Cross-Laminated Timber (CLT) in California:

Transcription

1 Cross-Laminated Timber (CLT) in California: Guidelines, Testing and Recommendations Erik Kneer, SE, LEED AP BD+C Disclaimer: This presentation was developed by a third party and is not funded by WoodWorks or the Softwood Lumber Board. November 7, 2018

2 The Wood Products Council is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES), Provider #G516. Credit(s) earned on completion of this course will be reported to AIA CESfor AIA members. Certificates of Completion for both AIA members and non-aia members are available upon request. This course is registered with 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. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation. CLT In California November 7,

3 Course Description The 2016 California Building Code prescriptively recognizes cross-laminated timber (CLT) as an acceptable building material in construction types III, IV and V. However, its use as part of a seismic force resisting system either as a diaphragm or shear wall is not yet codified. This panel session will focus on three topics key to the design, review and approval of CLT buildings. First, it will raise awareness regarding a process guideline document developed jointly by the California Building Officials (CALBO) and the Structural Engineers Association of California (SEAOC) in an effort to streamline mass timber project review and approval. Next it will discuss shake table testing conducted at the University of California at San Diego to investigate several resilient CLT shear wall configurations, including a post-tensioned rocking wall system and a repairable rocking wall system. Finally, it will discuss design processes and resources specific to the use of CLT in diaphragms. CLT In California November 7,

4 Learning Objectives 1. Develop an understanding of the process recommendations in the California Mass Timber Reference Guide developed jointly by CALBO and SEAOC to achieve a consistent and streamlined approach to mass timber project review and approval. 2. Describe a recently completed full-scale two-story mass timber building shake table test and understand the potential impacts these tests can have on building approvals. 3. Discuss how mass timber buildings with a resilient rocking wall system can minimize owner loss and repair time even after major earthquakes. 4. Examine the use of CLT in diaphragm applications and review design options and recommendations for seismic resistance. CLT In California November 7,

5 CLT in California Baby steps for mass timber in CA Population 39.5M Completed buildings using CLT 2013: : : : : 3 + more in progress Buildings using CLT for gravity & lateral system 2 Plumas County Biomass Building Tahoe Expedition Academy CLT In California November 7,

6 CLT in California Pre Jan 1 st All CLT required alternate means & methods request (AMMR). Post Jan 1 st CLT allowed for gravity load applications only. - Use in lateral systems (walls & diaphragms) requires AMMR. - Limited cases study precedents in CA to draw from. Many more steps to come. CLT In California November 7,

7 Making Mass Timber a Reality in CA Gravity:Good understanding of the mechanics and strength Seismic: Undergoing research and development Fire safety:good understanding of risks and safety measures CLT In California November 7,

8 Making Mass Timber a Reality in CA CLT In California November 7,

9 Mass Timber in the Code Product Performance Standard for CLT Wood Structural Design Standard with CLT 2015 International Building Code 2016 California Building Code CLT In California November 7,

10 Mass Timber in the Code CLT In California November 7,

11 Mass Timber in the Code CLT In California November 7,

12 Mass Timber in the Code CLT is generally available for use in Type III, IV and V construction. IBC 2015 Chapter 6 Defines Dimensions of CLT to qualify as Heavy Timber (Type IV Construction) 6 Walls 4 Floors 3 Roofs Non Fire-Retardant Treated CLT allowed in Exterior Walls of Type IV construction in many conditions. (IBC ) The Heavy Timber construction size requirements only apply to Type IV Construction CLT In California November 7,

13 Mass Timber in the Code National Design Specification for Wood Construction 2015 Edition CLT In California November 7,

14 Mass Timber in the Code CLT In California November 7,

15 Mass Timber in the Code Current (& 2019) Code Approach TypeIII, IV or V Construction Height:UpTO 85 AND 6 STORIES (COMMERCIAL) UP TO 85 AND 5 STORIES ( RESIDENTIAL) CAN USE PODIUM WITHIN 85 HEIGHT AREA: APPROX. 108,000 SF/FLOOR (COMMERCIAL) APPROX. 61,500 SF/FLOOR (RESIDENTIAL) HIGHER OR LARGER MASS TIMBER BUILDINGS WILL NEED TO BE SUBJECT TO AMMR (EQUIVALENT TO TYPE I-B) HEIGHT: UP TO 180 (12 STORIES) AREA: UNLIMITED (COMMERCIAL), 72,000 SF/FLOOR (RESIDENTIAL) OTHER: SPRINKLERS, 2-HOUR RATING, PARTIALLY COVERED CLT USE IBC 2021 PROVISIONS AS A BASIS OF AMMR CLT In California November 7,

16 Mass Timber in the Code CLT In California November 7,

17 Making CLT a Reality Prescriptive: Hybrid System CLT In California Performance-Based: Pure CLT System November 7,

18 Making Mass Timber a Reality Available solutions under the 2016-CBC OPTION #1 -PRESCRIPTIVE APPROACH (HYBRID SYSTEM) Construction: Gravity system:cltfloor panels, could use bearing-walls if not part of the seismic system. Seismic system: One recognized by the code (concrete shear walls, steel braced frames, etc.). Diaphragms consist of the CLTpanels (jurisdictions may force use of nailed wood sheathing or reinforced concrete topping confirm early). Notes: Normal design and permitting process. Structural height limitations of conventional lateral systems allow for high-rise construction. OPTION #2 - PERFORMANCE BASED APPROACH (PURE CLT SYSTEM) Construction: Gravity system:cltin form of floor panels and bearing walls. Seismic system:cltshear walls justified through testing and complex analysis (see next slide). Notes: Higher design cost due to increased engineering efforts. Longer design and permitting timeframe. Construction savings (material & labor) have to be compared to the cost and schedule impact related to testing, design, and permitting. CLT In California November 7,

19 Making Mass Timber a Reality Introducing: CA Mass Timber Reference Guide Multi-disciplinary working group led by SEAOC in collaboration with CALBO Process Guide for Designers and Building Officials Remove some of the uncertainty in approvals Consistent approach across jurisdictions COMING SOON! CLT In California November 7,

20 Making Mass Timber a Reality Project Examples Plumas Health & Human Services Biomass Boiler Building Client: High Sierra Community Energy Development Corporation Architect: ALMGM Location: Quincy, Plumas County, CA Project Description: new 1-story mechanical building Gross SF: 2,400 SF Construction Type: IV-Heavy Timber Structural System -Gravity: CLT roof supported by CLT bearing walls. Structural System Lateral:CLT diaphragm + CLT shear walls. First all CLT building in CA CLT In California November 7,

21 Making Mass Timber a Reality Project Examples CLT In California November 7,

22 Making Mass Timber a Reality Project Examples Brentwood Public Library Architect: Fog Studio Contractor: Lathrop Construction Location: Brentwood CA Project Description: new 2-story Library with 1- story Community Room seismically separated Gross SF: 22,529 SF Construction Type: V-B-Sprinklered Structural System -Gravity: CLT roof, CLT + conc. topping suspended floor. Both supported by steel beams and columns. Structural System Lateral:Steel Moment Frames CLT In California November 7,

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25 Making Mass Timber a Reality Project Examples Corporate Campus, Mountain View CA Architect: WRNS Studio Contractor: Ruldolph& Sletten Location: Mountain View, CA Project Description: Corporate Campus Predominately office use with assembly uses Accessible green roof over all new building structure Gross SF: 645,000 SF office + 505,000 SF structured parking Construction Type: III-B-Sprinklered Structural System Gravity: Composite CLT + conc. topping floor, steel beams w/glulam columns Structural System Lateral: Concrete shear wall Will be the largest (by SF) mass timber building in NA CLT In California November 7,

26 Making Mass Timber a Reality Project Examples Corporate Campus, Mountain View CA Regulatory Approvals - Type III-B. Required AMMR variance as a mall concept. - CBC conforming lateral system. Concrete shear walls. - Composite CLT + conc. topping slab floors. CLT In California November 7,

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28 CLT In California November 7,

29 Making Mass Timber a Reality Project Examples Corporate Campus, Mountain View CA Local Construction Industry Norms - Responsibility for erection? Wood + Steel + Concrete frame - Construction detailing to suit erection efficiency? cost? aesthetics? CLT In California November 7,

30 In the Works.. Performing Arts Center, Truckee CA CLT In California November 7,

31 In the Works.. Performing Arts Center, Truckee CA CLT In California November 7,

32 Questions? This concludes The American Institute of Architects Continuing Education Systems Course Erik Kneer: November 7, 2018