The truss bridge supportting Rotterdam Market Hall’s facade maintenance system is a nice example of creative 3D structural analysis. It perfectly illustrates how a structural engineer’s job is by no means limited to delivering a design that ensures safety and reliability.
If the Rotterdam Market Hall’s iconic shape captures your imagination, then the inside of this apartment building covering a fresh food market will do so even more. The central Market Square offers a spectacular view of the Horn of Plenty, Arno Coenen’s impressive artwork. Brightly colored giant fish, fruits and vegetables amaze every single visitor.
The Rotterdam Market Hall, including a view on the Horn of Plenty artwork decorating the inside of the building © Ossip van Duivenbode
And while admiring this splendid ‘Rotterdam Sistine Chapel’ the size of two football fields, do you notice the mobile maintenance platform 30 meters above ground level? If so, it will become clear how the cable-net facades and the artwork surface are maintained from the inside.
The mobile maintenance platform is visibly suspended from overhead tracks along the entire length of the Market Hall, enabling the maintenance of the artwork surface and the glass facades from the inside. © Rienus van Est (Estek)
Safety and reliability come first
The maintenance platform has been manufactured and built by Manntech Gevelinstallaties. This company, based in Moerdijk (The Netherlands), has been active for more than 60 years in the area of design, manufacturing and installation of facade maintenance systems. Staalbouwkundig Adviesburo van Odenhoven (Heijningen, The Netherlands) has been using BuildSoft’s structural analysis software Diamonds to engineer the truss bridge that supports the platform.
The truss bridge that supports the maintenance platform is suspended from overhead tracks along the entire length of the Market Hall. A trolley on top of the platform provides the maintenance team with access to the upper part of the artwork surface. The lower parts of the inner facades can be reached from within a nacelle that is suspended with cables from a mobile undercarriage at the bottom of the truss bridge. This creates a maintenance system that allows to handle the entire surface of the inner facade.
Top view of the maintenance platform, including the yoke with pendulum arms (left). © Marcel van Odenhoven
“What makes this project very special” says Marcel, “is the nacelle that can tap into rails that follow the contours of the curved facade. By slackening the cables through which the nacelle is suspended from the mobile undercarriage, that nacelle will move at a fixed distance along the inner facade and will subject the truss bridge to an oblique tensile load. The direction of that load will change as the nacelle moves along the facades.”
3D Diamonds model of the steel truss bridge supporting the maintenance platform, including the suspension from overhead tracks via a yoke with pendulum arms (left side) and a yoke with swivel (right side).
Playing a creative game
In spite of the fact that safety always is a key factor with this kind of project, keeping horizontal deformations under control proved to be extremely important for the Market Hall maintenance platform. Under no circumstances should that platform exert a pressure on the inner facade when the nacelle subjects the truss bridge to an oblique tensile load. The horizontal flexibility of the truss bridge should thus be limited, and that was achieved through a number of braces that deliver the required rigidity. “The nice thing about a 3D structural analysis model that you build with Diamonds” says Marcel, “is that you can easily identify the source of any problem and can then solve it quickly as well by adding stiffness where it is needed most. That’s the typical game any structural engineer should be playing, and I love to play that game within a working environment that gives me the freedom I need to come up with creative solutions.
3D Diamonds model of the steel truss bridge, visualizing horizontal deformations for a specific load case
3D Diamonds model of the steel truss bridge, visualizing buckling check results for compression members
A particular problem that is usually encountered with this type of structure relates to the buckling check of compression members along its upper edge. The edge beam diagonals, which are laterally supported by horizontal structural members in the bottom plane of the bridge, provide an elastic support for the upper edge. As a consequence, its out-of-plane buckling length will be smaller than the distance between the yokes. This reduced buckling length can easily be defined in Diamonds, in order to perform a more realistic buckling resistance check that fully complies with Eurocode 3.”
A sharp eye for makability
Marcel van Odenhoven has been professionally active as a structural engineer for more than 35 years, with a strong focus on the analysis and detailing of steel structures. In that capacity, Marcel delivers services to steel construction companies and engineering offices alike. He has been involved in many high-profile projects in recent years.
“As a structural engineer, I keep thinking carefully about the makability of any structure I am working on” says Marcel. “Hence my special attention to detailing. Easily makable details improve my client’s profitability during the building process. So I take care to extend my focus on makability throughout all projects, small and large. Whether I am dealing with a heavy steel structure for ASML clean rooms, designing a pipe bridge or a small-sized industrial building, makability always comes first.
Of course, that demands a thing or two from the structural analysis software I am using. I consider it absolutely vital that the software makes it easy to “grow” analysis models from concept to detail, increasingly zooming in during the subsequent phases of the analysis process. Personally, I always start out with what I call a master model. That model is then refined depending on the evolving requirements during the design process: calculation of foundation design loads, dimensioning of the steel structure, detailing of connections, … I also expect the software gives me the freedom and flexibility that I need to put my structural imagination to work. Diamonds supports me during all stages of my thought process, and quickly delivers insights into how I can adjust the structural design. In this respect, I very much like the fact that Diamonds helps me report my findings in a clear and comprehensible way to my client or to the chief structural engineer.”
Delivering creative engineering solutions
“This project perfectly illustrate how a structural engineer’s job is by no means limited to delivering a design that ensures safety and reliability” summarizes Marcel van Odenhoven. “That is obviously a prerequisite, but it is actually not sufficient. What is needed is to use the imagination, and really think in terms of makability during the design and detailing of a steel structure. To me, that’s the real game of the structural engineer, and I just love to play that game within Diamonds’ 3D analysis environment. It supports me throughout each and every stage of my thought process, and gives me the freedom I need to work out creative engineering solutions.”