• Journal of the Korea Concrete Institute
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• v.11 no.5
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• pp.79-88
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• 1999

The purpose of this paper is to develop a mathematical expression for computing crack angles based on reinforcement volumes in the longitudinal and transverse directions, member end-fixity and length-to-width aspect ratio. For this a reinforced concrete beam-column element is assumed to possess a series of potential crack planes represented by a number of differential truss elements. Depending on the boundary condition, a constant angle truss or a variable angle truss is employed to model the cracked structural concrete member. The truss models are then analyzed using the virtual work method of analysis to relate forces and deformations. Rigorous and simplified solution schemes are presented. An equation to estimate the theoretical crack angle is derived by considering the energy minimization on the virtual work done over both the shear and flexural components the energy minimization on the virtual work done over both the shear and flexural components of truss models. The crack angle in this study is defined as the steepest one among fan-shaped angles measured from the longitudinal axis of the member to the diagonal crack. The theoretical crack angle predictions are validated against experimentally observed crack angle reported by previous researchers in the literature. Good agreement between theory and experiment is obtained.

• Structural Engineering and Mechanics
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• v.41 no.4
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• pp.459-477
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• 2012

This paper attempts to determine the inclination of the compression strut within variable angle truss models for RC beams loaded in shear-flexure through a proposed semi-analytical approach. A truss unit is used to analyze a reinforced concrete beam, by the principle of virtual work under the truss analogy. The inclination of the compression strut is then theoretically derived. The concrete contribution is addressed by utilizing the compatibility condition within each truss unit. Comparisons are made between the predicted and published experimental results of the seventy one RC beams with respect to the shear strength and the inclined angle of the compression strut at this state to investigate the adequacy of the proposed semi-analytical approach.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.3
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• pp.213-220
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• 2005

Recently, a concern to verify the displacement capacity of shear wall has been arised to produce suitable data for the performance based design. In this paper, a process is presented to evaluate the displacement capacity of shear wall. The displacement of shear wall is expressed as the superposition of shear and flexural deformation. Variable crack angle truss model with a modification and sectional analysis method are used in calculating shear and flexural displacement, respectively. In addition, the effect of axial force and the contribution of vertical and horizontal reinforcements in wall are considered in the analysis. The accuracy of proposed method is evaluated by the comparison calculation results with previous test results. From the comparison, it was shown that the hysteretic behavior of shear wall could be well predicted by using the process. In the case with flange wall, however, the method overestimates the contribution of flange wall for strength and stiffness and underestimates for displacement capacity.

• Computers and Concrete
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• v.16 no.1
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• pp.67-97
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• 2015

This article presents a computing procedure developed to predict the torsional strength of axially restrained reinforced concrete beams. This computing procedure is based on a modification of the Variable Angle Truss Model 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 elements. Theoretical predictions from the proposed model are compared with some experimental results available in the literature and also with some numerical results from a three-dimensional nonlinear finite element analysis. It is shown that the proposed computing procedure gives reliable predictions for the ultimate behaviour, namely the torsional strength, of axially restrained reinforced concrete beams under torsion.

• Proceedings of the Korea Concrete Institute Conference
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• 1991.10a
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• pp.51-58
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• 1991

In staically indeterminate structures torsional stiffness is an important factor for prediction of mechanical behavior at all loading stages in reinfored concrete beams, which also for calculation of torsional moment. This paper proposes equation for postcracking torsional stiffness of reinforced concrete beams under pure torsion, which is derived considering the equilibrium and compatibility condition for shear panel based on the variable angle space truss model. The equation describes well the effect according to the variation of aspect ratio and steel volume ratio per unit concrete volume. It agress with experimental results in this paper as well as available literature.

• Structural Engineering and Mechanics
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• v.73 no.5
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• pp.515-527
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• 2020

This paper presents a stress field approach for the shear capacity of stirrup-reinforced concrete beams that explicitly incorporates the contribution of principal tensile stresses in concrete. This formulation represents an extension of the variable strut inclination method adopted in the Eurocode 2. In this model, the stress fields in web concrete consist of principal compressive stresses inclined at an angle θ combined with principal tensile stresses oriented along a direction orthogonal to the former (the latter being typically neglected in other formulations). Three different failure mechanisms are identified, from which the strut inclination angle and the corresponding shear strength are determined through equilibrium principles and the static theorem of limit analysis, similar to the EC-2 approach. It is demonstrated that incorporating the contribution of principal tensile stresses of concrete slightly increases the ultimate inclination angle of the compression struts as well as the shear capacity of reinforced concrete beams. The proposed stress field approach improves the prediction of the shear strength in comparison with the Eurocode 2 model, in terms of both accuracy (mean) and precision (CoV), as demonstrated by a broad comparison with more than 200 published experimental results from the literature.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2A
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• pp.187-196
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• 2008

The punching shear strength of RC slabs is estimated analytically by the simple truss model. To avoid intrinsic difficulties in punching shear analysis of reinforced concrete slabs, the slabs were divided into three sub-structures as the punching cone and the remaining parts. The strength of the punching cone was evaluated by the stiffness of inclined strut. The stiffness of springs which control lateral displacement of the roller supports consists of the steel reinforcement which passed through the punching cone. Initial angle of struts was determined by curve fitting method of the experimental data with variable reinforcement ratio in order to compensate for uncertainties in the slab's punching shear, the simplification errors and the stiffness of the remaining sub-structures. The validity of computed punching shear strength by simple truss model was shown by comparing with experimental results. The punching shear strength, which was determined by snap-through critical load of shallow truss, can be used effectively to examine punching shear strength of RC slabs.

• Structural Engineering and Mechanics
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• v.55 no.1
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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.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.638-644
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• 2019

In this study, the fluid flow and heat transfer characteristics within sandwich panels are investigated using computational fluid dynamics. Within the sandwich panels having periodic cellular cores, air can freely move inside the core section so that the structure is able to perform multi-functional roles such as simultaneous load bearing and heat dissipation. Thus, there needs to examine the thermal and flow analysis with respect to design variables and various conditions. In this regard, ANSYS Fluent was utilized to explore the flow and heat transfer within the pyramidal truss sandwich structures by varying the truss angle and inlet velocity. Without the entry effect in the first unitcell, the constant rate of pressure and the constant rate of Nusselt number was observed. As a result, it was demonstrated that Nusselt number increases and friction factor decreases as the inlet velocity increases. Moreover, the rate of Nusselt number and friction factor was appreciable in the range of V=1-5m/s due to the transition from laminar to turbulent flow. Regarding the effect of design variable, the variation of truss angle did not significantly influence the characteristics.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.185-190
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• 2002

Recently, a concern to verify the displacement capacity of shear wall has been arised to produce suitable data for the performance based design. In this paper, a process is presented In evaluate the displacement capacity of shear wall. The displacement of shear wall is expressed as the superpositopn of shear and flexural deformation. Variable crack angle truss model with a modification and existing analysis program(XTRACT) are used in calculating shear and flexural displacement, respectively. The accuracy of proposed method is evaluated by the comparison calculation results with previous test results. From the comparison, it was shown that the displacement capacity of shear wall could be well predicted by using the process.