Products and solutions, 2008-03-31, 10:30 AM
From standard to superlative
Ingenious stationary shorings help to accelerate building progress on many building sites. One such example concerns the expansion of Vienna's subway for the EURO 2008 soccer tournament.
Its extension into Vienna's fringes is currently calling for the construction of several bridges over land and water. Experts from ThyssenKrupp are designing, developing and assembling the special shorings required for cost-effective bridge construction.
Creativity and many years of experience are essential when it comes to dealing with the basic heavy-duty elements of stationary shorings. Because the latter are always one-off structures composed of frame supports, soldiers, girders, support towers and rolled steel girder columns. In the south of Vienna, in the district of Maria Lanzendorf, the stationary shoring construction team of ThyssenKrupp Xervon Austria GmbH has been successfully developing systems for years, mainly for the Austrian construction industry. The 30-strong special department, whose range of services runs from the initial draft and expert assembly through to final acceptance on site, is currently supervising the construction of several bridge shorings for Vienna's subway.
In the course of the extension of the U2 line to Ernst Happel Stadium and beyond into the northwest of Vienna, the new above-ground route crosses not only the Danube itself, but also a dead channel and various freeways. The good 60 meter long bridge for the new "Seestern" stadium is currently under construction. The dual-span bridge structure consists of two independent, parallel load-bearing structures. These dock directly onto an already completed (cable-stayed) bridge over the Danube and cross the A22 freeway along the banks of the Danube and a freeway feed road. Overall, four 4.2 meter wide hollow box girder shorings with individual spans of between 32 and 35 meters have to be assembled.
Reliability pays off
On behalf of the joint venture consisting of the two Austrian building contractors Östu-Stettin and Hinteregger, ThyssenKrupp Xervon has developed the stationary shoring structure for construction of the bridge. Along with absolute deadline reliability, the key prerequisite is the ability to develop a shoring limited in height to some 50 centimeters. So that freeway traffic can continue unimpeded beneath the bridge, headroom of 4.5 meters is demanded by law. The new bridge starts only 70 centimeters above this. Minus the 23 centimeters for the wooden beam formwork, only little space is left for the shoring. In use are 18 meter long rolled steel girders, resting on suitably stout twin soldiers. "In bridge construction, a pretty run-of-the-mill solution," is the verdict of stationary shoring construction manager Anton Stricker, assessing the technical requirements of this project. For him, the real challenge of the task is "above all our complete reliability in the performance of the job. After all, to install and move the stationary shoring elements, the freeway is always shut down completely at night. Manpower and materials have to be in the right place at exactly the right time."
Superlative technical feat
A superlative technical feat is then required in the subsequent phase of the project, work on which has already started. The subway route crosses the Mühlwasser, a dead channel of the Danube, followed by Vienna's southeast tangential freeway (A23). In this case, a 203 meter long hollow box girder shoring consisting of a total of six bridge spans is involved. The support for the roughly 39.5 meter bridge span over the Mühlwasser is provided by 16 heavy-duty T50 girders 36 meters long that discharge the shoring weight of 25 tons per running meter into two support systems. Overall, the two support systems, each consisting of a pair of ST300 steel soldiers mounted on the existing pier foundations, have to discharge about 1,000 tons of load.
Unlike the original solution of bridging the 36 meter span over the freeway with an advancing shoring, the solution proposed by ThyssenKrupp Xervon has proven to be much cheaper. The freeway is spanned by a rectangular tunnel of rolled steel girders. These roughly 30 HEB 500 rolled sectional girders, each 15 meters long, rest on socketed columns erected between the existing freeway shorings. "A truly creative solution that no one else came up with," beams stationary shoring expert Stricker.