17.34.100 Detailed system design requirements.
A. Lateral Force on Elements of Structures and Nonstructural Components. Parts or portions of structures; nonstructural components and their anchorage to the main structural system shall be designed for lateral forces in accordance with the following formula:
Fp = Cp Wp ...................... (100-1)
Wp shall be as defined in Section 2312(c) of the UBC. The value of Cp need not exceed the values set forth in Table No. 17-B.
B. Wall Anchorage.
1. Anchor locations. Unreinforced masonry walls shall be anchored at the roof and floor levels in order to resist the forces specified in this section.
2. Wall anchor requirements. Wall anchors shall be tension bolts through the wall having a maximum spacing of six feet or six times the wall thickness; whichever is less. Alternate anchors shall be combination tension and shear bolts complying with the requirements set forth in Table No. 17A. Tension bolts used to resist required forces may be assumed to develop the allowable values listed in Table No. 17-A. If access to the exterior face of a masonry wall is prevented by proximity of an existing building or when the appearance of through the wall tension anchors will affect the architectural appearance of the building; embedded bolts conforming to Table No. 17-A may be used. Wall anchors shall be secured to the rafters or joists to transfer the required forces into roof or floor sheathing.
3. Minimum wall anchorage force. Anchorage of masonry walls to each floor or roof shall resist a minimum force determined by Formula (100-1) or two hundred pounds per linear foot; whichever is greater; acting normal to the wall at the level of the floor or roof. Existing wall anchors installed under previous permits must meet or must be upgraded to meet the requirements of this chapter.
4. Anchors at corners. At the roof and floor levels, combination tension and shear anchors shall be provided within two feet horizontally from the inside of the corners of the walls.
C. Parapets. Parapets and exterior wall appendages not capable of resisting the forces specified in this section shall be removed; stabilized or braced to insure that the parapets and appendages remain in their original position.
The maximum height of an unbraced unreinforced masonry parapet above the level of tension anchors shall not exceed one and one-half times the thickness of the parapet wall. If the required parapet height exceeds this maximum height; a bracing system designed for the force determined by formula (100-1) shall be installed to support the parapet. Parapet corrective work shall be performed in conjunction with the installation of tension roof anchors.
The minimum height of a parapet above the wall anchor shall be twelve inches.
Exception: If a reinforced concrete beam is provided at the top of the wall; the minimum height above the wall anchor may be six inches.
D. Veneer.
1. Unreinforced concrete beam is provided at the top of the wall; the minimum height above the wall anchor may be six inches.
2. Veneer shall be anchored with approved anchor ties; conforming to the required design capacity specified in this code and placed at a maximum spacing of 24 inches with a maximum supported area of two square feet.
Exception: Existing veneer anchor ties may be acceptable provided the ties are in good condition and conform to the following minimum size; maximum spacing and material requirements.
Existing veneer anchor ties shall be corrugated galvanized iron strips not less than one inch in width; eight inches in length and one-sixteenth of an inch in thickness or equal and shall be located in every alternate course in the height of the wall at a spacing not to exceed eighteen inches on centers horizontally. As an alternate; such ties may be laid in every fourth course vertically at a spacing not to exceed nine inches on centers horizontally.
3. The location and condition of existing veneer ties shall be verified as follows:
a. An approved testing laboratory shall verify the location and spacing of the ties and shall submit a report to the building official for approval as a part of the structural analysis.
b. The veneer in a selected area shall be removed to expose a representative sample of ties (not less than four) for inspection by the building official.
E. Mortar Joints. All deteriorated mortar joints in unreinforced masonry walls shall be pointed with Type S or N mortar. Masonry cements shall not be used. Prior to any pointing; the wall surface must be raked and cleaned to remove loose and deteriorated mortar. All preparation and pointing shall be done under continuous inspection by a special inspection certified to inspect masonry or concrete. At the conclusion of the project; the special inspector shall submit a written report to the building official setting forth the portion of the work inspected.
(Ord. 1882 NCS §1 (part), 1992.)