Code Review With Checklist
Earthquake Hazard Reduction in Existing Wood-Frame
Residential Buildings With Soft, Weak or Open-Front Walls
§EBA401.1 Purpose: The purpose of this chapter is to promote public welfare and safety by reducing the risk of death or injury that may result from the effects of earthquakes on existing wood-frame, multiunit residential buildings. The ground motions of past earthquakes have caused the loss of human life, personal injury and property damage in these types of buildings. This chapter creates minimum standards to strengthen the more vulnerable portions of these structures. When fully followed, these minimum standards will improve the performance of these buildings but will not necessarily prevent all earthquake-related damage.
§EBA401.2 Scope: The provisions of this chapter shall apply to all existing wood-frame buildings, or portions thereof, that are used as hotels, lodging houses, congregate residences or apartment houses where:
The ground floor portion of the wood-frame structure contains parking or other similar open floor space that causes soft, weak or open-front wall lines as defined in this chapter, and there exists one or more levels above, or
The walls of any story or basement of wood construction are laterally braced with nonconforming structural materials as defined in this chapter, a soft or weak wall line exists as defined in this chapter, and there exist two or more levels above.
This chapter is applicable to Seismic Hazard Zones where SD1 is 0.3g or higher.
Notwithstanding the applicable definitions, symbols and notations in the Building Code of New York State, the following definitions shall apply for the purposes of this chapter:
- Apartment House: Any building or portion thereof that contains three or more dwelling units. For the purposes of this chapter, apartment house includes residential condominiums.
- Aspect Ratio: The span-width ratio for horizontal diaphragms and the height-length ratio for vertical diaphragms.
- Congregate Residence: A congregate residence is any building or portion thereof for occupancy by other than a family that contains facilities for living, sleeping and sanitation as required by this code, and that may include facilities for eating and cooking. A congregate residence may be a shelter, convent, monastery, dormitory, fraternity or sorority house, but does not include jails, hospitals, nursing homes, hotels or lodging houses.
- Cripple Wall: A wood-frame stud wall extending from the top of the foundation wall to the underside of the lowest floor framing.
- Dwelling Unit: Any building or portion thereof for not more than one family that contains living facilities, including provisions for sleeping, eating, cooking and sanitation as required by this code, or congregate residence for 10 or fewer persons.
- Expansion Anchor: An approved mechanical fastener placed in hardened concrete that is designed to expand in a self-drilled or pre-drilled hole of a specified size and engage the sides of the hole in one or more locations to develop shear and/or tension resistance to applied loads without grout, adhesive or dry pack.
- Ground Floor: Any floor within the wood-frame portion of a building whose elevation is immediately accessible from an adjacent grade by vehicles or pedestrians. The ground floor portion of the structure does not include any level that is completely below adjacent grades.
- Guestroom: Any room or rooms used or intended to be used by a guest for sleeping purposes. Every 100 square feet (9.3 m2) of superficial floor area in a congregate residence shall be considered a guestroom.
- Hotel: Any building containing six or more guestrooms intended or designed to be used, rented, hired out to be occupied, or that are occupied, for sleeping purposes by guests.
- Level: A story, basement or under floor space of a building with cripple walls exceeding 4 feet (1219 mm) in height.
- Life Safety Performance Level: The building performance level that includes significant damage to both structural and nonstructural components during a design earthquake, though at least some margin against either partial or total structural collapse remains. Injuries may occur, but the level of risk for life-threatening injury and entrapment is low.
- Lodging House: Any building or portion thereof containing at least one but not more than five guest rooms where rent is paid in money, goods, labor or otherwise.
- Motel: Motel shall mean a hotel as defined in this chapter.
- Multiunit Residential Buildings: Hotels, lodging houses, congregate residences and apartment houses.
- Nonconforming Structural Materials: Wall bracing materials other than wood structural panels or diagonal sheathing.
- Open-Front Wall Line: An exterior wall line, without vertical elements of the lateral-force-resisting system that requires tributary seismic forces to be resisted by diaphragm rotation or excessive cantilever beyond parallel lines of shear walls. Diaphragms that cantilever more than 25% of the distance between lines of lateral-force-resisting elements from which the diaphragm cantilevers shall be considered excessive. Exterior exit balconies of 6 feet (1829 mm) or less in width shall not be considered excessive cantilevers.
- Retrofit: An improvement of the lateral-force-resisting system by alteration of existing structural elements or addition of new structural elements.
- Soft Wall Line: A wall line whose lateral stiffness is less than that required by story drift limitations or deformation compatibility requirements of this chapter. In lieu of analysis, a soft wall line may be defined as a well line in a story where the story stiffness is less than 70% of the story above for the direction under consideration.
- Story Strength: The total strength of all seismic-resisting elements sharing the same story shear in the direction under consideration.
- Wall Line: Any length of wall along a principal axis of the building used to provide resistance to lateral loads. Parallel wall lines separated by less than 4 feet (1219 mm) shall be considered one wall line for the distribution of loads.
- Weak Wall Line: A wall line in a story where the story strength is less than 80% of the story above in the direction under consideration.
§EBA403: Analysis & Design
§EBA403.1 General: Buildings within the scope of this chapter shall be analyzed, designed and constructed in conformance with the 2007 Uniform Building Code except as modified in this chapter. Prior to any analysis, an initial screening review of the buildings shall be performed as noted in §EBA403.1.1. All items found to be noncompliant shall be addressed in this analysis.
No alteration of the existing lateral-force-resisting or vertical-load-carrying system shall reduce the strength or stiffness of the existing structure. When any portion of a building within the scope of this chapter is constructed on or into a slope steeper than 1 unit vertical in 3 units horizontal, the lateral-force-resisting system at and below the base level diaphragm shall be analyzed for the effects of concentrated lateral forces at the base caused by this hillside condition.
- Buildings in which all items on the applicable checklist - Table EBA4-A through Table EBA4-D - are marked compliant.
- Prescriptive measures provided in §EBA405 may be used in two-story buildings of no geometrical irregularity when the roof covering of the structure is of material weighing 5 pounds per square foot (240 N/m2) or less; when the aspect ratio of the floor diaphragm meets the current code requirements; and only when deemed appropriate by the code enforcement official.
§EBA403.1.1 Initial Screening: Prior to any analysis, an initial screening review of the buildings shall be performed. Each of the evaluation statements on this checklist shall be marked compliant (C), noncompliant (NC) or not applicable (N/A). Compliant statements identify issues that are acceptable according to the criteria of this chapter, while noncompliant statements identify issues that require further investigation. Certain statements may not apply to the buildings being evaluated. For noncompliant evaluation statements, the design professional may choose to conduct further investigation or comply with the prescriptive requirements of this chapter.
§EBA403.2 Scope of Analysis: This chapter requires the alteration, repair, replacement or addition of structural elements and their connections to meet the strength and stiffness requirements herein. The lateral-load-path analysis shall include the resisting elements and connections from the wood diaphragm above any soft, weak or open-front wall lines to the foundation soil interface or the upper level of a Type I structure below. The top story of any building need not be analyzed. The lateral-load-path analysis for added structural elements shall also include evaluation of the allowable soil-bearing and lateral pressures in accordance with UBC §1805.
Exception: When an open-front, weak or soft wall line exists because of parking at the ground level of a two-level building, and the parking area is less than 20% of the ground floor level, then only the wall lines in the open, weak or soft directions of the enclosed parking area need comply with the provisions of this chapter.
§EBA403.3 Design Base Shear: The design base shear in a given direction shall be 75% of the value determined by Formulas (30-4) through (30-7) in UBC §1630.2.
§EBA403.4 Vertical Distribution of Forces: The total seismic force shall be distributed over the height of the structure based on Formula (30-15) in UBC §1630.5. Distribution of force by story weight shall be permitted for two-story buildings. The value of R used in the design of any story shall be less than or equal to the value of R used in the given direction for the story above.
§EBA403.5 Weak Story Limitation: The structure shall not exceed 30 feet (9144 mm) in height or two levels if the lower level strength is less than 65% of the story above. Existing walls shall be strengthened as required to comply with this provision unless the weak level can resist a total lateral seismic force of W0 times the design force prescribed in §EBA403.4.
The story strength for each level of all other structures shall be a minimum of 80% of the story above.
§EBA403.6 Story Drift Limitation: The calculated story drift for each retrofitted level shall not exceed the allowable deformation compatible with all vertical-load-resisting elements and 0.025 times the story height. The calculated story drift shall not be reduced by the effects of horizontal diaphragm stiffness but shall be increased when these effects produce rotation. Drift calculations shall be in accordance with UBC §1630.9 and §1630.10.
The effects of rotation and soil stiffness shall be included in the calculated story drift when lateral loads are resisted by vertical elements whose required depth of embedment is determined by pole formulas, such as Formulas (6-1) and (6-2) in UBC §1806.8.2. The range of this coefficient of sub grade reaction used in the deflection calculations shall be provided from an approved geotechnical engineering report or other approved methods.
§EBA403.7 P D Effects: The requirements of UBC §1630.13 and §1633.2.4 shall apply except as modified herein. All structural framing elements and their connections not required by design to be part of the lateral-force-resisting system shall be designed and/or detailed to be adequate to maintain support of design dead plus live loads when subjected to the expected deformations caused by seismic forces. The stress analysis of cantilever columns shall use a buckling factor of 2.1 for the direction normal to the axis of the beam.
§EBA403.8 Ties and Continuity: All parts of the structure included in the scope of §EBA403.2 shall be interconnected, and the connection shall be capable of resisting the seismic force created by the parts being connected. Any smaller portion of a building shall be tied to the remainder of the building with elements having a strength to resist 0.5 CaI times the weight of the smaller portion. A positive connection for resisting a horizontal force acting parallel to the member shall be provided for each beam, girder or truss included in the lateral load path. This force shall not be less than 0.5 CaI times the dead plus live load.
§EBA403.8.1 Cripple Walls: Unbraced cripple walls found to be noncompliant in Table EBA4-C shall be analyzed and designed per Chapter EB3. When a single top plate exists in the cripple wall, all end joints in the top plate shall be tied. Ties shall be connected to each end of the discontinuous top plate and shall be equal to one of the following:
Three-inch-by-6-inch (76 mm by 152 mm), 18-gage galvanized steel, nailed with six 8d common nails at each end.
One and one-fourth-inch-by-12-inch (32 mm by 305 mm), 18-gage galvanized steel, nailed with six 16d common nails at each end.
Two-inch-by-4-inch-by-12-inch (51 mm by 102 mm by 305 mm) wood blocking, nailed with six 16d common nails at each end.
§EBA403.9 Collector Elements: Collector elements shall be provided that can transfer the seismic forces originating in other portions of the building to the elements within the scope of §EBA403.2 that provide resistance to those forces.
§EBA403.10 Horizontal Diaphragms: The analysis of shear demand or capacity of an existing plywood or diagonally sheathed horizontal diaphragm need not be investigated unless the diaphragm is required to transfer lateral forces from the lateral-resisting elements above the diaphragm to other lateral-resisting elements below the diaphragm because of an offset in placement of the elements.
Wood diaphragms in structures that support floors or roofs above shall not be allowed to transmit lateral forces by rotation or cantilever except as allowed by the Building Code of New York State. However, rotational effects shall be accounted for when unsymmetric wall stiffness increases shear demands.
Exception: Diaphragms that cantilever 25% or less of the distance between lines of lateral-load-resisting elements from which the diaphragm cantilevers may transmit their shears by cantilever, provided that rotational effects on shear walls parallel and perpendicular to the load are taken into account.
§EBA403.11 Shear Walls: Shear walls shall have sufficient strength and stiffness to resist the tributary seismic loads and shall conform to the special requirements of this section.
§EBA403.11.1 Gypsum or Cement Plaster Products: Gypsum or cement plaster products shall not be used to provide lateral resistance in the soft or weak story.
§EBA403.11.2 Wood Structural Panels
§EBA403.11.2.1 Drift Limit: Wood structural panel shear walls shall meet the story drift limitation of §EBA403.6.
§EBA403.11.2.1 Drift Limit: Wood structural panel shear walls shall meet the story drift limitation of §EBA403.6. Conformance to the story drift limitation shall be determined by approved testing or calculation, or analogies drawn therefrom, and not by the use of an aspect ratio. Calculated deflection shall be determined according to UBC Standard 23-2, Section 23.223, "Calculation of Shear Wall Deflection," and 25% shall be added to account for inelastic action and repetitive loading. Contribution to the shear wall deflection from the anchor or tie-down slippage shall also be included. The slippage contribution shall include the vertical elongation of the connector metal components, the vertical slippage of the connectors to framing members, localized crushing of wood due to bearing loads, and shrinkage of the wood elements because of changes in moisture content as a result of aging. The total vertical slippage shall be multiplied by the shear panel aspect ratio and added to the total horizontal deflection. Individual shear panels shall be permitted to exceed the maximum aspect ratio, provided the story drift and allowable shear capacities are not exceeded.
§EBA403.11.2.2 Openings: Shear walls are permitted to be designed for continuity around openings in accordance with §2315.1 of the UBC. Blocking and steel strapping shall be provided at corners of the openings to transfer forces from discontinuous boundary elements into adjoining panel elements. Alternatively, the perforated shear wall provisions of the Building Code of New York State may be used.
§EBA403.11.2.3 Wood Species of Framing Members: Allowable shear values for wood structural panels shall consider the species of the framing members. When the allowable shear values are based on Douglas fir-larch framing members, and framing members are constructed of other species of lumber, the allowable shear values shall be multiplied by the following factors: 0.82 for species with specific gravities greater than or equal to 0.42 but less than 0.49, and 0.65 for species with specific gravities less than 0.42. Redwood shall use 0.65 and hem fir shall use 0.82, unless otherwise approved.
§EBA403.11.3 Substitution for 3-Inch (76 mm) Nominal Width Framing Members: Two 2-inch (51 mm) nominal width framing members shall be permitted in lieu of any required 3-inch (76 mm) nominal width framing member when the existing and new framing members are of equal dimensions, when they are connected as required to transfer the in-plane shear between them, and when the sheathing fasteners are equally divided between them.
§EBA403.11.4 Hold-Down Connectors
§EBA403.11.4.1 Expansion Anchors in Tension: Expansion anchors that provide tension strength by friction resistance shall not be used to connect hold-down devices to existing concrete or masonry elements. Expansion anchors that provide tension strength by bearing (commonly referenced as "undercut" anchors) shall be permitted.
§EBA403.11.4.2 Required Depth of Embedment: The required depth of embedment or edge distance for the anchor used in the hold-down connector shall be provided in the concrete or masonry below any plain concrete slab unless satisfactory evidence is submitted to the code enforcement official that shows that the concrete slab and footings are of monolithic construction.
§EBA403.11.4.3 Required Preload of Bolted Hold-Down Connectors: Bolted hold-down connectors shall be preloaded to reduce slippage of the connector. Preloading shall consist of tightening the nut on the tension anchor after the placement but before the tightening of the shear bolts in the panel flange member. The tension anchor shall be tightened until the shear bolts are in firm contact with the edge of the hole nearest the direction of the tension anchor. Hold-down connectors with self-jigging bolt standoffs shall be installed in a manner to permit preloading.
§EBA404 General Requirements for Phased Construction
When the building contains three or more levels, the work specified in this chapter shall be permitted to be done in the following phases. Work shall start with Phase I unless otherwise approved by the code enforcement official. When the building does not contain the conditions shown in any phase, the sequence of retrofit work shall proceed to the next phase in numerical order.
Phase 1 Work: The first phase of the retrofit work shall include the ground floor portion of the wood structure that contains parking or other similar open floor space.
Phase 2 Work: The second phase of the retrofit work shall include walls of any level of wood construction with two or more levels above that are laterally braced with nonconforming structural materials.
Phase 3 Work: The third and final phase of the retrofit work shall include the remaining portions of the building up to, but not including, the top story as specified in §EBA403.2.
§EBA405 Prescriptive Measures for Weak Story
§EBA405.1 Scope: The proposed prescriptive measures provided here are intended to reduce the earthquake vulnerability of the structure and to reduce the possibility of collapse or partial collapse of the building in the event of a moderate to major earthquake.
§EBA405.1.1 Performance: The improved earthquake performance of the structure due to the proposed prescriptive measures varies and is greatly controlled by all of the following: proximity to the fault line; soil type; weight of roof and floor above; quality of existing walls, posts and columns, and their connections to the floor diaphragm; and the quality of construction provided to comply with the prescriptive measures. The implementation of the proposed measures is not intended to improve the earthquake performance of the building above the first story.
§EBA405.1.2 Limitation: The proposed prescriptive measures rely on rotation of the second floor diaphragm to distribute the load between the side and rear wall enclosing the parking area. The owner shall provide access to ensure that the floor diaphragm is of wood structural panel or diagonal sheathing. In the absence of such a verification, a new wood structural panel diaphragm must be applied of minimum thickness of 3/4 inch (19 mm) and with 10d common nails at 6 inches (152 mm) on center.
§EBA405.1.3 Additional Conditions: To qualify for prescriptive measures, the following additional conditions need to be satisfied:
- Diaphragm aspect ratio = 1.5 or less.
- Minimum length of side shear walls = 20 feet (6096 mm) with less than 10% openings.
- Minimum length of rear shear walls = 3/4 of rear wall length with individual walls not having more than 10% openings.
§EBA405.2 Minimum Required Retrofit
§EBA405.2.1 Anchor Bolt Size and Spacing: The anchor bolt size and spacing shall be a minimum of 3/4 inch (19 mm) in diameter at 32 inches (813 mm) on center. Where existing bolts are inadequate, new steel plates bolted to the side of the foundation and nailed to the sill may be used, such as an approved connector.
§EBA405.2.2 Connection to Floor Above: Shear wall top plates shall be connected to blocking or rim joist at upper floor with a minimum of 18-gage galvanized steel angle clips 4-1/2 inches (114 mm) long with 12-8d nails spaced no farther than 16 inches (406 mm) on center, or by equivalent shear transfer methods.
§EBA405.2.3 Shear Wall Sheathing: The shear wall sheathing shall be a minimum of 15/32 inch (11.9 mm) 5-Ply Structural I with 10d nails at 4 inches (102 mm) on center at edges and 12 inches (305 mm) on center at field; blocked all edges with 3 by 4 or larger. Where existing sill plates are less than 3-by thick, place flat 2-by on top of sill between studs, with flat 18-gage galvanized steel clips 4-1/2 inches (114 mm) long with 12-8d nails or 3/8-inch-diameter (9.5 mm) lags through blocking for shear transfer to sill plate. Stagger nailing from wall sheathing between existing sill and new blocking. Anchor new blocking to foundation as specified above.
§EBA405.2.4 Shear Wall Hold-Downs: Shear walls shall be provided with hold-down anchors at each end. Two hold-down anchors are required at intersecting corners. Hold-downs shall be approved connectors with a minimum 5/8-inch-diameter (15.9 mm) threaded rod or other approved anchor with a minimum allowable load of 4,000 pounds (17.8 kN). Anchor embedment in concrete shall not be less than 5 inches (127 mm). Tie-rod systems shall not be less than 5/8 inch (15.9 mm) in diameter unless using high strength cable. Threaded rod or high strength cable elongation shall not exceed 5/8 inch (15.9 mm) using design forces.
§EBA406 Materials of Construction
§EBA406.1 New Materials: All materials approved by this code, including their appropriate allowable stresses and minimum aspect ratios, shall be permitted to meet the requirements of this chapter.
§EBA406.2 Allowable Foundation and Lateral Pressures: Allowable foundation and lateral pressures shall be permitted to use the values from UBC Table 18-I-A. The coefficient of variation of sub grade reaction shall be established by an approved geotechnical engineering report or other approved methods when used in the deflection calculations of embedded vertical elements as required in §EBA403.6.
§EBA406.3 Existing Materials: All existing materials shall be in sound condition and constructed in conformance to this code before they can be used to resist the lateral loads prescribed in this chapter. The verification of existing material conditions and their conformance to these requirements shall be made by physical observation reports, material testing or record drawings as determined by the structural designer and as approved by the code enforcement official.
§EBA406.3.1 Horizontal Wood Diaphragms: Existing horizontal wood diaphragms that require analysis under §EBA403.10 shall be permitted to use Table EBA4-E for their allowable values.
§EBA406.3.2 Wood-Structural-Panel Shear Walls
§EBA406.3.2.1 Allowable Nail Slip Values: When the required drift calculations of §EBA403.11.2.1 rely on the lower slip values for common nails or surfaced dry lumber, their use in construction shall be verified by exposure. The use of box nails and unseasoned lumber may be assumed without exposure. The design value of the box nails shall be assumed to be similar to that of common nails having the same diameter. Verification of surfaced dry lumber shall be by identification conforming to UBC §2340.1.
§EBA406.3.2.2 Plywood Panel Construction: When verification of the existing plywood materials is by use of record drawings alone, the panel construction for plywood shall be assumed to be of three plies. The plywood modulus "G" shall be assumed equal to 50,000 pounds per square inch (345 MPa).
§EBA406.3.3 Existing Wood Framing: Wood framing is permitted to use the design stresses specified in the Building Code of New York State under which the building was constructed or other stress criteria approved by the code enforcement official.
§EBA406.3.4 Structural Steel: All existing structural steel shall be permitted to use the allowable stresses for Grade A36. Existing pipe or tube columns shall be assumed to be of minimum wall thickness unless verified by testing or exposure.
§EBA406.3.5 Strength of Concrete: All existing concrete footings shall be permitted to use the allowable stresses for plain concrete with a compressive strength of 2,000 pounds per square inch (13.8 MPa). The strength of existing concrete with a recorded compressive strength greater than 2,000 pounds per square inch (13.8 MPa) shall be verified by testing, record drawings or department records.
§EBA406.3.6 Existing Sill Plate Anchorage: Existing cast-in-place anchor bolts shall be permitted to use the allowable service loads for bolts with proper embedment when used for shear resistance to lateral loads.
§EBA407 Required Information on Plans
§EBA407.1 General: The plans shall show all necessary dimensions and materials for plan review and construction and shall accurately reflect the results of the engineering investigation and design. Details specific to the actual condition found shall be shown on the drawings to assure installation of all elements required for construction of the necessary complete load path. The plans shall contain a note that states that this retrofit was designed in compliance with the criteria of this chapter.
§EBA407.2 Existing Construction: The plans shall show existing diaphragm and shear wall sheathing and framing materials; fastener type and spacing; diaphragm and shear wall connections; continuity ties; and collector elements. The plans shall also show the portion of the existing materials that needs verification during construction.
§EBA407.3 New Construction
§EBA407.3.1 Foundation Plan Elements: The foundation plan shall include the size, type, location and spacing of all anchor bolts with the required depth of embedment, edge and end distance; the location and size of all columns for braced or moment frames; referenced details for the connection of braced or moment-resisting frames to their footing; and referenced sections for any grade beams and footings.
§EBA407.3.2 Framing Plan Elements: The framing plan shall include the width, location and material of shear walls; the width, location and material of frames; references on details for the column-to-beam connectors, beam-to-wall connections, and shear transfers at floor and roof diaphragms; and the required nailing and length for wall top plate splices.
§EBA407.3.3 Shear Wall Schedule, Notes and Details: Shear walls shall have a referenced schedule on the plans that includes the correct shear wall capacity in pounds per foot (N/m); the required fastener type, length, gauge and head size; and a complete specification for the sheathing material and its thickness. The schedule shall also show the required location of 3-inch (76 mm) nominal or two 2-inch (51 mm) nominal edge members; the spacing of shear transfer elements such as framing anchors or added sill plate nails; the required hold-down with its bolt, screw or nail sizes; and the dimensions, lumber grade and species of the attached framing member.
Notes shall show required edge distance for fasteners on structural wood panels and framing members; required flush nailing at the plywood surface; limits of mechanical penetrations; and the sill plate material assumed in the design. The limits of mechanical penetrations shall also be detailed showing the maximum notching and drilled hole sizes.
§EBA407.3.4 General notes. General notes shall show the requirements for material testing, special inspection, structural observation and the proper installation of newly added materials.
§EBA408 Quality Control
§EBA408.1 Structural Observation: All structures regulated by this chapter require structural observation. The owner shall employ the engineer or architect responsible for the structural design, or another engineer or architect designated by the engineer or architect responsible for the structural design, to perform structural observation as defined in the UBC.
Basic Structural Checklist
Table EBA4-A: Building System
- C - NC - N/A - Load Path: The structure shall contain one complete load path for seismic force effects from any horizontal direction that serves to transfer the inertial forces from the mass to the foundation.
- C - NC - N/A - Weak Story: The strength of the lateral-force-resisting system in any story shall not be less than 80% of the strength in an adjacent story above or below.
- C - NC - N/A -Soft Story: The stiffness of the lateral-force-resisting system in any story shall not be less than 70% of the stiffness in an adjacent story above or below, or less than 80% of the average stiffness of the three stories above or below.
- C - NC - N/A - Vertical Discontinuities: All vertical elements in the lateral-force-resisting systems shall be continuous to the foundation.
- C - NC - N/A - Deterioration of Wood: There shall be no signs of decay, shrinkage, splitting, fire damage or sagging in any of the wood members, and none of the metal accessories shall be deteriorated, broken or loose.
- C - NC - N/A - Wall Anchorage: Exterior concrete or masonry walls shall be anchored for out-of-plane forces at each diaphragm level with steel anchors or straps that are developed into the diaphragm. Straps shall be minimum 7 gage.
Table EBA4-B: Lateral-Force-Resisting System
- C - NC - N/A - Redundancy: The number of lines of shear walls in each principal direction shall be greater than or equal to two.
- C - NC - N/A - Shear Stress Check: The shear stress in the shear walls shall be less than the following values:
- 5-Ply structural panel sheathing: 400 plf (5.8 kN/m)
- 3-Ply structural panel and diagonal sheathing:
- 200 plf (2.9 kN/m)
- Straight sheathing: 80 plf (1.2 kN/m)
- C - NC - N/A - Stucco (Exterior Plaster) Shearwalls: Multistory buildings shall not rely on exterior stucco walls as the primary lateral-force-resisting system.
- C - NC - N/A - Gypsum Wallboard or Plaster Shear Walls: Interior plaster or gypsum wallboard shall not be used as shear walls on buildings over one story in height.
- C - NC - N/A - Narrow Wood Shear Walls: Narrow wood shear walls with an aspect ratio greater than 2:1 for life safety shall not be used to resist lateral forces developed in the building.
- C - NC - N/A - Walls Connected Through Floors: Shear walls shall have interconnection between stories to transfer overturning and shear forces through the floor.
- C - NC - N/A - Hillside Site: For a sloping site greater than 1 vertical in 3 horizontal and with greater than one-half story above the base, the base shear in the downhill direction, including forces from the base-level diaphragm, shall be resisted through primary anchors from diaphragm struts or collectors provided in the base-level framing to the foundation.
- C - NC - N/A - Cripple Walls: All cripple walls below first-floor-level shear walls shall be braced to the foundation with shear elements.
- C - NC - N/A - Openings: Walls with garage doors or other large openings shall be braced with plywood shear walls or shall be supported by adjacent construction through substantial positive ties.
- C - NC - N/A - Hold-Down Anchors: All walls shall have properly constructed hold-down anchors.
1. The Basic Structural Checklist shall be completed prior to completing this Supplemental Structural Checklist.
Table EBA4-C: Connections
- C - NC - N/A - Wood Posts: There shall be a positive connection of wood posts to the foundation.
- C - NC - N/A - Wood Sills: All wood sills shall be bolted to the foundation.
- C - NC - N/A - Girder/Column Connection: There shall be a positive connection between the girder and the column support.
- C - NC - N/A - Wood Sill Bolts: Sill bolts shall be spaced at 6 feet or less, with proper edge distance provided for wood and concrete.
- For SI: 1 foot = 304.8 mm.
1. The Basic Structural Checklist shall be completed prior to completing this Supplemental Structural Checklist.
Table EBA4-D: DIAPHRAGMS
- C - NC - N/A - Diaphragm Continuity: The diaphragms shall not be composed of split-level floors. In wood buildings, the diaphragms shall not have expansion joints.
- C - NC - N/A - Roof Chord Continuity: All chord elements shall be continuous, regardless of changes in roof elevation.
- C - NC - N/A - Straight Sheathing: All straight-sheathed diaphragms shall have aspect ratios less than 2:1.
- C - NC - N/A - Spans: All wood diaphragms with spans greater than 24 feet shall consist of wood structural panels or diagonal sheathing. Wood commercial and industrial buildings may have rod-braced systems.
- C - NC - N/A - Unblocked Diaphragms: All unblocked wood-structural-panel diaphragms shall have horizontal spans less than 40 feet and shall have aspect ratios less than or equal to 4:1.
- For SI: 1 foot = 304.8 mm.
1. The Basic Structural Checklist shall be completed prior to completing this Supplemental Structural Checklist.
Table EBA4-E: Allowable Values for Existing Materials
|Existing Materials or Configurations of Materials
||Allowable Values 14.594 for N/m
|1. Horizontal diaphragms|
|1.1 Roofs with straight sheathing and roofing applied directly to the sheathing||100 pounds per foot for seismic shear|
|1.2 Roofs with diagonal sheathing and roofing applied directly to the sheathing
||250 pounds per foot for seismic shear|
|1.3 Floors with straight tongue-and-groove sheathing
||100 pounds per foot for seismic shear|
|1.4 Floors with straight sheathing and finished wood flooring with board edges offset or perpendicular
||500 pounds per foot for seismic shear|
|1.5 Floors with diagonal sheathing and finished||600 pounds per foot for seismic shear|
|2. Crosswalls||Per side:|
|2.1 Plaster on wood or metal lath||200 pounds per foot for seismic shear|
|2.2 Plaster on gypsum lath||175 pounds per foot for seismic shear|
|2.3 Gypsum wallboard, unblocked edges||75 pounds per foot for seismic shear|
|2.4 Gypsum wallboard, blocked edges||125 pounds per foot for seismic shear|
|3. Existing footings, wood framing, structural steel and reinforced steel
|3.1 Plain concrete footings||f'c = 1,500 psi (10.3 MPa) unless otherwise shown by tests
|3.2 Douglas fir wood||Allowable stress same as D.F. Number 14|
|3.3 Reinforcing steel||f's = 18,000 psi (124 MPa) maximum|
|3.4 Structural steel||f's = 20,000 psi (138 MPa) maximum|
For SI: 1 foot = 304.8 mm.
- Material must be sound and in good condition.
- A one-third increase in allowable stress is not allowed.
- Shear values of these materials may be combined, except the total combined value shall not exceed 300 pounds per foot.
- Stresses given may be increased for combinations of loads as specified in the Building Code.