Part 1 — UNREINFORCED MASONRY BEARING WALL BUILDINGS

(a)

Purpose. The purpose of this Chapter is to promote public safety and welfare by reducing the risk of death or injury that may result from the effects of earthquakes on existing unreinforced masonry bearing wall buildings.

The provisions of this Chapter are intended as minimum standards for structural seismic resistance established primarily to reduce the risk of life loss or injury. Compliance with these standards will not

necessarily prevent loss of life or injury or prevent earthquake damage to rehabilitated buildings.

(b)

Scope. The provisions of this Chapter shall apply to all existing buildings having at least one unreinforced masonry bearing wall. Except as provided herein, all other provisions of the Building Code shall apply.

EXCEPTIONS: This Chapter shall not apply to:

1.

Detached one or two family dwellings and detached apartment houses containing less than five (5) dwelling units and used solely for residential purposes.

2.

Essential facilities as defined in Table 23-K of the Building Code.

3.

Hazardous facilities as defined in Table 23-K of the Building Code.

This Chapter does not require alteration of existing electrical, plumbing, mechanical or fire safety systems.

(c)

Definitions. For purposes of this Chapter, the applicable definitions in the Uniform Building Code (UBC) shall also apply.

COLLAR JOINT is the vertical space between adjacent wythes and may contain mortar.

CROSSWALL is a wall that meets the requirements of Section 8915(d)3. A crosswall is not a shear wall.

CROSSWALL SHEAR CAPACITY is the length of the crosswall times the allowable shear value, v c L o .

DIAPHRAGM EDGE is the intersection of the horizontal diaphragm and a shear wall.

DIAPHRAGM SHEAR CAPACITY is the depth of the diaphragm times the allowable shear value, v u D.

FLEXIBLE DIAPHRAGM is a diaphragm of wood construction or other construction of similar flexibility.

NORMAL WALL is a wall perpendicular to the direction of seismic forces.

OPEN FRONT is an exterior wall plane without vertical elements in one or more stories which resist the required lateral forces.

POINTING is the partial reconstruction of the bed joints of URM wall as defined in UBC Standard No. 2442.

UNREINFORCED MASONRY (URM) WALL is a masonry wall in which the area or reinforcing steel is less than twenty-five percent (25%) of that required by the Building Code for reinforced masonry.

UNREINFORCED MASONRY BEARING WALL is a URM wall which provides the vertical support for a floor or roof for which the total superimposed load is over one hundred (100) pounds per linear foot of wall.

YIELD STORY DRIFT is the lateral displacement of one level relative to the level above or below at which yield stress is first developed in a frame member.

(d) Symbols and Notations. For the purposes of this Chapter, the applicable symbols and definitions in the Building Code shall also apply.

A = Area of unreinforced masonry pier, square inches.

A;sub\sub; = Area of the bed joints above and below the test specimen for each in-place shear test.

C p = Numerical coefficient as specified in Section 2312(g) and given in Table 23-P of the Building Code and Table 89-A of this Chapter.

D = In-plane width dimension of pier, inches or depth of diaphragm, feet.

DCR = Demand-capacity ratio specified in Section 8915(d).

F wx = Force applied to a wall at level x, pounds.

H = Least clear height of opening on either side of pier, inches.

h/t = Height/thickness ration of URM wall. Height h is measured between wall anchorage levels.

L = Span of diaphragm between shear walls, or span between shear wall and open front, feet.

L o = Length of crosswall, feet.

L;sub\sub; = Effective span for an open front building specified in Section 8915(d)8, feet.

P D = Superimposed dead load at the top of the pier under consideration, pounds.

P D +L = Actual dead plus live load in place at the time of testing, pounds.

P w = Weight of wall, pounds.

V a = v a A, the allowable shear in any URM pier, pounds.

V cb = Total shear capacity of crosswalls in the direction of analysis immediately below the diaphragm level being investigated, Sv c L o , pounds.

V r = 0.5P D (D/H), the rocking shear of any URM wall or wall pier, pounds.

V wx = Total shear force resisted by a shear wall at the level under consideration, pounds.

V p = Shear force assigned to a pier on the basis of its relative shear rigidity, pounds.

V s = Shear force assigned to a spandrel on the basis of the shear forces in the adjacent wall piers and tributary dead plus live loads.

V test = Load in pounds at incipient cracking for each in-place shear test per UBC Standard No. 23-40.

v a = Allowable shear stress for unreinforced masonry, psi.

v c = Allowable shear value for a crosswall sheathed with any of the materials given in Tables 89-C or 89-D, pounds per foot.

v t = Mortar shear strength as specified in Section 8912(c)3E.

v to = Mortar shear test values as specified in Section 8912(c)3E.

v u = Allowable shear value for a diaphragm sheathed with any of the materials given in Tables 89-C or 89D, pounds per foot.

Sv u D = Sum of diaphragm shear capacities of both ends of the diaphragm.

SSv u D = For diaphragms coupled with crosswalls SSv u D includes the sum of shear capacities of both ends of diaphragms coupled at and above the level under consideration.

W d = total dead load tributary to a diaphragm, pounds.

SW d = Total dead load tributary to all of the diaphragms at and above the level under consideration, pounds.

W w = Total dead load of an unreinforced masonry wall above the level under consideration or above an open front of a building, pounds.

W wx = Dead load of a URM wall assigned to Level × halfway above and below the level under consideration.

(a)

General. All buildings shall have a seismic resisting system conforming with Section 2303(b) of the Building Code, except as modified by this Chapter.

(b)

Alteration and Repairs. Alterations and repairs required to meet the provisions of this Chapter shall comply with all other applicable requirements of the Building Code unless specifically provided for in this Chapter.

(c)

Requirements for Plans. The following construction information shall be included in the plans required by this Chapter:

1.

Accurately dimensioned floor and roof plans showing existing walls and the size and spacing of floor and roof framing members and sheathing materials. The plans shall indicate all existing and new crosswalls and their materials of construction. The location of the crosswalls and their openings shall be fully dimensioned or drawn to scale on the plans.

2.

Accurately dimensioned wall elevations showing openings, piers, wall classes as defined in Section 8912(c)3E, thickness, and heights, wall shear test locations, cracks or damaged portions requiring repairs. The general condition of the mortar joints and if and where the joints require pointing. Where the exterior face is veneer, the type of veneer, its thickness and its bonding and/or ties to the structural wall masonry shall also be reported.

3.

The type of interior wall and ceiling surfaces.

4.

The extent and type of existing wall anchorage to floors and roof when utilized in the design.

5.

The extent and type of parapet corrections which were previously performed, if any.

6.

Repair details, if any, of cracked or damaged unreinforced masonry walls required to resist forces specified in this Chapter.

7.

All other plans, sections and details necessary to delineate required retrofit construction including those items in Section 8916.

(a)

General. All materials permitted by this Chapter, including their appropriate allowable design values and those existing configurations of materials specified herein, may be utilized to meet the requirements of this Chapter.

(b)

Existing Materials. All existing materials utilized as part of the required force resisting system shall be in sound condition or shall be removed and replaced with new material.

(c)

Existing Unreinforced Masonry.

1.

General. All unreinforced masonry walls utilized to carry vertical loads or seismic forces parallel and perpendicular to the wall plane shall be tested as specified in this subsection. All masonry that does not meet or exceed the minimum standards established by this Chapter shall be removed and replaced by new materials or alternatively shall have its structural functions replaced by new materials and anchored to supporting elements.

2.

Lay-Up of Walls. The facing and backing shall be bonded so that not less than ten percent (10%) of the exposed face area is composed of solid headers extending not less than four (4) inches into the backing. The clear distance between adjacent full-length headers shall not exceed twenty-four inches vertically or horizontally. Where the backing consists of two or more wythes, the headers shall extend not less than four (4) inches into the most distant wythe or the backing wythes shall be bonded together with separate headers whose area and spacing conform to the foregoing. Wythes of walls not bonded as described above shall be considered as veneer. The veneer wythe shall not be included in the effective thickness used in calculating the height to thickness and the shear capacity of the wall.

3.

Mortar.

A.

Tests. The quality of mortar in all masonry walls shall be determined by performing in-place shear tests in accordance with UBC Standard No. 24-40. Alternative methods of testing may be approved by the Building Official.

B.

Location of Tests. The shear tests shall be taken at locations representative of the mortar conditions throughout the entire building, taking into account variations in workmanship at different building height levels, variations in weathering of the exterior surfaces, and variations in the condition of the interior surfaces due to deterioration caused by leaks and condensation of water and/or by the deleterious effects of other substances contained within the building. The exact test location shall be determined at the building site by the engineer in responsible charge of the structural design work. An accurate record of all such tests and their location in the building shall be recorded and these results shall be submitted to the Building Department for approval as part of the structural analysis.

C.

Number of Tests. The minimum number of tests per class shall be as follows:

(i)

At each of both the first and top stories, not less than two (2) per wall or line of wall elements providing a common line of resistance to lateral forces.

(ii)

At each end of all other stories, not less than one per wall or line of wall elements providing a common line of resistance to lateral forces.

(iii)

In any case, not less than one per one thousand five hundred (1,500) square feet of wall surface nor less than a total of eight (8).

D.

Minimum Quality Mortar.

(i)

Mortar shear test values, v to , in psi shall be obtained for each in-place shear test in accordance with the following equation:

V to = (V test - P D + L )/A;sub\sub;...........(43-1)

(ii)

Individual unreinforced masonry walls with v to consistently less than thirty (30) psi shall be entirely pointed prior to retesting.

(iii)

The mortar shear strength v t , is the value in psi that is exceeded by eighty (80) percent of all of the mortar shear test values, v to .

(iv)

Unreinforced masonry mortar shear strength, v t , less than thirty (30) psi shall be removed or pointed and retested.

E.

Collar Joints. The collar joints shall be inspected at the test locations during each in-place shear test, and estimates of the percentage of the surfaces of adjacent wythes which are covered with mortar shall be reported along with the results of the in-place shear tests.

F.

Unreinforced Masonry Classes. All existing unreinforced masonry shall be categorized into one or more classes based on shear strength, quality of construction, state of repair, deterioration and weathering See Section 8914(b).

G.

Pointing. All deteriorated mortar joints in unreinforced masonry walls shall be pointed according to UBC Standard No. 24-42. Nothing shall prevent pointing with mortar of all the masonry wall joints before the tests are made.

(a)

Pointing. All preparation and mortar pointing shall be done with special inspection.

Exception: At the discretion of the Building Official, incidental pointing may be performed without special inspection.

(b)

Masonry Shear Tests. In-place masonry shear tests shall comply with UBC Standard No. 24-40.

(c)

Existing Wall Anchors. Existing wall anchors utilized as all or part of the required tension anchors shall be tested in pullout according to UBC Standard No. 24-41. The minimum number of anchors tested shall be four (4) per floor, with two (2) tests at walls with joists framing into the wall and two (2) tests at walls with joists parallel to the wall, but not less than ten percent (10%) of the total number of existing tension anchors at each level.

(d)

New Bolts. One-fourth (1/4) of all new shear bolts and combined tension and shear bolts in unreinforced masonry walls shall be tested according to UBC Standard No. 24-41.

Exception: Special inspection may be provided during installation in lieu of testing.

(a)

Allowable Values.

1.

Allowable values for existing materials are given in Table 89-C and for new materials in Table 89-D. The one-third (1/3) increase in allowable values is not allowed for values in these tables.

2.

Allowable values not specified in this Chapter shall be as specified elsewhere in the Building Code. Allowable values not specified in this Chapter for dead load plus seismic load may be increased thirty-three percent (33%). Allowable values not specified in this Chapter for existing building elements with a combination of dead load plus floor live load plus seismic load may be increased seventy percent (70%).

(b)

Masonry Shear. The allowable unreinforced masonry shear stress, v a , shall be determined for each masonry class from the following equation:

v a = 0.1v t + 0.15P D /A...(45-1)

The mortar shear test value, v t , shall be determined in accordance with Section 8912, and not exceed one hundred (100) psi for the determination of v a .

The one-third (1/3) increase in allowable values of the Building Code is not allowed for v a .

(c)

Masonry Compression. Where any increase in dead plus live compression stress occurs, the allowable compression stress in unreinforced masonry shall not exceed one hundred (100) psi. The one-third (1/3) increase in allowable stress of the Building Code is allowed.

(d)

Masonry Tension. Unreinforced masonry shall be assumed as having no tensile capacity.

(e)

Masonry Shear Modulus. The shear modulus (E v ) for unreinforced masonry, for relative rigidity analysis when masonry is used to resist lateral forces in combination with other materials, may be assumed as ten thousand (10,000) v t , unless substantiated by tests.

(f)

Existing Tension Anchors. The allowable resistance values of the existing anchors shall be forty percent (40%) of the average of the tension tests of existing anchors having the same wall thickness and joist orientation. The one-third (1/3) increase in allowable stress of the Building Code is not allowed for existing tension anchors.

(g)

Foundations. For existing foundations new total loads may be increased over existing loads by twenty-five percent (25%) for dead load only and increased fifty percent (50%) for dead load plus seismic load. Higher values may be justified only in conjunction with a geotechnical investigation.

(a)

General. Except as modified herein, the analysis and design relating to the structural alteration of existing buildings shall be in accordance with the Building Code.

(b)

Selection of Procedure. Buildings shall be analyzed by the general procedure of Section 8915(c), which is based on Chapter 23 of the Building Code or, when applicable, buildings may be analyzed by the special procedure of Section 8915(d).

(c)

General Procedure.

1.

Minimum Design Lateral Forces. Buildings shall be analyzed to resist minimum lateral forces assumed to act noncurrently in the direction of each of the main axes of the structure in accordance with the following:

V = 0.33ZW...(46-1)

2.

Lateral Forces on Elements of Structures. Parts of portions of structures shall be analyzed as required in Chapter 23 of the Building Code.

Exceptions:

i.

Unreinforced masonry walls for which height to thickness ratios do not exceed ratios set forth in Table 89-B need not be analyzed for out-of-plane loading. Unreinforced masonry walls which exceed the allowable h/t ratios of Table 89-B shall be braced according to Section 8916(e).

ii.

Parapets complying with Section 8916(f) need not be analyzed for out-of-plane loading.

3.

Shear Walls (In-Plane Loading). Shear walls shall comply with Section 8915(e).

(d)

Special Procedure.

1.

Limitations for the Application of Section 8915(e). The special procedure of Section 8915(e) may be applied only to buildings with the following characteristics:

A.

Flexible diaphragms at all levels above the base of the structure.

B.

A maximum of six (6) stories above the base of the building.

C.

The vertical elements of the lateral force resisting system shall consist predominantly of masonry or concrete shear walls or steel braced frames or special moment resisting frames (see Section 3212 of the Building Code) each with a maximum overall height-to-length ratio of 1 1/2 to 1.

D.

The lateral force resisting system shall be regulated as defined in the Building Code. Except for a single story building with an open front, a minimum of two lines of vertical lateral force-resisting elements shall be parallel to each axis of the building.

2.

Lateral Forces on Elements of Structures. With the exception of the diaphragm provisions of Section 8915(d), elements of structures shall comply with Section 8915(c)2.

3.

Crosswalls. Crosswalls shall meet the requirements of this subsection.

A.

Crosswall Definition. A crosswall is a wood-framed wall sheathed with any of the materials described in Tables 89-C or 89-D. Spacing of crosswalls shall not exceed forty (40) feet on center measured perpendicular to the direction of consideration, and shall be placed in each story of the building. Crosswalls shall extend the full story height between diaphragms.

Exception:

1.

Crosswalls need not be provided at all levels in accordance with Section 8915(d)4B (iv).

2.

Existing crosswalls need not be continuous below a wood diaphragm at/or within four (4) feet of grade provided:

(i)

Shear connections and anchorage requirements of Section 8915(d)7 are satisfied at all edges of the diaphragm.

(ii)

Crosswalls with a total shear capacity of .07SW d interconnect the diaphragm to the foundation.

(iii)

The demand/capacity ratio of the diaphragm between the crosswalls that are continuous to their foundations shall be calculated as:

DCR = [0.33W d + V ca ]/2v u D...........(46-2) and DCR shall not exceed 2.5.

B.

Crosswall Shear Capacity. Within any forty (40) feet measured along the span of the diaphragm, the sum of the crosswall shear capacities shall be at least thirty percent (30%) of the diaphragm shear capacity of the strongest diaphragm at or above the level under consideration.

C.

Existing Crosswalls. Existing crosswalls shall have a length to height ratio between openings of not less than 1.5. Existing crosswall connections to diaphragms need not be investigated as long as the crosswall extends to the framing of the diaphragm above and below.

D.

New Crosswalls. New crosswall connections to the diaphragm shall develop the crosswall shear capacity. New crosswalls shall have the capacity to resist an overturning moment equal to the crosswall shear capacity times the story height. Crosswall overturning moments need not be cumulative over more than two stories.

E.

Other Crosswall Systems. Other systems such as special moment resisting frames may be used as crosswalls provided that the yield story drift does not exceed one (1) inch in any story.

4.

Wood Diaphragms.

A.

Acceptable Diaphragm Span. A diaphragm is acceptable if the point (L,DCR) on Figure 89-1, falls within Regions 1, 2 or 3.

B.

Demand-Capacity Ratios. Demand-capacity ratios shall be calculated for the diaphragm according to the following formulas:

(i)

For a diaphragm without qualifying crosswalls at levels immediately above or below:

DCR = 0.83ZW d /Sv u D...(46-3)

(ii)

For a diaphragm in a single-story building with qualifying crosswalls:

DCR = 0.83ZW d /(Sv u D + V cb )...(46-4)

(iii)

For diaphragms in a multi-story building with qualifying crosswalls in all levels:

DCR = 0.83ZSW d /(SSv u D + V cb )...(46-5)

(iv)

For a roof diaphragm and the diaphragm directly below if coupled by crosswalls:

DCR = 0.83ZSW d /SSv u D......(46-6)

C.

Chords. An analysis for diaphragm flexure need not be made and chords need not be provided.

D.

Collectors. An analysis of diaphragm collector forces shall be made for the transfer of diaphragm edge shear into vertical elements of the lateral force resisting system. Collector forces may be resisted by new or existing elements.

E.

Diaphragm Openings.

(i)

Diaphragm forces at corners of openings shall be investigated and shall be developed into the diaphragm by new or existing materials.

(ii)

In addition to calculating demand capacity ratios per Section 8915(d)4B, the demand capacity ratio of the portion of the diaphragm adjacent to an opening shall be calculated using the opening dimension as the span.

(iii)

Where an opening occurs in the end quarter of the diaphragm span v u d for the demand capacity ratio calculation shall be based on the net depth of the diaphragm.

Diaphragm Shear Transfer. Diaphragms shall be connected to shear walls with connections capable of developing a minimum force given by the lesser of the following formulas:

V = 1/2ZC p W d ..........(46-7) or

V = v u D...(46-8)

Shear Walls (In-Plane Loading) — Special Procedure.

A.

Wall Story Force. The wall story force distributed to a shear wall at any diaphragm level shall be the lesser value calculated as:

(i) For building without crosswalls:

F wx = 0.33Z(W wx + W d /2)...(46-9) but need not exceed

F wx = 0.33ZW wx + v u D...(46-10)

(ii) For building with crosswalls in all levels:

F wx = 0.25Z(W wx + W d /2)...(46-11)

but need not exceed

F wx = 0.25Z(W wx + SW d (v u D/SSv u D))...(46-12) and need not exceed

F wx = 0.25ZW wx + v u D...(46-13)

B.

Wall Story Shear. The wall story shear shall be the sum of the wall story forces at and above the level of consideration.

V wx = SF wx ...(46-14)

C.

Shear Wall Analysis. Shear walls shall comply with Section 8915(e).

D.

Moment Frames. Moment frames used in place of shear walls shall be designed as required in Chapter 23 of the Building Code except that the forces shall be as specified in Section 8915 (d)6A and the interstory drift ratio shall be limited to 0.005.

Out of Plane Forces — URM Walls.

A.

Allowable URM Wall Height to Thickness Ratios. The provisions of Section 8915(c)2 are applicable except the allowable h/t ratios given in Table 89-B shall be determined from Figure 89-1 as follows:

(i)

In Region 1, h/t ratios for "buildings with crosswalls" may be used if qualifying crosswalls are present in all stories.

(ii)

In Region 2, h/t ratios for "buildings with crosswalls" may be used whether or not qualifying crosswalls are present.

(iii)

In Region 3, h/t rations for "all other building" shall be used whether or not qualifying crosswalls are present.

B.

Walls with Diaphragms in Different Regions. When diaphragms above and below the wall under consideration have DCR s in different regions of Figure 89-1, the lesser h/t ratio shall be used.

8.

Buildings with Open Fronts. A building with an open front on one (1) side shall have crosswalls parallel to the open front and shall be designed by the following procedure:

A.

Effective Diaphragm Span L;sub .....sub; for use in Figure No. 89-1 shall be determined in accordance with the following formula:

L;sub\sub; = 2[(W w /W d ) · L + L]...(46-15)

B.

Diaphragm demand/capacity ratio shall be calculated as:

DCR = 0.83Z(W d + W w )/[(v u D) + V c ]...(46-16)

(e)

Analysis of Vertical Elements of the Lateral Force-Resisting System. Applicable to both general procedure and special procedure buildings.

Existing URM Walls.

A.

Flexural Rigidity. Flexural rigidity may be neglected in determining the rigidity of a URM wall.

B.

Shear Walls with Openings. Wall piers shall be analyzed according to the following procedure:

(i)

For any pier:

(1)

The pier shear capacity shall be calculated as:

V a = v a Dt...(46-17)

(2)

The pier rocking shear capacity shall be calculated as:

V r = 0.5P D D/H...(46-18)

(ii)

The wall piers at any level are acceptable if they comply with one of the following modes of behavior:

(1)

Rocking Mode. Where all piers at a level have shear capacities capable of sustaining rocking, i.e., the pier shear capacity is greater than or equal to the pier rocking shear capacity for each pier, forces in the wall at that level, V wx , shall be distributed to each pier V p , in proportion to P D D/H.

For each pier at that level: V a ≥ V r ...(46-19) and for the wall at that level: V wx ≤SV r ...(46-20)

(2)

Non-rocking Mode. Where at least one pier at a level is incapable of sustaining a rocking mode, i.e., the pier shear capacity is less than the pier rocking shear capacity, forces in the wall at that level, V wx , shall be distributed to each pier, V p , in proportion to D/H, such that V wx = SV p .

For at least one pier at that level:

V a < V r ...(46-21)

For each pier at that level: V p ≤ V a (46-22) and V p ≤ V r ...(46-23)

If V p > V r in one or more piers, omit such piers from the analysis and repeat the procedure for the remaining piers or strengthen and reanalyze the wall.

(iii)

Masonry Pier Tension Stress Unreinforced masonry wall piers need not be analyzed for tension stress.

C.

Shear Walls Without Openings. Shear walls without openings shall be analyzed as for walls with openings except that V r shall be calculated as follows:

V r = (0.50P D + 0.25P w )D/H...(46-24)

2.

Plywood Sheathed Shear Walls. Plywood sheathed shear walls may be used to resist lateral loads for buildings with flexible diaphragms analyzed according to provisions of Section 8915(c). Plywood sheathed shear walls may not be used to share lateral loads with other material along the same line of resistance.

3.

Combinations of Vertical Elements.

A.

Lateral Force Distribution. Lateral forces shall be distributed along the vertical resisting elements in proportion to their relative rigidities, except that moment frames shall comply with Section 8915(e)3B.

4.

Moment Resisting Frames. A moment frame shall not be used with a URM wall in a single line of resistance unless the wall has piers that are capable of sustaining rocking in accordance with Section 8915(e)1B and the frames are designed to carry one hundred percent (100%) of the lateral forces.

(a)

General.

(b)

Wall Anchorage.

Anchor Locations. All unreinforced masonry walls shall be anchored at the roof and floor levels as required in Section 8915(c)2. Ceilings with substantial rigidity and abutting masonry walls shall be connected to walls with tension bolts at a maximum anchor spacing of six (6) feet. Ceiling systems with substantial mass shall be braced at the perimeter to diaphragms.

2.

Anchor Requirements. Anchors shall be tension bolts through the wall as specified in Table No. 89-D, or by an approved equivalent at a maximum anchor spacing of six (6) feet. All existing wall anchors shall be secured to the joists to develop the required forces. The Building Official may require testing to verify the adequacy of the embedded ends of existing wall anchors.

3.

Minimum Wall Anchorage. Anchorage of masonry walls to each floor or roof shall resist a minimum force determined by Section 2312(g)2 of the Building Code or two hundred (200) 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 be upgraded to meet the requirements of this Chapter.

4.

Anchors at Corners. At the roof and all floor levels, both shear and tension anchors shall be provided within two (2) feet horizontally from the inside of the corners of the walls.

5.

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 89-D may be used.

(c)

Collectors. 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.

(d)

Ties and Continuity. Ties and continuity shall conform to Section 2312(h)2E of the Building Code.

(e)

Wall Bracing.

1.

General. Where a wall height-thickness ratio exceeds the specified limits, the wall may be laterally supported by vertical bracing members per Section 8916(e)2 or by reducing the wall height by bracing per Section 8916(e)3.

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 (1/2) the unsupported height of the wall nor ten (10) feet. Deflection of such bracing members at design loads shall not exceed one-tenth (1/10) of the wall thickness.

3.

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 (6) 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.

(f)

Parapets. 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 unreinforced masonry parapet above the lower of either the level of tension anchors or roof sheathing, shall not exceed one and one-half (1 1/2) 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 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 twelve (12) 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 (6) inches.

(g)

Veneer.

1.

Unreinforced masonry walls which carry no design loads other than their own weight may be considered as veneer if they are adequately anchored to new supporting elements.

2.

Veneer shall be anchored with approved anchor ties, conforming to the required design capacity specified in the Building Code and placed at a maximum spacing of twenty-four (24) inches with a maximum supported area of two (2) 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 (1) inch in width, eight (8) inches in length and one-sixteenth (1/16) of an inch in thickness (1" × 8" × 1/16") 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 seventeen (17) inches on centers horizontally. As an alternate, such ties may be laid in every fourth course vertically at a spacing not to exceed nine (9) inches on centers horizontally.

3.

The location and condition of existing veneer anchor 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.

(h)

Truss and Beam Supports. 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.

(i)

Adjacent Buildings.

1.

Where elements of adjacent buildings do not have a separation of five (5) inches, the allowable height/thickness ratios for "buildings with crosswalls" per Table 89-B shall not be used in the direction of consideration.

2.

Where buildings do not have a separation of at least five (5) inches and the diaphragm levels of the adjoining structures differ by more than one and one-half (1 1/2) times the wall thickness, supplemental vertical gravity load carrying members shall be added to support the loads normally carried by the wall and such members shall not be attached to the wall. The loads shall be transmitted down to the foundation.

(a)

Definitions. For the purposes of this Chapter, the applicable definitions in the Building Code shall also apply.

HIGH RISK BUILDING is any building, other than an essential building or hazardous building, having an occupant load of one hundred (100) occupants or more, as determined by Section 3302(a) of the Uniform

Building Code.

Exception: A high risk building shall not include the following:

1.

Any building having exterior walls braced with masonry crosswalls or wood frame crosswalls spaced less than forty (40) feet apart in each story. Crosswalls shall be full-story height with a minimum length of one and one-half (1 1/2) times the story height.

2.

Any building used for its intended purpose, as determined by the Building Official, for less than twenty (20) hours per week.

LOW RISK BUILDING is any building, other than an essential building or hazardous building, having an occupant load as determined by Section 3302(a) of the Uniform Building Code of less than twenty (20) occupants.

MEDIUM RISK BUILDING is any building, not classified as a high-risk building or an essential building or hazardous building, having an occupant load as determined by Section 3302(a) of the Uniform Building Code of twenty (20) occupants or more.

(b)

Rating Classifications. The rating classifications identified in Table 89-E are established and each building within the scope of this Chapter shall also be placed in one such rating classification by the Building Official. The total occupant load of the entire building as determined by Section 3302(a) of the Building Code shall be used to determine the rating classification.

Exception: For purposes of this Chapter, portions of buildings constructed to act independently when resisting seismic forces may be placed in a separate rating classification.

(c)

Compliance Requirements.

1.

The owner of each building within the scope of this Chapter shall, upon service of an order and within the time limits set forth in this Chapter, cause a structural analysis to be made of the building by an engineer or architect licensed by the state to practice as such and, if the building does not comply with earthquake standards specified in this Chapter, the owner shall cause it to be structurally altered to conform to such standards or shall cause the building to be demolished.

2.

The owner of a building within the scope of this Chapter shall comply with the requirements set forth above by submitting to the Building Official for review within the stated time limits:

A.

Within two hundred seventy (270) days after the service of the order, a structural analysis which is subject to the approval by the Building Official, and which shall demonstrate that the building meets the minimum requirements of this Chapter; or

B.

Within two hundred seventy (270) days after the service of the order, the structural analysis and plans for the structural alterations of the building to comply with the Chapter; or

C.

Within one hundred twenty (120) days after service of the order, plans for the installation of wall anchors in accordance with the requirements specified in Section 8916; or

D.

Within two hundred seventy (270) days after the service of the order, plans for the demolition of the building.

3.

After plans are submitted and approved by the Building Official, the owner shall obtain a building permit, and then commence and complete the required construction or demolition within the time limits set forth in Table No. 89-F. These time limits shall begin to run from the date the order is served in accordance with Section 8917 (d)2, except that the time limit to commence structural alteration or demolition shall begin to run from the date the building permit is issued.

4.

Owners electing to comply with subdivision 2C of this subsection are also required to comply with subdivisions 2B or 2D of this subsection; provided, however, that the two hundred seventy (270) day period provided for in subdivisions 2B or 2D and the time limits for obtaining a building permit and to complete structural alterations of building demolition set forth in Table No. 89-F shall be extended in accordance with Table No. 89-G. Each such extended time limit shall begin to run from the date the order is served in accordance with Section 8917(d), except that the time limit to commence structural alterations or demolition shall begin to run from the date the building permit is issued.

(d)

Administration.

1.

Order — Service.

A.

The Building Official shall, in accordance with the priorities set forth in Table No. 89-G, issue an order as provided in this Section to the owner of each building within the scope of this Chapter.

B.

Prior to the service of an order as set forth in Table No. 89-G, a bulletin may be issued to the owner as shown upon the last equalized assessment roll or to the person in apparent charge or control of a building considered by the Building Official to be within the scope of this Chapter. The bulletin may contain information the Building Official deems appropriate. The bulletin may be issued by mail or in person.

2.

Order — Priority of Service. Priorities for the service of the order for buildings within the scope of this Chapter shall be in accordance with the rating classification as shown in Table No. 89-G. Within each separate rating classification, the priority of the order shall normally be based upon the occupant load of the building. The owners of the building housing the largest occupant loads shall be served first. The minimum time period prior to the service of the order as shown in Table No. 89-G shall be measured from the effective date of this Chapter. The Building Official may, upon receipt of a written request from the owner, order such owner to bring his building into compliance with this Chapter prior to the normal service date for such building set forth in this Chapter.

3.

Order — Contents. The order shall be in writing and shall be served either personally or by certified or registered mail upon the owner as shown on the last equalized assessment, and upon the person, if any, in apparent charge or control of the building. The order shall specify that the building has been determined by the Building Official to be within the scope of this Chapter and, therefore, is required to meet the minimum seismic standards of this Chapter. The order shall specify the rating classification of the building and shall be accompanied by a copy of Section 8917(c) which sets forth the owner's alternatives and time limits for compliance.

4.

Appeal From Order. The owner of the building may appeal the Building Official's initial determination that the building is within the scope of this Chapter to the City Council. Such appeal shall be filed with the City Clerk within sixty (60) days from the service date of the order described in Section 8917(d)3 of this Chapter. Any such appeal shall be decided by the Council no later than ninety (90) days after the date that the appeal is filed. Such appeal shall be made in writing upon appropriate forms provided therefore, and the grounds thereof shall be stated clearly and concisely. Each appeal shall be accompanied by a filing fee as set forth by resolution of the City Council. Appeals or requests for modifications from any other determinations, orders or actions by the Building Official pursuant to this Chapter, shall be made in accordance with the normal appeal procedures established in the Building Code.

5.

Recordation. At the time that the Building Official serves the aforementioned order, the Building Official shall file with the office of the County Recorder a certificate stating that the subject building is within the scope of this Chapter, and is a potential earthquake hazardous building. The certificate shall also state that

the owner thereof has been ordered to structurally analyze the building and to structurally alter or demolish it where compliance with this chapter has not been demonstrated.

If the building is either demolished, found not to be within the scope of this Chapter, or is structurally capable of resisting minimum seismic forces required by this Chapter as a result of structural alterations or an analysis, the Building Official shall file with the office of the County Recorder a form terminating the status of the subject building as being classified within the scope of this Chapter.

6.

Enforcement. If the owner or other person in charge or control of the subject building fails to comply with any order issued by the Building Official pursuant to this Chapter within any of the time limits set forth in Section 8917(c), the Building Official shall verify that the record owner of this building has been properly served. If the order has been served on the record owner, then the Building Official shall order that the entire building be vacated and remain vacated until such order has been complied with. If compliance with such order has not been accomplished within ninety (90) days after the date the building has been ordered vacated, or by such additional time as may have been granted by the City Council, the Building Official may order its demolition of the building in accordance with the Abatement of Dangerous Buildings provisions of the Building Code.

(Chapter 9 added by Ord. 1916 adopted 12-5-89; amended by Ord. 1924 adopted 8-7-90; amended by Ord. 2033 adopted 2-7-95)

Table No. 89-A

Horizontal Force Factor C p

Table No. 89-B

Allowable Value of Height-Thickness Ratio of Unreinforced Masonry Walls

;hg0;All other walls

16 13

1 Applies to the Special Procedures of Section 8915(d) only. See Section 8915(d)7 for other restrictions.

2 This value of height-to-thickness ratio may be used only where mortar shear tests in accordance with Section 8912 established a tested mortar shear strength, v t , of not less than 100 psi or where the tested mortar strength, v t , is not less than 60 psi and a visual examination of the collar joint indicates not less than 50% mortar coverage.

3 Where a visual examination of the collar joint indicates not less than 50% mortar coverage and the tested mortar shear strength, v t , when established in accordance with Section 8912 is greater than 30 psi but less than 60 psi, the allowable height-to-thickness ratio may be determined by linear interpolation between the larger and smaller ratios in direct proportion to the tested mortar shear strength, v t .

Table No. 89-C

Allowable Values for Existing Materials

1 Material must be sound and in good condition.

2 Shear values of these materials may be combined, except the total combined value shall not exceed 300 lbs. per foot.

3 Stresses given may be increased for combinations of loads as specified in Section 8914.

4 A one-third increase in allowable stress is not allowed.

Table No. 89-D[4]

Allowable Values of New Materials Used In Conjunction with Existing Construction[1]

1 Bolts to be tested as specified in Section 8913.

2 Bolts 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 and tightening anchors and shear bolt nuts.

4 A one-third increase in allowable stress is not allowed.

Table No. 89-E

Rating Classifications

Table No. 89-Fl;eolTime Limits for Compliance

1 Measured from the date of the service of order.

2 Measured from date of building permit issuance. Table No. 89-G Extensions of Time and Service Priorities

Uniform Building Code Standard No. 24-40 In-Place Masonry Shear Tests

See Appendix Chapter 1, Uniform Code for Building Conservation.

The bed joints of the outer wythe of the masonry shall be tested in shear by laterally displacing a single brick relative to the adjacent bricks in the same wythe. The head joint opposite the loaded end of the test brick shall be carefully excavated and cleared. The brick adjacent to the loaded end of the test brick shall be carefully removed by sawing or drilling and excavating to provide space for a hydraulic ram and steel loading blocks. Steel blocks, the size of the end of the brick, shall be used on each end of the ram to distribute the load to the brick. The blocks shall not contact the mortar joints. The load shall be applied horizontally, in the plane of the wythe, until either a crack can be seen or slip occurs. The strength of the mortar shall be calculated by dividing the load at the first crack or movement of the test brick by the nominal gross area of the sum of the two bed joints.

Uniform Building Code Standard No. 24-41 Tests of Anchors in Unreinforced Masonry Wall

See Appendix Chapter 1, Uniform Code for Building Conservation.

Existing Anchors

The test apparatus shall be supported on the masonry wall at a minimum distance of the wall thickness from the anchor tested. Existing wall anchors shall be given a preload of 300 pounds prior to establishing a datum for recording elongation. The tension test load reported shall be recorded at 1/8 inch relative movement of the anchor and the adjacent masonry surface. Results of all tests shall be reported. The report shall include the test results as related to the wall thickness and joist orientation.

Combined Shear and Tension Bolts

Combined shear and tension bolts embedded in unreinforced masonry walls shall be tested using a torque calibrated wrench to the following minimum torques:

All nuts shall be installed over malleable iron or plate washers when bearing on wood and heavy cut washers when bearing on steel.

Uniform Building Code Standard No. 24-42 Pointing of Unreinforced Masonry Walls

See Appendix Chapter 1, Uniform Code for Building Conservation.

Pointing

The old mortar should be cut out, by means of a toothing chisel or a special painter's grinder, to a uniform depth of 3/4", or until sound mortar is reached. Care must be taken not to damage the brick edges. All dust and debris must be removed from the joint by brushing, blowing air or rinsing with water.

Mortar mix shall be Type "S" or "N" proportions as called for in the construction specifications. The tuckpointing mortar should be pre-hydrated to reduce excessive shrinkage. The proper pre-hydration process is as follows:

All dry ingredients should be thoroughly mixed. Only enough clean water should be added to the dry mix to produce a damp, workable consistency which will retain its shape when formed into a ball. The mortar should stand in this dampened condition for one to one and one-half hours.

The joints to be tuck-pointed should be dampened, but to ensure a good bond, the brickwork must absorb all surface water. Water should be added to the pre-hydrated mortar to bring it to a workable consistency (somewhat drier than conventional mortar). The mortar should be packed tightly into the joints in thin layers (1/4" maximum). Each layer should become "thumbprint hard" before applying the next layer. The joints should be tooled to match the original profile after the last layer of mortar is "thumbprint hard."

Relaying of Brick

Replacement bricks must match the originals with respect to size, color and texture where exposed. A tuck-pointing toothing chisel should be used to cut out the mortar which surrounds the affected units. Power driven impact tools are not allowed. Once the units are removed, all of the old mortar shall be carefully chiseled out and all dust and debris shall be swept out with a brush.

If used brick is to be relayed, it shall be cleaned of all old mortar. The brick surfaces in the wall shall be dampened before new units are placed, but the masonry should absorb all surface moisture to ensure a good bond. The appropriate surfaces of the surrounding brickwork and the replacement brick should be buttered with mortar. The replacement brick should be centered in the opening and pressed into position.

The excess mortar should be removed with a trowel. Pointing around the replacement brick will help to ensure full head and bed joints. When the mortar becomes "thumbprint hard," the joints shall be tooled to match the original profile.

Glossary of Symbols and Notations

C = Numerical coefficient as specified in Section 2312(d) of the Uniform Building Code

C p = Numerical coefficient as specified in Section 2312(g) of the Uniform Building Code

D = The dimension of the structure, in feet, in a direction parallel to the applied forces

f c = Specified compressive strength of concrete, psi

F p = Lateral forces on a part of the structure and in the direction under consideration

f t = Allowable tensile stress, psi

h n = Height in feet above the base to level n

I = Occupancy Importance Factor as set forth in Table No. 23-K of the Uniform Building Code

S = Numerical coefficient for site-structure resonance

V = The total lateral force or shear at the base

W = The total dead load as defined in Section 2302 of the Uniform Building Code including the partition loading specified in Section 2304(d) of the Uniform Building Code where applicable

W p = The weight of a portion of a structure or nonstructural component

Z = Numerical coefficient dependent upon the zone as determined by Figure No. 1, of Chapter 23 of the Uniform Building Code. All areas in California are classified in Zones 3 or 4. For locations in Zone No. 3, Z = 3/4, For locations in Zone No. 4, Z = 1

PART 2. - TILT-UP CONCRETE WALL BUILDINGS

The purpose of this Part is to promote public safety and welfare by reducing the risk of death or injury that may result from the effects of earthquakes on tilt-up concrete wall buildings designed under the building codes in effect prior to January 1, 1976. Such buildings have been categorized based on past earthquakes, as being potentially hazardous and prone to significant damage, including possible collapse, in a moderate to major earthquake.

The provisions of this Part are minimum standards for structural seismic resistance established primarily to reduce the risk of loss of life or injury on both subject and adjacent properties and will not necessarily prevent loss of life or injury or prevent earthquake damage to an existing building which complies with these standards. The requirement for compliance with these standards does not preclude the utilization, at

the building owner's option, of more extensive strengthening method that might further prevent or limit loss of life or injury or building damage. This Part shall not require existing electrical, plumbing, mechanical or fire safety systems to be altered unless they constitute a hazard to life or property.

This Part provides systematic procedures and standards for identification and classification of tilt-up concrete wall buildings based on the current use of the buildings. Priorities, time periods and standards are also established under which these buildings are required to be structurally analyzed and strengthened for seismic resistance. Where the analysis determines structural deficiencies, this Part requires the buildings to be strengthened or demolished.

The provisions of this Part shall apply to all buildings designed or built under building codes in effect prior to January 1, 1976, which, on the effective date of this Part have tilt-up concrete walls as defined in this Part.

Buildings within the scope of this Part may not be added to or structurally altered or remodeled without first complying with the provisions of this Part unless the Building Official determines that the alteration is minor in nature.

Seismic strengthening in place prior to the effective date of this Part shall be evaluated according to the provisions of this Part and modified to comply if deficient.

For purposes of this Section, the applicable definitions in Sections 2302, 2331, 2502 and 2602 of the 1991 Edition of the Uniform Building Code (UBC) shall also apply.

The rating classifications as exhibited in Table No. 89-H are established and each building within the scope of this Part shall be placed in one such rating classification by the department. The total occupant load as determined by UBC Section 3302(a) of this Code for the entire building plus the occupant load of any adjacent building which interconnects with the subject building or uses the subject building for exiting purposes shall be used to determine the rating classification.

The owner of each building within the scope of this Part shall cause an investigation of the existing construction and a structural analysis to be made of the building by a civil or structural engineer or architect licensed by the State of California, and if the building does not meet the minimum standards specified in this Part, the owner shall cause it to be structurally altered to conform to such standards or cause the building to be demolished.

The owner of the building within the scope of this Part shall comply with the requirements set forth in this Part by submitting to the department for review within two hundred seventy-five (275) days after the service of the order the following:

(a)

A structural analysis, subject to approval by the department within the two hundred seventy-five (275) day time period, which demonstrates that the building meets the minimum requirements of this Part; or

(b)

A structural analysis and plans for the proposed structural alterations of the building necessary to comply with the minimum requirements of this Part; or

(c)

Plans for the demolition of the building.

After plans are submitted and approved by the department, the owner shall obtain a building permit, commence and complete the required construction or demolition within the time limits set forth in Table 89I. These time limits shall begin to run from the date the order is served in accordance with Section 8925.1 and 8925.2 of this Part. Vacating a building shall not be deemed as complying with the requirements of this Part.

8925.1. Service of Order. When the department determines that a building is within the scope of this Part, the owner shall comply with Section 8924 of this Code. If the owner does not comply, the department shall issue an order as provided in Section 8925.2 to the owner of each building with the minimum time periods for service of such orders set forth in Table No. 89-J. The minimum time period for the service of such orders shall be measured from the effective date of this Part.

8925.2. Contents of Order. The order shall be in writing and may be given either by personal delivery thereof to the owner or by deposit in the United States mail in a sealed envelope, postage prepaid, addressed to the owner as shown on the last equalized assessment roll. Service by mail shall be deemed to have been completed at the time of deposit in the post office. The failure of any owner to receive such notice shall not affect in any manner the validity of any of the proceedings taking thereunder. Proof of giving any notice may be made by an affidavit of any employee of the City which shows such service in conformity with this Section. Department administrative action, other correspondence between the City and the building owner or building owner's representative, or other evidence of knowledge of notification shall also be deemed as proof of giving notice.

The order shall specify that the building has been determined by the department to be within the scope of this Part, and therefore, is required to meet the minimum seismic standards of this Part. The order shall specify the rating classification of the building and shall be accompanied by a copy of Section 8924 which sets forth the owner's alternatives and time limits for compliance.

8925.3. Appeal from Order. The owner of the building may appeal the department's determination that the building is within the scope of this Part to the Arcadia Building Code Appeals Board. Such appeal shall be filed with the building official within thirty (30) days of the service date of the order described in Section 8925.2. Such appeal shall be made in writing setting forth clearly and concisely the reasons for appeal. Each appeal shall be accompanied by a filing fee as set forth by resolution of the City Council.

8925.4. Recordation. At the time that the department serves the aforementioned order, the department shall file with the office of the County Recorder a certificate stating that the subject building is within the scope of Part 2 - "Earthquake Hazard Reduction in Existing Tilt-up Concrete Wall Buildings" of this Code. The certificate shall also state that the owner thereof has been ordered to structurally analyze the building and to structurally alter or demolish it when the department determines the building is not in compliance with Part 2 of this Code.

ate stating that the subject building is within the scope of Part 2 - "Earthquake Hazard Reduction in Existing Tilt-up Concrete Wall Buildings" of this Code. The certificate shall also state that the owner thereof has been ordered to structurally analyze the building and to structurally alter or demolish it when the department determines the building is not in compliance with Part 2 of this Code.

If the building is either demolished, found not to be within the scope of this Part or is structurally capable of resisting minimum seismic forces required by this Part as a result of structural alterations or an analysis, the department shall file with the office of the County Recorder a Certificate terminating the status of the subject building as being classified within the scope of Part 2 "Earthquake Hazard Reduction in Existing Tilt-up Concrete Wall Buildings" of this Code.

8925.5. Enforcement. If the owner of the subject building fails to comply with any order issued by the department pursuant to this Part within any of the time limits set forth in Section 8924, or within any additional time limits as may have been granted by the Board, the department may order that the building be vacated and subsequently ordered to be demolished in accordance with the provisions of Section 8924 of this Code. The Building Official shall have the authority to grant two one (1) year extensions in cases of extreme hardship.

8926.1. Wall Panel Anchorage. Concrete walls shall be anchored to all floors and roofs which 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 a horizontal force equal to thirty percent (30%) of the tributary wall weight for all buildings and forty-five percent (45%) of the tributary wall weight for essential buildings, or a minimum force of two hundred (200) pounds per linear foot of wall, whichever is greater. The required anchorage shall be based on the tributary wall panel assuming simple supports between floor and roof or between floor and floor.

EXCEPTION. Alternative design may be approved by the Building Official when justified by well established principles of mechanics.

8926.2. Special Requirements for Anchors. Wall anchors shall be provided to resist out-of-plane forces, independent of existing shear anchors. The wall anchor systems shall be capable of developing yield in the body of the anchor or the system without inducing brittle failure to the concrete to which the anchors are attached.

EXCEPTION. Existing cast-in-place shear anchors may 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 while being acted upon by the maximum tension force due to earthquake. Criteria for analysis and testing shall be determined by the Building Official.

Expansion anchors are not allowed without special approval of the Building Official. Attaching the edge of plywood sheathing to steel ledgers is not considered as complying with the positive anchoring requirements of this Code, and attaching the edge of steel decks to steel edges is not considered as providing the positive anchorage of this Code unless testing and/or analysis are performed which establish shear values for the attachment perpendicular to the edge of the deck.

8926.3. Development of Anchor Loads into the Diaphragm. Development of anchor loads into roof and floor diaphragms shall comply with Section 2337(b)9.C. of the UBC.

In wood diaphragms, anchorage shall not be accomplished by use of toe nails or nails subject to withdraw, nor shall wood ledgers, top plates or framing be used in cross-grain bending or cross-grain tension. The continuous ties required by Section 2337(b)9.C. of the UBC shall be 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.

At reentrant corners, continuity collectors may be required for existing return walls not designed as shear walls, to develop into the diaphragm a force equal to the lesser of the rocking or shear capacity of the diaphragm. Shear anchors for the return wall shall be commensurate with the collector force. If a truss or beam other than rafters or purlins is supported by the return wall, an independent secondary column is required to support the roof or floor members whenever rocking or shear capacity of the return wall is governing.

8926.4. Girder Anchorage at Support. In addition to the anchorage required per Section 8926.1. girder to pilaster connections shall be verified for the tributary wall anchoring load per Section 8926.1 of this Code, considering the wall as a two-day slab. Adequacy of existing lateral confinement of vertical girder anchor at the top of the pilasters shall be verified per Section 2607(k)3.D. of the UBC. If the confinement is inadequate, additional exterior confinement shall be provided. A continuous load path from the pilaster, through the girder and to the diaphragm shall be verified.

EXCEPTION. The requirement for additional confinement and/or adequate strength of existing girder anchor bolts at the top of the pilaster may be waived if the girder is anchored directly to the walls immediately adjacent to the pilaster, or to the pilaster, for the total lateral force such that the existing girder anchor bolts are by-passed without causing shear failure at the top of the pilaster.

8926.5. Crack and Damage Repairs, Evaluation of Existing Structural Alterations.

The engineer shall report any observed structural conditions and structural damage that have imminent life safety effects on the buildings and recommend repairs. Evaluations and repairs shall be reviewed and approved by the department.

The engineer shall also evaluate the effects of alterations such as openings cut in existing wall panels without a permit, that may present immediate life safety hazard and correct when necessary.

8926.6. Miscellaneous. Existing mezzanines relying on the tilt-up 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 Section 8926.1, 8926.2 and 8926.3.

EXCEPTION. Existing mezzanines that have independent lateral and vertical support need not be anchored to the walls.

Existing interior masonry or concrete walls not designed as shear walls, that extend to the floor above or to the roof diaphragm shall also be anchored for out-of-plane forces per Section 8926.1, 8926.2 and 8926.3 of this Code. In the in-plane direction, the walls may be isolated or shall be developed into the diaphragm for a lateral force equal to the lesser of the rocking or shear capacity of the wall, or the tributary shear but not exceeding the diaphragm capacity.

All materials permitted by this Code, including their appropriate allowable stresses and those existing configurations of material specified in Part 1 of this Code, may be utilized to meet the requirements of this Part.

Every building within the scope of this Part which has been analyzed to demonstrate compliance or structurally altered to comply with the minimum earthquake standards in this Part shall be maintained in conformity with the requirements of this Part in effect at the time of such analysis or structural alteration.

Subject to certain changes and amendments as hereinafter set forth in this Chapter, the City Council hereby adopts, by reference, as the residential building regulations for the City, the 2025 Edition of the California Residential Code (California Code of Regulations, Title 24), including Chapter 1. The Code shall govern, regulate and control all of the activities therein referred to and the same is made a part of this Chapter as though set forth in this Chapter in full.

One (1) copy of said Code is on file in the office of the Building Official for use and examination by the public.

(Added by Ord. 2279 adopted 12-7-10; Ord. No. 2312, § 11, 12-3-13; Ord. No. 2342, § 9, 12-6-16; Ord. No. 2366, § 8, 12-17-19; Ord. No. 2394, § 8, 11-15-22; Ord. No. 2408, § 8, 11-18-25)