Effect of the eccentricity in joints of mixed spatial truss superstructure of bridges (tridiloses)

Abstract

The authors present a case study carried out to know the relevance, in the resistance of the bars, of the eccentricity in the joints of a bridge with mixed spatial truss superstructure. This type of superstructures was built in a significant number in Mexico, from its technological development. This technique was proposed by Ing. Heberto Castillo Martínez in the 1960s (1). Some of these superstructures are still in use. In this article, the case study is the Santo Domingo bridge, on the river of the same name located in Chiapas, Mexico. As a first phase, the superstructure is analyzed considering the concentric bars in the joints. In a second phase, the flexing moments generated by the eccentricity in the mid-height joints of the tridilose are taken into account. The resistance of critical elements is calculated considering separately the effects of the axial loads, of the bending moments caused by the own weight and the flexion in the slab and the bending moments caused by the eccentricity of the bars in the joints. The authors conclude that approximately half of the resistance of the bars is required to take the bending moments caused by the eccentricity of the bars in the joints.