Award winning Brazilian blast

By Lindsay Gale13 April 2012

On December19, 2010, Fábio Bruno Construções Ltda. imploded the south wing of the Rio de Janeiro University Hospital. Built in Rio in 1950, it was considered to be the first reinforced concrete building in the city. It consisted of 16 floors with an area of 11,266 square metres (121,266 square feet) and a total of 55.000 square metres (1,942,306 square feet) of concrete. After construction was completed, the University planned to use only half of the building and left the other half unoccupied due to financial constraints. With time, the unused half suffered serious deterioration and it was therefore decided it should be demolished for the safety of the patients and people working in the occupied north wing of the hospital and to replace it with a new building.

In order to safely demolish half of the hospital only and protect the North wing, the structure had to be divided into two completely separate components by the demolition of a section between the two wings.

A space of 15 m (50 ft) was opened between the two wings of the hospital to mitigate the effects of vibration during the implosion. To ensure the safety of the remaining section of the structure and other surrounding buildings, Fábio Bruno Construções tasked Applied Science International (ASI) with analysing the demolition plan. With the Extreme Loading Technology (ELT), Fábio Bruno could model and analyse the behavior of the structure during the proposed demolition. Every structural detail, including columns, beams, slabs, masonry walls, expansion joints and reinforcement details were modeled in 3D. The model also included weakened material models in corroded areas of the structure to ensure that it reflected real-world conditions. With this analysis the demolition team was able to avoid the dangerous situations that can arise during controlled collapsed demolition, such as the structure falling in the wrong direction or 'squatting' where the structure does not completely collapse.

In addition, because of the sensitivity of the adjacent buildings and hospital equipment, Fábio Bruno was obliged to analyse the vibration effects of the debris on the soil due to ground impact. High velocity impact of a large mass on varying soil composition can be hazardous to surrounding infrastructure both above and below ground. All ground acceleration levels due to the impacting debris were found to be within acceptable limits.

It took 80 days to carry out the manual demolition of the 15 m section and a further 60 days to make 2,960 holes in the pillars, to break most of the brick walls and to place protective netting around the building.

After three days spent placing the explosives, a 200 m (656 ft) exclusion zone was created for the implosion with the participation of 15 separate stakeholders. Discussions concerning the operational map began on November 17 and after six different meetings the operational map for the implosion was ready.

Prior to the implosion the team discovered some puppies that had just been born in the building and were able to save them by placing them in a box at a safe distance after looking for their mother for over an hour. The good news is that she was hidden somewhere close to the building and got back to meet her puppies after the implosion.

A survey of the surroundings with pictures of the remaining hospital and other structures, done previously, and three seismograph points, which showed in the closest spot at 40 m (132 ft) from the implosion a particle vibration velocity of 2.86 mm/sec and a linear acoustic pressure of 129 dB (L), ensured the success of the enterprise.

Ten water trucks were strategically positioned to minimise the dust generated by the implosion, particularly on the main road close to the building.

The implosion went exactly the way as planned and the client was very pleased with the accuracy. A total of 90,000 cubic metres (3,178,320 cubic feet) of waste resulted from the implosion, with 99% being recycled.

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