BUREAUCRACY, POOR maintenance and inadequate fire precautions are all thought to have contributed to the deaths of four people in Moscow's 540m high Ostankino television tower last week, when a small electrical fire developed into a 26 hour inferno.
Firemen arrived at the scene just 10 minutes after the fire broke out high up the 33 year old structure at 3pm on 27 August.
But they had to wait three hours before Russian president Vladimir Putin could be informed and give permission to turn off the tower's power supply - even though safety regulations call for immediate shut-off.
The delay proved fatal. Even though the fire started in a service level some 375m above ground, poor quality cable insulation, lack of fire stops and the failure of automatic fire systems quickly allowed it to spread downwards. On the way it engulfed the rotating restaurant and observation decks 337m above ground. It reached the 117m level before it was finally extinguished.
'If we had cut the power earlier, we would have probably been able to localise the fire, ' said fire chief Leonid Kortchik.
Instead, firemen were forced to try to contain the fire and evacuate visitors while the power remained on.
Armed only with carbon dioxide hand held extinguishers, the firemen raced up 300m flights of narrow stairs to reach the fire - running into plumes of toxic smoke as they threw off their oxygen supplies in the process to lighten their load.
The length of stairs and lack of a fireman's service lift encouraged one fireman to breach safety regulations as he attempted to use one of the high speed passenger lifts in a bid to reach the fire more quickly.
Together with a female lift operator and two other unidentified men, senior fireman Vladimir Arsyukov died when the lift's automatic safety devices halted it at the 300m level. It seems intense heat from the burning restaurant may have softened and weakened the lift cables, causing them to fail. The lift eventually plummeted into the basement (see box).
Firemen placed two makeshift asbestos fire stops at 117m and 63m, and aimed high pressure gas extinguishers at the flames.
Eventually, the fire was put out on 5.40pm on 28 August, the day after it started.
Thousands of Muscovites gathered at the site on Sunday and Monday evenings to watch the blaze. They were not allowed within 700m of the tower, amid fears that the 150m steel spire would topple.
Initial Russian media reports said that the Ostankino spire was listing 19degrees. But local surveyors who monitored it in shifts from the early hours of Monday morning estimated the deviation was less than 1degrees from the vertical.
The extent of structural damage to the post-tensioned concrete main tower is as yet unknown, but senior engineer Tom Lennon of building research body BRE said: 'If the heat was enough to destroy lifts, then it was certainly enough to cause severe localised damage to the concrete structure.'
Spokesmen from Russia's State Construction Committee, Gosstroi, indicated on Monday evening that the tower 'can and must be repaired'. This is despite reports that between a quarter and half of the 149 exposed prestressing cables that run along the inside of the circular section tower have been damaged.
Russian civil engineers are certain that these are only present to protect against wind loading, however.
'For the tower to fall, even with all the pre-stress cables loosened, the wind would have to be 100m/s, ' one Moscow University structural engineering professor was reported as saying.
Gosstroi told NCE that results from laboratory tests that would confirm the extent of structural damage would be available next week.
Last Thursday, Putin told the Russian media that full restoration of the tower would be completed in between four to six weeks.
More on the Ostankino tower can be found at www.tvtower.ru www.great-towers.com
How the lifts were affected
According to Russian media reports the high speed lift holding the four victims of the blaze initially became jammed when its safety locks came on, indicating that the lift cables had already melted through or snapped.
However, as the blaze spread further downwards, the lift suddenly plummeted into the basement, followed by its counterweight.
Roger Howkins, Ove Arup & Partners associate, said a possible cause of the fall was that the lift roller guide tyres that follow the shaft guide rails - a feature of all high speed lifts - may have melted in the heat coming from fire below.
'This would allow the lift to move around inside the guide rail and eventually break free of the safety locks, ' he said.
Alternatively he suggested that the guide rails themselves may have buckled or distorted in the heat.
Before the lift fell, however, it is likely that the victims would have been overcome either by heat or toxic fumes from burning insulation.
How the fire spread
An electrical fault is thought to have started the blaze at Ostankino Tower, breaking out in the service area at 375m - above the rotating Sedmoyo Nebo, or Seventh Heaven, restaurant - as a result of 'huge overloading' on the 1967 year old structure's cabling.
Roger Johns, electrical engineer at Ove Arup's Moscow office, believes that cables in the tower could have become overloaded as a result of the progressive addition of telecommunications equipment over the years.
'This overload should have tripped the fuse breaker and led to a power shutdown, but either the breaker wasn't correctly sized, or wasn't working, ' he said.
Johns believes the power overload would have created a heat source, leading to the cables' PVC insulation catching light.
He said the fire could also have been caused by poor maintenance of the cable insulation, allowing a short circuit to take place - when current passes between exposed neutral and live wires.
He continued: 'Once the fire had started, pieces of burning insulation may have fallen down the tower and stuck to further cables, creating more fires.'
Strong air currents provided by the chimney effect of the tower would also have fed the flames.
However, fire experts believe the fire really took hold when it reached the restaurant, where the flammable interior would have helped feed the fire - possibly creating enough heat to affect the lift systems.