• Journal of the Korea Concrete Institute
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• v.29 no.1
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• pp.93-100
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• 2017

This study examined the one-way shear in concrete beam region and shear friction in joint region of a hybrid H-steel-reinforced concrete (HSRC) beam system with a simple ductile connection. One-way shear tests were conducted under overhanging beam system with a shear span-to-depth ratio of 1.6. Simple beams for shear friction were tested under two-point symmetrical top loads producing a clear shear span-to-depth ratio of 0.1. Test results showed that the dowel bars arranged in joint region insignificantly influence the propagation of shear cracks but enhances the shear strength of the HSRC beams by approximately 25%. The one-way shear strength and shear friction strength of HSRC beams can be conservatively evaluated using the design equations specified in ACI 318-14 and EC2 shear provisions.

• Tunnel and Underground Space
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• v.20 no.5
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• pp.344-351
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• 2010

Slip along a frictional fracture can be approached as initiation and propagation of a mode II crack along its own plane. Fracture mechanics theories predict that under pure mode II loading initiation will occur when the energy release rate of the fracture attains a critical value ($G_{IIC}$), which is generally taken as a material property. For the past few years the rock mechanics group at Purdue University has investigated experimentally the dependence of $G_{IIC}$ on normal stress and on the frictional characteristics of a fracture. A number of experiments has been conducted first on acrylic, a material that, using photoelastic methods, allows visualization of the stress field ahead of the fracture tip; and later on gypsum, a rock model material with relatively low unconfined compression strength. The experimental investigation has been expanded to include other frictional materials with higher unconfined compression strength. Direct shear tests have been conducted on specimens made with cement paste. New observations together with previous experiments indicate that $G_{IIC}$ can only be considered a material property when the peak friction angle of the discontinuity is similar to the residual friction angle; otherwise the critical energy release rate increases with normal stress.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.2
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• pp.37-42
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• 2022

The dual potential capacity model (DPCM) was extended to be suitable for evaluation of the shear strength of prestressed concrete (PSC) members in the previous study. This paper aims to simplify the DPCM for its better application in practice. To this end, a total of 172 shear test results of PSC members without shear reinforcement were collected from existing studies. The collected shear test results include PSC members with various section types and prestressing methods. It appeared that the simplified model could provide a good level of estimation accuracy of shear strength of PSC members, and it was comparable with that provided from the original DPCM.

• Journal of the Korea Concrete Institute
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• v.16 no.1 s.79
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• pp.10-17
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• 2004

Shear tests were performed on four ends of full scale U-type beams which were designed by optimum process for the depth with a live load of 4903Pa. The ratio of width to depth of full scale 10.5 m-span, composite U-type beams with topping concrete was greater than 2. Following conclusions were obtained from the evaluation on the shear performance of these precast prestressed beams. 1) Those composite U-type beams performed homogeneously up to the failure load, and conformed to ACI Strength design methods in shear and flexural behaviors. 2) The anchorage requirements on development length of strand In the ACI Provisions preyed to be a standard to determine a failure pattern within the limited test results of the shallow U-type beams. 3) Those all shear crackings developed from the end of the beams did not lead to anchorage failure. However, initiated strand slip may leads the bond failure by increasing the size of diagonal shear crackings. 4) The flexural mild reinforcement around the vertical center of beam section was effective for developments of a ductile failure.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.1 s.24
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• pp.1-9
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• 2007

This study does by purpose that propose shear resisting force equation of reinforced masonry wall that is reinforced by GFRP(glass fiber reinforced polymer) based on result that is noted through cyclic loading of masonry wall and a shaking table experiment of mock that reflect identifying marks of masonry building which is constructed in domestic. It was Rocking mode to dominate failure of masonry wall in the experiment results, and the equations of UBC show the most resemblant value with experiment results. Through this study, propose the shear force equation of GFRP strengthened masonry wall as following. $$V_n=0.02A_n{\sqrt{f'_m}}+0.022b_gh_g(1+2{\alpha})^3{\sqrt{f_g}}(N/mm^2)$$.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.1
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• pp.137-146
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• 2018

On September 12, 2016, the Gyeongju District was strongly shaken with M=5.8, which was the largest one since measured by the actual seismometer in Korea, and some buildings were damaged. The field survey of reinforced concrete school buildings in the affected area was carried out, and their residual seismic capacities(R) were estimated based on the Japanese Standard for post-earthquake damage evaluation. In this study, the M school, which was greatly damaged by the 2016 Gyeongju Earthquake, was selected, and its damage level was evaluated on the basis of the Japanese Standard. The seismic capacity of the M school was also evaluated using the nonlinear dynamic analysis, and relationships between its damage level and seismic capacity was also conducted to investigate causes of earthquake damage. The damage level of M school was classified into light with R=88.2%. The result of the dynamic analysis agreed reasonably well with the damage of M school sustained by the 2016 Gyeongju earthquake. This will provide fundamental data for earthquake preparedness measures, such as the seismic rehabilitation of low-rise reinforced concrete buildings in Korea.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.1
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• pp.83-92
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• 1987

Fatigue fracture of reinforced concrete structures are characterized by considerably larger strains and microcracking as compared to fracture of R.C. structures under static loading. The strain of stirrup is increased suddenly by the occuring of inclined crack and the average strain ${\epsilon}_{\omega}$ of all stirrups in a structure at maximum load increase approximately in proportion to log N. The structures critical in longitudinal reinforcement seemed to have an endurance limit of 60~70 percent of static ultimate strengths for 1,000,000 cycles. In this test, the average fatigue strength at 1,000,000 cycles for all structures tested was approximately 65 percent of the static ultimate strength.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.2
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• pp.53-59
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• 2017

In this experimental study, the characteristic of damages on GFRP rebar exposed to high temperature only and immerged in alkaline solution after the exposure to high temperature was analyzed through microscopic image analysis. The found microcrack and pores in resin matrix were quantitatively compared if there was effect of pre-exposure to high temperature. The damages, such as microcrack and pores in resin matrix, by alkali exposure were mainly found in rebar surface. On the other hand, the pores caused by high temperatures were extensively found in a section and had greater width than those caused by the alkali exposure. In results of the quantitative comparison, the accumulated length and widths of microcrack and pores in resin matrix in pre-exposed GFRP rebar to high temperature were respectively 1.5 and 1.4 times of those in the GFRP rebar only immerged in alkali solution. Therefore, the deterioration of resin matrix by the alkali exposure could be accelerated due to the pre-exposure to high temperature.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.1 s.20
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• pp.9-16
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• 2006

The moment resisting frame has been well-known as it had very excellent seismic performance, and it has been widely used and constructed in the design of a lot of buildings. However, the moment resisting frame system did not exert the seismic performance during the earthquake in Northridge and Kobe sufficiently, and it produced the crack or brittle fracture on the joint. this study was to ]m tests with the full-scale test subject as parameters of existence of H-beam web high tensile bolt shearing joint and reinforcement of H-flange rib. This researcher was to anticipate the decrease of number of high tensile bolts and the improvement of workability through the double shear joint by the experiment, and improve the seismic performance through the reinforcement of rib plate. In addition, this study was to prevent the brittle fracture by the stress concentration through the non scallop.

• Journal of Korean Society of Steel Construction
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• v.14 no.4
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• pp.499-508
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• 2002

A simple design method for rib-reinforced seismic steel moment connections has been recently proposed based on the equivalent strut model. An experimental program was implemented to verify the proposed design method, as well as develop the schemes that will prevent cracking at the rib tip where stress concentration was evident. All specimens designed using the proposed method were able to develop a satisfactory connection plastic rotation of 0.04 radian. In addition to rib reinforcement, slight beam flange trimming pushed the plastic hinging and local buckling of the beam away from the rip tip and effectively reduced cracking potential at the rib tip. Using strain gage readings, the strut action of the rib and resulting reverse shear in the beam web were also experimentally identified.