With Castings
in the manufacture of large concrete structures, and SDI is contracted by the manufacturers of those structures. SDI’s post tensioning systems pro-
vide the compression necessary to erect large concrete structures. The systems involve a cast anchor head, a cast bear- ing plate, and a plastic or steel structure that feeds steel wiring through to the base plate, as well as several other miscellaneous components (Fig. 1). The systems are placed on two sides of a concrete structure—bridges are com- mon—and the rebar they anchor is held tight between the two. The concrete structure is then completed around the systems, and what is left is the bridge, or storage tank, or base structure the
original construction company was hired to build. SDI, owned by President Guido
Schwager, employs 80 and operates out of an office space and warehouse in San Jose. In addition to the design and supply of multi-strand post-tensioning systems for civil engineering projects and providing repairs and alterations on post-tensioned structures, the company also makes some erection equipment for segmental bridge construction, and designs and installs automated people mover systems for urban transportation. The company, which has been op-
erating since 1982, does no assembly of its post tensioning systems at its headquarters. The various components
Post tensioning systems provider Schwager Davis has learned the casting ropes from its suppliers.
involved, including the castings, are sent directly to the jobsite, where they are brought together to form the desired equipment. According to Tumason, this aspect of the company’s business model influences the type of casting suppliers the company seeks. “We look for consistent quality [de- livered as-cast],” Tumason said.
Securing the Suppliers SDI has been involved behind the
scenes on some interesting projects over the years (see sidebar “Keeping It Together”). So its recent selection to provide the post tensioning systems for the bridge that will soon span the Hoover Dam wasn’t surprising. Nev- ertheless, it still turned some heads. “This is a pretty high profile project,”
Tumason said. The metalcaster selected to pour the
base plates and anchor heads for the bridge’s post tensioning systems, long- time supplier Farrar Corp., Norwich, Kan., agreed. “This is no doubt one of our ‘cool’ proj-
ects,” said Todd Farrar, the metalcasting company’s sales and marketing manager. In this particular project, the gov-
ernment had elected to build a bridge to force traffic to bypass the Hoover Dam primarily for security reasons. As the bridge is being constructed, post tensioning systems are used to hold rebar inside the concrete and keep the structure compressed. The anchor heads required for this particular project weigh 47 lbs., and the bearing plates weigh in at 40 lbs. Both parts have a diameter of 37 in. The size of the anchor heads and
bearing plates made Farrar the pre- ferred metalcaster for the Hoover Dam project. SDI maintains a list of suppliers it knows can produce the size range of the parts it desires, and the company
Schwager Davis recently was contracted to provide the post tensioning systems used to build the Hoover Dam bypass bridge.
MODERN CASTING / February 2010 33
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68