• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.3
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• pp.349-355
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• 2020

The purpose of this study is to investigate the effects of types and amounts of fibers on the compressive strength and tensile behavior high strength fiber-reinforced composites under a static load and impact resistance properties of composites under a high-velocity projectile impact load. Three kinds of mixtures were designed and specimens were manufactured. compressive strength, uniaxial tension, and high velocity projectile impact load tests were performed. Test results showed that the amount of fiber has a greater effect on the tensile strength an d tensile strain capacity than the compressive strength, an d the tensile strain capacity was improved by using hybrid fibers. It was also found that the amount of steel fiber had a great influence on the impact resistance capacity of panels. Although the impact resistance capacity of panels could be improved by using hybrid fibers, the difference of impact resistance capacity between specimens was found to be larger than the case of use of single fiber.

• Journal of the Korean Society for Nondestructive Testing
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• v.17 no.2
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• pp.81-88
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• 1997

Impact behavior of carbon fiber reinforced plastics (CFRP) laminates were evaluated with tension test and compact tension test. A steel ball launched by an air gun collides against CFRP laminates to generate impact damage of relatively low energy. The static tensile and fracture toughness tests were performed to evaluate the residual strength and the AE behavior of impact-damaged laminates. As a results, it was found that the static strength, the fracture toughness and the AE-event count were decreased with increasing of impact velocity and delamination area, and to have a different strength ratio and fracture toughness ratio for each stacking method. And also, it was confirmed that strength and fracture toughness of impact-damaged CFRP laminates could be evaluated and analyzed quantitatively by AE techniques.

• International Journal of Concrete Structures and Materials
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• v.2 no.2
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• pp.123-136
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• 2008

A new plastic-damage constitutive model applicable to lightweight concrete (LWC) and normal weight concrete (NWC) is proposed in this paper based on both continuum damage mechanics and plasticity theories. Two damage variables are used to represent tensile and compressive damage independently. The effective stress is computed in the Drucker-Prager multi-surface plasticity framework. The stress is then computed by multiplication of the damaged part and the effective part. The proposed model is coded as a user material subroutine and incorporated in a finite element analysis software. The constitutive integration algorithm is implemented by adopting the operator split involving elastic predictor, plastic corrector and damage corrector. The numerical study shows that the algorithm is efficient and robust in the finite element analysis. Experimental investigation is conducted to verify the proposed model involving both static and dynamic tests. The very good agreement between the numerical results and experimental results demonstrates the capability of the proposed model to capture the behaviors of LWC and NWC structures for static and impact loading.

• Structural Engineering and Mechanics
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• v.49 no.6
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• pp.775-792
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• 2014

Static loading tests were carried out in this study to investigate the effect of bar cutoff on the resistance of RC beam-column sub-assemblages under column loss. Two specimens were designed with continuous main reinforcement. Four others were designed with different types of bar cutoff in the mid-span and/or the beam-end regions. Compressive arch and tensile catenary responses of the specimens under gravitational loading were compared. Test results indicated that those specimens with approximately equal moment strength at the beam ends had similar peak loading resistance in the compressive arch phase but varied resistance degradation in the transition phase because of bar cutoff. The compressive bars terminated at one-third span could help to mitigate the degradation although they had minor contribution to the catenary action. Among those cutoff patterns, the K-type cutoff presented the best strength enhancement. It revealed that it is better to extend the steel bars beyond the mid-span before cutoff for the two-span beams bridging over a column vulnerable to sudden failure. For general cutoff patterns dominated by gravitational and seismic designs, they may be appropriately modified to minimize the influence of bar cutoff on the progressive collapse resistance.

• Structural Engineering and Mechanics
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• v.85 no.4
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• pp.563-571
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• 2023

Girdling underpinning joints are key areas of concern for the pier-cutting bridge-lifting process. In this study, five specimens of an underpinning joint were prepared by varying the cross-sectional shape of the respective column, the process used to treat the beam-column interface (BCI), and the casting process. These specimens were subsequently analyzed through static failure tests. The BCI was found to be the weakest area of the joint, and the specimens containing a BCI underwent punching shear failure. The top of the girdling beam (GB) was subjected to a circumferential tensile force during slippage failure. Compared to the specimens with a smooth BCI, the specimens subjected to chiseling exhibited more pronounced circumferential compression at the BCI, which in turn considerably increased the shear capacity of the BCI and the ductility of the structure. The GB for the specimens containing a column with a circular cross-section exhibited better shear mechanical properties than the GB of other specimens. The BCI in specimens containing a column with a circular cross-section was more ductile during failure than that in specimens containing a column with a square cross-section.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.1
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• pp.127-130
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• 2010

This paper deals with the formability of DP590 steel considering the strain rate. The strain hardening coefficient, elongation and r-value were obtained from the static and dynamic tensile test. As strain rate increases from static to 100/s, the strain hardening coefficient and the uniform elongation decrease and the elongation at fracture and r-value decrease to 0.1/s and increase again to 100/s. The high speed forming limit tests with hemi-spherical punch were carried out using the high speed crash testing machine and high speed forming jig. The high speed forming limit of DP590(order of $10^2$/s) decreases compared to the static forming limit(order of $10^{-3}$/s) and the forming limit band in high speed forming test is narrower than that in the static forming test. This tendency may be due to the development of brittleness with increase of stain rate.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.4
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• pp.905-915
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• 1998

Static tensile tests using adhesive-bonded single-lap joints of aluminum alloy were conducted to investigate the effect of geometric factor, overlap length, adherend thickness, adhesive thickness and material composition of adherend/adhesive on the strength of adhesive joint. The average applied shear stress at joint fracture decreased with increasing lap length. However increasing the adherend thickness resulted in a higher joint strength. Higher yield strength of adherend and lower elastic modulus of adhesive is advantageous to the adhesive joint. Newly proposed modified joint factor could be well evaluated the influence of lap length, adherend thickness and adhesive thickness on the bond strength for adhesive joints.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.258-261
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• 2006

This study investigates the flexural behavior and strengthening performance of RC beams with unbonded prestressing CFRP laminates through static bending tests. The aluminum anchorage system has been developed in tins study and successfully applied to the test specimens. The prestressing level of CFRP laminatehas was 0 %, 20 %, 30% and 50 % of its tensile strength. Experimental results revealed that RC beams with unbonded prestressing CFRP laminates showed increased crack load and yield load according to the level of prestress. It has also been observed that the length of the CFRP laminates does not have significant effect on the maximum load.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.83-88
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• 2003

In this paper, the medium strength self-compacting concrete with simple mix design method was manufactured and investigated about the properties of flowability and strength. Two types of binders like as fly-ash and RP(rock powder) were contained to the SCC in order to obtain the target medium strength of 270-350kgf/$cm^2$. The experimental tests about slump-flow, reaching time to the slump-flow of 50cm, V-funnel and U-box were carried out in accordance with the specified by the Japanese Society of Civil Engineering(JSCE). The mechanical properties such as compressive strength, splitting tensile strength and static modulus of elasticity were checked with the requirements specified by KS.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.3
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• pp.48-55
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• 1996

The aim of the present study is to investigate the scaling and dynamic erects on the plate cutting response. A series of cutting tests for unstiffened and longitudinally stiffened steel plate specimens in a quasi-static condition were carried out, varying the plate thickness. Based on the previous as well as the present test results, the scaling effect of Plate thickness on the cutting response is investigated. Dynamic erects are also clarified from the devious theoretical and experimental results. The Cowper-Symonds constitutive equation originally derived for mild steel is modified to consider the influence of strain-rate sensitivity on yield strength of high tensile steel.