Masonry Magazine February 1993 Page. 17
TABLE 4
REINFORCEMENT FOR STACK BOND
| Wall Thickness in. | Area of Steel Req'd. in.2/ft. | USE | Steel Supplied in.2/ft. |
|---|---|---|---|
| 4 | 0.029 | 2-9 ga. wires @8o.c. | 0.052 |
| 6 | 0.045 | 2-9 ga. wires @8o.c. | 0.052 |
| 8 | 0.061 | 2-8 ga. wires @8o.c. | 0.061 |
| 10 | 0.077 | 29/16" wires @8" o.c. | 0.083 |
| 12 | 0.093 | 4-9 ga. wires @8°o.c. | 0.104 |
supplied by bond beam steel. Use 2-#4 bars (area 0.40 in.).
When considering whether or not to use 16" diameter wire for joint reinforcement, 2 points should be considered: (1) When 16" wire is used the mortar used must be at least Type S or Type M. Type N mortar does not develop enough strength to fully develop the steel strength. (2) 3/16" joint reinforcement is the largest size allowed when " bed joints are used. This does not present a problem for "straight" joint reinforcement, but when adjustable tie assemblies are specified, their overall thickness can be such that it can become difficult to install the heavy duty assembly. As a general rule, bond, workmanship and productivity will increase when 9 ga. joint reinforcement is used at close spacing as compared to extra heavy joint reinforcement at normal spacing. The requirement for joint reinforcement in the veneer wythe of cavity walls also comes from existing codes. Its purpose is to provide improved ductility in and anchorage of the veneer wythe. Some codes require that there be a positive connection between the joint reinforcement in the joint and the wall tie. This is best accomplished in a one piece assembly. Some manufacturers make plastic devices to connect the joint reinforcement to ties. These are cumbersome bulky, and combustible. Figure 3 shows a typical veneer tie assembly with veneer joint reinforcement.
Seismic Performance Categories D&E
These categories cover the balance of buildings built across the country with Category E pertaining to buildings built in the red shaded map area that also fall under Seismic Hazard Exposure Group III. The horizontal reinforcement requirements for these categories are essentially the same as those for traditional reinforced masonry in the Uniform Building Code. It should be noted that any special Continued on Page 62
Construction Posts November Setback
THE RATE OF CONTRACTING for new construction fell back ten percent in November, following a surge of activity in the previous month. reported the F.W. Dodge Division of McGraw-Hill. The November volume lowered the seasonally adjusted Dodge Index to 92 (1987 100), close to the level that prevailed over a five month period at midyear when the recovery of the construction industry lost momentum.
All three of the industry's main sectors retreated during November. In particular, there was a sharp slide in the vulnerable residential building market.
"Given the tenuous quality of this recovery over the past year and a half, a setback from October's strong showing wasn't surprising." said Dodge's vice president of economic affairs Robert A. Murray. "It still remains to be seen just how durable the current upturn will be. Even so, a broader time frame offers a more positive slant on the industry's current status, as total construction was up seven percent during 1992's first eleven months. This modest improvement stands in contrast to the performance of 1990 and 1991, which showed annual declines of nine and six percent, respectively."
Nonresidential construction in November plunged seventeen percent to its weakest value so far in 1992, with reduced contracting reported by most of the categories. Manufacturing construction was down sharply from the usually robust amount reported in October, while an earlier rebound for institutional building proved to be short-lived. The overbuilt commercial market remained dismal, although store construction was a bright spot with its third consecutive advance.
Residential construction slipped four percent in November, as the value of single family starts eased back from October's gain. Given improved consumer confidence and generally low mortgage rates, the pace of single family activity is likely to pick up in the quarters ahead.
For the first eleven months of 1992, the seven percent gain in total construction was essentially due to a strengthening housing market. Residential construction advanced sixteen percent during this period, while nonbuilding construction showed a more subdued four percent rise.
Geographically, activity in the North Central region advanced thirteen percent, followed by the South Central's nine percent rise. Trailing the country's midsection were the South Atlantic and the Northeast, each up six percent, and the West, up three percent.
TABLE 3
SPECIAL DESIGN
REQUIREMENTS
SPC SPECIAL REQUIREMENTS
A-No special requirements
B-No special reinforcement requirements but shear walls must be designed rationally
C-Arbitrary, prescriptive reinforcement requirements for increased ductility even if building is designed "empirically"
D-Building must be designed as "reinforced" with minimum horizontal and vertical reinforcement
E-Special requirements for tying horizontal and vertical steel