도넛형 이방향 중공슬래브 뚫림전단 강도 및 파괴거동에 대한 실험적 연구

정주홍(Chung, Joo-Hong),윤주리(Yoon, Ju-Ri),이승창(Lee, Seung-Chang),최창식(Choi, Chang-Sik) 대한건축학회 2014 大韓建築學會論文集 : 構造系 Vol.30 No.4

This paper presents the punching shear strength and failure behavior of biaxial hollow slab with donut type hollow-shaper. Until now, various types of slab systems which can reduce self-weight of slabs have been studied as the height and width of building structures rapidly increase. A biaxial hollow slab system is widely known as one of the effective slab system which can reduce self-weight of slab. According to previous studies, the biaxial hollow slab has weakness in slab-column connection compared with solid slab. And previous studies pointed out reduced cross-section area of concrete by hollows as the cause. It is assumed in this study that the shape of hollows and the location of hollow-shaper exert influence on the punching shear strength of biaxial hollow slabs. Therefore, donut type hollow-shaper which was suggested as the optimal hollow shape in previous study was used in this study. To verify the punching shear strength and failure behaviour of donut type biaxial hollow slab, punching shear tests were conducted. 4 test specimens were used for test parameters. One was conventional RC slab and 3 were hollow slabs. The test parameter was the area of critical section which were determined by the number of hollow-shaper around the column. The punching shear strength of the donut type biaxial hollow slabs are 87%∼103% of solid slabs and superior to generic biaxial hollow slabs. And punching shear cracks occurred at the first perimeter line of donut type hollows.

Performance assessment of advanced hollow RC bridge column sections

김태훈,H.Y. Kim,S.H. Lee,J.H. Lee,신현목 사단법인 한국계산역학회 2015 Computers and Concrete, An International Journal Vol.16 No.5

This study investigates the performance of advanced hollow reinforced concrete (RC) bridge column sections with triangular reinforcement details. Hollow column sections are based on economic considerations of cost savings associated with reduced material and design moments, as against increased construction complexity, and hence increased labor costs. The proposed innovative reinforcement details are economically feasible and rational, and facilitate shorter construction periods. We tested a model of advanced hollow column sections under quasi-static monotonic loading. The results showed that the proposed triangular reinforcement details were equal to the existing reinforcement details, in terms of the required performance. We used a computer program, Reinforced Concrete Analysis in Higher Evaluation System Technology (RCAHEST), for analysis of the RC structures; and adopted a modified lateral confining effect model for the advanced hollow bridge column sections. Our study documents the testing of hollow RC bridge column sections with innovative reinforcement details, and presents conclusions based on the experimental and analytical findings. Additional full-scale experimental research is needed to refine and confirm the design details, especially for the actual detailing employed in the field.

Behavior of CFRP Strengthened CHS under Axial Static and Axial Cyclic Loading

A. Punitha Kumar,R. Senthil 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.4

Fibre Reinforced Polymer (FRP) wrapping is one of the techniques used to strengthen the concrete structures. Recently these techniques are implemented for the strengthening of steel structures. This study emphasizes on experimental investigation of Carbon Fibre Reinforced Polymer (CFRP) strengthened steel hollow sections under axial static and axial cyclic loading. In CFRP strengthened steel hollow section, number of layers and orientation of layers are the key factors for the prediction of axial capacity. A series of tests were conducted on CFRP strengthened steel Circular Hollow Sections (CHS) by varying the number and orientation of the CFRP layers under axial static and axial cyclic loading. From the experimental results, it was observed that the strength, ductility and stiffness has increased in the CFRP strengthened specimens. The results highlight that the axial load carrying capacity of CFRP strengthened circular hollow steel section has been increased up to 37.13% in static loading and 42.86% in axial cyclic loading. CFRP confinement could be responsible for the increase in the axial capacity of steel hollow section and this method could be used to enhance the performance of existing steel hollow sections.

A Unifi ed Theory for Distortion Analysis of Thin-Walled Hollow Sections

Xun Xu,Huawen Ye,De-Yi Zhang,Shizhong Qiang 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.3

A novel unifi ed theory for distortion analysis of thin-walled hollow section has been proposed based on the Hellinger– Reissner variational principle to account for distortional shear deformation eff ects. Based on the proposed theory, a fi nite segment model has been developed and the method for determining the distortion functions of the cross-section has been proposed. The rationality of approaches for determining distortional shear stress has been analysed and it is concluded that Bredt’s pure distortion does not exist in the single-cell hollow section. Comparisons and analyses have been performed between the proposed theoretical model and the existing four groups of theories in distortion analysis of thin-walled hollow section. Eff ects of distortional warping shear stress on the shear deformation has been investigated and the results indicate that the distortional shear deformation eff ect results in a decrease of the distortional warping stresses and shear stresses but an increase of the transverse bending stresses. The numerical study indicates that the distortional shear deformation eff ects can be ignored and the fi rst derivative of the distortion angle can be employed as the distortional warping function for the conventional hollow sections of bridge structures.

Axial compressive behaviour of stub concrete-filled columns with elliptical stainless steel hollow sections

X. Dai,D. Lam 국제구조공학회 2010 Steel and Composite Structures, An International J Vol.10 No.6

This paper presents the axial compressive behaviour of stub concrete-filled columns with elliptical stainless steel and carbon steel hollow sections. The finite element method developed via ABAQUS/Standard solver was used to carry out the simulations. The accuracy of the FE modelling and the proposed confined concrete stress-strain model were verified against experimental results. A parametric study on stub concrete-filled columns with various elliptical hollow sections made with stainless steel and carbon steel was conducted. The comparisons and analyses presented in this paper outline the effect of hollow sectional configurations to the axial compressive behaviour of elliptical concrete-filled steel tubular columns, especially the merits of using stainless steel hollow sections is highlighted

횡방향철근이 감소된 중공사각단면 교각의 내진거동 특성

선창호,김익현 한국지진공학회 2009 한국지진공학회논문집 Vol.13 No.3

콘크리트 교량의 합리적인 내진설계는 지진이 발생할 때 연성파괴메커니즘이 유도될 수 있도록 적절하게 교각 연성도를 확보하는 것이다. 현행 기준에서는 이를 위해 휨모멘트의 설계지진력을 산정할 때 응답수정계수를 도입하고 있으며, 연성도 확보를 위한 횡방향철근량을 규정하고 있다. 그러나, 이러한 내진규정은 일반적으로 단면이 크게 설계되는 우리나라에서는 횡방향철근이 과다하게 산정되는 비합리적이었다. 이를 개선하기 위해 소요연성도에 기반한 새로운 내진설계법이 제안되었으나 거동특성과 횡방향철근의 유효구속력이 다른 중공단면에 적용하기 위해서는 향후 많은 검증과 보완이 필요하다. 이에 본 연구에서는 축방향철근의 겹침이음과 횡방향철근량을 변수로 한 중공단면기둥을 제작하여 준정적 재하실험을 수행하였으며 다양하게 내진거동특성을 분석하고 내진성능을 확인하였다. 본 연구 결과는 향후 중공단면교각의 연성도(성능)기반 내진설계를 위한 기초자료로 제공될 수 있다. The seismic design concept of RC bridges is to attain the proper ductility of piers, yielding a ductile failure mechanism. Therefore, seismic design force for moment is determined by introducing a response modification factor (R), and lateral reinforcements to confine core concrete are specified in the current design code. However, these design provisions have irrationality, which results in excessive amounts of lateral reinforcements for columns in Korea, which are generally designed with large sections. To improve on these provisions, a new design method based on seismic performance has been proposed. To apply this to hollow sectional columns, however, further investigations and improvements must be performed, due to the different seismic behaviors and confinement effects. In this study, hollow sectional columns with different lap-splice of longitudinal bars and lateral reinforcements have been tested. Seismic characteristics and performance were investigated quantitatively. These research results can be used to derive a performance-based design for hollow sectional columns.

Residual stress of cold-formed thick-walled steel rectangular hollow sections

Xingzhao Zhang,Su Liu,Mingshan Zhao,Sing-Ping Chiew 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.22 No.4

This paper presents the experimental and numerical study on the distribution of transverse and longitudinal residual stresses in cold-formed thick-walled structural steel rectangular hollow sections manufactured by indirect technique. Hole-drilling method is employed to measure the magnitude of the transverse and longitudinal surface residual stress distribution, and the effects of the residual stresses are evaluated qualitatively by sectioning method. It is shown that compared to normal cold-formed thin-walled structural hollow sections (SHS), the coldformed thick-walled SHS has similar level of residual stress in the flat area but higher residual stresses in the corner and welding areas. Both the transverse and longitudinal residual stresses tend to open the section. In order to predict the surface residual stresses in the corners of the cold-formed thick-walled SHS, an analytical model is developed. 2D finite element simulation of the cold bending process is conducted to validate the analytical approach. It is shown that in analyzing bending for thick-walled sections, shifting of neutral axis must be considered, since it would lead to nonlinear and non-symmetrical distribution of stresses through the thickness. This phenomenon leads to the fact that cold-formed thick-walled SHSs has different distribution and magnitude of the residual stresses from the cold-formed thin-walled SHSs.

일방향 중공 슬래브의 구조성능 평가에 대한 실험적 연구

김동백,송대겸,최정호,조현상 한국재난정보학회 2018 한국재난정보학회 논문집 Vol.14 No.3

연구목적: 최근 기반시설물이 대형화 됨에 따라 콘크리트 구조물의 경우는 중량감소를 위 하여 중공 슬래브가 대안의 하나로 제시되고 있다. 연구방법: 중공부재의 시공 시 부력으로 인하여 시공이 어려운 점과 콘크리트 단면적이 줄 어 전단성능이 부족하게 되는 구조적인 단점이 있으므로, PVC관과 같은 중공체를 이용하 여 일방향 슬래브를 제작하고 시공성과 구조성능을 검토하는 실험을 실시하였다. 연구결과: PVC관을 이용한 일방향 중공슬래브의 경우 부력방지장치를 이용하면 타설 시 발생하는 중공체의 부상 및 침강을 예방하여 시공성능이 크게 개선되었으며, 휨 및 전단성 능도 적합한 성능을 가진 것으로 확인되었다. 결론: 중공율과 휨성능은 큰 관계가 없지만 중공율이 큰 경우는 항복 후 2차 강성이 낮으므 로 이에 대한 고려가 필요하며, 중공율의 증가에 따른 전단성능의 감소는 전단철근을 배근 하면 보완될 수 있을 것으로 사료된다. Purpose: Recently, As the size of the structure increased, the necessity of reducing its weight was raised. To reduce weight In concrete structures, a hollow slab is proposed as an alternative for weight reduction effect. Method: It is difficult to construct the hollow body due to buoyancy, and the shear performance is insufficient due to the decreased cross section. Slabs were fabricated using unidirectional hollow bodies such as PVC pipes, and experiments were conducted about construction performance and structural performance. Results: The buoyancy preventive device has been improved the construction performance by preventing floating hollow body, it has been confirmed that it has adequate performance to be used as a hollow slab system because it has enough expected shear performance. Coclusion: Hollow ratio has a little connection with bending performance, but after the yielding load, it is necessary to consider the secondary stiffness of structure, and is is supposed that the decrease of shear performance with the increase of hollow core ratio can be complemented with shear reinforcement.

물량저감 철근상세를 갖는 중공 철근콘크리트 교각단면에 관한 매개변수 연구

김태훈,김호영,이재훈,신현목 한국지진공학회 2013 한국지진공학회논문집 Vol.17 No.4

The purpose of this study is to investigate the inelastic behavior of hollow reinforced concrete bridge column sections with reinforcement details for material quantity reduction and to provide the details and reference data. Among the numerous parameters, this study concentrates on the shape of the section, the reinforcement details, the diameter of the transverse reinforcement and loading types. Eighteen column section specimens were tested under quasi-static monotonic loading. In this study, the computer program RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology) was used. A modified lateral confining effect model was adopted for the hollow bridge column sections. This study documents the testing of hollow reinforced concrete bridge column sections with reinforcement details for material quantity reduction and presents conclusions based on the experimental and analytical findings.

Hollow Twist Extrusion: Introduction, Strain Distribution, and Process Parameters Investigation

J. Joudaki,M. Safari,S. M. Alhosseini 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.6

Twist Extrusion is kind of severe plastic deformation process which enhances the strength of materials by applying a shearplastic strain and consequently grain refinement. The strain distribution is minimum at the center of the die and is maximumat outer surfaces. In this article, the plastic strain distribution will be studied within a hollow section. The billet is solid inprevious experimental and numerical studies in the literature, but by adding a new die (mandrel) for extruding the hollowbillet, it is possible to twist extrude hollow sections. A finite element model is developed in the ABAQUS finite elementsoftware and the effects of process parameters (slope line angle, thickness and friction coefficient) on equivalent plastic straindistribution are investigated. The numerical results show that the equivalent plastic strain will be increased by increasingthe slope line angle and decreasing the thickness and more homogeneity in the strain field will be obtained. In addition,increasing the friction coefficient higher than 0.2 can lead to an increase in induced plastic strain. The required force fortwist extrusion will be increased by increasing the friction coefficient.