Structural assessment of the Bryant Building revealed there was inadequate bracing and as a result the building was at risk to seismic loadings.
As a historically classified building, demolition was not an option, so a retro-fitted option was design, utilising structural steel, new concrete ground beams and micro-piles.
Ancor Loc Earth Systems were engaged by Isles Construction to carry out the Micro-piling package. Working within the building, with restricted access, a central city location and operating outside normal working hours meant the planning and programming stage was thoroughly thought out with contingencies in place for any foreseeable eventuality.
All Micropiles were drilled with a temporary casing system using our Comacchio MC400P Restricted Access drilling rig, The three types of Micro-piles were drilled to depths of 9.5m, 11m and 12.5m respectively, and founded within the cobbles/gravel river bed like strata that is present in the area. The micro-pile tendons were comprised from Williams 150KSI (high tensile, 1034MPa) All-Thread-Bar. Using a temporary casing system to prevent hole collapse and minimise grout loss, the anchors were grouted in place.
The Micropiles were tested to 870kN, with each one locked-off at the specified load. All anchors achieved the required loadings, and by working closely with Isles Construction the micro-piles were completed within time to enable the erection of the structural steel work and achieve the overall construction target date.