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Ord 1800 - Urgency Ordinance Los Gatos Restoration ProgramORDINANCE NO: 1800 URGENCY ORDINANCE OF THE TOWN OF LOS GATOS ESTABLISHING THE LOS GATOS RESTORATION PROGRAM FOR THE REPAIR, RESTORATION AND RECONSTRUCTION OF STRUCTURES DAMAGED AS A RESULT OF THE OCTOBER 17, 1989 EARTHQUAKE WIIEREAS, conditions of extreme peril to the safety of persons and property have arisen in the Town of Los Gatos caused by an earthquake that occurred on October 17, 1989; and WHEREAS, it is necessary to suspend any section of the Town Code or Zoning Ordinance that is inconsistent with the intent and purpose of this urgency ordinance; and WHEREAS, on October 22, 1989, the Town Council of the Town of Los Gatos adopted a Proclamation Confirming the Town Manager's Proclamation of the Existence of a Local Emergency; and WHEREAS, numerous structures within the Town limits have suffered damage caused by the earthquake and the owners of these structures are desirous of repairing, restoring or reconstructing said structure as expeditiously as possible; and WHEREAS, on October 22, 1989, the Town Council expressed the policy of the Town to encourage the repair, restoration and reconstruction and reconstruction of damaged structures so that the Town may return to its appearance as existed prior to the earthquake and directed that procedures be established to facilitate said repair, restoration and reconstruction. THE TOWN COUNCIL OF THE TOWN OF LOS GATOS DOES HEREBY ORDAIN: SECTION I Purpose and Intent This Urgency Ordinance is intended to establish procedures and regulations for the repair, restoration and reconstruction of the structures damaged as a result of the earthquake that occurred on October 17, 1989 or the aftershocks that occurred subsequent to the main earthquake (hereafter "earthquake "). The purpose of this Urgency Ordinance is to provide for the expeditious repair, restoration and reconstruction of structures damaged as a result of said earthquake. All reasonable efforts shall be made to restore the facades of the damaged structures or to replicate the facade as it existed prior to the earthquake. The facades of nondescript structures may be modified to include design features that are compatible with other nearby structures and which clearly contribute to the character of the streetscape. SECTION II Establishment of Restoration Committee The Los Gatos Restoration Committee (hereafter 'Restoration Committee ") is hereby established to advise the Planning Director and the Director of Building Services in their joint decision concerning the issuance, denial, revocation or suspension of any permit to demolish, repair, restore or reconstruct any structure damaged as a result of the earthquake. The members of the Restoration Committee shall be the following persons or their designees: 1. Planning Director, 2. Director of Building Services, 3. Town Engineer, 4. Chief of the Central Fire District, 5. Chief of the Police Department, 6. Director of Parks, Forestry and Maintenance Services, and 7. Town Retained Historic Resources Consultant. The Restoration Committee shall meet on a regular basis and make written recommendations to the Planning Director and the Director of Building Services. The 7 applicant shall be entitled to be present at the meeting of the Restoration Committee with his or her representatives. SECTION III Standards for Repair. Restoration and Reconstruction of Masonry Buildings The Town hereby adopts by reference the Uniform Code for Building Conservation (1985 edition) except for the deletion of Chapters 1 and 2 and with the addition of Appendix Chapter 1 (Earthquake Hazard Reduction in Existing Unreinforced Masonry Buildings as amended by the Town - Exhibit A). All unreinforced masonry structures damaged as a result of the earthquake shall be repaired, reconstructed , rebuilt or restored in accordance with the Uniform Code for Building Conservation as denominated herein except that unreinforced chimneys shall be reconstructed in accordance with Section 4 of this Urgency Ordinance. The owner(s) of all unreinforced masonry buildings that were not damaged by the earthquake shall submit a structural engineering analysis as set forth in Appendix A. The structural analysis shall be submitted on or before May 1, 1990. The Director of Building Services may revoke occupancy of structures whose owner(s) do not meet the deadline. The repair or restoration of other structures shall be governed by Section 5 of this Urgency Ordinance. SECTION IV Reconstruction of Unreinforced Chimneys Unreinforced chimneys damaged by the earthquake shall be reconstructed in accordance with the seismic safety standards set forth in Chapter 37 of the currently adopted edition of the Uniform Building Code, and be made to the satisfaction of the Director of Building Services. 3 SECTION V Repair. Restoration and Reconstruction of Reinforced Masonry Structures, Woodframe Structures and Other Types of Structures The repair, reconstruction and reconstruction or restoration of reinforced masonry structures, woodframe structures and other types of structures shall be made in accordance with 75% of the current Uniform Building Code value for lateral forces to the satisfaction of the Planning Director and the Director of Building Services. SECTION VI Historic Structures Structures that are historically designated or located within a historic district shall not require review by the Historic Preservation Committee or the Planning Commission and shall be reviewed only by the Restoration Committee. SECTION VII Demolition Permits Demolition permits for structures damaged by the earthquake shall be approved by the Town Manager, Planning Director and the Director of Building Services only where it has been determined by the Director of Building Services that the structure cannot feasibly be repaired. Before any demolition permit may be issued, the structure shall be photographed, including architectural detail, to the satisfaction of the Planning Director. Any architectural detail uncovered during the demolition shall also be photographed to the satisfaction of the Planning Director. The Director of Building Services may require the preparation of a detailed structural analysis in order to assist in determining whether a structure cannot feasibly be repaired. 4 SECTION VIII Temporary Structures The Planning Director may approve permits for temporary structures on properties where a structure has been damaged by the earthquake and has been determined uninhabitable by the Director of Building Services. The permit for said temporary structure shall be for a limited period of time as determined by the Planning Director and shall be abated by that date unless an extension is granted by the Planning Director. SECTION IX Waiver of Zoning Ordinance and Town Code Requirements The Planning Director and the Director of Building Services shall have the authority to waive the requirements of the Town Zoning Ordinance and the Town Code to the extent that such provisions are contrary to the intent and purpose of this Urgency Ordinance. SECTION X Appeals The appeal of any decision by the Planning Director or the Director of Building Services permitted by this Urgency Ordinance shall be appealable to the Town Council. The appellant shall file a written notice of appeal with the Town Clerk not more than ten (10) days from the date of the decision. The appeal shall be heard by the Town Council within forty -five (45) days after filing of the notice of appeal. The Town Council may continue from time to time any hearing held. The Town Clerk shall set the hearing date for the appeal and shall give a notice of such hearing to the appellant and publish a notice in a newspaper of general circulation ten (10) days prior to the hearing. When hearing the appeal the Town Council shall consider the staff report, the applicable codes, regulations and standards involved and such additional evidence or testimony given at the hearing and may affirm, modify or reverse, in whole or part, the action being appealed. The decision of the Town Council upon the appeal shall be expressed by a written resolution, a copy of which shall be transmitted to the appellant, the Planning Director and the Director of Building Services. If the decision of the Town 5 Council is adverse to that of the Planning Director and the Director of Building Services, the resolution shall contain findings used in making their decision. SECTION XI Waiver of Fees All Town fees for any and all permits associated with the repair, reconstruction, restoration or demolition of any structure damaged as a result of the earthquake are waived. SECTION XII Non - Applicability The provisions of this Urgency Ordinance shall not apply to the repair or construction of any structure that is not to be restored to the appearance of said structure prior to the earthquake. SECTION XHI Severabilitv If any section, subsection, sentence, clause or phrase of this Urgency Ordinance is for any reason held by a court of competent jurisdiction to be invalid or unconstitutional, such decision shall not affect the validity of the remaining portions of this Urgency Ordinance and each section, subsection, sentence, clause and phrase thereof, irrespective of the fact that any one or more sections, subsections, sentences, clauses or phrases be declared invalid or unconstitutional. C SECTION XIV CEOA Exemption This urgency ordinance and any permits approved hereunder are exempt from the requirements of the California Environmental Quality Act (CEQA) pursuant to Public Resources Code Section 21080 (b)(2) and (3) and Section 21172 and Section 15269 of the CEQA Guidelines. SECTION XV It is necessary for the immediate preservation of the public peace, health and safety that this ordinance take effect immediately to preserve the economic viability of the community, and to insure that the character of the community is preserved. SECTION XVI This ordinance takes effect immediately upon its adoption and shall remain in effect until and including November 6, 1990. Within fifteen (15) days after this ordinance is adopted, the Town Clerk shall cause it to be published once in a newspaper of general circulation published and circulated in the Town. 7 This ordinance was adopted by the following vote as an urgency ordinance of the Town of Los Gatos at a regular meeting of the Town Council on November 6, 1989. AYES: COUNCIL MEMBERS: Thomas J. Ferrito, Robert L. Hamilton Brent N. Ventura, Mayor Joanne Benjamin NAYES: COUNCIL MEMBERS: NONE ABSENT: COUNCIL MEMBERS: Eric D. Carlson ABSTAIN: COUNCIL MEMBERS: NONE SIGNED: /limn �l i ✓N MAYO OF THE TOWN OF OS GATOS C ATTEST: / KO A/ LEPvvL d . CLERK OF THE TOWN OF LO GATOS a: \cnclrpts \restore.tcr .3 TOWN OF LOS GATOS APPENDIX A GUIDE FOR STURCTURAL INVESTIGATION AND ANALYSIS OF UNREINFORCED MASONRY BEARING WALL BUILDINGS SCOTT BAKER DIRECTOR OF BUILDING SERVICES EXHIBIT A APPENDIX A FOR INVESTIGATION OF URM BEARING WALL BUILDINGS (a) Preliminary Field Survey From existing plans or from field investigation prepare framing plans for roof and upper floors noting all beams, trusses, and major lintels at bearing walls. Prepare elevations of all URM walls noting the location and size of all openings in the walls. (b) Items for Special Investiaation (1) Identify and include on the plans all parts of the vertical load carrying system that may act as ties to lateral load resisting elements, to determine the elements that may control the relative displacement between the building's base and roof. (2) Identify and include on the plans all undamaged interior crosswalls that are continuous between the ground floor and roof noting if these are connected to the upper floor or roof by methods other than attachment of wall and ceiling finishes. (3) Examine and draw the relationship of the roof or floor framing to the ceiling framing (if separate) to determine the method if any of their interconnection. (4) Identify and include on the plans the support system for any URM walls that are not continuous to the base of the building noting the materials used for this support. (ie. steel frame). (5) Identify and include on the plans a description of the floor and roof sheathing and its attachment. Note any difference in materials on a given level that could lead to substantial variations in diaphragm stiffness. Note the size and location of openings in diaphragms adjacent to URM walls. Identify the roof covering system used and note if there are locations where it is on a cricket or other superimposed deck. A thorough investigation of the roof diaphragm is necessary to permit the evaluation of the compatibility of its stiffness with the out -of -plane stability of the URM walls of the story immediately below the roof as required in section (c) of the analysis procedure of this appendix. Exception: Where the damage conditions of a building prevent adequate investigation of any of the items listed above the Director of Building Services may exempt those upon request from the engineer performing the investigation. Assumptions regarding structural conditions or materials not directly observed or taken from existing plans must be clearly noted in the investigation report and analysis. (c) Investiaation of Existina Anchorage of URM Walls to Upper Floor and Roof. Indicate the location of all existing wall anchors on the roof /floor framing plans and specify their spacing, size and method of connection. If existing anchors are to be utilized as connections for resisting lateral force in the analysis these will require testing as specified in section (e)l. (d) Investigation of Existing URM Walls Investigate the following items if they occur in the building, and determine: (1) The thickness of URM walls at all levels and location of any changes in thickness. Substantial changes in wall thickness or stiffness shall be considered in the analysis for out -of -plane and in -plane wall stability. Variations in wall stiffness caused by nominal openings such as windows and doors need not be considered. (2) The materials used for lintels or arches at openings and their bearing area and connection to supporting columns or piers. The materials used for columns or piers supporting lintel beams or arches. (3) The heights of parapet, cornices and gable ends of URM walls above the uppermost existing anchorages. (4) The anchorage or bonding of terra cotta, cast -stone brick veneer or similar facing materials to the backup wythes of brickwork at cornices and other architectural appendages. (5) The coursing of exterior wythes of masonry, the bonding of wythes of masonry, and the materials used in each wythe. An examination of the wall joint between wythes (collar joint) must be made at each in -plane shear test location to estimate the percentage of wythe to wythe mortar coverage and the estimate shall be reported wit the results of the tests. Wythes of walls not bonded as described below shall be considered veneer The veneer wythe shall not be included in the effective thickness of the wall used to calculate the height -to- thickness ratio and the shear capacity of the wall and methods for its adequate anchorage must be devised. All units of URM bearing and non - bearing walls shall be laid with full shoved mortar joints; all head, bed and collar joints shall be solidly filled with mortar; and the bonding of adjacent wythes of multi -wythe walls shall be as follows: The facing and backing shall be bonded so that not less than 4 percent of the wall surface of each face is composed of headers extending not less than four inches into the backing. The distance between adjacent full length headers shall not exceed 24 inches vertically or horizontally. In walls where a single header does not extend through the wall, headers from the opposite sides shall overlap at least four inches, or headers from opposite sides shall be covered with another header course overlapping the header below at least four inches. (6) The condition of mortar joints and the location of any existing cracks or damaged portions of wall elements. Exception: Where the damage conditions of a building prevent adequate investigation of any of the items listed above the Director of Building Services may exempt those upon request from the engineer performing the investigation. Assumptions regarding structural conditions or materials not directly observed or taken from existing plans must be clearly noted in the investigation report and analysis. 2 (e) Testing The testing of existing anchorage systems must be made to determine an average capacity where these anchors are to be used in the analysis of the building's current resistance to lateral forces. The testing of existing URM walls to determine the allowable bed -joint shear is required for all buildings. (1) Existing Wall Anchors in URM Walls. Five percent of the existing rod anchors shall be tested in pullout by an approved testing laboratory. The minimum tested quantity shall be four per floor or roof level with two tests where framing is perpendicular to the wall and two where framing is 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. Where due to obstructions this is not possible, details of the condition encountered and the alternate method used must be included in the test report, with calibration adjustment for conditions where the reaction of the test apparatus contributes to the tension value of the anchor. The rod anchor shall be given a preload of 300 pounds prior to establishing a datum for recording elongation. The tension load reported shall be recorded at 1/8 inch relative movement of the anchor to the adjacent masonry wall surface. (2) In -Place Shear Test of Brick Masonry. 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. Steel bearing plates of the full dimension of the brick shall be inserted at each end of the test jack. The bearing plates shall not contact the mortar joints. The shear stress shall be based on the gross area of both bed joints and shall be that at which movement of the adjacent brick is first observed. The minimum quality mortar in 80 percent of the shear tests shall not be less than the total of 30 psi when reduced to an equivalent zero axial stress. If the larger height - to- thickness ratios allowed by footnotes #5 and #6 of Table A -2 are to be utilized in the analysis, all shear tests taken at the top story must be included in the 80 percent of the shear tests used to determine the minimum mortar shear strength. The minimum quantity of tests shall be as follows: At each story not less than two per wall line or line of wall elements providing a common line of resistance to lateral forces, with not less than one per 1500 square feet of wall surface and not less than a total of eight per building. In single story buildings the wall above the lintel beam at an open storefront need not be tested. The exact test locations shall be determined by the engineer responsible for the investigation and noted on the documents submitted to the Town. The tests should be conducted at least two brick courses above or below the bond course and be distributed vertically to include a variety of dead load surcharge conditions. Test locations shall be representative of the mortar conditions throughout the entire building, taking into account variations in workmanship, variations in weathering of exterior surfaces and variations of interior surfaces due to deterioration caused by leaks and condensation of water and /or by other deleterious substances contained within the building. 3 STANDARDS FOR THE ANALYSIS AND EVALUATION OF UNREINFORCED MASONRY BEARING WALL BUILDINGS (a) Structural Analysis Procedures (1) The total seismic forces should be computed in accordance with the following equation: V = ZIKCSW WHERE: The value of RCS need not exceed .100 for one story buildings with an occupant load of less than 100; and need not exceed .133 for buildings over one story above grade or those one story buildings with 100 or more occupants. The value of Z and I shall equal 1.0. The value of W shall be as defined in Chapter 23 of the 1985 Uniform Building Code (UBC). (2) Parts or portions of the building shall be analyzed for lateral loads in accordance with Chapter 23 of the 1985 UBC but not less that the value from the following equation: Fp = ICpSWp WHERE: The product of IS need not exceed 1.0. The value of Cp shall be as set forth in Table 23 -1 of the 1985 UBC. The value of Wp shall be as defined in the 1985 UBC. Exception: URM walls may be analyzed as indicated in Section (b) below. (3) The structural elements of the building required to be analyzed shall include the following: Wall height -to- thickness ratio and in -plane shear forces. Tension bolts (in bending) if used to resist lateral forces. Parapets for out -of -plane loading. Diaphragm stress and diaphragm chords at floors and roof. (4) Anchorage and interconnection of all parts, portions and elements of the structure resisting lateral forces shall be analyzed in accordance with the 1985 UBC and the formula in Subsection (2) above. A complete and continuous load path from every part or portion of the structure to the foundation shall be shown to exist for the required lateral forces. All parts, portions and elements of the structural systems shall be shown to be interconnected by an adequate positive means. (5) Except as modified herein, the lateral analysis of the building shall be in accordance with the analysis specified in the 1985 UBC. Stresses in existing materials and construction utilized to transfer seismic forces shall conform to either those permitted by the 1985 UBC or those permitted for types of materials and configurations specified in Table A -3 or those described in Section (b) below. When calculating shear of diagonal tension stresses due to seismic forces, existing masonry shear walls may be allowed to resist 1.0 times the required forces in lieu of the 1.5 factor required by the 1985 UBC. 1.1 (6) Masonry walls shall be anchorea to all floors and roof to resist a minimum of 200 pounds per linear foot acting normal to the wall at the level of the floor of roof or must be considered inadequate. No allowable tension stress will be permitted in URM walls. URM walls not capable of resisting the required design forces specified in this section shall be deemed inadequate. In addition to seismic forces, URM walls shall be analyzed as specified in Chapter 24 of the 1985 UBC to withstand all vertical loads. Exception: URM Walls which carry no design loads other than their own weight may be considered veneer if they adequately anchored to elements which are not part of the existing lateral force resisting system. See section (d) 5 under Procedures for Investigation to determine if existing walls,must be considered as veneer. (7) When stresses in existing lateral force resisting elements are due to a combination of dead and live plus seismic loads, the allowable working stress specified in the 1985 UBC may increased by 100 percent. However, no increase will be permitted in the stresses allowed in Section (b) below and the stresses in members due to only seismic and dead loads shall not exceed the values permitted in the 1985 UBC. In addition, the calculated tensile fiber stress due to seismic forces may be reduced by the full direct stress due to vertical dead loads. (b) Materials of Construction Standards (1) Unreinforced masonry walls analyzed in accordance with this section may provide support for roof and floor construction and resistance to lateral loads under the conditions set forth below. The bonding of such walls shall conform to those specified in Section (d) 5 of the Procedures for Investigation. Tension stresses due to seismic forces acting normal to the wall may be neglected if the wall does not exceed the height -to thickness ratio and the allowable in -plane shear stresses due to seismic loads set forth in Tables A -2 and A -4 respectively. If the wall height -to- thickness ratio exceeds the specified limits, the wall will be considered inadequate unless braced by vertical members designed to satisfy the requirements of the 1985 UBC. The deflection of such bracing members at design loads shall not exceed one -tenth of the wall thickness. Exception: The wall may be supported by flexible vertical bracing members that comply with the requirements of Section (a) 2 of the analysis procedure if the deflection at design loads is not less than one - quarter nor more than one -third of the wall thickness in the story under consideration. Any existing or new vertical bracing used for this purpose shall be attached to floor and roof construction independently of existing wall anchors and the horizontal spacing of the members shall not exceed one -half the unsupported height of the wall or ten feet, whichever is greater. E (2) Minimum Acceptable Quality of Existing URM Walls. 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 Section (e) 2 of the Procedures for Investigation. All masonry used to resist seismic forces shall be undamaged by shear failure cracking and be of a quality not less than the minimum standards established or shall be considered inadequate. Pointing of all masonry wall joints may be performed prior to the testing if joints are raked and cleaned to remove loose and deteriorated mortar. Mortar pointing shall be Type S or N, except masonry cements shall not be used. All preparation and pointing shall be done under the continuous inspection of a special inspector whose reports shall be included in the testing report. The design seismic in -plane shear stresses shall be related to test results in accordance with Table A -4. Intermediate values between 5 and 10 psi may be interpolated. Compression stresses for unreinforced masonry having a minimum design shear value of 3 psi shall not exceed 100 psi and design tension values shall not be permitted. (3) Existing Roof, Floors, and Walls. Existing undamaged materials, including wood shear walls may be analyzed as part of the lateral load resisting system, provided that the stresses in these materials do not exceed the values shown in Table A -3. New plywood shear walls designed in accordance with the 1985 UBC may be recommended to strengthen portions of the existing seismic resisting system. Diaphragm chord stresses of horizontal diaphragms shall be developed in existing materials or be considered inadequate. (4) Minimum URM Wall Anchorage. All URM walls shall be. anchored at both floors and roof by existing rod anchors at a maximum spacing of six feet and be secured to the joists or rafters to develop the required forces. At the building corners at roof and floor levels combination shear and tension anchors shall be located not more than two feet horizontally from the inside corners of the wall. Testing of existing rod anchors shall be conducted according to Section (e) 1 of the Procedures for Investigation. Walls without anchors having the necessary locations, spacing or capacity will be considered inadequate. (5) Minimum vertical Support. Where trusses or beams other than rafters or joists and beams supporting walls above open storefronts are supported on URM piers, these piers must be evaluated and shown to provide adequate vertical support during seismic loading or shall be independently supported by a vertical element other than the URM wall pier. (6) Minimum Parapet Bracing. Parapets and exterior wall appendages not capable of resisting the forces specified in Section (a) shall be considered hazardous. The maximum height of an unbraced URM wall parapet above the lower of either the level of existing adequate tension anchors or the roof sheathing, shall not exceed one and one -half times the thickness of the parapet wall. (a (c) Design Check for Compatibility of Roof Diaphragm Stiffness to the Out -of -Plane Stability of URM Walls. (1) General. The requirements of this section are in addition to the other analysis requirements of Section (a). This section contains a procedure for the evaluation of the out -of -plane stability of unreinforced masonry walls anchored to wood diaphragms. The relative stiffness and strength of a diaphragm governs the amount of amplification of seismic ground motion by the diaphragm, and therefore, a diaphragm stiffness and strength related check of the out -of -plane stability of URM walls must be performed. (2) Definitions. The following definitions are applicable to this section: CROSS WALL is a wood framed wall having,a height -to- length ratio complying with 1985 UBC Section 4713(d) or Table 25 -I and is sheathed with any of the materials described in Table A -1. 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 under consideration DEMAND CAPACITY RATIO (DCR) is a ratio where: Demand equals lateral forces due to 33 percent of the weight of the diaphragm and the tributary weight of walls and other elements anchored to the diaphragm. Capacity equals the diaphragm's total shear strength in the direction under consideration as determined using the values in Table A -1. D = the depth of the diaphragm, in feet, measured perpendicular to the diaphragm span. h/t = the height -to- thickness ratio 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 Vc = the total shear capacity of cross walls in the direction of analysis immediately below the diaphragm level being investigated as determined by using Table A -1. vu = Maximum shear strength in pound per foot for a diaphragm sheathed with any of the materials given in Table A -1. Wd = total dead load of the diaphragm plus the tributary weight of the walls anchored to the diaphragm, the tributary ceiling and partitions, and the weight of any other permanent building elements at the diaphragm level under consideration. 7 (3) Design Check Procedure. The demand - capacity ratio (DCR) shall be calculated by the following equations: Buildings without crosswalls 0.33 Wd DCR = -- - - - - -- 2 vu D Buildings with crosswalls 0.33 Wd DCR = ----- - - - - -- 2 vu D + Vc Diaphragm Deflection. The calculated DCR shall be the left of the curve in Figure A -5. Where the calculated DCR is outside (to the right) of the curve, the diaphragm's deflection limits are exceeded and cross walls are needed to reduce the deflection. URM Wall Out -of -Plane Stability. The DCR shall be calculated discounting any existing cross walls. If this DCR value corresponding to the diaphragm span is to the right of the curve in Figure A -5, the region within the curve at and below the intersection of the diaphragm span with the curve may be used to determine the allowable h/t values per Table A -2. TABLE A -1 ALLOWABLE VALUES FOR EXISTING WALLS AND DIAPHRAGMS ONLY FOR DETERMINATION OF THE DIAPHRAGM DEMAND / CAPACITY RATIO 1. Horizontal Diaphragms 1 a. Roofs with straight sheathing and roofing applied directly to the sheathing. b. Roofs with diagonal sheathing and roofing applied directly to the sheathing. 2. Crosswalls 1 a. Plaster on wood or metal lath b. Plaster on gypsum lath c. Gypsum wallboard unblocked d. Gypsum wallboard edges blocked Footnotes: 100 PLF for seismic shear 250 PLF for seismic shear 200 PLF per side for seismic shear 175 PLF per side for seismic shear 75 PLF per side for seismic shear 125 PLF per side for seismic shear 1. Materials must be undamaged and in good condition. M TABLE A -2 ALLOWABLE VALUE OF HEIGHT -TO- THICKNESS (H /T) RATIO OF URM WALLS WITH MINIMUM QUALITY MORTAR 1 , ? ------------------ - - - - -- One Story Building Walls First Story Walls of Multi -Story Buildings Walls in Top Story of . Multi -Story Buildings All Other Walls ------------------ - - - - -- Footnotes: Buildings with All Other Complying Crosswalls s Buildings --------------------------------------- 13 - 16 4, 5, 6 ; 13 16 i 15 I 9- 14 4, 5 6 I 9 16 i 13 --------------------------------- - - - - -- 1. Minimum quality mortar shall be determined by testing described in Section (e) 2 of the Procedures for Investigation and shall include all top story tests in the 80 percent of tests used if the higher ratio values permitted in footnotes 5 and 6 are used. 2. See section (c) for determination of the demand capacity ratio values to be used in conjunction with Figure A -5 to determine if the building can qualify as a building containing crosswalls. 3. Qualifying crosswalls are defined as interior walls of masonry or wood frame construction with surface finish of wood lath and plaster, 1/2 inch thick gypsum board, or solid horizontal wood sheathing. They may not exceed 40 feet horizontal separation, must be continuous through all stories and have a minimum length of 1 -1/2 times the story height. 4. The minimum mortar strengths required in footnotes # 5 and 6 shall be the test shear strength reduced by the effect of axial stress in the wall at the point of the test. 5. The larger height -to- thickness ratio may be used where mortar shear tests 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 (collar) joint indicates not less than 50 percent mortar coverage. 6. Where a visual examination of the collar joint indicates not less than 50 percent mortar coverage and the minimum mortar shear strength is greater than 30 psi but not less than 60 psi, the allowable h/t ratio may be determined by linear interpolation between the larger and smaller values given in direct proportion to the mortar shear strength. G TABLE A -3 ALLOWABLE STRESS VALUES FOR EXISTING MATERIALS FOUND TO BE UNDAMAGED AND IN GOOD CONDITION 1. Horizontal Diaphragms a. Roofs with straight sheathing with the roof covering applied directly to the sheathing. b. Roofs with diagonal sheathing with the roof covering applied directly to the sheathing 100 PLF for seismic shear 400 for seismic shear C. Floors with straight tongue and groove sheathing d. Floors with straight sheathing and finished wood flooring e. Floors with diagonal sheathing and finished wood flooring f. Floors or roofs with straight sheathing and plaster applied to the joists or rafters below 150 PLF for seismic shear 300 PLF for seismic shear 450 PLF for seismic shear Add 50 PLF to the allowable values for items la and lc. 2. Shear Walls a. Wood stud walls with lath and plaster in undamaged condition 100 PLF each side for seismic shear 3. Plain Concrete Footings 4. Douglas Fir Wood i 5. Reinforcing Steel 1 6. Structural Steel i Footnotes: V c = 1500 PSI unless otherwise shown by tests Same as 1985 UBC values for No. 1 Douglas Fir V t = 18,000 PSI maximum 1 V t = 20,000 PSI maximum 1 1. Stresses may be increased for combination of loads as specified in Section (a) 7 of the Standards for Analysis and Evaluation. i0 TABLE A -4 ALLOWABLE SHEAR STRESS FOR TESTED URM WALLS 80 Percent of Test Results Allowable In -Plane Shear in PSI Not Less Than: in PSI Based on Gross Area 1 -------------------------------------------------------------- - - - - -- 30 + Axial Stress 40 + Axial Stress 50 + Axial Stress 100 + Axial Stress or more -------------------- - - - - -- 3.0 4.0 5.0 10.0 (maximum) ------- ------- - - - - -- Footnotes: 1. The allowable shear stress may be increased by addition of 10 percent of the axial stress due to the weight of the wall directly above. 540 480 420 360 f- W _ U. = 300 2 6 d N Q � 240 d Q 180 60 120 `l O1 REGION OF DEMAND /CAPACITY RATIOS WHERE CROSSWALLS MAY BE USED TO INCREASE H/T RATIOS O2 REGION OF DEMAND /CAPACITY RATIOS WHERE H/T RATIOS OF "WITH CROSSWALLS" MAY BE USED O3 REGION OF OEMANO /CAPACITY RATIOS WHERE H/T RATIOS OF "ALL OTHER BUILDINGS" SHALL BE USED 7 O 0 1 2 3 4 5 6 DEMAND - CAPACITY RATIO O.33•WD/(2y OR 0. W /(2v + sv ACCEPTABLE SPAN FOR DIAPHRAGMS (BASED ON DISPLACEMENT CONTROL CONCEPTS) A -5 FIGURE 19 12 TOWN OF LOS GATOS AMENDMENTS TO THE UNIFORM CODE FOR BUILDING CONSERVATION APPENDIX CHAPTER 1 EARTHQUAKE HAZARD REDUCTION IN EXISTING UNREINFORCED MASONRY BUILDINGS Section A102 is hereby amended to read: The requirements of this chapter shall apply to all damaged buildings containing unreinforced masonry bearing walls and those undamaged buildings with unreinforced masonry walls which do not meet the requirements of this chapter for seismic resistance. Exception: This chapter shall not apply to Group M. or Group R, Division 3 occupancies, Group R, Division 3 occupancies with less than five dwelling units used solely for residential purposes, nor to any undamaged building less than 900 square feet and containing less than five occupants. Subsection (a) of Section A105 is hereby amended to read: General. A historic building may comply with the special provisions of this chapter and the provisions of the State Historic Building Code. The second paragraph of Subsection (a) of Section A106 is hereby amended to read: The value of RCS need not exceed but shall not be less than .100 for one story buildings with less than 100 occupants; and need not exceed but must not be less than .133 for one story buildings containing 100 or more occupants and buildings over one story above grade. The value of Z and I shall equal 1.0. The value of W shall be as defined in Chapter 23 of the 1985 Uniform Building Code. 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 IS shall equal 1.0. The value of Co shall be in accordance with Table 23 -1 of the 1985 Uniform Building Code. The value of Wp shall be as defined in Chapter 23 of the 1985 Uniform Building Code. Exception: Unreinforced masonry walls in buildings not required to be designed as an essential facility may be designed in accordance with Section A107. Paragraph 1 of subsection (f) of Section A106 is hereby amended to read: 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. Exception: Buildings with rigid concrete or steel and concrete roof diaphragms shall use the h/t values for all other buildings in Table Al -F Paragraph 3 of subsection (g) of Section A106 is hereby amended by adding the following paragraph after the second exception: Substantial changes in wall thickness or stiffness shall be considered in the analysis for out -of -plane and in -plane wall stability, and the wall shall be restrained against out -of -plane instability lay anchorage and bracing to the roof or floor diaphragm in accordance with Section A106 (d). Exception: Variations in wall stiffness caused by nominal openings such as windows and doors need not be considered. Subsection (b) of Section A107 is hereby amended to read: (b) Existing Materials. 1. Unreinforced 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. All units of both bearing and non - bearing walls hall be laid with 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 follows: The facing and backing shall be bonded so that not less than 4 percent of the wall surface of each face is composed of headers extending not less than four inches into the backing. The distance between adjacent full - length headers shall not exceed 24 inches either vertically or horizontally. In walls where a single header does not extend through the wall, headers from the opposite sides shall overlap at least four inches, or headers from opposite sides shall be covered with another header course overlapping the header below at least four inches. 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 to calculate the height -to- thickness ratio and the shear capacity of the wall. Tension stresses due to seismic forces normal to the wall may be neglected if the wall does not exceed the height -to- thickness ratio set forth in Table Al -F and the in -plane shear stresses due to seismic loads set forth in Table Al -I. If the wall height -to- thickness ratio exceeds the specified limit, the wall may be supported by vertical bracing members designed to satisfy the 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. Exception: The wall may be supported by flexible bracing members designed in accordance with Section A106 h of this chapter 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 consideration 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 other than a floor or roof. Spacing of bracing elements and wall anchors shall not exceed six feet. Bracing elements shall be detailed to minimize the horizontal displacement of the wall by components of vertical displacements of the floor or roof. Paragraph 2 of Subsection (b) of Section A107 is hereby renumbered to become paragraph 3 and a new Paragraph 2 is added to read: 2. Veneer. Veneer shall be anchored with approved anchor ties, conforming to the required design capacity specified in Section 3304(c ) of the 1985 Uniform Building Code, and placed at a maximum spacing of 24 inches. Exception: Existing veneer anchor ties may be acceptable provided the ties are in good condition and conform to the minimum size, maximum spacing and material requirements as indicated below. The veneer anchor ties shall be corrugated galvanized iron strips not less than one inch in width, eight inches in length and one - sixteenth of an inch in thickness and shall be located and laid in ever alternate course in the vertical height of the wall at a spacing not to exceed 17 inches on center horizontally. As an alternate, the spacing may be every fourth course vertically at a spacing not to exceed nine inches on center horizontally. The existence and condition of existing veneer anchor ties shall be verified as follows: 1 An approved testing laboratory shall verify the location and spacing of the ties and shall submit a report to the Director of Building Services for approval as a part of the structural analysis. 2. The veneer in a selected area shall be removed to expose a representative sample of ties (not less than four) for inspection by the Director of Building Services. Paragraph 1 of subsection (d) of Section A107 is hereby amended to read: 1. General provisions. All unreinforced masonry walls utilized to carry vertical loads and seismic forces parallel and perpendicular to he wall plane shall be tested as specified in this subsection. All masonry quality shall equal or exceed the minimum standards established herein or shall be removed and replaced by new materials The quality of mortar in all masonry walls shall be determined by performing in -place shear tests or by testing eight 3 inch diameter cores. Alternate testing methods may be approved by the Director of Building Services upon submission of adequate evidence to indicate its equivalence The vertical wall 'off int between wythes collar j oint shall be inspected at each test location after the in -place shear tests, and an estimate of the percentage of wvthe to wythe mortar coverage shall be reported along with the results of the in -place shear tests. 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. Nothing shall prevent the 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 special 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 report shall be submitted to the Director of Building Services for approval as part of the structural analysis. All testing shall be performed in accordance with the requirements specified in this section by an approved agency. An accurate record of all such tests and their location in the building shall be recorded and these results shall be submitted to the Director of Building Services for approval as part of the structural analysis. Paragraph 2 of Subsection (d) of Section A107 is hereby amended to read: 2. Number and location of tests. The minimum number of tests shall be as follows. At each of both the first and top stories, not less than two per wall line or line of wall elements providing a common line of resistance to lateral forces. At each of all other stories, not less than one per wall elements providing a common line of resistance to lateral forces. In any case, not less than one per 1500 square feet of wall surface and a total of eight. 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 bJ the deleterious effects of other substances contained within the building. Where the higher h/t ratios allowed in footnotes 4 and 5 of Table Al -F are to be utilized, all the in -place shear tests taken at the top story shall be included in the 80 percent of the shear tests used to determine the minimum mortar shear strength. The exact test locations shall be determined at the building site by the person responsible for the seismic analysis of the subject building. Paragraph 1 of Subsection (b) of Section A108 is hereby amended to read: (b) Construction Details. The following requirements with appropriate construction details shall be made a part of the 0 approved plans. 1. All unreinforced masonry walls shall be anchored at the roof and ceiling levels by tension bolts through the wall as specified in Table Al -H, or by an approved equivalent at a maximum anchor spacing of six feet. All unreinforced masonry walls shall be anchored at all floors and ceiling with tension bolts through the wall or by existing rod anchors at a maximum anchor spacing of six feet. All existing rod anchors shall be secured to the joists to develop the required forces. Tests conforming to this chapter will be required to verify the adequacy of the embeded ends of existing rod anchors. Exception: Walls need not be anchored to ceiling systems that, because of their low mass and or relative location with respect to the floor or roof systems, would not impose significant normal forces on the wall and cause out -of -plane wall failure. Calculations and drawings to verify this exception must be submitted as part of the analysis. At the roof and all floor levels, the anchors nearest the building corners shall be combination shear and - tension anchors located not more than two feet horizontally from the inside corners of the walls. When access to the exterior face of the masonry wall is prevented by proximity of an existing building, wall anchors conforming to Items 5 and 6 in table no. Al -H may be used. Alternative devices to be used in lieu of tension bolts for masonry wall anchorage shall be tested as specified in Section A107(h). Paragraph 3 of Subsection (b) of Section A108 is hereby amended to read: 3. Where trusses and beams other than rafters or joists are supported on masonry independent secondary columns shall be installed to support vertical loads. Paragraph 4 of Subsection (b) of Section A108 is hereby amended to read: 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. 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 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 the Table 23 -J of the 1985 Uniform Building Code shall support the top of the parapet. Parapet corrective work must be performed in conjunction with the installation of tension roof anchors. The minimum height of a parapet above the wall anchor shall be 12 inches. Exception: If a reinforced concrete beam is provided at the top of the wall, the minimum height above the wall anchor may be six inches. 5 Paragraph 5 of Subsection (b) of Section A108 is hereby amended to read: 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 special inspector. At the conclusion of the project, the inspector shall submit a written report to the Director of Building Services setting forth the portion of work inspected. Paragraph 4 of Subsection (c) of Section A108 is hereby amended to read: 4. Accurately dimensioned floor plans and masonry wall elevations showing dimensioned opening, piers, wall thickness and heights, veneer locations and existing anchorages Paragraph 6 of Subsection (c) of Section A108 is hereby amended to read: 6. The type of interior wall surfaces and ceilings and if reinstalling or anchoring of existing plaster is necessary. Paragraph 8 of Subsection (c) of Section A108 is hereby added to read: 8. The location of all in -place shear tests or core tests, shall be shown on the floor plans and building wall elevations. A new Section A109 is hereby added to Chapter 1. Design Check for Compatibility of Roof Diaphragm Stiffness to Unreinforced Masonry Wall Out -of -Plane Stability. Sec. A108 (a) General. The requirements of this section are in addition to the other analysis requirements of this Chapter. The relative stiffness and strength of a diaphragm governs the amount of amplification of the seismic ground motion by the diaphragm, and therefore, a diaphragm stiffness and strength related check of the out -of plane stability of unreinforced masonry walls anchored to wood diaphragms shall be made. This section contains a procedure for evaluation of the out -of -plane stability of unreinforced masonry walls anchored to wood diaphragms that are coupled to shear resisting elements. (b) Definitions. The following definitions are applicable to this section. Cross Wall. A wood framed wall having a height to length ratio complying with Section 4713(d) or table 25 -I of the 1985 Uniform Building Code. and sheathed with any of the materials described in Table Al -J or Table Al -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. 6 Demand Capacity Ratio (DCR). A ratio of the following: 1. Demand equals the lateral forces due to 33 percent of the 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 Al -K. (c) Notations. D = 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. Vc = 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. (d) Design Check Procedure. 1. General. The demand - capacity ratio (DCR) for the building shall be calculated using the following equations: DCR = 0.33 Wd / 2 vu D For building without cross walls or DCR = 0.33 Wd /2 vu D + Vc For building with cross walls 2. Diaphragm Deflection. The calculated DCR shall be to the left of the curve in Figure No. Al -L. Where the calculated DCR is outside (to the right of) the curve, the diaphragm deflection limits are exceeded and cross walls may be used to reduce the deflection. 3. Unreinforced Masonry Wall Out -of -Plane Stability. The DCR shall be calculated discounting any cross wall. If the DCR from this method corresponding to the diaphragm span is to the right of the curve in Figure No. Al -L, the region within the curve at and below the intersection of the diaphragm span with the curve may be used to determine the allowable h/t values per Table No. Al -F. Table Al -F of Chapter 1 is hereby amended to read: TABLE NO Al -F ALLOWABLE VALUE OF HEIGHT - THICKNESS (h /t) RATIO OF UNREINFORCED MASONRY WALLS WITH MINIMUM QUALITY MORTAR 1 2 -------------------------------------------------------------------- I BUILDINGS WITH ALL OTHER I COMPLYING CROSS WALLS BUILDINGS I -------- ---------------------------------- One Story Building Walls { 13 - 16 3 4 a I 13 First Story of Multi -Story Buildings Walls in the Top Story of Multi -Story Buildings All Other Walls 16 9` 14 3 4 e 16 15 7 13 1 Minimum mortar quality shall be determined by laboratory testing in accordance with this chapter. 2 This table is not applicable to buildings classified as essential facilities. Such building must be analyzed in accordance with Section A106. 3 The minimum mortar 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 op int of the test. 4 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 'off int collar joint) indicates not less than 50 percent mortar coverage. ° Where a visual examination of the collar 'o3 int indicates not less than 50 percent mortar coverage and the minimum mortar shear strenath 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 strenath. Portions of Table No. Al -H are hereby modified to read: 3. Shear Bolts Shear bolts and shear dowels embedded a minimum of 8 inches 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 [ +� 133 percent of the values for plain masonry specified in Table No. 24 -J of the 1985 UBC. No values larger than those given for 3/4 inch diameter bolts shall be used. 5. Combination Shear and Tension Wall Anchors (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 z 3 (b) Bolts or dowels extending to the exterior face of the wall with a 2 -1/2 inch round plate under the head and drill at an angle of 22 -1/2 degrees to the horizontal. Install as specified for shear bolts. 1 2 3 600 lbs. per bolt for tension see Item 3 (Shear Bolts) for shear values. 1200 lbs. per bolt or dowel for tension See Item 3 for shear values. (c) Through bolt with bearing plate See Item 4 (Tension Bolts) for tension per Item 4. for tension values See Combined with minimum 8 inch Item 3 for shear values. grouted section for shear per Item 3. The following footnotes are hereby added to Table No. Al -H 3 Drilling for bolts and dowels shall be done with an electric rotary drill. Impact tools hall not be used for drilling holes or tightening anchor and shear bolt nuts. 4 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. New Tables No. Al -J and No. Al -K are hereby added to Chapter 1 to read: TABLE NO. Al -J ALLOWABLE VALUES FOR EXISTING MATERIALS TO BE USED ONLY IN THE COMPUTATION OF THE DEMAND CAPACITY RATIO DESIGN CHECK Existing Materials or Configuration of Materials 1 ---------------------------------- 1. Horizontal Diaphragms a. Roofs with straight sheathing and roofing applied directly to the sheathing. Allowable Values 100 lbs. per foot for seismic shear. b. Roofs with diagonal sheathing and roofing applied directly to the sheathing 2. Cross Walls 2 a. Plaster on wood or metal lath. 250 lbs. per foot for seismic shear. Per Side: 200 lbs per foot for seismic shear. u b. Plaster on gypsum lath. 175 lbs. per foot for seismic shear. c. Gypsum wall board unblocked 75 lbs. per foot for edges. seismic shear. d. Gypsum wall board blocked 125 lbs. per foot for edges. seismic shear. ------------------------------------------------------------------- i Materials must be sound and in good condition. 2 For cross walls, values of all materials may be combined, except the total combined value shall not exceed 300 lbs. per foot for seismic shear. 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 t ------------------------------------ 1. Horizontal Diaphragms a. Plywood sheathing applied directly over existing straight sheathing with ends of plywood sheets bearing on rafters and edges of plywood located on the center of individual sheathing boards. Allowable Values 225 lbs. per foot for seismic shear. 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 specified in Table 25 -K applied over existing plaster or of the 1985 UBC. wood sheathing. b. Drywall or plaster applied 100 percent of the values directly over existing wood studs specified in Table 47 -I of the 1985 UBC. ------------------------------------------------------------------ 1 Materials must be sound and in good condition. 2 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. A new Figure Al -L is hereby added to Chapter 1 to read: H y s $40 480 420 0 360 f „ W lL = 300 a a H 240 4 180 OI REGION OF DEMAND /CAPACITY RATIOS WHERE CROSSWALLS MAY BE USED TO INCREASE H/T RATIOS 02 REGION OF DEMANO /CAPACITY RATIOS WHERE H/T RATIOS OF "WITH CROSSWALLS" MAY BE USED Q3 REGION OF DEMAND /CAPACITY RATIOS WHERE H/T RATIOS OF "ALL OTHER BUILDINGS" SHALL BE USED 120 ` 60 0 i 1 IN 0 1 2 3 4 5 6 DEMAND-CAPACITY RATIO, 0.33•WD/(2v OR 0.33 W /(2Y + LY,) ACCEPTABLE SPAN FOR DIAPHRAGMS (BASED ON DISPLACEMENT CONTROL CONCEPTS) FIGURE VP It is the policy of the Town Council to; repair damaged structures rather than demolish. It is the intent of the Los Gatos Building Restoration Program:. a. To provide guidelines for the. repair or reconstruction of buildings damaged in the earthquake of October 17 1989, or.,from the; aftershocks after that date. b. To create a: development process. -that will provide for the.£apid repair of damaged buildings within adopted code- .limitations•. fl 4 ,:, c.._ To encourage the restoration: and; reconstruction of damaged: buildings to insure-the preservation of the exterior of buildings as they existed before the - ,earthquake.:- (See guidelines > for, ­repair,, reconstruction and now construction: below.)_-,'_ - The Town has developed the following. .procedures,.for the repair or. reconstruction of earthquake damaged - buildings - .- There are three categories of- permits -for such work: repair, reconstruction as,existing earthquake, and new construction. I. REPAIR Repair of, structure to its- exiating, status. before., quake A. All Town fee* waived, B. Structural Guidelines: 1. Unreinforced masonry. structural - :repairs.. the.Unifom -KCode for Buildin& Conservation will be the standard. 2. _ Other building types - need to satisfy current building code requirements except lateral seismic. design may, be as. low as 75 = percent of the requirement of the current code C. Will require building, permits. only: N¢: public- review or hearing process. D. Fireplace repairs: the fireplace must meet current criteria for seismic design. Handouts showing these requirements are available at the Planning, Building, Engineering departments counter on the lower level of the Town Civic Center. F/U IM 2 1 II. RECONSTRUCTION - Replacement of an existing structure, by a new structure with the floor area, setbacks, and exterior identical to previous structure. A. All Town fees waived. B. Will require Restoration Committee review as well as building permits. No public hearing process. The Restoration Committee will consist of the following members or their designee: ■ Director of Building Services - ■ Planning Director ■ Town Engineer ■ Central Fire District Chief ■ Police Chief ■ Director of Parks, Forestry and Maintenance Services ■ Historical Restoration Consultant hired by the Town C. The new structure must meet all current building code requirements. All demolition requires a Town approved demolition permit prior to commencement. Removal of any portion of a structure is a demolition. D. Buildings not historically designated shall be rebuilt in an architectural style consistent with the historical flavor of downtown as identified by a Town retained professional consultant, the Restoration Committee and approved by the Town Council. The approved styles of architecture and choice of exterior materials will be identified by a Town retained professional architectural consultant after recommendation from the Historic Preservation Committee and approved by the -Town Council. E. Town designated historic buildings shall be rebuilt to their original identical construction with seismic safety improvements added. F. Interior spaces may be rearranged or reorganized as desired, under repair or reconstruction, as long as total floor area is not increased. G. Demolition application may require structural report. Eligibility for the repair and reconstruction options is only possible if the demolition, if any, was in accordance with an approved demolition permit. H. Off -site improvements not required. The final decisions regarding reconstruction are determined jointly by the Director of Building Services and the Planning Director subject to appeal to the Town Council. III. NEW CONSTRUCTION - Replacement of existing structure with �new structure which is identical to the previous structure to be removed. A. All fees must be paid. B. Normal review- process; Development Review Committee, Planning, Commission, Town Council, must meet all state regulation and Town codes and ordinances and all public noticing requirements. IV. A. Illegal or unlawful construction or- unlawful- occupancy will not be allowed to be reestablished. B. The current grading moratorium has not been amended. PL05 \2&rth.gk October 27, 1989 1�