Experimental and Analytical Evaluation of the Behavior of Concrete T Beams with External Prestressing

Download or read book Experimental and Analytical Evaluation of the Behavior of Concrete T Beams with External Prestressing written by Nada Emile Khairallah and published by . This book was released on 1997 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt: The behavior and flexural resistance of reinforced concrete T beams strengthened using external prestressing were experimentally and analytically investigated. The behavior at both serviceability and limit states were evaluated. A total of twelve beams was tested. The main test variables included ratio of the ordinary reinforcing steel, magnitude of the external prestressing force (or area of external prestressing steel), and profile of the external prestressing tendons. The results indicated clearly that external prestressing is a very powerful technique for strengthening concrete flexural members. The use of external prestressing delayed the formation of flexural cracks, reduced the service load deflections, enhanced the shear performance, and increased the ultimate flexural strength up to 14percent in comparison with conventional reinforced concrete specimens. However, the corresponding improvement in the strength and behavior is accompanied by reduction in the ductility of flexural failure. Everything else being constant, external tendons with deviated profile were more effective in increasing the flexural strength than tendons with straight profile. The experimental results were reproduced analytically using a nonlinear analysis method. The nonlinear analysis method requires constitutive analytical relationships of the stress-strain curves of the constituent materials, namely, concrete, prestressing steel, and ordinary steel, and iteration procedure to satisfy deformation compatibility and force equilibrium at every stage during the load-deformation response of the member. The analytical results based on nonlinear analysis were in very good agreement with the experimental results. Furthermore, comparison was made between the experimental results of the stress in the external prestressing steel and available design equations. Based on this comparison, it was found that the stress in the external prestressing steel and the nominal flexural resistance of externally prestressed members can be predicted with reasonable accuracy using the ACI Building Code approach for beams prestressed with internal unbonded tendons.