ADG Engineers (CPBJH West Gate Tunnel Project – Melbourne, Victoria, Australia)
ADG Engineers required thermal modelling of bridge concrete elements for the West Gate Tunnel Project (CPB Contractors John Holland Joint Venture). Thermal modelling of selected restrained concrete elements was required in accordance with CIRIA C660 to determine appropriate formwork insulation systems and concrete curing requirements/control measures to maintain temperature differentials within 20°C and maximum internal temperature less than 75°C.
What we did:
- Defined concrete transient head loads (i.e. heat of hydration-time curves) and insulation material thermal properties.
- Performed transient heat FEA of concrete elements considering heat of hydration rates, heat losses (to exposed surfaces and adjacent members) and maximum initial/ambient air temperature conditions.
- Determined temperature-time curves, compared peak temperature and temperature differentials with CIRIA C660 requirements and adjusted insulation material/thickness (i.e. equivalent thermal resistance) as required.
- Performed thermal-structural analysis of concrete element with highest temperature differential exceedance to confirm location of differential thermal expansion induced tensile-compressive stresses exceeding allowable stress limits (to determine occurrence and extent of cracking).
Outcome:
Avesta Consulting determined minimum formwork insulation requirements for the bridge concrete elements and confirmed adequate structural performance of the worst case concrete element considering localised regions exceeding maximum allowable temperature differential (20°C) and differential thermal expansion/constraint due to adjacent concrete members.
