CIDECT Award 2001
This year the award goes to Silke Williband, who presented the project titled "THE STATIC STRENGTH OF RING-STIFFENED TUBULAR T- AND Y-JOINTS", under the supervision of Dr. Stefan Herion and Dr. Ram Puthli, in Karlsruhe University.
ABSTRACT
T- and Y-Joints are one of the most common connection types in structures made of hollow sections. Due to the high flexibility of the chord face at these connections, the static performance of hollow section can be significantly reduced for slender chords and/or small width ratios between brace and chord. Ring-stiffeners can increase the connection strength so that the member sizes are not dependent upon the connection strength in a structure. In long lattice girders the critical joints are usually close to the supports. Low bending moments (low chord stresses) are accompanied by high shear forces (transmitted from braces) at a support. These joints are easily accessible, allowing a convenient placement of the stiffeners even in smaller hollow sections. In large diameter chords (i.e. bridges, offshore structures) fabrication raises no problems and ring-stiffeners are already in use. However, internal ring-stiffeners have also been shown to be useful in joints having chord diameters under 200 mm. Chords of lattice girders can be made significantly more slender with ring-stiffeners. As the chord members make up to 80% of the weight in lattice girders, the appreciable material savings as well as the savings for transportation and erection easily exceed the additional costs for the ring-stiffener fabrication. An additional benefit is the aesthetic appearance, since the stiffeners are not visible from outside.
As there is an urgent need for data on internally ring-stiffened tubular joints from steel designers and fabricators, the German Research foundation (DFG) has supported a theoretical and practical study on this topic. The study considers two flat ring-stiffeners that are placed symmetrically about the saddle point. An FE investigation (see Figure 1) has been done on both T- (90° angle between chord and brace) and Y-Joints (45° and 60° angles) and experimental work (see Figure 2) on ring-stiffened T-Joints has verified the numerical results. The FE work shows that by providing two light ring-stiffeners, the capacity of the stiffened joints can increase by more than 300% compared to the unstiffened joint. For some joints a joint efficiency of close to 100% can be obtained.
.
.
.
Read the letter from the artist Marijke de Goey, author of the Award:
Letter to CIDECT members
For an artist it is indeed a grat honour to be requested to design an award, in this case a Tubular Steel Award, with international "Tubesuppliers" as the principal and promising youngsters as the recipients.
It is gratifying when an Award contains symbolism towards both parties. The flamablue burned steel, as a solid, contemporary base, represents the diligence of the people in the steel industry.
The highly polished strip reflects the inscription "Cidect President's Award" and on the other side of the "ship" the year of the award.
The fact that it is in reverse writing, which reflects in the polished stainless steel, shows that steelmen are resourceful entrepreneurs enabling the youngsters to find answers in their reflexion. After all, even a house can not be built without foundation.
A mast is placed in the ship and this mast is a hollow, square pipe, on the inside of which, the blue weld is still visible. This pipe holds a secret, viz. flexibility. From the pipe emerge two lively, mobile, abstract derwishes. Gold bedecked like kings. They are the future of steel industry. Will they ever find the formulae for the invisible steel containing all the elements which give steel its eternal value!
Marijke de Goey
Amsterdam