Abstract
Post-tensioning is being widely used in bridges, namely, highway bridges, railway bridges, segmental box girder bridges, METRO bridges, and sea links. Generally, the ultimate flexural behavior of concrete members with unbonded tendons is evaluated by the stress in unbonded tendons at ultimate state. Researchers have developed the equations using various analytical concepts, namely, moment–curvature relationship, empirical methods, strain reduction coefficient method, equivalent plastic hinge length method, and finite element method. The paper intends to present the performance of the prediction equations and suitable analytical concept for calculating the stress in tendons. Performance of prediction equations for calculating the stress at ultimate in unbonded tendons \( f_{{\text{ps}}} \) has been evaluated using experimental data published in the literature. In the next stage, an experimental investigation on the flexural behavior of post-tensioned concrete beam is done by authors, and the results have been used for evaluation. Also, the FEM analysis using ANSYS package is also performed and compared with test results. It is concluded that the prediction equations developed using equivalent plastic hinge length concept have performed well.
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Abbreviations
- \( A_{{\text{ps}}} \) :
-
Area of prestressing steel
- \( A_{\text{s}} \) :
-
Area of nonprestressed tensile steel
- \( A_{\text{s}}^{{\prime }} \) :
-
Area of nonprestressed compressive steel
- \( b \) :
-
Width of the section
- \( c \) :
-
Depth from concrete extreme compressive fiber to neutral axis
- \( c_{\text{y}} \) :
-
Depth from concrete extreme compressive fiber to neutral axis calculated using \( f_{{\text{py}}} \)
- \( d_{\text{p}} \) :
-
Depth from concrete extreme fiber to centroid of the prestressing steel
- \( d_{\text{s}} \) :
-
Depth from concrete extreme compressive fiber to centroid of the non prestressed tensile steel
- \( d_{\text{s}}^{{\prime }} \) :
-
Depth from concrete extreme compressive fiber to centroid of the nonprestressed compressive steel
- \( E_{{\text{ps}}} \) :
-
Modulus of elasticity of the prestressing steel
- \( f_{{\text{pe}}} \) :
-
Effective stress in the prestressing steel
- \( f_{{\text{ps}}} \) :
-
Ultimate stress in the prestressing steel
- \( f_{{\text{pu}}} \) :
-
Ultimate strength of the prestressing steel
- \( f_{{\text{py}}} \) :
-
Yield strength of the prestressing steel
- \( f_{\text{c}}^{{\prime }} \) :
-
Concrete compressive strength
- \( f_{{\text{cu}}} \) :
-
Concrete compressive strength taken from cube test
- \( f_{\text{y}} \) :
-
Yield strength of nonprestressed tensile steel
- \( f^{\prime}_{\text{y}} \) :
-
Yield strength of nonprestressed compressive steel
- \( h \) :
-
Height of the section
- \( h_{\text{f}} \) :
-
Thickness of the flange
- \( L \) :
-
Span length between end anchorages
- \( L_{\text{e}} \) :
-
Span length between end anchorages divided by the number of plastic hinges
- \( L_{\text{p}} \) :
-
Width of the plastic zone
- \( L_{0} \) :
-
Equivalent plastic hinge length
- \( \beta_{1} \) :
-
ACI concrete compression block reduction factor
- \( \rho_{\text{p}} \) :
-
Prestressing steel ratio
- \( \rho_{\text{s}} \) :
-
Reinforcing steel ratio
- \( \varepsilon_{{\text{cu}}} \) :
-
Strain in the concrete at the compressive fiber at ultimate
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This paper is being published with the kind permission of the Director, CSIR-Structural Engineering Research Centre, Chennai.
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Manisekar, R., Saravana Kumar, K. (2019). Stress in Unbonded Tendons for Post-tensioned Concrete Members—Assessment of Prediction Equations and Experimental Investigation. In: Rao, A., Ramanjaneyulu, K. (eds) Recent Advances in Structural Engineering, Volume 1. Lecture Notes in Civil Engineering , vol 11. Springer, Singapore. https://doi.org/10.1007/978-981-13-0362-3_20
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