As soon as the side span steelwork was completed , concreting of the roadway on them was begun .
All the site connections in the suspended structure , with the exception of the joints between the battle deck panels and connections of crash barriers and parapets , were made with high-strength friction-grip bolts , tightened by impact wrenches . The other connections were site welded .
For works on erection of steelwork structure it was decided to use four safety net assemblies . Each assembly fully covered the length and width of three panels . Experience had shown that men work more quickly and freely on structural steelwork if safety nets are provided beneath them .
In the second pass the suspended structure was completed . Two erection gantries , intended to work out from the towers towards mid-span , were designed at site . Thus it was not necessary to wait for the 15-ton derricks to become free and be turned round .
The gantries were assembled on the second panel out from each tower . They completed the erection of the roadway battle decks , the cantilevered footway / cycle tracks , and the crash barriers , panel by panel as they moved towards mid-span .
Figure 11 : Erection of suspended structure in progress , with safety net Figure 12 : Erection of Steelwork in main span
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