The collapse of a parking garage under construction in Tel Aviv's Ramat Hahayal neighborhood on Monday, in which three people were killed, was a rare event in Israel that will be taught in the civil engineering and architecture faculties. The last time a building collapsed because of a planning failure was the 2001 Versailles banquet hall tragedy in Jerusalem, when the building was in use. In this case the building collapsed before it was opened, an incident that old timers in the building industry have a hard time matching in their memory.
The aberrant incident raises tough questions about what lay behind it. Was it a problem of planning, implementation or supervision? Experts we talked to believe it is a combination of several factors.
When you look at the pictures of the collapse, it seems the pillars remained almost in place. The ceilings collapsed on one another; the walls did not support them. Building engineer Rosa Frances, a lecturer at the Technion’s faculty of architecture and town planning, examined the garage’s building permits, which are in the Tel Aviv municipality’s digital archive, and at photographs. “The thickness of the ceiling according to the drawings is 25 centimeters,” she says, calling that dimension “a bit borderline.”
In the past day rumors have arisen that the concrete had been poured just two weeks earlier and had yet to dry, and that piles of building materials were laid on the roof in a concentrated way that sped up the collapse. However, Frances says she does not think this is the main problem. “Because the building collapsed when the load on it was relatively small, I believe it is not connected solely to the thickness of the ceiling,” she says.
Frances raises two other theories. She says that one can barely see in the pictures reinforcing rods. “My fear is that there is an insufficiently strong connection between the pillars and the ceilings. The point that connects between the pillars and the ceiling is one of the places most known for failure,” she says. “In fact, the construction [failure] that took place here is penetration,” meaning the pillars penetrated the ceiling, instead of the entire building collapsing.
“It could be that all the railings were in the plans, but someone was negligent in implementation or that the developer didn’t put in the necessary reinforcement,” she continues. Reinforcement is also needed in the lower half of the ceilings and a wave required along the pillars. Construction industry sources we spoke with said the planner, Hanoch Zahar of Miller, Shenbal, Zahar and Associates, is a veteran, and it would be surprising if he didn’t draw in the reinforcing rods.
A second reason that caused the cave-in, which probably is connected to the first reason, is the foundations from which the pillars arise. Frances identified in the plans that the garage was built on a raft foundation, by which the columns and walls are all attached to one large concrete slab. In contrast, pile foundations connect to each column separately and go down to depths of dozens of meters. “It is likely that the raft sunk into the ground and started a process of sinking that sped up the cave-in,” she said.
Soil consultant and engineer David David adds that clay soil is softer than kurkar, which is common around the city. David was a soil consultant at Assuta Hospital, which was planned nearby using a pile foundation. He raises other theories regarding the cave-in. “It is not one of the stable soils. It is problematic and it could be that there is a raft there,” he suggested. “Then the elasticity of the soil was not calculated correctly. It could be that the main cause of the cave-in was the penetration that the soil added.”
He stressed that in the Versailles disaster there were also a number of factors that led to the collapse. “They thought that it was the Pal-Kal,” he said, referring to the banned construction method used for the wedding hall. “However, it was the weight they added to the floor, and the floor was also not calculated as a floor but rather as a ceiling, so it was planned for other loads.”
Technion expert: 'Problem was systemic'
Prof. Arnon Bentur of the Technion’s civil engineering faculty tends to agree with Frances, saying: “When you plan an engineering system, you plan so that if there is a failure, you will have warning signs, like a car that has warning lights. Therefore, the problem is not in the safety preliminaries,” meaning that when planning for concrete, the plan takes a higher than average load into account, and accounts for rare events like earthquakes. “Instead, there was most likely a combination of factors,” says Bentur. “Therefore, it does not seem to me that the reason was that the concrete hadn’t dried yet.”
He theorizes that there was a systemic failure in the garage, and he does not believe inspectors would have prevented the collapse. “The matter required a systemic change, like the Zeiler Committee described,” he said. “There was a list of recommendations that included the Construction Ministry – one body that looks at every issue of planning and building, so that one system is built, and some of the safety problems are reduced,” he said. “I am not sure that such a system would have prevented the building’s cave-in, which also could have happened in another two months.”
The parking garage’s building architect, Dagan Mushli, and the building engineer who planned the garage’s skeleton, Hanoch Zahar, did not respond to Haaretz’s questions.
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