From Earthquake Risk to Resilience: Practical Seismic Strengthening of Rotorua Children’s Village

Hampton Jones was engaged to deliver seismic assessment and strengthening services for a multi‑building property comprising six structures, including a main building, gymnasium, boiler room, therapy building, woodworking shed, and bike shed/garage. The project required a comprehensive understanding of the site’s structural condition, seismic performance, and ground behaviour to ensure compliance with current New Zealand seismic standards while delivering a cost‑effective outcome for the building owner.

An Initial Seismic Assessment (ISA) was first undertaken across all six structures to determine their relative seismic risk. The assessment identified that the main building and boiler room achieved less than 67 percent of the New Building Standard (%NBS), classifying them as earthquake‑prone buildings. As a result, Hampton Jones progressed to a Detailed Seismic Assessment (DSA) for these two structures to better understand their seismic lateral capacity and performance in accordance with NZSEE and MBIE guidelines.

The detailed assessment process presented several challenges. Existing drawings indicated that the buildings were originally designed around 1978, with numerous additions and alterations completed over time. This resulted in inconsistencies between the available documentation and the as‑built condition of the structures, requiring careful engineering judgement, on‑site investigation, and interpretation of varying structural details to accurately determine seismic behaviour.

Ground conditions were a key consideration throughout the assessment. The site exhibited post‑seismic liquefaction and potential flow failure conditions, which presented a risk of ground deformation beneath the main building. Hampton Jones evaluated various ground failure scenarios and concluded that the potential life‑safety risk was minimal due to the light timber‑framed construction of the building. Any anticipated slope or flow failure was expected to occur gradually, providing sufficient warning for occupiers to evacuate the building safely during a seismic event. Additionally, the relative height difference across the site was less than the typical building length, meaning the building was unlikely to overturn and would more likely experience limited settlement.

Based on the findings of the Detailed Seismic Assessment, Hampton Jones developed practical and cost‑efficient seismic strengthening solutions tailored to each structure. For the main building, new GIB‑braced wall linings were installed at strategic locations to enhance lateral resistance and improve overall seismic performance. These targeted upgrades successfully increased the building’s seismic rating to 67 percent NBS, removing its earthquake‑prone classification.

For the boiler room, Hampton Jones recommended the installation of additional steel cross‑bracing within the roof space, along with new steel members between existing concrete columns and behind retaining walls. These measures significantly enhanced the lateral stiffness of the structure and improved its seismic resilience without unnecessary construction complexity.

Through a balanced and evidence‑based approach, Hampton Jones successfully upgraded both buildings to non‑earthquake‑risk status while minimising construction cost and disruption. The project demonstrates Hampton Jones’ capability in delivering seismic assessments for complex, existing buildings, developing targeted strengthening solutions, and providing integrated Structural Engineering, Building Surveying, and Quantity Surveying services that align technical compliance with commercial outcomes.