811.1.1 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 unreinforced masonry bearing wall buildings constructed before 1934. Such buildings have been widely recognized for their sustaining of life hazardous damage as a result of partial or complete collapse during past moderate to strong earthquakes.
The provisions of this chapter are minimum standards for structural seismic resistance established primarily to reduce the risk of life loss or injury and will not necessarily prevent loss of life or injury or prevent earthquake damage to an existing building which complies with these standards. This chapter shall not require existing electrical, plumbing, mechanical or fire safety systems to be altered unless they constitute a hazard to life or property.
This chapter provides systematic procedures and standards for identification and classification of unreinforced masonry bearing wall buildings based on their present use. Priorities, time periods and standards are also established under which these buildings are required to be structurally analyzed and anchored. Where the analysis determines deficiencies, this chapter requires the building to be strengthened or demolished.
Portions of the State Historical Building Code (SHBC) established under Part 8, Title 24 of the California Administrative Code are included in this chapter.
811.1.2 SCOPE.
The provisions of this chapter shall apply to all buildings constructed or under construction prior to March 10, 1933, or for which a building permit was issued prior to March 10, 1933, which on the effective date of this chapter have unreinforced masonry bearing walls as defined herein.
EXCEPTION: This chapter shall not apply to detached one or two family dwellings and detached apartment houses containing fewer than five dwelling units and used solely for residential purposes.
811.1.3 DEFINITIONS.
For purposes of this chapter, the applicable definitions in Sections 2302 and 2312 of the Uniform Building Code and the following shall apply:
ESSENTIAL BUILDING. Any building housing a hospital or other medical facility having surgery or emergency treatment areas, fire or police stations, municipal government disaster operation and communication centers.
HIGH-RISK BUILDING. Any building not classified an essential building having an occupant load as determined by Section 3301 of the Uniform Building Code of one hundred (100) occupants or more.
EXCEPTION: A high-risk building shall not include the following:
A) Any building having exterior walls braced with masonry cross walls or wood frame cross walls spaced less than forty feet (40) feet apart in each story. Cross walls shall be full story height with a minimum length of one-and-one-half (1-1/2) times the story height.
B) Any building used for its intended purpose as determined by the department for less than twenty (20) hours per week.
HISTORICAL BUILDING. Any building designated as a historical building by an appropriate federal, state, or city jurisdiction.
LOW-RISK BUILDING. Any building not classified an essential building having an occupant load as determined by Section 3301 of the Uniform Building Code of less than twenty (20) occupants.
MEDIUM-RISK BUILDING. Any building not classified as a high-risk building or an essential building having an occupant load as determined by Subsection 3301(a) of the Uniform Building Codes of twenty (20) occupants or more.
UNREINFORCED MASONRY BEARING WALL. A masonry wall having all of the following characteristics:
1) Provides the vertical support for a floor or roof.
2) The total superimposed load is over one hundred (100) pounds per linear foot.
3) The area of reinforcing steel is less than fifty (50) percent of that required by subsection 2417(j) of the Uniform Building Code.
811.1.4 RATING CLASSIFICATIONS.
The rating classifications as exhibited in Table No. 11-A below are hereby established and each building within the scope of this chapter shall be placed in one such rating classification by the city. The total occupant load of the entire building as determined by Subsection 3301(a) of the Uniform Building Code shall be used to determine the rating classifications.
EXCEPTION: For the purpose of this chapter, portions of buildings constructed to act independently when resisting seismic forces may be placed in separate rating classifications.
811.1.5 GENERAL REQUIREMENTS.
(Amended by O-3279)
The owner of each building within the scope of this chapter shall cause 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 earthquake standards specified in this chapter, the owner shall cause it to be structurally altered to conform to such standards or cause the building to be demolished.
The owner of a building within the scope of this chapter shall comply with the requirements set forth above by submitting to the city for review within the stated time limits:
a) Within two hundred seventy (270) days after the service of the order, a structural analysis. Such analysis, which is subject to approval by the city, 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, a structural analysis and plans for the proposed structural alterations of the building necessary to comply to the minimum requirements of this 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 811.1.8, or,
d) Within two hundred seventy (270) days after the service of the order, plans for the demolition of the building.
After plans are submitted and approved by the city, the owner shall obtain a building permit, commence and complete the required construction or demolition within the time limits set forth in Table No. 11-B below. These time limits shall begin to run from the date the order is served in accordance with Section 811.1.6.
Owners electing to comply with Subsection (c) of this section are also required to comply with Subsection (b) or (d) of this section, provided, however, that the two hundred seventy (270) day period provided for in such Subsections (b) and (d) and the time limits for obtaining a building permit, commencing construction and completing construction for complete structural alterations or building demolition set forth in Table No. 11-B below shall be extended in accordance with Table No. 11-C below. Each such extended time limit, except the time limit for commencing construction, shall begin to run from the date the order is served in accordance with Section 811.1.6. The time limit for commencing construction shall run from the date the building permit is issued.
811.1.6 ADMINISTRATION.
a) Service of Order. The city shall issue an order, as provided in Paragraph (b) below, to the owner of each building within the scope of this chapter in accordance with the minimum time periods for service of such orders set forth in Table No. 11-C below. The minimum time period for the service of such orders shall be measured from the date that the City Council adopts a funding program for the affected property owners. The city shall, upon receipt of a written request from the owner, order a building to comply with this chapter prior to the normal service date for such building set forth in this section.
b) Contents of Order. 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 city 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 811.1.5, which sets forth the owner’s alternatives and time limits for compliance.
c) Appeal From Order. The owner or person in charge or control of the building may appeal the city’s initial determination that the building is within the scope of this to the Board of Appeals. Such appeal shall be filed with the Board within sixty (60) days from the service date of the order described in this Section 811.1.6. Any such appeal shall be decided by the Board no later than sixty (60) days after the date that the appeal is filed. Such appeal shall be made in writing upon appropriate forms provided therefor by the city, and the grounds thereof shall be stated clearly and concisely. Each appeal shall be accompanied by a filing fee as set forth in Paragraph (f) of this section.
Appeals or request for slight modifications from any other determination, orders or actions by the city pursuant to this chapter shall be made in accordance with the procedures established in Section 106 of the Uniform Building Code.
d) Recordation. At the time that the city serves the aforementioned order, the city shall file with the Office of the County Recorder a certificate stating that the subject building is within the scope of Earthquake Hazard Reduction in Existing Buildings of the Torrance Municipal 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 where compliance is not exhibited.
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 city 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 Earthquake Hazard Reduction in Existing Buildings of the Torrance Municipal Code.
e) Enforcement. If the owner or other person in charge or control of the subject building fails to comply with any order issued by the city pursuant to this chapter within any of the time limits set forth in Section 811.1.5, the city shall order that the entire building be vacated and that the building 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 such additional time as may have been granted by the Board, the Building and Safety Director may order its demolition in accordance with the provision of this code.
f) Appellate Fee; Building & Safety Director.
1) The fee for an appeal of the Building and Safety Director’s action to the Board of Appeals shall be Seventy-Five Dollars ($75.00).*
2) The fee for an appeal to the City Council of any action of the Board of Appeals shall be pursuant to the provisions of Section 11.5.2 of this Code.
*fees increased/decreased pursuant to Subsection 81.2.2(f).
811.1.7 HISTORICAL BUILDINGS.
a) General. The standards and procedures established by this chapter shall apply in all aspects to a historical building except that as a means to preserve original architectural elements and facilitate restoration, a historical building may, in addition, comply with the special provisions set forth in this section.
b) Unburned Clay Masonry or Adobe. Existing or re-erected walls of adobe construction shall conform to the following:
1) Unreinforced adobe masonry walls shall not exceed a height or height-to-thickness ratio of five (5) for exterior bearing walls and must be provided with a reinforced bond beam at the top, interconnecting all walls. Minimum beam depth shall be six (6) inches and a minimum width of eight (8) inches less than the wall width.
Minimum wall thickness shall be eighteen (18) inches for exterior bearing walls and ten (10) inches for adobe partitions. No adobe structure shall exceed one (1) story in height unless the historic evidence indicates a two-story height. In such cases the height-to-thickness ratio shall be the same as above for the first floor based on the total two-story height, and the second floor wall thickness shall not exceed the ratio five (5) by more than twenty (20) percent. Bond beams shall be provided at the roof and second floor levels.
2) Foundation footing shall be reinforced concrete under newly reconstructed walls and shall be fifty (50) percent wider than the wall above, soil conditions permitting, except that the foundation wall may be four (4) inches less in width than the wall above if a rock, burned brick, or stabilized adobe facing is necessary to provide authenticity.
3) New or existing unstabilized brick and adobe brick masonry shall have an average compressive strength of two hundred twenty-five (225) pounds per square inch when tested in accordance with ASTM designation C 67. One sample out of five (5) may have a compressive strength of not less than one hundred eighty-eight (188) pounds per square inch. Unstabilized brick may be used where existing bricks are unstabilized and where the building is not susceptible to flooding conditions or direct exposure. Adobe may be allowed a maximum value of three (3) pounds per square inch for shear with no increase for lateral forces.
4) Mortar may be of the same soil composition and stabilization as the brick in lieu of cement mortar.
5) Nominal tension stresses due to seismic forces normal to the wall may be neglected if the wall meets thickness requirements and shear values allowed by this subsection.
c) Archaic Materials. Allowable stresses for archaic materials not specified in this code shall be based on substantiating research data or engineering judgment, subject to the department’s satisfaction.
d) Alternative Materials and SHBC Advisory Review. Alternative materials, design or method of construction will be considered as set forth in Section 811.1.9. In addition, when a request for an alternative proposed design, material or method of construction is being considered, the city may file written request for opinion to the State Historical Building Code Advisory Board for its consideration, advice or findings in accordance with the SHBC.
811.1.8 ANALYSIS AND DESIGN.
a) General. Every structure within the scope of this chapter shall be analyzed and constructed to resist minimum total lateral seismic forces assumed to act nonconcurrently in the direction of each of the main axis of the structure in accordance with the following equation:
|
V = IKCSW |
(811-1) |
The value of IKCS need exceed the values set forth in Table No. 11-D based on the applicable rating classification of the building.
b) Lateral Forces on Elements and Structures. Parts or portions of structures shall be analyzed and designed for lateral loads in accordance with Subsection 811.1.8(a) and 2312(e) of the Uniform Building Code but not less than the value from the following equation:
|
Fp = ICpSWp |
(811-2) |
For the provisions of this subsection, the product of IS need not exceed the values as set forth in Table No. 11-E below.
EXCEPTION: Unreinforced masonry walls in buildings and having a Rating Classification of one (1) may be analyzed in accordance with Section 811.1.9.
The value of Cp need not exceed the values set forth in Table 11-F below.
c) Anchorage and Interconnection. Anchorage and interconnection of all parts, portions and elements of the structure shall be analyzed and designed for lateral forces in accordance with Table No. 11-F below of this chapter and the equation Fp = ICpSWp as modified by Table No. 11-E below. Minimum anchorage of masonry walls to each floor or roof shall resist a minimum force of two hundred (200) pounds per linear foot acting normal to the wall at the level of the floor or roof.
d) Level of Required Repair. Alteration and repairs required to meet the provisions of this chapter shall comply with all other applicable requirements of this code unless specifically provided for in this chapter.
e) Required Analysis.
1) General. Except as modified herein, the analysis and design relating to the structural alteration of existing structures within the scope of this chapter shall be in accordance with the analysis specified in Division 23 of the Uniform Building Code, 198 Edition, or as it may be amended from time to time.
2) Continuous Stress Path. A complete, continuous stress path from every part or portion of the structure to the ground shall be provided for the required horizontal forces.
3) Position Connections. All parts, portions or elements of the structure shall be interconnected by positive means.
f) Analysis Procedure.
1) General. Stresses in materials and existing construction utilized to transfer seismic forces from the ground to parts or portions of the structure shall conform to those permitted by the Uniform Building Code and those materials and types of construction specified in Section 811.1.9
EXCEPTION: The Building Official has the authority to accept alternate methods of retrofit in accordance with Section 81.2.1(h).
2) Connections. Materials and connections used for interconnection of parts and portions of the structure shall conform to the Uniform Building Code. Nails may be used as part of an approved connector.
3) Unreinforced Masonry Walls. Except as modified herein, unreinforced masonry walls shall be analyzed as specified in Sections 2416, 2417 and 2419 and to withstand all vertical loads as specified in Division 23 of the Uniform Building Code in addition to the seismic forces required by this chapter. The fifty (50) percent increase in the seismic force factor for shear walls as specified in Table No. 24-H below of the Uniform Building Code may be omitted in the computation of seismic loads to existing shear walls.
No allowable tension stress will be permitted in unreinforced masonry walls. Walls not capable of resisting the required design forces specified in this chapter shall be strengthened or shall be removed and replaced.
EXCEPTIONS:
1) Unreinforced masonry walls in buildings not classified as a Rating Classification I pursuant to Table No. 11-A below may be analyzed in accordance with Section 811.1.9
2) 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.
g) Combination of Vertical and Seismic Forces.
1) New Materials. All new materials introduced into the structure to meet the requirements of this section which are subject to combined vertical and horizontal forces shall comply with Subsection 2303(f) of the Uniform Building Code.
2) Existing Materials. When stresses in existing lateral force-resisting elements are due to a combination of dead loads plus seismic loads, the allowable working stress specified in the Uniform Building Code may be increased one hundred (100) percent. However, no increase will be permitted in the stresses allowed in Section 811.1.9 and the stresses in members due only to seismic and dead loads shall not exceed the values permitted by Subsection 2303(d) of the Uniform Building Code.
3) Allowable reduction of bending stress by vertical load. In calculating tensile fiber stress due to seismic forces required by this chapter, the maximum tensile fiber stress may be reduced by the full direct stress due to vertical dead loads.
811.1.9 MATERIALS OF CONSTRUCTION.
a) General. All materials permitted by the Uniform Building Code, including their appropriate allowable stresses and those existing configurations of materials specified herein, may be utilized to meet the requirements of this chapter.
b) Existing Materials.
1) Unreinforced masonry walls. Unreinforced masonry walls analyzed in accordance with this section may provide vertical support for roof and floor construction and resistance to lateral loads. The bonding of such walls shall be as specified in Subsection 2411 (b)1 of the Uniform Building Code.
Tension stresses due to seismic forces normal to the wall may be neglected if the wall does not exceed the height or length-to-thickness ratio and the in-plane shear stresses due to seismic loads as set forth in Table No. 11-G below.
If the wall height-thickness ratio exceeds the specified limits, the wall may be supported by vertical bracing members designed in accordance with Chapter 23 of the Uniform Building Code. The deflection of such bracing members at design loads shall not exceed one tenth (1/10) of the wall thickness.
EXCEPTION: The wall may be supported by flexible vertical bracing members designed in accordance with Subsection 811.1.8(b) if the deflection of design loads is not less than one-quarter (1/4) nor more than one third (1/3) of the wall thickness.
All 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.
The wall height may be measured vertically to bracing elements other than a floor or roof. Spacing of the bracing elements and wall anchors shall not exceed six (6) feet. Bracing elements shall be detailed to minimize the horizontal displacement of the wall by components of vertical displacement of the floor or roof.
2) Existing roof, floors, walls, footings and wood framing. Existing materials, including wood shear walls utilized in the described configuration, may be used as part of the lateral load resisting system, provided that the stresses in these materials do not exceed the values shown in Table No. 11-H below.
c) Strengthening of Existing Materials. New materials, including wood shear walls, may be utilized to strengthen portions of the existing seismic resisting system in the described configurations, provided that the stresses do not exceed the values shown in Table No. 11-I below.
d) Alternate Materials. Alternate materials, designs and methods of construction may be approved by the city in accordance with the provisions of Section 10 of the Uniform Building Code.
e) Minimum Acceptable Quality of Existing Unreinforced Masonry Walls.
1) General Provisions. All unreinforced masonry walls utilized to carry vertical loads and seismic forces parallel and perpendicular to the wall plane shall be tested as specified in this subsection. All masonry quality shall equal or exceed the minimum standards established herein and shall be removed and replaced by new materials. Alternate methods of testing may be approved by the city. The quality of mortar in all masonry walls shall be determined by performing in-place shear tests or by testing eight (8) inch diameter cores. Alternative methods of testing may be approved by the city. Nothing shall prevent pointing with mortar of all the masonry wall joints before the tests are first made. Prior to any pointing, the mortar joints must be raked and cleaned to remove loose and deteriorated mortar. Mortar for pointing shall be Type S or N except masonry cements shall not be used. All preparation and mortar pointing shall be done under the continuous inspection of a registered deputy building inspector. At the conclusion of the inspection, the inspector shall submit a written report to the licensed engineer or architect responsible for the seismic analysis for the building setting for the result of the work inspected. Such report shall be submitted to the city for approval as part of the structural analysis. All testing shall be performed in accordance with the requirements specified in this subsection by a testing agency approved by the city. An accurate record of all such tests and their location in the building shall be recorded and these results shall be submitted to the city for approval as part of the structural analysis.
2) Number and Location of Tests. The minimum number of tests shall be two (2) per wall or line of wall elements resisting a common force, or one per one thousand five hundred (1, 00) square feet of wall surface, with a minimum of eight (8) tests in any case. The exact test or core location shall be determined at the building site by the licensed engineer or architect responsible for the seismic analysis of the subject building.
3) In-place Shear Tests. 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 that wythe. The opposite head joint of the brick to be tested shall be removed and cleaned prior to testing. The minimum quality mortar in eighty (80) percent of the shear tests shall not be less than the total of thirty (30) psi plus the axial stress in the wall at the point of the test. The shear stress shall be based on the gross area of both bed joints and shall be that at which movement of the brick is first observed.
4) Core Tests. A minimum number of mortar test specimens equal to the number required cores shall be prepared from the cores and leveled as specified herein. The mortar joint of the outer wythe of the masonry core shall be tested in shear by placing the circular core section in a compression testing machine with the mortar bed joint rotated fifteen (15) degrees from the axis of the applied load. The mortar joint tested in shear shall have an average ultimate stress of twenty (20) psi braced on the gross area. The average shall be obtained from the total number of cores made. If test specimens cannot be made from cores taken then the shear value shall be reported as zero (0).
f) Testing of Shear Bolts. One fourth (1/4) of all new shear bolts and dowels embedded in unreinforced masonry walls shall be tested by a registered deputy building inspector using a torque calibrated wrench to the following minimum torques:
1/2-inch-diameter bolts or dowels - 40 foot lbs.
5/8-inch-diameter bolts or dowels - 50 foot lbs.
3/4-inch-diameter bolts or dowels - 60 foot lbs.
No bolts exceeding three-fourths (3/4) inch shall be used. All nuts shall be installed over malleable iron or plate washers when bearing on wood and heavy cut washers when bearing on steel.
g) Determination of Allowable Stresses for Design Methods Based on Test Results.
1) Design Shear Values. Designs seismic in-plane shear stresses shall be substantiated by tests performed as specified in Subsection 811.1.9(e) 3 and 4.
Design stresses shall be related to test results obtained in accordance with Table No. 11-J below. Intermediate values between three (3) and ten (10) psi may be interpolated.
2) Design Compression and Tension Values. Compression stresses for unreinforced masonry having a minimum design shear value of three (3) psi shall not exceed one hundred (100) psi. Design tension values for unreinforced masonry shall not be permitted.
h) Five (5) percent for the existing rod anchors utilized as all or part of the required wall anchors shall be tested in pullout by an approved testing laboratory. The number 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. The test apparatus shall be supported on the masonry wall at a minimum distance of the wall thickness from the anchor tested. The rod anchor shall be given a preload of three hundred (300) pounds prior to establishing a datum for recording elongation. The tension test load reported shall be recorded at one-half (1/2) 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. The allowable resistance value of the existing anchors shall be forty (40) percent of the average of those tested anchors having the same wall thickness and joist orientation.
i) Qualification tests for devices used for wall anchorage shall be tested with the entire tension load carried on the enlarged head at the exterior face of the wall. Bond on the part of the device between the enlarged head and the interior wall face shall be eliminated for the qualification tests. The resistance value assigned the device shall be twenty (20) percent of the average of the ultimate loads.
811.1.10 INFORMATION REQUIRED ON PLANS.
a) General. In addition to the seismic analysis required elsewhere in this chapter, the licensed engineer or architect responsible for the seismic analysis of the building shall determine and record the information required by this section on the approved plans.
b) Construction Details. The following requirements with appropriate construction details shall be made part of the approved plans:
1) All unreinforced masonry walls shall be anchored at the roof level by tension bolts through the wall as specified in Table No. I or by approved equipment at a maximum anchor spacing of six (6) feet. Anchors installed in accordance with Section 2310 of the Uniform Building Code shall be accepted as conforming to this requirement.
All unreinforced masonry walls shall be anchored at all floors with tension bolts through the wall or by existing rod anchors at a maximum anchor spacing of six (6) feet. All existing rod anchors shall be secured to the joists to develop the required forces. The city may require testing to verify the adequacy of the embedded ends of existing rod anchors. Tests when required shall conform to Subsection 811.1.9(h).
When access to the exterior face of the masonry wall is prevented by proximity of an existing building, wall anchors conforming to items and 6 in Table No. 11-I below may be used.
Alternate devices to be used in lieu of tension bolts for masonry wall anchorage shall be tested as specified in Subsection 811.1.9(i).
2) Diaphragm chord stresses of horizontal diaphragms shall be developed in existing materials or by addition of new materials.
3) Where trusses and beams other than rafters or joists are supported on masonry, ledges or columns shall be installed to support vertical loads of the roof or floor members.
4) Parapets and exterior wall appendages not capable of resisting the forces specified in this chapter shall be removed, stabilized or braced to ensure that the parapets and appendages remain in their original position.
5) All deteriorated mortar joints in unreinforced masonry walls shall be pointed with Type S or N mortar. 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 the continuous inspection of a registered deputy building inspector certified to inspect masonry or concrete. At the conclusion of the project, the inspector shall submit a written report to the city setting forth the portion of work inspected.
6) Repair details of any cracked or damaged unreinforced masonry wall required to resist forces specified in this chapter.
c) Existing Construction. The following existing construction information shall be made part of the approved plans:
1) The type and dimensions of existing walls and the size and spacing of floor and roof members.
2) The extent and type of existing wall anchorage to floors and roof.
3) The extent and type of parapet corrections which were performed in accordance with Section 2310 of the Uniform Building Code.
4) Accurately dimensioned floor plans and masonry wall elevations showing dimensioned openings, piers, wall thickness and heights.
5) The location of cracks or damaged portions of unreinforced masonry walls requiring repairs.
6) The type of interior wall surfaces and if reinstalling or anchoring of ceiling plaster is necessary.
7) The general condition of the mortar joints and if the joints need pointing.
|
Type of Building |
Classification |
|---|---|
|
Essential building |
I |
|
High-risk building |
II |
|
Medium-risk building |
III |
|
Low-risk building |
IV |
|
Required Action by Owner |
Complete Building Permit Within |
Commence Construction Within |
Complete Construction Within |
|---|---|---|---|
|
Complete structural alteration or building demolition |
14 months |
180 days* |
3 years |
|
Wall anchor installation |
180 days |
270 days |
1 year |
* Measured from date of building permit issuance.
|
Rating Classification |
Occupant Load |
Extension of Time if Wall Anchors Are Installed |
Minimum Time Period for Service of Order |
|---|---|---|---|
|
I (Highest Priority) |
Any |
1 year |
0 |
|
II |
100 or more |
1 year |
90 days |
|
III |
100 or more |
1 year |
1 year |
|
|
More than 50 but less than 100 |
1 year |
2 years |
|
|
More than 19 but less than 51 |
1 year |
3 years |
|
IV (Lowest Priority) |
Less than 20 |
1 year |
4 years |
|
Rating Classification |
IKCS |
|---|---|
|
I |
0.186 |
|
II |
0.133 |
|
III & IV |
0.100 |
|
Rating Classification |
IS |
|---|---|
|
I |
1.50 |
|
II |
1.00 |
|
III & IV |
0.75 |
|
Parts 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 ten (10) feet in height; masonry fences over six (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 part of a building; towers, tanks, towers and tanks plus contents, racks over eight (8) feet three (3) inches in height plus contents, chimneys, smokestacks and penthouses |
Any direction |
0.202,4 |
|
When connected to or part of a building; rigid and rigidly mounted equipment and machinery are required for continued operation of essential occupancies5 |
Any horizontal direction |
0.203 |
|
Tanks plus effective contents resting on the ground |
Any direction |
0.12 |
|
Floors and roofs acting as diaphragms |
In the plane of the diaphragm |
0.126 |
|
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 |
Notes:
1See Subsection 811.1.8(b) for use of Cp.
2When located in the upper portion of any building with any h/D ratio of five (5) to one (1) or greater, the value shall be increased by fifty (50) percent.
3For flexible and flexibly 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 or structure in which it is placed.
4The Wp for storage racks shall be the weight of the racks plus contents. The value of Cp for racks over two (2) storage support levels in height shall be 0.16 for the levels below the top two (2) levels.
5The design of the equipment and machinery and their anchorage is an integral part of the design and specification of such equipment or machinery. The structure to which the equipment or machinery is mounted shall be capable of resisting the anchorage forces (see also Subsection 2312(k) of the Uniform Building Code).
6Floor and roofs acting as diaphragms shall be designed for a minimum force resulting from a Cp of .12 applied to Wp unless a greater force results from the distribution of lateral forces in accordance with Subsection 2312(e) of the Uniform Building Code.
|
|
Buildings with Crosswalks as Defined by Section 811.1.3 |
All Other Buildings |
|---|---|---|
|
Walls of one (1) story buildings |
16 |
13 |
|
First-story wall of multi-story buildings |
16 |
15 |
|
Walls to top story of multi-story buildings |
14 |
9 |
|
All other walls |
16 |
13 |
1 Minimum quality mortar shall be determined by laboratory testing in accordance with Subsection 811.1.9(c).
2 Table No. 11-G is not applicable to buildings of Rating Classification I. Walls of buildings within Rating Classification I shall be analyzed in accordance with Subsection 911.1.8(f).
TABLE NO. 11-H
VALUES FOR EXISTING MATERIALS
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Existing Materials or Configuration of Materials |
Allowable Values |
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|---|---|---|---|
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1. |
Horizontal Diaphragms |
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a. |
Roofs with straight sheathing and roofing applied directly to the sheathing |
100 pounds per foot for seismic shear |
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b. |
Roofs with diagonal sheathing and roofing applied directly to the sheathing |
400 pounds per foot for seismic shear |
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c. |
Floors with straight tongue-and-groove sheathing |
150 pounds per foot for seismic shear |
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d. |
Floors with straight sheathing and finished wood flooring |
300 pounds per foot for seismic shear |
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e. |
Floors with diagonal sheathing and finished wood flooring |
450 pounds per foot for seismic shear |
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f. |
Floors or roof with straight sheathing and plaster applied to the joist or rafters2 |
Adds 50 pounds per foot to the allowable values for items 1(a) and 1(c) |
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2. |
Shear walls |
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Wood stud walls with lath and plaster |
100 pounds per foot each side for seismic shear |
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3. |
Plain concrete footings |
F = 1,500 psi unless otherwise shown by tests |
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4. |
Douglas Fir Wood |
Allowable stress same as No. 1 D.F.3 |
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5. |
Reinforcing Steel |
f = 18,000 pounds per square inch maximum3 |
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6. |
Structural Steel |
f = 20,000 pounds per square inch maximum3 |
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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 city.
3 Stresses given may be increased for combinations of loads as specified in Subsection 811.1.8(g)2.
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New Materials or Configuration of Materials1 |
Allowable Values |
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|---|---|---|---|
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1. |
Horizontal Diaphragms |
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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 Table No. 25-J of the Uniform Building Code for blocked diaphragms |
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2. |
Shear walls |
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a. |
Plywood sheathing applied directly over existing studs. No value shall be given to plywood applied over existing plaster or wood sheathing |
Same as values specified in Table 25-K of the Uniform Building Code for shear walls. |
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b. |
Drywall or plaster applied directly over existing wood studs |
75 percent of the values specified in Table No. 47-I of the Uniform Building Code |
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c. |
Drywall or plaster applied to plywood sheathing over existing wood studs |
33 1/3 percent of the values specified in Table No. 47-I of the Uniform Building Code |
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3. |
Shear Bolts. |
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Shear bolts and shear dowels embedded a minimum of eight (8) inches into unreinforced masonry walls. Bolt centered on a two and one-half (2-1/2) inch diameter hole with dry pack or nonshrink grout around the circumference of bolt or dowel1,3 |
100 percent of the values for plain masonry specified in Table No. 24-G of the Uniform Building Code. No values larger than these given for three-fourths (3/4) inch bolts shall be used. |
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4. |
TENSION BOLTS |
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Tension bolts and tension dowels extending entirely through unreinforced masonry walls secured with bearing plates on far side of wall with at least thirty (30) square inches of area2,3 |
1,200 pounds per bolt or dowel |
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5. |
WALL ANCHORS |
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a. |
Bolts extending to the exterior face of the wall with two and one-half (2-1/2) inch round plate under the head. Install as specified for shear bolts. Spaced not closer than twelve (12) inches on centers1,2,3 |
600 pounds per bolt |
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b. |
Bolts or dowels extending to the exterior face of the wall with a two and one-half (2-1/2) inch round plate under the head and drill at an angle of twenty-two and one-half (22-1/2) degrees to the horizontal. Installed as specified for shear bolts1,2,3 |
1,200 lbs per bolt or dowel |
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6. |
INFILLED WALLS |
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Reinforced masonry infilled openings in existing unreinforced masonry walls with keys or dowels to match reinforcing |
Same as values specified for unreinforced masonry walls |
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7. |
Reinforced Masonry |
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Masonry piers and walls reinforced per Section 2418 of the Uniform Building Code |
Same as values specified in Table No. 24-B of the Uniform Building Code |
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8. |
Reinforced Concrete |
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Concrete footings, walls and piers reinforced as specified in Chapter 26 and designed for tributary loads |
Same as values specified in Chapter 26 of the Uniform Building Code |
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9. |
Existing Foundation Loads |
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Foundation loads for structures exhibiting no evidence of settlement |
Calculated existing foundation loads due to maximum dead load plus live load may be increased twenty-five (25) percent for dead load, and may be increased fifty (50) percent for dead load plus seismic load required by this chapter. |
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1 Bolts and dowels to be tested as specified in Subsection 811.1.9(f).
2 Bolts and dowels to be one-half (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.
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80 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 |
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40 plus axial stress |
27 |
7 psi |
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50 plus axial stress |
33 |
5 psi |
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100 plus axial stress or more |
67 or more |
10 psi maximum |
* Allowable shear stress may be increased by addition of ten (10) percent of the axial stress due to the weight of the wall directly above.