jack—a mechanical device used for applying force to prestressing tendons, for adjusting elevation of forms or form supports, and for raising objects small distances.
jack, flat—a hydraulic jack consisting of light gage metal that is folded and welded to a flat shape that expands under internal pressure.
jack shore—telescoping, or otherwise adjustable, singlepost metal shore.
jacket—an integral covering which is applied over an existing structural element, e.g. a concrete pile, whose primary function is to strengthen or provide environmental protection, or both.
jackhammer—hand-held mechanical breaker for removal of concrete.
jacking device—the device used to stress the tendons for prestressed concrete; also the device for raising a vertical slipform.
jacking force—see force, jacking.
jacking stress—see stress, jacking.
jaw crusher—boom-mounted mechanical crusher for removal of concrete from decks, walls, columns, and other concrete members where the shearing plane depth is 6 ft (1.8 m) or less, pulverizing jaw attachment can debond concrete from steel reinforcement for recycling purposes. (See also mechanical shearing.)
jitterbug—a grate tamper for pushing coarse aggregate slightly below the surface of a slab to facilitate finishing. (See also tamper.)
joint—a physical separation in concrete, including cracks if intentionally made to occur at specified locations; also the region where structural members intersect, such as a beam-column joint.
joint, articulated—a joint with movement limited by restraint.
joint, butt—a plain square joint between two members.
joint, cold—an unplanned joint or discontinuity resulting from a delay in placement of sufficient time to preclude a union of the material in two successive lifts of concrete, mortar, or the like.
joint, construction—interface between two successive placements; bond is typically required at such joints and reinforcement may be continuous.
joint, contraction—formed, sawed, or tooled groove in a repair surface to create a weakened plane and regulate the location of cracking resulting from restrained dimensional change.
joint, control—see joint, contraction (preferred term.)
joint, cross—the joint at the end of individual form-boards between subpurlins.
joint, expansion—(1) a separation provided between adjoining parts of a structure to allow movement where expansion is likely to exceed contraction; or (2) a separation between pavement slabs on grade, filled with a compressible filler material; or (3) an isolation joint intended to allow independent movement between adjoining parts.
joint, groove—see joint, contraction (preferred term).
joint, hinge—any joint which permits rotation with no appreciable moment developed in the members at the joint. (See also joint, Mesnager and joint, semiflexible.)
joint, isolation—a separation between adjoining parts of a structure that allows relative movement in three directions; usually vertical planes located to avoid formation of cracks in the structure. (See also joint, contraction and joint, expansion.)
joint, lift—surface at which two successive lifts meet.
joint, longitudinal—a joint parallel to the length of a structure or pavement.
joint, raked—a masonry-wall joint that has the mortar raked out to a specified depth while it is only slightly hardened.
joint, sawed—a joint cut in hardened concrete, generally not to the full depth of the member, by means of special equipment.
joint, scarf—see connection, scarf.
joint, semiflexible—a connection in which the reinforcement is arranged to permit some rotation of the joint. (See also joint, hinge and Mesnager, joint.)
joint, separation—see joint, isolation (preferred term).
joint, transverse—a joint normal to the longitudinal dimension of a structural element, assembly of elements, slab, or structure.
joint, warping— a joint with the sole function of permitting warping of pavement slabs when moisture and temperature differentials occur between the top and bottom of the slabs, that is, longitudinal or transverse joints with bonded steel or tie bars passing through them.
joint, weakened-plane—see joint, groove and joint, contraction (preferred term).
joint filler—see filler, joint.
joint sealant—see sealant, joint.
joint-sealing compound—see compound, joint-sealing.
joint spall—a fragment detached from a concrete mass adjacent to a joint.
jointer (concrete)—a metal tool approximately 6 in. (150 mm) long and from 2 to 4-1/2 in. (50 to 100 mm) wide and having shallow, medium, or deep bits (cutting edges) ranging from 3/16 to 3/4 in. (5 to 20 mm) or deeper used to cut a joint partly through fresh concrete. (See also jointing.)
jointing—the process of producing joints in a concrete slab. (See also jointer [concrete].)
joist—a comparatively narrow beam used in closely spaced arrangements to support floor or roof slabs (that require no reinforcement except that required for temperature and shrinkage stresses); also a horizontal structural member such as that which supports deck form sheathing. (See also beam.)
jumbo—a specially built mobile carrier used to provide a work platform for tunneling operations, such as installing rock bolts and grouting.
jurisdictional authority––person or entity that has legal control over the applicable building code and permitting procedures for a structure; examples of jurisdictional authorities include local building officials.