Innovative Concepts for Hydraulic Steel Structures - Folded-Plate Gates
In recent years folded-plate constructions have been designed and in many cases built for various types of gate as an alternative to conventional crossbeam structures. The empirical evidence so far available shows that this type of design has a positive impact on parameters such as production and preservation, bearing capacity redundancy, fatigue resistance, ease of maintenance and inspection, and maintenance costs.
Folded plate gats mainly consist of sheet-metal plates which are bent horizontally into trapezoid folds. The folds are welded at their ends with vertical end brackets, which may take the form of box girders, which divert forces into the concrete structure. Folded-plate constructions usually make use of butt seams and for this reason the requirements for welding in cold formed areas must be taken into account. Picture 1 shows a lift gate built according to a folded-plate design and picture 2 a mitred lock gate with a folded-plate design during construction. This construction principle should always be considered as a potential alternative every time a new gate is designed.
Other folded-plate constructions have already been put to use by the WSV. Folded plates can clearly be used for lock gates and in sliding and lift gates. However, folded plates can prove problematic for gates and valves which are also used to fill or empty chambers owing to the hydraulic procedures involved. The underflows of these gates can produce significantly increased driving forces as well as vibrations in bypass or longitudinal culvert sluice gates. In the case of mitred lock gates which are also used to fill or empty chambers, getting the mid-placed drive rod (when two gates or valves are being driven simultaneously) through the folded plate is an extremely difficult design challenge. At the same time, the generally high fatigue resistance of folded plates is considerably reduced causing additional corrosion protection problems. Another limitation may be gate dimensioning. Using a folded-plate design is not recommended if the gate is much wider than it is high. Lift gates (sliding gates, mitred lock gates) with widths of ≥ 24.00 m may also require sheet metal thicknesses which are no longer controllable using standard turning benches.1
Smaller or even bigger design changes may have a negative impact on the otherwise beneficial aspects of folded plates, such as design form, production and preservation, near improbability of total failure, more advantageous detail categories and greater ease of maintenance and inspection.
1 Meinhold, W./Gabrys, U./Binder, G./Baumann, M./Kunz, C.: Chapter 7: Stahlwasserbau; Stahlbau-Kalender 2006, Ernst & Sohn, Berlin 2006