• Journal of the Korea Concrete Institute
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• v.14 no.1
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• pp.24-32
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• 2002

The modified compression field theory is already applied in shear problem at some code(AASHTO-1998) partly. Nominal shear strength of concrete beam is sum of the concrete shcar strength and the steel shear strength in the current design code. But Torsional moment strength of concrete is neglected in the calculation of the nominal torsional moment strength of concrete beam In the current revised code. Tensile stress of concrete strut between cracks is still in effect due to tension stiffening effect. But The tensile stresses of concrete after cracking are neglected in bending and torsion In design. The torsional behavior is similar to the shear behavior in mechanics. Therefore the torsional moment strength of concrete should be concluded in the nominal torsional moment strength of reinforced concrete beam. This paper shows that the torsional moment strength of concrete is caused by the average principal tensile stress of concrete. To verify the validity of the proposed model, the nominal torsional moment strengths according to two ACI codes (89, 99) and proposed model are compared to experimental torsional moment strengths of 55 test specimens found in literature. The nominal torsional moment strengths by the proposed model show the best results.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.5
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• pp.19-25
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• 2007

In this study, a program based on the P-M interaction curve is developed to calculate the nominal strength of concrete pole. Using this, it is verified to compare with previous studies and the nominal strength$(M_n)$ of concrete pole is calculated. It is less than the rupture strength$(M_r)$ of the design standard. Thus, to increase nominal strength, several parameters are selected like as size of tension and reinforced bars, position of those, number of reinforcement bars, thickness of concrete pole, and diameter of it. The effects of those are analysed in the study. It is supposed that section of concrete pole are satisfied rupture strength.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.2
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• pp.175-186
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• 2006

Strength method for determining nominal moment capacity of reinforced concrete members is also assumed to be suitable for strengthened members with FRP system. If the internal tensile forces of the strengthened member from steel and FRP is insufficient, the FRP system strain might become greater than its ultimate tensile strain which makes the strength method a contradiction and unapplicable. The experimental results of 27 strengthened beams with carbon fiber sheets which have relatively lower tensile forces from steel and FRP show that not only concrete compressive strain is lower than 0.003 but also measured ultimate moment was lower than nominal moment using the strength method.

• Journal of Korean Society of Steel Construction
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• v.24 no.5
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• pp.503-510
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• 2012

High performance, high strength steels were developed and used in steel structures recently. Since the newly developed high strength steels posses different toughness, weldability, yield strength ratio, etc. in compare with conventional structural steels, it is requred to investigate the applicability of the design strength of fillet weld specified in the existing design codes. The comparison of the design strengths of various codes from domestic and overseas shows quite a difference. Test results for fillet weld strengths were collected and statistically analysed. Each of yield strength, tensile strength of parent material and tensile strength of weld metal was selected as a main parameter for each estimation equation respectively. All the estimation equations yield almost same values for each type of steel regardless the type of main parameter selected. Considering the behaviour of fillet welded joints and for practical purposes, it is proposed that the equation with tensile strength of parent material is to be used in design codes. The comparison with the proposed nominal strengths of fillet welds shows that the existing design codes could lead to an uneconomical result for low strength steels and lie on an unsafe side for high strength steels.

• Journal of the Korean Society of Hazard Mitigation
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• v.4 no.4 s.15
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• pp.1-6
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• 2004

Fatigue tests were carried out for butt welded joints with SM520-TMC steel plate with thickness between 20mm and 80mm. The test results were analysed statistically and the effect of plate thickness on the fatigue strength investigated. The fatigue strengths based on nominal stress range satisfy the requirement of the standards. Due to misalignment of the specimens, the measured stresses are higher than the nominal stresses especially for 20mm thick plates. If fatigue strengths are evaluated based on the measured stresses, then the fatigue strengths are greater than those based on nominal stresses. The results show that the thickness effect is similar to the formula proposed by Gurney.

• Journal of Korean Society of Steel Construction
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• v.26 no.3
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• pp.205-217
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• 2014

In this study, flexural strength and ductility requirements of composite hybrid steel I-girder with its HSB(high performance steel for bridge) applied to tension flanges are examined in positive bending. In AASHTO LRFD specification, flexural strength and ductility requirements of composite I-girder in positive bending are specified in terms of plastic moment and plastic neutral axis that are derived from plastic behavior of conventional steel. However, plastic zone cannot be defined clearly from the stress-strain behavior of HSB unlike the behavior of conventional steel. Therefore, through idealized stress-strain curves of HSB, the plastic moment of composite hybrid steel I-girder with its HSB applied to tension flanges is defined by assuming the plastic zone of HSB. By using the consequences of numerical analysis regarding arbitrary cross-sections that have various dimensions, ductility requirements and flexural strength of composite hybrid I-girder with its HSB applied to tension flange are proposed.

• Journal of the Korea Concrete Institute
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• v.19 no.1
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• pp.103-111
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• 2007

Experimental study was carried out to investigate the structural performance of composite beams with steel fiber concrete and angle. For this purpose, seven specimens composed of two RC beams with or without steel fiber and five composite beams with steel fiber and angle were constructed and tested. All specimens had no web shear reinforcement. Main variables for the specimens were tensile reinforcement ratio and fiber volume fraction. Based on the test results, structural performance such as strength, stiffness, ductility and energy dissipation capacity was evaluated and compared with the predicted strength. The prediction of flexure and shear strength gives a good relationship with the observed strength. The strength, ductility and energy dissipation capacity are increased, as the fiber volume fraction is increased. Meanwhile, high tensile reinforcement ratio resulted in the reduction of ductility and energy dissipation capacity for the composite beams.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.4
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• pp.580-588
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• 2010

OPB(out-of-plane bending)-induced failure of mooring chain was firstly addressed by CALM (catenary anchor leg mooring)-type offloading buoy, located approximately one mile away from the bow of the Girassol FPSO which was installed offshore area of Angola in September 2001. This study deals with verifying the load transfer mechanism between the first free chain link and connected two chain links inside the chain hawse. OPB moment to angle variation relationships are proposed by extensive parametric study where the used design variables are static friction coefficients, proof test loads, nominal tension forces, chain link diameters, chain link grades and chain link types. The stress ranges due to OPB moments are obtained using nonlinear FEAs (finite element analyses). Final stress ranges are derived considering ones from IPT (in-plane tension) forces. Also a formula for OPB fatigue assessment is briefly introduced.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.129-137
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• 2020

In designing a high strength bolted beam splice using steel for building structures, it is necessary to present the appropriate steel grade selection criteria for how to determine the cover plate steel grade. This study examined the difference in tensile behavior according to the steel grades through static tensile tests simulating the beam member high strength bolt joints flange. For this purpose, the specimens were designed and fabricated with the main variables, such as the thickness, steel grade and the strength of flange and cover plate, which are expected to affect the splice strength and behavior. The tensile test results for a total of 48 specimens showed that the tensile-load capacity exceeded the design tensile strength applied with a nominal strength of steel in all specimens. When the design strength of the cover plate exceeded 1.25 times that of the flange plate, the flange plate governed the behavior of splice. The change in maximum tensile load due to the change in flange steel grade is not very large, but there is a difference in deformation. The test results confirmed that the steel grade and thickness of the cover plate were the main factors affecting the beam splice behavior.

• Journal of the Korea Concrete Institute
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• v.27 no.1
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• pp.11-20
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• 2015

An unbonded post-tensioned anchor using a 15.2 mm diameter 7-wire strand was developed based on finite element analysis and experimental testing. In order to evaluate its performance, static load tests and load transfer tests were conducted following KCI-PS101. The static load tests and additional strand tensile tests confirmed that the developed anchor had a capacity more than nominal tensile strength of a 7-wire strand without any damage or deterioration. According to the result of load transfer tests for many different reinforcing details, specimens with no additional reinforcing bars sustained at least 1.64 times the nominal tensile strength of the strand.