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International Concrete Abstracts Portal

Showing 1-5 of 30 Abstracts search results

Document: 

SP265-01

Date: 

October 1, 2009

Author(s):

R.D. Lequesne, G.J. Parra-Montesinos, and J.K. Wight

Publication:

Symposium Papers

Volume:

265

Abstract:

Results from the test of a large-scale coupled-wall specimen consisting of two T-shaped reinforced concrete structural walls joined at four levels by precast coupling beams are presented. Each coupling beam had a span length-depth ratio (ln/h) of 1.7, and was designed to carry a shear stress of 7vfc' [psi], (0.59vfc' [MPa]). One reinforced concrete coupling beam was included along with three strain-hardening, high-performance fiber-reinforced concrete (HPFRC) coupling beams to allow a comparison of their behavior. When subjected to reversing lateral displacements, the system behaved in a highly ductile manner characterized by excellent strength retention to drifts of 3% without appreciable pinching of the lateral load versus drift hysteresis loops. The reinforced concrete structural walls showed an excellent damage tolerance in response to peak average base shear stresses of 4.4vfc' [psi], (0.34vfc' [MPa]). This paper presents the observed damage patterns in the coupling beams and the structural walls. The restraining effect provided by the structural walls to damage-induced lengthening of the coupling beams is discussed and compared with that observed in component tests. Finally, the end rotations measured in the coupling beams relative to the drift of the coupled-wall system are also presented.

DOI:

10.14359/51663288


Document: 

SP265-21

Date: 

October 1, 2009

Author(s):

M. Labib, Y. Moslehy, and A.S. Ayoub

Publication:

Symposium Papers

Volume:

265

Abstract:

The two-dimensional design and behavior of typical reinforced concrete (RC) structures has been extensively studied in the past several decades. Such design requires knowledge of the constitutive behavior of reinforced concrete elements subjected to a biaxial state of stress. These constitutive models were accurately derived from experimental test data on representative reinforced concrete panel elements. The true behavior of many large complex structures, however, requires knowledge of the constitutive laws of RC elements subjected to a triaxial state of stress. The goal of the proposed work is to develop new constitutive relations for RC elements subjected to a triaxial state of stress. To accomplish this task, largescale tests on representative concrete panels need to be conducted. The University of Houston is equipped with a unique universal panel testing machine that was used for this purpose. This universal panel tester is the only one of its kind in the United States, and the only one in the world that allows for both displacement and forcecontrolled load application through its newly upgraded servo-control system. The panel tester enhanced the understanding of the in-plane shear behavior of reinforced concrete elements. Recently, 20 additional hydraulic cylinders were mounted in the out-of-plane direction of the universal panel tester to facilitate testing of concrete elements subjected to tridirectional shear stresses. The addition of these cylinders makes the panel tester the only one of its kind in the world that is capable of applying such combinations of stresses on full-scale reinforced concrete elements. This paper presents the details of the mounting and installation of the additional hydraulic cylinders on the universal panel tester, and preliminary results of large-scale tests of a series of RC panels subjected to three-dimensional shear loads.

DOI:

10.14359/51663308


Document: 

SP265-29

Date: 

October 1, 2009

Author(s):

A.S. Nowak and P. Paczkowski

Publication:

Symposium Papers

Volume:

265

Abstract:

Recent calibration of ACI 318-08 for concrete structures was focused on the flexural capacity. The objective of this paper is to develop the statistical parameters for shear capacity of reinforced concrete beams. The capacity of shear reinforcement is a function of steel cross section area, yield strength, and spacing of stirrups. In this paper, the capacity of concrete is considered using ACI formulas and other shear capacity models available in literature. The analysis is performed for various reinforcement ratios, longitudinal and transverse, including beams without web reinforcement. The statistical parameters of resistance are determined from the test results. The reliability analysis is performed, and it serves as a basis for the selection of resistance factors. The selection criterion is closeness to the target reliability index. Recommended values of resistance factors are provided for each of the considered shear capacity methods.

DOI:

10.14359/51663317


Document: 

SP265-08

Date: 

October 1, 2009

Author(s):

L.N. Lowes, P. Oyen, and D.E. Lehman

Publication:

Symposium Papers

Volume:

265

Abstract:

Recent advances in computational capabilities, both hardware and software, have made nonlinear analysis a viable tool for seismic structural engineering. To fully realize the potential of this tool, however, engineers require nonlinear models and modeling recommendations that have been validated using extensive experimental data sets. For reinforced concrete beams and columns that exhibit primarily flexural response, beam-column elements with fiber-type cross section models have been shown to simulate well observed response. While these types of models are used commonly in practice for design of concrete wall buildings, a comprehensive evaluation of these models for simulating wall response has not been accomplished. Thus, as part of an ongoing study funded by NSF through the NEES program, an investigation of the accuracy of these models for simulating concrete wall response was undertaken. A data set comprising 60 planar wall tests was assembled and used to evaluate the accuracy with which critical response parameters could be predicted. The force-based beam-column element formulations available in the OpenSees platform were used with a standard fiber-type cross section model that simulates flexureaxial load interaction. A MATLAB code was created to facilitate the evaluation process. Results of the evaluation showed that the basic model over-predicted stiffness and under-predicted critical displacements, and an enhanced model was developed that includes a bar-slip model at the base of the wall and an effective, elastic shear stiffness. The enhanced model was calibrated using the data set, and the MATLAB-based code and MATLAB optimization toolbox were used to find an optimal shear stiffness. For three representative walls, the response history simulated using the enhanced beamcolumn element was compared with that simulated using the Response 2000 and VecTor2 analysis programs. The results of this study show that the enhanced beamcolumn element is appropriate for use in simulating the response of concrete walls with a range of design parameters.

DOI:

10.14359/51663295


Document: 

SP265-22

Date: 

October 1, 2009

Author(s):

N.M. Hawkins and D.A. Kuchma

Publication:

Symposium Papers

Volume:

265

Abstract:

Five specific limitations to the existing shear design methodologies of the AASHTO LRFD Bridge Design Specifications and ACI 318-08 are discussed: (1) the issues resulting from the fact that what has been tested in the laboratory is not representative of what is built in the field for bridge structures and therefore where additional laboratory testing is needed particularly for bridge members; (2) the equivalency and non-equivalency of the treatment of axial load and prestress in shear provisions; (3) the basis for the minimum and maximum shear reinforcement requirements or limits for members and why those requirements differ in the AASHTO LRFD Specifications from those in ACI 318-08; (4) shear design considerations for the end regions of bridge girders and the need to design for the effects of the funneling of the shear force into the support and the balancing of the tension caused by shear at the face of the support; and (5) the relative variations in the components of the shear resistance with increasing load and changes in member behavior and the significance of those variations for the limitations to the existing shear design concepts of the AASHTO LRFD Specifications and ACI 318-08.

DOI:

10.14359/51663309


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