• Structural Engineering and Mechanics
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• v.65 no.3
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• pp.315-325
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• 2018

This paper predicts the flexural behaviour of reinforced concrete (RC) beams strengthened with a precast strip of ultra-high performance fiber-reinforced concrete (UHPFRC). In the first phase, ultimate load capacity of preloaded and strengthened RC beams by UHPFRC was predicted by using various analytical models available in the literature. RC beams were preloaded under static loading approximately to 70%, 80% and 90% of ultimate load of control beams. The models such as modified Kaar and sectional analysis predicted the ultimate load in close agreement to the corresponding experimental observations. In the second phase, the famous fatigue life models such as Papakonstantinou model and Ferrier model were employed to predict the number of cycles to failure and the corresponding deflection. The models were used to predict the life of the (i) strengthened RC beams after subjecting them to different pre-loadings (70%, 80% and 90% of ultimate load) under static loading and (ii) strengthened RC beams after subjecting them to different preloading cycles under fatigue loading. In both the cases precast UHPFRC strip of 10 mm thickness is attached on the tension face. It is found that both the models predicted the number of cycles to failure and the corresponding deflection very close to the experimental values. It can be concluded that the models are found to be robust and reliable for cement based strengthening systems also. Further, the Wang model which is based on Palmgren-Miner's rule is employed to predict the no. of cycles to failure and it is found that the predicted values are in very good agreement with the corresponding experimental observations.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.1
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• pp.54-63
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• 1997

The purpose of this study is to analyse deformation properties by carrying out of flexure experimentations after fabricating polymer concrete sandwich panels which are composed of the polymer concrete in facing and expanded polystyren in cores, and to provide the basic data necessary to design, fabricate and operate the structure using these polymer concrete sandwich panels The analysed result of this study is summarized as follows. 1. The result of experiment on flexural deflection indicated that the thicker the thickness of both cores and facing of the polymer concrete sandwich panels, the smaller the deflection but the larger the ultimate shear force. In addition, it was also shown that the thicker the thickness of these cores and facing, the smaller the increasing rate of the deflection with the increase of load. 2. The breaking shape of polymer concrete sandwich panels by experiment on flexure was different according to the thickness of facing. When the facing was 5mm in thickness, it was the flexure while it was the flexure and shear failure when the facing was 5mm in thickness. As a result, it seems that the thickness of the facing has a great effect on failure. 3. There were induced not only the related formula between load, deflection and deformation according to the thickness of cores and facing on the basis of the flexure experiment, but also formula between load, horizontal displacement, Then, it seems that it will be possible to estimate the above elements by using these related formulas.

• Structural Engineering and Mechanics
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• v.61 no.1
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• pp.117-124
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• 2017

Load testing is one of the important tests to determine if the structural elements can be used at the intended locations for which they have been designed. It is nothing but gradually applying the loads and measuring the deflections and other parameters. It is usually carried out to determine the behaviour of the system under service/ultimate loads. It helps to identify the maximum load that the structural element can withstand without much deflection/deformation. It will also help find out which part of the element causes failure first. The load-deflection behaviour of the road bridge girder has been studied by carrying out the load test after simulating the field conditions to the extent possible. The actual vertical displacement of the beam at mid span due to the imposed load was compared with the theoretical deflection of the beam. Further, the recovery of deflection at mid span was also observed on removal of the test load. Finally, the beam was checked for any cracks to assert if the beam was capable of carrying the intended live loads and that it could be used with confidence.

• Structural Engineering and Mechanics
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• v.27 no.4
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• pp.501-521
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• 2007

This study presents a model to better understand the shear behavior of reinforced concrete walls subjected to lateral load. The scope of the study is limited to squat walls with height to length ratios not exceeding two, deformed in a double-curvature shape. This study is based on limited knowledge of the shear behavior of low-rise shear walls subjected to double-curvature bending. In this study, the wall ultimate strength is defined as the smaller of flexural and shear strengths. The flexural strength is calculated using a strength-of-material analysis, and the shear strength is predicted according to the softened strut-and-tie model. The corresponding lateral deflection of the walls is estimated by superposition of its flexibility sources of bending, shear and slip. The calculated results of the proposed procedure correlate reasonably well with previously reported experimental results.

• Nuclear Engineering and Technology
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• v.45 no.2
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• pp.223-236
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• 2013

In the present study the behavior of fire and the residual strength of fire-ignited RC slabs are investigated by experimental tests and numerical simulations. The fire tests of RC slabs were carried out in a furnace using the ISO 834 standard fire. The load capacity of the cooled RC slabs that were not loaded during the fire tests was evaluated by additional 3 point bending tests. The influence of the proportion of PP (polypropylene) fibers in the RC slabs on the structural behavior of the RC slabs after the fire loading was investigated. The results of the fire tests showed that the maximum temperature of concrete with PP fiber was lower than that of concrete without PP fiber. As the concrete was heated, the ultimate compressive strength decreased and the ultimate strain increased. The load-deflection relations of RC slabs after fire loading were compared by using existing stress-strain-temperature models. The comparison between the numerical analysis and the experimental tests showed that some numerical analyses were reliable and therefore, can be applied to evaluate the ultimate load of RC slabs after fire loading. The ultimate load capacity after cooling down the RC slabs without PP fiber showed a considerable reduction from that of the RC slabs with PP fiber.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.544-547
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• 2004

Predicting the failure modes of reinforced concrete corbels is difficult because the reinforced concrete corbels show the shapes of sudden shear failures at even slight deflection. For this reason, an exact analysis method is demanded highly. In this study, the validity of the grid softened strut-tie model method suggested for concrete member analysis was examined through the ultimate strength evaluation of the reinforced concrete corbels tested to failure. The evaluated ultimate strengths by the grid softened strut-tie model method were compared with those by the ACI 318-02 and the softened strut-tie model method.

• Structural Engineering and Mechanics
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• v.2 no.2
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• pp.185-196
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• 1994

In this paper a spline function solution for the ultimate strength of steel members and member structures is derived based on total Lagrangian formulation. The displacements of members along longitudinal and transverse directions are interpolated by one-order B spline functions and three-order hybrid spline functions respectively. Equilibrium equations are established according to the principle of virtual work. All initial imperfections of members and effects of loading, unloading and reloading of material are taken into account. The influence of the instability of members on structural behavior can be included in analyses. Numerical examples show that the method of this paper can satisfactorily analyze the elasto-plastic large deflection problems of planar steel member and member structures.

• Journal of Biosystems Engineering
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• v.18 no.1
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• pp.30-36
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• 1993

Cucumbers being living biological materials are generally vulnerable to external forces, especially, bending force during the processes, because they have usually longish shape. Understanding the mechanical and viscoelastic properties of cucumber is important to analyze various characteristics which might be helpful in determining design parameters for the processing equipment such as sorting, packaging and transporting machine. The objectives of this study were to determine ultimate bending strength, deflections, and hysteresis losses for the cucumbers from the bending tests. Within the range of loading rate from 20 to 100mm/min, the ultimate bending strength of the cucumber samples were 525-630kPa at the Gyeousalicheongjang and the Baekdadagi, and 476~618kPa at the Cheongjangmadi, respectively, but the ultimate bending deflection ratio of the Cheongjangmadi showed the highest value among the tested samples. The effect of loading rate on the physical properties of the cucumber was relatively significant, all considered physical properties and degree of elasticity of the cucumber increased with the loading rate, but the hysteresis loss decreased with it.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.885-890
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• 2000

12 RC deep beams with a/d = 1.17 are reported. This paper is to study the effect of vertical and horizontal web reinforcement and web reinforcement arrangement on inclined cracking shear, ultimate shear strength, midspan deflection, and inclined crack width. Test results indicated that web reinforcement produces and arrangement seems to moderately affect inclined cracking shear, ultimate shear strength and crack width. However, addition of horizontal web reinforcement(pv = 0.0085) little or no influence on inclined cracking shear, ultimate shear strength and crack width. The member which vertical and horizontal web reinforcement concentrate on the center web considerably increases in load-carrying capacity.

• Magazine of the Korean Society of Agricultural Engineers
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• v.44 no.1
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• pp.93-102
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• 2002

Steel fiber and polymer are used widely for reinforcement material of RC structures because of its excellences of the durability, serviceability as well as mechanical properties. The purpose of this study is to investigate the shear behavior of polymer cement high strength concrete beams mixed with steel fiber. The compressive strength of concrete was based on the 100$\times$200 mm cylinder specimens. The compressive strength of concrete are 320$kgf/cm^2$, 436 $kgf/cm^2$ and 520 $kgf/cm^2$ in the 28 days. The static test was carried out to measure the ultimate load, the initial load of flexural and diagonal cracking, crack patterns and fracture modes. Also, load-strain and load-deflection examined. During the test cracks were sketched against the load values according to the growth of crack. result are as follows; (1) The failure modes of the specimens are increased in rigidity and durability with mixing steel fiber and polymer. (2) The load of initial crack was similar a theory of shear-crack strength. (3) The deflection and strain at failure load of Polymer-steel fiber high strength concrete beams were increased, improving the brittleness of the high strength concrete.