Strengthening existing buildings to achieve a higher performance in earthquakes is an everyday task for structural engineers in New
Three or more main questions arise:
- Is the building capable of resisting the demands
of earthquakes under the ULS and SLS stated limits and fulfilling the current code requirements?
- What is the residual life cycle of the existing
- Is there a continual deterioration of the
existing structure caused by active corrosion, aggressive environmental
conditions, or concrete carbonation?
For most structural
engineers, the first question is obvious. How about the others?
Unfortunately, the answer is that the majority of structural engineers don’t take into
consideration the residual life cycle of the existing structural system and the
influence that this may have on the future capacity of the structure.
Current international legislation provides solutions and
quality control measures for every aspect related to maintenance, structural
integrity and repair.
From simple aspects like paint and humidity control, to more
complex ones like concrete restoration, structural strengthening and cathodic
Modern codes like EN 1504 ensure that structural maintenance
is now a much more difficult assignment requiring specialist knowledge from
EN 1504 recognises that failure of repairs at any structural
level including seismic upgrade and repair can lead to unprecedented dangers
affecting not only the repair and the correct structural analysis, but also the investments
and lives of the occupants.
Today structural engineers should be able to substantiate
their solutions, assumptions and safety factors via a strict protocol of Maintenance
and Durability Analysis. The protocol should be able to safeguard that, ifthere
are no specific needs that would eventually compromise the selected solution, (i.e.
active corrosion of reinforcement or low alkalinity concrete), then the
functional service life of the solution can be well defined through a series of
tests. For example, EN 1542 defines the adhesion of FRP repairs. This means that every step related to the
application of the selected repair method can be warranted via the necessary EN
standards. (There are more than 110 standards
accompanying repairs from chemical anchorage to the application of shotcrete.)
In Europe, there were growing concerns for more than 40
years that the performance of any structure was profoundly affected by time and
exposure. In the1990s, these concerns
justified the creation of special Task Groups of specialists working on the development
of legislation covering Structural Maintenance.
In 2000, all 10 parts of EN 1504 – Repair and Protection of
Concrete Structures - was introduced and is now mandatory across the EU-27.
This means that the only way to add value to existing
structures is through depth of knowledge
and by using the latest design tools under international legislation.
Here at Harrison Grierson, by working in conjunction with
relative departments (Structural Analysis, Inspection, Material Selection and
Quality Control) we ensure that our solutions are the result of the best knowledge
We believe that the New Zealand engineering profession is mature enough to accept the challenge and
incorporate the domestic and international codes for durability and maintenance
into their practice.
This thought leadership article by Ioannis Prionas, team leader of Structural
engineering at Harrison Grierson,
raises questions about whether New Zealand should be adopting
international regulations relating to the structural integrity and life cycle of
buildings.and how structural engineers need to look beyond
the immediate repairs to the overall health and condition of a building.
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