Tuesday, June 18, 2013
What kind of force shears open a road and drives a car some six metres into the ground? According to an engineering expert, the force that hit the Honda City driven by Lim Chin Aik was equal to having seven buses travelling at 130kph hitting him simultaneously.
The full capacity of each stage bus is 60 passengers and the driver.
Thirty-five-year old Singapore-based architect Clifford Tan was calculating the force of the impact on the car driven by rice seller Lim when the 38m lightning arrestor and part of the “wing wall” holding it fell from the rooftop of the 21-storey Menara Umno in Macalister Road. Tan said the debris would “pulverise anything that came into contact with it”.
The debris which spiralled downwards would have generated high velocity when plunging, he said in a telephone interview from Singapore.
It would be difficult to extricate anything which was crushed or pinned down by the sheer force of the falling debris, he added. The fate of the driver is still unknown but he is feared dead.
Tan, who posted his findings on his personal Facebook account, was referring to the freak storm which caused the lightning arrestor and its supporting concrete wing wall to come loose. The falling debris also killed one lorry assistant from India.
Tan estimated that the mass of the collapsed concrete alone was nearly 100 metric tonnes.
With the steel reinforcement, steel antenna structures, aluminium cladding and other ancillary components, the total mass of the fallen structure was probably 110-120 metric tonnes, he said.
The force of the impact, he estimated, was about 1,143,333 N (newtons) or 1,143 kN.
To put that into perspective: if you place a one litre bottle of water on your hand, that exerts a downward force of approximately 10N (9.8N) on your hand. The impact force of the debris was 114,333 times of that.
Alternatively, he said, it was the equivalent of seven fully-loaded RapidPenang buses impacting simultaneously at a person at 133kph.
A typical concrete floor slab of an office building is designed to carry loads of 1.5 to 2.0kN/per sq m, while heavy load areas like loading docks are typically five kN per sq m. Extra-heavy load floor slabs, for example warehouses and factories, are typically rated between 10-20kN/per sq m.
“I estimated that the wing wall fell from an estimated height of 70m and would cause anything it hit to be crushed to bits,” Tan said.
Tan stressed that he was not speculating about the collapse but merely offering an educated observation on why the car was smashed to pieces