Prendos’ structural engineers are experienced in the design and strengthening of a wide range of single and multi-storey commercial, residential and educational buildings as well as providing robust solutions for historic structures and earthquake damaged buildings. Our structural engineering team provides structural design services to clients either as a stand-alone service or as technical support for design work undertaken by the Prendos architectural team. At the heart of business is cost effectiveness and safety. It’s about people in the end.

Specialist Services

• Seismic assessments and implementation of appropriate seismic strengthening solutions for single-storey and multi-storey buildings

• Design of precast concrete panels for single- and double-storey residential projects

• Structural upgrades of structures built reinforced concrete, reinforced and unreinforced masonry, steel, and timber

• Specific analysis, design and detailing of cold-formed steel structures

• Computer analysis of wind loading and seismic analysis of low- to mid-rise office/residential/apartment buildings

• Structural peer reviews (design reviews)


New Builds

The 2011 Canterbury earthquakes and the 2016 Kaikoura earthquakes have required that New Zealand structural engineers adopt new and innovative structural design to incorporate the latest seismic resisting systems.

Our structural engineers are pioneering seismic systems to meet the upgraded risk in Canterbury, which is simultaneously progressing the profession throughout the country.

Our focus is to inform clients of the level of seismic resilience prescribed by the NZ Building Code, and to implement low damage systems that increase this resilience beyond minimum requirements.


What Property Owners Need to Know

Seismic Assessment

You could be left bewildered by the array of earthquake assessments and reporting available to you and it may be difficult to determine what is appropriate. Suddenly “ISA“, “DSA” and “%NBS” have become part of everyday vocabulary for those in the construction industry and property investors.

The impact of these assessments can be significant and extensive.

The latest Guidelines for the Seismic Assessment of Existing Buildings, published in July 2017, have been fully revised to take into account the technical developments, including lessons from the Canterbury Earthquakes.

One of the requirements of the Building (Earthquake-prone Buildings) Amendment Act 2016 is that the Guidelines must be used as the basis for seismic assessments to determine whether or not a building is earthquake-prone.

Earthquake prone buildings are defined as being less than 34%NBS (34% New Building Standard). The recent change in the Seismic Assessment Guidelines alters our approach to assessments with less scope to rely on ‘judgement’. This change means that Initial Seismic Assessment reports are no longer lightweight exercises with no legal implications.

The Procedure

The assessment procedure begins with an Initial Seismic Assessment (ISA) where our experienced structural engineer performs site investigation to provide a qualitative insight on whether a building is potentially earthquake-prone. The ISA report is intended to quickly identify earthquake prone buildings using minimal resources.

A potentially earthquake-prone building (< 34%NBS) may require a Detailed Seismic Assessment (DSA) – a quantitative means requiring detailed calculations and analyses to establish more accurately whether a building is above the 34% threshold.

The analyses are typically carried out based on available existing drawings and building properties from the council, the measurement taken during site investigations, and if required, concrete scanning to determine the amount of reinforcement in the structures when drawing is not available.

The goal of a DSA is to provide a more accurate assessment of the building strength in resisting earthquake. If a building is rated earthquake-prone, we could ‘pinpoint’ the locations of the building that require strengthening through DSA.

After a DSA is completed, we provide a comprehensive report to our client that typically states the summary of the results, the %NBS of the building and the critical member governing this rating, and a seismic retrofit options if required.

At Prendos, we focus on finding the best solution to improve the earthquake resistance of a structure with strong consideration to minimise obstruction and cost.


Seismic Strengthening

Once a building owner enters the realms of structural strengthening, the issue becomes how close to %NBS is an appropriate goal.

The Guidelines recommend that all buildings below 34% NBS must be strengthened within different a time window, depending on the hazard the building poses.

Therefore, the seismic capacity of a building has now become a crucial consideration for building owners.

We recommend an ISA assessment is carried out when undertaking technical due diligence pre purchase. Having comprehensive knowledge of your building puts you in a more powerful position.

A building that has a high %NBS and grading is a highly marketable investment and conversely understanding a low %NBS and grading can be useful for planning future improvements.

Our structural team have had first-hand experience of the devastating effects of buildings that don’t perform as expected and as such, take great responsibility in making sure their work is of the highest standard – which isn’t always the most expensive option available.

Please contact us for more information

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