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International Concrete Abstracts Portal

Showing 1-5 of 20 Abstracts search results

Document: 

SP237

Date: 

October 11, 2006

Author(s):

Editors: Laura Lowes and Filip Filippou

Publication:

Symposium Papers

Volume:

237

Abstract:

SP-237CD This CD-ROM is a collection of 19 papers presented at a workshop sponsored by Joint ACI-ASCE Committee 447, Finite Element Analysis of Reinforced Concrete Structures, and JCI Committee 016SP, in Maui, Hawaii, USA, in November 2003. A broad range of topics was addressed, including the creation of new experimental data sets for use in developing, calibrating, and validating models; the development and validation of plain, reinforced, and fiber-reinforced concrete constitutive models; new approaches to simulating the response of reinforced concrete continua; new element formations to enable improved simulation of component response; and new computational techniques.

DOI:

10.14359/18184


Document: 

SP237-19

Date: 

August 1, 2006

Author(s):

F.C. Filippou and A. Saritas

Publication:

Symposium Papers

Volume:

237

Abstract:

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 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. Next, 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 ‘converges’. Bifurcations are prevented due to the scaling technique.

DOI:

10.14359/18260


Document: 

SP237-08

Date: 

August 1, 2006

Author(s):

F.J. Vecchio

Publication:

Symposium Papers

Volume:

237

Abstract:

Code procedures for the seismic design of reinforced concrete structures are increasingly incorporating performance-based criteria, with ‘push-over’ analyses becoming an accepted means of demonstrating sufficient energy-absorbing capacity. Hence, in concrete frame structures containing shear-critical structural elements, the post-peak load-deformation response of these members becomes of practical importance. A series of shear-critical beams was tested recently, patterned after the classic set of beams tested by Bresler and Scordelis forty years ago. In the current tests, particular attention was paid to capturing the post-peak response. The details and results of these beams are presented, providing data useful in testing and calibrating analytical procedures. Nonlinear finite element analyses were undertaken to determine current ability to accurately model post-peak ductility in shear-critical members. Results indicate that current procedures are of marginally acceptable accuracy, and that further developmental work is warranted. A case study, involving a large concrete frame structure built in a high seismic region and containing shear-deficient members, is discussed. This case underscores the importance of accurately calculating the post-peak ductility of shear-critical beams.

DOI:

10.14359/18249


Document: 

SP237-03

Date: 

August 1, 2006

Author(s):

K. Suzuki and A. Fujii

Publication:

Symposium Papers

Volume:

237

Abstract:

Two interior column (RC)-beam (PPC) specimens were tested. The specimens were first subjected to reversed, repeated cyclic loading to maximum rotational angles of 1/30 and 1/16, respectively. The specimens were then repaired using resin injection and mortar covering. Mechanical properties obtained following repair were almost the same as those obtained during the initial loading, probably, due to the confined concrete used in the beam ends. However, a reduction in initial stiffness of approximately 30% was observed.

DOI:

10.14359/18240


Document: 

SP237-12

Date: 

August 1, 2006

Author(s):

H. Nakamura, Y. Yamamoto, A. Itoh, and T. Tanabe

Publication:

Symposium Papers

Volume:

237

Abstract:

For members with symmetric cross-sections, the geometric centroid and shear center are coincident. Thus, if lateral load is applied through the geometric centroid, a torsional moment is not induced. However, a RC cross sections typically develop an asymmetric resistance mechanisms, resulting in progressive movement of the shear center away from the geometric centroid as nonlinearity increases and the section responds to bi-axial loading. In this study, the mechanism causing shifting of the shear center for RC cross sections was investigated using frame elements with a fiber-type discretization of the member cross-section. Then, the effects of the torsional moment induced by the shifting of the shear center were discussed, and it was shown that the effect in not negligible in practical design.

DOI:

10.14359/18253


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