• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.727-734
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• 2006

Although a limited number of experimental investigations and finite element analyses revealed that a curved web panel in practical design has a considerable reserve strength after the elastic buckling as a straight girder web panel, the current Guide Specifications for Horizontally Curved Steel Girder Highway Bridges (AASHTO, 2003) do not consider the postbuckling strength in the ultimate shear strength due to lack of a comprehensive study. In this study, the ultimate shear strength behavior of horizontally curved steel web panels was investigated through nonlinear finite element analysis and experimental test. It was found that curved web panels used in practical designs are able to develop the postbuckling strength that is equivalent to that of straight girder web panels having the same dimensional and material properties.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.475-480
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• 2003

Latex modification of concrete provides the material with higher flexural strength. This increase in flexural strength can attribute to the crack-arresting action of polymer in concrete, and also to the bonding they provide between the matrix and aggregates. This experimental study presents the fracture behavior of 12 flexural reinforced concrete beams repaired or strengthened by latex-modified concrete with the main experimental variables such as overlay thickness, strength thickness, and shear reinforcement. The results are as follow: All beam specimens having shear reinforcement were failed by delamination rupture at concrete interface at about 80% of ultimate loading after flexural cracking. All specimens overlayed and strengthened by latex-modified concrete (LMC) showed higher ultimate flexural strength than OPC control specimen, but lower than LMC control specimen. This increase in flexural strength could attribute to the high bonding they provide between the matrix and aggregates. All specimens except two shear unreinforced showed quite similar and consistent displacement behavior. The effect of overlay and strength thickness on the load-displacement relationship were a small at this study.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.853-858
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• 2001

Experimental studies were peformed to investigate variations in ductility of shear wall with length of boundary confinement. Eight specimens containg different lengths of confinment zone, which model compressive zone in plastic regions of shear walls, were tested against eccentric vetical load. Stress-strain model for confined concrete was used to predict strength and ductility of the specimens, which was compared to the test results. The results obtained show that failure of the compressive zone occurs in a brittle manner when the stress of unconfined zone softened after the ultimate strength were reached. To enhance the ductility of shear walls with concentrated confinement zone such as barbell-type walls, the ultimate strength of the confinement zone needs to be increased, and for shear walls with distributed confinement zone the length of the confinement zone needs to be extended.

• Journal of the Korea Concrete Institute
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• v.12 no.4
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• pp.23-30
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• 2000

The purpose of this paper is to study on the shear strength of high strength concrete beams with steel fibrous. In general, the shear strength of reinforced concrete beams is affected by the compressive strengths of concrete( c), the shear span-depth ratio(a/d), the longitudinal steel ratio($\rho$ $\omega$), and shear reinforcement. An experimental investigation of the shear strength of high strength concrete beams with steel fibrous was conducted. In each series the shear span-depth ratio(a/d) was held constant at 1.5, 2.8, or 3.6, while concrete strengths were varied from 320 to 520, to 800kgf/$\textrm{cm}^2$. To verify the proposed equations the experimental results were compared with those from other researches such as equation of ACI code 318-95 or equation of Zsutty. To deduce equation for shear strength from experimental data carried out MINITAP program. According to the experimental results, the addition of steel fibrous has increased the deflection and strain at failure load, improving the brittleness of the high strength concrete.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2A
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• pp.269-279
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• 2008

In this study, the ultimate strengths of 229 simply supported reinforced concrete deep beams tested to shear failure were evaluated by the ACI 318-05's strut-tie model approach implemented with the presented indeterminate strut-tie model and its load distribution ratio. The ultimate strengths of the deep beams were also estimated by the experimental shear equations, design codes that were based on experimental and theoretical shear strength models, and current strut-tie model design codes. The validity of the present strut-tie model and its load distribution ratio was examined through the comparison of the strength analysis results classified according to the prime design variables of the shear span-to-effective depth ratio, flexural reinforcement ratio, and compressive strength of concrete.

• Structural Engineering and Mechanics
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• v.63 no.5
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• pp.575-583
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• 2017

The study covers the behavior of reinforced concrete deep beams loaded under 4-point bending, failed by shear and repaired using bonding glass fiber reinforced plastics fabrics (GFRP) patches. Two rehabilitation methods have been used to highlight the influence of the composite on the ultimate strength of the beams and their failure modes. In the first series of trials the work has been focused on the reinforcement/rehabilitation of the beam by following the continuous configuration of the FRP fabric. The patch with a U-shape did not provide satisfactory results because this reinforcement strategy does not allow to increase the ultimate strength or to avoid the abrupt shear failure mode. A second methodology of rehabilitation/reinforcement has been developed in the form of SCR (Strips of Critical Region), in which the composite materials reinforcements are positioned to band the inclined cracks (shear) caused by the shear force. The results obtained by using this method lead a superior out come in terms of ultimate strength and change of the failure mode from abrupt shearing to ductile bending.

• Geomechanics and Engineering
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• v.9 no.3
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• pp.287-311
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• 2015

The ultimate bearing capacity and failure mechanism of square footings resting on a sand layer over clay soil have been investigated numerically by performing a series of three-dimensional non-linear finite element analyses. The parameters investigated are the thickness of upper sand layer, strength of sand, undrained shear strength of lower clay and surcharge effect. The results obtained from finite element analyses were compared with those from previous design methods based on limit equilibrium approach. The results proved that the parameters investigated had considerable effect on the ultimate bearing capacity and failure mechanism occurring. It was also shown that the thickness of upper sand layer, the undrained shear strength of lower clay and the strength of sand are the most important parameters affecting the type of failure will occur. The value of the ultimate bearing capacity could be significantly different depending on the limit equilibrium method used.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.878-883
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• 2003

To modify some problems of ACI shear provisions, ultimate shear strength equation considering size effect and arch action to compute shear strength in high-strength concrete beams without stirrups is presented in this research. Three basic equations, namely size reduction factor, rho factor, and arch action factor, are derived from crack band model of fracture mechanics, analysis of previous some shear equations for longitudinal reinforcement ratio, and concrete strut described as linear function in deep beams. Constants of basic equations are determined using statistical analysis of previous shear testing data. To verify proposed shear equation for each variable, namely d, , ρ, f/sub c/' and aid, about 250 experimental data are used and proposed shear equation is compared with ACI 318-99 code, CEB-FIP Model code, Kim & Park's equation and Zsutty's equation. While proposed shear equation is simpler than other shear equations, it is shown to be economical predictions and reasonable safety margin. Hence proposed shear strength equation is expected to be applied to practice shear design.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.10a
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• pp.220-225
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• 1993

This paper is an experimental study on shear capacity of the high strength lightweight reinforced concrete beams with shear-depth ratio between 1.5 and 2.5. Thirteen T & rectangular beams were tested to determine their diagonal cracking and ultimate shear capacity. The major variables are shear span-depth ratio (a/d=1.5, 2.0, 2.5), concrete compressive strength(f'c=210, 24., 270㎏/㎠) and tensile steel ratio( =0.6, 1.2%). Based on results obtained from experiment of high strength lightweight reinforced concrete Beam & normal concrete, the following conclusions were drawn. (1) The shear capacity of high-strength lightweight concrete is less 15% than that of normal concrete under same condition. (2) As the results of Comparing this experimental datas with other various formulas. It is regarded that ACI 318-89 shear strength formula related tensile strength is proper to design formula of shear strength of high-strength lightweight reinforced concrete using lightweight concrete.

• Smart Structures and Systems
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• v.16 no.3
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• pp.497-519
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• 2015

This study discusses the use of Adaptive-Network-Based-Fuzzy-Inference-System (ANFIS) in predicting the shear strength of reinforced-concrete deep beams. 139 experimental data have been collected from renowned publications on simply supported high strength concrete deep beams. The results show that the ANFIS has strong potential as a feasible tool for predicting the shear strength of deep beams within the range of the considered input parameters. ANFIS's results are highly accurate, precise and therefore, more satisfactory. Based on the Sensitivity analysis, the shear span to depth ratio (a/d) and concrete cylinder strength ($f_c^{\prime}$) have major influence on the shear strength prediction of deep beams. The parametric study confirms the increase in shear strength of deep beams with an equal increase in the concrete strength and decrease in the shear span to-depth-ratio.