Masonry Magazine October 2003 Page. 18
POST-TENSION MASONRY
Figure 3
Figure 4
Courtesy of Dr. Malcoin Phipps
U.S. codes currently limit prestressed masonry shear walls to low seismic areas.
While architects and engineers are still learning how to design with prestressing, contractors are also learning how to price and construct these walls. Learning to use prestressed masonry provides another method of construction to the contractor's list of abilities. As you will see, the techniques can be used in both new construction and for strengthening and repairing existing buildings.
For new work, prestressing is well-suited to walls of one- and two-story buildings. The systems are ideal for retail buildings, warehouse, offices, gymnasiums, schools and "tallwall" types of buildings. It has also been used for the façade of parking structures. Figure 3 shows a new building that has been constructed using prestressing.
Over 15,000 houses in the southwest U.S. rely on prestressing using the Integra system, a concrete block that utilizes a special internal design to decrease heat penetration.
Figure 4 is a bridge in England; all of the retaining walls are brick reinforced with prestressing tendons.
The repair and strengthening market has taken to prestressing as well. For example, the walls in Figure 5 needed strengthening. As most of you know, masonry strengthening often involves cutting open a wall and inserting reinforcement and grout. Unlike traditional methods, these walls were strengthened with far less cutting and without the wall grout. Figure 6 shows the access ports at the bottom. An additional port was installed at mid-height. The details for these will be shown later.
Figure 5
ASC WAREHOUSE UTICA
Figure 6
Figure 7 shows a historical building in which the ornamental masonry is cast stone. The top finial elements were removed decades ago due to structural problems caused by being too tall and slender. These elements were rebuilt during a recent building restoration using prestressing to secure them to the walls below.
Prefabricated wall panels are another fertile field for prestressing. The prestressing can compensate for shipping and handling stresses, as well as the stresses in the panels once installed.
Courtesy of Ledy Design Group
Courtesy of Ledy Design Group
A BETTER WAY TO CONNECT A MASONRY WALL TO A JOIST, A JOIST GIRDER OR A BEAM
NEW!!
Vertical Sliding Bar
Twist-On Hook
Corrugated Anchor Bar
TWIST-ON GROUTLESS SYSTEM
ALLOWS THE STEEL TO DEFLECT!
ANCHORS THE STRAP IN THE MORTAR BED !
LOAD RESISTANCE IS FULLY TESTED!
HECKMANN BUILDING PRODUCTS INC.
NEW ADDRESS!
1501 N. 31st Ave. Melrose Park, IL 60160-2911
800-621-4140 or 708-865-2403
Fax: 708-865-2640
www.heckmannbuildingprods.com
None of these prestressed masonry projects have any outward appearance to indicate there is anything special about their construction.