• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.3
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• pp.243-250
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• 2004

In SPS system, steel beams are used as not only temporary struts supporting the wale but main flexural members of building. Previous experimental works show that RC wale-steel beam joints have some flexural rigidity. In this paper, nonlinear analysis is performed using DRAIN-2DX program to investigate the behaviors of the underground composite frames constructed with SPS system when the rigidity of RC wale-steel beam joints change. Analysis variables are the procedure of construction, magnitude of lateral forces, and flexural rigidity of the RC wale-steel beam joint with stud connector. Analysis results show the effects of joint rigidity for the yielding process of frame and the moment and deflection at the mid-span of beam.

• Earthquakes and Structures
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• v.1 no.3
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• pp.269-287
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• 2010

High-strength concrete (HSC) is becoming more popular in the construction of beams and columns of tall buildings because of its higher stiffness and strength-to-weight ratio. However, as HSC is more brittle than normal-strength concrete (NSC), it may adversely affect the flexural ductility and deformability of concrete members. Extended from a series of theoretical study conducted on flexural ductility of concrete beams, the authors would in this paper investigate the effects of some critical factors including the degree of reinforcement, confining pressure, concrete and steel yield strength on the flexural deformability of NSC and HSC beams. The deformability, expressed herein in terms of normalised rotation capacity defined as the product of ultimate curvature and effective depth, is investigated by a parametric study using nonlinear moment-curvature analysis. From the results, it is evident that the deformability of concrete beams increases as the degree of reinforcement decreases and/or confining pressure increases. However, the effects of concrete and steel yield strength are more complicated and dependent on other factors. Quantitative analysis of all these effects on deformability of beams has been carried out and formulas for direct deformability evaluation are developed. Lastly, the proposed formulas are compared with available test results to verify its applicability.

• Structural Engineering and Mechanics
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• v.39 no.4
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• pp.465-498
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• 2011

Concrete structures are generally cracked in flexural tension at working loads. Concrete beams with asymmetric section details and crack patterns exhibit different flexural rigidity depending upon the sense of the applied flexural moment. In this paper, three different models, having the same natural period, of such SDOF bilinear dynamical systems have been proposed. The Model-I and Model-II have constant damping coefficient, but the latter is characterized by two stiffness coefficients depending upon the sense of vibration amplitude. The Model-III, additionally, has two damping coefficients as well. In this paper, the dynamical response of Model-III to sinusoidal loading has been investigated and compared with that of Model-II studied earlier. It has been found that Model-III exhibits regular and irregular sub-harmonics, jump phenomena and strong sensitivity to initial conditions, forcing frequency, system period as well as the sense of peak sinusoidal force. The constant sustained load has been found to affect the natural period of the dynamical system. The predictions of Model-I have been compared with those of the approximate linear model adopted in present practice. The behaviour exhibited by different models of the SDOF cracked elastic concrete structures under working loads and the theoretical and practical implications of the approach followed have been critically evaluated.

• Computers and Concrete
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• v.2 no.1
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• pp.1-18
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• 2005

This paper presents a study on the effects of localized steel-concrete bond degradation on the flexural behaviour of RC beams. A finite element analysis is undertaken to complete the experimental analysis. The first part deals with an experimental study on beams where bond was removed by using plastic tube at different locations and for various lengths. The flexural behaviour was studied at global scale (load-deflection) and local scale (moment-curvature). The second part, a numerical study using a simplified special finite element (rust element) modelling the rust layer occurring between reinforcement and concrete with corrosion was conducted in order to find the relation between the degree of corrosion and the degradation of the steel-concrete bond. The computed value of the corrosion degree corresponding to the total degradation of bond has been used in a second time to model the tests, in order to evaluate the influence of the loss of bond, the steel cross section reduction, and the combination of both. The results enable to evaluate the influence of the different corrosion effects on the flexural behaviour, according to the length and the location of the corroded zone.

• Structural Engineering and Mechanics
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• v.44 no.4
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• pp.521-538
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• 2012

In this study, the transverse vibrations of an axially moving flexible beams resting on multiple supports are investigated. The time-dependent velocity is assumed to vary harmonically about a constant mean velocity. Simple-simple, fixed-fixed, simple-simple-simple and fixed-simple-fixed boundary conditions are considered. The equation of motion becomes independent from geometry and material properties and boundary conditions, since equation is expressed in terms of dimensionless quantities. Then the equation is obtained by assuming small flexural rigidity. For this case, the fourth order spatial derivative multiplies a small parameter; the mathematical model converts to a boundary layer type of problem. Perturbation techniques (The Method of Multiple Scales and The Method of Matched Asymptotic Expansions) are applied to the equation of motion to obtain approximate analytical solutions. Outer expansion solution is obtained by using MMS (The Method of Multiple Scales) and it is observed that this solution does not satisfy the boundary conditions for moment and incline. In order to eliminate this problem, inner solutions are obtained by employing a second expansion near the both ends of the flexible beam. Then the outer and the inner expansion solutions are combined to obtain composite solution which approximately satisfying all the boundary conditions. Effects of axial speed and flexural rigidity on first and second natural frequency of system are investigated. And obtained results are compared with older studies.

• 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.8 no.1
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• pp.147-156
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• 2004

The Rehabilitation and repair of structurally deteriorated, reinforced concrete structures will be highly demanded in the near future. The purpose of this study is to investigate whether damaged beams that crack and deflection are developed by bending moment are restored to the former state. In conclusion, when specimens strengthened with Steel Plate, CFS(Carbon Fiber Sheet) and CFRP-Grid(Carbon Fiber Reinforced Plastic-Grid) are compared with standard specimen, flexural capacity is increased and ductility and energy absorbtion capacity are similar with undamaged specimen. Therefore Steel Plate, CFS(Carbon Fiber Sheet) and CFRP-Grid (Carbon Fiber Reinforced Plastic-Grid) have highly efficiency as material of flexural strengthening.

• Steel and Composite Structures
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• v.6 no.3
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• pp.257-284
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• 2006

The behaviour of hollow structural steel (HSS) stub columns and beams filled with normal concrete and recycled aggregate concrete (RAC) under instantaneous loading was investigated experimentally. A total of 40 specimens, including 30 stub columns and 10 beams, were tested. The main parameters varied in the tests were: (1) recycled coarse aggregate (RCA) replacement ratio, from 0 to 50%, (2) sectional type, circular and square. The main objectives of these tests were threefold: first, to describe a series of tests on new composite columns; second, to analyze the influence of RCA replacement ratio on the compressive and flexural behaviour of recycled aggregate concrete filled steel tubes (RACFST), and finally, to compare the accuracy of the predicted ultimate strength, bending moment capacity and flexural stiffness of the composite specimens by using the recommendations of ACI318-99 (1999), AIJ (1997), AISC-LRFD (1999), BS5400 (1979), DBJ13-51-2003 (2003) and EC4 (1994).

• Steel and Composite Structures
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• v.31 no.3
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• pp.303-317
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• 2019

This paper presents a finite element model for predicting the behaviour of high-strength steel bolted beam-to-column joints under monotonic loading. The developed numerical model considers the effects of material nonlinearities and geometric nonlinearities. The accuracy of the developed model is examined by comparing the predicted results with independent experimental results. It is demonstrated that the proposed model accurately predicts the ultimate flexural resistances and moment-rotation curves for high-strength steel bolted beam-to-column joints. Mechanical performance of three joint configurations with various design details is examined. A parametric study is carried out to investigate the effects of key design parameters on the behaviour of bolted beam-to-column joints with double-extended endplates. The plastic flexural capacities of the beam-to-column joints from the experimental programme and numerical analysis are compared with the current codes of practice. It is found that the initial stiffness and plastic flexural resistance of the high-strength steel beam-to-column joints are overestimated. Proper modifications need to be conducted to ensure the current analytical method can be safely used for the bolted beam-to-column joints with high-performance materials.

• Journal of Korean Society of Steel Construction
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• v.19 no.6
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• pp.643-653
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• 2007

The ultimate bending strength and flexural ductility performance of longitudinally stiffened plate girders fabricated with mild steel were investigated utilizing nonlinear incremental finite element analysis. AASHTO LRFD (2002) design specifications were reviewed for possible application of longitudinally stiffened plate girders as compact sections. In order to investigate compact section requirements for plate girders with longitudinal stiffeners in webs, a number of full-scale plate girders were modeled and analyzed up to the collapse under pure bending condition. It was found that the slenderness of sub panel of the webs, the stiffness of longitudinal stiffeners, and the slenderness of compression flanges are key parameters governing the flexural ductility of the plate girders. It was also found from finite element analysis that longitudinally stiffened plate girder sections can satisfy compact section requirements both in full plastic moment capacity and flexural ductility requirement. New design equations have been proposed for longitudinally stiffened plate girders to be treated as compact sections.