B of the Bang Manchester
Dismantling Iconic SculptureConnell Brothers were appointed as contractors to dismantle the sculpture known as the B of the Bang on behalf of Manchester City Council.
The sculpture was located on the junction of Alan Turing way and Ashton New Road at the entrance of the walkway to the City of Manchester Stadium.
This is a very busy junction with over 55,000 vehicle movements per day; traffic management was required during the removal of a number of spikes which over sailed the footpath and road. It stood some 55 meters high at the tip of the highest spike and comprised of 175 hollow steel spikes connected to a central core. This core was 22 metres above ground level and was canted forward on the five supporting legs. The entire structure weighed 168 tonnes and was welded to base plates that were securely fixed to concrete piles and a reinforced concrete slab.
Prior to the sculpture being opened to the public a number of the spikes had failed and had fallen to the ground. This resulted in the entire sculpture being declared unsafe and fenced off from the general public. Several spikes were removed at this time for testing. It was later decided that the sculpture was to be dismantled in its entirety.
Several sections of steel fencing and a number of large gates were removed, together with concrete benches, in order to gain access to the sculpture.
Prior to any dismantling works being carried out an exhaustive study of the fabrication and construction drawings was undertaken to determine the best technique for carrying out the works.
The first stage of the project was to remove the spikes back to the initial connection point to the main core. As the intention was to retain the core for future use. Dismantling of the spikes had to be carefully controlled in order to maintain the balance of the sculpture as a whole and a specific removal sequence was determined to achieve this objective.
The spikes consisted of several sections up to 7.5 m long butt welded together. Some of these welds showed fatigue and therefore each section of each spike had to be removed individually. This was carried out by forming a hole at one end of the spike to pass a chain through and supporting the other end by wrapping a strap around the spike. The section was then cut just beyond the welded joint and the spike lowered to ground level. Access to carry out this work was provided by a combination of mobile elevated work platform and a man riding basket attached to a second crane.
This method was adopted in order to remove the spike at the same angle it was installed at. The process was repeated until all the spikes were removed. The tip of each spike was removed to a length of approximately 1 m and these were placed in a secure skip for destruction off site. The remaining sections of the spikes were cut into smaller pieces by a combination of operatives using oxy/propane cutting equipment and an excavator equipped with a shear, the resultant sections being salvaged as scrap.
Following the removal of the last spike the core structure was inspected closely again. It was found that the lateral welds along the tubes forming the core were exhibiting cracks. After further consultation it was decided that the structural integrity of the core could not be guaranteed and therefore the safest option would be to dismantle the core in sections.
The second stage of the demolition therefore comprised removing the core piece by piece until only the final connection to the legs remained.
Once this had been achieved the next phase was to remove the core and legs. Each leg consisted of a solid steel base section up to 5 metres long. This was welded to a 40 mm thick tube, up to 600 mm in diameter, forming the main legs which were then welded together at the core.
The position of the legs allowed for one front leg and one rear leg to be removed, with the remaining three legs forming a tripod type arrangement to support the core.
Prior to removing any of the legs a crane was brought to site and a chain passed through a hole formed in the core. This was to enable the core to be fully supported during the dismantling works. Once supported a hole was formed at the top of the leg and a chain passed through to enable a second crane to lower the leg to ground level. The leg was then cut through at the base and rotated down to ground level before being removed.
After the removal of two of the legs the final rear leg was cut through. The weight of the core was then shared between the remaining front legs and the crane. After the rear leg was removed the front two legs were each cut through 2/3 of the way up and the core, weighing 19 tonnes, was lifted free and placed on the floor for further processing and removal. The remaining 2/3 of the last two legs were then removed, leaving just the last small section of each solid leg piece protruding out of the ground.
Following the removal of the final leg section the sculpture was reduced in size by operatives using oxy/propane cutting equipment and removed from the site. The area around each of the remaining legs was excavated to reveal the concrete surround to the steel fixing point on the concrete slab. This surround was then broken away and the leg cut back flush with the slab before the entire area was backfilled and reinstated to its former condition.