(Amended by Ord. No. 171,175, Eff. 7/25/96.)
91.8813.1. General. This section shall apply to every vacant unreinforced masonry bearing wall building within the scope of this division which has not complied with the requirements contained in this division.
91.8813.2. Enforcement. When the Department determines that a building is within the scope of this section, it shall notify the owner and order the owner to bring the building into compliance with the provisions of this section Compliance with such an order shall be accomplished within the time limits set forth herein and any extensions of time granted by the Department. If the owner does not comply within such time limits, then the Department may order the demolition of the building or structure in accordance with the provisions of Section 91.8903.
91.8813.3 Time for Compliance. (Amended by Ord. No. 171,939, Eff. 4/15/98.)
1. For a one-story building with wall anchors installed pursuant to Section 91.8808.3, either before or within 60 days after notice is given by the Department:
Within 180 days after notice is given pursuant to this section, the owner shall submit to the Department either plans and a structural analysis for the proposed structural alterations of the building necessary to comply with the minimum requirements of this division, or an application for demolition of the building or structure.
If the owner elects to perform the proposed structural alterations, then within 270 days after notice is given pursuant to this section, the owner shall obtain the necessary permits for strengthening the building or structure; within 90 days of obtaining a permit to strengthen the building, the owner shall commence strengthening work; and within 18 months after notice is given pursuant to this section, the owner shall complete all strengthening work.
If the owner elects to demolish the building, then within 210 days after notice is given pursuant to this section, the owner shall obtain permits for the demolition of the building or structure; within 21 days of obtaining a demolition permit, the owner shall commence demolition; and within 300 days after notice is given pursuant to this section the owner shall complete the demolition of the building or structure.
2. Time for compliance for all other buildings:
Within 60 days after notice is given pursuant to this section, the owner shall submit to the Department either plans and a structural analysis for the proposed structural alterations of the building necessary to comply with the minimum requirements of this division, or an application for demolition of the building or structure.
If the owner elects to perform the necessary alterations, then within 120 days after notice is given pursuant to this section, the owner shall obtain the necessary permits for strengthening the building or structure; within 21 days of obtaining a permit, the owner shall begin work; and within 365 days after notice is given pursuant to this section, the owner shall complete all strengthening work.
If the owner elects to perform the necessary alterations, then within 120 days after notice is given pursuant to this section, the owner shall obtain the necessary permits for strengthening the building or structure; and within 120 days after obtaining the demolition permit, the owner shall complete the demolition of the building or structure.
91.8813.4. Special Provisions for Damaged Buildings. An unreinforced masonry bearing wall building which is damaged or partially destroyed by fire, flood, wind, earthquake or other calamity or act of God or the public enemy shall be repaired or demolished within six months of such damage or destruction.
DEMAND-CAPACITY RATIO, 0.33 WD/(2vuD) OR 0.33 WD/(2vuD + ΣVc)
ACCEPTABLE SPAN FOR DIAPHRAGMS
(BASED ON DISPLACEMENT CONTROL CONCEPTS)
FIGURE NO. 88-A
(Added by Ord. No. 165,310, Eff. 12/31/89.)
RATING CLASSIFICATIONS
TYPE OF BUILDING | CLASSIFICATION |
Essential Building | I |
High Risk Building | II |
Medium Risk Building | III |
Low Risk Building | IV |
TIME LIMITS FOR COMPLIANCE
REQUIRED ACTION BY OWNER | OBTAIN BUILDING PERMIT WITHIN | COMMENCE CONSTRUCTION WITHIN | COMPLETE CONSTRUCTION WITHIN |
Complete Structural Alterations or Building Demolition | 1 year | 180 days* | 3 years |
Wall Anchor Installation | 180 days | 270 days | 1 year |
*Measured from date of building permit issuance.
SERVICE PROVISIONS AND EXTENDED TIME PROVISIONS**
(Amended by Ord. No. 160,451, Eff. 11/25/85.)
Rating Occupant Classification | Extension of Time if Wall Anchors Load | Minimum Time Periods are Installed | Service of Order |
I (Highest Priority) | Any | One Year | 0 |
II | 100 or more | One Year | 90 Days |
III | 100 or more | One Year | One Year |
More than 50, but less than 100 | One Year | Two Years | |
More than 19, but less than 51 | One Year | Three Years | |
IV (Lowest Priority) | less than 20 | One Year | Four Years |
**Buildings that have obtained a building permit for wall anchors and met the time schedule in Table 88-B for wall anchor installation may utilize the time extensions, which are permitted in Table 88-C prior to the adoption of this ordinance. (Amended by Ord. No. 179,324, Eff. 12/10/07, Oper. 1/1/08.)
HORIZONTAL FORCE FACTORS BASED ON RATING CLASSIFICATION
RATING CLASSIFICATION | IKCS |
I | 0.186 |
II | 0.133 |
III & IV | 0.100 |
HORIZONTAL FORCE FACTORS “IS” FOR PARTS OR PORTIONS OF STRUCTURES
RATING CLASSIFICATION | IS |
I | 1.50 |
II | 1.00 |
III & IV | 0.75 |
HORIZONTAL FORCE FACTOR “CP” FOR PARTS OR PORTIONS OF BUILDINGS OR OTHER STRUCTURES 1
(Amended by Ord. No. 171,939, Eff. 4/15/98.)
PART OR PORTION OF BUILDINGS | DIRECTION OF FORCE | VALUE OF Cp |
PART OR PORTION OF BUILDINGS | DIRECTION OF FORCE | VALUE OF Cp |
Exterior bearing and nonbearing walls; interior bearing walls and partitions; interior nonbearing walls and partitions over 10 feet in height; masonry fences over 6 feet in height | Normal to flat surface | 0.20 |
Cantilever parapet and other cantilever walls, except retaining walls. | Normal to flat surface | 1.00 |
Exterior and interior ornamentations and appendages. | Any direction | 1.00 |
When connected to or a part of a building: towers, tanks, towers and tanks plus contents, racks over 8 feet 3 inches in height plus contents, chimneys, smokestacks and penthouses. | Any direction | 0.20 2,4 |
When connected to or a part of a building: rigid and rigidly mounted equipment and machinery not required for continued operation of essential occupancies. 5 | Any horizontal direction | 0.20 3 |
Tanks plus effective contents resting on the ground. | Any direction | 0.12 |
Floors and roofs acting as diaphragms. | In the plane of the diaphragm | 0.12 6 |
Prefabricated structural elements, other than walls, with force applied at center of gravity of assembly. | Any horizontal direction | 0.30 |
Connections for exterior panels or elements. | Any direction | 2.00 |
For SI: 1 inch = 25.4 mm, 1 foot = 305 mm.
Notes:
2. When located in the upper portion of any building with a height to depth ratio of 5 to 1 or greater, the value shall be increased by 50 percent.
3. For flexible and flexible mounted equipment and machinery, the appropriate values for Cp shall be determined with consideration given to both the dynamic properties of the equipment and machinery and to the building and building or structure in which it is placed.
4. The Wp for storage racks shall be the weight of the racks plus contents. The value of Cp for racks over two storage support levels in height shall be 0.16 for the levels below the top two levels.
5. The design of the equipment and machinery and their anchorage is an integral part of the design and specification of that equipment and machinery. The structure to which the equipment or machinery is mounted shall be capable of resisting the anchorage forces (see also Section 13.6.5 of ASCE-7). (Amended by Ord. No. 179,324, Eff. 12/10/07, Oper. 1/1/08.)
6. Floor and roofs acting as diaphragms shall be designed for a minimum force resulting from a Cp of 0.12 applied to Wp unless a greater force results from the distribution of lateral forces in accordance with Section 12.8.3 of ASCE-7. (Amended by Ord. No. 179,324, Eff. 12/10/07, Oper. 1/1/08.)
ALLOWABLE VALUE OF HEIGHT-TO-THICKNESS RATIO OF UNREINFORCED MASONRY WALLS WITH MINIMUM QUALITY MORTAR 1, 2
(Amended by Ord. No. 171,939, Eff. 4/15/98.)
BUILDINGS W/ CROSS WALLS AS DEFINED BY SECTION 91.8803 | ALL OTHER BUILDINGS | |
Walls of One-story Buildings | 13 - 16
3, 4, 5 | 13 |
First-Story Wall of Multi-story Buildings | 16 | 15 |
Walls in Top Story of Multi-story Buildings | 9 - 14
3, 4, 5 | 9 |
All Other Walls | 16 | 13 |
1. Minimum quality mortar shall be determined by laboratory testing in accordance with Section 91.8809.5 of this Code.
2.
This table is not applicable to buildings of Rating Classification I. Walls of buildings within Rating Classification I shall be analyzed in accordance with Section 91.8808.6 of this Code.
3.
The minimum mortar shear strengths required in Footnotes 4 and 5 shall be that shear strength without the effect of axial stress in the wall at the point of the test.
4.
The larger height-to-thickness ratio may be used where mortar shear tests in accordance with Section 91.8809.5.3 of this Code establish a minimum mortar shear strength of not less than 100 psi (690 kPa) or where the tested mortar shear strength is not less than 60 psi (414 kPa) and a visual examination of the vertical wythe-to-wythe wall joint (collar joint) indicates not less than 50 percent mortar coverage.
5.
Where a visual examination of the collar joint indicates not less than 50 percent mortar coverage and the minimum mortar shear strength when established in accordance with Section 91.8809.5.3 of this Code is greater than 30 psi (207 kPa) but less than 60 psi (414 kPa), the allowable height-to-thickness ratio may be determined by linear interpolation between the larger and smaller ratios in direct proportion to the mortar shear strength.
VALUES FOR EXISTING MATERIALS
(Amended by Ord. No. 181,758, Eff. 8/8/11.)
EXISTING MATERIALS OR CONFIGURATION OF MATERIALS 1 | ALLOWABLE VALUES |
EXISTING MATERIALS OR CONFIGURATION OF MATERIALS 1 | ALLOWABLE VALUES |
1. HORIZONTAL DIAPHRAGMS | |
(a) Roofs with straight sheathing and roofing applied directly to the sheathing. | 100 lbs. per foot for seismic shear. |
(b) Roofs with diagonal sheathing and roofing applied directly to the sheathing. | 400 lbs. per foot for seismic shear. |
(c) Floors with straight tongue-and-groove sheathing. | 150 lbs. per foot for seismic shear. |
(d) Floors with straight sheathing and finished wood flooring. | 300 lbs. per foot for seismic shear. |
(e) Floors with diagonal sheathing and finished wood flooring. | 450 lbs. per foot for seismic shear. |
(f) Floors or roofs with straight sheathing and plaster applied to the joist or values for items 1(a) and 1(c) rafters.2 | Add 50 lbs. per foot to the allowable values for items 1(a) and 1(c). |
2. SHEAR WALL Wood stud walls with lath and plaster | 100 lbs. per foot each side for seismic shear. |
3. PLAIN CONCRETE FOOTINGS | fc’ = 1500 psi unless otherwise shown by tests |
4. DOUGLAS FIR WOOD | Allowable stress same as No. 1 D.F. 3 |
5. REINFORCING STEEL | fy = 18,000 lbs. per square inch maximum |
6. STRUCTURAL STEEL | fy = 20,000 lbs. per square inch maximum |
For SI: 1 pound per foot = 0.0146 N/m, 1 pound per square inch (psi) = 6.895 kPa.
Notes:
1. Material must be sound and in good condition.
2. The wood lath and plaster must be reattached to existing joists or rafters in a manner approved by the Department.
3. Stresses given may be increased for combinations of loads as specified in Section 91.8808.7.2 of this Code.
ALLOWABLE VALUES OF NEW MATERIALS USED IN CONJUNCTION WITH EXISTING CONSTRUCTION
(Amended by Ord. No. 181,758, Eff. 8/8/11.)
NEW MATERIALS OR CONFIGURATION OF MATERIALS 1 | ALLOWABLE VALUES |
NEW MATERIALS OR CONFIGURATION OF MATERIALS 1 | ALLOWABLE VALUES |
1. HORIZONTAL DIAPHRAGMS | |
Plywood sheathing applied directly over existing straight sheathing with ends of plywood sheets bearing on joists or rafters and edges of plywood located on center of individual sheathing boards. | Same as specified in CBC Table 2306.2.1.(1) and 2306.2.1.(2) for blocked diaphragms. |
2. SHEAR WALLS | |
a. Plywood sheathing applied directly over existing wood studs. No value shall be given to plywood applied over existing plaster or wood sheathing. | Same as values specified in CBC Table 2306.3 for shear walls. |
b. Dry wall or plaster applied directly over existing wood studs. | 75 percent of the values specified in CBC Table 2306.7. |
c. Dry wall or plaster applied to plywood sheathing over existing wood studs. | 33 1/3 percent of the values specified in CBC Table 2306.7. |
3. SHEAR BOLTS | |
Shear bolts and shear dowels embedded a minimum of eight inches into unreinforced masonry walls. Bolt centered in a 2-1/2 inch-diameter hole with drypack or an approved non-shrink grout around circumference of bolt or dowel. 1, 3 | 133 percent of the values for plain solid masonry specified in Table No. 88-M. No values larger than those given for 3/4 inch bolts shall be used. |
4. TENSION BOLTS | |
Tension bolts and tension dowels extending entirely through unreinforced masonry secured with bearing plates on far side of wall with at least 30 square inches of area. 2, 3, 4 | 1200 lbs. per bolt or dowel. |
5. COMBINATION SHEAR AND TENSION WALL ANCHORS | |
a. Bolts extending to the exterior face of the wall with a 2-1/2 inch round plate under the head. Install as specified for shear bolts. Spaced not closer than 12 inches on centers. 1, 2, 3 | 600 lbs. per bolt for tension.4 See Item 3 (SHEAR BOLTS) for shear values. |
b. Bolts or dowels extending to the exterior face of the wall with a 2-1/2 inch round plate under the head and drill at an angle of 22-1/2 degrees to the horizontal. Installed as specified for shear bolts. 1, 2, 3 | 1200 lbs per bolt or dowel for tension.4 See Item 3 (SHEAR BOLTS) for shear values. |
c. Through bolt with bearing plate for tension per Item 4. Combined with minimum eight-inch grouted section for shear per Item 3. | See Item 4 (TENSION BOLTS) for tension values.4 See Item 3 (SHEAR BOLTS) for shear values. |
6. INFILLED WALLS | |
Reinforced masonry infilled openings in existing unreinforced masonry walls with keys or dowels to match reinforcing. | Same as values specified for unreinforced masonry walls. |
7. REINFORCED MASONRY | |
Masonry piers and walls reinforced per CBC Section 2106 and Section 91.2107 of this Code. | Same as values determined per CBC Section 2106. |
8. REINFORCED CONCRETE | |
Concrete footings, walls and piers reinforced as specified in Division 19 of this Code and designed for tributary loads. | Same as values specified in Division 19 of this Code. |
9. EXISTING FOUNDATION LOADS | |
Foundation loads for structures exhibiting no evidence of settlement. | Calculated existing foundation loads due to maximum dead load plus live load may be increased 25 percent for deadload, and may be increased 50 percent for dead load plus seismic load required by this division. |
For SI: 1 inch = 25.4 mm, 1 square inch = 645.16 mm2, 1 pound = 4.45 N.
2. Bolts and dowels to be 1/2-inch minimum in diameter.
3. Drilling for bolts and dowels shall be done with an electric rotary drill. Impact tools shall not be used for drilling holes or tightening anchor and shear bolt nuts.
4. Allowable bolt and dowel values specified are for installations in minimum three wythe walls. For installations in two wythe walls, use 50 percent of the value specified, except that no value shall be given to tension bolts that do not extend entirely through the wall and are secured with bearing plates on the far side.
ALLOWABLE SHEAR STRESS FOR TESTED UNREINFORCED MASONRY WALLS
Eighty percent of test results in psi not less than | Average test results of cores in psi | Seismic in-plane shear based on gross area |
30 plus axial stress | 20 | 3 psi* |
40 plus axial stress | 27 | 4 psi* |
50 plus axial stress | 33 | 5 psi* |
100 plus axial stress or more | 67 or more | 10 psi max* |
*Allowable shear stress may be increased by addition of 10% of the axial stress due to the weight of the wall directly above.
VALUES FOR EXISTING MATERIALS
(Amended by Ord. No. 179,324, Eff. 12/10/07, Oper. 1/1/08.)
EXISTING MATERIALS OR CONFIGURATION OF MATERIALS 1 | ALLOWABLE VALUES |
EXISTING MATERIALS OR CONFIGURATION OF MATERIALS 1 | ALLOWABLE VALUES |
1. HORIZONTAL DIAPHRAGMS | |
a. Roofs with straight sheathing and roofing applied directly to the sheathing. | 100 lbs. per foot for seismic shear. |
b. Roofs with diagonal sheathing and roofing applied directly to the sheathing. | 250 lbs. per foot for seismic shear. |
2. CROSSWALLS 2, 3 | |
a. Plaster on wood or metal lath. | per side: 200 lbs. per foot for seismic shear. |
b. Plaster on gypsum lath. | 175 lbs. per foot for seismic shear. |
c. Gypsum wall board, unlocked edges. | 75 lbs. per foot for seismic shear. |
d. Gypsum wall board, blocked edges. | 125 lbs. per foot for seismic shear. |
1. Materials must be sound and in good condition.
2. For crosswalls, values of all materials may be combined, except the total combined value shall not exceed 300 lbs. per foot for seismic shear.
3. The cross wall aspect ratio for plaster on wood, metal, or gypsum lath and gypsum wall board shall be a maximum height to width ratio of 1:1.
ALLOWABLE VALUES OF NEW MATERIALS USED IN CONJUNCTION WITH EXISTING CONSTRUCTION
(Amended by Ord. No. 181,758, Eff. 8/8/11.)
NEW MATERIALS OR CONFIGURATION OF ALLOWABLE VALUES | NEW AND EXISTING MATERIALS 1 |
1. HORIZONTAL DIAPHRAGMS | |
Plywood sheathing applied directly over existing straight sheathing with ends of plywood sheets bearing on joists or rafters and edges of plywood located on center of individual sheathing boards. | 225 lbs. per foot for seismic shear. |
2. CROSS WALLS 2, 3 | |
a. Plywood sheathing applied directly over existing wood studs. No value shall be given to plywood applied over existing plaster or wood sheathing. | 1.33 times the values specified in CBC Table 2306.3 for shear walls. |
b. Drywall or plaster applied directly over existing wood studs. | 100 percent of the values specified in CBC Table 2306.7. |
1. Materials must be sound and in good condition.
2. For cross walls, values of all materials may be combined, except the total combined value shall not exceed 300 lbs. per foot for seismic shear.
3. The cross wall aspect ratio for drywall, plaster and gypsum wall board shall be a maximum height to width ratio of 1:1, and for plywood shall be a maximum height to width ratio of 2:1.
DIAMETER BOLT (inches) | EMBEDMENT (inches) | SOLID MASONRY (shear in pounds) | GROUTED MASONRY (shear in pounds) |
1/2 | 4 | 350 | 750 |
5/8 | 4 | 500 | 750 |
3/4 | 5 | 750 | 1100 |
7/8 | 6 | 750 | 1100 |
1 | 7 | 750 | 1100 |
1-1/8 | 8 | 750 | 1100 |