Updated: Dec 10, 2019
This post was stimulated by some of you who’ve reached out recently to seek advice on your growth as bridge engineers. While you receive on-the-job training working at design firms, in general, there is a lack of career-building mentoring. Now that I think about it, other than what I picked up from working on projects, there wasn’t any sort of formal mentoring during my formative years (the first 3-5 years of an engineer’s career) and it seems many EITs of today are in the same boat. Assuming you are actively engaged in structural analysis and getting exposure to the design of bridge components (both in steel and concrete), I would recommend four simple practices to incorporate in your training that will accelerate your technical development.
Practice 1: Sketch it
Some of the most skilled bridge engineers I’ve worked with rely heavily on hand sketches to convey ideas as they germinate in their minds. Sketches are a quick and easy way for creative expression, communicating, brainstorming and refining ideas into concepts. They also enhance your ability to visualize the problem in three dimensions (3D). I find that these days, the value of sketching is not emphasized enough at universities and engineering offices. You tend to quickly jump on a computer even before concepts are clearly formed in your mind.
I would encourage you to develop the practice of depicting problems and potential solutions through freehand sketching first, where appropriate. Your sketches do not need to be of exceptional quality (leave that for artists and architects); so, with basic attention to relative proportioning you will be able to draw effectively for the purposes of discussion and to support your calculations. Where you require more precision such as detailing rebar in concrete sections, you can use CAD software to prepare sketches that can be passed on to drafters as a starting point for drawings production.
Practice 2: Visualize it
Training yourself to picture in your mind’s eye is a very important skill for a bridge engineer to gain a superior grasp of the problem, which is half the battle in developing context-sensitive solutions. One of the intangible benefits of the practice of sketching is that it will develop your ability to visualize as well. You can imagine how useful this skill would be on brown-field highway improvement projects with stacked interchange bridges and curved ramps that involve geometric and construction phasing complexities.
In addition to visualization of the physical situation, an aptitude to understand a structure and trace the flow of forces through it is very useful. To develop these visualization muscles, I picked up a drill form a long-standing colleague that I’m sure you would find very beneficial. Be on the lookout for interesting structures in your natural environment: bridges, buildings, stadiums, roofs (especially at airports, railway stations and even churches) and try to piece together the structural system: cantilevers, frames, girders, arches, cable-stays, trusses and so on. Attempt to trace the flow of vertical and lateral forces. Don’t lose heart if you struggle; make a simple sketch entailing a free-body diagram (FBD) for deeper understanding and for later discussion with your peers or supervisor. As an example, I’ve included a simple FBD of the BC Place Stadium roof showing how it balances vertical loads through a compression and tension ring.
Practice 3: Think Big Picture
It is easy for us to get lost in the weeds early in our careers as there is so much to learn technically about various bridge types and all their associated parts and pieces. Nonetheless, I would encourage you to develop the practice of stepping back; visualize ascending to a bird’s eye view to understand the big picture of how your bridge fits into the larger scheme of things on the project and how other disciplines interface with yours.
Your scope may not involve developing the configuration of the bridge but ask your supervisor on how the general arrangement came about. Learn about the influence of highway geometrics on the bridge layout and vice versa. Are there other roadway alignment possibilities and why were they not best suited? Ponder specific site challenges such as the need to maintain traffic flow along the highway corridor or continuity of critical utilities to the adjacent residential neighborhood. Would your bridge need to be built in stages to allow traffic flow during construction or can you use the old bridge as a detour? Many other site-specific issues such as environmental sensitivities, hydraulic or geometric clearances, private property and right of way, the proximity of railway lines, etc. impact the permanent configuration and/or construction phasing of your bridge. Make it your business to understand how those challenges were addressed even though your task on the project may be limited to the bearings only.
If I had to pick one discipline that is most important to a bridge engineer, it would be geotechnical engineering and inputs, especially in seismic areas with high variability in sub-surface conditions. One can bury a lot of costs in the ground here. Therefore, it is important early in your career to start developing a feel for the various foundation types taking every opportunity possible to interact with geotechnical experts. Again, pick your supervisor’s brain on the rationale behind the foundation type(s).
Practice 4: Think Construction
Since most bridge firms are not engaged in the practice of erection engineering, your work is likely concerned with the bridge in its final state only. I learned while working on cable-stayed bridges that the erection sequence has a major influence on the final stress state and geometry. On typical highway girder bridges, this is not the case, and this is precisely why most EITs don’t need to give much thought to erection stages. Still, I would encourage you to think about how the prefabricated components (structural steel or precast girder segments) of your bridge will be transported, staged and erected. This exercise will also make you delve into access, right-of-way, sizes & positioning of cranes and possible site conflict issues.
In some instances, even for girder bridges, you will need to assess and verify that your bridge can survive the temporary erection stages such as in the case of incremental launching. The sketch shows an erection concept for the closure segment of a steel box girder using a tandem crane lift, with the left truck crane positioned on a lower level pre-existing bridge and the right crawler sitting on mats along railway tracks (requiring a 4 hr closure to complete the operation). Note that the cantilever erection methodology locks in relatively larger the dead load moments over the piers and smaller positive moments at mid-span compared to the erection of a conventionally long center span segment. Therefore, this locked-in stress state from the erection methodology should be considered in the demand envelope and camber calculations.
As a practice, on every bridge you work on, try to conceive the possible ways it could be constructed from the foundations up to the superstructure. Make a habit of reviewing your thoughts with your supervisor. I remember once being surprised to see the enormity of an actual 3.5m (11.5 ft) deep girder compared to how insignificant it looked on paper! Therefore, take every opportunity to go to the site to witness construction activities especially on assignments where you were involved in the production of the design.
I’ve articulated the above practices from twenty years of experience in bridge and erection engineering, which has included a wide variety of bridges (short creek spans to long river crossings and everything in between) and feel that most mentors never articulate the importance of the above aspects to EITs. It is left for you to discover on your own along the way. I’m confident that consciously incorporating these practices early in your training will propel your bridge engineering career.