SAFETY TEMPORARY WORKS INVOLVING THE INSTALLATION OF THE TOWER CRANE AT TREASURY GOOGLE Task Planning At Treasury Google the erection of the tower crane external to the footprint of the building was proving challenging. The perimeter of the Treasury Google building is enclosed by public roads, private commercial properties and live buried services. For safety reasons a different approach had to be investigated. PJ Hegarty appointed EirEng Consulting Engineers for their professional guidance on Temporary Works. The site is very restricted and the optimum location of the tower crane was determined to be within the footprint of the building instead of externally. The ideal location, which was decided in conjunction with PJ Hegarty, involved the design of a new steel frame, which was threaded down through the building and supported off the existing pile caps.
Safe System of Works Critical safety controls measures were planned,
implemented and monitored at all stages during the tower crane erection. PJ Hegarty’s early engagement with all third parties played a vital role in the successful installation of Tower Crane 4 due to the complex nature of all the works. Temporary works designs were developed, reviewed and approved by competent engineers and third-party verification. Structural and ground investigation surveys were carried out for structural stability.
Existing mains power supply was isolated within the electrical rooms and the site was diverted to generator power supply, to allow the installation of the ground anchors. PJ Hegarty conducted several high-risk workshops and review of safety documentation prior to commencing the works. A specialist steel contractor was engaged to install the structural steel element of the tower crane mast structure which was threaded through the building on each level. Exclusion zones, fall protection and ope management procedures were installed on all levels affected. Traffic Management Plans was set up on Grand Canal Street Lower. Ground conditions were compacted and tested prior to setting up the mobile crane. DCC derogation was obtained to carry out high-risk works out of hours. Nearby residents were notified of the activities within the monthly newsletter. Crane coordination meetings were held with adjacent sites, PJ Hegarty Treasury Annex and Collen Construction to ensure all Tower Cranes were manned during the lifting operations. PJ Hegarty crane Appointed Person was in attendance to monitor Lewis Cranes throughout all stages of the tower crane erection works. On completion of the works, both Lewis Cranes and Allianz carried out all testing and commissioning activities prior to issuing the statutory GA1 certificate. PJ Hegarty would like to express a huge thank you to all parties involved for the successful installation of the Treasury Google tower crane during August. 19/05/2023 Page 6
Figure 6 - Tekla Model of New Crane Support Structure
Figure 1 - Proposed Crane Position
Sequence of Works There was a significant number of structural surveys and enabling works to be completed in advance of the tower crane erection. These works consisted of the demolition of the plant room roof enclosure. Complete engineering calculations, drawings and investigation surveys to confirm the ground floor construction, ground slab and pile cap construction were completed. Concrete coring at the existing column locations to allow the new frame to be spliced and dropped into position from roof level. Installation of the new steel frame from ground floor to 5th floor level. Installation of the new steel grillage and finally the installation of the new tower crane. 231043 | Google Treasury Building Temporary Works 19/05/2023 The existing 1940s columns are plated steel columns. Testing undertaken during the 1980s extension confirmed that the steel was characteristic of grade 43a (S275) and that the allowable stresses for Gr43a may be assumed for design purposes. ii. The existing 1940 columns are cased in concrete and the overall size is approx. 600 x 600mm. the quality of the concrete is very poor and the connections between the beams and the column and also any splices in the column are unknown. iii. The 1980s extension 4 th to 5 th floor appears to be very robust however the steel frame is supported by the weakest column section from the 1940s (14” x 5 ½” 40lb/ft, 350 x 140 UB 60kg/m) iv. The concrete floors in the 1940s original building are identified on the drawings as 120mm thick and have a flat soffit, when measured on site these were found to be 180mm thick and a bonded cementitious screed appears to have been installed on top of the existing slab. v. The concrete strength of the floors is unknown as too are the strength and grade of the bolts used in the steel to steel connections vi. The foundations of the existing building are piled and the pile cap loads have been shown on the original 1940’s drawings together with design capacity of the piles 4.0 PERMANENT PROPOSED WORKS The proposed development requires the vertical extension of the existing building by 2 floors and plantroom, replacement of the existing cladding and refurbishment and modifications to the internal layouts. 231043-ECE-ZZ-XX-RP-0001 info@eireng.com 231043-ECE-ZZ-XX-RP-0001 3.0 EXISTING BUILDING i.
6.0 RECOMMENDATIONS Based on the above information our recommendations would be as follows:
The recommended proposal for the new crane supporting structure would include the construction of a new steel frame within the existing building. At each level new horizontal steel beams, positioned above the existing concrete slab, to frame and stabilise new steel columns. This would require the removal of a portion of the existing concrete slabs at the position of the new steel columns. Diagonal bracing would be added each level (except for the first level, ground to first fool) to maintain the stability of the new steel frame. New steel beam would be fixed back to the existing concrete core to provide further stability, this would only occur at the 4 th level and 1 st floor level. The new member sizes are to be in the magnitude of a 254 UC for the columns, 203UC for beams and diagonal beams 200RSA angles for the elevation bracing.
231043 | Google Treasury Building Temporary Works
PROPOSED TOWER CRANE DESIGN
info@eireng.com
PROPOSED TOWER CRANE DESIGN
Page 2
Made with FlippingBook Digital Proposal Creator