Containment enhancement for liquid gas tanks
North Walsham containment enhancement provided a bolted steel structure onto an existing RC/ masonry structure to provide second and third level protection against a catastrophic leak of the liquid gas housed in tanks contained within the bund.
MMI Engineering used STAAD pro to generate a model, which could analyze the applied loading of the proposed steelwork. TDS Midlands was provided with a Tekla model containing the steelwork members. The remit was to model in all the cladding plates, with several types of criteria dependent on location in relation to the gas tanks, model all connections in and adjust the model to suit the as-built conditions of the concrete and masonry structure along with adjusting any steelwork which fouled existing pipework. Surveys were provided in either Navisworks files or point cloud surveys, which were converted and inserted to the TDS model for review. The site had no grid lines for reference, just a datum point from which all models needed to be correctly orientated and positioned.
Some of the key challenges encountered included generating workable connections from those provided, including being physically able to construct the complex corner sections, which were subject to the highest loadings. The cladding plates to these areas had a huge number of bolts, which needed to be considered against the main steelwork connections for access and buildability. Furthermore, all steelwork was galvanized so the maximum capacities of the galv bath had to be considered whilst providing steelwork in the largest welded frames to aid site erection and minimize complex connections.
TDS provided IFC copies of our model for the contractor to carry out its own clash detection, particularly with regards to existing pipework (gas and fire suppression). The ability for Tekla to export and import IFC files was critical to the co-ordination of this element, and being able to share models quickly as situations arose was a real benefit. The 3D PDF tool was also excellent for demonstrating quickly to anyone with a PC, issues which need resolving. This especially helped in meetings where parties who weren’t necessarily directly involved in the complexities of the job could immediately see the issue being discussed without having to wade through a batch of drawings. All this reduced our requirement for creating sketches and general arrangement drawings trying to show these items.
Restricted site access meant models were critical to project success
The finished model had over 200 tonnes of steel and plate work, which was bolted together, to the concrete and masonry with almost 25,000 fixings. On a site where mobile phones were not permitted and there were only two site cameras, which could be taken onto site, the importance of thoroughly integrated models of the steelwork, concrete and services beforehand was critical. Only a few cladding plates needed manipulation on site to suit pipework, which had been moved after the models had been clash checked. This ensured minimal downtime for any site operatives who needed to speak to any of the design team.