• Magazine of the Korean Society of Agricultural Engineers
• /
• v.44 no.3
• /
• pp.73-84
• /
• 2002

Nominal shear strength of concrete beam is the combined strength of concrete shear strength and steel shear strength in current design code. But Torsional moment strength of concrete is neglected in calculation of the nominal torsional moment strength of reinforced concrete beam in 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 to the nominal torsional moment strength of reinforced concrete beam. To verify the validity of the proposed model, the nominal torsional moment strengths according to CEB, two ACI codes(89, 99) and proposed model are compared to experimental torsional strengths of 55 test specimens found in literature. The nominal torsional moment strengths by the proposed model show the best results.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2021.05a
• /
• pp.181-182
• /
• 2021

Selecting a proper tile cement for ceramic tile is important to secure tile construction quality. But there is some ambiguity in standards about evaluating adhesion test such as using KS L 1593 in Lab test but using KS L 1592 in site. So, this study aims to how to select proper tile cement for securing adhesion strength in site considering both tensile and shear adhesion strength of cement for ceramic tile. Also, when doing tensile adhesion test in site, there may be adhesion drop because of cutting tile with grinder. As a result, drop of adhesion strength is about 9% ans quality manager consider these factor and should select proper tile cement.

• Journal of Welding and Joining
• /
• v.20 no.2
• /
• pp.95-101
• /
• 2002

After high power lasers are avaliable in the commercial market, the number of applications of the laser welding has been increased in manufacturing industries. Although the tailored blank laser welding of butt jointed steel sheets is well known recently in the automotive industries, the lap joint laser welding is a new technology to the automotive manufacturing people as well as the design people. But the deep penetration laser welding seems to be preferred to the partial penetration welding for the lap joint welding in the automotive manufacturers because the partial penetration is a serious deflect for the butt joint. In this study, the feasibility of partial penetration welding fur the lap joint $CO_2$ laser welding was studied fur the 1mm thick 390MPa high strength steel sheets for automotive bodies. The process window of the lap joint partial penetration welding was obtained from experiments with the gap size and the welding speed as process parameters. The partial penetration welding was found excellent on the basis of the tensile shear strength and sectional geometry. The bead width, input energy Per volume, tensile-shear strength, deformation energy and the sectional geometries after tensile-shear tests of partial penetration welded specimens are compared with those of full penetration welded specimens with a series of gaps and welding speeds.

• Journal of Power System Engineering
• /
• v.17 no.4
• /
• pp.115-119
• /
• 2013

The resistance spot welding of high strength steel degrades the weldability because of its high strength with rich chemical composition and coating layer to protect from corrosion. And the weld Expulsion is prone to occur and severely affect the nugget guality when the initial gap between automatic borrowing galvanied steel sheets(SGARC35) and Zn-coateel trip steels(GA580TRIP and GA980 TRIP) exist in resistance spot welding(RSW). RSW is one of the most popular welding processes used to join sheet metals. but weld guality sometimes do creases due to welding condition. in this paper to verity tue weldability using spot welding with the hemispherically concaved electrode, tensile shear strength and cross-tensile strength were measured by a universal test machine. in addition, the nugget size on cross-sectional area of the weld was observed by optical and electron microscopy. As a result, the nugget size of this specimen is increased with increasing welding current and Max load of tensile-shear strength is increased with welding current is increasing.

• International Journal of Highway Engineering
• /
• v.14 no.5
• /
• pp.31-45
• /
• 2012

PURPOSES: In Korea, rapid maintenance of distressed concrete pavement is required to prevent traffic jam of the highway. Asphalt concrete overlay has been used as a general maintenance method of construction for aged concrete pavement. AC overlay on existing concrete pavements experience various early distresses such as reflection crack, pothole and rutting, due to different physical characteristics between asphalt overlay and existing concrete pavement. Bonded concrete overlay(BCO) is a good alternative since it has advantages that can reduce various distresses during the service life since overlay material has similar properties with existing concrete pavements. Recently, BCO which uses the ultra rapid harding cement has been applied for maintenance of highway. BCO has advantage of structural performance since it does monolithic behave with existing pavement. Therefore, it is important to have a suitable bond strength criteria for securing performance of BCO. Bond strength criteria should be larger than normal tensile stress and horizontal shear stress occurred by traffic and environmental loading at bond interface. Normal tensile stress and horizontal shear stress need to estimated for the establishment of practical bond strength criteria. METHODS: This study aimed to estimate the bond stresses at the interface of BCO using the three dimensional finite element analysis. RESULTS: As a result of this study, major failure mode and maximum bond stress are evaluated through the analysis of normal tensile stress and horizontal shear stress for various traffic and environmental load conditions. CONCLUSIONS: It was known that normal tensile stresses are dominated by environmental loading, and, horizontal shear stresses are dominated by traffic loading. In addition, bond failure occurred by both of normal tensile stresses and horizontal shear stresses; however, normal tensile stresses are predominated over horizontal shear stresses.

• Smart Structures and Systems
• /
• v.22 no.5
• /
• pp.611-620
• /
• 2018

In this research the effect of bedding layer angle and bedding layer thickness on the shear failure mechanism of concrete has been investigated using PFC3D. For this purpose, firstly calibration of PFC3d was performed using Brazilian tensile strength. Secondly shear test was performed on the bedding layer. Thickness of layers were 5 mm, 10 mm and 20 mm. in each thickness layer, layer angles changes from $0^{\circ}$ to $90^{\circ}$ with increment of $25^{\circ}$. Totally 15 model were simulated and tested by loading rate of 0.016 mm/s. The results shows that when layer angle is less than $50^{\circ}$, tensile cracks initiates between the layers and propagate till coalesce with model boundary. Its trace is too high. With increasing the layer angle, less layer mobilize in failure process. Also the failure trace is very short. It's to be note that number of cracks decrease with increasing the layer thickness. The minimum shear test strength was occurred when layer angle is more than $50^{\circ}$. The maximum value occurred in $0^{\circ}$. Also, the shear test tensile strength was increased by increasing the layer thickness.

• Structural Engineering and Mechanics
• /
• v.68 no.4
• /
• pp.507-517
• /
• 2018

In this research the effect of bedding layer angle and bedding layer thickness on the shear failure mechanism of concrete has been investigated using PFC3D. For this purpose, firstly calibration of PFC3d was performed using Brazilian tensile strength. Secondly punch shear test was performed on the bedding layer. Thickness of layers were 5 mm, 10 mm and 20 mm. in each thickness layer, layer angles changes from $0^{\circ}$ to $90^{\circ}$ with increment of $25^{\circ}$. Totally 15 model were simulated and tested by loading rate of 0.016 mm/s. The results show that when layer angle is less than $50^{\circ}$, tensile cracks initiates between the layers and propagate till coalesce with model boundary. Its trace is too high. With increasing the layer angle, less layer mobilizes in failure process. Also, the failure trace is very short. It's to be note that number of cracks decrease with increasing the layer thickness. The minimum shear punch test strength was occurred when layer angle is more than $50^{\circ}$. The maximum value occurred in $0^{\circ}$. Also, the shear punch test tensile strength was increased by increasing the layer thickness.

• Structural Engineering and Mechanics
• /
• v.73 no.5
• /
• pp.515-527
• /
• 2020

This paper presents a stress field approach for the shear capacity of stirrup-reinforced concrete beams that explicitly incorporates the contribution of principal tensile stresses in concrete. This formulation represents an extension of the variable strut inclination method adopted in the Eurocode 2. In this model, the stress fields in web concrete consist of principal compressive stresses inclined at an angle θ combined with principal tensile stresses oriented along a direction orthogonal to the former (the latter being typically neglected in other formulations). Three different failure mechanisms are identified, from which the strut inclination angle and the corresponding shear strength are determined through equilibrium principles and the static theorem of limit analysis, similar to the EC-2 approach. It is demonstrated that incorporating the contribution of principal tensile stresses of concrete slightly increases the ultimate inclination angle of the compression struts as well as the shear capacity of reinforced concrete beams. The proposed stress field approach improves the prediction of the shear strength in comparison with the Eurocode 2 model, in terms of both accuracy (mean) and precision (CoV), as demonstrated by a broad comparison with more than 200 published experimental results from the literature.

• Journal of Welding and Joining
• /
• v.18 no.1
• /
• pp.52-58
• /
• 2000

Spot welding, namely a kind of electric resisting welding has been used widely in field of automobile and aircraft industries because of easiness to apply. Specimens used in this study was a mild steel of 1.2mm thickness and the electrode was a Cu-Cr alloy of 6mm diameter. The surface sheared of specimens after testing of tensile shear was observed by SEM(scanning electron microscope) after ultrasonic cleaning for 10min., and microstructures and grain size of all specimens were measured with using of O.M.(Optical microscope). By the means of measurement and observations of tensile shear load, fatigue strength and share surface, the weldability of spot welding was evaluated. When tensile shearing testing, fracture starting point in all specimens was took place at the bond between HAZ(Heat affected zone) and nugget. With increasing in number of layers, fatigue strength was decreased. With increasing in electric current, grain size in the HAZ became more fine.

• Journal of the Korea Concrete Institute
• /
• v.27 no.3
• /
• pp.299-309
• /
• 2015

Ultra High Performance Fiber Reinforced Concrete (UHPFRC) is distinguished from the normal concrete by outstanding compressive and tensile strength. Cracked normal concrete resists shear by aggregate interlocking while clamped by transverse reinforcement, which is called as shear friction theory. Cracked UHPFRC is expected to have a different shear transfer mechanism due to rather smooth crack face and post-cracking behavior under tensile force. Twenty-four push-off specimens with transverse reinforcement are tested for four different fiber volume ratio and three different ratio of reinforcement along the shear plane. The shear friction strength for monolithic concrete are suggested by limit analysis of plasticity and verified by test results. Plastic analysis gives a conservative, but reasonable estimate. The suggested shear friction factor and effectiveness factor of UHPFRC can be applied for interface shear transfer design of high-strength concrete and fiber reinforced concrete with post-cracking tensile strength.