INNOVATION November-December 2017

A comprehensive plan for installation and erection of the bridge included a 225-metre highline and work platform for the installation of the suspension elements and deck structure.

cable-type structures is feasible when the models are fairly simple and relatively stiff, but have severe convergence challenges when the stiffness is reduced. While the structure in its final condition is relatively stiff, during construction you are transitioning from a completely slack system to the final condition. All-Span learned quickly that the application of non-uniform loads reflecting different construction stages, along with incomplete load resisting elements, led to large displacements, which were difficult to model. Approximate hand calculations and alternative methods needed to be performed daily as sanity checks to ensure model results were reasonable and meaningful. OLIVER AL-JANABY, P.ENG. (AB), PROJECT ENGINEER , GRAHAM INFRASTRUCTURE LP PROJECT ROLE: TEMPORARY WORKS ENGINEER We needed a braking tool for unwinding the suspension cables as we launched them across the river. The braking force required was considerable due to the long span and heavy unit weight of the cables. We had started with a plan to buy a manufactured tool, however the supplier turned out to be unable to meet our schedule. As a result we had to design and build the tool ourselves in an extremely short time frame.

AIDAN CONNELL, SENIOR PROJECT MANAGER, GRAHAM INFRASTRUCTURE LP PROJECT ROLE: PROJECT MANAGER My biggest challenge was ensuring that every scope of work performed met the required schedule. Although my team performed much of the work, many subcontractors and suppliers had critical roles in ensuring project success. To achieve the owner’s target of public access by Christmas 2016, every individual subcontract and supplier was held to tight deadlines to ensure a successful outcome. To understand how difficult building this bridge would be for the crew, I travelled out in a purpose-built mobile platform over the Columbia River before main span erection commenced. This provided a very real sense of the daily challenges the crew would be exposed to. This proved to be a valuable learning experience for me, giving me an appreciation of the role of temporary works engineering in making this erection method possible, and more importantly, safe. BARRY GERBRACHT, P.ENG., SENIOR STRUCTURAL ENGINEER , ALL-SPAN ENGINEERING & CONSTRUCTION PROJECT ROLE: ERECTION ENGINEER Suspension bridges present many challenges that are unusual when compared to

conventional beam and girder, truss, or arch-type bridges. Getting the cables across the river, installing the deck and floor beams while maintaining stability, geometric control, and managing material stresses on a highly-flexible structure are not easy feats. All of the machinery for pulling the cables across the river and the high line system used to install all of the structural elements were one-off custom designed pieces. Once all of the methods and equipment had been designed, the operation of the equipment and process had to be communicated to the workers performing the actual construction. Understanding the hazards associated with each process and determining the expected structure behavior during each stage of execution was imperative to ensure worker safety. Dealing with highly flexible and non-linear structures is a significant challenge and a great learning experience. Most structural analysis software packages cannot deal with large displacement modeling. Modeling

Focusing on your construction needs in BC, across Canada and everywhere else you do business. John S. Haythorne P.Eng D +1 604 691 6456 john.haythorne@dentons.com

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