Part I - A Summary of the Facts

On hearing the initial appeal over the public address system, a vice-president for the Tenant’s Parent Division headed for the produce area to find out what was happening. “I noticed the beam was rotating, and there was a leak in the pipe in the ceiling at the location. I knew exactly what was going on. I knew we had a cave-in problem,” he said.

Everyone was then told over the P-A to leave the store immediately.

Trevor Burkitt, an amateur photographer and photo-technician at another of the Tenant’s stores, was drawn to the area by the running water and started taking pictures when he saw “that there was something terribly wrong.” He was right underneath the beam and zoomed in for a close-up: “It was then that it started to appear to me that there was a major problem, and that I was really in the wrong place.” Burkitt heard a crack “and I turned around and aimed my camera at the roof, and then there was a tremendous roar as the roof sagged and just fell right in. ”

Estelle Birch and a girlfriend watched the ceiling “come down very slowly, and (we) got out of there fast. They gave us a choice to go out the left or the right, and my girlfriend and I chose the right which was a good thing because everything was flying at the other end. And that’s when that air hit everybody, just like a tornado going through. ”

Elsie Barber said the gust knocked her down “and then all I knew, people picked me up, then I looked, my feet were wet, but my shoes were off my feet.

The blast of air and the water on the floor caused Molly Jensen to fall on the floor where she broke her elbow.

“The gush of air that came out of the building . . . with a nutmeg smell . . . blew us out,” said Bud Smallwood. He was helping pick up an elderly lady “when another woman fell over the top of both of us. I could see that there was going to be a pile-up in front of the door, so I stayed thereto help the people, drag them out.”

The exodus was orderly and everybody was well behaved. Testimony showed that the quick and courageous action on the part of the employees and the mayor saved many customers from injury caused directly by the collapsing roof. Utility clerk Larry Nichols, who was in the danger zone cleaning up, did not get out in time, and his hips were pinned under bent steel and broken concrete. Firemen and emergency health services personnel used two pallet jacks to remove him from under the rubble. He suffered a crushed pelvis.

At about 9:15 AM, approximately 6,400 square feet of the roof structure fell into the produce area. Twenty cars parked on the roof fell into the opening and 21 people were injured.

There were no fatalities.

The seniors who lost their cars in the collapse were upset at having to accept considerably less than they feel their vehicles were worth. “We had no way to protect ourselves, and I think they should look after us,” said Annabel McDaniel who did not have comprehensive insurance. “I went in with a car I don’t see why I can’t come out of there with a car."

THE COLLAPSE HISTORY

Architect, as the architect and project coordinator, solicited proposals for the mechanical, electrical and structural engineering, and selection of the consultants was made by the owners. Eight bids were received on the structural engineering work and a firm (Engineers), the third lowest bidder was chosen. Their bid was in the amount of $20,500 for the $5.4 million Tenant’s building. This fee was subsequently negotiated down to $17,000 by the Developer’s development manager.

The Developer pre-qualified the contractors as to ability to build a project of this size and financial ability, and chose a firm (Constructors) which was the lowest of six bidders. Constructors in turn hired the sub-contractors including a firm (Erectors) to provide and erect the steel. Erectors hired another firm (Fabricators) to design and supply the open web steel joists and a designer (Detailer) to detail the connections.

Original plans for the Tenant’s building did not include parking on the roof, and in December, 1986, one of the contractors bidding for the contract suggested the rooftop parkade during prequalifications. Both Architects and Engineers reviewed the proposal and reported that it was feasible. Discussions were held with the Tenant and the idea was adopted. A travelator was to take people from the floor of the store to the roof.

All plans, drawings and specifications were finally signed off by the Tenant on July 16, 1987.

The Engineer provided the Municipality of Burnaby with a letter indicating that the building construction would be supervised by a structural engineer. Building permits were issued for a fee of $30,235, and construction started July 17, 1987.

The sidewalk on the parking deck was originally five feet six inches wide as shown on architectural drawing A5. 5. On July 6, 1987, revision six was issued extending the sidewalk three feet on each side for a total width of 11 feet six inches. Drawing S5.5 provides an edge detail of the sidewalk showing the sidewalk six inches above the finished roof-parking surface with an edge thickness of 10 inches and a center core of six inches of Styrofoam insulation. Constructors proceeded with the rooftop construction and poured the three feet extensions on each side of the sidewalk in solid concrete.

The designer, an engineer-in-training at the Engineer, said the edge detail on drawing S5.5 should have prevailed, and the additional weight would have been minimal. Engineer would not have agreed with the addition of six feet of concrete six inches deep had they been consulted on that point. The additional weight of the sidewalk supported by the beam became 24,500 pounds, a significant increase in weight and a contributing factor to the eventual collapse.

The extra weight, although in place, was ignored by another firm of consulting engineers (Consultants) that did a subsequent structural review.

Meanwhile, Fabricators started design of the open web steel joists and in September and October was requested by Engineers to add bottom chord extensions to 29 locations. There was a note on one of the structural drawings requesting that bottom chord extensions also be placed where applicable.

Fabricators informed the consultants that the extensions would involve extra costs, and the consulting engineers decided that these would not be required to provide stability for the columns.

“The omission of the extension at the critical column location had a very significant effect,” said the consulting engineer in charge of the remedial work in the store. “It’s my belief that had the extension been in place, the beam would have been still very severely over stressed, but it would probably not have collapsed on that day. We may very well have been shopping in that store today unaware of the level of distress in the roof structure above us.”

There were no problems until November, 1987, when a beam in the area of the travelator deflected about two inches, tilting the housing. The owners asked Engineers to review the problem and remedial work was recommended and done. Several beams were strengthened, some columns were added; a new reinforced concrete beam constructed; and some details modified.

Station Square decided to get an independent opinion of the structure and hired Consultants to review this area and to look at the building and the design drawings for problems. In a Dec. 24, 1987 letter, Consultants submitted a report identifying the beams that they found to have “insufficient capacities,” discussed the remedial action carried out, or proposed, by Engineers; and agreed with it. Letters from both fims confirmed that the remedial work had been done.

In March, the Tenant became concerned about deflections of certain roof beams and hired the Consultants to conduct a design review of the entire building. “We didn’t set a time limit on it, nor did we set a dollar value on what we were prepared to pay,” said the vice president of the Parent Division. “The main thing was to get a good second opinion on the safety of the building.”

In a report dated March 30, 1987. Consultants reported that two beams had “insufficient capacities.” One was the W24X76 that later collapsed. The report recommended remedial measures, and Developers, the architects and both engineering firms initiated steps to effect this remedy. The following day, the owners were advised that the remedial work would not be required because a mill certificate provided by Erectors to Engineers indicated a yield strength of 55,700 per square inch (psi). The design was 44,000 psi. “On the basis of this information; we conclude that the beams in question are at least 26 per cent stronger than the specified strengths and are satisfactory to resist the desire loadings imposed,” said a member of Consultants in April 7 letter to the Parent Division. “This new information is a blessing for all concerned.”

Construction was completed on March 18. Engineers informed the Municipality on April 14 that the building had been built according to its drawings and specifications and to the National Building Code of Canada. A temporary occupancy certificate was issued by the Municipality on April 22.

On April 23, shortly after the official opening, the beam and an area of approximately 6,400 square feet collapsed.

COLLAPSE MODE

The W24x76 beam supporting this portion of the roof failed over the column at grid lines S513.13 and W110.84 on the architect’s drawing.

The investigation determined that the beam failure probably involved at least two modes, beam bending with buckling of the lower flange and buckling of the beam-column assembly as a result.

For reasons not fully known, the beam was changed from W24X104 to a w24x76 - a beam too small even if laterally supported. When doubt was raised, a series of recalculations was made.

There are nine factors involving the design engineer --- assumptions, decisions, judgement of miscalculations --- each of which reduced the safety margin:

• A design change from a two-inch to a three-inch top slab wearing surface increased the dead load from 80 psf to 90 to 95 psf. The open web steel joists were designed for this heavier load but the beam design was not changed.
• As built, slab thicknesses were greater than design, increasing the dead weight load to about 100 psf. There was no provision for this additional concrete.
• No allowance was made for the weight of the walkway, either as designed or as built (concrete where styrofoam was specified).
• The beam, originally sized at W24x104 based on deflection criteria, was incorrectly reduced to a W24x76 as a result of a change in the deflection from l/240th of span to 1/360th of span length stemming from a discussion about economy.
• The live load was incorrectly assumed to be 43.7 psf due to incorrect identification of loaded area and failure to note a constraint on an unbraced live load.
• In calculating the bending moment at the column centerline, a fourth calculation reduced the moment to that at the face of the column cap plate (where it is appreciably less than at the centerline), proceeding with design of a strengthening bracket . . . to make up the small deficiency introduced.
• The assumption made by the engineers --- that the “guaranteed” minimum yield strength of a beam can be upgraded to the value given by one value or the lowest of several given by mill tests --- is unsupported for two reasons: sample location on the beam and variations in chemical composition.
• The structural engineer did not study the reduced capacity of the W24X76 caused by lack of lateral support which were originally specified for some columns (not the one that collapsed) and later cancelled due to extra cost.
• The requirement for lateral support was not studied in part due to conflicting assumptions about responsibility by the structural engineer and the detailer and without knowledge of as built thicknesses and weights of the extra walkway.

Any one of these alone would not have resulted in collapse, being partially compensated for by factors of safety. However, taken together, failure was inevitable.

The underdesign was due to miscalculations in the office of the structural engineer. It was compounded by a similar miscalculations by the structural engineer who was called in to review the structure after deflections were noticed in some beams supporting the travelator in the store.

The investigation of the cause of this incident concludes that, “The need for greater care by all parties in communicating special and unusual requirements to suppliers and designers is of vital importance on all building projects.”

INQUIRY RECOMMENDATIONS

While the underdesign was due to a miscalculation made in the structural engineer’s office, this was not the only error made on the project. Facts presented in evidence showed that there was a definite lapse of communication and instruction between the parties involved in the building process.

Throughout the hearings, and in many submissions, the responsibility and obligations of the owner received considerable attention. From this it was concluded that owners must establish clear lines of communication and responsibility for all those involved in their projects.

The role of the municipality who issued the building permit was strictly administrative, and there was no suggestion that it was deficient in discharging its duties. Contrary to public perception, building inspectors do only a cursory inspection of large buildings. However, municipal departments are the last check points before a building is built and any necessary additional checks must be introduced into the process at either the design stage, by architects and engineers, or at the stage of the permit application to the municipality.

The response of emergency teams, fire, police, ambulance, was prompt and efficient.

Clearly, the matter of public safety is a paramount consideration by all those involved in building projects, especially those intended for public use. With this in mind, the Inquiry Commissioner made a number of important recommendations as follows:

• Provision must be made for the audit of structural engineering drawings and calculations for major buildings selectively chosen by municipalities for review by independent engineers, with the cost borne by a special levy on municipal permits.
• Structural engineers should be required to pass a special examination before becoming professionally qualified and should be required to carry specified limits of professional liability insurance.
• A provincial manual of recommended construction practices and procedures should be developed to clarify responsibilities of owners, architects, engineers, contractors and suppliers in construction projects.
• Standard documents (Letters of Assurance) under the building code should be used throughout the province for major buildings, to assign responsibilities among owners, architects and engineers.
• Architects and engineers should be primarily responsible for ensuring compliance with the building code for major buildings, with building inspectors playing a secondary, administrative role.
• In addition to the registration of individual engineers, engineering firms should also be registered with the professional association, to strengthen standards within the engineering profession.
• Provincial standards of practice should be established for major building design, drawings and calculations.
• Steel industry construction manuals should be revised to provide more accurate assistance to engineers.
• The Minister responsible for municipal construction should appoint a three-member task force to oversee implementation of these recommendations.