Whether it was just a badly phrased moment in a press conference or not, Toronto’s Heavy Urban Search and Rescue team has not done itself any public relations favours in the aftermath to the partial collapse of the Algo Centre Mall in Elliot Lake:
The story of the collapsed mall in Elliot Lake, where the rescue mission is back on after being suspended on Monday because officials deemed the building too “unsafe,” has so far deviated from romantic tales of heroism and rescue, spiralling instead into talk of delays, strict mandates and “limited resources.”
A spokesman for Toronto’s Heavy Urban Search and Rescue team, Bill Neadles, said on Tuesday the group was still in its “infancy” — that aside from winning some industry competitions and running mock rescues, HUSAR, as it is known, had only participated in one operation: a gas explosion in 2003. He said when he initially told residents on Monday the team had “reached the end of its mandate” he did not mean they were abandoning the operation, he “just didn’t want to lead anybody to believe I was going to come back with a silver claw and walk on water.”
[. . .]
In Elliot Lake, no one has been spirited away alive, at least not yet. One person is thought dead and a dozen are feared missing. At least one is believed to have made a noise amid the rubble on Monday morning.
“One of the things that gives rescue a sort of romance is the idea that you go in and you get the job done … and that’s one of the reasons this Northern Ontario mall story is so 21st century,” said Bob Thompson, a pop culture expert at New York’s Syracuse University. “Here we’ve got this potentially romantic rescue story, and what do we see? Good ol’ fashioned bureaucracy.”
When most Canadians think of rescue, they do not think of government inner-workings: a Ministry of Labour structural engineer suspending a search; provincial officials having to explicitly give the Toronto team the authority to go back in; a premier intervening to make that happen.
“If you had put 100 miners in there, they would have been out by Saturday,” said Greg Dillavough, a retired miner who once worked in mine rescue in the Northwest Territories and Ontario. “You don’t walk away from a site when someone’s alive.”
Why part of a rooftop parking garage collapsed at the Algo Centre Mall in Elliot Lake ?
Rooftop parking garages are most often born of necessity, dictated by tight sites located in areas where real estate is scarce and expensive. Elliot Lake is in the middle of nowhere. Is land at that much of a premium that they needed a rooftop parking lot? In a nothern country community like that where plenty of land is available why they put a heavy rooftop parking garage on top of the mall is very mind boggling. Why an architect design retail stores and offices with rooftop parking in Elliot Lake where ample surrounding land is available for surface parking?
Construction of the Algo Centre Mall in Elliot Lake located about 160 km west of Sudbury, was approved by the Ontario Municipal Board in 1978, with an estimated cost of $10 million. Construction began in 1979 and completed in 1980. Situated above Ontario Avenue and fronted by parking lots, this 18,580 sq m (200,000 sq ft) two-level enclosed mall is clad mostly in brown prefinished metal siding. The 80 room Algo Inn, the town’s largest hotel and retirement residence, was also built into the mall. In 1981 the mall was anchored by Woolco, Dominion and Shoppers Drug Mart. The Algo Centre Mall and the Algo Inn are terrific amenities and likely contribute greatly to the attraction of shoppers and visitors to the downtown core, but the design is less than sensitive to its urban environment. The entrances are remote and do not address the street. The scale of the building, its introverted nature and the lack of tactile materials, detail, and transparency at the pedestrian level, do little to contribute to the urban environment.
By 1990, the Algo Centre Mall was starting to be plagued with leaks and water damage.
Elliot Lake once was the home of uranium mines. After the closure of the uranium mines including Quirke Mine, Denison Mine, Stanleigh Mine and Panel Mine in Elliot Lake in early ’90s it became a huge retirement centre with homes and apartments for half price.
The current owner Bob Nazarian, 66, of Richmond Hill, Ontario acquired the Algo Centre Mall in August of 2005 for $6.2 million.
In January 1995 Bob Nazarian bought Eastwood Square, a strip plaza in Kitchener, Ontario for just over $3 million. The property was sold in August 1999 for $4.7 million. A newspaper report in 1999 also identified a Bob Nazarian as the owner of a plaza in London, Ontario. He is also listed as an officer of Hillcrest, a real- estate company registered to a suburban office building in Torrance, California that owned a piece of property in a residential neighbourhood in Los Angeles several years ago.
The Elliot Lake Standard newspaper in 2008 reported on “greater than normal” leaks caused damages to multiple units in the mall. Starlight Cafe closed permanently, despite being profitable soon after opening, as customers would occasionally need umbrellas to stand at the take-out counter. Drip-tarps installed by the mall in the kitchen of the restaurant were ineffective. The cafe owner was not made aware of the leaks before starting her lease in 2007. Bank of Nova Scotia had closed for a few weeks in 2008 as a precaution. Bank of Nova Scotia began construction on a new location in July 2011, to replace their mall location. Some businesses suggested that additional leaks started after new owner started repairs to the roof. Tenants noticed a reduced amount of traffic after leaks started, and buckets were scattered throughout the mall.
Some mall business owners were said to not be vocal about their disappointments, unless “water is dripping right on their head or if the water is destroying their business.” The owner of the mall was aware of the leaky roof when purchasing the mall, and suggested there would be renovations to the mall, but would not commit to a date for completing roof repairs or interior upgrades. Ultimately, over $1 million was spent in an attempt to repair the roof.
Leaks in the Algo Centre Mall roof and mould caused Elliot Lake city councillors to consider moving the Elliot Lake Public Library out of the mall, in 2009, where they had been from 1992. Many books were damaged, despite library staff using tarps to cover shelves. At some points, entire sections were blocked for public health reasons.Much of the leaking was said to be corrected, before council considered the issue, and an environmental study was completed. Some library board members and councillors worried that liability insurance wouldn’t cover them in the mall, despite reassurances by library management and the city’s insurance broker. With a multi-use complex in the works, some of the library board was concerned with a 5 year lease that mall management was pursuing, despite the library’s preference for a 2.5 year lease. In the end, the library remained at the mall.
In spite of the issues, the mall used the roof for many events. In 2011 and 2012, it served as the site for the Heart and Stroke Foundation’s Big Bike ride.
The mall owner continued repair and maintenance work in 2012, spending $120,000 into repairs within the 12 month period leading up to June 2012. An engineering and structural study “turned up nothing”, according to the mall manager. Even after the repair, there were photos of serious interior damage to the mall’s roof.
In March 2012, the mall management pleaded guilty in provincial court, after their fire alarms and sprinklers did not meet code. The mall spent $50,000 to upgrade the infrastructure to avoid further fines. The process included adding a new roof to the hotel, gutting the second and third floors, including the hotel lounge.
Along with the Algo Inn, Algoma District Services Administration Board (ADSAB), Algoma Public Health, Algo Room – a community theatre space used by the Elliot Lake Amateur Youth Theatre Ensemble, The Bargain! Shop, Color Your World, Curves (for Women), Dollarama, Elliot Lake Public Library, Offices of the local MP Carol Hughes and MPP Michael Mantha, Foodland – formerly IGA, Investors Group, Marlin Travel, Northern Reflections, Pet Valu, Bank of Nova Scotia, Service Canada, Zellers and Elliot Lake Transit terminal presently occupy the Algo Centre Mall which serves the community of about 11,000 in Elliot Lake.The Algo Centre Mall is a community hub. It is a gathering place – a social centre. Everybody go to the mall at least once a week, some daily. People visiting downtown Elliot Lake, almost always ended up in the Algo Centre Mall.
The coreslab roof supported by steel beams held up on steel-reinforced concrete columns came crashing down through two floors just before 2:30pm on Saturday June 23, 2012. The collapse left a gaping hole about 12 metres (40 ft) by 24 metres (80 ft) and it triggered a natural gas leak. Two cars have fallen through the gaping hole near some escalators.
What may have caused the collapse? Was it caused by stress corrosion cracking, exacerbated by the salts?
Sudden failure of normal coreslab is very rare. Provided regular building and structural inspections are made the condition of the coreslab can be observed and ongoing deterioration noted. The most common cause of coreslab deterioration in Canada is the de-icing road salt. The roof structure is hollow coreslab on steel beams. Joints are the weakest part of all construction. All the joints in the hollow coreslab require sealants – and a double layer of them. Failure was most likely at the bolts, which are more susceptible to stress corrosion cracking, exacerbated by the highly corrosive de-icing salt water. The joints in the hollow coreslab line up over the steel support beams, and highly corrosive salt water constantly dripped onto the steel beams.
Hollow coreslabs are most widely known for providing economical, efficient floor and roof systems. The top surface can be prepared for the installation of a floor covering by feathering the joints with a latex cement, installing non-structural fill concretes ranging from 0.5 inch to 2 inch (12 to 50 mm) thick depending on the material used, or by casting a composite structural concrete topping. The underside can be used as a finished ceiling as installed, by painting, or by applying an acoustical spray.
When properly coordinated for alignment, the voids in a hollow coreslab may be used for electrical or mechanical runs. For example, routing of a lighting circuit through the cores can allow fixtures in an exposed slab ceiling without unsightly surface mounted conduit. Structurally, a hollow coreslab provides the efficiency of a prestressed member for load capacity, span range, and deflection control.
Excellent fire resistance is another attribute of the hollow coreslab. Depending on thickness and strand cover, ratings up to a 4 hour endurance can be achieved.
All structures can experience corrosion problems in harsh environments, and steel-framed coreslab parking structures are no exception. Snow and highly corrosive salt would sit and penetrate the coreslab. Any cracks will allow chloride ingress no matter how good the coreslab quality is, which is the fatal blow for most structures exposed to deicing salts. The coreslab parking deck requires special protection. A parking structure should not corrode or crack because both will cause expensive maintenance problems and may lead to collapse of the parking structure. Slab cracking is always an issue of concern. All corrosion was typically initiated by water and de-icing salts entering cracks in the slabs. In Ontario, the snow and road salt tracked into parking garages by cars can cause considerable damage to coreslab and steel.
Rusting of the steel structures accelerates during the following situations:
• higher soluble chloride ion (salt) concentration
• moisture intrusion
• oxygen
• warm temperature
Chlorides, including sodium chloride, can promote the corrosion of steel if present in sufficiently high concentration. Chloride anions induce both localized corrosion (pitting corrosion) and generalized corrosion of steel.
The use of de-icing salts is probably one of the primary causes of premature failure of steel joints. The use of coated steel and hot dip galvanized steel has mitigated this problem to some extent.
Deterioration of coreslab and steel begins out of sight. Regular building and/or structural inspection will identify the signs of deterioration.
Prior to the commencement of visual inspection of a mall, the building inspector should obtain a set of the building’s structural layout plans from the building owner. The availability of the structural layout plan will help the building inspector to:
(a) understand the structural system and layout of the building;
(b) identify critical areas for inspection;
(c) identify the allowable imposed loads, in order to assess the usage and possibility of overloading; and
(d) verify if unauthorized addition or alteration works that affect the structure of the building have been carried out.
In general, the building inspector is expected to carry out, with reasonable diligence, a visual inspection of:
a) the condition of the structure of the building
– to identify the types of structural defects
– to identify any signs of structural distress and deformation
– to identify any signs of material deterioration
b) the loading on the structure of the building
– to identify any deviation from intended use, misuse and abuse whichcan result in overloading
c) any addition or alteration works affecting the structure of the building
– to identify any addition or alteration works which can result in overloading or adverse effects on the structure.
If there are no signs of any structural deterioration or defects, the visual inspection should suffice and unless the building inspector otherwise advises, no further action needs to be taken.
If, on the other hand, signs of significant structural deterioration or defects are present, the structural engineer should make a professional assessment of the deterioration or defect and recommend appropriate actions to be taken. Such actions may involve repair works or full structural investigation to parts or whole of the building.
Observations of any signs of structural defects, including signs of corrosion, excessive deflection, spalling, cracks, distress, deformation or deterioration,connection failure, instability, settlement, tilt, etc should be properly recorded. This could entail judicious removal of architectural finishes to establish the underlying structural condition. The seriousness of any structural defects should be immediately assessed.
Hollow-core post tension slabs are generally used as structural units for roofs with proper membranes but should not be used in highly corrosive environments such as roof top parking garage in cold climate with high amounts chlorides from de-icing road salts. Reinforced concrete when subjected to over stress conditions due to loadings and corrosion will show distress by cracking and spalling first. Hollow-core post tension panels are less forgiving they are designed using small diameter tendons that have zero tolerance for corrosion, catastrophic shear failure will result.
In 1985, twelve people were killed in Uster, Switzerland when a concrete roof of a swimming pool collapsed only after thirteen years of use. The roof was supported by stainless steel rods in tension, which failed due to stress corrosion cracking.
On April 23, 1987 the L’Ambiance Plaza building, in Bridgeport, Connecticut, collapsed without warning. This collapse spurred a large scale week long rescue attempt but ultimately left twenty eight workers dead and many more injured.
On June 29, 1995,The Sampoong Department Store in Seoul, South Korea, the roof gave way and within half a minute, all of the building’s columns in the south wing gave way, the building’s south wing pancaked into the basement trapping more than fifteen hundred people and killing more than five hundred people. Rescue crews were on the scene within minutes of the disaster, with cranes and other heavy equipment being brought within 24 hours. However, authorities announced that they would call off the rescue, due to the danger that the unstable remains of the Department Store could come down, and many of the rescuers would be at risk. Massive protests, especially from friends and relatives of those still missing, compelled officials to continue looking for survivors, with the remains of the Department Store being steadied by guide cables. After nearly a week, the focus was on removing the debris, though construction crews were careful to check for victims.
Two days after the collapse, some officials said that anybody who was still in the building must have already died; therefore, further efforts would be made only towards “recovery” and not “rescue”. This conflicts with other people’s experience that people can survive much longer. Despite the sweltering heat, those who were not rescued in the first few days were able to avoid dehydration by drinking rainwater. The last to be rescued, 19 year old Park Seung Hyun was pulled from the wreckage 17 days after the collapse with a few scratches.
Due to poor workmanship of quality control during construction, sometimes the ducts containing the prestressing tendons are not fully filled, leaving voids in the grout where the steel is not protected from corrosion. The situation is exacerbated if water and highly corrosive chloride from de-icing salts from the highway are able to penetrate into these voids.
The Ynys-y-Gwas bridge in West Glamorgan, Wales – a segmental post-tensioned structure, particularly vulnerable to defects in the post-tensioning system – collapsed without warning in 1984.
The Melle bridge, constructed in Belgium during the 1950s, collapsed in 1992 due to failure of post-tensioned tie down members following tendon corrosion.
Following discovery of tendon corrosion in several bridges in UK, the Highways Agency issued a moratorium on the construction of new internal grouted post-tensioned bridges and embarked on a 5 year program of inspections on its existing post-tensioned bridge stock.
It was once common for calcium chloride to be used as an admixture to promote rapid set-up of the concrete. It was also mistakenly believed that it would prevent freezing. However, this practice has fallen into disfavour once the deleterious effects of chlorides became known. It should be avoided when ever possible. In 2000, a large number of people were injured when a section of a footbridge at the Charlotte Motor Speedway in Concord, North Carolina gave way and dropped to the ground. In this case, corrosion was exacerbated by calcium chloride that had been used as a concrete admixture, rather than sodium chloride from de-icing salts.
In 2011, the Hammersmith Flyover in London, UK, was subject to an emergency closure after defects in the post-tensioning system were discovered.
The alkali–silica reaction is a reaction which occurs over time in concrete between the highly alkaline cement paste and reactive non-crystalline silica, which is found in many common aggregates. The alkali–silica reaction can cause serious expansion and cracking in concrete, resulting in critical structural problems that can even force the demolition of a particular structure
In the late 70’s, the punching failure of a concrete slab during the construction phase led to the progressive collapse of a large part of a shopping mall in Switzerland. During the winter of 1981, another collapse occurred at an underground parking garage at Bluche, Switzerland, which caused the death of two children. In 2004, a catastrophic collapse occurred in an underground parking garage at Gretzenbach, Switzerland. This collapse resulted in the death of seven firemen, who were extinguishing a fire in the parking garage. Failure likely started from one column and propagated to a large part of the underground parking garage.
Inspection of coreslab, steel structure and reinforced concrete is only effective if the inspection can identify precursors of foreseeable failure modes. Inspection of coreslab, steel structure and reinforced concrete is only effective for foreseeable ductile modes of failure where the coreslab supported by steel structure or its components undergo significant, gradual displacement prior to collapse.
Forensic investigation should include view the construction drawings and specifications for the structure, the construction, and materials testing and inspection records, the as-built drawings and maintenance records. When sifting through the wreckage the forensic investigators should also look for the structural connections in the the debris. Coreslab engineering experts, structural steel engineering experts and reinforced concrete column engineering experts specializing in failure analysis and forensic investigation need to be brought in to thoroughly examine the collapsed coreslab and steel structures to identify the exact cause of the collapse.
Nalliah Thayabharan BSSO
Building Science Specialist of Ontario
Building Experts Canada Ltd
http://www.buildingexperts.ca
Comment by Nalliah Thayabharan — July 2, 2012 @ 08:18