Old bridge made safer with specially designed neck bolts from CSP
New Zealand’s urban and rural roads cover approximately 83,000 kms and, with a population of about 4.2 million people, New Zealand has one of the highest lengths of road per person in the world – making it challenging for the NZ Transport Agency and local Councils to keep motorists safe. Improving safety on our roads depends on four things – safer speeds, safer vehicles, safer drivers and safer roads and roadsides.
In January this year the two-lane bridge at Kaupokonui on SH45 - also known as the ‘Surf Highway’ due to the number of prominent surfing breaks that are accessible from it - was damaged when a car careened through the side barrier and plunged into the river. A review of the safety of the bridge, built in the 1950’s, showed that, whilst narrow, it was still sound but that the guardrail required a safety upgrade.
“During initial discussions on what was to be done with the bridge the engineers tried to retain the two lanes and develop a post that would be bolted to the side of the bridge deck maximising its width,” explains Richard Moody, Divisional Manager for Downer in Hawera. “But after investigation this option was ruled out and it was decided that the posts needed to be bolted to the top of the bridge deck.”
“We were asked to price posts for both options on the bridge with the top mounted bolt down option the one chosen by the engineers and NZ Transport Agency,” says Jeremy Mallender, Sales Engineer - Lower North Island for CSP. “This option includes neck bolts that are weakened to 40kN so they break more easily, putting less stress on the concrete bridge deck.”
Jeremy explains that even if another collision occurs on the bridge, the bolts are designed to shear off, allowing the Thrie-Beam™ Guardrail to prevent the vehicle from going into the river.
With new approaches and new X-350 Terminal Ends, the first phase of the safety upgrade to the old bridge was complete. Richard is pleased that this work has helped make the old bridge safer and should help prevent further serious crashes at this locale.
Contractors are now working on the Kaupokonui Bridge to reconfigure the guardrail so that the bridge can be reinstated with two lanes. After this work is complete a temporary speed reduction will be in place while additional strengthening work to support the new guardrail is carried out. This work will be complete in February 2017, at which time the speed reduction will be removed and the two lane bridge will be fully operational.