• Journal of the Korean Society of Safety
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• v.27 no.5
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• pp.141-147
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• 2012

Recently, the external prestressed concrete structures are increasingly being built. The mechanical behavior of prestressed concrete beams with external tendon is different from that of normal bonded PSC beams in that the increment of tendon stress was derived by whole member behavior. By this reason, the ultimate stress of external tendon is smaller than that of bonded tendon or internal unbonded tendon. The purposes of the present paper are therefore to improve the mechanical behavior of external unbonded tendon by using partially bonded external tendon and to evaluate the flexural behavior of partially bonded external tendon by the flexural member experiment. From the experimental results, before flexural cracking, there was no difference between external unbonded, partially bonded and bonded tendons. However, after cracking, yielding load of reinforcement, ultimate load, and tendon stress were increased in the sequence of external unbonded, partially bonded and bonded tendon members. The equation of ACI-318 and AASHTO 1994 were not matched with test results and had no correlations. So the newly proposed equation will be needed including the consideration of tendon profile, tendon bonded type, and so on. The proposed partially bonded external tendon in this paper will be a effective basis for the evaluation of external tendons in construction and design.

• Structural Engineering and Mechanics
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• v.50 no.6
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• pp.709-722
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• 2014

Ultra-High Performance Concrete (UHPC) is an innovative new material that, in comparison to conventional concretes, has high compressive strength and excellent ductility properties achieved through the addition of randomly dispersed short fibers to the concrete mix. This study presents the results of an experimental investigation on the behavior of axially loaded UHPC short circular columns wrapped with Carbon-FRP (CFRP), Glass-FRP (GFRP), and Aramid-FRP (AFRP) sheets. Six plain and 36 different types of FRP-wrapped UHPC columns with a diameter of 100 mm and a length of 200 mm were tested under monotonic axial compression. To predict the ultimate strength of the FRP-wrapped UHPC columns, a simple confinement model is presented and compared with four selected confinement models from the literature that have been developed for low and normal strength concrete columns. The results show that the FRP sheets can significantly enhance the ultimate strength and strain capacity of the UHPC columns. The average greatest increase in the ultimate strength and strain for the CFRP- and GFRP-wrapped UHPC columns was 48% and 128%, respectively, compared to that of their unconfined counterparts. All the selected confinement models overestimated the ultimate strength of the FRP-wrapped UHPC columns.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.2
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• pp.78-85
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• 2003

This study aims to investigate the effect of partially distributed loads on the static behavior of parabolic arches by using the elastic-plastic finite element model. For this purpose, the vertical, the radial, and the anti-symmetric load cases are considered, and the ratio of loading range and arch span is increased from 20% to 100%. Also, the elastic-visco-plastic analysis has been carried out to estimate the elapse time to reach the stable state of arches when the ultimate load obtained by the finite element analysis is applied. It is noted that the ultimate load carrying capacities of parabolic arches are 6.929 tf/$m^2$ for the radial load case, and 8.057 tf/$m^2$ for the vertical load case. On the other hand, the ultimate load is drastically reduced as 2.659 tf/$m^2$ for the anti-symmetric load case. It is also shown that the maximum ultimate load occurs at the full ranging distributed load, however, the minimum ultimate loads of the radial and vortical load cases are obtained by 2.336 tf/$m^2$, 2.256 tf/$m^2$, respectively, when the partially distributed load is applied at the 40% range of full arch span.

• Journal of Industrial Technology
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• v.17
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• pp.111-118
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• 1997

This thesis is an experimental research of investigating behavior of single pile, subjected to the vertical compression loads, using the centrifuge facility located in the geotechnical engineering laboratory in Kangwon National University. Centrifugal model experiments of model pile were carried out changing diameter of model pile, relative density of sandy ground and the gravitational level applied in the centrifuge. Thus, their effects on the load-settlement behavior and the ultimate bearing capacity of pile were investigated. Experimental results obtained from centrifuge model tests were compared with the theoretical or semi-empirical equations to analyze values of ultimate bearing capacity of model pile. When we compare the ultimate bearing capacity of experimental results with the ultimate bearing capacity of theorical results, the experimental results appear more higher in the De Beer method and Meyerhof. Expecially, Terzaghi method is very same as the experimental results normally.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.897-902
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• 2001

The purpose of this experimental study is to investigate the shear behavior of high-strength concrete deep beam and to grasp the conservatism of ACI Building Code. Experimental results on 12 deep beams under two equal symmetrically placed point loads are reported. Main variables are vertical and horizontal web reinforcement and shear span-to-overall depth ratio. Test results indicated that web reinforcement dose not affect on formation of inclined cracks but shear span-to-overall depth ratio affect on inclined shear cracks and ultimate shear strength. Addition of vertical web reinforcement improves ultimate shear strength of H.S.C. deep beams that shear span-to-overall depth ratio is 1.0. Considerable increase in ultimate shear strength of H.S.C. deep beams with increasing horizontal web reinforcement that shear span-to-overall depth ratio is 0.5. Especially with increasing concrete strength($f_{ck}$) the ACI code is conservative in estamating the ultimate shear strength of deep beams.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.533-538
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• 2009

Ultimate lateral loaded pile capacity is influenced by soil conditions. Methods of calculating ultimate lateral loaded pile capacity in homogeneous soil were suggested by a lot of previous researchers.(Broms 1964, Petrasovits & Award 1972, Prasad & Chari 1999) There is only few homogeneous soil in actual condition, however, it could be not conviction that the methods from previous researchers are correct in multi-layered soil. In this study, ultimate lateral capacities were estimated from artificial multi-layered soils and were measured from lateral load test that were composed by various soil conditions. The influence of layered soil conditions were confirmed by comparing with two results.

• Structural Engineering and Mechanics
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• v.22 no.2
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• pp.223-240
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• 2006

Taking into account the geometrical and material nonlinearities, an ultimate behavior of reinforced concrete cooling tower shell in hyperbolic configuration is presented. The design wind pressures suggested in the guidelines of the US (ACI) and Germany (VGB), with or without the effect of internal suction, are employed in the analysis to examine the qualitative and quantitative characteristics of each design wind pressure. The geometrical nonlinearity is incorporated by the Green-Lagrange strain tensor. The nonlinear features of concrete, such as the nonlinear stress-strain relation in compression, the tensile cracking with the smeared crack model, an effect of tension stiffening, are taken into account. The biaxial stress state in concrete is represented by an improved work-hardening plasticity model. From the perspective of quality of wind pressures, the two guidelines are determined as highly correlated each other. Through the extensive analysis on the Niederaussem cooling tower in Germany, not only the ultimate load is determined but also the mechanism of failure, distribution of cracks, damage processes, stress redistributions, and mean crack width are examined.

• Architectural research
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• v.26 no.2
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• pp.31-39
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• 2024

The numerical study focuses on the analysis of the structural behavior of concrete beams containing outdated concrete and offers an innovative method of strengthening them using carbon-fiber-reinforced polymer sheets (CFRP). The focus is on modeling and analyzing the performance of aged concrete beams strengthened by CFRP in the flexural direction. This study presents an ultimate load model for CFRP-strengthened RC beams featuring outdated concrete layers. Validation through four-point bending tests and finite element modeling demonstrated the efficacy of the model. Findings indicate that CFRP sheets significantly enhance beam strength, particularly in structures with outdated concrete layers, resulting in increased ultimate load capacity. Moreover, an inverse relationship between ultimate load and concrete layer height was observed, with the CFS-21-15-30 sample exhibiting the most substantial reduction. Validation of the model was achieved using finite element analysis con-ducted in Abaqus software.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.262-269
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• 2004

Ship structures are basically an assembly of plate elements and the load-carrying capacity or the ultimate strength is one of the most important criteria for safety assessment and economic design. Also, Structural elements making up ship plated structures do not work separately, resulting in high degree of redundancy and complexity, in contrast to those of steel framed structures. To enable the behavior of such structures to be analyzed, simplifications or idealizations must essentially be made considering the accuracy needed and the degree of complexity of the analysis to be used. On this study, to investigate effect of analysis range, the finite element method are used and their results are compared varying the analysis ranges. The model has been selected from bottom panels of large merchant ship structures. For FEA, three types of structural modeling are adopted in terms of the extent of the analysis. The purpose of the present study is to numerically calculate the characteristics of ultimate strength behavior according to the analysis ranges of stiffened panels subject to uniaxial compressive loads.

• Advances in nano research
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• v.15 no.1
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• pp.59-65
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• 2023

In this present article, the mechanical behavior of single-walled black phosphorene nanotubes (SW-αPNTs) is simulated using molecular dynamics (MD). The proposed model is subjected to the axial loading and the effects of morphological parameters, such as the mono-vacancy defect and strain rate on the tensile behavior of the zigzag and armchair SW-αPNTs are studied as a pioneering work. In order to assess the accuracy of the MD simulations, the stress-strain response of the current MD model is successfully verified with the efficient quantum mechanical approach of the density functional theory (DFT). Along with reproducing the DFT results, the accurate MD simulations successfully anticipate a significant variation in the stress-strain curve of the zigzag SW-αPNTs, namely the knick point. Predicting such mechanical behavior of SW-αPNTs may be an important design factor for lithium-ion batteries, supercapacitors, and energy storage devices. The simulations show that the ultimate stress is increased by increasing the diameter of the pristine SW-αPNTs. The trend is identical for the ultimate strain and stress-strain slope as the diameter of the pristine zigzag SW-αPNTs enlarges. The obtained results denote that by increasing the strain rate, the ultimate stress/ultimate strain are respectively increased/declined. The stress-strain slope keeps increasing as the strain rate grows. It is worth noting that the existence of mono-atomic vacancy defects in the (12,0) zigzag and (0,10) armchair SW-αPNT structures leads to a drop in the tensile strength by amounts of 11.1% and 12.5%, respectively. Also, the ultimate strain is considerably altered by mono-atomic vacancy defects.