Highlights from the Herb Gray Parkway girder report
An independent expert review panel released 165-page report and 2 possible solutions Wednesday
On Wednesday, the Ministry of Transportation made public a 165-page report examining the more than 500 girders manufactured for the Rt. Hon. Herb Gray Park.
The girders, according to the province and engineers, did not meet the standards of the Canadian Highway Bridge Design Code.
Here are some of the highlights and the two recommended solutions from the report done by five members of an independent expert review.
- With respect to the Freyssinet plant, the first concrete for the girders was poured on August 7, 2012, at which time the plant was in the process of attempting to qualify for its requisite Canadian Standards Association (“CSA”) certification. Girders fabricated at an uncertified plant are not permitted to bear the standard-setting CSA certification mark. Certification of the plant had been held up due to Freyssinet’s failure to comply with 13 items on CSA’s Certification Program Checklist. However, despite there being no CSA certification at the time, Freyssinet continued to produce the girders, and, between August 7 and November 19, 2012, a total of 203 girders were fabricated.
- Furthermore, apparently unbeknownst to I.O. and MTO at the time of the CSA certification on November 19, 2012, there was another lurking issue which would soon emerge – the use of tack welding to hold together the cages containing welded wire reinforcing mats – which would also affect I.O.’s and MTO’s views of the Freyssinet girders. As discussed below, the
- Canadian Highway Bridge Design Code (CSA S6-2006) (“CHBDC”) provides that tack welding of reinforcing steel is not permitted, unless it has been approved by a “Regulatory Authority”, in this case, MTO.
- On January 18, 2013, Ken Kapusniak, P.Eng. wrote a letter to Franck Chavent of Freyssinet, in which he stated that he has been familiar with the production of the girders in the Freyssinet plant, where he had served as Quality Verification Engineer (“QVE”) from August 2012 to November 12, 2012, and later as the Retained Engineer. As such, he had no problem signing the [Canadian Standards Association] Statement of Compliance forms for all girders manufactured in the plant to the date of his letter.
- Ken Kapusniak had worked for concrete precasting companies. Ken Kapusniak is not a structural engineer and has limited girder experience in Ontario.
- The results of forensic decomposition of the girders from August 19 – 21, 2013 revealed several facts about the girders. These included horizontal and inclined cracks in the web of girder ends and strand misalignment; and spacing between strands was not adhered to the design. Cracking was observed in nine girders and some of the cracks were described as ”thru cracks cutting through the width of the web”.
- A May 10, 2013 letter from Mr. Hatchell identified that only one (1) out of four (4) welders was certified to CSA W18691 a full nine (9) months after the start of operation of the plant.
- There is irrefutable evidence that Freyssinet Quality Control has fallen short of the project needs.
- Products manufactured with a lack of quality control cannot be deemed safe or durable, because even small deviations from shop drawings have the potential to lead to major problems immediately or in the future.
- There was a comment made in the CSA audit regarding the use of tack welding. It was noted that some of the bars were undercut and some of the tack welds appeared to be of poor quality.
- Tack welding of reinforcing bars is not permitted, since it can reduce fatigue resistance.
- It is irrefutable that tack welding of structural reinforcement for bridge structures is ‘discouraged’ and only the design engineer can assess its potential impact on the project. Variance from the CAN/CSA S6-06 must therefore be pre-approved. Tack welding of the Parkway girders was done without record and the evidence from forensic testing confirms the uncertainty with respect to their safety and durability.
- Based on the information received so far, it is the opinion of the IER Committee that the girders do not meet the requirements of the applicable regulations, codes and standards. With various violations in the design and construction requirements and the uncertainties in the construction of these girders, the IER cannot unequivocally opine that the girders are safe and durable. In fact, there is evidence that safety and durability of the girders have been compromised.”
- The IER Committee is unanimous that, unless there is a satisfactory remediation protocol, it is an irresistible conclusion that the 500 girders fabricated by Freyssinet are not acceptable for use in the Rt. Hon. Herb Gray Parkway
The IER Committee has therefore considered and now recommends two options, as follows:
As stated earlier, it is not possible to have legal compliance of the 500 girders retroactively with all applicable regulations, codes and standards. To achieve this, the only option is to replace deficient and non-compliant girders with new ones that are constructed in accordance with all the applicable requirements for design and construction.
Existing non-compliant girders may be salvaged for service through the steps listed below. In the development of these steps, IER Committee considered the recent test results, some of which were found to be encouraging although they did not address all the concerns related to durability of the girders:
- Survey the girders for visible deficiencies and signs of distress. Measure the deflection profile when they are supported at the ends. This step is aimed at identifying the girders that have a large or unusual deflection profile and may not be suitable for use.
- Of the girders selected for use, strengthen girders that are deemed deficient in shear using a mechanism that reduces stress in the internal stirrups to address the fatigue problem that may be caused by tack welds. Results from the ongoing tests should be considered to determine the extent of strengthening. The spans of the girders where stirrups are used at large spacing (600 mm in some cases) are especially vulnerable if the stirrups are compromised due to tack welding and do not perform as intended.
- The strengthening mechanism discussed in paragraph number 2 above must meet the required fire-rating.
- Tack welding is known to increase the risk of corrosion of steel. The corrosion rate in the welded stirrups should be monitored at selected critical locations and steps taken to mitigate the adverse effects of corrosion.
- In the tests carried out by ProjectCo, the pre-stressing tendons have been reported to be misaligned. This may result in under-stressing of the girders, excessive stress concentration in the end zones, pre-mature cracking and excessive deflection. Steps must be taken to address these issues.
- Since the girders have been found to be deficient with respect to compliance with the design and construction requirements that will compromise their strength and durability, robust continuous structural health monitoring is required to ensure their performance in the short and long terms. In addition, an enhanced inspection regime by
- independent trained professionals is required to mitigate possible hazards arising from the deficiencies of the girders.
- With respect to T2, T3, T5 and T7, if any girder should exhibit shear cracking before the Expiry Date, as defined and set out in the Project Agreement, such girder should be replaced by ProjectCo at its sole cost and expense.