aia 2016 - the momentum of tall wood buildings
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Overview
• Defining Tall Wood
• Precedence/Context
• Motivation and Benefit
• Execution Under U.S. Code
Overview
• Defining Tall Wood
• Precedence/Context
• Motivation and Benefit
• Execution Under U.S. Code
The momentum of tall wood really started with an disrupter of sorts. Technology has been the great disrupter of the times, hasn’t it? It is no different in the building industry. Advances in materials and manufacturing science has really opened the door for timber products. The disruptive technology in this case is the emergence of Mass Timber building Systems.
Momentum Starts With a Disruption
Some of you may have heard the term mass timber used. While mass timber doesn’t have an official definition, it’s most easily described as construction consisting of solid timber panels. Everyone is familiar with traditional wood construction methods of Post and Beam/Heavy Timber and light frame. Post and beam was a vertical load carrying system of large solid sawn lumber elements as used in floor deck, joist/beam and column and evolved to include glue laminated beams as well. Light frame came about as a very material efficient system that enable smaller wood elements to be used providing both vertical and lateral load resistance. Modern light frame buildings use a whole host of engineered technologies like I-joists, LVL, OSB, plywood, etc. Mass timber building systems make use of small dimension lumber but on a much more “massive” scale providing much higher structural capacity and the advantages that come with heavy timber sizing in regards to fire.
Mass Timber Building Systems
You are familiar with a variety of engineered lumber products such as glulam, LVL, PSL, LSL. These products have been limited to single element beam like applications. In mass timber buildings we use these technologies a little differently. We are using them as panels. These panels can be used horizontally or vertically and provide both the vertical and lateral load resisting capabilities.
Other mass timber systems include cross laminated timber with orthogonal layers of 2x material layered and glued or mechanically fastened together, nail laminated timber and a whole host of timber concrete composites. The advent of CLT is what opened the eyes of designers and industry alike to the potential of timber panels with multi-directional capacity.
NLT isn’t really new either. 2x’s nailed together in the vertical orientation was a common decking system in historical post and beam construction and is making a comeback as a solid timber panel system being prefabricated 8’ wide sections..
Mass Timber Building Systems
Images: StructureCraft
Here is an example of mass timber building; the Redstone Arsenal Hotel in Alabama. This is an all CLT building; floors, exterior walls, floors/roofs and even shafts. As a 4 story Type III building, this is an application that can be done under the current prescriptive building code.
When you consider that most wood structures are less than 3 stories tall, this could be called a tall timber building although it’s probably not really what most people think of when they think of tall timber.
2 0 1 5
REDST O NE ARSENAL CANDLEW O O D
SUIT ES HO T EL
HUNSTVILLE, AL
Design/Build: LendLeaseImages: LendLease
This might be a more representative example of what is often referred to as tall timber. This particular example is a 7-story office building under construction in Minneapolis. This project uses NLT floors with glulam beams and columns and is an example of a timber hybrid using a combination of mass timber and post and beam systems. T3 demonstrates maximization of current code allowances using a prescribed 6 story office occupancy maximum for Type IV construction over a single story Type IA concrete podium, all under the 85’ height limit.
Tall timber is a term that includes both code compliant mid-rise structures such as this as well as high-rise structures that are beyond code.
T3 (Timber/Technology/Transit), Minneapolis, MN• Concept at this point, will know in spring 2015 if they are building it• Surface parking • Hines development unveiled plans for new office building• 7 stories• 210 K sf• 1s t story concrete• Solid wood core
U N D E R C O N S T R U C T I O N
T 3 O F F ICE
MINNEAPOLIS, MN
Architect: Michael GreenImages: StructureCraft, MGA
There have been several published structural concepts for full timber high rise buildings that explore the use of these mass timber systems and can be very useful in understanding how this could be possible.
If people are contemplating 20-40 stories of mass timber construction, it might change the way you feel about doing 6.
High-Rise Timber Studies
• Preliminary Findings
– Cost with “surface” CLT opportunities
$0
$10
$20
$30
$40
$50
Wood Concrete Modular CLT
65'
85'
125'
Modular CLT
Source: Sellen Construction
Overview
• Defining Tall Wood
• Precedence/Context
• Motivation and Benefit
• Execution Under U.S. Code
We built 9 stories of wood in the US a hundred years ago. Butler Bros building in Minneapolis, Minn. was a 500,000 sf warehouse originally housing the Butler Bros mail order business. Since then has been converted into a mixed use building with both office and retail.
These relics of the 18th century exist all over the North America; in Boston, San Francisco, Seattle, Vancouver and Toronto; in good condition and in some adaptive reuse application converted from warehouse or factory.
Heavy timber post and beam construction provided the 300 pound per square foot loading requirements of the warehouse. Precut and put together on a module measuring approximately 14' by 16'. The columns which receive the beams with cast iron brackets, gradually diminish in size from 24" square on the ground floor to a spindly 9" on the ninth floor.
1 9 0 6
BUT LER SQ UARE,
MINNEAPOLIS, MN
The mass timber technologies have sent a ripple into the world of construction. We have been watching the ripple effect growing in Europe for almost the past 10 years.
Disruption Causes a Ripple
22
8 storey prototype built in Austria and studies underway for several others in US & Germany.
Lifecycle Tower 2008 - Austria
23
45 x 30m footprint8.1m or 9.45m span from core to perimeter for multi-usePerimeter wood cols at 2.7m (to fit in with 1.35 grid for mixed use dev); 480 x 250
Structure and Fire Testing
25
In addition, the facade has been brought to site in 12m-long units including insulation, framing, plasterboard and windows with only the recycled metal cladding added to the elevations on site. Al rainscreen installed on site.
LCT One - Prefabrication
26
The inclusion of the various prefabricated elements has resulted in a construction process with a claimed reduction of one half in resource use through constructional optimisation and claimed reduction in weight of 30% over a purely reinforced concrete structure. Most remarkably the floors were assembled by a site team of five workers at a speed of one floor per day.
LCT One – Construction
US Tall Wood Competition
• Originally a $2 million Project Competition
• So many high quality submissions resulted in 2 projects awarded $1.5 million each
• Funding provided by joint effort between Softwood Lumber Board, Binational Softwood Lumber Council and USDA
• Learn more at rethinkwood.com (LINK HERE)
Framework: An Urban + Rural Ecology
Beneficial State Bancorp will provide site control to real estate developer project, affordable housing investor Home Forward, and LEVER Architecture, for the proposed Framework as a redevelopment of their Pearl District property in Portland, Oregon. The 12-story urban + rural
ecological project is to be constructed primarily of cross-laminated timber (CLT) and will support a distinct blend of functions including street-level retail, office, workforce housing and community space. The main community space is designed to include a public Tall Wood Exhibit,
featuring resources related to the realization and design of the building.
“We consider Framework to be a totally transformative, mission-driven project that will promote social justice,
environmental well-being and economic opportunity at the building, regional and national levels,” said Kat Taylor, Pres ident, Beneficial State Bancorp, the landowner of the project s ite.
“The relationship of our ci ties to our rural communities, what we call ‘forest to frame,’ is strengthened by Framework,” added Tom Cody, Principal, project^. “On a national scale this project will be catalytic, leading to more ta l l wood buildings, driving more wood products and wood product innovation, and boosting rural economic development.”
Tall Wood Winner – Portland, OR
Framework: An Urban + Rural Ecology
Location: Pearl District, Portland, OR
Height: 130’ / 12 stories
Total Building Area: 90,000 square feet
Building Uses: Ground floor retail; 5 office
floors; 5 apartment floors; rooftop amenity
Materials: Cross laminated timber floors and
lateral force resisting system; glued laminated
beams and columns
Projected Completion Date: December 2017
OWNER: Beneficial State Bancorp
ARCHITECT: LEVER Architecture
ENGINEERS: Arup, KPFF Consulting
Engineers and PAE Consulting Engineers
475 West 18th: Setting the Stage For Innovation, Engineering and Architecture130-134 Holdings LLC, in partnership with Spiritos Properties, SHoP Architects, Arup, IcorAssociates, and environmental consultancy Atelier Ten, proposed 475 West 18th as a transformative and sustainable prototype for the design and construction industry,
demonstrating an innovative approach to going beyond a limited palette of materials and systems for high-rise construction. Expanding the palette with wood, a locally sourced and renewable material, provides a low-carbon, more economically sound building solution.
475 West 18th’s extensive use of wood structural elements and other wood products allows
the team to set ambitious sustainability targets in the building's design, construction, and operation. By combining aggressive load reduction with energy efficient systems, the project team anticipates reducing overall energy consumption by at least 50 percent relative to current energy codes. It will also target LEED Platinum certification, as well as pursue higher levels of sustainability not captured in the LEED system.
“By choosing to develop a timber building, we hope to pave the way for a new method of urban construction that is ecologically conscious and supportive of rural economies,” said Erica Spiritos of Spiritos Properties. “Rooted in the forests and erected in the city, this building is a celebration of habitats that are at once ancient and cutting edge, interconnected and
individual, natural and technological.”
“We are delighted to be developing this tall timber building in New York City, which has led the world in urban design and engineering throughout the last century,” said Jonathan Ghassemi, on behalf of 130-134 Holdings LLC. “We are confident that this project will once again position
New York to serve as a leader in a new generation of sustainable building methods during the 21st century and beyond.”
Tall Wood Winner – New York, NY
475 West 18th: Setting the Stage for
Innovation, Engineering and Architecture
Location: West Chelsea, Manhattan, NY
Height: 120’ / 10 stories
Total Building Area: 50,000 square feet
Building Uses: Residential condominium
with ground floor commercial space
Materials: Mass timber columns, beams,
shear walls and floors
Projected Construction Start Date: Fall
2016
OWNER: 130-134 Holdings LLC
ARCHITECT: SHoP Architects
ENGINEER: Arup and Icor Consulting
Engineers
Source: ArupSource: LEVER Architecture
Framework,
Portland, OR
130-134
Holdings, NYC-134
Holdings, NYC
Overview
• Defining Tall Wood
• Precedence/Context
• Motivation and Benefit
• Execution Under U.S. Code
Based on research done by Perkins+Will studying several of the European Tall Wood projects, it was found that there were some common motivators for owners and designers for these projects.
Tall Wood Motivators
• Market Leadership
• Carbon Reduction
• Energy Performance
Primary Motivators
• Structural Performance
• Light weight
• Speed of Construction
• Aesthetic
Secondary
Motivators
Sky - Believe in Better BuildingOwner: British Sky Broadcasting Group
Architect: Arup Associates
Structural: Arup Associates
Contractor: Mace
Structural Frame Supply: B&K Structures
CLT Supply: Binderholz
Source: Simon Kennedy
• 1st UK multi-storey timber commercial office• 43,000 sq ft• Glulam frame; CLT slabs & shear walls• Timber cassette façade panels (passivhaus)
Sky - Believe in Better Building
BSkyB:3 months Design11 months ConstructionCLT Slabs install: 5300 – 8600 sq ft/week
ScheduleTraditional Approach:7 months Design21 months ConstructionRC Slab install:3200 – 4300 sq ft/week
Comparison of Traditional approach Vs
BIBB.
• Glulam Frame starts 3 March and will
complete in 7 weeks.
• Timber cassette cladding will follow two
weeks behind frame, completing in 7
weeks.
• Building will be 70% weather-tight in 8
weeks – temporary membrane attached to
north elevation to allow fit-out to start in
parallel with Glazing
• Fit-out double-shifts.
The US is 100 million acres, of which 33 million acres is forested.
Dispelling Myths about Wood ProductsUS Forest Lands
U.S. Forest Land
Forest Area in the United States
1630-2007
1045
759 760 756 761 744 738 747 749 751
0
200
400
600
800
1000
1200
1630 1907 1938 1953 1963 1977 1987 1997 2002 2007
Tho
usa
nd
Acr
es
Source: USDA-Forest Service, General Technical Report WO-78. (2009).
103.7 128.3 163 190 214.3 217.6
148.5174.1
223.4244.6
256.4 268
363.7363.2
346.7347
365.1 370.5
0
100
200
300
400
500
600
700
800
900
1953 1963 1977 1987 1997 2002
Inve
nto
ry (b
illio
n cu
bic
fee
t)
U.S. Timber Volume on Timber Land
North South West
U.S. Forest Land
Source: USDA-Forest Service, US Forest Resource Facts and Historical Trends FS-801. (2004).
At least 6-7 million acres of productive forestland are in need of forest health and/or fuels reduction treatments.
Western U.S. Wild Fire Epidemic
• Fire readiness and
suppression has
gone from 20% of
the FS budget in
2001 to 52% in
2015.
• It is not uncommon
to spend $1 million
per hour fighting
fires.
Source: US Forest Service –http://www.fs.fed.us/about-agency/budget-performance/cost-fire-operations
Insect and Disease Risk Map
Inter-Mountain West Insect Devastation
Source: IDS- Insect and Disease Survey USDA Forest Health Protection
Dramatic Potential for Change
100% 41%
Standard Materials
Source: Timber Tower Research Project, Skidmore, Owings and Merrill, May 2013
Timber Hybrid Prototype
Reinforced Concrete Benchmark
Overview
• Defining Tall Wood
• Precedence/Context
• Motivation and Benefit
• Execution Under U.S. Code
– Acoustics
– Structure
– Fire
Acoustic Testing – Floor Assembly
Floor Assembly • Carpet • 3/16” Acoustic mat
sound deadening layer
• ¾” Gypsum concrete underlayment
• 5 ply CLT• 5/8” gypsum board• Resilient channel• Rockwool insulation• 5/8” Gypsum Board
Acoustic Testing – Floor Assembly
Source: Graphic provided by ARUP, CLT data provided by FPInnovations
Heavy Timber Buckling-Restrained Brace
© Arup North America Ltd. Distribution and Reproduction By Permission Only
HTBRB Specimen Exploded View
CNC Wood Fabrication
HTBRB Specimen Cross Section
Fully Threaded Screws
Heavy Timber Buckling-Restrained Brace
So what can you achieve in terms of heights for Type III and Type V buildings? This table summaries the possibilities using our more typical occupancies and starting with allowances in Table 503 and expanding those to what is allowed with an NFPA 13 sprinkler system.
Building Heights and Stories by Building Type
With NFPA 13 Sprinklers
Occupancy
IIIA IV VA
85 ft 85 ft 70 ft
R-1/R-2/R-4 5 5 4
A-2/A-3 4 4 3
B 6 6 4
M 5 5 4
S-2 5 6 5
S-1 4 5 4
Summary of IBC Maximum Heights
**ASCE7 12.2-1 limits wood shear wall seismic systems to 65’ in height in SDC D,E,F
Expanding Stories with Podium
IBC Provisions for Mixed-Use podium have been evolving.
IBC 2006 2009 2012 2015
Section 509.2 509.2 510.2
Upper
Occupancy
A, B, M, R or S
Lower
Occupancy
S-2
Parking
A, B, M, R or S-2
Parking
Any
Except H
Podium
Height
1 Story Multi-
Story
2015 IBC will allow multiple podium stories above grade.
AWC conducted a very successful ASTM E119 fire endurance test on CLT wall at NGC Testing Services in Buffalo, NY to substantiate the inclusion of CLT in the building code and include it for 2-hour fire resistive rated assembly. The test was successful for 3 hours and 6 minutes, far outlasting the 2-hour goal. Chapter 16 of the National Design Specification NDS also provides fire design calculations (char rate) for exposed wood members requiring up to a 2-hour rating.
Fire Test Results
ASTM E119 Fire Endurance Test
• 5-Ply CLT (6-7/8” thick)
• 5/8” Type X GWB each side
• 2 hour target
• Actual 3 hours 6 minutes
2015 NDS Chapter 16
includes char rates for
CLT to achieve up to 2
hour fire rating
Approved fire rated assemblies are an important role in selecting
building framing and finishing systems. It is increasingly difficult to find tested fire assemblies that meet the building’s needs from other perspectives, such as acoustics, energy compliance, building envelope, special structural needs and even aesthetics.
The easiest way to prove an assembly is properly rated for the application is to use a tested assembly however, it is more common in mid-rise construction that you will need to use all of these methods and it is helpful to know how others are doing this.
The three basic ways to establish a fire rated assembly is by 1. Tested the assembly to E119 standard. Most think of UL but there
are other sources of assemblies. AWC and APA both have information on tested assemblies
2. Deemed to comply tables and3. Calculated fire resistanceAn advantage to DCA 3 is that you can use 100% of the design load where a reduced loading is required in the deemed to comply tables and other approved assemblies.
Exposing StructureIBC 703.3 Alternate Methods for determining fire resistance
• Prescriptive designs per IBC 721.1
• Calculations in accordance with IBC 722
• Fire-resistance designs documented in sources
• Engineering analysis based on a comparison
• Alternate protection methods as allowed by 104.11
IBC 722 Calculated Fire Resistance
“…The calculated fire resistance of exposed wood members and wood decking shall be permitted in accordance with Chapter 16 of ANSI/AF&PA National Design Specification for Wood Construction (NDS).”
NDS Chapter 16 Fire Design of Wood Members
Limited to calculating fire resistance up to 2 hours.
Char rate varies based on endurance required, product type and lamination thickness. Equations and tables provided.
TR10 and NDS commentary are helpful in implementing permitted calculations.
Distinctions between Type III and Type V wood-framed mid-rise buildings go beyond the allowable heights and areas. In addition to the use of FRT, a big difference between Type III and V is the fire-rating requirement at the exterior bearing wall. Table 601 requires that both Type IIIA and IIIB structures have two hours of fire protection on the inside face of the exterior wall lines.
This jump in fire resistance both for the exterior wall and the firewall is not as straightforward as simply finding a UL assembly with an increased rating.
Key Differences in Fire Ratings for Construction Types (hrs)
IA IB IIIA IV
Primary Structural
Frame 3 2 1 HT
Exterior wall fire rating 3 2 2 2
Floor assembly fire
rating 2 2 1 HT
Fire wall rating 3 3 3 3
Fire Resistance Ratings
IBC Tables 601 & 706.4
6 Stories/85 ft 5 Stories 3 Stories/63 ft 5 Stories
5 Stories 6 Stories/ 85 ft 4 Stories 7 Stories/ 85 ft
Contact Information
Hans-Erik Blomgren
206-493-2248
Lisa Podesto
530-520-7966
Summary
• Reviewed the historical context for tall timber structures, and considered the construction and sustainability motivators driving modern examples.
• Learned how tall timber can achieve design goals outside of code requirements including high acoustical performance, unique aesthetics and ambitious sustainable objectives.
• Discovered how tall timber can achieve structural performance and approval in the US.
• Realized how tall timber can achieve fire performance and approval in the US.