The combined strength of RMD Kwikform's Alshor Plus and Rapidshor equipment has been used to create record-breaking shoring towers to support the construction of the new $64m landmark Sultan Qaboos Mosque in Nizwa.

The mosque is being built by Carillion Alawi.
 
The towers have been erected in some parts of the structure up to 43 m tall, to support the casting of the dome, concrete slabs and beams, making up the main areas in the new Sultan Qaboos Mosque, funded by the Oman government.

The vast scale of the project required RMD Kwikform to deliver over 1,200 tonnes of equipment to the Carillion Alawi site, which is 150km south west of Muscat.

Faced with a change in programme sequencing, which required both beams and slabs to be cast at the same time, engineers from RMD Kwikform designed an innovative solution to erect a run of Rapidshor shoring support inside the previously erected Alshor Plus birdcage, specified for the initial works. By combining the strengths of Alshor Plus and Rapidshor, Carillion Alawi was able to cope with the increased loading of the slab and beams construction sequencing, optimising the construction cycle for the project.

Commenting on the challenges, Carillion Alawi project manager Mohamed Tariq said: “With the top of the dome needing shoring support at a total height of 43 m and numerous concrete slabs at different levels making up the new mosque, the key challenge was how to manage the safe erection of the shoring.

“Critically we also had to be conscious of the distribution of loads throughout the project, to keep within the allowable working load of the RMD Kwikform equipment.  

“Having worked with RMD Kwikform on numerous other projects in Oman, including the Wave retail centre in Muscat, where we also used Alshor Plus, we were familiar with the high leg load capabilities of the product.  So for the initial sequencing for the project we opted for this solution, with RMD Kwikform site staff supporting us with the system design and erection training.

“When we decided to change the sequencing as part of a fast-track programme, we looked to RMD Kwikform to help us design a revised solution that did not involve us dismantling the already majority erected Alshor Plus towers. Working with us, they analysed the additional pressures and came up with a solution to construct Rapidshor towers inside the Alshor Plus towers, bracing the two together to create a combined shoring tower structure.”

With both Alshor Plus and Rapidshor being modular systems, the Carillion Alawi site teams were able to quickly erect the tower structures safely, bringing forward the concreting element of the programme to meet the needs of the overall advanced programme time.

As part of the revised design of the structure and construction sequencing, that included additional monolithic slaps, which had to be poured at the same time, RMD Kwikform engineers were faced with the need to install additional equipment without majorly restricting access.

Commenting on revised design and the project RMD Kwikform regional sales manager, Bellphine Campbell said: “With the changes made part way through the project, having calculated all of the loadings, we knew we could not release the loads in the Alshor Plus to strike these additional slabs. We therefore introduced a 900mm wide run of Rapidshor shoring that sat within the Alshor Plus birdcage support to distribute the loads and keep both systems within their loading capacities.

“In doing so, we also recognised the need to increase the size of the working platform, so we designed additional bays using Alshor Plus. To reach the 42 metre top height of the dome structure, we literally put shoring, on top of shoring, on top of shoring.

“Put simply the first Alshor Plus birdcage tower arrangement was 12.5 metres and 15.8 metres tall. To save time and money on dismantling the Alshor Plus at this lower level, the next set of shoring combined Alshor Plus with Rapidshor, reaching from 18 metres to 30 metres to cast the beams and slabs at this height. This combination was required as the consulting engineers advised that additional concreting up to 46 metres high would need to be cast without further striking of loads.

“With different segments of the structure requiring different shoring setups, like the two level slabs next to the prayer hall, the shoring puzzle required a great deal of engineering and site support. But it was the dome that was the ultimate challenge. Rapidshor shoring, reaching a height of 17m to the top of the dome was arranged at varying heights and adjusted using the systems jacks to support the curved structure of the dome.  The Rapidshor shoring was founded on top of an Alshor Plus birdcage, a staggering 25 metres high, erected from the main 5.5 metre slab. In total this created a record-breaking tower for RMD Kwikform, some 42 metres tall.”  

To enable the project to stay on-track, even with the changes to the construction programme, RMD Kwikform managed to source additional equipment and deliver the new design solution without impacting on the programme time.  

Due to be completed in 2015, the new Sultan Qaboos Mosque will be one of the largest in Oman. - TradeArabia News Service