Structural Engineering Slide Library

Forth Road Bridge, Scotland (1964)

Thumbnail Image Image-GoddenG2 Site of the Forth Road Bridge crossing, taken from the north shore looking south. At this stage the concrete end towers have been constructed, and work has started on the main towers. The bottom of the north tower can be seen. (Scotland)
Thumbnail Image Image-GoddenG3 Forth Road Bridge. After the construction of the main towers and the cable spinning. View of the south shore shows in the foreground the construction of the approach spans (see also GoddenA42) with sections of the box girders beside the concrete bent. (Scotland)
Thumbnail Image Image-GoddenG4 Forth Road Bridge. View from the top of the south main tower. The so-called 'cable-spinning' operation, originally devised by Roebling, consists of unreeling a continuous length of wire back and forth across the bridge until a 'strand' is built up. The wire is looped round the wheel of the traveling sheave (shown) which is connected to an endless hauling rope. (Ref: 'The Engineer' Jan. 1962 p.62) (Scotland)
Thumbnail Image Image-GoddenG5 Forth Road Bridge. Top of south tower showing the first wires of the cable being laid over the saddle. The wires are 0.196 in. diameter with an ultimate strength of 100 tons per sq. in. 314 wires will form a 'strand' and there will be 37 stands in each cable: 11,618 wires and 23.5 in. diameter. The division of the cable into strands is seen in GoddenG8 at the anchorage. (Scotland)
Thumbnail Image Image-GoddenG6 Forth Road Bridge. Looking up the cable to the south tower saddle. Note the bundles or 'strands' of wires that will form the finished cable. The individual wires are color-coded to assist in the spinning operation. (Scotland)
Thumbnail Image Image-GoddenG7 Forth Road Bridge. Cable saddle at the top of the side tower. Note the size of the saddle which has to take the resultant vertical component of cable tension due to the angle change in the cable at this location. (Scotland)
Thumbnail Image Image-GoddenG8 Forth Road Bridge. South anchorage of one cable. Each strand is anchored round one red yoke tied back to the anchorage by two screw rods. (Scotland)
Thumbnail Image Image-GoddenG9 Forth Road Bridge. Close-up of the cable anchorage yokes in GoddenG8. Note: GoddenG8 and GoddenG9 were taken at the construction stage shown in GoddenG10-G15. (Scotland)
Thumbnail Image Image-GoddenG10 Forth Road Bridge. After the cable has been laid, the stiffening truss is constructed symmetrically about both main towers. This view, together with GoddenG11, taken before the truss has reached the side towers or met at midspan, shows the geometry of the finished cable supporting the unfinished truss. (Scotland)
Thumbnail Image Image-GoddenG11 Forth Road Bridge. View of the south cable anchorage at the same construction stage as in GoddenG10. Note the scale from the figures to the left of the anchorage. (Scotland)
Thumbnail Image Image-GoddenG12 Forth Road Bridge. Shows the elevation and end view of the stiffening truss at the same stage of construction. The truss has not quite reached the south side tower. (Scotland)
Thumbnail Image Image-GoddenG13 Forth Road Bridge. The gap at midspan between the two ends of the stiffening truss is more than twice the gap in GoddenG12 as the truss is constructed symmetrically about each main tower. Note the shape of the cable which is relatively flat over the unloaded center section. (Scotland)
Thumbnail Image Image-GoddenG14 Forth Road Bridge. End view showing the deflected shape of the stiffening truss before the dead load is evenly applied to the cable over the full span. At this stage the joints in the lower chord of the truss are not connected in order to permit this gross vertical curvature of the truss. When the truss is complete, the cable will adopt its final configuration and the joints will be connected. (Scotland)
Thumbnail Image Image-GoddenG15 Forth Road Bridge. Close-up of the unfinished end of the stiffening truss taken from the south side tower. The truss has a warren configuration with verticals, and the top and bottom chords are box sections. Note the scale of the truss from the figures on the near vertical member. (Scotland)
Thumbnail Image Image-GoddenG16 Forth Road Bridge. View of the completed bridge taken from the south shore. (Scotland)
Thumbnail Image Image-GoddenG17 Forth Road Bridge. Monument at the south shore view point commemorating the opening of the bridge on September 4, 1964. (Scotland)

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