Glossary

axial load

A force acting along the long axis of a member or vertically in a wall.

base isolation

A means of limiting the seismic forces on a building by supporting it on devices that allow relative movement to occur between the building and its foundation.

base shear

The horizontal force at the base of a structure due to inertial forces acting during earthquake ground movement.

bending moment

Occurs in a structural element (such as a beam) when forces are applied at right angles to the element so that it bends. Bending moments produce tension on one side of the element and compression on the other side.

CERA

Canterbury Earthquake Recovery Authority.

cone penetrometer

Measures the properties of soil beneath the surface in a particular location.

confinement reinforcement

Used to make reinforced concrete beams and columns stronger and more ductile so they can perform better in an earthquake.

CPT

Cone penetrometer test.

diaphragm

A flat (usually horizontal) structural element or system that transmits horizontal forces (typically from wind or earthquakes) to and from shear walls or frames.

double tee

A precast/prestressed concrete unit commonly used in floors or roofs.

driven pile

A pile made of timber, steel or precast concrete that is typically hammered into the ground to form foundations.

ductility

A measure of how easily a solid material (such as a metal) deforms under stress without breaking.

eccentric braced frames

Frames with diagonal bracing that is not concentric.

geotechnical investigation

An investigation by a specialist engineer or geologist into the physical properties of the rocks and soils at a particular location.

ground improvement

Techniques to improve the strength and stability of soil so it better supports a building.

hollow-core slab

Precast, prestressed concrete slabs that have tubular voids running through the full length, making them much lighter than solid slabs of equal thickness.

hysteretic damper

A damper that absorbs energy by allowing the metal to yield, either by bending or in tension and compression, depending on the design of the damper.

IEP

Initial evaluation process, usually carried out by a local building control authority to determine whether a building is likely to be earthquake prone or an earthquake risk.

in-plane forces

Forces that act in the same plane as the face of the wall.

inclined pile

A pile that goes into the ground on an angle rather than vertically so as to better resist horizontal forces.

intensity

A measure of the effects of an earthquake on people and buildings at a particular location. The intensity at a particular site depends on the strength (magnitude) of a quake, how far the site is from the epicentre of the earthquake and the geology under the site. Intensity is measured with the 12-point Modified Mercalli Intensity (MMI) scale.

inter-storey drift

The difference in sideways movement between two adjacent storeys.

lateral loads

Horizontal or sideways loads on the building.

liquefaction

Earthquake forces cause the sand and silt particles to rearrange themselves into a more compact volume, and the water is squeezed out of the reduced space between the particles. The loose granular soil starts to lose strength and behave like a dense fluid – hence the term ‘liquefaction’.

load

A force applied to a structure.

low-damage design

Design that means that, after a building displaces sideways in an earthquake, it will return to its original position.

magnitude

A measure of the strength of an earthquake (the amount of energy it releases) at the point where it occurs.

maximum considered earthquake

An earthquake that has a 2% probability in 50 years or a 2,500 year return period.

moment-resisting frame

A structural frame typically consisting of reinforced concrete or steel beams and columns that are rigidly connected at their joints. Resistance against sideways forces of wind or earthquakes is by bending of the frame members.

normal force/normal load

A force acting at 90° to an object.

out-of-plane forces

Forces that act at right angles to the face of the wall.

plastic hinge/potential plastic hinge

The zone in a concrete beam or column or shear wall where reinforcement yields or stretches under earthquake loading.

PREcast Sesimic Structural System

A technique where unbonded, tensioned cables or bars are threaded through precast concrete walls, beams and columns, with jointed ductile connections. The cables and ductile joints let the building spring back to its original position after a large earthquake.

PRESSS

PREcast Seismic Structural System.

return period

The average number of years between earthquakes of a certain magnitude on a particular fault or at a particular location.

serviceability limit state

Buildings that can still be used for their intended purpose after an earthquake of the magnitude that can be expected once or twice during the life of the building.

shear forces

Forces acting in a direction parallel to the face of the material or to a planar cross-section of a body.

shear wall

A structural wall, commonly of reinforced concrete or timber, that often starts at the base of a building and runs for its full height.

standard penetration test

A test to provide an indication of the density of the soil.

STIC

Structural Timber Innovation Company – a company set up to develop the use of post-tensioned LVL (laminated veneer lumber) structures.

ultimate limit state

This is concerned with the safety of people in buildings. To stay within its ultimate limit state, a building must still be standing after being subjected to its peak design load.

unreinforced masonry

Concrete, stone or brick masonry that has no reinforcing steel.

URM

Unreinforced masonry.