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HomeMy WebLinkAboutOrd 1419.2 Burlingame Municipal "Chapter 18.24 18.24.010 Purpose It is found and declared the in the event of a strong or moderate local earthquake, loss of life or serious injury may result from damage or collapse of unreinforced masonry buildings in Burlingame. The purpose of this ordinance is to promote public safety by establishing a set of structural repair standards to be used to strengthen unreinforced masonry buildings and require owners to make their buildings conform to those standards within a reasonable period of time. The provisions of this chapter are minimum standards for structural seismic resistance established primarily to reduce the risk of life loss or injury but will not necessarily prevent loss of life or injury or prevent earthquake damage to an existing building which complies with these standards. This seismic hazard reduction program is consistent with California health and Safety Code sections 19160-19168 and Government Code sections 8875-8878 et sect. 18.24.020 Definitions (a) "Bearing wall" means any wall supporting a floor or roof where the total superimposed load exceeds one hundred (100) pounds per linear foot, or any unreinforced masonry wall supporting its own weight when over six (6) feet in height. (b) "Civil engineer or Structural engineer" means a licensed civil or structural engineer registered by the State of California pursuant to the rules and regulations of Title 16, Chapter 5 of the California Administrative Code. (c) "Occupant Load" means the total maximum number of occupants in the building determined by either 1) Table 33-A of the Uniform Building Code or, 2) the actual maximum number of occupants in the building as certified by the building owner and current tenants. (d) "Story" means that portion of a building included between the upper surface of any floor and the upper surface of the floor next above, except that the topmost story shall be that portion of a building included between the upper surface of the topmost floor and the ceiling or roof above. • masonry means containing -. . partially e followingmateandlessrials thanfifty percent reinforcingof the minimum area of - required by .. Uniform Building Code Section 2407(h)4 Ba I Hollow clay tile Adobe or unburned cl Applicability. All unreinforced masonry buildings identified by the City, except those used exclusively for residential purposes containing five (5) or less living units. 18.24.040 ®caner Notification The owners of unreinfareed masonry buildings determined to be within the scope of this chapter will be notified in writing by the Chief Building inspector according to the schedule set forth in Section 18.24.050(b). (aD Building categories. Three categories of unreinforced masonry buildings are hereby established to prioritize their need for remedial action to reduce potential hazards. 1. High Risk buildings are those which have two or more stories or a maximum occupant load of more than 100 regardless of the number of stories. High Risk buildings also include any structure with an unreinforced masonry parapet wall where the remainder of the building does not contain unreinforced masonry walls. 2. Medium Risk buildings are those one story buildings with a maximum occupant load of 100 or less and are more than 2000 square feet in floor area. 3. Low Risk buildings are one story buildings with a maximum occupant load of less than 10. (b) implementation schedule. The owners of buildings in the three risk categories must take the appropriate actions to comply with the requirements and time schedule set forth in Table A below. The time period for the submission of plans and the completion of construction begin on the date of the notice served upon the owner. The period of time stated for the noticing of owners begins on the effective date of the ordinance adopting this chapter. 0 ! HIGH RISK 90 DAYS' January 1, 1995 MEDIUM RISK 1 YEAR' January 1, 1995 LOW RISK 1 YEAR' January 1, 1995 ki wjq4ji%8 June 30, 1996 When construction is performed for the purpose a€ meeting the requirements of this chapter, the City shall waive as many non -life safety Municipal Cade requirements as possible and reasonable, so as to allow the same use o€ the building as preceding the remedial work. No requirements shall be waived which would allow an increase in the building area ar increase in the area of an existing use or the continuation of an illegal use. Replacement of tenant imgrovements may be included in such waivers. The procedures and engineering standards establishing a minimum level of structural strengthening required for all unreinforced masonry buildings within the scope of this ordinance are set forth in Sections 18.24.080 et sea. of this chapter. The Uniform Code for Building Conservation Appendix Chapter One only, published in 1985 by the International Conference of Building Officials, Whittier, California, with amendments is hereby adopted as a part of this ordinance and all references in Section 18.24.080 et seq. are to that appendix. 18.24.080 Section A102 amended - Scope. Sectian A102 is amended to read °'Sec. A102. The requirements of this chapter shall apply to all buildings containing unreinforced masonry bearing walls. Exceptions This chapter shall not apply to a detached Group R, Division 3 Occixpancy nor to a detached Group R, Division 1 Occupancy containing less than five dwelling units used solely for residential purposes . '° "Sec. A105. (a) General. A historic building may comply with the special provisions set forth in this chapter and the provisions of the State Historical Building Code. (b) Archaic Materials. Allowable stresses for archaic materials not specified in this code shall be based on substantiating research data or engineering judgement with the agproval of the Chief Building Inspector.'° 18.24.110 Section A106 amended - Analysis and Design. Section A106(a) through (d), (f)1, and (g}3 are amended to read as follows: '°Sec. A106.(a) General. Every structure within the scoge 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 axes of the structure in accordance with the following equation: V = ZTKCSw ........................(A1-1) The value of KCS need not exceed but shall not be less than for one story buildings with less than 100 occupants; and need exceed but must not be less than .133 for ane story buildings containing 100 or more occupants and buildings over one story .100 not above grade. The value of 2 and I be as defined in Chapter 23 shall of the equal 1.0. The value of W 1985 Uniform Building Code. shall Section0 amended to real folloys: "Sec. A105. (a) General. A historic building may comply with the special provisions set forth in this chapter and the provisions of the State Historical Building Code. (b) Archaic Materials. Allowable stresses for archaic materials not specified in this code shall be based on substantiating research data or engineering judgement with the agproval of the Chief Building Inspector.'° 18.24.110 Section A106 amended - Analysis and Design. Section A106(a) through (d), (f)1, and (g}3 are amended to read as follows: '°Sec. A106.(a) General. Every structure within the scoge 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 axes of the structure in accordance with the following equation: V = ZTKCSw ........................(A1-1) The value of KCS need not exceed but shall not be less than for one story buildings with less than 100 occupants; and need exceed but must not be less than .133 for ane story buildings containing 100 or more occupants and buildings over one story .100 not above grade. The value of 2 and I be as defined in Chapter 23 shall of the equal 1.0. The value of W 1985 Uniform Building Code. shall Subsection (b} of Section A106 is hereby amended to read: (b} Lateral Forces on Elements of Structures. Parts or portions of buildings shall be analyzed and designed for lateral loads in accordance with Chapter 23 of the 1985 Uniform Building Code but not less than the value from the following equation: Fp - ICpSwp...................... (A1-2 For the provisions of this section, the product of TS shall equal 1.0. The value of Cp shall be in accordance with Table 23-J of the 1985 Uniform Building Code. The value o€ Wp shall be as defined in Chapter 23 of the 1985 Uniform Building Cade. Exception: Unreinforced masonry walls in buildings not required to be designed as an essential facility may be designed in accordance with Section A107. ratio(c) Regulated Elements of Buildings. The elements of buildings required to be analyzed by this chapter include: 1) Height -to - of masonry_ bolts 3) In -plane shear stress; 4) Parapets;stresses floorstiaphragm chords in anciTurage an4- nuercounection. MIMMage ana 17mercollnecrion of all parts, portions and elements of the structure shall be analyzed and designed for lateral forces in accordance with the 1985 Uniform Building .. -code. Masonry walls shall be anchored to all floors and roof to resist a minimum �� - - level of the floor or roof. tf} Required Analysis. 1. General. Except as modified herein, the analysis and design relating to the structural alteration of existing buildings within the scope of this chapter shall be in accordance with the analysis specified in the 1985 Uniform Building Code. In addition the compatibility of the roof diaphragm stiffness with the out -of -plane stability of the unreinforced masonry bearing walls of the story immediately below the roof shall be verified in accordance with the provisions of Section A109. oof diaphragms shall use the h/t values for all other uildings in Table Al -F. OW WININIONIMMU _ • _MVE • forcesto resist 1.0 times the required forces in lieu of the 1.5 factor required by the Building Code. » removed and replaced. i Exceptions: 1. Unreinforced masonry walls in buildings not classified as an essential facility may be analyzed in accordance with Section A107. 2. Unreinforced masonry walls which carry no design loads other than their own weight may be considered veneer if they are adequately anchored to new supporting elements. Substantial changes in wall thickness or stiffness shall be stability, and the wall shall be restrained ... , plane instability by anchorage and bracing to the roof or floor diaphragm in accordance with Section A106 (d)* Exception: Variations in wall stiffness caused by nominal apenings such as windows and doors need not be IV 18o24*112 SectionA107 amended .. - of r r.... follows:Section A107(b), W and (f) are hereby amended to read as follows: x1sting"nTlaterials. 1. Tnreintorceld masonry walls. Unreinforced masonry walls analyzed in accordance with this chapter may provide vertical support for roof and floor construction and resistance to lateral loads. full shoved mortar joints; all head, bed and wall (collar) joints shall be solidly filled with mortar; and the bonding of adjacent wythes of multi-wythe walls shall be as wercent of the wall surface of each face is composed of headers extending not less than four inches into the backing. The distancz 4etween adjacent fullIIIIIlength headers shall not exceed 24 inches either vertically or # • _ a single header toes not extend through the wall, headers from the opposite sides shall overlap at least four inches, or headers from opposite shall be covered with another header course overlapping the header below as veneer. The veneer wythe shall not be included in the effective thickness used to calculate the heightIIIIIIto�thickness ratio and the shear capacity of the wall. rieglected it the wall does not exceed the height�to�thickness ratijf. set forth in Table AlIIIIIF and the inI~p1ane shear stresses due to seismicloads • • - wall • f supportedthickness ratio exceeds the specified limit, the wall may be requirements of the 1985 Uniform Building Code. The deflection of such bracing members at design loads shall not exceed one�tenth of the wall thickness. 1111111 Jill 1111 1111 lill Jill 1111 111 Jill 11:1 1111111 if the deflection at design loads is not less than one-quarter nor more than one-third of the wall thickness at the level under 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 the unsupported height of the wall nor ten feet, whichever is less. The wall height may be measured vertically to bracing elements anchors shall not exceed six teet. Bracing elements - fetailed to minimize the horizontal displacement of the wall by components of vertical displacements of the floor or roof. C� verifiedbe as follows: reportlo An approved testing laboratory shall verify the location and spacing of the ties and shall submit a - Chief.part of the structural selected2a The veneer in a arearemoved . expose representative sample ,f ties (not less than four) for inspection- __ • • ,-.Jr Pdothing shall prevent the pointing with mortar of all the masonry wall joints before the tests are first made. Prior to any painting, the mortar joints must be raked and cleaned to remove loose and deteriorated mortar. Mortar for painting shall be Type S or N exDept masonry Dements shall not be used. All preparation and mortar pointing shall be done under the continuous inspection of a speeial inspector. At the conclusion of the inspection, the inspector shall submit a written report to the person responsible for the seismic analysis of the building setting forth the results of the work inspected. Such 7 s . • � r • . .. •. _ • r. It1 • - '- a . s •. •. - r i,.: + •. i _ _ _ • _ • �^. �. :..'• • •. ::s _ _- • 1.-.. • `.' •a . --s 1 - -• e -•r'f i. i..... is - _ i 1 r � i` - i a • • r is - .: F •, • ♦. - i, i x - � - •.T' � r i... -i _ • �.. • is R... �}� - .. i. _. ice. _•: • r_. . ..• _y, �:. - f R ^ ♦ # r a; ar. � • r. _. _._• ...._ i. i.. . 0 The minimum height of a parapet above the wall anchor shall be 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 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 deterioratedmortar.Allpreparation and pointingshallbe done under the continuous inspection of a special inspector. At the conclusion of the project, the inspector shall submit a written report to the Chief Building Inspector setting forth the portion of work inspected. 6. Repair details for 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 any parapet bracing or other structural reinforcement to parts or portions of the building which were previously performed. 4. Accurately dimensioned floor plans and masonry wall elevations showing dimensioned opening, piers, wall thickness and heights, veneer locations and existing anchorages. 5. The locations of cracks or other damaged portions of unreinforced masonry walls requiring repair. 6. The type of interior wall surfaces and ceilings, and if reinstalling or anchoring of existing plaster is necessary. 7. The general condition of the mortar joints and if the joints need repointing. 8. The location of all in-place shear tests shall be shown on the floor plans and building wall elevations." "Design Check for CompatibilityfR Diaphragm General.requirements ... _- _ of this Chapter. The relative stiffness and ,» diaphragm governs amplificationground• diaphragm, therefore m stiffness and strength related check of the » _ of unreinforced masonry walls anchored wood diaphragms shall be made. This section contains a procedure for evaluation of a .. • bility of unreinforced walls anchored to wood diaphragms that are coupled to shear resisting elements. (b) Definitions. The following definitions are applicable to this Cross Wall. A wood framed wall having a height to length rati# complying with Section 4713(d) or table 25�1 of the 1985 Uniform Building Coand sheathed with any of the materials described in de Table AI�J or Table AI�K. The total strength of all cross walls located within any 40 feet length of diaphragm measured in the direction of the diaphragm span shall not be less than 30 percent of the strength of the diaphragm in the direction of consideration. Demand Demand equals_ lateral forces due to 33 percent of the combined weight of the diaphragm and the tributary weight of the walls and other elements anchored to the diaphragm. 2. Capacity equals the diaphragm total shear strength in the direction under consideration as determined using the values in Tables No. Al�J or Table AI�K. (c) Notations. B = depth of diaphragm, in feet, measured perpendicular to the diaphragm span. h/t = height -to -thickness of an unreinforced masonry wall. The height shall be measured between wall anchorage levels and the thickness shall be measured through the wall cross section at the level under consideration. L = span of diaphragm between masonry shear walls or steel frames. Vo = total shear capacity of cross walls in the direction of analysis immediately below the diaphragm level being investigated as determined by using Tables No. Al -J and Al -K. vu = maximum shear strength in pounds per foot for a diaphragm sheathed with any of the materials given in tables No. Al -J and Al -K. Wd = total dead load of the diaphragm plus the tributary weight of the walls anchored to the diaphragm, the tributary ceiling and partitions and weight of any other permanent building elements at the diaphragm level under consideration. m of the curve in Figure No. Al�L. Where the calculated DCR is #utside (to the right of) the curve, the diaphragm deflection limi are exceeded and cross walls may be used to reduce the deflection] • . Deleted _ ;.. Tables a - hereby deleted and Tables herebyTable Al�H are - . as follows: TABLE AO ALLOWABLE VALUE OF HEIGHT�THICKNESS (h/t) RATIO M. , MASONRY WALLS WITH MINIMUM QUALITY MORTAR 1 2 BUILDINGS WITH COMPLYING CROSS WALLS One Story Building Walls 1 13 — 16 3 a 5 f First Story of 1 Multi -Story Buildings I 16 i Walls in the Top Story ; of Multi -Story Buildings ; 9 - 14 5 5 5 6 B All Other Walls I 16 ALL OTHER OTHER BUILDINGS _____________ 13 15 9 13 a This table is nat applicable to buildings classified as essential facilities. Such building must be analyzed in accordance with Section A106. 3 The minimum martar shear strengths required in the following footnotes 4 and 5 shall be that shear strength without the effect of axial stress in the wall at the point of the test. a The larger height -to -thickness ratio may be used where mortar shear tests in accordance with Section A107(d) establish a minimum mortar shear strength of not less than 100 psi or where the tested mortar shear strength is not less than 60 psi and a visual examination of the vertical wythe-to-wythe wall joint (collar joint) indicates not less than 50 percent mortar coverage. 3 Where a visual examination of the collar joint indicates not less than 50 percent mortar coverage and the minimum mortar shear strength when established in accordance with Section A107(d) 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 ratio values in direct proportion to the mortar shear strength." 13 New Materials or Configuration of Materials 1. horizontal Diaphragms Plywood sheathing applied directly over existing straight sheathing with ends of plywood sheets bearing on joists or rafters and edges of plywood located within the center 1/3 of individual sheathing boards. 2. Shear Walls 600 I a. Plywood sheathing applied directly over existing wood studs. (No value I shall be given to plywood applied ; over existing plaster or wood sheathing boards. i b. Dry wall or plaster applied I directly over existing wood studs I c. Dry wall or plaster applied to I I plywood sheathing over wood studs I 3. Shear Bolts I Shear bolts and shear dowels I embedded a minimum of 8 inches I into unreinforced masonry walls. Bolt centered in a 2-1/2 inch diameter hole with dry -pack or non -shrink grout around the circumference of the bolt. 1 3 I 4. Tension Bolts Tension bolts and tension dowels I extending entirely through URM walls secured with bearing plates I on far side of wall with at least 30 square inches of area. 2 3 4 I 5. Combination Shear and Tension i Wall Anchors I (a) Bolts extending to the exterior face of the wall with a 2-1/2 inch round plate under the head.; Install as specified for shear bolts. Spaced not closer than 12 inches on centers. 1 2 3 ; m Allowable Values �J of the 1985 Uniform ilding Code Same as values specified i*: Table No. 25-K of the 1985 UBC for shear walls ecitied in Table No. 47�I the 1985 UBC e�third of the values ecified in Table No. 47-1 t!se 1985 UBC 133 percent of the values for plain masonry specified in Table No. 24-J of the 1985 C. No values larger than those given for 3/4 inch diameter bolts shall be used. lbs. per bolt for tension S Item 3 (Shear Bolts) for shear values. 5. Combination Shear and Tension ; Wall Anchors Continued (b) Bolts or dowels extending to 1200 lbs. per bolt or dowel the exterior face of the wall for tension4. See Item 3 for with a 2-1/2 inch round plate shear values. under the head and drill at an ; angle of 22-1/2 degrees to the ; horizontal. Install as ; specified for shear bolts. f 2 31 (c) Through bolt with bearing plate ! See Item 4 (Tension Bolts) for tension per Item 4. ; for tension values4. See Combined with minimum 8 inch o Item 3 for shear values. grouted section for shear per ; Item 3. e 6. Infilled Walls ; Reinforced masonry infilled openings; Same as values specified for in existing unreinforced masonry I unreinforced masonry walls walls with keys or dowels to match ; in this chapter. reinforcing. , 7. Reinforced Masonry ; Masonry piers and walls reinforced ; Same as values specified in as specified in Chapter 24 of the I Table No. 24-B of the 1985 1985 Uniform Building Code. Uniform Building Code. 8. Reinforced Concrete ; Concrete footings, walls and piers I Same as values specified in reinforced as specified in Chapter I Chapter 26 of the 1985 26 and designed for tributary loads.; Uniform Building Code 9. Existing Foundation Loads Foundation loads for structures J Calculated existing foundation exhibiting no evidence of settlement) loads due to maximum dead load ;plus live load may be increased 11 by 25 percent and may be I increased 50 percent for dead load plus seismic loads -------------------------------------------------------------------- required by this chapter. a Bolts and dowels to be tested as specified in Section A107. a Bolts and dowels to be 1/2 -inch diameter minimum. a Drilling for bolts and dowels shall be done with an electric rotary drill. Imgact tools shall not be used for drilling holes or tightening anchor and shear bolt nuts. a Allowable bolt and dowel values specified are for installations in minimum three Wythe wall. For installations in two Wythe walls use 50 percent of the value specified, except that no value shall be given to tension bolts that do not extend entirely through the wall and are secured with bearing plates on the far side." m 18.24.116 Tables Added Table No. Al�J and Al�K and Figure Al -L are hereby added to read as follows: ,•. COMPUTATIONALLOWABLE VALUES FOR EXISTING MATERIALS TO BE USED ONLY IN THE OF D CAPACITY RATIO DESIGN Existing Materials or Configuration of Materials s ---------------------------------- 1. Horizontal Diaphragms a. Roofs with straight sheathing and roofing applied directly to the sheathing. and roofing applied directly to the sheathing Allowable Values ---------------- 250 lbs. per foot for seismic shear. Per Sideo 200 lbs per foot for seismic shear. oil 125 lbs. per foot for seismic shear. L Materials must be sound and in gaud condition. Jill I Jill � 11 � 11 11111 Jill 111 11111111 1 Jill � I 1 11 111111111 Jill III ii !1 11 seismic shear." 0 m TABLE NO. Al -K ALLOWABLE VALUES FOR NEW MATERIALS USED IN CONJUNCTION WITH EXISTING CONSTRUCTION MATERIALS TO BE USED ONLY IN THE COMPUTATION OF THE DEMAND CAPACITY RATIO DESIGN CHECK New Materials or Configuration of New and Existing Materials s Allowable Values 1. Horizontal Diaphragms a. Plywood sheathing applied i directly over existing straight ; 225 lbs. per foot for sheathing with ends of plywood ; seismic shear. sheets bearing on rafters and edges of plywood located on the ; center of individual sheathing 1 boards. ; 2. Cross Walls 2 ; ° a. Plywood sheathing applied directly; over existing wood studs. No ; 1.33 times the values value shall be given to plywood i I specified in Table 25-K applied over existing plaster or Iof the 1985 UBCv wood sheathing. i b. Drywall or plaster applied 1 100 percent of the values directly over existing wood studs.; specified in Table 47-I of the 1985 UBC. = Materials must be sound and in good condition. ? For cross walls, values of all materials may be combined, except the total combined shear value shall not exceed 300 lbs. per foot for seismic shear." "FIGURE Al -lm 240 180 120 60 O REGION OF DEMAND/CAPACITY RATIOS WHERE CROSS WALLS MAY BE USED TO INCREASE H/T RATIOS O REGION OF DEMAND/CAPACITY RATIOS WHERE H/T RATIOS OF "WITH CROSS WALLS" MAY BE USED WHETHER OR NOT THEY ARE PRESENT U3 REGION OF DEMAND/CAPACITY RATIOS WHERE H/T RATIOS OF "ALL OTHER BUILDINGS" MUST I BE USED EVEN IF CROSS WALLS —I— ARE PRESENT { 1 1 I I I I I I I I i I I I I i I I 1 I 1033 1 1 1 1 i 1 I 1 i 1 1 I 1 I I I I I 1 1 I 1 1 I I 1 1 1 I 1 lO2 1 1 I 1 I I t I 1 1 1 t 1 I i 1 2 3 DEMAND/CAPACITY RATIO = 0.33Wd / 2vuD FE3 or 0.33Wd / 2vuD + Vc" 18.24.117 Remedies It shall be unlawful for the owner of a building identified as being within the scope of this ordinance to fail to submit plans and obtain a permit for correction of structural deficiencies discovered, or fail to complete the necessary structural corrections within the time period specified in Section 18.24.050, Table A. The City may invoke all remedies available at law, including but not limited to the following. (a) The City may revoke the building's certificate of occupancy and cause it to be vacated until such requirements are met. (b) The City may seek injunctive relief on behalf of the public to enjoin 6th day of a building owner's violation of this ordinance. law. Section 2. This ordinance shall be published as required by I, JUDITH A. MALFATTI, City Clerk of the City of Burlingame, do hereby certify that the foregoing ordinance was introduced at a regular meeting of the City Council held on the 6th day of August 1990, and was adopted there -after at a regular meeting of the City Council held on the 20th day of August 1990, by the following vote: , AYES: COUNCILMEMBER: BARYON, NARRISON, O'MAHONY, PAGLIARO NOES: COUNCILMEMBER: NONE ABSENT: COUNCZLMEMBER: LEMBI� K•- (77 City Clerk 19