The existing fuel jetty platform at Thanckes fuel station is over 60 years old, hence the need for replacement and new modern facilities for fuelling. The government backed a multi-million-pound investment at the depot, which will guarantee its compliance with current standards and safety regulations within the sector.
Work began in 2018. Marshall steel stairs provided the jetty approach control office support frame inclusive of; main support steel, access stairs, perimeter and stair safety balustrade and kick-flat, open mesh safety decking, and connection design service for all items. With a total weight of around 40 tonnes of hot rolled steel, blast cleaned and painted to BS EN 12944 for the serviceability of a C5-M atmospherically environment.
Splicing main members makes for manoeuvrable-size assemblies
The initial design of the jetty approach control office support frame aimed to provide a fully assembled frame encompassing all the above items for fabrication, delivery, and erection in one piece. Due to the size of the assembled frame being 20 x 7.5m and overall foot print being 24 x 10.5m Marshall Steel Stairs deemed it necessary to break the frame down into more manoeuvrable size assemblies to be bolted together on site by carefully selecting the splice points of each member. By doing this, connection design for the whole platform had to take place, which seemed the right thing to do from both, a fabrication and CDM point of view. This would allow the single assemblies to be fabricated, manoeuvred, painted, transported, and erected with safety at the forefront of the project.
Due to the large loads applied to the frame and the large member sizes required, the connections design was critical and carefully co-ordinated throughout using BIM software, Trimble Connect, to allow regular reviews to take place.
Due to the frame’s location and marine protection requirements, the steel required anhydrous silica gel bags to be incorporated within the hollow steel sections to protect against the ingress of moisture and environmental issues, this had to be calculated on a volume basis. The next challenge to tackle was the lifting arrangement of the frame. The decision was made that the single assembly members would be transported to site and built up on a separate assembly barge located close to the jetty, to ensure minimal working over open water. Once it had been built up the frame could then be lifted in once piece into position and fixed. The 40-tonne frame needed specialist bespoke lifting lugs designing and procuring, these were positioned adequately to suit the frames dynamic centre of gravity, the design dictated that the lifting lugs be orientated in the same manner as the lifting chains to mitigate any unnecessary stresses in the lifting process. Using steelwork for the project has provided the scheme with a number of benefits, alongside the ease of splicing the main members and speed of construction, flexibility has also been designed into the steel frame, in case of any on-site modifications. This also allows for the required services to be fixed to the steelwork on site with ease.
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Important points or benefits:
- Peter Marshall Steel Stairs was responsible for the supply, fabrication, and offsite treatment of the steelwork along with supporting connection design calculations.
- Engineering design of connections was carried out by Peter Marshall Steel Stairs in-house and subcontract design departments. This was done in close coordination with CH2M and Volker Stevin.
- Co-ordination was also required with Volker Stevin to enable the fixing points of required services and the main jetty approach site cabin to be positioned and fixed with precision, thus saving time and resources.
- Peter Marshall Steel Stairs provided circa 75m² of 20mm ball proof open mesh flooring in accordance with regulations, this was co-ordinated via drawings and models to ensure an accurate and easy fit.
- We used the NC1 file export function to programme automated cutting and drilling machines in the workshop, as well as for nesting plate fittings in specialist nesting software.
- The 3D model is used to visualise and report which steel members had been completed, checked, and issued for fabrication. We also create specific representation settings to allow us to view object groups in different colours, for example, paint / galvanising codes, phased member groups, Bought out items, Material grades and on hold / outstanding items.
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