Note: Prior ordinance history: Ord. Nos. 1945CCS and 2380CCS.
Appendix Chapter A2 of the California Existing Building Code
2022 Edition, entitled "Earthquake Hazard Reduction in Existing Reinforced
Concrete and Reinforced Masonry Wall Buildings with Flexible Diaphragms"
of the International Existing Building Code, 2021 Edition, as published
by the International Code Council (excluding Sections A201, A202,
A203, A205 and A206) is hereby adopted as the Mandatory Seismic Retrofit
Requirements for Existing Concrete and Reinforced Masonry Wall Buildings
with Flexible Diaphragms of the City of Santa Monica.
(Added by Ord. No. 2537CCS §
3, adopted 3/28/17; amended by Ord. No. 2623CCS § 14, adopted 10/22/19; Ord. No. 2727CCS § 15,
adopted 10/25/22)
The purpose of this Chapter is to enhance public safety by providing
an improved component of seismic strengthening to existing concrete
and reinforced masonry wall buildings with flexible diaphragms and
reducing risks from the effect of earthquakes. This Chapter addresses
the hazards of these buildings by establishing requirements for the
analysis, design of structural strengthening elements, and seismic
retrofit of these buildings.
This Chapter and the requirements therein are considered minimum
standards for structural seismic resistance. They are intended to
provide a greater measure of safety through improved performance of
existing concrete and reinforced masonry wall buildings with flexible
diaphragms. Compliance with this Chapter does not necessarily prevent
the loss of life or injury or damage to retrofitted buildings.
(Added by Ord. No. 2537CCS §
3, adopted 3/28/17)
The provisions of this Chapter shall apply to all concrete or
reinforced masonry buildings with flexible diaphragms, including tilt-up
concrete wall buildings, built under building code standards enacted
before January 1, 1996.
Concrete or reinforced masonry buildings with flexible diaphragms,
including tilt-up concrete wall buildings that have completed all
required seismic retrofit work, with a lateral load resisting analysis
and structural design plans, and obtained valid final approval from
the City of Santa Monica prior to the adoption of the ordinance codified
in this Chapter, are exempt from the requirements this Chapter.
An owner of any building within the scope of this Chapter shall
demonstrate compliance with the mandatory seismic retrofit requirements
of this Chapter consistent with the time limits set forth in this
Chapter.
(Added by Ord. No. 2537CCS §
3, adopted 3/28/17)
For purposes of this Chapter, applicable definitions in the
California Building Code and the following shall apply:
is the system of all structural elements and connections
which support the concrete or masonry wall in the lateral direction,
including diaphragms and subdiaphragms, wall anchorage and continuity
or cross tie connectors in subdiaphragms and main diaphragms for retrofit
and repairs.
is a mechanical fastener placed in hardened concrete or assembled
masonry, designed to expand in a self-drilled or predrilled hole of
a specified size and engage the sides of the hole in one or more locations
to develop shear and/or tension resistance to applied loads without
grout, adhesive or drypack.
is any diaphragm constructed of wood structural panel, diagonal
or straight wood sheathing or decking, metal decking without a structural
concrete topping, or horizontal rod bracing.
is a building with masonry walls which have twenty-five percent or more of the reinforcing steel ratios required by the building code for reinforced masonry and is not classified as an unreinforced masonry wall building pursuant to Chapter 8.60 of the Santa Monica Municipal Code.
is a form of precast concrete panel construction either cast
in the horizontal position at the site or cast off-site in a fabricator's
shop, and then lifted and moved into place in a vertical position.
(Added by Ord. No. 2537CCS §
3, adopted 3/28/17)
(a)
Reinforced Concrete and Reinforced Masonry Wall Anchorage. Concrete and masonry walls shall be anchored to all floors and roofs
that provide lateral support for the wall. The anchorage shall provide
a positive direct connection between the wall and floor or roof construction
capable of resisting seventy-five percent of the horizontal forces
specified in Chapter 16 of the California Building Code.
(b)
Special Requirements for Wall Anchorage Systems. The steel
elements of the wall anchorage system shall be designed in accordance
with the building code without the use of the 1.33 short duration
allowable stress increase when using allowable stress design.
Wall anchors shall be provided to resist out-of-plane forces,
independent of existing shear anchors.
Exception: Existing cast-in-place shear anchors are allowed
to be used as wall anchors if the tie element can be readily attached
to the anchors, and if the engineer or architect can establish tension
values for the existing anchors through the use of approved as-built
plans or testing and through analysis showing that the bolts are capable
of resisting the total shear load (including dead load) while being
acted upon by the maximum tension force due to an earthquake.
Expansion anchors are only allowed with special inspection and
approved testing for seismic loading.
Attaching the edge of plywood sheathing to steel ledgers is
not considered compliant with the positive anchoring requirements
of this Chapter. Attaching the edge of steel decks to steel ledgers
is not considered as providing the positive anchorage of this Chapter
unless testing and/or analysis are performed to establish shear values
for the attachment perpendicular to the edge of the deck. Where steel
decking is used as a wall anchor system, the existing connections
shall be subject to field verification and the new connections shall
be subject to special inspection.
(c)
Development of Anchor Loads into the Diaphragm. Development
of anchor loads into roof and floor diaphragms shall comply with Chapter
16 of the California Building Code using horizontal forces that are
seventy-five percent of those used for new construction.
Exception: If continuously tied girders are present, the maximum
spacing of the continuity ties is the greater of the girder spacing
or twenty-four feet (7,315 mm).
In wood diaphragms, anchorage shall not be accomplished by use
of toenails or nails subject to withdrawal. Wood ledgers, top plates
or framing shall not be used in cross grain bending or cross grain
tension. The continuous ties required in Chapter 16 of the California
Building Code shall be used in addition to the diaphragm sheathing.
Lengths of development of anchor loads in wood diaphragms shall
be based on existing field nailing of the sheathing unless existing
edge nailing is positively identified on the original construction
plans or at the site.
(d)
Anchorage at Pilasters. Anchorage at pilasters shall be designed for the tributary wall-anchoring load per subsection (a) of this Section, considering the wall as a two-way slab. The edges of the two-way slab shall be considered fixed when there is continuity at pilasters and shall be considered pinned at roof and floor. The pilasters or the walls immediately adjacent to the pilasters shall be anchored directly to the roof framing such that the existing vertical anchor bolts at the top of the pilasters are bypassed without permitting tension or shear failure at the top of the pilasters.
Exception: If existing vertical anchor bolts at the top of the
pilasters are used for the anchorage, additional exterior confinement
shall be provided as required to resist the total anchorage force.
The minimum anchorage force at a floor or roof between the pilasters shall be that specified in subsection (a).
(e)
Symmetry. Symmetry of wall anchorage and continuity connectors
about the minor axis of the framing member is required.
Exception: Eccentricity may be allowed when it can be shown
that all components of forces are positively resisted. The resistance
must be supported by calculations or tests.
(f)
Combination of Anchor Types. New anchors used in combination
on a single framing member shall be of compatible behavior and stiffness.
(g)
Anchorage at Interior Walls. Existing interior reinforced concrete or reinforced masonry walls that extend to the floor above or to the roof diaphragm shall be anchored for out-of-plane forces per subsections (a) and (c). Walls extending through the roof diaphragm shall be anchored for out-of-plane forces on both sides, and continuity ties shall be spliced across or continuous through the interior wall to provide diaphragm continuity.
(h)
Collectors. If collectors are not present at reentrant corners
or interior shear walls, they shall be provided. Existing or new collectors
shall be designed for the capacity required to develop into the diaphragm
a force equal to the lesser of the rocking or shear capacity of the
reentrant wall or the tributary shear based on seventy-five percent
of the horizontal forces specified in Chapter 16 of the California
Building Code. The capacity of the collector need not exceed the capacity
of the diaphragm to deliver loads to the collector. A connection shall
be provided from the collector to the reentrant wall to transfer the
full collector force (load). If a truss or beam other than a rafter
or purlin is supported by the reentrant wall or by a column integral
with the reentrant wall, then an independent secondary column is required
to support the roof or floor members whenever rocking or shear capacity
of the reentrant wall is less than the tributary shear.
(i)
Mezzanines. Existing mezzanines relying on reinforced concrete or reinforced masonry walls for vertical and/or lateral support shall be anchored to the walls for the tributary mezzanine load. Walls depending on the mezzanine for lateral support shall be anchored per subsections (a), (b) and (c).
Exception: Existing mezzanines that have independent lateral
and vertical support need not be anchored to the walls.
(Added by Ord. No. 2537CCS §
3, adopted 3/28/17)
(a)
Except as provided in subsection (b) below, the owner of any building covered by this Chapter shall comply with the following time limits.
|
Action by Building Owner
|
Time Limits from Date of Service of Order
|
|---|---|
|
Structural Evaluation Report
|
120 Days or 4 Months
|
|
Application for Building Permit and Submission of Plans
|
270 Days or 9 Months
|
|
Final Approval
|
3 Years or 36 Months
|
(b)
Notwithstanding subsection (a) above, the owner of any building covered by this Chapter that has received a permit: (1) issued and active as of March 13, 2020; (2) issued between March 13, 2020 and December 31, 2022; or (3) issued pursuant to a complete application submitted between March 13, 2020 and December 31, 2022 shall comply with the following time limits.
|
Action by Building Owner
|
Time Limits from Date of Service of Order
|
|---|---|
|
Structural Evaluation Report
|
2 years, 4 Months; or 28 Months
|
|
Application for Building Permit and Submission of Plans
|
2 years, 9 Months; or 33 Months
|
|
Final Approval
|
5 Years or 60 Months
|
(Added by Ord. No. 2537CCS §
3, adopted 3/28/17; amended by Ord. No. 2689CCS § 3, adopted 1/25/22)
