• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.2
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• pp.157-165
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• 2002

Nonlinear analysis of the reinforced concrete beam subjected to torsion is presented. Seventeen equations involving seventeen variables are derived from the equilibrium equation, compatibility equation, and the material constitutive laws to solve the torsion problem. Newton method was used to solve the nonlinear simultaneous equations and efficient algorithms are proposed. Present model covers the behavior of reinforced concrete beam under pure torsion from service load range to ultimate stage. Tensile resistance of concrete after cracking is appropriately considered. The softened concrete truss model and the average stress-strain relations of concrete and steel are used. To verify the validity of present model, the nominal torsional moment strengths according to ACI-99 code and the ultimate torsional moment by present model are compared to experimental torsional strengths of 55 test specimens found in literature. The ultimate torsional moment strengths by the present model show good results.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.1103-1108
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• 2001

ACI 318-99 predicts the torsional moment of reinforced concrete members by assuming that the angle of diagonal compressive concrete is equal to 45 degree. However, this angle depends on the difference of longitudinal and transverse steel ratios. This paper compares the torsional moments calculated by ACI 318-99 code and a truss model considering compatibility of strains. The comparison indicated that the torsion equation in ACI code underestimated the real torsional moment of reinforced concrete beam in which the ratio of longitudinal reinforcement was larger than that of transverse reinforcement.

• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.1010-1021
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• 2002

The current ACI design code does not take into account the contribution of concrete for the torsional moment of reinforced concrete(RC) beams subjected to pure torsion. This code is not capable of evaluating the inter-effects between concrete and torsional reinforcement on the torsional resistance of the RC beams. Some test results indicated that the current ACI code was not successful in predicting the observed torsional moment of the RC beams with reasonable accuracy. The research reported in this paper provides an evaluation equation to predict the torsional moment of the RC beams subjected to pure torsion. The proposed equation is derived from the equilibrium as well as compatibility equations of the truss model for the cracked RC beams. Comparisons between the observed and calculated torsional moments of the 66 tested beams, showed reasonable agreement.

• Structural Engineering and Mechanics
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• v.87 no.6
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• pp.541-554
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• 2023

An unbraced cantilever beam subjected to loads which cause bending about the major axis may buckle in a flexuraltorsional mode by deflecting laterally and twisting. For the efficient design of these structures, design engineers require a simple accurate equation for the elastic flexural-torsional buckling load. Existing solutions for the flexural-torsional buckling of cantilever beams have mainly been derived by numerical methods which are tedious to implement. In this research, an attempt is made to derive a theoretical equation by the energy method using different buckled shapes. However, the results of a finite element flexural-torsional buckling analysis reveal that the buckled shapes for the lateral deflection and twist rotation are different for cantilever beams. In particular, the buckled shape for the twist rotation also varies with the section size. In light of these findings, the finite element flexural-torsional buckling analysis was then used to derive simple accurate equations for the elastic buckling load and moment for cantilever beams subjected to end point load, uniformly distributed load and end moment. The results are compared with previous research and it was found that the equations derived in this study are accurate and simple to use.

• Wind and Structures
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• v.3 no.4
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• pp.279-289
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• 2000

The main purpose of this paper is to demonstrate the necessity of considering wind load combinations even for low-rise buildings. It first discusses the overall quasi-static wind load effects and their combinations to be considered in structural design of low-rise buildings. It was found that the maximum torsional moment closely correlates with the maximum along-wind base shear. It was also found that the instantaneous pressure distribution causing the maximum along-wind base shear was quite similar to that causing the maximum torsional moment, and that this asymmetric pressure pattern simultaneously accompanies considerable across-wind and torsional components. Secondly, the actual wind pressure distributions causing maximum quasi-static internal forces in the structural frames are conditionally sampled and their typical pressure patterns are presented.

• Computers and Concrete
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• v.29 no.5
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• pp.285-301
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• 2022

This study aims at developing a torsional strength model based on a nonlinear analysis method presented in the previous studies. To this end, flexural neutral axis depth of a reinforced concrete section and effective thickness of an idealized thin-walled tube were formulated based on reasonable approximations. In addition, various sectional force components, such as shear, flexure, axial compression, and torsional moment, were considered in estimating torsional strength by addressing a simple and linear strain profile. Existing test results were collected from literature for verifications by comparing with those estimated from the proposed model. On this basis, it can be confirmed that the proposed model can evaluate the torsional strength of RC members subjected to combined loads with a good level of accuracy, and it also well captured inter-related mechanisms between shear, bending moment, axial compression, and torsion.

• Journal of Korean Society of Steel Construction
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• v.29 no.5
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• pp.361-368
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• 2017

ASCE 7-10 defines the torsional irregular structure as the one that has large torsional responses caused by the eccentricity. The code requires that these structures should be designed abide by the torsional provisions. This study evaluates the influence of torsional provisions on the performance of the designed multiple steel moment frames with different eccentricity. In this study, 3D response history analyses are performed. The results show that the moment frame design according to the standard with torsional irregularity provisions showed larger performance as the eccentricity increased and the distribution of plastic hinges similarly to orthopedic structures.

• Journal of the korean Society of Automotive Engineers
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• v.4 no.1
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• pp.20-30
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• 1982

Recent diesel engine has achieved high speed running comparable to that of gasoline engine as a speed improvement effort. Consequently, torsional vibration of high-speed diesel engine induced vibration nosise, reduced horsepower and the like. Viscous damper which is thought to be effective in curtailing the torsional vibration was studied over a wide range of speed. In this investigation, a water cooling, 4-cycle high-speed diesel engine(Msx. 3500 rpm)was used for the study. Theoretical analysis was made by assuming the engine to be an ideal equivalent system(length, moment of inertia) i. e. the multi-degree of freedom equivalent torsional vibration system with damper was analyzed. In the analysis, the inertia moment of suitable damper for this experiment was calculated by varying the relative damping coefficient of damper of engine for each damper. Furthermore, in the torsional vibration experiment, the torsional vibration amplitude of the crankshaft system was measured when the engine was equipped with dampers of different moments of inertia and also when the engine was equipped without dampers. The experimental results were compared with the analytical values and were found to be satisfied. The results of this investigation are summarized below; (1) It was found that for the engine equipped with dampers, the torsional vibration amplitude was reduced to about one third of those without dampers. (2) The optimum value of inertia moment of viscous damper for the engine was found to be about Id=1.05(kg.cm.s$^{2}$) (3) The optimum damping coefficient and the ratio of moment of inertia for the engine were found to be about Ca= 850(kg.cm.s), Rd=0.509, respectively (b1 dapmper).

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.437-440
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• 2007

Design equations for calculating the lateral-torsional buckling moment resistances of I-section beams with continuous lateral top-flange bracing subjected to several loading conditions are investigated based on elastic finite-element analyses. The equations presented in this study are compared with current moment gradient modifiers presented by other researchers and specifications. The equation suggested in the SSRC Guides(1998) has a good agreement with the results of finite-element analyses. The moment gradient correction factors proposed in the SSRC Guides(1998) should be easily used to calculate the lateral-torsional buckling moment resistance of I-beams with continuous lateral top-flange bracing.

• Structural Engineering and Mechanics
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• v.18 no.6
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• pp.745-757
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• 2004

Lateral-torsional buckling moment resistances of I-shaped stepped beams with continuous lateral top-flange bracing under a single point load on the top flange and negative end moments were investigated. Stepped beam factors and a moment gradient correction factor suggested by Park et al. (2003, 2004) were used to develop new lateral buckling formula for beam designs. From the investigation of finite element analysis (FEA), new lateral buckling formula of beams with singly or doubly stepped member changes and with continuous lateral top-flange bracing subjected to a single point load on top flange and end moments were developed. The new design equation includes the length-to-height ratio factor to account for the increase of lateral-torsional buckling moment resistance as the increase of length-to-height ratio of stepped beams. The calculation examples for obtaining lateral-torsional buckling moment resistance using the new design equation indicate that engineers should easily determine the buckling capacity of the stepped beams.