• 한국구조물진단유지관리공학회 논문집
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• 제5권2호
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• pp.93-102
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• 2001

The objective of this experimental study is to evaluate the strengthening effects of concrete compression confined with Epoxy-boned compound fiber sheets. An analytical model is proposed to construct a stress-strain relationship for confined concrete. Test results are summarized as followed. While non-FRP lateral confinement specimens appeared sudden failure after shell concrete was torn off, specimens confined laterally with FRP were showed that their failure. Specially, Glass fiber lateral confined specimens occurred obviously increase ductility ability. Hence, concrete specimen with lateral confinement by Hi-carborn and Aramide. Glass fiber simultaneously can be increased in not only strength but also a lot of ductility ability.

• Steel and Composite Structures
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• 제25권3호
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• pp.287-298
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• 2017

The present study aims to determine the structural response of full scaled rectangular columns under both of vertical and lateral loads using numerical methods. In the study, the composite columns considering full concrete filled circular steel tube (FCFRST) and concrete filled double-skin rectangular steel tube (CFDSRST) section types are numerically modelled using ANSYS software. Vertical and lateral loads are applied to models to assess the structural response of the composite elements. Also similar investigations are done for reinforced concrete rectangular (RCR) columns to compare the results with those of composite elements. The analyses of the systems are statically performed for both linear and nonlinear materials. In linear static analyses, both of vertical and lateral loads are applied to models as only one step. However in nonlinear analyses, while vertical loads are applied to model as only one step, lateral loads are applied to systems as step by step. The displacement and stress changes in some critical nodes and sections and contour diagrams are reported by graphs and figures. At the end of the study, it is demonstrated that the nonlinear models reveal more accurate result then those of linear models. Also, it is highlighted that composite columns provide more and more safety, ductility compared to reinforced concrete column.

• Coupled systems mechanics
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• 제5권2호
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• pp.127-144
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• 2016

Two dimensional numerical investigations were carried out to study the influence of interface thickness and their pattern on the behavior of reinforced concrete frames subjected to in-plane lateral loads using commercial finite element tool SAP 2000. The linear elastic analysis was carried out on one and two bay structural systems as well as the influence of number of stories was studied by varying the number of stories as single, three and five. The cement mortar was used as interface material and their effect was studied by varying thicknesses as 6, 8, 10, 14 and 20 mm. The interface was recognized as one sided, two sided, three sided and four sided and their effect was studied by removing the interface material between the reinforced concrete frame and masonry infill. The effect of lateral loads on infill masonry wall was also studied by varying assumed loads as 10, 20, 30, 40, 50 and 60 kN. The behavior of infilled frames studied has revealed that there is a maximum influence of interface thickness and interface pattern corresponding to 10 mm thickness. In general, the lateral displacement of frame is increased linearly with increase in lateral loads.

• Steel and Composite Structures
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• 제20권1호
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• pp.57-70
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• 2016

The predominant type of buckling that I-steel concrete composite beams experience in the negative moment area is distortional buckling. The key factors that affect distortional buckling are the torsional and lateral restraints by the bottom flange. This study thoroughly investigates the equivalent lateral and torsional restraint stiffnesses of the bottom flange of an I-steel concrete composite beam under negative moments. The results show a coupling effect between the applied forces and the lateral and torsional restraint stiffnesses of the bottom flange. A formula is proposed to calculate the critical buckling stress of the I-steel concrete composite beams under negative moments by considering the lateral and torsional restraint stiffnesses of the bottom flange. The proposed method is shown to better predict the critical bending moment of the I-steel composite beams. This article introduces an improved method to calculate the elastic foundation beams, which takes into account the lateral and torsional restraint stiffnesses of the bottom flange and considers the coupling effect between them. The results show a close match in results from the calculation method proposed in this paper and the ANSYS finite element method, which validates the proposed calculation method. The proposed calculation method provides a theoretical basis for further research on distortional buckling and the ultimate resistance of I-steel concrete composite beams under a variable axial force.

• Geomechanics and Engineering
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• 제32권6호
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• pp.567-581
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• 2023

Enhanced vertical load capacity of the ground reinforced with the stone columns drew great attention by the researchers as it deals with many of the geotechnical difficulties associated with the weak ground. Recently, it has been found that the stone columns are also prone to fail under the shear load when employed beneath the embankments or the foundations susceptible to lateral loads. In this study, the effect of various encasement conditions on the lateral deflection of stone columns is investigated. A method of dual layers of encasement has been introduced and its the effect on lateral load capacity of the stone columns has been compared with those of the single encased stone column and the un-encased stone columns. Large shear box tests were utilised to generate the shear deformation on the soil system under various normal pressure conditions. The stiffness of the soil-stone column combined system has been compared for various cases of encasement conditions with different diameters. When subjected to lateral deformation, the encased columns outperformed the un-encased stone columns installed in loose sand. Shear stress resistance is up to 1.7 times greater in dual-layered, encased columns than in unencased columns. Similarly, the secant modulus increases as the condition changes from an unencased stone column to single-layer encasement and then to dual-layer encasement, indicating an improvement in the overall soil-stone column system.

• 한국정밀공학회지
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• 제29권12호
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• pp.1296-1303
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• 2012

There is a certain limit to reproduce phenomena between the real vehicle and road, since the existing methods to verify durability of the wheel are mostly uni-axial tests. And the change of durability of the wheel can't be predicted since these tests don't consider the camber angle and lateral force as important factors. In this paper, the FE models of the wheel-tire and drum are created. Then, the vertical and lateral loads are applied to wheel-tire assembly and the camber angle is applied by inclining the wheel-tire assembly to the drum. Based on the analysis result, the crack position is predicted to be created in the body of the wheel. The variation of the stress according to the camber angle is verified and the maximum spot of the stress changes continually.

• KCI Concrete Journal
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• 제13권1호
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• pp.69-78
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• 2001

The inelastic behavior of a reinforced concrete columns is influenced by a number of factors : 1) level of axial load, 2) tie spacing, 3) volumetric ratio of lateral steel, 4) concrete strength, 5) distribution of longitudinal steel, 6) strength of lateral steel, 7) cover thickness, 8) configuration of lateral steel, 9) strain gradient, 10) strain rate, 11) the effectively confined concrete core area, and 12) amount of longitudinal steel. A new constitutive model of a confined concrete is suggested in order to investigate the nonlinear behavior of the reinforced concrete columns under concentric loading. The developed constitutive model for the confined concrete takes into account the effects of effectively confined area as well as the horizontal and longitudinal distributions of the confining pressures. None of the existing models incorporated these two main effects at the same time. A total of different six constitutive models for the behavior of the confined concrete under concentric compression were compared with the sixty-one test results reported by different researchers. The superiority of the developed model in its accuracy is demonstrated by evaluating the error function, which compares the weighted averages for the sum of squared relative differences in peak compressive strength and corresponding strain, stress at strain equal to 0.015, and total area under stress-strain curve up to strain equal to 0.015.

• Steel and Composite Structures
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• 제32권2호
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• pp.199-212
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• 2019

This paper presents an investigation on seismic behavior of out-of-code Q690 circular high-strength concrete-filled thin-walled steel tubular (HCFTST) columns made up of high-strength (HS) steel tubes (yield strength $f_y{\geq}690MPa$). Eight Q690 circular HCFTST columns with various diameter-to-thickness (D/t) ratios, concrete cylinder compressive strengths ($f_c$) and axial compression ratios (n) were tested under the constant axial loading and reversed cyclic lateral loading. The obtained lateral load-displacement hysteretic curves, energy dissipation, skeleton curves and ductility, and stiffness degradation were analyzed in detail to reflect the influences of tested parameters. Subsequently, a simplified shear strength model was derived and validated by the test results. Finally, a finite element analysis (FEA) model incorporating a stress triaxiality dependent fracture criterion was established to simulate the seismic behavior. The systematic investigation indicates the following: compared to the D/t ratio and axial compression ratio, improving the concrete compressive strength (e.g., the HS thin-walled steel tube filled with HS concrete) had a slight influence on the ductility but an obvious enhancement of energy dissipation and peak load; the simplified shear strength model based on truss mechanism accurately predicted the shear-resisting capacity; and the established FEA model incorporating steel fracture criterion simulated well the seismic behavior (e.g., hysteretic curve, local buckling and fracture), which can be applied to the seismic analysis and design of Q690 circular HCFTST columns.

• 한국지반공학회논문집
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• 제25권2호
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• pp.37-44
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• 2009

본 연구에서는 대표적인 원위치현장시험인 CPT의 콘관입치 $q_c$ 값을 이용하여 말뚝의 극한수평단위지지력과 극한수평지지력을 산정하는 예측식들을 제안하고, 검증하였다. 일반적으로 기존 극한수평단위지지력과 극한수평지지력은 사질토지반에서 중요한 요소인 상대밀도, 연직응력, 그리고 다양한 토압계수들에 대한 함수로 표현하여 왔다. 하지만 이들은 수평음력에 대한 영향을 고려하지 않았으며, 말뚝 주변지반이 단 일층으로 구성되어 있다고 가정하여 실제 현장에서의 영향을 고려하지 않았다. 따라서 본 연구에서는 이에 대한 영향을 고려할 수 있는 CPT 결과를 이용한 극한수평단위지지력 산정식과 극한수평지지력을 산정하는 방법을 제안하였다. 이는 순수사질토에 대상으로 하고 있으며, 그에 대한 해석을 위해 적합한 대상지반을 대상으로 제안된 산정식의 신뢰성을 확보하였다.

• 한국재난정보학회 논문집
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• 제12권1호
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• pp.40-46
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• 2016

Nowdays, adjacent loading bringing enormous harm to the existing bridge in engineering construction. In this paper, the influencing mechanism of adjacent loading to pier and Law of displacement of pier is researched through living examples, and the safe influence area has been defined. Research shows that: the main damages to piers is caused by the side loading; lateral displacement index of pier top surface is more conservative than the pier additional stress index; it is secure when the distance of adjacent load is 0.5 times of the height of accumulation or 6m, otherwise it would be very scary, and the monitoring measure is necessary.