Masonry Magazine June 2009 Page. 35
Today, designers have seismic design categories A-E (Figure 1), which define the degree of protection provided to the public against the potential hazards due to earthquakes. The seismic design categories are based on the expected level of seismicity in a geographic area and the type of building. For example, seismic design category A has the least risk of an earthquake and few additional design requirements, while E is required to meet the strictest seismic design provisions in order to minimize risk of failure during an earthquake.
The vast majority of designers use the International Building Code (IBC), which adapted the ACI 530 Code for Building Code Requirements for Masonry Structures. In ACI 530, designers use Chapter 6, titled Veneer, for general and seismic design applications for masonry construction. In the veneer application, the backup system is designed to carry the entire load with no load requirements for the veneer.
Starting with seismic design categories A and B, ACI 530 has no additional requirements than the normal general requirements for joint reinforcing, anchors and ties.
Seismic design category C is also exempt from any additional joint reinforcing or tie requirements, except where the designer allows the backup system and veneer to share the load. In this rare brick masonry case, the structure is required to have a continuous single wire, minimum 9 gauge (W1.7) at a maximum spacing of 18 inches on center vertically. The continuous wire must be mechanically attached to the backup system by way of adjustable anchors with clips or hooks. The continuous wires are required to provide ductility and post cracking strength.
Seismic design categories D, E and F require continuous wire, minimum 9 gauge, in the veneer at a maximum spacing of 18 inches vertically. The required clips and hooks provide a channel for the continuous wire to lay in the bed joint and transfer the load to the backup system. Since their inception, seismic design categories E and F required these provisions, but not until 2006 was seismic design category D included, after a major modification by the IBC.
New seismic products
WITH THE NEW seismic requirements in design categories D, E and F, the masonry joint reinforcing industry had a new challenge in developing a line of products for seismic applications.
Charlotte, N.C.-based Wire-Bond spent countless hours working on ways to attach a channel part or clip to the end of their adjustable double hook. The part would also need to accommodate a continuous 9-gauge wire, and not exceed one-half the thickness of the mortar joint, normally 3/8-inch thick. The company tried
Work Smarter, Not Harder.
Mobile M50 26"-50 ton stone splitter for Flagstone, River Rock, Brick, Block, Veneer and more!
Your solution just rolled in.
Process more stone in less time at your job site with the Mobile M50 stone splitter. Designed and built for easy operation, simple maintenance and backed by a hard working company that's been building the industry's finest full line of stone processing machines for quarries and masons since 1950. Call today to see how we can save you time and money!
800-350-9313
CEE-JAY TOOL COMPANY. INC
Loveland, Colorado www.ceejaytool.com
READER SERVICE #175
SAFETY IN SCAFFOLDING
Planking
• Testers
• Sealant
WORLD WIDE SHIPPING
Indian Mill Corporation
Houston, TX 866.729.7310
www.indianmill.com
READER SERVICE #205
June 2009
MASONRY 33