U-bolt - a bar bent in the shape of the letter "U" and fitted with threads and nuts at its ends 

ultimate strength - the highest stress which a material can withstand before breaking 

ultrasonic testing - nondestructive testing of a materials integrity using sound waves 

underpass - the lowermost feature of a grade separated crossing; see OVERPASS 

uniform load - a constant load across a member 

unit stress - the stress per unit of surface or cross-sectional area 

uplift - a negative reaction or a force tending to lift a beam, truss, pile, or any other bridge element upwards 

upper chord - the top longitudinal member of a truss 

V

 vertical curve - a sag or crest in the profile of a roadway 

vertical lift bridge -  a bridge in which the span moves up and down while remaining parallel to the roadway 

viaduct - a series of spans carried on piers at short intervals

vibration - the act of vibrating concrete to compact it 

Vierendeel truss - a Pratt truss without diagonal members and with rigid joints between top and bottom chords and the verticals 

voided slab - a precast concrete deck unit containing cylindrical voids to reduce dead load 

voids - an empty or unfilled space in concrete 

Voussoir - one of the truncated wedge shaped stones composing a ring course in a stone arch; also known as ring stone 

voussoir arch - an arrangement of wedge shaped blocks set to form an arched bridge 

W 

Warren truss - a triangular truss consisting of sloping members between the top and bottom chords and no verticals; members form the letter W 

washer - a small metal ring used beneath the nut or the head of a bolt to distribute the pressure 

water/cement ratio - the weight of water divided by the weight of cement in a concrete; ratio controls the strength of the concrete

waterway - the available width for the passage of water beneath a bridge 

wearing surface - the topmost layer of material applied upon a roadway to receive the traffic loads and to resist the resulting disintegrating action; also known as wearing course 

web - the portion of a beam located between and connected to the flanges; the stem of a dumbbell type pier 

web members - the intermediate members of a truss, not including the end posts, usually vertical or inclined 

web plate - the plate forming the web element of a plate girder, built-up beam or column 

web stiffener - a small member welded to a beam web to prevent buckling of the web 

weephole - a hole in a concrete retaining wall to provide drainage of the water in the retained soil 

weld -a joint between pieces of metal at faces which have been made plastic by heat or pressure 

weldability - a property of electrode and parent metal combined, estimated by the ability to make good welds by as many processes as possible 

welded bridge structure - a structure whose metal elements are connected by welds 

welded joint - a joint in which the assembled elements and members are united through fusion of metal 

welding - the process of making a welded joint 

weld layer - a single thickness of weld metal composed of beads (runs) laid in contact to form a pad weld or a portion of a weld made up of superimposed beads 

weld metal - the fused filler metal which is added to the fused structure metal to produce a welded joint or a weld layer 

weld penetration - the depth beneath the original surface, to which the structure metal has been fused in the making of a fusion weld; see PENETRATION 

weld sequence - the order of succession required for making the welds of a built-up piece or the joints of a structure, to avoid producing residual stresses 

weld toe -  particularly in a filet weld, the thin end of the taper furthest from the center of the weld  cross section 

wheel guard - a raised curb along the outside edge of traffic lanes to safeguard constructions outside the roadway limit from collision with vehicles 

wheel load - the load carried by and transmitted to the supporting structure by one wheel of a traffic vehicle, a movable bridge, or other motive equipment or device; see AXLE LOAD