G. A. Parsekian 1 , L. S. Franco2, R. C. Carvalho3
- Professor, Dept of Civil Engineering, Federal University of Sao Carlos, Brazil, gparsekian@terra.com.br
- Professor, Dept of Civil Engineering, University of Sao Paulo, Brazil, luiz.franco@poli.usp.br
- Professor, Dept of Civil Engineering, Federal University of Sao Carlos, Brazil, chust@power.ufscar.br
ABSTRACT
Prestressed masonry has been widely used in constructions where the walls are required to resist lateral loads, as in the case of retaining walls, water tanks, one-story buildings and others. Countries where this technology has been used include the United Kingdom, Australia, Switzerland, and United States, where recommendations for design and execution have been a part of local codes and standards for some years. In Brazil only a few cases are known.
In this paper, we present and discuss some recommendations for the design of prestressed masonry for possible inclusion in the Brazilian Code. These recommendations are based on an extensive experimental program conducted with national materials and techniques. Also a review of several international references and codes has been taken into account.
The discussion includes considerations of combined axial compression and flexure and shear design, taking or not taking into account the prestress force in buckling effects, anchorages and bearing stresses, wall stability and prediction of prestress losses due to elastic shortening. Shrinkage, creep, thermal effects, anchorage seating, friction loss and relaxation of prestressing tendon are also considered.
Good practice in execution is also discussed, including the best type of tendon (rod or strand), how to apply prestress (with a torque wrench or hydraulic jack), how to measure prestress force (measuring torque, using direct tension indicators, measuring tendon elongation, measuring the pressure applied to the hydraulic jack), when and where to grout, position of couplers, advantages of applying a provisional prestress in the early days, curing period of final stressing.
KEYWORDS: Prestressed Masonry, Code, Brazilian Code
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