A flatbed truck delivers the lead-rubber bearing units to the Wexford site, each isolator weighing close to two tonnes and wrapped in protective sheeting. The crane operator works with the setting-out engineer to position the bearings on the lower plinth, checking the level with a digital inclinometer before grouting begins. At our laboratory, we have already tested the prototype bearings under a full-scale dynamic test protocol to confirm the shear modulus and equivalent viscous damping match the design report. For a town like Wexford, where the bedrock lies beneath variable depths of glacial till and weathered slate, the isolators must accommodate both the seismic demand and the long-term settlement characteristics of the ground. We often combine the isolator design with a mat foundations assessment to distribute load evenly across the till, and we coordinate with the test pits crew to verify the depth to competent bearing strata before the plinth reinforcement is tied.
Base isolation in Wexford is not about surviving a large earthquake; it is about keeping a hospital or data centre operational immediately after a moderate event that would crack a fixed-base structure.
Frequently asked questions
Is base isolation required for buildings in Wexford given the low seismicity?
For most residential and commercial buildings, base isolation is not mandatory under the Irish Building Regulations. However, for essential facilities such as hospitals, emergency response centres, and data centres, or for structures with high-value contents, the post-earthquake functionality requirement often justifies isolation. The Eurocode 8 consequence class CC3 structures benefit most, and the additional cost of the isolators and moat detailing is offset by reduced structural member sizes and damage avoidance.
How much does a base isolation design package cost for a Wexford project?
A complete base isolation design package for a Wexford building, including site-specific hazard analysis, isolator sizing, non-linear time-history modelling, and prototype test specification, typically ranges from €4,340 to €7,560 depending on the structural complexity and number of ground motion pairs required. The bearing procurement and testing costs are separate and depend on the number and diameter of the isolators.
What ground investigation is needed before designing base isolators for a Wexford site?
We need a shear wave velocity profile to at least 30 metres depth, which can be obtained from a MASW survey or seismic refraction. Additionally, boreholes with SPT data and laboratory classification tests on the glacial till are needed to confirm the site class and check for liquefiable layers. The site-specific response analysis requires the Vs30 value and the depth to bedrock, which in Wexford can vary from 5 metres near the town centre to over 20 metres in the outlying drumlin areas.
