Residential Earthquake Retrofits in BC by Shear Seismic Retrofits

Glossary of Seismic Retrofit Terms

Adhesive Anchor

An anchor that is installed using a chemical adhesive. The adhesive may create a mechanical or chemical bond between the base material (concrete) and the anchor. Adhesives include epoxies, acrylates, viynl esters, polyesters, and hybrid mortars.

Aerated Concete

Aerated (or Lightweight insulating) concrete has a unit weight of approximately 115 pounds per cubic foot.

Anchor bolt

Also called “J-bolt” or “L-bolt” depending on its shape; used to connect sill plates to footings.
The term ‘bolt’ technically means a headed fastener so ‘anchor bolt’ is not entirely accurate to describe typical sill anchors.

Anchor rod

Hardware that connects a tie-down to the footing. ‘Anchor rod’ is a more technically accurate term to describe a threaded fastener thsat connects a building’s seperstructure to the footing.

Anchor Side Plate

A metal plate or plates used to connect the sill plate or floor framing to the side of a concrete stem wall when conditions prevent anchor or bolt installations vertically through the sill plate.

APA

Formerly The American Plywood Association; changed its name to, “APA–The Engineered Wood Association.”

Base Material

The element or substrate to be anchored to. Different types of base materials include concrete, hollow and grouted masonry block, clay masonry and brick.

Base Shear

The reaction at the base of a wall or structure due to an applied lateral load, a “sliding force.”

Blocked Diaphragm

A diaphragm in which all panel edges occur over and are nailed to common framing; the additional nailing provides a greater number of fasteners available to transfer shear from one panel to another, thus increasing the overall shear capacity and rigidity or stiffness of the diaphragm.

Unblocked Diaphragm is one in which only the 4-foot-wide panel ends occure over, and are nailed to, common framing; this is the most common type of diaphragm used in standard residential construction.

Boundary

An edge of a diaphragm; typically along eave blocking and the trusses or rafters in line with the gable-end walls for a roof diaphragm (not the fascia or barge rafters), the end and rim (band) joists for a floor diaphragm and the end-posts and top and bottom members of a shear wall.

Box-type Structure

When diaphragms and shear walls are used in the lateral design of a building, the structural system is called a “box system.”

Cast in Place

Installation of anchor occurs before the concrete has been poured.

Chemical Anchor

A fastener placed in hardened concrete that derives its holding strength from a chemical adhesive compound placed between the wall of the hole and the embedded portion of the anchor. Chemical adhesive compounds are organic compounds, composed of resin and hardener, that form adhesives when blended together. Examples of chemical adhesive compounds include epoxies, polyurethanes, polyesters, methyl methacrylates and vinylesters.

Composite Panel

A wood structural panel product composed of a combination of wood veneer and wood-based material and bonded with waterproof adhesive.

Compressive Strength

The Maximum Stress a material can sustain under crush loading. When the limit of compressive strength is reached, materials are crushed.

Concrete Masonry Unit (CMU)

A hollow or solid masonry unit made from cementitious materials, water and aggregates.

Cracked Concrete

Concrete that may crack through the line of the anchor during its service life.  Common factors that contribute to cracking include: concrete in tension (it’s natural weakness; tension is opposite of compression), seismic forces, external short term loads (eg. high winds), temperature variations)

Chord

The top or bottom member of a truss; also used to describe the member along a diaphragm boundary (diaphragm chord).

Collector

A structural member that connects a diaphragm to a shear wall in order to gather lateral forces spread throughout the diaphragm and deliver them to the shear wall.

Cripple Wall

A short wood-framed wall built on top of the foundation to support framing for the first-floor level above.

Diaphragm

A large area of sheathing such as a floor, roof or shear wall (diaphragms may be vertical as well as horizontal); in order to function as a diaphragm, all edges of the sheathed area must have boundary members, and the sheathing panels must connect to these members and to intermediate framing members to transfer forces across the panel joints.

Double Plate

Two horizontal framing members at the top of a wall, typically spliced or lapped to give continuity or tie wall sections together.

Drag strut

The load path for a box-type structure goes from the diaphragm into the shear walls running parallel to the direction of the load. Another way to say this is that the diaphragm loads the shear walls that support it. Because the diaphragm acts like a long, deep beam, it loads each of the supporting shear walls evenly along the length of the walls.

The traditional model used to analyze shear walls only recognizes wall segments that run full height as shear wall segment. This means that at locations with windows and doors, a structural element is needed to distribute the uniform diaphragm shear over the top of the opening into the full height segments adjacent to it. This element is called a drag strut.

Drag tie

Essentially the same as a drag strut or collector, with the added possibility that it may refer to a member that only transmits force from one part of the structure to another part some distance away, without collecting any additional force along the way.

Edge

When referring to a shear panel, a panel has four edges – two of these edges are “ends” and two are “sides”.

Edge Distance (Anchors)

Critical Edge Distance is the least edge distance at which the allowable load capacity or an anchor is applicable without reductions.

Minimum Edge Distance is the least edge distance at which the anchors are tested for recognition.

Embedment Depth

The depth of an anchor into the concrete prior to setting of the anchor.

Expansion Anchors

A mechanical fastener placed in hardened concrete designed to expand in a self-drilled or pre-drilled hle of a specified size and engage the sides of the hole in one or more locations to develop shear and/or tension resistance to applied loads without grout, adhesive or drypack.

Header

A horizontal member that spans across an opening in a wall (typically over a door or window).

Hold-down

See “Tie-down” – device used to keep the end of a shear wall from lifting up.

IBC

International Building Code – published by the International Council Code, Inc. (ICC), and available for adoption by government jurisdictions internationally.

ICBO

International Conference of Building Officials – publisher of the Universal Building Code. The ICBO is one of the three model code organizations that became the International Code Council (ICC).

ICC

International Code Council – publisher of the International Codes; including the International Building Code and the International Residential Code.

Installation Torque

The minimum moment applied to a torque-set anchor that creates the degree of anchorage required for full load values.

Load Path

The path taken by a force acting on a building. Loads are transferred by the elements in the building and by the connections between those elements into the foundation.

Oriented Strand Board (OSB)

A mat-formed structural panel product composed of thin rectangular wood strands or wafers arranged in oriented layers and bonded with waterproof adhesive.

Overturning

What happens when a lateral force acts on a wall or structure and the wall is restrained from sliding; a “tip-over” or overturning force results.

Perforated Shear Wall

Contains door and window openings and is treated as a single shear wall with a slightly lower capacity than that of a similar full-height shear wall segment.

Perimeter Foundation

A foundation system that is located under the exterior walls of a building.

Plan Detail

An individual drawing of a specific portion of construction containing dimensions, notes, and other information necessary to guide the work to be done.

Plywood

A structural panel product composed of sheets of wood veneer bonded together and with the grain of adjacent layers oriented at right angles to one another.

Snug Tight

The condition when the full surgace of the plate washer is in contact with the wood member and begins to slightly indent the wood surface.

Tensile Strength

The stress at which a material breaks or permanently deforms. A tensile strength test determines the load-carrying ability and the amount of deformation before fracture.

Tension Load

When the force is applied parallel to the anchor, it is a tension load.

Tensile Loading

In the context of anchor installation, whacking it on the head with a hammer.

Torque

The measure of the force applied to produce rotational motion usually measured in foot-pounds. Torque is determined by multiplying the applied force by the distance from the pivot point to the point where the force is applied.

Torque-Set Anchor

An expansion anchor whose wedge or sleeve engages the concrete base material in the drilled hole by the application of torque and where the amount of torque applied controls the degree of anchorage.

Torque-Controlled Adhesive-Bonded Anchors

An adhesive anchor employing an anchor element designed to generate expansion forces in response to tension loading.

Torque-Controlled Expansion Anchor

A post-installed expansion anchor that derives its holding strength from the expansion of one or more sleeves or other elements against the sides of the drilled hole through the application of torque, which pulls the cone(s) into the expansion sleeve(s). After setting, tensile loading can cause additional expansion (follow-up expansion).

Waferboard

A mat-formed wood structural panel product composed of thin rectangular wood wafers arranged in random layers and bonded with waterproof adhesive.

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