TACK COAT: A thin coat of bitumen, road tar or emulsion laid on a road to improve the adhesion of a course above it.
TANDEM ROLLER: A road roller having rolls (drums) of about the same diameter behind each other on the same track.
TACK WELD: A temporary half-inch thick weld that holds steel parts together during fabrication.
TEMPERATURE STEEL: Reinforcement which is inserted in a slab or other concrete member to prevent cracks due to shrinkage or temperature stresses from becoming too large. It generally amounts to a minimum of about 0.1% of the cross-section in any direction. The requirement for a slab, which is two-dimensional, being therefore about 0.2% altogether.
TEMPERATURE STRESS: A stress due to temperature rise or drop. If the expansion due to temperature rise or the contraction due to temperature drop is restrained, the member concerned is stressed in compression during rising temperature or tension during falling temperature.
TENDON: A pre-stressing bar, cable, rope, strand or wire.
TERZAGHI-MEYERHOFF EQUATION: This equation is used to find the gross (ultimate) bearing capacity or gross pressure for a soil:
THRUST: A horizontal force, particularly the horizontal force exerted by retained earth.
TOPSOIL: The topmost layer of the soil which by its humus content supports vegetation. It is usually the top one foot of the soil.
TOLERANCE: Acceptable variation from a standard size.
TOUGHNESS: The resistance of a material to repeated bending and twisting.
TORQUE, TORSION OR TWIST: The twisting effect of a force on a shaft applied tangentially, like the twist on a haulage drum which winds rope on to its circumference.
TRAFFIC LANE: That portion of a travelled way for the movement of a single line of vehicles.
TRAVEL LANE: When used to distinguish between passing lane and travel lane, the travel lane is the right lane of a two lane roadway with both lanes going in the same direction. Usually both the passing lane and the travel lane are considered travel lanes with the passing lane considered to be the right travel lane.
TRAVELED WAY: The portion of the roadway for the movement of vehicles exclusive of shoulders and auxiliary lanes.
TRUSS: A frame, of steel, but also sometimes of timber, concrete, or light alloy, to carry a roof or bridge, built up wholly from members in tension and compression. It is generally a perfect frame or nearly so, and may be pin jointed.
TURFING: The covering of an earth surface with growing grass cut from another site. It can also be revetment to slopes which are usually covered by water, made by laying turves on the slope according to a technique like sliced block-work.
UNIFORM FLOW: Flow which has a constant depth, volume and shape along its course.
UPLIFT: (1) An upward force on earth due to water leaking into a dam or from any point where water is under high pressure. (2) Lifting of a structure caused by: frost heave, or on the windward side by wind force, or in a dry climate by swelling soil.
VARRIED FLOW: Flow that had a changing depth along the water course. The variation is with respect to location, not time.
VIBRATED CONCRETE: Concrete consolidated by vibration from an internal or external vibrator. It requires very much less water for effective placing than does concrete compacted by punning, therefore it is much stronger. The formwork, however, must also be stronger when the concrete is to be vibrated. Concrete in hollow-tile floors is not vibrated.
VIBRATOR: A tool which vibrates at a speed form 3,000 to 10,000 rpm and is inserted into wet concrete or applied to the formwork to compact the concrete.
WARPING: Deviation of pavement surface from original profile caused by temperature and moisture differentials.
WATER FOR DOMESTIC USE: Potable water used by the public (Home-use).
WORK: The product of a force and the distance through which it moves. It is to be distinguished from energy and from power which is a rate of doing work. Energy can, however, be expressed in the same units as work, and often is.
WORK ON ENGINEERING CONTRACTS: Work here shall mean the furnishing of all labor, materials, equipment and other incidentals necessary or convenient to the successful completion of the project and the carrying out of all the duties and the obligations imposed by the contract.
WEEPHOLE: A hole to allow water to escape from behind a retaining wall and thus to reduce the pressure behind it.
WORKABILITY: The ease with which a concrete can be mixed, placed and finished. Wet concretes are workable but weak. Workability can be measured by the slump test, the compacting factor test, and by the V.-B. Consist meter test.
XYLEM: The botanical name for wood.
YIELD OR BUCKLE: The permanent deformation which a metal piece undergoes when it is stressed beyond its elastic limit.
ZONING: Restrictions as to size or character of buildings permitted within specific areas, as established by urban authorities.