Transfer matrix method for construction phase analysis of incrementally launched prestressed concrete bridges

The transfer-matrix method uses a mixed form of the element force–displacement relationship and transfers the structural behavior parameters (state array) from one section to the other. Hence, the transfer matrix method produces a system of equations that are simpler in comparison to those produced by the stiffness method. In this paper, a simplified transfer matrix technique is proposed to evaluate the state of stress at each cross section of prestressed concrete bridge decks during incremental launching. Prestressing force induces additional equivalent loads on the deck in upward as well as downward directions depending on the profile of the prestressing cable. Further, the effect of bearing stiffness makes the construction phase analysis more complex. An elegant and new analysis methodology which can account for the prestressing force and bearing stiffness in the determination of the state of stress in bridge deck sections during incremental launching is proposed in this paper. With the proposed method of ‘Transient Transfer Matrix’ (TTM), so named to indicate its transient nature during the launching process, these problems can be handled efficiently with minimal computational effort. This paper gives insights into the proposed method of analysis, formulation and parametric studies carried out to assess the effect of prestressing force and bearing stiffness on the stress state of incrementally launched bridges during construction.