Investigating the redundancy of steel truss bridges composed of modular joints

Abstract

The objective of this paper is to present a numerical investigation of the redundancy of steel truss bridges composed of novel modular joints when subjected to the sudden loss of diagonal members. The modular joint - a prefabricated steel nodal connector composed of flat web plate welded to flat and curved cold bent flange plates - represents a new approach to the construction of steel truss bridges in which the connector is a module that joins member that are standard rolled wide flange sections. A unique feature of this approach is that a moment-resisting connection is achieved in a truss topology by joining webs and flanges independently through bolted splice connections. This, in combination with orienting members in strong axis bending, provides the potential for the system to tolerate the loss of a diagonal member through load redistribution in flexure. The response of a 119-m (390-ft) simply supported vehicular bridge following the abrupt loss of a diagonal is numerically investigated considering three behaviors: (1) instantaneous dynamic behavior, focusing on the effect of the high-velocity stress wave, with its associated high strain rates and impact on fracture toughness particularly in the cold bent and welded portion of the modular joint, (2) short-term dynamic behavior of the structure, and (3) static behavior of the faulted structure. Results show that the modular joint is able to redistribute load after sudden member loss, demonstrating the redundancy of this new approach to modular construction.