Tunnel Attenuator Structural Assessment

IAC Acoustics (WestConnex M4 East Project – Sydney, New South Wales, Australia)

IAC Acoustics required structural analysis and design verification of tunnel attenuators for the WestConnex M4 East project Parramatta Road and Underwood Road ventilation facilities (exhaust fan intake and discharge). The attenuator splitter and casing designs needed to meet the unique operating requirements for the ventilation facility including minimising pressure losses and peak shut-off pressure loading conditions during a fire event.

What we did:

  • Performed CFD analysis of attenuator splitter gap to determine pressure loss characteristics and fluctuating pressure loads (for fatigue assessment).
  • Performed structural FEA of attenuator splitter and casing designs considering strength and fatigue loading conditions.
  • Minimised plate thickness and section requirements and determined design compliance with standard AS 4100 for specified operating and ultimate loading conditions.
  • Modified lifting lug configuration to achieve minimum casing strength requirements as per standard AS 4991.


Avesta Consulting verified compliance of the design with standards AS 4100 and recommended design modifications to achieve minimum project specification requirements for strength, fatigue and flow performance.