Light and stable Structures: DYWIDAG Post-Tensioning Tendons for Tower Two at Collins Square in Melbourne
Currently, one of the largest commercial construction projects in Australia is under construction at the centrally located Collins Square in Melbourne’s Western Precinct. It involves the construction of a large block of buildings that includes 6 towers and a renovated, historical warehouse that will accommodate offices, retail facilities and restaurants on an area of over 250,000m².
DYWIDAG Strand and Bar Post-Tensioning Systems were used in levels 26 and 27 of the 39 story high Tower Two at 727 Collins Street. The contractor, Form 700, together with its partner company Postenco, designed an alternative solution for the complicated structural design of both levels. In order to comply with the design of the architects, no columns could be used in the façade of level 26 on one side of the building.
As there are 12 more stories above level 27, not having these columns in the façade created structural instability that was initially solved with passive reinforcement.
As an efficient and light-weight alternative, Postenco proposed active post-tensioning using eight 57mm Ø DYWIDAG Bar Tendons and DYWIDAG Strand Tendons with Type 6837 MA Anchorages.
The large steel “triangles” on level 26 were tensioned back to the central core of the building using DYWIDAG Bar and Strand Post-Tensioning Tendons. In total, 8 Fep 1,050N/mm2 DYWIDAG Bar Tendons with nuts, couplers and plates were cast into the floor and the walls of the core. The DYWIDAG Strand Tendons were installed in the heavy beams on level 27, tying back the steel triangles of level 26.
All 37 strands in one cable were installed parallel to prevent entangling and friction of the individual strands in each cable bundle. Due to limitations in stressing space and maximum weight restrictions, stressing was carried out using a monostrand jack. In total, 10 DYWIDAG Strand Post-Tensioning Tendons were used. DSI not only supplied the necessary DYWDAG Post-Tensioning Tendons, but also supported the contractors in the correct use of the post-tensioning systems. The DYWIDAG Post-Tensioning Systems were installed, stressed and grouted by the subcontractor Postenco.