The Works Of Messrs. Schneider And Co.

140 MESSES. SCHNEIDER AND CO’. S WORKS. view unique of its kind, owing to the succession of bridges, and to the active navigation. 3. It was to be of such a width as to harmonise with that of the new avenue (328 ft.), that forms the approach on the Champs-Elysées side, while it was désirable not to cover too great a space of the river. Great difficulties arose, due to the bend of the Seine between the Concorde and Invalides Bridges, which ren- ders navigation particularly difficult at that part ; and in order not to increase these difficulties, it was necessary to maintain a sufficiently wide channel for the traffic, and especially for long tows, before passing under the Invalides Bridge. As, on this account, piers in the stream were in- (29| in.) over the abutment faces, so that the joints at tlie springing are 107.50 metres (353 ft.) distant from centre to ; centre. The bridge is 40 metres (131 ft.) wide between the hand- ‘ rails ; this width is occupied by a centre roadway 20 metres j (65 ft. 6 in.) in width, and by two footways, each 10 metres (32 in. 9 in.) wide. Longitudinally, the roacl is made with two inclines of 0.02 per metre (2 in 100), United at the ! centre by the arc of a circle, the chord of which is 32 metres (105 ft.) in length, and the radius 800 metres ! (2,624 ft.). Transversely the rise in the centre of the road is 20 centimetres (7-g- in.). The main structure of the bridge consists of 15 ribs Fig. 400. The Alexander III. Bridge, Paris. admissible, a low arch was tlie only type that allowed the fulfilment of all the conditions required, Fig. 400 gives an idea of the general design. The main girders are segmentai, and made with three joints ; the river spån is approached on each side by land spåns. The longitudinal centre line of the bridge coïncides with thai of the new avenue, and it crosses the river at an angle of 83 deg. 38 min. Tlie distance of 155 metres (508 ft.) between the faces of the abutments is divided into three parts, namely, land spåns each 22.50 metres (74 ft.) wide each, and the main spån, the clear length of which, measured in its centre line, is 109 metres (358 ft.) between the abutments. The shoes that carry the joints at the springing project .75 metre placed at equal distances apart. These ribs are formée! of a series of cast-steel voussoirs, the joints being normal to the median curve of the arch ; the voussoirs are designed so as to be wholly in compression, but to facilitate érection they are joined together by a few bolts. The cross-section of the inner voussoirs differs from that of the outer on es. The cross-section of the latter is E-shaped, but with a curved web formed on the outside and provided with ribs, while the inner voussoirs are I-sbaped, the width of all flanges being .600 metre (234 in-)> the total depth vary- ing from .850 metre (33r% in.) to 1.500 metre (59 in.). The webs are .050 metre (2 in. bare) thick throughout ; tlie thickness of the lower flange varies from .050 metre (2 in. bare) to .060 metre (2-| in. bare). The voussoirs have