• Computers and Concrete
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• v.34 no.4
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• pp.393-408
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• 2024

In recent decades the strengthening of reinforced concrete (RC) structural elements using Fiber-reinforced polymer (FRP) has received much attention. The behavior of RC elements can vary from axial compression to pure bending, depending on their loading. When the compressive behavior is dominant, the FRP jacket application is common, but when the flexural behavior is prevalent, the codes consider the FRP jacket ineffective. Codes suggest applying FRP bars or strips as Near-surface Mounted (NSM) or Externally Bonded (EB) in the tensile face to strengthen the beams under flexure. To strengthen the columns in tension-control mode, some researchers have suggested NSM FRP bars in both tension and compression faces alone or with the FRP jacket (hybrid). However, the number of tests that evaluate the pure bending of the strengthened columns as one of the pivotal points of the axial force-moment interaction curve is limited. In this paper, 11 RC elements strengthened using the NSM (in both tension and compression faces) or hybrid method were subjected to bending to assess the effect of the amount and material type of the FRP bar and jacket and the dimensions of the groove. The test results revealed that the NSM method increased the flexural capacity of the members between 10% to 50%. Furthermore, using the hybrid method increased the capacity between 51% to 91%. Finally, an analytical model was presented considering the effect of the NSM FRP bond in different circumstances, and its results were in good agreement with the experimental results.

• Journal of the Korean Wood Science and Technology
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• v.46 no.1
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• pp.85-92
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• 2018

In order to use glued built up timber beam as a structural member for post and beam construction, it must be possible to manufacture long-span lumber. In this study, the researchers conducted a performance evaluation for longitudinal bonding of lumber (cross-section $89{\times}120mm$) made from larch. The specimens were prepared in six different forms using the longitudinal bonding method. The bonding strength of these specimens was tested through tensile strength tests and bending strength tests. The tensile strength test result of the longitudinally bonded parts was better than that of the double lap specimens. And, the tensile strength value of the scarf specimen was better than that of the hooked scarf specimen. The tensile strength of the GFRP (Glass Fiber Reinforced Plastic) rod insertion bonding specimen was 3.6 MPa, which was the highest. As for the bending strength test result of the longitudinally bonded part, the average MOR (modulus of rupture) of the specimen where a GFRP rod was inserted and bonded measured 29 MPa, while the specimens of other bonded parts showed a MOR no more than 11 MPa. Toughness destruction was observed in specimens where a GFRP rod was insertion-bonded. The rest of the specimens showed brittle destruction. The average MOR strength of the Rod + Lap specimen was 30.5 MPa, which was the highest among all longitudinally bonded specimens. The bending strength of the Rod + Lap specimens showed an effective strength that was 66% of that of the control group which were not longitudinally bonded.

• Journal of the Korean Geotechnical Society
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• v.27 no.3
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• pp.63-73
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• 2011

The behavior of laterally cyclic loaded piles is affected by the magnitude and number of cycles of cyclic lateral loads as well as loading method (1-way or 2-way loading). In this study, calibration chamber tests were carried out to investigate the effects of loading method of cyclic lateral loads on the behavior of piles driven into sand. Results of the chamber tests show that the permanent lateral displacement of 1-way cyclic loaded piles is developed in the same direction as the first loading, whereas that of 2-way cyclic loaded piles is developed in the reverse direction of the first loading. 1-way cyclic lateral loads cause a decrease of the ultimate lateral load capacity of piles, and 2-way cyclic lateral loads cause an increase of the ultimate lateral load capacity of piles. The change of ultimate lateral load capacity with loading method of cyclic lateral loads increases with increasing number of cycles. It is also observed that the 1-way cyclic loads generate greater maximum bending moment than 2-way cyclic loads for piles in cyclic loading step and generates smaller maximum bending moment for piles in the ultimate state. It can be attributed to the difference in compaction degree of the soil around the piles with loading method of cyclic lateral loads. In addition, it is founded that 1-way and 2-way cyclic lateral loads cause a decrease in the maximum bending moment of piles in the ultimate state compared with that of piles subjected to only monotonic loads.

• Journal of the Korean Wood Science and Technology
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• v.31 no.5
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• pp.72-79
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• 2003

In reliability based design(RBD) method, the distribution characteristics of mechanical properties of material are basic input variable. Therefore, distribution type and parameters of mechanical properties should be determined accurately. Until now, the properties were derived from tests with small, clear specimens. However, the test conditions should emulate as nearly as possible the way in which the timber would be used in practice and the test results should, as closely as possible, reflect the structural end use conditions to which the timber products would be subjected. In this study, structural timbers (38mm by 140mm, 3.0m long) were graded by visual assessment of growth characteristics and defects. And then bending tests were conducted on 498 structural size timbers. For each grade, the distribution type and the parameters of mechanical properties were determined for each grade. For the determination of best-fit distribution type, comparing of square error between distribution types and KS test were conducted. Best-fit distribution type of bending strength(MOR) is weibull distribution for all grade. In case of MOE, normal distribution is best-fit.

• Journal of the Korean Geotechnical Society
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• v.22 no.2
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• pp.5-17
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• 2006

In order to investigate the stabilizing effect of nails against sliding, a series of model tests were carried out. The apparatus of model test was designed to perform the model test of soil slope reinforced by nails. The instrumentation system was used to measure the deflection behavior of nails during slope failure. As a result of model tests, the quantity and the occurred position of the maximum bending stress are changed according to the area ratio and the inclination angles of nails. The maximum stabilizing effect against sliding of nails is presented at 0.7$\%$ of the area ratio because the biggest maximum bending stress occurs at this time. But, the stabilizing effect of nails decreases with more than 0.7$\%$ of the area ratio. In the same condition of the area ratio, the stabilizing effect of nails is excellent at -10$^{circ}$ of the inclination angles of nails. The sliding surface can be predicted on the basis of the position of the maximum bending stress in each nails. The shape and depth of sliding surface are changed according to the area ratio and the inclination angles of nails.

• Journal of the Korean Geotechnical Society
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• v.26 no.12
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• pp.41-50
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• 2010

The behavior of laterally cyclic loaded piles is different from that of piles under monotonic loading and depends on soil and load characteristics. In this study, model pile load tests were performed using a calibration chamber to investigate the effects of load characteristics on the behavior of laterally cyclic loaded piles in sand. Results of the model tests show that the ultimate lateral load capacity of laterally cyclic loaded piles decreases linearly with increasing the number of cycles and increases slightly with increasing the magnitude of cyclic lateral loads. When the piles reach the ultimate state, the maximum bending moment developed in the piles decreases linearly with increasing the number of cycles and it occurs at a depth of 0.36 times pile embedded length for all the number of cycles. However, both the magnitude and depth of the maximum bending moment of piles in the ultimate state increase slightly as the magnitude of cyclic lateral loads increases. It is also observed that the cyclic lateral loading generates a decrease in the ultimate lateral load capacity and maximum bending moment for piles in the ultimate state. In addition, based on the model test results, a new empirical equation for the ultimate lateral load capacity of laterally cyclic loaded piles in dense sand is also proposed. A comparison between predicted and measured load capacities shows that the proposed equation reflects satisfactorily the model test results.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.665-670
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• 1998

This study was carried out to investigate quantitatively the relationship between the degree of rebar corrosion and the strength of reinforced concrete beams. After producing equations for the relationship between both the tensile properties of rebars and bond properties and the corrosion percentage of rebars. Finite element analysis and bending tests were conducted for RC beams damaged by corrosion of tension main rebar. As a result, it was made that the strength of RC beams damged by corrosion could be practically simulated by FEM using experimentally determined material representing the bond properties and the mechanical properties of corroded rebars.

• Composites Research
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• v.13 no.3
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• pp.1-8
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• 2000

Excellent environmental durability and handy installation procedure as well as high specific strength and stiffness have introduced fiber-reinforced polymeric composite materials into the civil and architectural engineering field. This study presents the considerably enhanced strength characteristics of the mortal beams by being reinforced with epoxy-bonded carbon fiber sheets(CFS). Three point bending and Charpy impact tests were performed on both of bare and reinforced mortar specimens. The influences of length, and the number of reinforcing plies were investigated. Strength reduction due to pre-existent notch was lessened dramatically. The acoustic emission(AE) measurement revealed the progressive damage process in reinforced specimens.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.479-484
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• 2000

An experimental study to investigate the structural performance of reinforced concrete beams repaired by Polymer Cementitous Mortar in the tension zone is described. Preliminary trials with beams in which beams tensile reinforcing steel was exposed over 100%, 80% and 60% of their length have led to tests on $5\times25$cm beams over a 200cm span to examine the experimental parameter. Attention is concentrated upon overall bending capacity, deflection and crack development of repaired beams.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05a
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• pp.546-549
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• 2006

A series of seismic tests was carried out using piezoelectric elements called "bender elements". A pair of bender elements can be used as a source and a receiver respectively to measure dynamic properties of concrete. The most suitable bender elements were developed and implemented to measure P wave velocity changes due to the cracks of a concrete beam caused by bending.