Construction World January 2020

COVER STORY

J et Demolition Director Joe Brinkmann highlights the close working relationship that the demolition specialist established with various stakeholders throughout the course of WKH SURMHFW 7KH FR RSHUDWLRQ DQG GHGLFDWLRQ WR WKH SURMHFW E\ DOO stakeholders, including its main client the Gauteng Department of Infrastructure Development (GDID), various local and provincial departments, project managers, subcontractors, specialists, and the local public, all contributed to the successful implosion RI WKH ͤUH GDPDJHG VWUXFWXUH 6DIH PDNLQJ PRQLWRULQJ DQG FOHDQLQJ RI WKH VWUXFWXUH KDG DOUHDG\ FRPPHQFHG LQ 'HFHPEHU 7KH ͤQDO IRXU PRQWKV preceding the implosion included valued contributions and detailed SODQQLQJ E\ HPHUJHQF\ VHUYLFHV ORFDO WUDͦF DQG ODZ HQIRUFHPHQW all to ensure the safety of the general public during the implosion. Brinkmann also pays tribute to the surrounding residents and businesses – including student accommodation, and landmarks VXFK DV 7KH 6WDU QHZVSDSHU KHDG RͦFH DQG /XWKXOL +RXVH ̰ IRU EHLQJ IXOO\ FR RSHUDWLYH DQG VXSSRUWLYH RI WKH SURMHFW IURP the outset. “During the entire project, we were also highly conscious and UHVSHFWIXO RI WKH IDFW WKDW WKUHH ͤUHͤJKWHUV ORVW WKHLU OLYHV ZKHQ D ͤUH broke out in the building in September 2018,” Jet Demolition Director Liz Brinkmann adds. Jet Demolition was awarded the contract after a competitive tender process, and presented the GDID with two options: Controlled LPSORVLRQ RI WKH HQWLUH VWUXFWXUH RU D WRS GRZQ PHFKDQLFDO demolition process. Given the sensitivities surrounding the site itself, and concerns about the extent of damage to the structure, GDID elected the implosion approach. 7KH ̨UVW VWHS 7KH ͤUVW VWHS ZDV WR UH VXSSRUW WKH ͤUH GDPDJHG VWHHO UHLQIRUFHG

concrete building by installing engineered propping where required. $Q DGYDQFH ZDUQLQJ PRQLWRULQJ V\VWHP ZDV DOVR LQVWDOOHG WR ZDUQ RI any creepage that could indicate an imminent collapse. 7KHUHDIWHU DOO WKH IXUQLWXUH FRQWHQWV DQG ͤ[LQJV IRU WKH WKUHH government departments that had occupied the building, as well as WKH SHUVRQDO SURSHUW\ RI WKH HPSOR\HHV KDG WR EH UHPRYHG IRU RII VLWH VWRUDJH IRU ZKLFK D PDQ DQG PDWHULDOV KRLVW ZDV LQVWDOOHG Jet Demolition carried out a geotechnical investigation, design, and installation of lateral support to the basement retaining walls to ensure their stability during, and after, the demolition of the building. This was an important consideration for the future redevelopment of the site, especially given the premium placed on underground parking in the city centre. Challenges The fact that there were no structural drawings available for the building meant that Jet Demolition had to physically GHWHUPLQH WKH PDNH XS RI WKH VWUXFWXUH LQ DGGLWLRQ WR GHWHUPLQLQJ the exact location of services such as electricity, water, and ͤEUH RSWLF FDEOLQJ ,W ZDV LPSRUWDQW WR SURWHFW WKHVH VHUYLFHV adequately during the implosion event, to avoid any disruption to the rest of the city. All of the major utility companies were on standby to assist with any contingencies. A major challenge was posed by the fact that the main building columns tapered quite dramatically from the bottom to the top, which required a detailed assessment of the column size and rebar strength at all points. The columns were at their widest in the basement, where they measured 1,5 m by 1,8 m. Not only did breaking up these massive columns pose a major challenge, but all of the debris had to be contained to prevent damage or injury. The closest building was only 7,8 m away. “The height relative to the closest structure, and the very tight constraints of the surroundings,

A central column being charged.

Electronic detonator controllers.

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CONSTRUCTION WORLD JANUARY 2020