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Home > Publications > International Concrete Abstracts Portal
Showing 1-5 of 23 Abstracts search results
Document:
SP120-16
Date:
June 1, 1990
Author(s):
Antoine E. Naaman
Publication:
Symposium Papers
Volume:
120
Abstract:
A simple methodology for the solution of beams prestressed or partially prestressed with external or unbonded tendons in the linear elastic cracked and uncracked range of behavior is described. It leads to equations allowing the computation of stresses in the concrete section, the tensile reinforcing steel, the compression reinforcing steel, and the prestressing steel. In particular, it is shown that the stress in unbonded tendons is a function of the applied loading, the steel profile, and the ratio of the crack width (or crack band width) to the span. These factors can all be accounted for through the use of a strain reduction coefficient ê for the uncracked range of behavior and a similar coefficient êc for the cracked range of behavior. It is shown that, when the strain reduction coefficients ê and êc are taken equal to unity, the solutions developed here revert to the solutions developed earlier for partially prestressed beams with bonded tendons.
DOI:
10.14359/2765
SP120-19
Michael E. Kreger Gregory L. Fenves, and Kamal C. El-Habr
A nonlinear finite element analysis was conducted to examine the full range of behavior of segmentally precast box girder construction with external post-tensioning tendons. A primary objective of the study was to examine the effect of dry joints (without epoxy) on the strength and ductility of box girder construction. A secondary consideration was the influence of supplemental bonded internal tendons on the behavior of the structure.
10.14359/2859
SP120-20
Jeanne M. Nagele, Sankar C. Das, and Reda M. Bakeer
The purpose of this investigation was to examine the forces developing in the dome of a prestressed concrete nuclear containment structure due to prestressing of vertical tendons. A computer program was developed for personal computers to evaluate the effect of prestressing forces. A parametric study was conducted, using the program, to examine the effects of dimensions, prestressing force, properties of tendons, etc. on the resulting stresses in the dome.
10.14359/2862
SP120-21
Eilhard WoelfelI
In the near future, prestressed concrete structures will be designed in Europe according to Eurocode 2 (EC 2). The EC 2 principles governing the design of structures with bonded tendons and with external tendons are given in this paper, and a comparison is made between the structural behavior of the two different types of structures. It is shown that the reliability of both is comparable if the characteristic strain due to prestressing is introduced in the calculations.
10.14359/2865
SP120-22
A. S. Nowak, A. E. Naaman, and S. C.Ting
Evaluation of existing bridges is an important part of the strategy of dealing with the deteriorating infrastructure. Load and resistance parameters are random variables because of uncertainties in load components, material properties, and dimensions. Therefore, the reliability of a structure is a convenient measure of its performance. The load and resistance models are first summarized. The major load components in bridges are dead load and live load. The live load model is based on the weigh-in-motion studies. Girder distribution factors are derived using special computer procedures for bridge analysis. Behavior of composite girders is considered using a nonlinear model. The basic characteristic of the section is the moment-curvature relationship. The reliability is measured in terms of the reliability index. The approach is demonstrated on evaluation of a prestressed concrete girder bridge. Three cases are considered: original design condition, damaged with corroded strands, and repaired by external prestressing. The load components and load-carrying capacities are evaluated and then the reliability indexes are calculated for the three cases.
10.14359/2868
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