Forward Algorithm for the construction control of cable-stayed bridges built on temporary supports

Abstract

Traditionally the construction process of cable-stayed bridges is modeled according to the backward approach, as its calculation is much easier using an elastic analysis. In this approach the bridge is disassembled according to the opposite sequence of events which occur during its erection. The main trade off of the backward approach is that time-dependent phenomena, such as creep, shrinkage or cable relaxation, cannot be directly computed as the analysis is performed according to the reversed time direction.In this paper the Forward Algorithm (FA) that is based on the forward approach is formally presented. This procedure has been applied to the temporary supports erection method as no specific investigation of this erection technique has been found by the authors. The FA has the following advantages: (1) Modifications in design and/or tensioning strategy can be easily computed. (2) The effect of time-dependent phenomena can be efficiently included into the calculation of the construction process of the bridge. (3) Differences between the temperatures in the structural elements assumed when doing the structural analysis of the bridge and the real ones when built can be calculated without the need of separate models. (4) The stresses in the mono-strands when the strand by strand prestressing technique is used are obtained directly. (5) Stay and strand elongation, which are very useful to control the prestressing operations, can be also easily computed. All these features make the FA an efficient procedure to control the construction process on site, increasing safety during construction and decreasing construction time.