Category: Bridges

The new Samuel de Champlain bridge opened to traffic on two very important days. The northbound lanes heading into Montreal were opened on June 24^th, when the province of Quebec celebrates Saint Jean Baptiste Day. The southbound lanes heading to Brossard opened on July 1^st, when Canada celebrates the founding of the country.

These opening days are symbolic of how important the original Champlain bridge, and now the Samuel de Champlain bridge, are to North America. According to Infrastructure Canada, this bridge is crossed 50 million times each year (https://www.infrastructure.gc.ca//nbsl-npsl/faq-eng.html).

This translates to approximately 140 000 vehicles per day, or 5 800 vehicles per hour, making the crossing one of the most important bridges in North America.

How does a 3.4 km long bridge, with a final price tag of around $4.5 billion, get built? A project of this scale requires an organized group of thousands of people to achieve such a feat of Engineering. For years these people have been spending their days, nights, and weekends, often in extreme temperatures and weather conditions, ensuring that each individual task gets done on time, and on budget. So, who are these everyday heros?

There are many different roles that need to be filled to complete a project of this scale. To understand the range of specialties needed, consider the following groups of professionals who have contributed to the project:

• Construction workers: Build the bridge, piece by piece. Includes work on site and in fabrication shops.
• Construction Engineer: Coordinate construction works on and off the jobsite, ensuring the safety and quality of the works.
• Engineer of Record: Design the bridge by calculating the exact loading expected from traffic, and create a structural system that can carry these loads safely across the river.
• Independent Engineer: Check the design of the Engineer of Record, and spot-check the on-site works.
• Environmental Engineers: Create systems to protect the environment before, during and after construction.
• Geotechnical Engineers: Verify the condition of the soil and rock to ensure the bridge can rest on solid foundations.
• Durability Engineers: Ensure that all materials and methods used for construction are going to meet the durability requirements of the bridge, which includes 125 years with no major repair works.
• Quality Control Engineers: Verify the quality of the materials being received on site, and ensuring the quality documentation is filed per project requirements.
• Document Controllers: Coordinate and document millions of documents relating to every aspect of the project.
• Owners Engineer: Develop the overall concept of the bridge prior to awarding the project, in coordination with the Architect.
• Others: There are numerous other groups that participated in the project, including risk management, finance, law, asset management, etc.

Within these professions, there is a large variation in the types of tasks required. Consider the role of the Engineer of Record (EOR). For the Samuel de Champlain bridge, the EOR consisted of T.Y. Lin International, Systra-International Bridge Technologies, and SNC-Lavalin.

From the pre-bid works to final completion, the EOR is constantly engaged on a wide range of different roles to ensure that the bridge gets built according to the project agreement and all relevant design standards. These roles include, but are not limited to:

• Help develop an estimate of the materials and cost of construction with the contractor, to provide a competitive bid to win the project.
• When the project is awarded, use the project requirements, design criteria and design standards to determine the size, shape, material and connection of the entire bridge.
• Independently check the work of the other partners in the EOR team, to ensure the quality and safety of the design.
• Work with the contractor to verify the method of lifting and installing each of these pieces.
• Provide construction site support to the contractor at every stage of the construction, as part of the certification process for the bridge.

After the many millions of hours worked on this bridge, there is one final product that will last for at least the next 125 years. That translates to more than 6.3 billion vehicles trips, most of which will be made by people who are not even born yet. This single projection highlights the magnitude of what has just been accomplished in Montreal.

The importance of every single person who contributed to the project cannot be overstated, and has helped deliver a bridge that Montreal, and Canada, can be truly proud of for generations.

Humans have been building bridges for thousands of years. At first, they were built using trial and error. Recently, humans began to use math and physics to create bigger, safer, and more economical structures. Paired with new materials, economic prosperity, and the development of the Bridge Engineering profession, this has led to the creation of some truly magnificent structures.

When the Brooklyn Bridge was completed in 1883, it had the longest main span (distance between vertical supports) in the world.  Since then, this feat has been surpassed hundreds of times. In 1937, using the same type of support system, the Golden Gate Bridge was constructed with a main span that is 2.5 times longer than the Brooklyn Bridge. Around 60 years later, the Akashi Kaikyo bridge increased that by 1.5 times.

The five bridges with the longest mains spans in the world are presented in the below table. All of these are suspension bridges, similar to the Golden Gate and Brooklyn bridges.

The theoretical limit on the length of a suspension bridge is governed by the self-weight of the support cable and deck system.  Theoretically, the longest possible length of a suspension bridge, using present day materials, is approximately 5 km. This is 2.5 times longer than the longest bridge built to date. However, there are many practical restraints that would make the construction of such a long span nearly impossible.

In the past century, the materials and methods used for construction have developed at a slow pace, and there have been few significant changes in the general form of long span bridges. Some may believe that engineers have reached the peak performance of construction materials, while others may argue that the current base of knowledge is sufficient for the majority of bridges that society needs. So why would engineers continue to push the boundaries of bridge construction?

Because, we are engineers – and that’s what we do!

Engineers are always looking for ways to improve bridges, either by building them faster, cheaper, or safer. However, only a small group focus on a very interesting challenge – how to make them longer. In a recent paper (link to paper), an analytical model was developed using a numerical layout optimization procedure to study the theoretically optimal form that a very long span bridge should have. One of the most interesting concepts that comes out of this paper is the split-pylon form, presented below. This bridge is shown with a main span of 5 km, which is 2.5 times longer than the longest bridge ever built.

This new structural form would be difficult to construct using present day techniques, as it may require significant temporary supports when erecting the split pylons. However, the final optimal form provides a brand-new artistic form for a bridge – similar to the forms that became popular after the development of suspension and cable stay bridges. This balance of engineering optimization and form need only find a balance with economy, to become a truly plausible option.

At the very least, this paper significantly adds to our understanding of how long span bridges can be built using present day materials. It also offers hope to the bridge engineering profession, and opens up many new potential problems, and exciting challenges, that we get to deal with.

Even if a bridge like this never gets built, it will help to inspire others to study the feasibility of new structural forms for long span bridges. And that, is very exciting!

Engineers use scientific knowledge to push the boundaries of the physical world. but how risky is it?

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Engineering is a very dynamic industry, and the scope of what engineers do constantly changes. At the core, Merriam-Webster defines engineering as:

“The application of science and mathematics by which the properties of matter and the sources of energy in nature are made useful to people”

This is an incredibly broad description that encapsulates many activities. From building bridges to space stations, engineers design and build the visible (and more recently the non-visible) world around us. What this definition does not convey is that an engineer’s job is understanding and taking on risk.

With every new bridge, the engineer of record uses their theoretical knowledge to design the structure to an acceptable level of safety. In modern times, this level of risk is defined in technical and regional design codes and specifications. In the past, however, the acceptable level of safety was defined based on the experience of the engineers involved. This has created some engineering folk tales, including one where clients were forcing engineers to stand underneath their new bridges during load tests. This ensures that the engineer is literally held accountable for any short-comings in the design. I have heard this tale in many different countries around the world, and hope it was not true!

In modern society, a governing body licenses engineers by region. For each project, the engineer takes on the responsibility to protect the investment and safety of the public, client, and all stakeholders. As a result,

“each engineer must walk a tight line between being a designer and a lawyer.”

Each and every decision that an engineer makes can impact cost, schedule, and safety. It is therefore imperative that engineers understand the scope of risk that they are taking on, with relation to the project agreement.

This is something that engineers, both junior and senior, can struggle with. In design-build contracts, for example, it is imperative that the scope of risk is understood by everyone, and maintained throughout the duration of the project. However, these lines can often get blurred when quick decisions are needed. It is at times like these that engineers must use caution in how they respond to each question, as small changes in wording can significantly impact the level of risk that engineers are exposing themselves, and their companies, to.

Since understanding this aspect of engineering can often govern the way we work and interact with clients and the public, it is imperative that this be taught to engineers in school, and early on in their careers.

This will not only help protect the public by maintaining accountability for risk, it will also protect our engineering firms from taking on unnecessary risk.

Like many, I grew up fascinated with how things work – how they are put together, how they stay together, who makes them – and how I can become involved with them. After some research (with books, dial-up internet time was restricted so my father would not miss a call), I found out my true calling – to be an Engineer.

Of all the interesting and challenging engineering disciplines, I decided that I wanted to be a Bridge Engineer. To put it simply: we take a problem (river), add a requirement (need to cross said river), and come up with a solution (bridge). Believe it or not, in most cases designing the bridge and its components is not the hardest part – it’s having to build them fast, cheap, and sometimes beautiful (more on this last point later). As the American Civil Engineer, Arthur M. Wellington put it,

An engineer can do for a dollar what any fool can do for two.

This is the key to the engineering profession. We innovate to save society money, which increases the number of infrastructure projects, which leads to more innovation and cost-savings. It’s a wonderful cycle! But there is something that seems to be missing in the modern day definition of a Bridge Engineer. In the below image, we have a bridge. This was designed by an Engineer, and is a common form for a present day highway overpass – but not many people would refer to this bridge as beautiful.

Many people believe that this can be solved, simply by adding a “Bridge Architect” to these projects. Indeed, the Ministry of Transportation of Ontario (MTO) has taken this to heart, by recently making it mandatory on some signature projects. The most famous example of this is the engineer turned architect, Santiago Calatrava. As shown below, he cares deeply of the artistic originality of his bridges.

However, this all comes at a large price tag – which is always paid for by tax payers. For example, the Peace Bridge was built for $24.9 million, and construction was delayed by 1.5 years. In addition to the high initial cost, the city has needed to repair broken windows ($152 K) and install new lights ($700 K), partly due to design problems (read more: Calgary Herald). This seems to be a recurring issue with Calatrava projects (read more: D Magazine).

Luckily there is a solution, and it’s very simple – education. Engineers study long and hard for years to master the physics behind bridge structures. However, very little time is put aside to teach students how to use this knowledge to create beautiful structures. As engineer David Billington put it, the art of bridge engineering is to balance form, function and economy. If you need proof, consider the Salginatobel Bridge shown below, designed by Bridge Engineer Robert Maillart.

This bridge was the cheapest solution submitted, and for this reason only, was it built. Because Maillart had studied both the physics and form of bridges, he was able to create this masterpiece. But this is an extreme case. Consider this simple flyover bridge in Ontario. It was clearly not designed to be a signature bridge – but the attention to detail and form paid by the Bridge Engineer resulted in both an economical and arguably beautiful structure.

Therefore, it is essential that bridge engineers stop selling their services as a commodity, and start re-discovering the influence that a good Bridge Engineer can have on society.

This must start in the classroom.

The new Champlain Bridge corridor project in Montreal, Canada will cost up to $4.5 billion, and is planned for completion on December 1, 2018. But what’s wrong with the current bridge? Why was the decision made to build a new one, with such a large price tag?

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Spark-Notes (Easy Read)

This section provides a quick, non-technical summary of this post. For more details, including some more technical information, continue to the following section.

• Current Champlain Bridge, open to traffic in 1962.
• Designed by engineers at SNC.
• Designated a life-line route off the island during emergencies.
• A 2011 report found that the main span was in good condition, but the concrete girders were deteriorating faster then expected.
• If one of these beams fails, the bridge could collapse.

If the new bridge is finished on time, experts predict that a total of $550 million will have been spent on repairs. In October 2017, experts announced that it would cost an additional $250 million to keep the current bridge in service until 2020.

As a result of this assessment, and after years of discussions, the government of Canada finally decided to proceed with  construction of the new Champlain Bridge. Stay tuned for a future post on the construction of the New Champlain Bridge!

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Detailed Notes (Technical)

This section provides more details and technical information, expanding on the points discussed in the spark-notes section.

Condition of the existing bridge

For years, experts were discussing potential options for repairing or replacing the existing bridge. However, the findings from the study conducted by the engineering firm Delcan (see full report) was the catalyst that started the process of designing and building the new bridge. The study was commissioned in August of 2010 to determine the current state of the Champlain Bridge. Although the bridge is considered a lifeline for the island of Montreal, it was found that the bridge would not be able to withstand extreme seismic events.

The steel main span superstructure was found to be in relatively good condition, but the prestressed concrete girders, used for the approach spans, exhibited significant deterioration from the salt water running off the bridge roadway. The condition of the steel reinforcement in these girders cannot be determined, due to the potential dangers of damaging the pre-stressed strands. However, there is evidence of damaged and broken strands inside the concrete. The report also found that failure of the edge girders could lead to the progressive collapse of the bridge.

These findings confirmed that critical repair work was needed on the existing bridge in order to maintain its safety in service. However, the cost to repair the bridge over the next 40 years was found to be equal to the cost to maintain the existing bridge for 15 years while building a new bridge. This point made it very clear to all parties involved that a new bridge was needed – and fast.

Repair work needed

At first glance, the current Champlain bridge looks like it is using every bridge rehabilitation technique ever invented. For civil engineering students at the city’s various universities, it would be a perfect case study, and an easy field trip.

Sensors have been placed across the length of the entire bridge, to monitor its behaviour and deflection during service. In addition, the following repair techniques have been applied:

• A total of 74 steel truss supports have been installed under concrete edge girders, found to be in critical condition.
• External post-tensioning applied longitudinally along the edge girders.
• External post-tensioning applied transversely along the pier caps.
• External fibre reinforced polymer (FRP) wrap applied applied to the exterior of many girders.

Assuming that the new bridge is delivered on schedule, the total repair bill is expected to reach $550 million (CBC).  But with the majority of repairs completed on the existing bridge, and the new bridge planned for completion in December 2018, it seems that Montrealers can rest assured:

The life-line crossing across the Saint Lawrence – one of the busiest bridges in Canada – will continue to be a safe choice for everyone.

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For more photos, visit: Existing Champlain Bridge Photo Album

For more information, see below resources:

https://www.bridgeweb.com/New-reports-highlight-latest-action-needed-at-Champlain-Bridge/3691

http://www.nrcresearchpress.com/doi/pdf/10.1139/l96-941

https://www.theglobeandmail.com/news/national/champlain-bridge-is-falling-down-montreal-pays-for-past-penny-pinching/article15699180/

http://montrealgazette.com/news/local-news/holding-it-together-on-the-champlain-bridge