Wood Solutions Fair, 2014, Toronto

Transcription

1 Overview of Changes to CSA O & Structural Design Provisions for Mid-Rise in OBC Wood Solutions Fair, 2014, Toronto Jasmine Wang, Ph.D., P.Eng. Canadian Wood Council Copyright Materials This presentation is protected by US and International Copyright laws. Reproduction, distribution, display and use of the presentation without written permission of the speaker is prohibited. Canadian Wood Council

2 Program Education Credit Information The Canadian Wood Council is a Registered Provider with the American Institute of Architects. This course meets Continuing Education System requirements for one Learning Unit. Credit earned on completion of this program will be reported to CES Records for AIA members who provided their member number during the online registration. This course also qualifies as Structured Learning with OAA. Certificates of Completion for OAA members, and all other delegates, will be ed after the event. We will also report participation to the Engineering Institute of Canada on behalf of any engineers who requested their participation be recorded. This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. The same is true for the OAA and EIC. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation. Outline Mid-rise Related Changes in Building Codes Overview of Changes to CSA O Technical Resources for Engineering Design for Mid-Rise Photo credit: Steven Street, WoodWORKS!ON 2

3 Mid-rise Related Changes in Building Codes National (proposed) and Provincial building codes allow wood construction of up to 6 storeys Firstly adopted in amendment to 2006 BCBC in 2009 Proposed for 2015 NBCC Different fire provisions Essentially the same structural/seismic provisions but with broader scope Recently adopted by OBC Different fire requirements The same structural/seismic provisions as NBCC 2015 Mid-rise Related Changes in NBCC 2015 & OBC - Structural/Seismic Design Aspects Restrictions on irregularities (Sentence (4)) For medium and high seismic zones (I E F a S a (0.2)>=0.35), Type 4 or 5 Irregularities are not allowed in 5 or 6 storeys of continuous wood construction (a) (b) (a) offset: Shear wall location moves (b) lateral stiffness: Shear wall has more openings in a storey below 3

4 Mid-rise Related Changes in NBCC 2015 & OBC - Structural/Seismic Design Aspects Increased static design force level (Sentence (11)) Only for seismic design; If the empirical code period is used, no need to increase the base shear When the fundamental period is determined using established methods of mechanics other than the empirical code period, the static base shear shall be increased by 20%, but need not exceed the maximum. Increased dynamic design force level (Sentence (12)) Only for seismic design; Having a fundamental period as determined using established methods of mechanics other than the empirical code period, the base shear shall be the larger of dynamic design force and 100% of static design force. Outline Mid-rise Related Changes in Building Codes Overview of Changes to CSA O Technical Resources for Engineering Design for Mid-Rise 4

5 Overview of CSA O Changes Published in July 2014 (PDF format) Mid-rise related changes Shear resistance of shearwalls and diaphragms Shear and bending moment resistance of glulam Withdrawal resistance of lag screws Other changes Mid-Rise Related Changes in CSA O Requirements for Anticipated Building Movements due to Moisture Content Change Requirements for Calculation of Deflection for Multi-Storey Shearwalls Requirements for Shearwalls Using Gypsum Wallboard Shear Resistance of High Capacity Shearwalls and Diaphragms 5

6 Requirements for Anticipated Building Movements due to Moisture Content Change O Clause Building movements due to moisture content change O Clause A Shrinkage and swelling of wood members Information on the effect of shrinkage on differential movements and overall lateral drift calculations & how to mitigate shrinkage Information on areas that should be paid attention to: Information on how to estimate shrinkage Requirements for Anticipated Building Movements due to MC Change Estimate of shrinkage In multi-storey wood frame buildings Shrinkage occurs mainly in horizontal members Cumulative shrinkage in studs (parallel to grain) may be considerable in 5 & 6-storey buildings Examples: Table 1: Estimated vertical movement in a 4-storey building (mm) Table 2: Estimated vertical movement in a 5-storey building (mm) 6

7 Shrinkage in multi-storey wood buildings Shrinkage can contribute to overall lateral drift Interstorey drift ratio may become the governing factor 2.5% for earthquake design (normal occupancy) 0.2% for wind design Can be mitigated by Using shrinkage compensators, and Using material subjected to less dimensional change CTUD TUD Shrinkage Take-Up Devices (Source: Simpson Strong-Tie) Requirements for Calculation of Deflection for Multi- Storey Shearwalls Current equation in CSA O86-09 applies to single-storey shearwall segments Clause (CSA O ) Deflections of shearwalls In the calculation of deflection for multi-storey shearwalls, multi-storey effects shall be considered Note: See Clause A for additional information on multi-storey effects Clause A Deflection of shearwalls in multi-storey buildings A purely mechanics-based approach; Appropriate for a typical shearwall cantilevered from its base and stacked for the full height; Comprised of interstorey drift due to bending, panel shear, nail slip and vertical elongation of the wall anchorage system; Takes into account the cumulative rotational effects from the storeys below; The methodology is the same as the one given in APEGBC Bulletin. 7

8 Deflection of single-storey shearwalls v = maximum shear force per unit length due to specified lateral loads He s shearwall segment height n = nail deformation for a particular v = maximum load Hshear s per = shearwall nail force (Table per segment 8.2 unit of length WDM) height due to specified lateral loads A H cross-sectional area of chord members s = shearwall segment height H E = modulus of elasticity of chords s = shearwall L s segment = length of height shearwall segment L s = length of shearwall segment B v = shear-through-thickness d a = total vertical rigidity elongation (Tables of the 7.3 wall A~C anchorage of CSA O86) system Deflection of shearwalls in multi-storey buildings Bending Anchorage system elongation 8

9 Deflection of shearwalls in multi-storey buildings Fastener slip, e n, for shearwall and diagram deflection calculation (Clause A.11.7 O ) e n table was replaced with one equation 1. For nails used in wood-based sheathing with dry lumber: 2. Multiply by 2 for green lumber 3. e n may be taken as 0.76 mm for GWB with dry lumber Requirements for Shearwalls Using Gypsum Wallboard O Clause Seismic design requirements for shearwalls using gypsum wallboard Gypsum wallboard shall not be considered to provide lateral resistance when the interstorey drift ratio exceeds 1%. For buildings higher than 4 storeys the contribution of the gypsum wallboard shall not be accounted for in seismic resistance. Different from APEGBC Bulletin O Clause Load bearing walls constructed with gypsum wallboard only When interstorey drift exceeds 1% the design should be based on the assumption that GWB provides no lateral support to studs. Alternatively a secondary blocking system shall be used 9

10 Shear Resistance of Shear Resistance of High Capacity Shearwalls and Diaphragms Clause , & of CSA O : A mechanics-based approach was adopted to calculate the shear resistance of shearwalls and diaphragms Makes it possible for designers to design for high capacity shearwalls & diaphragms Mid-panel shearwalls Diaphragms with multiple rows of fasteners Overview of CSA O Changes Published in July 2014 (PDF format) Mid-rise related changes Shear resistance of shearwalls and diaphragms Shear and bending moment resistance of glulam Withdrawal resistance of lag screws Other changes 10

11 Shear resistance of shearwalls and diaphragms Tabulated values in CSA O86-09 Based on test data Limited to assemblies constructed with dimension lumber, common nail and sheathing of discrete thicknesses A mechanics based approach was adopted in CSA O Shear resistance of shearwall/diaphragm sheathed with wood-based structural panels governed by the smaller of: Sheathing-to-framing connection For seismic design nail shall be designed to fail in the modes where plastic hinge(s) form to ensure sufficient ductility Sheathing panel buckling Advantages More engineering sense More flexibility in terms of the assemblies High capacity shearwalls and diaphragms: mid-panel shearwalls and diaphragms with multiple rows of fasteners Shear resistance of shearwalls and diaphragms Sheathing-to-framing connection Sheathing panel buckling Seismic design Selection tables will be provided in WDM

12 High capacity shearwalls and diaphragms Mid-panel shearwalls double shear Diaphragms with multiple rows of fasteners Stud or Plate Sheathing n s = 2 89 mm 38 mm 38 mm Grain direction Stud or Plate Nail in single shear Nail in double shear Overview of CSA O Changes Published in July 2014 (PDF format) Mid-rise related changes Shear resistance of shearwalls and diaphragms Shear and bending moment resistance of glulam Withdrawal resistance of lag screws Other changes 12

13 Bending Moment Resistance of Glulam Design provisions in CSA O86-09 Design provisions in CSA O Shear resistance of glulam with tension side notch at supports Design provisions in CSA O86-09 (Clause ) Design provisions in CSA O (Clause ) Longitudinal shear resistance of residual member above notch Tension side notch not exceeding 0.25d Within a distance d from the inner edge of the closest support to the furthest edge of the notch No reduction in shear resistance calculated using gross cross sectional area Fracture shear resistance at notch 13

14 Overview of CSA O Changes Published in July 2014 (PDF format) Mid-rise related changes Shear resistance of shearwalls and diaphragms Shear and bending moment resistance of glulam Withdrawal resistance of lag screws Other changes Withdrawal resistance of lag screws Design provisions in O86-09 (Clause ) Design provisions in O86-14 (Clause ) Based on the density of various wood products Apply not only to lag screws but also self-drilling fasteners compliant to appropriate product standards or product evaluation reports 14

15 Overview of CSA O Changes Published in July 2014 (PDF format) Mid-rise related changes Shear resistance of shearwalls and diaphragms Shear and bending moment resistance of glulam Withdrawal resistance of lag screws Other changes Other changes Reduction in the concentrated loaded area on roof deck Commentary information on plank decking and structural sheathing Requirements for lateral brace forces for metal-plate-connected wood truss compression webs (Clause 5.5) 1.25% of the axial compressive force in the member Newly added finger-joined lumber grade (Clause 6.2.3) NLGA SPS 4 Dry Use Only lumber Metal-plate-connected trusses application 15

16 Other changes Reaction resistance for I-Joist (Clause & ) Strength resistance of truss plates (Clause 16.4) Revised ultimate lateral resistance of teeth, tensile, shear and lateral slip resistance Allowed in SCL to SCL connections or sawn lumber to SCL connections Allowing lag screws and wood screws for joist hanger connections (Clause 12.10) Annex B: Fire resistance of large cross-section wood elements Outline Mid-rise Related Changes in Building Codes Overview of Changes to CSA O Technical Resources for Engineering Design for Mid-Rise 16

17 Technical Resources for Engineering Design for Mid-Rise Wood Design Manual 2015 (to be published in late 2015) Mid-Rise Wood Frame Construction Handbook (in process) APEGBC Bulletin NBC Structural Commentary Technical Resources for Engineering Design for Mid-Rise Fact Sheets - Vertical Movement in Wood Platform Frame Structures Basics Movement Prediction Design and Detailing Solutions Diaphragm Design Diaphragm Flexibility Design Example: Wood Diaphragm on Reinforced CMU Shearwalls Design Example: Design for Openings in Wood Diaphragm Design Example: Wood Diaphragm Using Envelope Method Design of Multi-Storey Wood-Based Shearwalls: Linear Dynamic Analysis & Mechanics-Based Approach Linear Dynamic Analysis for Wood-Based Shearwalls and Podium Structures A Mechanics-Based Approach for Determining Deflections of Stacked Multi-Storey Wood-Based Shearwalls Design Example: Design of Stacked Multi-Storey Wood-Based Shearwalls Using a Mechanics-Based Approach Design of Wood Frame and Podium Structures Using Linear Dynamic Analysis (WCTE 2014 Proceedings) 17

18 Shrinkage Compensator Video Source: Brent Bunting, Simpson Strong-Tie Questions/ Comments? This concludes the: American Institute of Architects Ontario Association of Architects Engineering Institute of Canada Continuing Education Systems Program Overview of Changes to CSA O & Mid-Rise Related Changes in OBC Canadian Wood Council 18