A76 REPORT—1899. 
operation of mounting the arches was interrupted in the month of 
January. 
Some peculiarities of the metallic structure in connection with the 
use of cast steel, and the flatness and the width of the bridge, present a 
certain interest of novelty. 
As the steel-makers deemed it important for the good and cheap 
casting of the voussoirs that the thickness of al] parts of them should be 
as uniform as possible, the surfaces of the webs and of the top and bottom 
flanges have been designed to be plain without any hook or prominent 
block. Only a few bearings, obtained by planing at places an extra thick- 
ness of ten or twelve millimetres, were allowed besides the stays stiffening 
the webs and flanges. 
As, moreover, the bridge is skew, there is no correspondence between 
the stays of the consecutive ribs, and, therefore, no possibility of using 
them for the necessary connections between the ribs. 
For these reasons the voussoirs have been arranged to be held only by 
the top flange, and they have been stiffened in consequence by strong 
joint tables and two main stays. Near the springings, cast steel shoes 
fixed at the base of the upright pillars grasp the top flange of the 
voussoirs properly planed and drilled at these points ; bolts keep the shoes 
from slipping along the flanges. The upright pillars being connected 
together by means of horizontal and cross bars, the shoes are strongly 
maintained at the required distance. 
In the central part, on account of the want of height, the top flanges 
of the voussoirs are held by the beams of the flooring. This arrange- 
ment, which the engineers could not help making use of, was somewhat 
troublesome. In consequence of it the structure of the flooring required 
the most careful designing ; the distance from the top of the arches to 
the top of the beams being extremely variable, and according with no 
simple law on account of the convexity of the flooring and of the obliquity 
of the beams to the direction of the axis of the river, the joints connect- 
ing the beams with the arches have been necessarily made in the most 
various ways, the number being no less than 173. 
The last peculiarity I have to mention to you concerns the precautions 
taken on account of the transversal expansion, which is not to be neg- 
lected on a length of 40 metres (141 feet). It was found that the stresses 
developed in the arches near the springings in consequence of the expan- 
sion of the rigid beams in which the top flanges were inserted by the 
aforesaid cast steel shoes, could rise at a dangerous rate. Consequently, 
the three sets of beams near the springings have been supplied with 
expansion joints made of Belleville spring washers, so that the stresses 
transmitted by the horizontal bars of the beams are limited. 
The test requirements for the steel do not present anything of special 
interest. The steel has been divided into four grades : 
Steel for angles and plates ; grade I. 
Steel for rivets ; grade IT. 
Steel castings for voussoirs ; grade III. 
Hammered steel for pins ; grade IV. 
All steel castings have been thoroughly annealed. The tests required 
for this part of the work concerned not only tensile strength, but also 
power to resist shocks, Y 
The required conditions and the most interesting results are shown in 
the following tables : 
