(a) Anchor locations. All URM walls shall be anchored at the roof and floor levels as required in subsection
9-12.603(b) of this chapter. Ceilings with substantial rigidity and abutting masonry walls shall be connected to walls with tension bolts at a maximum anchor spacing of six feet. Ceiling systems with substantial mass shall be braced at the perimeter to diaphragms.
(b) Anchor requirements. Anchors shall be tension bolts through
the wall as specified in Table 12-D of this chapter or by an equivalent
approved by the Building Official at a maximum anchor spacing of six
feet. All existing wall anchors shall be secured to the joists to
develop the required forces.
(c) Minimum wall anchorage. Anchorage of masonry walls to each
floor or roof shall resist a minimum force determined by:
or 200 pounds per linear foot, whichever is greater,
acting normal to the wall at the level of the floor or roof. Existing
floor wall anchors must meet or must be upgraded to meet the requirements
of this chapter if utilized in the design. Existing roof anchors shall
not be utilized in the design.
(d) Anchors at corners. At the roof and all floor levels, both
shear and tension anchors shall be provided within two feet horizontally
from the inside of the corners of the walls.
(e) Anchors with limited access. When access to the exterior
face of the masonry wall is prevented by proximity of an existing
building, wall anchors conforming to Item 5b in Table 12-D of this
chapter may be used.
(§ 1, Ord. 678, eff. July 12, 1991)
Collector elements shall be provided which are capable of transferring
the seismic forces originating in other portions of the building to
the element providing the resistance to those forces.
(§ 1, Ord. 678, eff. July 12, 1991)
Ties and continuity shall conform to Section 2312(h)2E of the
Uniform Building Code.
(§ 1, Ord. 678, eff. July 12, 1991)
(a) General. Where a wall height-thickness ratio exceeds the specified limits, the wall may be laterally supported by vertical bracing members in accordance with the provisions of subsection
(b) of this section or by reducing the wall height by bracing in accordance with the provisions of subsection
(c) of this section.
(b) Vertical bracing members. Vertical bracing members shall
be attached to floor and roof construction for their design loads
independently of required wall anchors. Horizontal spacing of vertical
bracing members shall not exceed one-half (½) the unsupported
height of the wall nor 10 feet. Deflection of such bracing members
at design loads shall not exceed one-tenth of the wall thickness.
(c) Wall height bracing. The wall height may be reduced by bracing
elements connected to the floor or roof. Horizontal spacing of the
bracing elements and wall anchors shall be as required by design but
shall not exceed six feet on center. Bracing elements shall be detailed
to minimize the horizontal displacement of the wall by the vertical
displacement of the floor or roof.
(§ 1, Ord. 678, eff. July 12, 1991)
Parapets and exterior wall appendages not conforming to this
chapter shall be removed or stabilized or braced to ensure that the
parapets and appendages remain in their original position.
The maximum height of an unbraced URM parapet above the lower
of either the level of tension anchors or roof sheathing shall not
exceed two times the thickness of the parapet wall. If the required
parapet height exceeds this maximum height, a bracing system designed
for the force factors specified in Table 23-P of the Uniform Building
Code for walls shall support the top of the parapet. Parapet corrective
work must be performed in conjunction with the installation of tension
roof anchors.
The minimum height of a parapet above the wall anchor shall
be 12 inches; provided, however, that, if a reinforced concrete beam
is provided at the top of the wall, the minimum height above the wall
anchor may be six inches.
(§ 1, Ord. 678, eff. July 12, 1991)
(a) URM
walls which carry no design load other than their own weight may be
considered as veneer if they are adequately anchored to new supporting
elements.
(b) Veneer
shall be anchored with approved anchor ties conforming to the required
design capacity specified in the Uniform Building Code and placed
at a maximum spacing of 24 inches with a maximum supported area of
two square feet; provided, however, that 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:
(1) Existing veneer anchor ties shall be corrugated galvanized iron strips
not less than one inch in width, eight inches in length and one-sixteenth
(1/16) of an inch in thickness or equal and shall be located and laid
in every alternate course in the vertical height of the wall at a
spacing not to exceed 17 inches on centers horizontally.
(2) As an alternate, such ties may be laid in every fourth course vertically
at a spacing not to exceed nine inches on centers horizontally.
(c) The
location and condition of existing veneer anchor ties shall be verified
as follows:
(1) An approved testing laboratory shall verify the location and spacing
of the ties and shall submit a report to the Building Official for
appeal as a part of the structural analysis.
(2) 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.
(§ 1, Ord. 678, eff. July 12, 1991)
Where trusses and beams other than rafters or joists are supported
on masonry, independent secondary columns shall be installed to support
vertical loads of the roof or floor members. The loads shall be transmitted
down to adequate support.
(§ 1, Ord. 678, eff. July 12, 1991)