Risk of failure for the salso river railroad steel bridge

Abstract

The degradation state of railroad steel bridges is one of the most important and difficult aspects to be interpreted. The use of steel bridges started from 1900, and they are still in service today as railroad bridges. The case study examined was that of a bridge railroad steel bridge having a total length of 112 m and constituted by three isostatic, reticular beams having a Pratt type composition. The substructures (two shoulders and two intermediate piles) are in masonry with a reinforced concrete beam in the upper portion.The structure (steel bridge and piers) is in a degraded state. To determine the degradation level, non-destructive and partially destructive tests were carried out: - a geometric survey with careful detection of the crack patterns;- a georadar survey on a flat and inclined surface of the pier; - pacometric tests on the upper concrete beams to determine the position and the actual diameter of the reinforcement bars; - endoscopic tests to examine the morphology, typology, and state of conservation of the materials of the piers; - mechanical characterization of masonry constituting the piers through extraction of long core specimens to be tested for compression, chemical and mechanical characterization of the mortar; -microhardness tests for estimating the mechanical tensile strength of the steel constituting the bridge deck. The results obtained were utilized to characterize the strength of the constituent materials for static verification of the steel bridge under permanent and accidental loads, according to the Italian Building Code. The results obtained showed that for this bridge there are no risks of failure, but it was not checked against the Eurocodes, and a retrofitting design is still required.