End Zone Reinforcement for Pretensioned Concrete Girders
In this study, a literature review was conducted to establish the background of current specifications and to evaluate the applicability of various theories and methods for design of end zone reinforcement. Analytical methods reviewed in this paper include finite element analysis, strut- and-tie modeling, and the Gergely-Sozen equivalent beam method. Previous experimental work combined with work conducted as part of this study were used to correlate between various theoretical and experimental results. This paper illustrates that no single theoretical method adequately represents the complex behavior at the end of a pretensioned concrete member. A general semi-empirical design procedure is proposed here. It is based on theoretical behavior and experimental observation. Standard reinforcement details are given. The proposed procedure could result in reduction in the congestion of reinforcement while maintaining acceptable crack control at the member end. Application of the proposed procedure to highly pretensioned bridge girders is demonstrated.
Stresses In The End Zones Of Precast Inverted T-Beams With Tapered Webs
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Exponential stabilization of an axially moving string with geometrical nonlinearity by linear boundary feedback
This paper addresses the vibration suppression problem of an axially moving string using boundary control. Taking into account large transverse motion of the string via the second-order component of Lagrangian strain, a nonlinear oscillation equation is derived for the problem by employing the Hamilton's Principle. Direct Lyapunov method is then adopted to demonstrate that a linear boundary control of negative speed feedback ensures the vibration response of the moving string exponentially stable. The main contributions are a new stability condition in terms of controller gain parameter, and a detailed demonstration on the equilibrium condition at the boundary where the control is applied.