HCA Demolition Of Sandwell College,
West BromwichConnell Brothers were appointed by the HCA to carry out the demolition of Sandwell College, West Bromwich. The site comprised of a number of buildings including a 9 storey tower block, 2 storey teaching blocks and a number of single storey buildings. A number of buildings also contained basements.
Connell Brothers were appointed by the HCA to carry out the demolition of Sandwell College, West Bromwich. The site comprised of a number of buildings including a 9 storey tower block, 2 storey teaching blocks and a number of single storey buildings. A number of buildings also contained basements.
The main tower block was constructed using a steel frame with brick external walls and block and beam flooring. The two storey blocks were of reinforced concrete construction with brick external walls and block and beam floors. The single storey buildings consisted of loadbearing brick walls with pitched roofs comprising profiled metal cladding. There were basement below the buildings in several locations with the basement beneath the tower block extending beyond the footprint of the building. The site itself was located on the busy Sandwell High Street with an access road to the rear serving the garages of adjacent houses and West Bromwich Building Society.
Prior to commencing the works meetings were held with the West Bromwich Building Society to inform them of the proposed works and the timescale involved. The initial works required access to their car park at the rear of the building and this communication and good relationship allowed suitable arrangements to be quickly established. We were also granted permission to establish a webcam on the roof of the Building Society to record the works. The residents were also informed of the proposed works via a letter drop and good site communication allowed for a flexible working arrangement that benefitted all parties.
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Due to the tight confines of the site, initially a temporary all in one welfare unit was brought to site to provide accommodation whilst the first building was demolished. Once this was completed the permanent site facilities were established on the footprint of this building.
Once the front 2 storey buildings were removed the single storey buildings to the rear could be demolished. These buildings had to be carefully brought into the site as their outer walls formed the boundary between the site and the rear access road. The Heras fencing was moved out locally into the access road to allow for demolition, which was halted whenever access was required by the residents therefore minimising any inconvenience.
During this period asbestos removal was carried out to various areas throughout the building by Connell Brothers in house asbestos removal specialists. Also the lifts were removed from the shaft at the rear of the building to form a drop chute for the removal of the soft strip material.
The main building was to be demolished using the floor by floor technique and this required a full scaffold, clad in monaflex, to be erected to the perimeter of the building. The end elevation of the building formed the boundary of the rear access road and this was required to be kept open for its full width to allow fire engines to pass if required. In order to achieve this, the scaffold to this elevation was cantilevered using beams supported off the steel frame of the building, located on the third floor. An added complication was the need to step up the level of the cantilevered beams where they were located within the stairwell in order for them to be based on the stair landings.
In addition to the scaffold requiring cantilevering there was also the need to prop various floors to support the scaffold due to the presence of basements that extended past the footprint of the building. To achieve this, the scaffold was first based out and then carefully measured to ensure the props to the floor below were located under the standards. This was also required to a section of the building at the rear that was only there floors high.
Investigations were carried out within the building to determine its structure in order to develop a propping plan to allow for floor by floor demolition. Sections of floor were removed to accurately measure the thickness of each component, including the steel frame, and determine the sizes of the infill clay pots. Once this information was collected a propping scheme could be developed. Acrow props were installed to various levels following a pre-determined sequence in readiness for demolition. Once fully installed the props were signed off by the Temporary Works Supervisor as available for loading and subject to daily checks.
Once the scaffold and propping was completed Navi mats, mini-excavators and a tracked skid steer loader could be lifted onto the roof by crane to commence the floor by floor demolition. A tracked skid steer loader was used as this reduced the loading on the slab and removed the need for it to be located on Navi mats. The first operation was to remove the large mast from the roof of the building. A man riding basket was used to secure chains to the mast to allow it to be cut free at its base and lowered to the ground safely.
The crane was limited in its location due to basements and other obstruction on the site. Initially a mobile crane with a fly jib set at an angle was utilised. This had the added bonus of being able to reach further across the building than just using the main jib and allowed sections of steelwork to be removed more easily. In addition to using the lift shafts as drop chutes two debris skips were also used to ensure efficient use of all the plant on site. Once demolition had been carried out to the upper floors the mobile crane was replaced by a tracked crawler crane.
Demolition then continued on a floor by floor basis with the scaffold being reduced in line with the demolition works until the building had been demolished to the third floor level. In order to achieve this large GASS props were required to the front of the building as the entrance was 2 floors high and Acrow props could not be used. These props were installed in a frame system for additional strength.
During the floor by floor demolition period Connell Brothers were requested to grant access to the site to enable geotechnical investigations to be carried out for the following construction works. Following on site discussions with the geotechnical engineers the locations of the various boreholes and sampling pits were identified. Plant and material stockpiles were relocated over the Christmas period around the site to ensure they would not interfere with these works.
The investigation works were completed over the Christmas period and enabled the demolition works to recommence after the holiday period and avoid any delays to the overall programme.
Following the completion of the floor by floor demolition the scaffold and internal props were removed to allow for ground based demolition to complete the works. Excavators equipped with pulverisers and shears progressively worked the building down. The ground floor slab was removed and the basements filled with hardcore as demolition progressed to allow excavators to travel onto the footprint of the building. Once the structure was demolished the basement hardcore was removed and the basement backfilled with site won crushed arisings.
During this time the final demolition works to the structures adjacent to the West Bromwich Building Society were being carried out. A protection scaffold was erected to the existing sub-station and fuel tank and the remaining structures carefully demolished. The basement areas were exposed and backfilled with site won crushed materials.
Once all the demolition had been completed the entire site was profiled to match existing levels and new fencing erected to the perimeter of the site
The scaffolding and propping were carried out under controls as required by BS 5975.2008 ‘Code of practice for temporary works procedures and the permissible stress design of falsework’ and detailed within our Integrated Management System, specifically Work Procedure WP16 – Temporary Works. This involved maintaining records of design and design checks/verification responsibilities, Permits to Load and Permits to Strike, inspections, etc. and maintenance of a Temporary Works Register.
This project presented a number of challenges, namely:
• The very tight nature of the site
• Close proximity of the West Bromwich Building Society
• Adjacent access road requiring 24 hour access for residents
• Basements extending beyond the footprint of the building