Report: De la Concorde Overpass Collapse Technical

The falling apart of the overpass bridge in Quebec raised not only concerns but fears among the people together with other bodies concerned with oversight. The bridge built in 1968 did not attain its lifespan of 70 years. The collapse of the bridge happened on the AutoRoute 19. Dessau was the company that carried out the construction of the overpass, after which it started functioning in 1971. The inquiry report noted on various failures in the structure stemming from when it was constructed. The bridge showed signs of failure after only 12 years.

Moreover, repairs were done in 1992 that further weakened the structure due to the development of cracks. In 2004 cracks developed on the road, and there was an inspection of the way by an engineer. In 2006, more issues arose, and Dave Ferera witnessed a large piece of concrete detach from the overpass. The transport patroller received calls that demanded urgent action, but it eventually collapsed without immediate repair. The AutoRoute 19 was below the bridge where the accident happened. The overpass helped connect Montreal with the Laurentian region. The accident did not just take place abruptly without people noting it, many people had noticed that the bridge was in bad shape and needed repair. Residents near highway 19 had seen the progressive deterioration of the bridge and had tried to inform the authorities before the collapse.

A section of the public noticed the sinking of the overpass before its collapse. As a result, various signs led to the breakdown in which the authorities new. The engineer responsible for the construction and supervision was Marcel Dubois, who failed in his duty to ensure the safety of the overpass (Québec & Johnson, 2007, p. 68). Quality control was in the hands of Claude Robert, who failed significantly in his task because of delegating his responsibility (Québec & Johnson, 2007, p. 78). Another engineer who exacerbated failure in the bridge was Tiona Sanago (engineer) (Québec & Johnson, 2007, p. 132). In 2004 Christian Mercier did not thoroughly inspect the bridge in light of the many signs regarding the sorry state of the bridge (Québec & Johnson, 2007, p. 105). The commission drafted in their report the failure by not only the contractor but also the transport authorities in the collapse of the bridge. The public, on the other hand, played a significant role in reminding the various authorities of their duties.

Reasons

The collapse of the bridge did not come as a surprise since the authorities knew about the continual worsening, and if they had acted promptly, they would have prevented the collapse of the bridge. Many issues led to the falling apart of the overpass before its destruction. One important reason for the failure of the bridge was poor design. No calculations were made on the stability of the bridge, particularly concerning the steel reinforcements of the overpass. The cracks that developed in the bridge according to inspection standards should have been measured, and their width recorded together with the type, location, length, depth, and width together with whether the crack was nonstructural or structure (Calvi,  Bentz, & Collins, 2018). There was a flaw in the standards concerning shear reinforcement about the use of large slabs on bridges.

Moreover, there was laxity on the part of the companies that erected the bridge. The main reason for the collapse, in this case, was a shear failure in the bridge contributed by various flaws in design and construction. It is important to note that the different construction processes by the contractor to put more rebar on the upper side created a plane of deterioration where cracks occurred (Fernandes, Matos, Oliveira & Henriques, 2019).

Another reason arose from improper construction while enacting the rebar. The beam seat, along with more rebar at the top, further created a problem in creating a horizontal plane with the possibility of creating shearing forces (Fiset, Bédard, Bastien, & Mitchell, 2018). Such forces would lead to increased deterioration and thus failure at the plane that would course the concrete to fall apart. Besides, the quality of the concrete used was substandard. Substandard concrete for such a large structure worsened matters due to the resulting increased porosity of the concrete. As such, the shear came about because of the improper balance in using reinforcements throughout the concrete.

The cracks that developed in the concrete arose due to various reasons that include the bond stress regarding no—14 bars (Québec & Johnson, 2007, p. 6). The bond formed by concrete and rebar is the bond stress, which is essential in determining the strength of concrete. The weather through the thawing and freezing further caused a deterioration of the concrete. The thawing and freezing came about because of the harsh weather conditions. The repeated freeze and thaw process eroded, creating fissures in the concrete due to the expansion in the reinforcement, particularly after rusting (Brault & Hoult, 2019). The incorrect position of the longitudinal bars led to a reduction in the size of the concrete. Construction errors significantly contributed caused the failure of the bridge concerning the heat of hydration that was generated in the concrete because of the laying of asphalt. Moreover, the impact on the expansion joint further worsened the situation (Desnerck, Lees, & Morley, 2017). Furthermore, the possibility of the use of chemicals in dealing with freeze and thaw action greatly exacerbated the state of the concrete.

Moreover, the contractor did not put into consideration the porosity of the concrete, which led to increased deterioration due to the continuous melting and freezing of concrete. However, the repairs done in 1992 significantly contributed to the progressive decline of the concrete in the overpass and its collapse. The team doing the repairs should have noticed the worsening of the bridge due to exposure to the no. 14 and hangar bars were leading to their corrosion (Quebec & Johnson, 2018, p. 6). The removal part of the concrete affected the bond stress in concrete. The cracks further weakened the bond strength in the concrete, negatively the integrity of the bridge.

Therefore, the significant reasons for the collapse include bad design, supervision mistakes, accidental impact and overload, random inspections, structural deficiencies, and corrosion. Bridges are concrete structures having reinforcement, which should have proper maintenance to ensure the appropriate integrity of the bridge.

Lessons

A lesson from the collapse is that any significant construction without proper constant monitoring and evaluation, together with regular maintenance, results in its eventual failure. Engineering, as such, should follow the standards associated with the construction of different structures. For roads, some rules require tests and high-quality materials in their development. The structural design should consider the issue of shear failure in the process of preventing accidents. Errors in road constructions are lethal since they concern people’s lives.

Moreover, engineers should apply current standards and study the design properly to ensure that no structural mistakes arise after construction. Another critical lesson is the oversight and supervision of the roads. Ensuring that no cracks develop and that repairs are consistent with the design in place is essential. The contractors, in this case, should make regular checks on the roads while the transport authorities should perform their checks too in the process (Kamdar et al., 2018; Moufti et al., 2014). Quality assurance plays a significant role in the proper maintenance and construction of roads. Engineers have to satisfy the boards in place of their professionalism for them to carry out various works.

Conclusion and Recommendations

More can be done in terms of construction and maintenance of road works. Even though there are many bridges, it is essential to recruit more personnel in reducing the cumbersome nature of inspecting bridges in Canada. Besides determining the companies that made which bridges may help quickly identify the uniformity of flaws, if any, in such bridges. Evaluation and monitoring of such bridges will help reduce the workload, particularly if similarities in their state like developing cracks or shear failure are noticed.

Proper oversight by transport authorities is necessary to ensure that the right materials and not substandard ones help in the construction of bridges. Moreover, the authorities should carry out various tests like semi destructive testing to determine the integrity of the concrete and make concrete decisions that may involve exploratory removal. Inspection of bridges should not take place yearly but on a more frequent basis, for instance, quarterly.

It is recommended that the standards on shear failure be at the smallest minimum quantities to ensure total conformity when using thick slabs for bridge construction. Moreover, an update to MTQ manuals will help significantly in ensuring that the cumbersome nature of testing reduces greatly and improve the efficiency of such tests of the 9200 bridges and over.

References

Boyle, P. J. (2019). ‘Building a safe and resilient Canada’: resilience and the mechanopolitics of critical infrastructure. Resilience, 7(1), 59-82.

Brault, A., & Hoult, N. A. (2019). Distributed Reinforcement Strains: Measurement and Application. ACI Structural Journal, 116(4).

Calvi, P. M., Bentz, E. C., & Collins, M. P. (2018). Model for assessment of cracked reinforced concrete membrane elements subjected to shear and axial loads. ACI Structural Journal, 115(2), 501-509.

Commission d’enquête sur le viaduc de la Concorde (Québec), & Johnson, P.-M. (2007). Commission of inquiry into the collapse of a portion of the de la Concorde overpass, October 3, 2006-October 15, 2007: Report. Montréal, Qué.: Commission d’enquête sur le viaduc de la Concorde Québec.

Desnerck, P., Lees, J. M., & Morley, C. T. (2017). The effect of local reinforcing bar reductions and anchorage zone cracking on the load capacity of RC half-joints. Engineering Structures, 152, 865-877.

Fernandes, J., Matos, J. C., Oliveira, D. V., & Henriques, A. A. (2019). Computational framework for a railway bridge maintenance strategies affected by gradual deterioration.

Fiset, M., Bédard, F., Bastien, J., & Mitchell, D. (2018). Thick concrete slab bridges: study of shear strengthening.

Kamdar, A., Kienhöfer, F., Emwanu, B., Heyns, G., & Nordengen, P. A. (2018). Operational improvement outcomes through voluntary compliance in road transport operations.

Moufti, S., Gkountis, I., Jabri, A., Shami, A., Dinh, K., & Zayed, T. (2014). Bridge Inspection, Maintenance, and Management Strategies in Canada. In Istanbul Bridge Conference.