• Structural Engineering and Mechanics
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• v.33 no.6
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• pp.765-779
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• 2009

Quantitative condition assessment of structures has been traditionally using proof load test leading to an indication of the load-carrying capacity. Alternative approaches using ultrasonic, dynamics etc. are based on the unloaded state of the structure and anomalies may not be fully mobilized in the load resisting path and thus their effects are not fully included in the measured responses. This paper studies the effect of the load carried by a reinforced concrete beam on the assessment result of the crack damage. This assessment can only be performed with an approach based on static measurement. The crack damage is modelled as a crack zone over an area of high tensile stress of the member, and it is represented by a damage function for the simulation study. An existing nonlinear optimization algorithm is adopted. The identified damage extent from a selected high level load and a low load level are compared, and it is concluded that accurate assessment can only be obtained at a load level close to the one that creates the damage.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.1
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• pp.69-78
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• 1991

This paper concentrates on the analysis of deflection of the reinforced concrete flexural members under monotonic loading. Concrete is treated as an orthotropic nonlinear material. The concept of equivalent strain and crack strain are used to establish independent stress-strain relationships in the directions of orthotropy. Steel is modeled as an elstoplastic material, and von Mises failure criterion is applied. The finite element computer program for the nonlinear analysis of the deflection of RC flexural members under monotonic loading is developed. The accuracy and reliability of the numerical procedure is demonstrated by the FEM analysis and experiments of the under reinforced concrete beams over the entire loading range up to failure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.4
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• pp.203-210
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• 2004

This study reviewed various current methods of evaluating the toughness of steel fiber reinforced concrete specimens and criticized the use of various multiples of first-crack deflection to define toughness indices. The load-CMOD curve to determine toughness, instead of load-deflection curve, was used. The notched steel fiber reinforced concrete specimens With different water/cement ratio(0 35, 0.40, 0.45, 0 50) and fiber volume content(0.0%, 0 5%, 1 0%, 1.5%) were tested under third point bending.

• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.4
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• pp.104-112
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• 1999

Tensile behavior in concrete has been neglected until recently. However, the effect of tensile stresses in concrete must be considered where the member primarily carries tensile forces or when ultimate strength is affected by the cracking history. In this paper, a series of experiments were performed with a reinforced rectangular beams of 15 specimens in order to investigate the effect of tension stiffening into the nonlinear analysis and cracking behavior. The experimental results were analyzed in terms of load-deflection curves and strain fracture energy with respect to the main experimental variables such as types of specimen, strength of concrete and steel ration. The results from experiments and finite element analysis were compared in terms of load-deflection relationship and cracking pattern. The results are as follows ; The tension stffening effects of reinforced concrete beams were observedc up to yielding of members after cracking showing strain energy difference of 35 % at the beam of 0.57% steel ratio compared with that of beam ignoring the tension stiffening effect. The tension stiffening of concrete strength 400kgf/$\textrm{cm}^2$ and 600kgf/$\textrm{cm}^2$ increased by 8% and 13%, respectively, compared with that of concrete strength 200kgf/$\textrm{cm}^2$. The tension stiffening effects were greater at a ductile member rather than a brittle one. The load-deflection results of finite element analysis showed very similar results from experiment. The crack growth and pattern might be predicted from the nonlinear finite element analysis considering concrete stiffening.

• International Journal of Highway Engineering
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• v.8 no.1 s.27
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• pp.139-152
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• 2006

Many experimental and numerical approaches have been developed to evaluate paving materials and to predict pavement response and distress. Micromechanical simulation modeling is a technology that can reduce the number of physical tests required in material formulation and design and that can provide more details, e.g., the internal stress and strain state, and energy evolution and dissipation in simulated specimens with realistic microstructural features. A clustered distinct element modeling (DEM) approach was implemented In the two-dimensional particle flow software package (PFC-2D) to study the complex behavior observed in asphalt mixture fracturing. The relationship between continuous and discontinuous material properties was defined based on the potential energy approach. The theoretical relationship was validated with the uniform axial compression and cantilever beam model using two-dimensional plane strain and plane stress models. A bilinear cohesive displacement-softening model was implemented as an intrinsic interface and applied for both homogeneous and heterogeneous fracture modeling in order to simulate behavior in the fracture process zone and to simulate crack propagation. A disk-shaped compact tension test (DC(T)) with heterogeneous microstructure was simulated and compared with the experimental fracture test results to study Mode I fracture. The realistic arbitrary crack propagation including crack deflection, microcracking, crack face sliding, crack branching, and crack tip blunting could be represented in the fracture models. This micromechanical modeling approach represents the early developmental stages towards a 'virtual asphalt laboratory,' where simulations of laboratory tests and eventually field response and distress predictions can be made to enhance our understanding of pavement distress mechanisms, such its thermal fracture, reflective cracking, and fatigue crack growth.

• Structural Engineering and Mechanics
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• v.11 no.3
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• pp.301-314
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• 2001

The purpose of this experimental study is to investigate the damage mechanism due to shear-fatigue behavior of high-strength reinforced concrete beams under repeated loading. The relationship between the number of cycles and the deflection or strain, the crack growths and modes of failure with the increase of number of cycles, fatigue strength, and S-N curve were observed through a fatigue test. Based on the fatigue test results, high-strength reinforced concrete beams failed at 57-66 percent of static ultimate strength for 2 million cycles. The fatigue strength at 2 million cycles from S-N curves was shown as about 60 percent of static ultimate strength. Compared to normal-strength reinforced concrete beams, fatigue capacity of high-strength reinforced concrete beams was similar to or lower than fatigue capacity of normal-strength reinforced concrete beams. Fatigue capacity of normal-strength reinforced concrete beams improved by over 60 percent.

• Computers and Concrete
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• v.21 no.2
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• pp.157-166
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• 2018

This article presents the flexural behaviour of reinforced fly ash (FA)-based geopolymer concrete (GPC) beams with partial replacement of FA for about 10% by weight with paper sludge ash (PSA). The beams were made of M35 grade concrete and cured under three curing conditions for comparison viz., ambient curing, external exposure curing, and oven curing at $60^{\circ}C$. The beams were experimentally tested at the 28th day of casting after curing by conducting two-point loading flexural test. Performance aspects such as load carrying capacity, first crack load, load-deflection and moment-curvature behaviours of both types of beams were experimentally studied and their results were compared under different curing conditions. To verify the response of reinforced GPC beams numerically, an ANSYS 13.0 finite element program was also used. The result shows that there is a good agreement between computer model failure behaviour with the experimental failure behaviour.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.319-324
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• 1999

This study is to investigate the properties on the load-deflection and fracture behaviors of the steel fiber reinforced concrete(SFRC) slab model specimens, Steel fibers of indent, crimp, and end hook shape were considered to reinforce the matrix under various mixing conditions and proportions. Initial cracking load, maximum load, and energy absorption capacity(load carrying capacity) of SFRC panel specimen increased with increase of steel fiber contents. And the plain concrete slab was fractured abruptly after maximum load but SRFC slabs were fractured smoothly by steel fibers in concrete matrix operated as cracking resistance force after maximum load. Indent, crimp and end hook shape steel fibers were effective in reinforcing the matrices but end hook type fiber were superior to indent and crimp type fibers.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.519-524
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• 2007

Recently, Fiber sheets have been used for strengthening the deteriorated reinforced concrete RC slabs because of its resistant capacity of corrosion and repairing works. The purpose of this study is to carry out the experimental studies on thirteen kinds of RC slabs and to investigate the behavior of RC slabs form the experimental results. Test parameters are the strengthening material, the number of sheet layer and strengthening direction. The behavior of strengthened He: slabs is represented by crack load-deflection curves and maximum load. And the parametric study based on the nonlinear FEM analysis are performed and its results are discussed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.4 no.1
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• pp.93-100
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• 2000

The purpose of this study is to investigate the shear behavior of reinforced concrete beams according to small shear span-depth ratio between a/d=1.5, 2.8, 3.6. In general, shear strength of reinforced concrete beams is dependent on the compressive strength of concrete the longitudinal steel ratio, the shear span-depth ratio and shear reinforcement. The static test was carried out to measure the ultimate load, the initial load of flexural and diagonal cracking, crack patterns, fracture modes. The load versus strain and load versus deflection relations were obtained from the static test. The test results on shear strength were compared with results obtained by the formulas of ACI code 318-95. The shear strength of reinforced concrete beams exceeded those predicted following present ACI code 318-95(11-6).