Conco was selected to perform a dome roof metal deck fill with shotcrete. The project required a unique application of approximately 6,000 cubic yards of shotcrete that had to be pumped over 300 feet. While Conco does not currently operate in Nevada, Conco was the only contractor that was able to provide solutions with a job-specific plan including pumping, shotcrete/place, and finish sequence, and access-egress to perform the scope of work.
MSG Sphere is the first of its kind. The building consists of a sphere-shaped amphitheater that will feature nearly 20,000 seats. The interior of the building will be completely wrapped with over 13,500 high-resolution LED screens. As the building itself, Conco provided a unique dome roof fill with shotcrete application. Conco coordinated manpower from all the regions to work together and complete such a complex project.
The first challenge that Conco had to face, was to provide a complete pumping plan to push over 6,000 cubic yards over 300 ft vertically plus another 100 feet horizontally at each pump system location. The plan included engineering, calculations of maximum pressure of the system, and the rate of yardage per hour required to meet the project expectations. A total of (3) complex pump systems were installed, utilizing high-pressure pumps at ground level that fed trailer pumps installed on the roof through hard pipes. Finally, a combination of pipes and rubber hoses were used from the upper pumps to place the whole dome.
The second challenge was to tailor and create shotcrete and cast-in-place mix design that can meet a specified 0.02% shrinkage requirement on the whole dome. Conco worked hand in hand with a local Ready-Mix Supplier (Silverstar Ready Mix) performing multiple trial batches, adjusting aggregates sources and multiple admixtures dosages until it was achieved.
The structural engineer required the dome to be placed in dome shape form starting from the crown of the dome. Every day the placement had to be completed around the whole circumference of the dome for the structure be able settled evenly with the added weight of the concrete. Conco planned a construction joint sequence with the following parameters:
▪ Being able to place a total circumference on a daily basis to meet the engineer’s requirement.
▪ Achieve an optimum rate of yardage per hour on daily basis with three crews running simultaneously at every pump location.
▪ Coordination with ready mix supplier on the concrete delivery rate.
▪ Complete the fill of the whole dome in 23 days or less as required on the project schedule.
▪ Conco had to fully coordinate every single step of the work with other trades to avoid project delays.
▪ Planned a scaffold system that was easy enough to be able to be moved on a daily basis but strong enough to support crews on a safely manner.
▪ Provided easy access-egress on areas of the dome that were up to 50-degree incline.
Location: Las Vegas, NV
Project Size: 6,000 cubic yards
AECOM-Madison Square Garden Company
Severud Associates Consulting Engineers