• Structural Engineering and Mechanics
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• v.91 no.5
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• pp.427-441
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• 2024

Large-scale cantilever reinforced concrete (RC) columns with footing/stub were examined to determine their seismic response under a quasi-static increasing-magnitude cyclic lateral loading. Three-dimensional (3D) numerical models of RC columns with ductile and non-ductile reinforcement arrangements were developed in a Finite Element (FE) software, i.e., ABAQUS, to corroborate them with the experimental study conducted by the author. Both simulated models were validated with the experimental results in all respects, and the theoretical axial capacity of columns under concentric axial load (P₀) was calculated. Subsequently, a detailed parametric study was conducted by adopting the force and reinforcement variables. These variables include axial compression ratios (ACR) varying from 0.35P₀ to 0.7P₀ and the amount of lateral reinforcements taken as 0.33% and 1.31% representing the non-ductile and ductile columns, respectively. This research outcome conclusively quantifies the combined effect of ACR levels and lateral reinforcement spacing on the flexural response and ductility characteristics of RC columns. The comparative analysis reveals that increased ACR levels resulted in a severe reduction in strength, deformability and ductility characteristics of both ductile and non-ductile columns. Structural response of ductile columns at higher ACR levels was comparable to the non-ductile columns, nullifying the beneficial effects of ductile design provisions. Higher ACR levels caused decline in pre-peak and post-peak response trajectories, leading to an earlier attainment of peak response at lower drift levels.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.897-902
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• 2001

Recently, structure performance is maximized by using high strength concrete. In design of structure, concrete need combination with reinforcement, but use of common strength reinforcement make member complex bar placement, so high strength concrete members require increased strength reinforcement. If common strength reinforcement replaced by equal tension area of high strength reinforcement, reinforcement ratio increase and brittle failure of member may occur by material change. So, adequate upper limit of strength ratio is required to affirm ductile behavior in application of high strength reinforcement. In this study, ductility behavior was analysed by factor of reinforcement ratio, strength of concrete and reinforcement. The result indicate that ductile failure is shown under 0.35 $\rho_{b}$ in any reinforcement strength of same section and high strength concrete of 800kg/$cm^{2}$ used commonly is compatible with reinforcement of 5500kg/$cm^{2}$.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.4
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• pp.147-155
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• 2019

In this study, flexural tests of granite reinforced with titanium metal rods were carried out to repair and restore the damaged stone-made cultural heritage, the Stone Pagoda of the Mireuksa Temple Site. A total of twelve specimens were tested. The primary test parameters are the reinforcement ratio and the location of the reinforcement. For restoration, epoxy resin was used for joining the separated stones, and titanium metal rods were used for structural reinforcement. Test results showed that the flexural failure took place in specimens with a reinforcement ratio of 0.8% or less, and shear failure occurred when the reinforcement ratio was 1.68% or more. The peak load of the reinforced stone was found to be highly related to the reinforcement ratio. The peak load increased with increasing the reinforcement ratio. Also, the flexural behaviors of the reinforced stones were affected by the location of the reinforcement. Based on the test results, this study recommends the reinforcement ratio of the reinforced granite to induce ductile behavior.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.53-56
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• 2005

This paper investigates the effect of ductile deformation behavior of high performance hybrid fiber-reinforced cement composites (HPHFRCCs) on the shear behavior of coupling beams to lateral load reversals. The matrix ductility and the reinforcement layout were the main variables of the tests. Three short coupling beams with two different reinforcement arrangements and matrixes were tested. They were subjected to cyclic loading by a suitable experimental setup. All specimens were characterized by a shear span-depth ratio of 1.0. The reinforcement layouts consisted of a classical scheme and diagonal scheme without confining ties. The effects of matrix ductility on deflections, strains, crack widths, crack patterns, failure modes, and ultimate shear load of coupling beams have been examined. The combination of a ductile cementitious matrix and steel reinforcement is found to result in improved energy dissipation capacity, simplification of reinforcement details, and damage-tolerant inelastic deformation behavior. Test results showed that the HPFRCC coupling beams behaved better than normal reinforced concrete control beams. These results were produced by HPHFRCC's tensile deformation capacity, damage tolerance and tensile strength.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.1486-1491
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• 2010

Recently, the frequency and magnitude of the earthquake have increased. The structural safety of the public facilities such as bridges and tunnels etc. which were not concerned for earthquake resistant design are increased. Fiber reinforcement polymer that has been frequently studied for seismic retrofit has advantage as seismic reinforcement material, but it has disadvantage of the brittleness. Therefore, the investigation of safety and seismic reinforcement are required. In this study, new FRP-ductile material layered composites proposed to seismic performance reinforced of subway tunnel. Tensile test of FRP-ductile material layered composites showed that Maximum tensile force of FRP-ductile using Aluminum is similar to existing FRP reinforcement material and maximum strain was increased. In case of application of domestic subway tunnel which need ductility, layered composites of FRP-Aluminum is estimated effectively for increase of seismic performance.

• Magazine of the Korea Concrete Institute
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• v.8 no.6
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• pp.141-149
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• 1996

The reinforced high-strength-concrete beam subjected to flexure moment behaves more brittly than the moderate-strength-concrete beam reinforced with equal reinforcement ratio($\rho$/$\rho_b$). Test results show that when the concrete strength exceeds 830kg/$cm^2$, the maximum reinforcement ratio should be less than $0.6{\rho}_b$ for ductile behavior (${\rho}_b$=balanced steel ratio). The ratio of flexural strength between experimental results and analytical results with rectangular stress block decrease as the compressive strength of concrete increase. The shape of the compressive stress block distributed triangularly. because the ascending part of the stress-strain curve shows fairly linear response up to maximum stress in contrast to the nonlinear behavior of the medium and low strength specimens.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.3
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• pp.181-189
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• 2001

Recently, the need for strengthening reinforced concrete(R.C.) structure has been increased, particularly when there is an increase in load requirements, a change in use, a degradation problem, or design/construction defects. The use of composite materials for structural repair presents several advantages and has been investigated all over the world. It is well known that the incorporation of carbon fiber sheet(CFS) with concrete is one of the most effective ways to strengthen the R.C. structure. In this papers, experimentally investigated the ductile behavior of the R.C. beams strengthened with CFS, and provided the basic data for design of R.C. beams strengthened with CFS. Tests were carried out with 15 beams ($20cm{\times}30cm{\times}240cm$) reinforced with CFS, and with parameters including and the ratio of tensile reinforcement to that of balanced condition and number of CFS. The results show that strengthened and non-strengthened beams exhibit different ductile behovior. Non-strengthened beams showed increase of ductility as amount of the tensile reinforcement decreased. However, bearing capacity of the CFS-strengthened beams are dictated by the strength of the CFS layers that a very high ductility is indicated for the beams with large number of CFS.

• Journal of the Earthquake Engineering Society of Korea
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• v.27 no.4
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• pp.171-180
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• 2023

This study proposed a seismic reinforcement of RC columns with non-seismic details, a fiber reinforcement method of aramid sheets and MLCP (high elasticity aromatic polyester fiber material) with different characteristics, and 4 full-size column specimens and conducted experiments. The results show that a non-seismic specimen (RC-Orig) rapidly lost its load-bearing capacity after reaching the maximum load, and shear failure occurred. The RC column reinforced with three types of aramid did not show an apparent increase in strength compared to the unreinforced specimen but showed a ductile behavior supporting the load while receiving a lateral displacement at least 1.57 to 1.95 times higher than the unreinforced specimen. The fracture mode of the specimen, according to the application of lateral load, also changed from shear to ductile fracture through aramid-based reinforcement. In addition, when examining the energy dissipation ability of the reinforced specimens, a ductile behavior dissipating seismic energy performed 4 times greater and more stably than the existing specimens.

• Earthquakes and Structures
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• v.21 no.5
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• pp.489-503
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• 2021

This research aims to investigate the seismic response of RC shear wall buildings of 5-, 6-, 7-, 8-, 9-, and 10-story designed as conventional and ductile and located in moderate seismic zone in Saudi Arabia in accordance with the seismic provisions of the American code ASCE-7-16. Dynamic analysis is conducted using the developed models in ETABS and the design spectra of the selected zone. The seismic responses of a number of design variations are evaluated in terms of story displacements, drift, shear and moments of both conventional and ductile building models as performance measures and presented comparatively. In addition, pushover analysis is also performed for the lowest and highest building models. Cost estimate of ductile and conventional walls is evaluated and compared to each other in terms of weight of reinforcement bars. In addition, due to the complexity of design and installation of ductile shear walls, sensitivity analysis is performed as well. It is observed that conventional design considerably increases induced seismic responses as well as cost compared to ductile one.

• Journal of the Korea Concrete Institute
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• v.19 no.4
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• pp.441-448
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• 2007

The beam-column assembly in a ductile reinforced concrete (RC) frames subjected to seismic loading are generally controlled by shear and bond mechanisms, both of which exhibit poor hysteretic properties. Hence the response of joints is restricted essentially to the elastic domain. The usual earthquake resistant design philosophy of ductile frame buildings allows the beams to form plastic hinges adjacent to beam-column assembly. Increased strain in these plastic hinge regions affect on joint strain to be increased. Thus bond and shear joint strength are decreased. The research reported in this paper presents the test results of five RC beam-column assembly after developing plastic hinges in beams. Main parameter of the test Joints was the amount of the longitudinal tensile reinforcement of the beams. Test results indicted that the ductile capacity of joints increased as the longitudinal tensile reinforcement of the beams decreased. In addition, both the tensile strain of the longitudinal reinforcement bars in the joint and the ductile ratio of the beam-column assemblages increased due to the yielding of steel bars in the plastic hinge regions.