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a book with a complete explanation about floor joists and frames. it explains basic terms to computation.
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Designing Floor Systems with Engineered Wood Joists
Course Sponsor
Designing Floor Systems
with Engineered Wood Joists
Universal Forest Products, Inc. 2801 East Beltline NE
Grand Rapids, MI 49525
616-365-6608
cfox@ufpi.com
Web
www.ufpi.com
Course Number
ufp06a
2007 Universal Forest Products. The material contained in this course was researched, assembled, and produced by Universal Forest
Products and remains their property. Questions or concerns about the content of this course should be directed to lkroh@ufpi.com.
An AIA Continuing Education Program
Credit for this course is 1 AIA HSW CE Hour
Ron Blank & Associates, Inc. 2009
Please note: you will need to complete the conclusion
quiz online at ronblank.com to receive credit
An American Institute of Architects (AIA)
Continuing Education program
Approved Promotional Statement:
Ron Blank & Associates, Inc. is a registered provider with The American
Institute of Architects Continuing Education System. Credit earned upon
completion of this program will be reported to CES Records for AIA members.
Certificates of Completion are available for all course participants upon
completion of the course conclusion quiz with +80%.
Please view the following slide for more information on Certificates of
Completion through RBA
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 or Ron Blank & Associates, Inc. of
any material of construction or any method or manner of handling, using,
distributing, or dealing in any material or product.
An American Institute of Architects (AIA)
Continuing Education program
Course Format: This is a structured, web-based, self study course with a final exam.
Course Credit: 1 AIA Health Safety & Welfare (HSW) CE Hour Completion Certificate: A confirmation is sent to you by email and you can
print one upon successful completion of a course or from your
RonBlank.com transcript. If you have any difficulties printing or receiving
your Certificate please send requests to certificate@ronblank.com
Design professionals, please remember to print or save your certificate of completion after successfully completing a course conclusion quiz. Email
confirmations will be sent to the email address you have provided in your
RonBlank.com account. Please note: you will need to complete the conclusion quiz
online at ronblank.com to receive credit
There are many factors to consider when designing a floor system
with engineered wood joists. Review the design strategies, code
requirements, different types of engineered floor components, and
their capabilities and limitations.
Course Description
Course Objectives
Upon completion of this course the design professional will be able to:
List the factors to consider when designing floor systems
Explain the appropriate design strategies for code requirements and client
satisfaction
List the types of engineered floor components, their capabilities, and limitations
Explain the Engineering, design, and support available from manufacturers
The advent of engineered wood framing
components has impacted floor system and
subsequent building design
Engineered products use wood fiber more efficiently and permit the use of
former waste fiber for new structural components with greater strength than solid sawn lumber.
New configurations with I shapes and triangles result in products with greater strength than solid sawn lumber.
Because of this new strength, design
professionals now have greater design
flexibility and opportunities for designing
larger open spaces.
This new strength also produces new
construction efficiencies through fewer
components and faster installation.
Impact of Engineered Wood
on Floor System Design
Designing floor systems
with engineered wood
components requires new
considerations by design
professionals.
In addition to safety considerations addressed
by the model building
codes, user comfort and system performance with
regard to deflection,
vibration and sound
transfer must now become
integral factors in
designing floor systems.
Designing floor systems with engineered wood
products requires attention to three sets of
considerations:
1.Requirements of the applicable model building code with regard to safety factors.
2.Practical considerations including product availability, ease and speed of installation, and design flexibility.
3. Comfort factors that may have impact on the physical and psychological well-being of those who will occupy or visit a
building.
Lets look at the various design considerations within each of these categories.
Design Considerations:
Building Code Requirements
Design Safety Factors:
Length of Span Loading Conditions Deflection Criteria Joist Spacing Fire Endurance Seismic Performance Local Regulations
Building Code Requirements
Safety Factor: Length of Joist Span
Length of span, while not specified by the building codes, is certified and
published by joist and truss manufacturers and is recognized by the model
building codes in product evaluation reports. Published spans may be used
by design professionals within the specified loading and spacing
parameters.
Building Code Requirements
Safety Factor: Length of Joist Span
Length of the joist span is determined by the designers space concepts and the locations of bearing points in a structure. Designers often relocate bearings to accommodate span capabilities. Once a desired span has been identified, it must be considered in context with loading conditions, deflection characteristics, joist spacing and bearing size. Consult manufacturers literature and software to confirm the appropriate joist span for given conditions.
Building Code Requirements
Safety Factor: Loading Conditions
Three types of loads may apply to any floor system:
Live Loads Dead Loads Special Loads (Line, Point, Area) Live Loads are temporary loads and are defined by the building codes according to the intended use of the structure. Dead Loads are permanent loads and are comprised of the actual weights of materials that make up the floor/ceiling system. Special Loads are permanent and are actual design loads occurring on confined areas of a floor system.
Building Code Requirements
Safety Factor: Loading Conditions
Live Loads:
Live Load conditions consider temporary loads uniformly
applied to the floor system (people, furniture and moveable
items) and are specified by the building codes according to the
designated function of the space, i.e.:
Residential Living Spaces: 40 PSF Office Use: 50 PSF Retail Use: 80 PSF Assembly Areas: 100 PSF
Building Code Requirements
Safety Factor: Loading Conditions
Dead Loads:
Dead Loads are permanent, non-moveable elements (floor framing and
decking, ceiling finish, mechanical systems, insulation, etc.) and loading is
determined by the sum of the weightsper square footof all these elements. Dead Loads are applied uniformly to the floor system.
Common design practice uses standard Dead Load factors of 10, 15 or 25
PSF depending on the makeup of the floor/ceiling envelope.
Building Code Requirements
Safety Factor: Loading Conditions
Special Loads:
Line, Point and Area Loads are permanent and represent concentrated
loads on specific limited areas of a floor system. They are not applied
uniformly. These special loads may result from roof framing, interior bearing
walls, large mechanical units, large fixtures, etc.
Building Code Requirements
Safety Factor: Deflection
Deflection is vertical movement of a floor system when subjected to loads.
The Building Code specifies Deflection Limits for floor systems:
L/360 Live Load Deflection and L/240 Total Load Deflection
(L is joist length in inches)
Example:
Joist Length of 20 (L= 240) 240 divided by 360 = .67 inches allowable deflection under full load
condition
Deflection limits are based on historical performance and are specified by
the codes for user comfort and to prevent cracking of ceiling and flooring
materials.
Building Code Requirements
Safety Factor: Deflection
Deflection performance of a floor system is determined by three factors:
Length of Joist Span Loading Conditions Stiffness of the Framing Member (joist) Of these three, Length of Joist Span has the greatest impact on deflection.
Building Code Requirements
Safety Factor: Deflection
Floor system deflection can be reduced in several ways:
By reducing Loading (by decreasing the on-center spacing of the joists) By reducing the Joist Span By increasing the Joist Depth By upgrading Joist size or materials:
Larger dimension flange or chord Higher lumber grade of components Use of engineered materials
Building Code Requirements
Safety Factor: Joist Spacing
The building code does not specify on-center joist spacing but does require
spacing that will produce specified deflection performance for the loading
conditions.
Joist spacing is most often determined by owner/builder preference or the
desire to value engineer the floor system.
Traditional joist spacing is 16 o.c.
Stronger engineered joists have made possible new on-center spacing
options of 19.2 and 24.
The building codes set only minimum requirements for floor system
performance.
Value engineering recognizes the ability of fewer, stronger joists to meet
code minimums.
Building Code Requirements
Safety Factor: Joist Spacing
Joist spacing must be considered along with loading conditions and length of
span when designing to achieve desired deflection performance.
Floor system performance may be enhanced by designing for higher
deflection limitations, especially for longer spans.
Since loading conditions and length of span cannot normally be changed,
Joist Spacing is the element most often changed to achieve desired
deflection performance.
Building Code Requirements
Safety Factor: Fire Resistance
Building classification and building codes determine if floor systems must be
designed to meet minimum fire resistance requirements.
Multi-Family and institutional residences most often require separation of
living units by fire resistant floor/ceiling assemblies.
Single-Family residences with integral garages often require separation.
Building Code Requirements
Safety Factor: Fire Resistance
Minimum standards for fire endurance are specified by building codes to
allow adequate time for building occupants to escape during a fire and for
firefighters to extinguish fires.
Floor/ceiling assemblies are designed to endure in a fire for a specified
duration of timeone, two, or more hours (depending on the code requirement).
Assemblies are tested for fire endurance by independent third-party testing
agencies using ASTM standard test designs and procedures.
Once certified, endurance assemblies are published by component product
manufacturers and by certification agencies.
Building Code Requirements
Safety Factor: Seismic Performance
Individual floor joists cannot be rated for a
specific seismic zone since they only act as
components of a lateral-force-resisting
system.
Joists act as drag struts or chords in lateral-force-resisting systems such as shear
walls.
Designers must be aware of the required
forces a drag strut must carry and refer to
manufacturer data for the products drag strut capabilities.
Drag Loads are normally specified by the
building designer on construction plans.
Building Code Requirements: Local Regulations
A few local jurisdictions prohibit the use of specific engineered wood framing products. Some local codes specify more stringent deflection limitations for floor systems than the model building codes permit. Some municipalities have fire protection regulations requiring the use of sprinkler systems and/or baffling in floor systems. Fire endurance requirements may also vary by jurisdiction. Design professionals must be aware of these local regulations when designing engineered wood floor systems.
Building Code Requirements
Because SAFETY is the primary purpose of model building code
enforcement, adherence to code requirements is the responsibility of all
the following:
Design Professionals
Project Developer
General Contractor
Framing Contractor
Mechanical Trades
Building Inspector
Design Considerations: Logistical Factors
Several elements of practicality must be considered when choosing the type
of framing product to be used in an engineered wood floor system, including:
Installation of Mechanical Systems
Construction Timetable
Product Access
Cost
Design Considerations: Logistical Factors
Installation of Mechanical Systems
Electrical, Plumbing, HVAC:
Is it necessary or desirable to contain mechanical
systems within the floor/ceiling envelope (due to building
height restrictions, basement headroom, etc.)?
Is it necessary or desirable to frame bulkheads for duct
runs (may also be a design element)?
Is the construction schedule impacted by mechanical
systems installation time?
Is there likelihood of error when joists are altered to allow
mechanical systems penetrations?
Do MEP requirements and fixture placement dictate joist
depth and spacing?
Design Considerations: Logistical Factors
Construction Timetable:
Will floor framing materials be shipped on a schedule to conform with job
site progress?
Is it reasonable to expect timely and efficient installation of floor system
components?
The pace of construction obviously
impacts project cost.
Design Considerations: Logistical Factors
Product Access:
Are there dependable local sources
of supply for engineered wood
products?
Do suppliers offer competent
technical support for the
engineered products they offer?
Is there confidence that supply
issues will not result in down time at the job site?
Design Considerations: Logistical Factors
Cost:
Installing the strongest, best performing
floor system for the lowest cost is
everyones natural objective.
The installed cost of a system that meets
both structural and performance
requirements is the standard of
measurement used to judge the success of
a floor system design.
Design Considerations: Comfort and Performance
Two floor system factors have significant physical and psychological impact on individuals who inhabit or use a building. Those factors are:
Sound Transmission &
Floor Vibration While these factors may, in fact, be measured quantitatively, reactions to
them by humans are purely subjective. For this reason, design professionals should be aware of human preferences for performance with regard to these factors.
Design Considerations: Comfort and Performance
Sound Transmission:
Sound transmission refers to how easily sound is transferred through an elevated floor system.
Some code bodies set requirements for sound performance by specifying minimum standards for Sound Transmission Class (STC)
and Impact Insulation Class (IIC).
Design Considerations: Comfort and Performance
Sound Transmission:
STC and IIC ratings are determined by the testing and certification of floor/ceiling assemblies by independent third-party agencies.
Codes and designers specify minimum STC and IIC ratings for floor systems to satisfy the majority of people who occupy or use a
structure.
It remains a fact that human reactions to sound transmission are totally subjective in nature.
Design Considerations: Comfort and Performance
Sound Transmission:
Manufacturers of engineered wood floor framing components and third-party agencies publish sound performance assemblies for reference by
designers.
To maintain sound performance requirements, construction details must be followed accurately so that assemblies are not compromised
by penetrations, etc.
Design Considerations: Comfort and Performance
Floor System Vibration:
Vibration is oscillatory movement of the floor system when subjected to a live load such as footsteps, a dropped item, or machine vibration.
Floor vibration performance is the least quantitative and most subjective characteristic of a floor system.
Vibration performance should be a priority.
consideration for floor system designers.
Design Considerations: Comfort and Performance
Floor System Vibration:
Studies have shown that excessive floor system vibration makes occupants uncomfortable and may even cause them to fear system
failure.
It is also known that auditory effects (rattling china closets, etc.) heighten human discomfort with vibration.
Vibration is not necessarily related to the structural integrity of a floor system and extra design measures may be required in anticipation of
satisfying end users.
Design Considerations: Comfort and Performance
Floor System Vibration:
It should be recognized that floor system vibration is a performance concern, not a safety issue.
U.S. building codes do not specify vibration performance requirements for floor systems.
It should also be recognized that vibration is not simply a side effect of deflection.
Design Considerations: Comfort and Performance
Floor System Vibration:
Three factors influence human response to floor system vibration:
The Frequency Content of the vibration
The Amplitude of the vibration
The effects of vibration Damping
Design Considerations: Comfort and Performance
Floor System Vibration:
Frequency Content is the cycle time of the vibration, measured in cycles per second or hertz, Hz.
Humans feel more comfort with higher frequency vibrations than lower Hz cycles.
Shorter lengths of span have higher frequencies than long lengths of span.
Design Considerations: Comfort and Performance
Floor System Vibration:
Amplitude is the magnitude of floor vibration.
Amplitude is directly related to the stiffness of the floor (deflection).
High amplitude vibrations are more annoying to people than low amplitude
vibrations.
Design Considerations: Comfort and Performance
Floor System Vibration:
Amplitude may be reduced by two methods:
Specifying deeper framing members (joists)
Using bridging between joists Continuous bridging perpendicular to the
bottom flange of the joist is the most effective.
Design Considerations: Comfort and Performance
Floor System Vibration:
Damping of vibration reduces amplitude and shortens the duration of
vibrations.
Damping is provided by existing loads and frictions within the floor system.
Damping is achieved with bridging and through the presence of interior
partition walls.
Design Strategies
To determine the proper design strategy for a project, the design
professional must consider building classification, safety factors, comfort
factors and cost.
These considerations will lead to
one of two basic design strategies:
Code Minimum Strategy
Client Satisfaction Strategy
Design Strategies
Code Minimum Strategy:
Most often, this strategy is identified as the
Value Engineering approach. In this design strategy:
On-center joist spacing is maximized and long spans are accommodated
Quantities of framing materials are minimized and installation time is reduced
The installed cost of the floor system is minimized
Design Strategies
Client Satisfaction Strategy:
The classification of a building normally dictates the application of this strategy.
Custom residences and other privately
commissioned projects naturally demand
a client satisfaction design strategy.
This strategy gives high priority to comfort and performance factors when designing
floor systems and usually specifies
structural performance in excess of that
required by the building codes.
In this strategy, cost is usually not of primary concern.
Engineered Wood
Floor Framing Components
Now lets consider the engineered wood floor framing components available in todays market.
They include:
Floor Joists
Beams and Girders
Rim / Band Board
Hangers / Connectors
Engineered Wood
Floor Framing Components
Floor Joists:
There are three types of engineered wood joists
available today:
Wood I-Joists
Steel-Plate-Connected Parallel Chord Floor Trusses
All-Wood Parallel Chord Floor Trusses
Engineered Wood
Floor Framing Components
Wood I-Joists:
Invented 1969 by Truss Joist Corporation
Extensive architect education effort
I cross section
Solid sawn flanges and plywood web
Switched to LVL flanges and OSB webs in 1990s
APA-The Engineered Wood Association published standards for I-Joists in 1990s
Engineered Wood
Floor Framing Components
Wood I-Joists:
Flanges resist bending, web resists shear
Lighter than dimension lumber
Efficient use of wood fiber
Consistent quality
Penetrations through web limited
Depths of 9-1/2, 11-7/8, 14, 16, 18
Multiple span applications with proper blocking
Engineered Wood
Floor Framing Components
Wood I-Joists: Flange dimensions of 1-1/2 to 3-1/2
Flanges of solid sawn SPF, LVL, LSL
Installation requires accessory reinforcement pieces: web fillers, web
stiffeners, squash blocks
Can accommodate some point, line and area loads with proper reinforcement
Structural rim board is required at ends of joists
Engineered repair details required
Engineered Wood
Floor Framing Components
Steel-Plate-Connected
Parallel Chord Floor Trusses:
Invented in 1952 by A. Carroll Sanford
Open web configuration
Made possible by the innovation of the steel truss plate
Steel plate values are measurable and can be sized to handle forces of
compression and tension at joints
Truss engineering software is used to design trusses for specific job
conditions
Engineered Wood
Floor Framing Components
Steel-Plate-Connected
Parallel Chord Floor Trusses:
Constructed of SYP, Doug Fir or SPF lumber
Flanges of 4x2 most common
Web dimensions must be same as flange dimension
May be designed to accommodate duct chases
Must be fabricated to exact jobsite dimensions
Structural rim board is not required at ends of trusses
Engineered Wood
Floor Framing Components
Steel-Plate-Connected
Parallel Chord Floor Trusses:
Can be designed to handle point, line, and area loads
Common depths are 12, 14, 16, 18, 20, 22, 24
May be damaged by excessive construction materials loads
Engineered repair details required
Engineered Wood
Floor Framing Components
Proprietary Steel Plated Floor Trusses: Open web configuration
Wood or steel webs
Stock lengths with trim-able I ends
Space Joist TE, Trim Joist, Gator Joist
Depths of 9-1/4, 11-1/4, 14, 16, 18
Flanges of 4x2 or 3x2
Structural rim board required
Engineered Wood
Floor Framing Components
All Wood Parallel Chord Trusses:
Invented in Canada in 1989
First trim-able open-web floor joist
Stock lengths in one-foot increments
Combination of I and truss engineering
Values from actual testing
Engineered Wood
Floor Framing Components
All Wood Parallel Chord Trusses:
Assembled with precision finger joinery and structural adhesive
No metal plates or fasteners
Spruce-Pine-Fir flanges and webs
Flanges of 4x2 and 3x2
Depths of 9-1/4, 11-7/8, 14 16
Technology allows efficient use of wood fiber
Engineered Wood
Floor Framing Components
All Wood Parallel Chord Trusses: Trusses are individually tested
Standard repair details on hand
Simple span installation
Bottom-chord-bearing
1-1/2 bearing required
Can accommodate point, line, and
area loads with proper reinforcement
Structural rim board not required
Engineered Wood
Floor Framing Components
Structural Rim Board:
Structural rim is designed to support vertical
loads transferring down through bearing walls.
This rim is available in several engineered wood
technologies, including:
LVL (laminated veneer lumber)
PSL (parallel strand lumber)
LSL (laminated strand lumber)
OSB (oriented strand board)
Glu-Lam (laminated solid sawn lumber)
Solid sawn lumber
Engineered Wood
Floor Framing Components
Beams and Girders:
Beams and girders are manufactured with the same technologies as
structural rim board, including:
LVL (laminated veneer lumber)
PSL (parallel strand lumber)
Glu-Lam (laminated solid sawn lumber)
Steel plated girder trusses
Engineered Wood
Floor Framing Components
Hangers and Connectors:
The designer must choose hangers that accommodate the
loads and reactions at the ends
of joists and beams.
Major manufacturers offer products to fit all engineered
wood joist and beam sizes.
Manufacturers provide Design Guides to help designers
choose correct products.
Design Assistance
Manufacturer Literature:
Span charts and load tables
Installation details
Fire and sound assemblies
Product specifications
Manufacturer Websites:
Repeat of printed information
Interactive for product sourcing
Downloadable details and specs
Design Assistance
Engineering/Design Software: Usually offered free of charge by
manufacturer
Training is usually provided
Design Done by Supplier: Design floor system to architects
specifications
Final approval by architect and/or engineer
Sealed shop drawings should be available from the manufacturer
Course Summary
The design professional will now be able to:
List the factors to consider when designing floor systems
Explain the appropriate design strategies for code requirements and client satisfaction
List the types of engineered floor components along with their capabilities and limitations
Explain the Engineering, design, and support available from manufacturers
Designing Floor Systems with Engineered Wood Joists
Course Sponsor
Designing Floor Systems
with Engineered Wood Joists
Universal Forest Products, Inc. 2801 East Beltline NE
Grand Rapids, MI 49525
616-365-6608
cfox@ufpi.com
Web
www.ufpi.com
Course Number
ufp06a
2007 Universal Forest Products. The material contained in this course was researched, assembled, and produced by Universal Forest
Products and remains their property. Questions or concerns about the content of this course should be directed to lkroh@ufpi.com.
An AIA Continuing Education Program
Credit for this course is 1 AIA HSW CE Hour
Ron Blank & Associates, Inc. 2009
Please note: you will need to complete the conclusion
quiz online at ronblank.com to receive credit
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