DESIGN OF NON-STRUCTURAL PARTS

AND COMPONENTS OF BUILDINGS FOR

SEISMIC LOADS IN AUSTRALIA

John Woodside FIEAust, F.ASCE, FICE, FIStrucE, NER, RPEQ

Principal, J Woodside Consulting Pty Ltd

INTRODUCTION• The design of non-structural parts and components is just as

important as the structure itself.• In moderate to large earthquakes, failure of non-structural

parts and components invariably leads to difficulty in egressing the building.

• Occupants will face major business interruption and economic loss

• The structure of the building only represents about 25% of the total cost of the building.

• In Australia the NCC sets out the regulatory requirements for the design of buildings including nonstructural parts and components but generally ignored.

INTRODUCTION• The design requirements for nonstructural elements have

largely been ignored in Australia, as insufficient design and construction information has been available.

• Also architect, designers and services engineers do not have the experience or technical knowledge to design for seismic loads.

• As a result the design responsibilities of parts and components is either given to the builder/contractor, the supplier or the installer.

• Most of these will struggle with the concepts and as a consequence the statutory requirements have been in the past, effectively ignored except on a few larger projects.

DESIGN OF PARTS AND COMPONENTS

• When did it start ??

• Called up in first earthquake code AS 2121 in 1979.

• Also called up in the first edition of AS 1170.4 in 1993 in Section 5 and with its adoption in the BCA, but was largely ignored.

• Second edition of AS 1170.4 (2007) in Section 8 of the also required that all parts and components be designed for seismic loads.

• The paper explores some of the issues and problems based on the author's experience with the new Royal Adelaide Hospital and the design of non-structural components.

• It reviews what can be done to make all designers including architects, building services engineers and contractors aware of their statutory responsibility.

OLIVE VIEW HOSPITAL CALIFORNIA 1971

OLIVE VIEW HOSPITAL CALIFORNIA

• Hospital opened in December 1970 and designed to the then current seismic standards.

• Severely damaged only three months after it was open in the San Fernando earthquake on the 9 of February 1971.

• Three people lost their lives, two on life support and one killed by falling masonry.

• The hospital was abandoned and demolished in 1973.

• Redesigned and rebuilt and the structure performed satisfactorily in the 1994 Northridge earthquake but the building was unusable because of the failure of building services and nonstructural components.

• The ceiling services and nonstructural elements have now been rebuilt to a higher standard.

• What will happen next time????

Non structural damage overseas

•

EARLIER EARTHQUAKES IN AUSTRALIA – Adelaide 1954

•

EARLIER EARTHQUAKES IN AUSTRALIA – Meckering 1968

•

EARTHQUAKES IN AUSTRALIA

•Australia has an extensive record of earthquakes since settlement.

•Failure of non-structural parts and components is well documented.

•Significant earthquake in Adelaide in 1954.

•Meckering earthquake in WA in 1968 and about 78 buildings collapsed.

AS 1170.4 (1993)

• Section 5 of the Code required detailing and design of nonstructural parts and components excluding domestic structures.

• It was hoped that deemed to comply or industry based standards would be developed as a result of this code.

•Unfortunately these did not eventuate and except for some larger projects it was largely ignored.

NEWCASTLE EARTHQUAKE 1989

NEWCASTLE EARTHQUAKE 1989

Nonstructural damage included:-

•Failure of brickwork, ceilings, light fittings was widespread. •The new the opening of the new John Hunter Hospital was delayed by about 18 months and the damage cost was approximately $6 million.•Electricity companies suffered failure of switchyards.

FEMA USA• In the past earthquake engineering has focused on the

performance of structural systems and how to reduce structural damage and allow people to escape in the event of an earthquake. As we move toward to more comprehensive earthquake requirements and expectations of improved seismic performance, it is vital to understand the significance of non-structural damage and why we need to design for it”.

• Failure of nonstructural components may prevent people from egressing the building resulting in injuries and fatalities.

CANTERBURY EARTHQUAKES NZ 2011

• 185 people lost their lives in the earthquake of the 22nd of Feb 2011.

• Most of this loss of life was the CTV building.

• Royal commission reported "egress from a building during an emergency and the protection of the egress through route should be considered as a life safety issue, and consequently the means of as egress should perform adequately in an ultimate limit state event. This also applies to building elements that could fail and injure people underneath.

Structural engineers focus on the primary structure, with ancillaries structure generally being managed by the designer responsible for the architectural elements. There is often no overall supervision of the structure within the building by a person with knowledge of how the building is expected to behave in an earthquake“.

CANTERBURY EARTHQUAKES NZ

NEW ROYAL ADELAIDE HOSPITAL 2016

NEW ROYAL ADELAIDE HOSPITAL THE TIDE HAS TURNED

The NRAH required all non-structural parts and components to be designed for earthquake loads including:

• All services including ductwork, sprinklers, and the like,

• All partition walls and windows,

• All suspended ceilings and there were about 17 hectares weighing about 225 tonnes in total

• All door frames and joinery,

• All shelving,

• All clean rooms and so the list went on;

DESIGN SUSPENDED T- BAR CEILINGS TO THE NRAH

• The structural engineer provided the floor accelerations afloor and the expected storey drifts.

• This information then allowed Clause 8.2 of AS 1170.4 to be used for designing parts and components.

• Lateral forces were about 20% of the seismic weight and the vertical loads were 10% of the seismic weight although vertical loads did not apply to all elements.

• Clauses 8.2 and 8.3 requires a component factor Rc = 2.5 i.e. all fixings to be designed for an ultimate load of 2.5 x 20% = 50 % of the ultimate load.

• All fasteners (fixings) had to be designed for cracked concrete with seismic rating.

• This requirement for the seismic design of parts and components, shook up all subcontractors and the fixing industry in SA.

• Many sub-contractors tendered on the project without fully understanding these requirements initially, even though they were clearly set out in the specification and drawings.

DESIGN OF THE SUSPENDED T- BAR CEILINGS NRAH

•

DESIGN SUSPENDED T- BAR CEILINGS TO THE NRAH

• While some minor damage to the ceiling can be expected under seismic actions, the main requirements for designing suspended T-bar ceilings for earthquake actions is to avoid significant damage and collapse.

• Some minor damage as some local buckling or bending of the T-bar system or local damage to the tiles particularly at the edges.

• Significant damage would be the collapse of ceiling system, the falling of a large number tiles to the floor below or the dropping of services such as light fittings supported by the ceilings to the floor below.

DESIGN SUSPENDED T- BAR CEILINGS TO THE NRAH

•To provide a suspension system strong enough to resist lateral forces imposed upon it without failing.

•To prevent ceiling tiles in a T-bar system and plasterboard sheets from fixed ceilings falling to the floor.

•To avoid light fittings and duct registers supported by the ceiling falling to the floor below.

SA GOVERNMENT

CONCLUSIONS• Seismic design of nonstructural parts and components is a

relatively simple and basic structural engineering design task by applying a “notional” lateral and vertical seismic forces and then designing for them.

• The NRAH project has clearly shown, that after some initial efforts, the design of nonstructural components is possible, practicable and not excessively expensive.

• There is now enough experience in the industry to design all non-structural elements for all projects in Australia.

• It is time we got this part of the seismic design jigsaw in Australia in place for the effective design of parts and components for seismic loads.