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Excalibur Screwbolts

PLUS Bolt A Long Lasting Solution for Crossrail

It’s a story of a great British innovation being used in a great British engineering project.

When consultants for Europe’s biggest underground construction project were looking for a bolt to secure platform edge screens at stations, Crossrail stipulated a design life of 120 years. Standard ETA approved fixings have an estimated design life of 50 years, so this may have seemed a tall order. Not, however, to Screwbolt specialists Excalibur Screwbolts. Excalibur, highly reputed and awarded for their twin helix threaded concrete screw anchor, had already developed a new and revolutionary Excalibur Screwbolt that has extremely high levels of corrosion resistance.

The ‘Excalibur Screwbolt PLUS’ is an enhancement of their original Excalibur Screwbolt. Not only is the Screwbolt PLUS rust resistant, it also has high performance tensile and shear characteristics.

In addition to their own extensive salt spray testing, samples of Excalibur Screwbolts PLUS were submitted to Ford Motor Company for their 9 Week Accelerated Cyclic Corrosion Test for evaluation. Excalibur Screwbolts PLUS completed tests with no signs of corrosion. In comparison low grade stainless steel sample subjected to same corrosion tests showed extensive areas of red rust.

Data from further independent salt spray testing supports the technical opinion that the Screwbolt PLUS will last in excess of 120 years. "It’s a great leap technologically and it takes our Screwbolts performance to another level," says Excalibur’s Technical Manager Jim Clement.

Another challenge related to fixing the platform edge screens steelwork to the Crossrail (Sprayed Concrete) tunnel linings where particularly long bolts were required to overcome the variations in depth of concrete. Again Excalibur were able to deliver with a suitably long PLUS Studbolt to solve this problem.

Crossrail then commissioned Vinci Technology and Imperial College London’s Department of Engineering to conduct stringent testing of the Excalibur Screwbolt PLUS to ensure they complied with their strict requirements and could withstand the relevant stresses and strains involved with the designated design life into the sprayed concrete tunnel lining. Tests conducted included tension and shear tests, cyclic tension and shear tests and mock up simulation tests to top and side connections. The results of the tests undertaken proved to be positive and the products or approved equivalent were added to the Crossrail design specification.

In July 2015 Excalibur Screwbolts PLUS were used in the installation of the platform edge screens at Tottenham Court Road station. Installation of the brackets was undertaken by specialist contractor Lakesmere Ltd on behalf of main contractor Laing O’Rourke. All parties involved have collaborated together to ensure speedy and safe completion of the works.

"We believe it’s a great improvement in both durability and performance on other bolts currently available, and 6mm/8mm and 10mm products are to be developed" says Jim Clement, delighted not only with their product, but also pleased that Excalibur Screwbolts Ltd was able to provide a solution to a problem on this landmark British project which has also benefited the UK economy and other companies involved in the supply chain. A great British story indeed.







PLUS Bolt high corrosive resistant anchor

Design Tables based on ETAG 001 pt3

Table 1: Mean Ultimate resistance (Nru,m from test results)
Anchor Size (mm) 10 12 16 20
Hef nominal (mm) - 90 130 120
Non-Cracked Concrete - C30 C30
C30
Tensile Nru,m [kN] - 35.13 64.36 77.82
Shear Vru,m [kN] - 37.02 83.63 116.63


Table 2: Characteristic resistance (Nrk (1-k5%V)
Anchor Size (mm) 10 12 16 20
Hef nominal (mm) - 90 130 120
Non-Cracked Concrete - C30 C30 C30
Tensile Nru,m [kN] - 30.35 47.93 62.20
Shear Vru,m [kN] - 30.22 54.91 101.20


Table 3: Design resistance (Nrk = Nrk/ym) y taken as 1.8 (1.5 for steel/shear)
Anchor Size (mm) 10 12 16 20
Hef nominal (mm) - 90 130 120
Non-Cracked Concrete - C30 C30 C30
Tensile Nru,m [kN] - 16.86 26.62 34.55
Shear Vru,m [kN] - 20.14 30.50 67.40


Table 4: Recommended Load (Nrec = Nrd/y) y taken as 1.4
Anchor Size (mm) 10 12 16 20
Hef nominal (mm) - 90 130 120
Non-Cracked Concrete - C30 C30 C30
Tensile Nru,m [kN] - 12.04 19.01 24.67
Shear Vru,m [kN] - 14.39 21.79 48.10

For specific performance test data in Sprayed Concrete Lining, please contact us.



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Please note: From time to time, materials and specifications are changed to improve performance, please check for the latest information.