Journal of Formwork System
Title: Climbing formwork system goes horizontal
Full-round concrete placement for Austrian tunnel
Environmental protection issues shaped the plans for a twin-tube vehicular tunnel 1.45 miles long outside the village of Steinhaus in Upper Austria. A cut-and-cover operation requiring the excavation of 650,000 cubic yards of soil, the tunnel itself called for 130,000 cubic yards of concrete to be placed. Because the tunnel stands in groundwater, it was built as what the Austrians call a white tank, a water-- impermeable concrete body with no added impervious external skin. Demanding Austrian standards for these impermeable concrete structures include a high degree of crack limitation and control of concrete temperatures; the mix temperature must be below 65 deg F at placement and cannot rise above 105 deg F during setting.
Monolithic tunnel cross section
At Steinhaus, the contractor built successive 80-foot-long sections of the twin tube using the full-round method, with the base slab, walls, and cover slab all completed for an entire section at a time in a single pour. Monolithic construction contributes significantly to meeting the Austrian white tank requirements because the structure has no longitudinal construction joints where the nonuniform creep and shrinkage of components of different ages could lead to cracking. Eliminating the longitudinal joints also does away with the laborintensive job of waterproofing them. At the same time, it presents a challenging placement schedule.
The tunnel formwork machine When the tunnel contractor, Stra bag Bau AG, proposed doubling the originally planned section length from 40 feet to 80 feet and pouring each section monolithically, the form supplier (Doka) responded by designing and delivering two large-area, highly mechanized, self-propelling form units. Strabag planned to use each forming machine 50 times, working from mid-length of the tunnel toward each end, forming an area of about 15,000 square feet with
Full-round concrete placement for Austrian tunnel
Environmental protection issues shaped the plans for a twin-tube vehicular tunnel 1.45 miles long outside the village of Steinhaus in Upper Austria. A cut-and-cover operation requiring the excavation of 650,000 cubic yards of soil, the tunnel itself called for 130,000 cubic yards of concrete to be placed. Because the tunnel stands in groundwater, it was built as what the Austrians call a white tank, a water-- impermeable concrete body with no added impervious external skin. Demanding Austrian standards for these impermeable concrete structures include a high degree of crack limitation and control of concrete temperatures; the mix temperature must be below 65 deg F at placement and cannot rise above 105 deg F during setting.
Monolithic tunnel cross section
At Steinhaus, the contractor built successive 80-foot-long sections of the twin tube using the full-round method, with the base slab, walls, and cover slab all completed for an entire section at a time in a single pour. Monolithic construction contributes significantly to meeting the Austrian white tank requirements because the structure has no longitudinal construction joints where the nonuniform creep and shrinkage of components of different ages could lead to cracking. Eliminating the longitudinal joints also does away with the laborintensive job of waterproofing them. At the same time, it presents a challenging placement schedule.
The tunnel formwork machine When the tunnel contractor, Stra bag Bau AG, proposed doubling the originally planned section length from 40 feet to 80 feet and pouring each section monolithically, the form supplier (Doka) responded by designing and delivering two large-area, highly mechanized, self-propelling form units. Strabag planned to use each forming machine 50 times, working from mid-length of the tunnel toward each end, forming an area of about 15,000 square feet with