. Simple form expression for the secular equation of torsional surface wave has been worked out in both the cases by executing specific boundary conditions, which comprises Whittaker's function and its derivative, for imminent result that have been elaborated asymptotically. Some special cases have been constituted which are in excellent compliance with recorded literatures. For the sake of comparative study, numerical estimation and graphical illustration have been accomplished to identify the effects of the width ratio of the layers, Biot's gravity parameter, sandy parameter, porosity parameter and other heterogeneity parameters corresponding to the layers and half spaces, horizontal compressive and tensile initial stress on the phase velocity of torsional surface wave.

• Computers and Concrete
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• 제32권2호
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• pp.173-184
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• 2023

In this study, mechanical, flexural post-cracking, and torsional behaviors of recycled steel fiber-reinforced concrete (RSFRC) incorporating steel fibers obtained from recycling of waste tires were investigated. Initially, three concrete mixes with different fiber contents (0, 40, and 80 kg/m³) were designed and tested in fresh and hardened states. Subsequently, the flexural post-cracking behaviors of RSFRCs were assessed by conducting three-point bending tests on notched beams. It was observed that recycled steel fibers improve the post-cracking flexural behavior in terms of energy absorption, ductility, and residual flexural strength. What's more, torsional behaviors of four RSFRC concrete beams with varying reinforcement configurations were investigated. The results indicated that RSFRCs exhibited an improved post-elastic torsional behaviors, both in terms of the torsional capacity and ductility of the beams. Additionally, numerical analyses were performed to capture the behaviors of RSFRCs in flexure and torsion. At first, inverse analyses were carried out on the results of the three-point bending tests to determine the tensile functions of RSFRC specimens. Additionally, the applicability of the obtained RSFRC tensile functions was verified by comparing the results of the conducted experiments to their numerical counterparts. Finally, it is noteworthy that, despite the scatter (i.e., non-uniqueness) in the aspect ratio of recycled steel fiber (as opposed to industrial steel fiber), their inclusion contributed to the improvement of post-cracking flexural and torsional capacities.

• 콘크리트학회논문집
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• 제14권6호
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• pp.1010-1021
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• 2002

1995년에 개정된 현행 ACI 규준식은 콘크리트의 비틀림 저항을 무시하여, 콘크리트와 비틀림 보강근이 비틀림 내력에 미치는 상호영향을 평가할 수 없다. 실험에서는 현행 ACI 규준식이 콘크리트와 비틀림 보강근의 차이에 따라 철근콘크리트 보의 비틀림 내력을 과소/과대 평가하고 있음을 지적하였다. 이 논문에서는 트러스 모델의 힘의 평형조건과 변형의 적합조건을 이용하여 콘크리트의 비틀림 저항을 고려한 비틀림 평가식을 제안하였다. 제안식에서는 현행 규준식의 상수 '2'대신에 $textsc{k}$를 사용하여 비틀림 모멘트에 대한 콘크리트와 비틀림 보강근의 상호영향을 고려하였다. 제안식은 순수비틀림을 받는 총 66개의 철근콘크리트 보의 실험결과와 비교되었다. 제안식은 콘크리트의 압축강도와 비틀림 보강근의 양의 변화에 관계없이 현행 ACI 비틀림 규준식보다 정확하게 실제의 비틀림 모멘트를 예측하였으며, 이 때의 평균값 및 변동계수는 각각 1.1 및 8.5%였다.

• Structural Engineering and Mechanics
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• 제61권3호
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• pp.397-406
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• 2017

The use of fiber reinforced polymer (FRP) for torsional strengthening of reinforced concrete (RC) single cell box beams has been analyzed considerably by researchers worldwide. However, little attention has been paid to torsional strengthening of multicell box girders in terms of both experimental and numerical research. This paper reports the experimental work in an overall investigation for torsional strengthening of multicell box section RC girders with externally-bonded Carbon Fiber Reinforced Polymer CFRP strips. Numerical work was carried out using non-linear finite element modeling (FEM). Good agreement in terms of torque-twist behavior, steel and CFRP reinforcement responses, and crack patterns was achieved. The unique failure modes of all the specimens were modeled correctly as well.

• Structural Engineering and Mechanics
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• 제55권1호
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• pp.1-27
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• 2015

This article presents a theoretical parametric analysis on the ultimate torsional behaviour of axially restrained reinforced concrete (RC) beams. This analysis is performed by using a computing procedure based on a modification of the Variable Angle Truss Model. This computing procedure was previously developed to account for the influence of the longitudinal compressive stress state due to the axial restraint conditions provided by the connections of the beams to other structural members. The presented parametric study aims to check the influence of some important variable studies, namely: torsional reinforcement ratio, compressive concrete strength and axial restraint level. From the results of this parametric study, nonlinear regression analyses are performed and some design charts are proposed. Such charts allow to correct the resistance torque of RC beams (rectangular sections with small height to width ratios) to account for the favorable influence of the axial restraint.

• 대한토목학회논문집
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• 제41권3호
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• pp.201-208
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• 2021

본 논문에서는 하부수평브레이싱 설치에 따른 무도상 철도판형교의 횡방향 및 비틀림거동에 관한 영향을 검토하였다. 우선 하부브레이싱의 부재 배치 형태가 다른 해석모델을 대상으로 하여 열차하중에 의한 횡방향변위를 비교 검토하여 가장 효율적인 하부 브레이싱의 배치에 대하여 검토하였다. 다음으로는 하부브레이싱을 설치한 2주형 철도판형교의 비틀림거동에 대해 검토를 수행하였다. 또한, FEM 해석결과로부터 구한 비틀림상수와 상부와 하부수평브레이싱을 등가두께로 치환하여 폐합단면으로 하는 철도판형교의 비틀림상수를 비교하였고, 교량의 지간길이와 하부브레이싱의 단면적의 영향을 검토하였다. 이와같은 해석결과를 기초로 본 연구에서는 횡좌굴모멘트와 비틀림상수비와의 관계곡선을 제시하였고 비틀림보강이 필요한 철도판형교의 범위를 제안하였다.

• Computers and Concrete
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• 제11권5호
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• pp.399-410
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• 2013

A nonlinear finite element analysis of R/C hybrid deep T-beam with web opening subjected to pure torsion is presented. Hexahedral 8-nodes and space truss element were used for modeling concrete and reinforcement. The reinforcement was assumed perfectly bonded to the corresponding nodes of the concrete element. The constitutive relations for concrete and reinforcement are based on the modified field theory and elastic perfectly plastic. The smear crack approach was adopted for modeling the crack. The torque-twist angle relationship curve based on the finite element analysis was compared to the experimental results. The comparison shows that the curve of torque-twist angle predicted by the nonlinear finite element analysis is linear before cracking and close to the experimental result. After cracking, the curve becomes nonlinear and stiffer compared to the experimental result.

• Computers and Concrete
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• 제14권1호
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• pp.1-18
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• 2014

The addition of steel fibers in concrete mixture is recognized as a non-conventional mass reinforcement scheme that improves the torsional, flexural, and shear behavior of structural members. However, the analysis of fiber reinforced concrete beams under combined torsion, bending, and shear is limited because of the complicated nature of the problem. Therefore, nonlinear 3D finite element analysis was conducted using the "ANSYS CivilFEM" program to investigate the behavior of fiber reinforced concrete L-beams. These beams were tested at different reinforcement schemes and loading conditions. The reinforcement case parameters were set as follows: reinforced with longitudinal reinforcement only and reinforced with steel bars and stirrups. All beams were tested under two different combined loading conditions, namely, torsion-to-shear ratio (T/V) = 545 mm (high eccentricity) and T/V = 145 mm (low eccentricity). Eight intermediate L-beams were constructed and tested in a laboratory under combined torsion, bending, and shear to validate the finite element model. Comparisons with the experimental data reveal that the program can accurately predict the behavior of L-beams under different reinforcement cases and combined loading ratios. The ANSYS model accurately predicted the loads and deformations for various types of reinforcements in L-beams and captured the concrete strains of these beams.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.409-412
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• 2003

ACI design code is not capable of evaluating the inter-effects between concrete and torsional reinforcement on the torsional resistance of the reinforced concrete beams. In this study, the failure strengths of the ten reinforced concrete beams subjected to pure torsion were evaluated using 3-dimensional strut-tie models. The analysis results obtained from the present study were compared with those obtained from the ACI design code. The comparison showed that the accuracy and performance of the present method were better than the ACI design code. Thus, the method implementing a 3-dimensional strut-tie model can be possibly applied to the analysis and design of the reinforced concrete beams subjected to pure torsion as a rational design method.