Abstract
Modeling of physically non-linear behavior becomes more and more important for the analysis of SFRC structures in practical applications. From this point of view we will present an effective, three-dimensional constitutive model for SFRC, that is also easy to implement in commercial finite element programs. Additionally, the finite element analysis should only require standard material parameters which can be gained easily from conventional experiments or which are specified in appropriate building codes. Another important point is attaining the material parameters from experimental data. The procedures to determine the material parameters proposed in appropriate codes seem to be only approximations and are unsuitable for precise structural analysis. Therefore a finite element analysis of the test itself is used to get the material parameters. This process is also denoted as inverse analysis. The efficiency of the proposed constitutive model is demonstrated on the basis of numerical examples and their comparison to experimental results. In the framework of material parameter identification the idea of a new, indirect tension testing procedure, the
Key Words
steel fiber reinforced concrete; constitutive model; material law; flow theory of plasticity; multisurface plasticity; localization; fracture energy; FEM; modified tension test.
Abstract
(Received December 21, 2005, Accepted May 3, 2006)rnAbstract. Over the past years techniques for non-linear analysis have been enhanced significantly via improved solution procedures, extended finite element techniques and increased robustness of constitutive models. Nevertheless, problems remain, especially for real world structures of softening materials like concrete. The softening gives negative stiffness and risk of bifurcations due to multiple cracks that compete to survive. Incremental-iterative techniques have difficulties in selecting and handling the local peaks and snap-backs. In this contribution, an alternative method is proposed. The softening diagram of negative slope is replaced by a saw-tooth diagram of positive slopes. The incremental-iterative Newton method is replaced by a series of linear analyses using a special scaling technique with subsequent stiffness/strength reduction per critical element. It is shown that this event-by-event strategy is robust and reliable. First, the model is shown to be objective with respect to mesh refinement. Next, the example of a large-scale dog-bone specimen in direct tension is analyzed using an isotropic version of the saw-tooth model. The model is capable of automatically providing the snap-back response. Subsequently, the saw-tooth model is extended to include anisotropy for fixed crack directions to accommodate both tensile cracking and compression strut action for reinforced concrete. Three different reinforced concrete structures are analyzed, a tension-pull specimen, a slender beam and a slab. In all cases, the model naturally provides the local peaks and snap-backs associated with the subsequent development of primary cracks starting from the rebar. The secant saw-tooth stiffness is always positive and the analysis always
Key Words
softening; saw-tooth softening; snap-back; sequentially linear analysis; cracking; fracture; reinforced concrete.
Address
Jan G. Rots; Faculty of Architecture and Faculty of Civil Engineering & Geosciences, Delft University of Technology, P.O.Box 5043, 2600 GA - Delft, The NetherlandsrnStefano Invernizzi; Department of Structural Engineering and Geotechnics, Politecnico di Torino, rnCorso Duca degli Abruzzi 24, 10129 - Torino, Italy. Also research fellow at TUDelft.rn Beatrice Belletti; Department of Civil and Environmental Engineering and Architecture, University of Parma, Parco Area delle Scienze 181/a, 43100 - Parma, Italy. Also research fellow at TUDelft.
Abstract
This investigation presents an analysis procedure for simulating the compressive behavior of a rectangular concrete column confined by fiber-reinforced plastic (FRP) under uniaxial load. That is, the entire stress-strain curve can be drawn through the present analysis procedure. The modified Mander
Key Words
concrete; rectangular column; fiber reinforced plastic (FRP); reinforcement; confined; finite element method (FEM).
Address
Department of Engineering Science and Ocean Engineering National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 106, Taiwan
Abstract
Self-consolidating concrete (SCC) in the fresh state is known for its excellent deformability, high resistance to segregation, and use, without applying vibration, in congested reinforced concrete structures characterized by difficult casting conditions. Such a concrete can be obtained by incorporating either mineral or chemical admixtures. This paper presents the results of an investigation to asses the applicability of Abram
Key Words
self-consolidating concrete; compressive strength equation; statistical optimization.
Address
Department of Civil Engineering, Ryerson Universityrn350 Victoria St, Toronto, ON, Canada, M5B 2K3
Abstract
The flexural behaviour of symmetrically reinforced concrete (RC) columns cast of normal- and high-strength concrete under both monotonic and cyclic loading is studied based on an analytical procedure, which employs the actual stress-strain curves and takes into account the stress-path dependence of concrete and steel reinforcement. The analysis is particularly extended into the post-peak stage with large inelastic deformation at various applied axial load level. The effect of axial load on their complete flexural behaviour is then identified based on the results obtained. The axial load is found to have fairly large effect on the flexural behaviour of RC columns under both monotonic and cyclic loading. Such effects are discussed through examination of various aspects including the moment-curvature relationship, moment capacity, flexural ductility, variation of neutral axis depth and steel stress.
Key Words
axial load; flexural ductility; moment capacity; moment-curvature relationship; monotonic and cyclic loading; reinforced concrete columns.
Address
Department of Civil Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, P.R. China
