• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.609-614
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• 2001

This paper is to explain reasonable shear behavior that can apply usually to reinforced concrete beams on the basic concepts of existent analysis and experimental research information. This study is succession $paper^{2) 3) 4) 5)}$ of treatise announced in existing and main control variable of reinforced concrete beams with stirrups used internal force state factor($\alpha$). Shear failure of reinforced concrete beams with stirrups is Influenced greatly because of the actual geometrical shape(a/d) of the concrete and flexural reinforcement steel ratio, stirrup reinforcement ratio and concrete compression strength, size effect etc. Therefore, shear behavior of reinforced concrete beams with stirrups that flexural crack is happened can be explained easily through proper extent proposal of internal force state factor($\alpha$) that express internal force state flowing. Use existent variable truss model by analysis model to explain arch action. Also, wish to compose each failure factors and correlation with internal force state factor by function, and when diagonal cracks happens, internal force state factor($\alpha$) study whether shear stress and some effect are.

• Journal of the Korean Society of Safety
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• v.13 no.4
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• pp.292-299
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• 1998

In this study, the size effect in flexural and shear behaviors of reinforced concrete beams with stirrup has been studied. The specimens of different size with same longitudinal reinforcement ratio are tested. The major variables of test include the size(relative depth) of the members as well as the longitudinal reinforcement ratios. The nominal resistances in flexure and shear are obtained for various sizes and steel ratios. It is found from the present study that the size effect is also very pronounced for the flexural resistance in reinforced concrete structures. The prediction formulas for the size effect of reinforced concrete beams in flexure and shear are proposed. The proposed equations agree relatively well with experimental data. The present study will provide useful bases for more accurate analysis and design of reinforced concrete structures.

• International Journal of Concrete Structures and Materials
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• v.3 no.1
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• pp.39-45
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• 2009

The purpose of this study is to establish flexural behavior of high-strength concrete beams confined in the pure bending zone with stirrups. The experiment was carried out on full-scale high-strength reinforced concrete beams, of which the compressive strengths were 40 MPa and 70 MPa. The beams were confined with rectangular closed stirrups. Test results are reviewed in terms of flexural capacity and ductility. The effect of web reinforcement ratio, longitudinal reinforcement ratio and shear span to beam depth ratio on ductility are investigated. The analytic method is based on finite element method using fiber-section model, which is known to define the behavior of reinforced concrete structures well up to the ultimate state and is proven to be valid by the verification with the experimental results above. It is found that confinement of concrete compressive regions with closed stirrups does not affect the flexural strength but results in a significantly increased ductility. Moreover, the ductility tends to increase as the quantity of stirrups increases by reducing the spacing of stirrups.

• Coupled systems mechanics
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• v.3 no.2
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• pp.195-211
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• 2014

When strong seismic forces act on reinforced concrete structures, their beam-column connections are very susceptible to damage during the earthquake event. The aim of this numerical work is to evaluate the influence of the internal steel reinforcement array on the nonlinear response of a RC beam-column connection when it is subjected to strong cyclic loading -as a seismic load. For this, two specimens (extracted from an experimental test of 12 RC beam-column connections reported in literature) were modeled in the Finite Element code FEAP considering different stirrup's arrays. In order to evaluate the nonlinear response of the RC beam-column connection, the 2D model takes into account the nonlinear thermodynamic behavior of each component: for concrete, a damage model is used; for steel reinforcement, it is adopted a classical plasticity model; in the case of the steel-concrete bonding, this one is considered perfect without degradation. At the end, we show a comparison between the experimental test's responses and the numerical results, which includes the distribution of shear stresses and damage inside the concrete core of the beam-column connection; in the other hand, the effects on the connection of a low and high state of confinement are analyzed for all cases.

• Journal of the Korean Recycled Construction Resources Institute
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• v.1 no.2
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• pp.128-135
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• 2013

In this study, one-way shear tests were performed to investigate the shear capacity of amorphous steel fiber-reinforced concrete slabs. Primary test parameters were the shear reinforcing method(Stirrups or amorphous steel fibers) and shear reinforcement ratio(0.25 and 0.5%). A series of four one-way slab specimens including a specimen without shear reinforcement and three specimens with shear reinforcements(stirrup, 0.25%, and 0.5% amorphous steel fibers) were tested. The test results showed that 0.25% amorphous steel fibers improved the shear capacity, but 0.5% amorphous steel fibers did not improve the shear capacity compared to the specimen with conventional shear reinforcement of 0.25%. Additional study is needed to understand the variation of shear capacity according to fiber volume fraction.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.1
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• pp.259-269
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• 2005

This paper describes the application of genetic algorithm for the discrete optimum design of reinforced concrete continuous beams. The objective is to minimize the total cost of reinforced concrete beams including the costs of concrete, form work, main reinforcement and stirrup. The flexural and shear strength, deflection, crack, spacing of reinforcement, concrete cover, upper-lower bounds on main reinforcement, beam width-depth ratio and anchorage for main reinforcement are considered as the constraints. The width and effective depth of beam and steel area are taken as design variables, and those are selected among the discrete design space which is composed with dimensions and steel area being used from in practice. Optimum result obtained from GA is compared with other literature to verify the validity of GA. To show the applicability and efficiency of GA, it is applied to three and five span reinforced concrete beams satisfying with the Korean standard specifications.

• Steel and Composite Structures
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• v.34 no.1
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• pp.17-34
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• 2020

This paper investigates the flexural behavior of concrete beams reinforced longitudinally with either steel bars, molded glass-fiber reinforced polymer (GFRP) grating mesh or pultruded glass-fiber reinforced polymer (GFRP) grating mesh, under four-point bending. The variables included in this study were the type of concrete (normal weight concrete, perlite concrete and vermiculite concrete), type of the longitudinal reinforcement (steel bars, molded and pultruded GFRP grating mesh) and the longitudinal reinforcement ratio (between 0.007 and 0.035). The influences of these variables on the load-midspan deflection curves, bending stiffness, energy absorption and failure modes were investigated. A total of fifteen beams with a cross-sectional dimension of 160 mm × 210 mm and an overall length of 2400 mm were cast and divided into three groups. The first group was constructed with normal weight concrete and served as a reference concrete. The second and third groups were constructed with perlite concrete and vermiculite concrete, respectively. An innovative type of stirrup was used as shear reinforcement for all beams. The results showed that the ultimate load of the beams reinforced with pultruded GFRP grating mesh ranged between 19% and 38% higher than the ultimate load of the beams reinforced with steel bars. The bending stiffness of all beams was influenced by the longitudinal reinforcement ratio rather than the type of concrete. Failure occurred within the pure bending region which means that the innovative stirrups showed a significant resistance to shear failure. Good agreement between the experimental and the analytical ultimate load was obtained.

• Journal of Korean Association for Spatial Structures
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• v.23 no.2
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• pp.29-36
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• 2023

Reinforcement learning (RL) is widely applied to various engineering fields. Especially, RL has shown successful performance for control problems, such as vehicles, robotics, and active structural control system. However, little research on application of RL to optimal structural design has conducted to date. In this study, the possibility of application of RL to structural design of reinforced concrete (RC) beam was investigated. The example of RC beam structural design problem introduced in previous study was used for comparative study. Deep q-network (DQN) is a famous RL algorithm presenting good performance in the discrete action space and thus it was used in this study. The action of DQN agent is required to represent design variables of RC beam. However, the number of design variables of RC beam is too many to represent by the action of conventional DQN. To solve this problem, multi-agent DQN was used in this study. For more effective reinforcement learning process, DDQN (Double Q-Learning) that is an advanced version of a conventional DQN was employed. The multi-agent of DDQN was trained for optimal structural design of RC beam to satisfy American Concrete Institute (318) without any hand-labeled dataset. Five agents of DDQN provides actions for beam with, beam depth, main rebar size, number of main rebar, and shear stirrup size, respectively. Five agents of DDQN were trained for 10,000 episodes and the performance of the multi-agent of DDQN was evaluated with 100 test design cases. This study shows that the multi-agent DDQN algorithm can provide successfully structural design results of RC beam.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.349-354
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• 2000

While a little research has been performed on flexural behavior of reinforced polymer concrete (RPC) beams with the compressive strength lower than 1000kg/$\textrm{cm}^2$, vary little exists in conjunction with the behavior of (RPC) 1,400kg/$\textrm{cm}^2$ or compressive strength. In this paper the flexural behavior of high strength polymer concrete beams with 1,400kg/$\textrm{cm}^2$ in compressive was evaluated. The unsaturated polyester resin was used to make polymer concrete as binder. The beams with stirrup singly/doubly were rested to examine the effect of tensile reinforcement ratio. As test results. steel ratio increased with the increased moment strength, decreased with ultimate deflection.

• Structural Engineering and Mechanics
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• v.37 no.2
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• pp.163-175
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• 2011

The results of experimental and numerical investigations on reinforced concrete beams, with different longitudinal rebars affected by corrosive processes are presented in this paper. Different diameters and/or different distributions of longitudinal rebars were employed keeping constant the total section in each analyzed case, (maintaining a constant stirrup diameter and distribution). The rebars were subjected to accelerated corrosion in the experimental study. Electrochemical monitoring of the process, periodic measuring of the cover cracking and gravimetry of the rebars were performed through the test. Some building recommendations are obtained in order to be considered by designers of concrete structures. The numerical simulation was carried out through the application of the Finite Element Method (FEM), employing plane models, and using linear-elastic material model. The cracking process was associated with the evolution of the tensile stresses that were originated. This numerical methodology allows the monitoring of the mechanical behavior until the beginning of the cracking.