Analysis of the Flexural Behavior of Precast Prestressed Beams with Semi-Rigid Connections

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Title: Analysis of the Flexural Behavior of Precast Prestressed Beams with Semi-Rigid Connections

Author(s): B. Catoia, M.A. Ferreira, R.C. Carvalho, and T. Catoia

Publication: Special Publication

Volume: 253

Issue:

Appears on pages(s): 217-234

Keywords: deformation; prestressed beams; semi-rigid connections; stiffness; strength

Date: 7/31/2008

Abstract:
The flexural behavior of precast concrete beams is strongly infl uenced by their end connections. Connections can be considered as zones of discontinuity within the precast structure, wherein stress concentrations occur. Depending on the connection effi ciency in terms of mobilizing displacements and transferring forces, there will be a correlative redistribution of the internal forces throughout the precast structure. This paper deals with the study of the behavior of precast prestressed beams with semi-rigid connections, wherein analytical procedures considering the interaction between moment-curvature relation of the precast beam and the moment-rotation relation of its beam-column connections have been proposed and experimentally validated. By using these procedures, equations based on the fixity factor of the connections were combined with experimental results, allowing the integration between the stiffness of the beam and the rotational stiffness of the beam-column connections. Within the experimental methodology, fl exural tests of prestressed beams were conducted, considering both pinned and semi-rigid connections. Therefore, it has been possible to evaluate the effect of semi-rigid connections on the fl exural behavior of the precast beam, in which defl ections, rotations, and curvature of the semi-rigidly connected beam were compared with equivalent parameters from the fl exural test of the simply supported beam, in order to estimate the partially restrained moment at the beam ends. This approach provided accurate results for the partially restrained moments at the beam ends, indicating that the beam supports were semi-rigid. Based in the experimental results of the studied model, the effective partially restrained end moment considering ULS has been estimated between 60% and 70% of the full restrained moment.