designing with shear walls for low to midrise construction

Course Sponsor

California Expanded Metal Company

263 North Covina Lane City of Industry, CA 91744

Phone 425-591-4174

E-mail [email protected]

Web www.cemcosteel.com

www.sureboard.com

Course Number

cem05c

Credit for this course is 1 AIA HSW CE Hour & 1 PDH

© Ron Blank & Associates, Inc. 2014

Designing with Shear Walls for Low

to Midrise Construction

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.

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

[email protected]

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.

An American Institute of Architects (AIA)

Continuing Education Program

Approved Promotional Statement

Ron Blank & Associates, Inc. has met the standards and requirements of the Registered

Continuing Education Program. Credit earned on completion of this program will be reported

to RCEP. Certificates of completion will be issued to all participants. Complaints regarding

registered providers may be addressed to RCEP at 1015 15th Street, NW, 8th Fl.,

Washington, DC, 20005. Web site: RCEP.net.

Registered Continuing Education Program

Understand how to design with shear walls for low to midrise

construction. The components, location, test standards,

advantages and disadvantages, as well as what should be

considered when specifying shear elements are illustrated in this

course.

Course Description

Upon completion of this course the Design Professional will be able to:

• Explain what shear is

• Describe what a shear wall is

• Explain the main components of a shear wall

• Show where shear walls should be located

• List what types of forces shear walls resist

• Explain where shear walls direct lateral forces

• Describe what the test standards are for

• Explain the methods and systems providing shear values

• Express the advantages and disadvantages of each type of shear

method

• Explain what Architect, Engineer, and Specification professionals

consider when specifying shear elements

Course Objectives

What is Shear and Shear Walls

Shear is an action or stress resulting from applied forces that

causes or tends to cause two contiguous parts of a body to

slide relatively to each other in a direction parallel to their

plane of contact.

What are the Functions of a Shear Wall?

Shear Walls

• Provide lateral Strength to resist horizontal earthquake or

wind forces placed upon the structure

• Provide lateral Stiffness preventing excessive movement in

the roof or floors above

• Resist two types of forces:

– Shear forces

– Uplift forces

• Transfer horizontal forces to the next element in the load

path below them

– Other shear walls

– Floors

– Foundation walls

– Slabs

– Footings

View of Lateral Input/Activity

This Building Needed MORE Shear Strength!

Seismic event in California prior to the building code updates

that now exist.

Nationally Published Zones

Components Providing Horizontal and Vertical

Transfer of Shear Forces

• Uplift devices (hold-downs/straps/bolts)

• Framed shear walls

• Steel reinforced concrete columns, walls

• Prefabricated shear assemblies

• Brace Frames

• Moment Frames

Three Main Components Providing

the Strength in a Framed Shear Wall

• Framing Members – Studs – Beams – Posts

• Sheathing/Bracing Materials – Sheet materials

• Plywood/OSB • Steel sheet • Composite shear panels • Drywall/cement boards

– Bracing • Interior brace frame (tube, stud, or plate) • Cross bracing/strapping

• Fastener (size, pattern, frequency, and method) – Nails – Screws – Welds

Composite Sheet Steel Shear Panels on Cold

Formed Steel Framing

Composite Sheet Steel Shear Panels in

Cold Formed Steel Studs

OSB Shear Panels

on Wood Framing

Composite Sheet Steel Shear Panels

on Wood Framing

Main Components of Poured Concrete

• Steel Reinforced Concrete – (simple or “caged” metal

rebar)

• Post Tension

• Concrete

– Thickness

– Compressive Strength

– Tensile strength

– Cure time

Steel Reinforced

Concrete Shear Walls

Where Are Shear Walls

Typically Located

• At Floor level of all structures

• Symmetrically on exterior and/or interior walls

• Placed in relation to strength and stiffness required to

accommodate load paths based on span-width ratios and

vertical load

Code Approved Test Standards

• Shear Walls and Lateral Control Devices

• Reverse Cyclic Testing Method

• SPD-Sequential Phased Displacement

• CUREE-Consortium of Universities for Research in Earthquake Engineering

• Requirements for Testing/Reporting/Performance

• ICC Evaluation Service

• IAPMO Evaluation Service

• Additional Local City Requirements

• Los Angeles-LARR/LA Research Report

• New York-MEA/Mechanical Engineering Approval

• Dade County Florida/Miami Dade Approval

Test Equipment For Cyclic Test

Materials and Methods - Testing Equipment

Cyclic Test Rack

Another Rack View/Two Story

Cyclic Positive/Negative Loop

Typical Methods For Accommodating Shear

• Plywood / OSB sheathing

• Flat strap “X brace or cross bracing”

• Prefabricated Shear wall Assemblies

• Steel Sheet Independently

• Corrugated Sheet Metal

• Concrete Shear Wall

• Steel Braced Frame/Moment Frame

• Composite Steel Sheet with Wallboard or Substrate

sheathing attached

Plywood/OSB Sheathing

• Standard thickness approved 7/16” to 15/32” thick Plywood/OSB

• Full height/or multiple pieces with required blocking, attached with approved fasteners at required spacing per engineer of record and approved plans and specifications

• Advantages

– Material readily available

– Fasteners readily available

– Easy to handle, cut, install

– Minimal STC increase – (entire wall covered)

Plywood/OSB Sheathing

Disadvantages

• Combustible (additional fuel and path for fire)

• Susceptible to mold, rot, termites, etc…

• Nails “overdriven” reducing the effective shear values

• Unnecessary excess material and labor required to “furr out” wall to match sheared portions for installation of finish drywall or plaster

• Categories of building not approved using these materials:

– Type II non-combustible

– Type III modified non-combustible

– Assisted living require more employees in case of fire/Added costs of employees to qualify for exemption to use wood based products

Cold Formed Steel Framing

OSB for Shear Panel (Rare)

OSB Shear Panels

on Wood Framing

Flat Strap “X or Cross Bracing”

• 6” typical steel flat stock

• Gusset plates (locate at corners)

• Advantages


– Relatively low cost materials

– Small amount of materials used

Flat Strap “X or Cross Bracing”

Disadvantages

– Labor to first install gusset plates on all corners

– Labor to install straps (corner to corner)

– Build up of gusset plate, fasteners heads, and flat strap on top of one another

– Low shear value

– Ability to retain tension

• Difficult to install straps and retain tension

• Once wall “loaded” straps tend to buckle in unsupported spans

– Additional furring required to “hide” build up

– No penetrations, cutouts (doors or windows), or obstructions can go through straps

Picture of X-Bracing

• Prefabricated frames or formed steel

• Built to height, width, and strength requirements per E.O.R.

• Can be multiple pieces welded or fastened together

• May be single formed piece of material

• Advantages

– Strength

– Relatively quick install

– Less field labor to install

– Reduced number of fasteners required

Prefabricated Shear Wall Assembly

Prefabricated Shear Wall Assembly

Disadvantages

• Rigid causing issues with uneven foundation/floors

• Obstruction for MEP’s inside wall

• Obstruction for penetrations (doors, windows, etc…)

• Expense of prefabricated materials

• Shipping costs

• Field modifications are labor intense and costly

Pre-Fabricated Shear Walls

Prefabricated Shear Walls

Steel Sheet Shear Panel

• 22 Gauge steel sheet applied to wall framing

• Advantages


– Non-combustible

– Thin requiring no additional furring of wall

– Provides backing

• Disadvantages

– Difficulty installing and keeping tension; Without proper

tension steel will buckle when loaded

– Build up of fasteners required for installing just the sheet of

steel

– Additional labor to install first steel then drywall sheets

– Strength reliant upon tension during install.

– Handling of materials

Sheet Steel Used as Shear Panel

with Difficulty Keeping Tight

Sheet Steel Used as Shear Panel with

Difficulty Keeping Tight

Corrugated Metal for Shear Panel

Corrugated metal panel installed with ribs perpendicular to studs

Advantages

• Stronger than Plywood/OSB

• Non-Combustible

• Material readily available

Disadvantages

• Build up on wall requiring additional furring for the entire length

of wall for wallboard

• Bends of corrugation make it less stable than flat sheet

• Labor to first install sheet of steel then additional labor to install

wallboard

• Penetration cut outs difficult due to depth of corrugations

Corrugated Test Panel at UC Berkeley

2007 Before Test

Results of Corrugated

Steel Shear Cyclic Test

Concrete Shear Walls/Shafts

Poured reinforced concrete shear walls

• Advantages

– Continuous rebar/cables throughout floors

– Weight eliminates significant “hold-down” requirements

– Building shear can be carried throughout, without framed shear walls

– Non-combustible

– High STC value

• Disadvantages

– Very expensive labor and materials to construct

– Job schedule slow down

– Penetrations very difficult/expensive

– Obstructions in design layout (less flexibility in design and changes)

– Increased weight of the overall building.

– Shear system must stand independent from any framing attached. (Entirely different performance characteristics)

Concrete Steel Reinforced

Bearing/ Shear Wall

Steel Braced Frame/Moment Frame

• Prefabricated steel I-beam and tube steel braced frames

• Built to height, width and strength requirements per engineer of record and approved drawings

• Can be multiple pieces welded or bolted together

• Advantages

─ Strong

─ Relatively quick to install

─ Less field labor to install

─ Reduced number of fasteners required

Disadvantages

• Very rigid with inability to conform with irregular concrete base

• Obstruction for MEP’s

• Obstruction in cavity if braced frame design

• Obstruction for windows, doors, etc.

• Very expensive system, with very little adjustment possible

• Significant point load in concrete deck/more concrete and steel required

• Cost to deliver is higher due to huge amounts of air-per-truck

• Costs to erect very high and very dangerous for workforce (Cranes/trucks/etc.)

Steel Braced Frame/Moment Frame

Steel Braced Frame/Moment Frame (1st level)

Steel Braced Frame/Moment Frame – Moving

Upward (Significantly Higher Labor Costs)

Composite Steel Sheet With Bonded

Gypsum/Substrate Wall Sheathing

• 22 Gauge Steel sheet laminated to any variety of gypsum or

non-structural substrate board product for Shear

• Requirements of Use

– Material made to each job requirements on height / 3

week lead time if special length requested

– Additional labor required to cut and install penetration

holes (New metal cutting saws and drill bits available)

– Additional labor to install and additional fasteners when

higher loads are required. (New collated screw-guns

available)



Advantages

• Increased strength over plywood, sheet steel, and x-bracing

• Use any type, thickness, and variety of gypsum/cement based

wallboard

– Accommodate different wall designs and types of exposure

– May be used interior application

– May be used exterior application

– May be used as Structural substrate

• One step application installing shear element, fire rated protection,

and finish drywall

• Reduction of labor to install first shear element and then finished

product



Advantages (cont’d)

• Improved fire resistance

• Improved STC ratings (when entire wall covered)

• Flexibility in design

• Provides backing (wall fixtures or second layer of drywall), abuse,

impact, and blast resistance

• Engineered system/ICC and all national approvals

• Non-combustible

• Insect proof

• Mold resistant

• .027 steel thickness/requires no additional furring required on rest of

wall

• No surface irregularities

• Hurricane impact resistant

Composite Steel/Gypsum Being Prefabricated

in Panel Shop for Delivery

Composite Steel/Gypsum After Installation

No Slack in Steel Sheet 30% Higher Strength

Composite Steel/Gypsum Stacked To Maximum

Limits of Code 65’ High Performance

• 22 Gauge Steel sheet laminated to 1/8” thick substrate

• Requirements of Use

– Material is made to each job’s requirements on height – 3 week delivery if special length requested

– Additional labor required to cut and install penetration holes (New metal cutting saws and drill bits available)

– Additional labor to install and additional fasteners when higher loads are required. (New collated screw-guns available)

Composite Steel Sheet and

Non-Structural Substrate

Composite Steel Sheet and

Non-Structural Substrate

Advantages • Increased strength over

plywood/OSB

• Can be used interior application

• Can be used exterior application

• Can be nailed on without concern of “over-driving” nails; providing

consistent values

• Improved fire resistance

• Improved STC ratings (when entire wall is covered)

• Flexibility in design

• Engineered system

• Insect proof

• Steel sheet is mold resistant

• Limited buildup with no additional furring required on rest of wall

• Eliminate excess plywood

• Reduction in material costs

• Requires only single 2 x bottom plate on all wood framed shear walls

• No surface irregularities

Composite Steel/Medium Density Fiber Board

Installed on Wood Framing With Nails


Installed on Wood Framing Tight and Strong


Installed on Cold Formed Steel Water Resistant

Design Considerations

Provide the basic information needed to assure that wood and

cold-formed steel Structures include the following information:

• Products are properly identified

• Buildings are specified and designed in accordance with

current building codes and industry recommendations

• Buildings are constructed per plans and industry standards

Composite Steel/Gypsum or

Medium Density Fiber Boards

Some additional applications are:

• Backing for wall mounted fixtures

• Superior Fire resistance for 1 and 2 Hour

• Shaft wall for mechanical ducts

• Projectile resistance (Hurricane Zones)

• Blast and Ballistic resistant walls

• Future floor and roof diaphragms

These Are The Results When

We Are Surprised By Nature

Without The Necessary Lateral Control,

Shear Will End Like This!!

Composite Steel/Gypsum Helped

This Design Hold Together

The Design Professional will now be able to:

• Explain what shear is

• Describe what a shear wall is

• Explain the main components of a shear wall

• Show where shear walls should be located

• List what types of forces shear walls resist

• Explain where shear walls direct lateral forces

• Describe what the test standards are for

• Explain the methods and systems providing shear values

• Express the advantages and disadvantages of each type of

shear method

• Explain what Architect, Engineer, and Specification

professionals consider when specifying shear elements

Course Summary

Course Sponsor

California Expanded Metal Company

263 North Covina Lane City of Industry, CA 91744

Phone 425-591-4174

E-mail [email protected]

Web www.cemcosteel.com

www.sureboard.com

Course Number

cem05c

Credit for this course is 1 AIA HSW CE Hour & 1 PDH

© Ron Blank & Associates, Inc. 2014

Designing with Shear Walls for Low

to Midrise Construction

designing with shear walls for low to midrise construction

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