The suspension bridge which spanned the Thames at Charing Cross, on the
site of the present railway bridge, was designed and constructed by Mr.
Brunel between the years 1841 and 1845. It consisted of a centre span of
676 feet, and two side spans of 343 feet each. Being intended for foot
passengers only, its width was 14 feet. The versed sine, or deflection
of the middle of the catenary, was 50 feet. The two river piers, which
still exist up to the level of the railway, and form piers of the
present bridge, were of brickwork, with large footings at the bottom, so
as to distribute the pressure over a considerable area. The whole
structure was made hollow and as light as possible. From the level of
the footway the piers were carried up as ornamental campanile towers,
the weight of the chains being taken by four solid pillars of brickwork,
7 feet 3 inches square, forming the angles. Mr. Brunel introduced here
many of the arrangements he had designed for the Clifton bridge. In
order that the pressure from the chains might be always vertical on the
piers, the saddles rested on rollers working in oil, on the level
surface of a large cast-iron bed-plate. By this arrangement it was
rendered possible for the chains of the land spans to leave the tower at
a greater inclination than those of the middle span, so that the chains
were made shorter, and as they were at a lower level where they met the
abutment, there was less change in their direction at that point, and
consequently less thrust on the brickwork. Freedom of horizontal motion
was also secured, so that, in the case of unequal loading of the spans,
the chains might accommodate themselves to the strains, and move
horizontally until equilibrium was restored. At each of the land
abutments the chains passed down over a fixed saddle, at an inclination,
to anchorages placed at the bottom of the abutment. The brickwork under
the fixed saddle was so disposed as to resist directly the thrust
resulting from the change of direction between the main chains and the
anchor chains. To resist any movement of the abutments, the piles on
which they rested were driven obliquely, with their heads inclined from
the river. These piles were very numerous, the abutments spreading out
so as to cover a large area at the foundations. Nearly all the spaces
between the longitudinal, cross, and outside walls were filled with
concrete, in order that the abutments might be as massive as possible.
The details of the brickwork in the piers and abutments showed Mr.
Brunel’s skill in the economical employment of this material. The chains
were constructed so that the sectional area was proportional to the
strain; the total area at the centre was 296 square inches, while near
the piers it was 312 square inches. There were four chains, two on each
side of the bridge, placed one above the other, and consisting each
alternately of ten and eleven links. The links were 24 feet long and 7
Public-domain text, read in full here on John Shaqi.
Reviews
Reviews
No reviews yet
Be the first to share your thoughts on this work.
Elsewhere in the archive
Join the Discussion
Join the discussion
Sign in to leave a comment or review.
Sign InorCreate an account