The reinforced concrete structures built decades ago are vulnerable because they respond to the level of knowledge, computational progress and quality of the materials of that time. These buildings exist in large cities, so it is urgent to verify the performance of these structures against seismic events (Aguiar, 2016) (Mouzzoun et al., 2013).
The comparative analysis was applied to a 10-story reinforced concrete porticoed building with a basement. It is a type 2 unsymmetric-plan building with excessive inward corners, making it susceptible to torsional flexibility, and it has a type 3 irregularity in elevation with vertical geometric irregularity.
Reinforced Concrete Structures Park And Paulay Pdf 19
The paper presents numerical findings of reinforced concrete interior beam-column joints under monotonic antisymmetrical load. The finite element models considered compression and tension damage were calibrated by test results in terms of the load-displacement, failure modes, and strains of longitudinal steel. The emphasis was put on studying the effects of hoop reinforcement ratio in joint core and the axial compression ratio on the responses of the joints. The results show that, in addition to the truss and strut-and-tie mechanisms, the confinement mechanism also existed in the joint core. A certain amount of stirrup is not only able to enhance the confinement in joint core, undertake a part of shear force and thus to increase the shear capacity, prevent the outward buckling of steel bars in column, improve the stress distribution in joint core, delay cracking and restrain the propagation of cracks, but also to increase the yield load, decrease the yield displacement of beam and improve the joint ductility. However, excessive horizontal stirrups contribute little to the joint performance. In a certain range, larger axial compression ratio is beneficial for the joint mechanical behavior, while it is negative when axial compression ratio is too large.
Generally, in reinforced concrete beams, shear reinforcing bars such as stirrups are used as shear reinforcements to prevent brittle failure and induce flexural behavior. Shear reinforcement transfers stress between shear cracks to prevent the shear failure of concrete and to give it greater strength and ductility. However, in the case of the existing shear reinforcement details such as stirrups, the construction process is complicated by segmented details. Previous studies have been conducted on various existing segmented shear reinforcements.
Choi et al. [3] evaluated the shear reinforcement performance of fiber-reinforced polymer (FRP) plates. Their testing confirmed that the shear strength of the reinforced concrete beam with the FRP plates was improved, and that the shear reinforcement effect was greater when the shear reinforcement was attached perpendicularly to the crack angle. Lee et al. [4] experimented with shear-reinforced beams with slit-type steel plates attached to the beam surface. Their paper reported that with the vertical slit steel plate retrofit, the shear strength greatly depended on the increase in the thickness of the steel plate and a larger attachment area between the steel plate and the concrete. They also confirmed that the slit-type steel plate with a 45-degree inclination was more effective. Although the maximum strength did not change as the attachment area changed, the shear stiffness changed as the concrete crushing point changed. Sharif et al. [5] studied shear reinforcement by attaching steel plates and U-strips to the surface of reinforced concrete beams, and proposed design equations for this. They reported that the steel plate and the U-strip were effective in enhancing shear strength and could improve ductility. F. Qin et al. [6] conducted an experimental study on the shear strength of a new shear reinforcement by welding a cross-tie between the upper and lower steel plates. The experimental results were compared with the design shear strength presented by ACI 318 [7] and Modelcode 2010 [8], and a design method was proposed to design the developed shear reinforcement. C. Bywalski et al. [9] conducted an experimental study on the shear strength of reinforced concrete beams reinforced with a glass-fiber-reinforced polymer (GFRP) reinforcement, and compared and evaluated the performance according to GFRP details. K. Pilakoutas et al. [10] used the inclined shear reinforcement as an alternative detail of the shear reinforcement for the flat slab. At this time, the adhesion performance was increased by digging a groove in the shear reinforcement, and the effect of enhancing the shear strength was confirmed.
It was necessary to shorten the construction period and improve the workability by omitting the reinforcement process of the existing stirrup at the construction site of the reinforced concrete structure. In addition, it should be usable for general reinforced concrete members. To this end, an integrated shear reinforcement that can be manufactured in a factory has been proposed, and it is necessary to evaluate the structural safety of the new shear reinforcement and to review the applicability of the current design standards. These were manufactured using steel plates and rebar bent in N shapes (N-type rebar) instead of stirrups. The shapes of the N-type rebar and the steel plate shear reinforcements are shown in Figure 1.
The BS-0 specimen was not shear-reinforced; it was designed to evaluate only the shear strength of the concrete and the longitudinal reinforcing bars. As a result of the test, the BS-0 specimen exhibited a typical shear fracture behavior in which the first shear crack occurred at 286 kN, the crack expanded, and the strength rapidly decreased immediately after the shear crack occurred. The actual shear strength of the BS-0 specimen was about 39% higher than the value calculated by applying the material test results to the nominal shear strength equation of ACI 318-19.
In this work a two-dimensional formulation describing the fracture process in reinforcedconcrete is developed, implemented and validated. The cracks in the material are capturedby means of continuum strong discontinuity approach (CSDA) (Oliver 1996) and the constitutivemodel of composite material is defined through mixing theory (Truesdell & Toupin1960).
According to the proposed formulation, on each point of solid, the strain and stress fieldsof the reinforced concrete are described as a composite material. This has the followingadvantages: first, the model facilitates the implementation on the finite element method,since many ingredients of standard numerical process remain, and secondly, the macroscopic scale of analysis avoids the discretization of each component material and the interactioneffects, and consequently the computational cost is reduced.
The model can reproduce two different stages of cracking in the reinforced concrete.Initially, the steel capacity and the adherence in the interface produce a stable stage of distributedcracking, where appear many cracks with constant spacing and opening. Afterward,a localization cracking stage is characterized by few cracks while the structural response decreases.Reinforced concrete members subjected to tension, bending and shear are simulated.The numerical results, mainly the structural response and the crack pattern, are comparedwith experimental test (Leonhardt 1965; Collins, Vecchio et al. 1985; Ouyang & Shah 1994;Ruiz, Elices et al. 1998). The correlation between numerical results using the proposedformulation and actual results is quantitative and qualitatively satisfactory.
In this work a two-dimensional formulation describing the fracture process in reinforcedconcrete is developed, implemented and validated. The cracks in the material are capturedby means of continuum strong discontinuity approach (CSDA) (Oliver 1996) and the constitutivemodel of composite material is defined through mixing theory (Truesdell & Toupin1960).
According to the proposed formulation, on each point of solid, the strain and stress fieldsof the reinforced concrete are described as a composite material. This has the followingadvantages: first, the model facilitates the implementation on the finite element method,since many ingredients of standard numerical process remain, and secondly, the macroscopic scale of analysis avoids the discretization of each component material and the interactioneffects, and consequently the computational cost is reduced.
The model can reproduce two different stages of cracking in the reinforced concrete.Initially, the steel capacity and the adherence in the interface produce a stable stage of distributedcracking, where appear many cracks with constant spacing and opening. Afterward,a localization cracking stage is characterized by few cracks while the structural response decreases.Reinforced concrete members subjected to tension, bending and shear are simulated.The numerical results, mainly the structural response and the crack pattern, are comparedwith experimental test (Leonhardt 1965; Collins, Vecchio et al. 1985; Ouyang & Shah 1994;Ruiz, Elices et al. 1998). The correlation between numerical results using the proposedformulation and actual results is quantitative and qualitatively satisfactory. 2ff7e9595c
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