구조용 데크플레이트를 사용한 연속 합성슬래브 시스템의 모멘트 재분배 및 소성회전능력

정헌수,은희창,양근혁 대한건축학회 2005 大韓建築學會論文集 : 構造系 Vol.21 No.2

The objective of this study is to evaluate the moment redistribution and plastic rotation of continuous one-way composite slabs reinforced with structural steel decking. A total of 8 two-span continuous slabs with fixed-ends were tested and compared with limit analysis approaches. Theoretical moment capacity and curvature for section subjected to positive or negative moment were calculated by section laminae method. Test results showed that flexural behavior and rotation were greatly influenced by the amount of top bar in negative moment region. Also, the welded wire fabric used as top bar in negative moment region could result in decreasing total load capacity of slabs due to impairing moment redistribution. The predictions, maximum load and plastic rotation capacity, obtained from proposed analysis method were in good agreement with the test results.

단부?중앙부 모멘트 철근 분배율에 따른 플랫플레이트의 모멘트 재분배에 관한 실험

최정욱,송진규 한국콘크리트학회 2007 콘크리트학회논문집 Vol.19 No.5

Three interior slab-column connections designed by equal static moments and by different distribution of end and midspan moments were tested. Each test specimen consisted of a 4.2 m square slab and a 355 mm square column stub. The slab thickness was 152 mm. Test results showed not only that flat slab systems can undergo considerable redistribution of moments from the uncracked state to final maximum capacity, but also that the distribution of moments is controlled largely by the distribution of reinforcement adopted by the designer. The tests also indicated that the punching shear strength of slabs can be affected with the redistributed moments.

I-Beam연속교 내측지점의 소성변형에 관한 연구

정경희,김진성,양승이 한국산업안전학회 2002 한국안전학회지 Vol.17 No.4

The steel shows plastic deformation after the yield point exceeds. Because of overloads, the plastic deformation occurs at the interior support of a continuous bridge. The plastic deformation is concentrated at the interior support, and the permanence deformation at the interior support remains after loads pass. Because local yielding causes the positive moment at the interior support, it is called "auto moment". Auto moment redistributes the elastic moment. Because of redistribution, auto moment decreases the negative moment at the interior support of a continuous bridge. In this paper, the moment-rotation curve from Schalling is used. The plastic rotation is computed by using Beam-line method, and auto moment is calculated based on the experiment curve. The design example is presented using limit state criterion.

FE modeling of inelastic behavior of reinforced high-strength concrete continuous beams

Lou, Tiejiong,Lopes, Sergio M.R.,Lopes, Adelino V. Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.3

A finite element model for predicting the entire nonlinear behavior of reinforced high-strength concrete continuous beams is described. The model is based on the moment-curvature relations pre-generated through section analysis, and is formulated utilizing the Timoshenko beam theory. The validity of the model is verified with experimental results of a series of continuous high-strength concrete beam specimens. Some important aspects of behavior of the beams having different tensile reinforcement ratios are evaluated. In addition, a parametric study is carried out on continuous high-strength concrete beams with practical dimensions to examine the effect of tensile reinforcement on the degree of moment redistribution. The analysis shows that the tensile reinforcement in continuous high-strength concrete beams affects significantly the member behavior, namely, the flexural cracking stiffness, flexural ductility, neutral axis depth and redistribution of moments. It is also found that the relation between the tensile reinforcement ratios at critical negative and positive moment regions has great influence on the moment redistribution, while the importance of this factor is neglected in various codes.

FE modeling of inelastic behavior of reinforced high-strength concrete continuous beams

Tiejiong Lou,Sergio M.R. Lopes,Adelino V. Lopes 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.49 No.3

A finite element model for predicting the entire nonlinear behavior of reinforced high-strengthconcrete continuous beams is described. The model is based on the moment-curvature relations pre-generated through section analysis, and is formulated utilizing the Timoshenko beam theory. The validity of the model is verified with experimental results of a series of continuous high-strength concretebeam specimens. Some important aspects of behavior of the beams having different tensile reinforcement ratios are evaluated. In addition, a parametric study is carried out on continuous high-strength concrete beams with practical dimensions to examine the effect of tensile reinforcement on the degree of moment redistribution. The analysis shows that the tensile reinforcement in continuous high-strength concrete beamsaffects significantly the member behavior, namely, the flexural cracking stiffness, flexural ductility, neutral axis depth and redistribution of moments. It is also found that the relation between the tensile reinforcement ratios at critical negative and positive moment regions has great influence on the moment redistribution, while the importance of this factor is neglected in various codes.

Behaviour of continuous prestressed concrete beams with external tendons

K.H. Enoch Chan,Vahid Babaghasabha 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.55 No.6

External prestressing has been applied to both new construction and retrofitting of existing reinforced and prestressed concrete structures. Continuous beams are preferred to simply supported beams because of economy, fewer movement joints and possible benefits from moment redistribution. However, this paper argues that continuous prestressed concrete beams with external unbonded tendons demonstrate different full-range behaviour compared to reinforced concrete (RC) beams. Applying the same design approach for RC to external prestressing may lead to design with a lower safety margin. To better understand the behaviour of continuous prestressed concrete beams with unbonded tendons, an experimental investigation is performed in which nine such specimens are tested to failure. The full-range behaviour is investigated with reference to moment-curvature relationship and moment redistribution. The amounts of moment redistribution measured in the experiments are compared with those allowed by BS 8110, EC2 and ACI 318. Design equations are also proposed to estimate the curvature ductility index of unbonded prestressed concrete beams.

Design for moment redistribution in FRP plated RC beams

Deric John Oehlers,Matthew Haskett,Mohamed Ali M.S. 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.38 No.6

Assessing the ductility of reinforced concrete sections and members has been a complex and intractable problem for many years. Given the complexity in estimating ductility, members are often designed specifically for strength whilst ductility is provided implicitly through the use of ductile steel reinforcing bars and by ensuring that concrete crushing provides the ultimate limit state. As such, the empirical hinge length and neutral axis depth approaches have been sufficient to estimate ductility and moment redistribution within the bounds of the test regimes from which they were derived. However, being empirical, these methods do not have a sound structural mechanics background and consequently have severe limitations when brittle materials are used and when concrete crushing may not occur. Structural mechanics based approaches to estimating rotational capacities and rotation requirements for given amounts of moment redistribution have shown that FRP plated reinforced concrete (RC) sections can have significant moment redistribution capacities. In this paper, the concept of moment redistribution in beams is explained and it is shown specifically how an existing RC member can be retrofitted with FRP plates for both strength and ductility requirements. Furthermore, it is also shown how ductility through moment redistribution can be used to maximise the increase in strength of a member. The concept of primary and secondary hinges is also introduced and it is shown how the response of the nonhinge region influences the redistribution capacity of the primary hinges, and that for maximum moment redistribution to occur the non-hinge region needs to remain elastic.

Probabilistic models for curvature ductility and moment redistribution of RC beams

Hassan Baji,Hamid Reza Ronagh 사단법인 한국계산역학회 2015 Computers and Concrete, An International Journal Vol.16 No.2

It is generally accepted that, in the interest of safety, it is essential to provide a minimum level of flexural ductility, which will allow energy dissipation and moment redistribution as required. If one wishes to be uniformly conservative across all of the design variables, curvature ductility and moment redistribution factor should be calculated using a probabilistic method, as is the case for other design parameters in reinforced concrete mechanics. In this study, simple expressions are derived for the evaluation of curvature ductility and moment redistribution factor, based on the concept of demand and capacity rotation. Probabilistic models are then derived for both the curvature ductility and the moment redistribution factor, by means of central limit theorem and through taking advantage of the specific behaviour of moment redistribution factor as a function of curvature ductility and plastic hinge length. The Monte Carlo Simulation (MCS) method is used to check and verify the results of the proposed method. Although some minor simplifications are made in the proposed method, there is a very good agreement between the MCS and the proposed method. The proposed method could be used in any future probabilistic evaluation of curvature ductility and moment redistribution factors.

Redistribution of moments in reinforced high-strength concrete beams with and without confinement

Tiejiong Lou,Sergio M.R. Lopes,Adelino V. Lopes 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.55 No.2

Confinement is known to have important influence on ductility of high-strength concrete (HSC) members and it may therefore be anticipated that this parameter would also affect notably the moment redistribution in these members. The correctness of this “common-sense knowledge” is examined in the present study. A numerical test is performed on two-span continuous reinforced HSC beams with and without confinement using an experimentally validated nonlinear model. The results show that the effect of confinement on moment redistribution is totally different from that on flexural ductility. The moment redistribution at ultimate limit state is found to be almost independent of the confinement, provided that both the negative and positive plastic hinges have formed at failure. The numerical findings are consistent with tests performed on prototype HSC beams. Several design codes are evaluated. It is demonstrated that the code equations by Eurocode 2 (EC2), British Standards Institution (BSI) and Canadian Standards Association (CSA) can well reflect the effect of confinement on moment redistribution in reinforced HSC beams but the American Concrete Institute (ACI) code cannot.

Factors governing redistribution of moment in continuous prestressed concrete beams

Kodur, V.K.R.,Campbell, T.I. Techno-Press 1999 Structural Engineering and Mechanics, An Int'l Jou Vol.8 No.2

The failure load of a continuous prestressed concrete beam depends partially on the amount of redistribution of moment that occurs prior to failure. Results from a parametric study, carried out using a nonlinear finite element computer program, are presented to demonstrate the influences of various factors on redistribution of moment in two-span, continuous bonded prestressed concrete beams. Trends in the data from the numerical studies are compared with those from a theoretical expression for percentage of redistribution, and it is shown that the redistribution of moment occurring in a continuous prestressed concrete beam is a function of number of parameters.