TGD A 2012 – 1.0.4 – DEFINITIONS

1.0.4 The following definitions apply to Section 1: Actions – Set of forces (loads) applied to the structure (direct action), or a set of imposed deformations or accelerations (indirect actions) caused for example by temperature changes or uneven settlement. Actions are classified by their variation in time and include the following (For full definitions of all terminology relating to actions and other action types refer to I.S. EN 1990): • Permanent action (G) – Action that is likely to act throughout a given reference period and for which the variation in magnitude with time is negligible, or for which the variation is always in the same direction (monotonic) until the action attains a certain limit value e.g. self weight of structures, fixed equipment etc; and indirect actions caused by e.g. shrinkage and uneven settlements etc; • Variable action (Q) – Action for which the variation in magnitude with time is neither negligible nor monotonic e.g. imposed loads on building floors, wind actions or snow loads; • Accidental action (A) – Action, usually of short duration but of significant magnitude, which is unlikely to occur on a given structure during the design working life. An accidental action e.g. due to fire, local failure, explosions or impact from vehicles, etc can be expected in many cases to cause severe consequences unless appropriate measures are taken. Buttressing wall – A wall designed and constructed to afford lateral support to another wall perpendicular to it, support being provided from the base to the top of the wall. Cavity width – The horizontal distance between the two leaves of a cavity wall. Compartment wall – A wall constructed as a compartment wall to meet the requirements of Part B (Fire Safety) of the Second Schedule to the Building Regulations. Execution – This covers all activities carried out for the physical completion of the work. The term covers work on site; it may also signify the fabrication of components off site and their subsequent erection on site. Imposed load – Imposed loads on buildings are those arising from occupancy e.g. normal use by persons, furniture and moveable objects (e.g. moveable partitions, storage), vehicles, and anticipated rare events, such as concentrations of persons or of furniture, or the moving or stacking of objects which may occur during reorganisation or redecoration. Pier – A member which forms an integral part of a wall, in the form of a thickened section, so as to afford lateral support to the wall to which it is bonded or securely tied. Self weight – (included in permanent actions) includes the structure and non-structural elements including fixed services as well as the weight of earth and ballast. Non-structural elements include roofing, surfacing and coverings, partitions, suspended ceilings, wall cladding, thermal insulation, fixed services e.g. electrical, plumbing, heating, ventilating, air conditioning etc. Separating wall – A wall or part of a wall which is common to adjoining buildings and constructed to meet the requirements of Part B (Fire Safety) of the Second Schedule to the Building Regulations. Spacing – The distance between the longitudinal centres of any two adjacent members of the same type, measured in the plane of floor, ceiling, roof, or other part of the structure of which members form a part. Span – The distance measured along the centre line of a member between the centres of any two adjacent bearings or supports. Supported wall – A wall to which lateral support is afforded by a combination of buttressing walls, piers or chimneys acting in conjunction with floor(s) or roof.

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