Research on Restraint System of Malutang Bridge in Wenshan,a Composite Girder Cable-Stayed Bridge with High-Rise Piers
The main bridge of Malutang Bridge in Wenshan is a steel-concrete composite girder cable-stayed bridge with a main span of 480 m.The two pylons rise 122.5 m and 129.5 m,respectively,below the deck.Four types of restraint system that can improve the longitudinal stiffness of the bridge are compared by finite element modeling,including the longitudinal unrestraint system,longitudinal rigid restraint system,fixed system and longitudinal elastic restraint system.And the applicability of the longitudinal elastic restraint system in the composite girder cable-stayed bridge with different below-deck pylon heights was studied.It is shown that compared with the longitudinal unrestraint system,the longitudinal elastic restraint system can help reduce the girder-end displacements by 37.2％and 36.1％,and the longitudinal pylon-bottom bending moments by 19.5％and 19.8％under the static and dynamic actions,respectively,and the first-mode longitudinal floating period of the structure is shortened by 2.76 s.Compared with the other three restraint systems,the anti-cracking stress margin in the concrete panels at the auxiliary piers when the bridge is equipped with a longitudinal elastic restraint system is increased by 1.13 MPa under the combined actions of frequent loads.The longitudinal elastic restraint system with a stiffness of 12 MN/m are installed in between the pylons and the girder of the Malutang Bridge.The longitudinal stiffness of the bridge gradually decreases along with the increase of the heights of the pylons below the deck.When the ratio of the below-deck pylon heights and the total pylon heights exceeds 0.35,the longitudinal stiffness of the structure drops nonlinearly,indicating that the longitudinal elastic restraint system is effective in improving the longitudinal stiffness of the structure.
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