The Crucial Role of Seismic Anchors in Australian Buildings

Australia may experience fewer major earthquakes than countries located directly along active tectonic plate boundaries, but earthquake risk remains an important consideration in Australian building design.

Earthquake actions can affect structural elements as well as non-structural building components such as mechanical equipment, electrical systems, pipework, ductwork, ceilings, partitions and architectural features.

When these components are not appropriately restrained, earthquake movement may cause them to slide, overturn, fall or become detached from the supporting structure. This can create risks to occupants, damage essential building services and prevent a building from remaining operational after an earthquake.

Seismic anchors and engineered restraint systems help transfer earthquake forces safely into the building structure. Their correct selection, design and installation are therefore essential to effective seismic restraint engineering in Australia.

Does Australia Require Earthquake Design?

Earthquake actions are relevant to building design throughout Australia.

The National Construction Code references AS 1170.4, Structural design actions – Earthquake actions in Australia, for the determination of earthquake actions. Section 8 of AS 1170.4 addresses certain non-structural building parts and components that may need to resist horizontal and vertical earthquake forces.

These components may include:

• Mechanical equipment

• Electrical equipment

• Fire-suppression systems

• Smoke-control systems

• Boilers and plant

• Ceilings

• Partitions

• Parapets

• Architectural appendages

• Other non-structural building elements

The earthquake design requirements applying to a component depend on factors such as the building classification, importance level, location, component weight, mounting height and the consequences of failure.

What Are Seismic Anchors?

Seismic anchors are fixings used as part of an engineered system to connect equipment, supports or building components to the primary structure.

They may be used to transfer earthquake forces into:

• Concrete slabs

• Concrete walls

• Structural steel

• Masonry

• Timber framing

• Engineered support frames

Common anchor systems include:

• Mechanical expansion anchors

• Undercut anchors

• Screw anchors

• Bonded or chemical anchors

• Cast-in anchors

• Anchor channels

• Through-bolts

• Proprietary fastening systems

An anchor should not be considered suitable for seismic use merely because it is strong under normal static loading.

Seismic performance may require consideration of cyclic loading, cracked concrete, edge distances, anchor spacing, concrete strength, installation conditions and the behaviour of the complete connection.

AS 5216 and Concrete Fastening Design

The design of safety-critical post-installed and cast-in fastenings in concrete is addressed by AS 5216.

The current edition, AS 5216:2026, Design of post-installed and cast-in fastenings in concrete, specifies minimum requirements for fastenings used to transfer loads into concrete in safety-critical applications. It replaced AS 5216:2021 in April 2026.

Depending on the application, anchor design may need to assess potential failure modes such as:

• Steel failure

• Concrete breakout

• Concrete pull-out

• Concrete splitting

• Pry-out failure

• Edge failure

• Combined tension and shear

• Failure of the supporting fixture

• Failure of the surrounding structure

The engineer must consider the entire load path rather than assessing the anchor product in isolation.

Why Seismic Anchors Matter

During an earthquake, building components experience acceleration and movement.

Even equipment that is securely supported under normal operating conditions may generate substantial forces when the building moves beneath it.

Seismic anchoring helps prevent:

• Equipment sliding across a floor

• Plant overturning

• Suspended services falling

• Supports separating from the structure

• Pipes and ducts rupturing

• Electrical equipment becoming disconnected

• Fire services being damaged

• Components blocking evacuation routes

• Heavy objects striking occupants

The Australian Building Codes Board has highlighted that failure of non-structural components can cause injury, rupture fire-sprinkler pipework, damage electrical equipment, obstruct exits and make a building unusable following an earthquake.

Seismic Anchors for Mechanical Equipment

Mechanical plant often requires seismic restraint because of its weight, location and importance to building operation.

Equipment that may require engineered restraint includes:

• Air-handling units

• Chillers

• Cooling towers

• Condensers

• Pumps

• Fans

• Boilers

• Heat exchangers

• Packaged air-conditioning units

• Rooftop mechanical equipment

• Mechanical control panels

The seismic design may include anchors, brackets, frames, braces or restraint cables.

The engineer must also consider whether the equipment is rigidly mounted or supported on vibration isolators.

Equipment installed on springs or isolation pads may move differently from rigidly fixed equipment and can require specialised seismic restraint details.

Seismic Restraint for Ductwork

Suspended ductwork can move laterally and longitudinally during an earthquake.

Where seismic restraint is required, duct systems may need:

• Transverse bracing

• Longitudinal bracing

• Trapeze support strengthening

• Bracing rods

• Proprietary seismic brackets

• Structural anchors

• Flexible connections

• Clearance from nearby services

The seismic braces must transfer forces through the duct supports and anchors into an adequate structural element.

Fixing seismic braces to lightweight ceilings, non-structural framing or unsuitable substrates may not provide a reliable load path.

Seismic Restraint for Pipework

Pipework may require seismic restraint to reduce the risk of excessive movement, joint failure or damage to connected equipment.

Relevant services may include:

• Fire-sprinkler pipework

• Hydrant services

• Chilled-water pipework

• Heating-water systems

• Plumbing services

• Gas pipework

• Medical-gas systems

• Process pipework

Seismic pipe restraints may include transverse and longitudinal braces, anchors, guides and flexible connections.

The design must allow for expected thermal movement while still providing adequate earthquake restraint.

Seismic Anchors for Electrical Services

Electrical and communications equipment may also present a significant safety or operational risk if it moves during an earthquake.

Seismic anchoring may apply to:

• Electrical switchboards

• Transformers

• Battery cabinets

• Uninterruptible power supplies

• Generators

• Cable trays

• Busduct systems

• Communications racks

• Control cabinets

• Emergency power equipment

The restraint design should consider the equipment’s mass, centre of gravity, fixing arrangement and supporting structure.

Tall or narrow cabinets may be particularly vulnerable to overturning if they are not adequately anchored.

Protecting Essential and Life-Safety Systems

The importance of seismic restraint increases where failure could affect emergency response, fire safety or continuity of essential services.

Critical systems may include:

• Fire-sprinkler systems

• Smoke-control equipment

• Emergency power

• Fire-alarm systems

• Hospital equipment

• Medical-gas services

• Data-centre infrastructure

• Communications equipment

• Emergency water systems

In these situations, seismic restraint does more than prevent physical damage. It can help preserve the operation of systems needed during and immediately after an earthquake.

Seismic Anchors in Cracked Concrete

Concrete in a building should not automatically be assumed to remain uncracked.

Structural loading, shrinkage, temperature effects and earthquake movement may cause cracks to form or open around an anchor location.

Where cracked concrete is relevant, the anchor system must be suitable for the applicable concrete condition and design actions.

The engineer may need to review:

• Anchor product assessment information

• Suitability for cracked concrete

• Seismic performance classification

• Concrete strength

• Embedment depth

• Edge distance

• Anchor spacing

• Installation orientation

• Hole-cleaning requirements

• Installation torque

Using an anchor that has only been assessed for uncracked concrete may be inappropriate for a safety-critical seismic application.

Mechanical Anchors and Chemical Anchors

Both mechanical and bonded anchors can be used in engineered fastening systems, provided they are suitable for the application and installed correctly.

Mechanical anchors

Mechanical anchors typically develop resistance through expansion, interlock or bearing against the concrete.

They may include:

• Expansion anchors

• Screw anchors

• Undercut anchors

• Concrete screws

Their performance can be affected by embedment, installation torque, concrete condition and proximity to edges.

Bonded anchors

Bonded anchors, often called chemical anchors, use resin or adhesive to bond a threaded rod or reinforcing bar into a drilled hole.

Their performance may be influenced by:

• Hole diameter

• Embedment depth

• Hole-cleaning procedure

• Concrete temperature

• Moisture

• Adhesive curing time

• Installation direction

• Product shelf life

• Installer competency

Substituting a different resin, threaded rod or installation method without engineering review can invalidate the original anchor design.

The Importance of Anchor Installation

Even a correctly designed seismic anchor can perform poorly if it is not installed in accordance with the approved design and manufacturer’s instructions.

Common installation problems include:

• Incorrect drill-bit size

• Insufficient embedment

• Poor hole cleaning

• Incorrect installation torque

• Anchors positioned too close to an edge

• Reduced anchor spacing

• Installation into damaged concrete

• Use of an unapproved anchor product

• Cutting or modifying anchors

• Installing anchors through unsuitable finishes

• Failure to observe adhesive curing times

Where anchors form part of a safety-critical connection, installation records and inspections may be required.

Anchor Location and Reinforcement

The position of reinforcing steel can affect where an anchor can be installed.

Drilling through reinforcement without approval may:

• Reduce the capacity of the concrete element

• Damage critical reinforcement

• Affect durability

• Compromise fire resistance

• Create an unapproved departure from the structural design

Reinforcement scanning may be required before drilling into existing concrete.

If the specified anchor position conflicts with reinforcement, the revised location should be assessed by the engineer rather than moved arbitrarily on site.

Anchoring into Structural Steel

Seismic restraints may also connect to structural steel using:

• Bolted brackets

• Beam clamps

• Welded connections

• Proprietary channel systems

• Steel support frames

The capacity of the steel member and connection must be assessed.

A clamp or bracket should not automatically be assumed capable of resisting seismic loads merely because it can support the equipment’s vertical weight.

Where welding is proposed, the design should consider the steel grade, weld size, access, surface coatings and any restrictions imposed by the structural engineer.

Anchoring into Masonry and Other Substrates

Concrete anchor capacities should not be applied directly to masonry, hollow blockwork, lightweight panels or other substrates.

Anchoring into masonry may require consideration of:

• Masonry unit type

• Grout condition

• Mortar strength

• Edge distance

• Embedment

• Hollow or solid construction

• Condition of the existing wall

• Load direction

In some cases, a separate support frame connected to the primary building structure may provide a more reliable seismic load path.

Selecting the Correct Seismic Anchor

Anchor selection should be based on engineering assessment rather than convenience or product availability.

The design process may consider:

• Seismic design force

• Tension and shear loads

• Concrete strength

• Cracked or uncracked concrete

• Anchor diameter

• Embedment depth

• Edge distances

• Anchor spacing

• Fixture thickness

• Corrosion exposure

• Fire requirements

• Installation conditions

• Product assessment documentation

• Supporting structural capacity

The specified anchor forms part of the certified engineering design.

Any proposed substitution should be reviewed before installation.

Corrosion Resistance and Environmental Exposure

Anchors must remain durable throughout the expected life of the building or equipment installation.

Environmental conditions may include:

• Internal dry environments

• External weather exposure

• Coastal environments

• Plant rooms

• Wet areas

• Chemical exposure

• High humidity

• Industrial environments

The required material or protective coating may vary depending on the exposure.

Corrosion can reduce the cross-sectional area and strength of an anchor, so anchor durability should be considered alongside its initial structural capacity.

Seismic Anchor Testing and Product Evidence

Product testing and technical assessment information can help engineers determine whether an anchor is suitable for a proposed seismic application.

Relevant evidence may address:

• Static resistance

• Cyclic loading

• Cracked-concrete performance

• Seismic performance

• Installation conditions

• Durability

• Fire exposure

• Permitted base materials

However, product approval or test data does not replace project-specific engineering.

The engineer must still determine the design forces, check the connection geometry and confirm that the supporting structure can carry the resulting loads.

Site-Specific Seismic Restraint Design

A generic seismic detail may not be suitable for every building.

Site-specific seismic restraint engineering may be necessary where:

• Equipment weights differ from the generic design.

• Support spacing has changed.

• The building has a higher importance level.

• Equipment is mounted at a greater height.

• The proposed anchor substrate is different.

• Vibration isolators are used.

• Services are arranged differently.

• Anchor edge distances are restricted.

• The installation falls outside the product limitations.

The design should reflect the actual equipment, support layout and building structure shown on the project drawings.

Engineering Documentation and Certification

Seismic anchor and restraint documentation may include:

• Seismic design calculations

• Equipment schedules

• Bracing layouts

• Anchor schedules

• Support details

• Certified engineering drawings

• Installation requirements

• Inspection hold points

• Product information

• Engineering certificates

In Queensland, a Form 15 may be provided for a seismic restraint design or specification where appropriate.

Following installation, the building certifier may also require inspection documentation or another applicable compliance certificate.

Certification requirements vary between Australian states and territories.

Inspection of Seismic Anchors

Inspection helps confirm that the seismic anchors and restraints have been installed in accordance with the certified design.

An inspection may review:

• Anchor type and diameter

• Number of anchors

• Embedment

• Anchor spacing

• Edge distances

• Supporting substrate

• Bracket configuration

• Brace angle

• Connection to equipment

• Installation torque

• Chemical-anchor installation records

• Differences from the approved drawings

Where physical inspection is not practical, the engineer may request clear photographs, marked-up drawings, installer records and product documentation.

Important connections should be inspected before ceilings, wall linings or other finishes conceal them.

Common Seismic Anchor Design Mistakes

Common problems include:

• Selecting anchors based only on equipment weight

• Ignoring horizontal earthquake forces

• Assuming all concrete anchors are seismically suitable

• Fixing restraints to non-structural elements

• Failing to check concrete edge distances

• Using generic details outside their limitations

• Substituting anchor products without approval

• Ignoring cracked-concrete requirements

• Failing to consider equipment overturning

• Omitting restraint for flexible or vibration-isolated equipment

• Providing braces without checking the complete load path

These issues can be reduced through early engineering coordination and clear installation documentation.

Why Early Seismic Coordination Matters

Seismic restraint should be coordinated before building services are installed.

Early design allows the project team to:

• Identify equipment requiring restraint

• Establish accurate equipment weights

• Confirm suitable structural fixing points

• Coordinate brace locations

• Avoid clashes with other services

• Specify appropriate anchors

• Determine inspection requirements

• Include restraint costs in project planning

Attempting to add seismic braces after services have been installed can result in congestion, unsuitable fixing locations and costly modifications.

Building Safer and More Resilient Australian Structures

Seismic anchors are a small but critical part of a complete earthquake-resilient building system.

Their effectiveness depends on more than the strength of an individual anchor. The equipment, bracket, brace, fastener, supporting substrate and primary structure must all form a continuous and reliable load path.

By using appropriately assessed anchor products, completing project-specific engineering calculations and verifying installation, Australian project teams can reduce the risk of non-structural components becoming damaged or dislodged during an earthquake.

Effective seismic anchor design and earthquake restraint engineering help protect occupants, preserve essential building services and improve the resilience of Australia’s built environment.