pack - a steel plate inserted between two others to fill a gap and fit them tightly together; also known as packing

pack rust - rust forming in a restricted place that tends to pack itself into a tight fit as the oxide increases the thickness of the parts

paddleboard - striped, paddle-shaped signs or boards placed on the roadside in front of a narrow bridge as a warning of reduced roadway width

panel - the portion of a truss span between adjacent points of intersection of web and chord members

panel point - the point of intersection of primary web and chord members of a truss

parabolic arch - an arch in which the intrados surface is a segment of a symmetrical parabolic surface (suited to concrete arches)

parabolic truss - a polygonal truss having its top chord and end post vertices coincident with the arc of a parabola, its bottom chord straight and its web system either triangular or quadrangular; also known as a parabolic arched truss

parapet - a low wall along the outmost edge of the roadway of a bridge to protect vehicles and pedestrians

pedestal - concrete or built-up metal member constructed on top of a bridge seat for the purpose of providing a specific bearing seat elevation

pedestal pier - one or more piers built in block-like form that may be connected by an integrally built web between them; when composed of a single, wide block-like form, it is called a wall or solid pier

pedestrian bridge - see FOOT BRIDGE

penetration - when applied to creosoted lumber, the depth to which the surface wood is permeated by the creosote oil; when applied to pile driving; the depth a pile tip is driven into the ground 

pier - a substructure unit that supports the spans of a multi-span superstructure at an intermediate location between its abutments 

pier cap - the topmost portion of a pier which distributes uniformly over the pier the concentrated loads from the bridge 

pile - a shaft-like linear member which carries loads through weak layers of soil to those which are  capable of supporting such loads 

pile bent - a row of driven or placed piles with a pile cap to hold them in their correct positions; see BENT 

pile bridge - a bridge carried on piles or pile bents 

pile cap - the uppermost portion of a pile which acts to secure the piles in position and provides a bridge seat to receive and distribute superstructure loads

pile foundation - a foundation reinforced by driving piles in sufficient number and to a depth adequate to develop the bearing resistance required to support the substructure load

pile pier - see PILE BENT 

piling - general term applied to groupings of piles in a construction. see PILE, SHEET PILES 

pin - a cylindrical bar used to connect 

pin-connected truss  -  a general term applied to a truss of any type having its chord and web members connected at the panel points by pins 

pin joint - a joint in a truss or other frame in which the members are assembled upon a cylindrical pin 

pin packing - an arrangement of truss members on a pin at a pinned joint 

pin plate - a plate rigidly attached upon the end of a member to develop the desired bearing upon a pin or pin-like bearing, and secure additional strength and rigidity in the member 

pintle - a relatively small steel pin  engaging the rocker of an expansion bearing, in a sole plate and masonry plate, thereby preventing translation of the rocker ends 

pipe - a hollow cylinder used for the conveyance of water, gas, steam etc. 

piping - a process of subsurface erosion in which surface runoff flows along the outside of a culvert and with sufficient hydraulic gradient erodes and carries away soil around the culvert 

plain concrete - concrete with no structural reinforcement except light steel to reduce shrinkage and temperature cracking 

plan - drawing that represents the top view of a structure and structure site 

plastic deformation -  deformation of material beyond the elastic range 

plate - a  flat sheet of metal greater than 1/8 inch thick 

plate girder - a large I-shaped beam composed of a solid web plate with flange plates attached to the web plate by flange angles or fillet welds 

plug weld - a weld joining two members produced by depositing weld metal within holes cut through one or more of the members; also known as slot weld 

plumb bob - a weight hanging on a cord used to provide a true vertical reference 

plumb line - a true vertical reference line established using a plumb bob 

pneumatic caisson - a caisson in which the working chamber is kept full of compressed air at a pressure nearly equal to the water pressure outside it 

pointing - the compacting of the mortar in the outermost portion of a joint and the troweling of its exposed surface to secure water tightness or desired architectural effect  

ponding -  water backed up in a channel or ditch as the result of a culvert of inadequate capacity  

pontoon bridge - a bridge which floats on pontoons moored to the riverbed; a portion may be removable to facilitate navigation 

pony truss - a through truss having insufficient height to use a top chord system of lateral bracing  

pop-out - conical fragment broken out of a concrete surface by pressure from reactive aggregate particles usually found at the bottom of the hole 

portable bridge - a bridge that may be readily erected for a temporary communication-transport service disassembled and its members again reassembled and the entire structure rendered ready for further service 

portal - the clear unobstructed space of a through truss bridge forming the entrance to the structure 

portal bracing - a system of sway bracing placed in the plane of the end posts of the trusses 

post - a member resisting compressive stresses, located vertical to the bottom chord of a truss and common to two truss panels; sometimes used synonymously for vertical; see COLUMN 

posted - a limiting dimension, speed, or loading indicating larger dimensions and higher speeds and loads can not be safely taken by the bridge 

post-stressing - see POSTTENSIONING 

posttensioning - a method of externally prestressing concrete in which the tendons are stressed after the concrete has been cast 

pot bearing - a bearing type that allows for multi-dimensional rotation by using a neoprene or spherical bearing element 

pot holes - irregular shaped,disintegrated areas of bridge deck or approach pavement concaved by the failure of the surface material 

Pratt truss - a truss with parallel chords and a web system composed of vertical posts with diagonal ties inclined outward and upward from the bottom chord panel points toward the ends of the truss; also known as N-truss  

precast concrete - concrete members which are cast and cured before being placed into their final positions on a construction site 

prestressed concrete - concrete in which cracking and tensile forces are greatly reduced by compressing it with tensioned  cables or bars  

prestressing - applying forces to a structure to deform it in such a way that it will withstand its working loads more effectively; see POSTTENSIONING, PRETENSIONING 

pretensioning - a method of prestressing concrete in which the cables are held in a stretched condition until the concrete has hardened, then the pull on the cables is released inducing internal compression into the concrete 

priming coat - the first coat of paint applied to the metal or other material of a bridge; also known as base coat, shop coat 

probing - investigating the location and condition of submerged footing foundation material using a rod or shaft of appropriate length; checking the surface condition of a timber member for decay using a pointed instrument, e.g., an ice pick 

profile - a section cut vertically through the center line of a roadway or waterway to show the original and final ground levels 

programmed repair -  those repairs that may be performed in a prescheduled program over the next 2 to 24 months