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221 Cards in this Set
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- Back
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Add tendons |
Tendons usually short in length placed in specific locations such as end bays to increase structural capacity |
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Anchor |
For monostrand tendons, normally a ductile iron casting which houses the wedges and is used to transfer the Prestressing force to the concrete |
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Anchorage |
Mechanical device comprising all components required to anchor the prestressing steel and permanently transmit the prestressing force to the concrete |
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Anchor cavity |
The opening in the anchor designed to accommodate the strand passing through and the proper seating of the wedges. |
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Anchorage zone |
The region in the concrete adjacent to the anchorage subjected to stresses resulting from the prestressing force. |
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Back-up bars |
Reinforcing steel used to control the tensile splitting forces in the concrete |
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Banded tendons |
Groups of closely spaced tendons placed together |
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Barrel anchor |
A cylindrical metal device housing the wedges |
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Barrier cable |
High strength steel strands erected around the perimeter of a structure and at open edges of ramps |
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Bearing plate |
A metal plate which bears directly against the concrete and is part of an overall anchorage system. |
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Blowout |
Concrete failure which occurs during or after stressing |
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Bonded tendon |
Annular space around the prestressing steel strands are grouted after stressing |
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Bursting steel |
Rebar used to control the tensile bursting forces developed at the bearing side of the anchor |
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Camber |
An upward deformation caused by the application of a prestressing force |
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Cantilever |
Any horizontal structure member projecting beyond its vertical support. |
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Chair |
Hardware used to support or hold post-tensioning tendons in their proper position and prevent displacement |
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Coating |
Material used to protect against corrosion and reduce friction |
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Concrete slurry |
Cementitious paste mixed with aggregate fines |
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Coupler |
Device, normally spring loaded for connecting two strand ends together |
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Creep |
The time dependent deformation (shortening) of prestressing steel or concrete under sustained stress (load). |
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Detensioning |
Releasing the prestressing force from the tendon |
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Distributed tendons |
Single or group of tendons uniformly distributed, usually perpendicular to banded tendons and spaced 8 times the slab thickness or 5 feet |
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Edge form |
Form Work used to limit the horizontal spread of Fresh concrete on flat surfaces |
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Edge form |
Form Work used to limit the horizontal spread of Fresh concrete on flat surfaces |
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Effective prestress |
The prestressing force at a specific location in a prestressing concrete member after all losses have occurred. |
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Elastic shortening |
The shortening of a member which occurs immediately after the application of the prestressing force. |
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Elastic shortening |
The shortening of a member which occurs immediately after the application of the prestressing force. |
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Elongation |
Increase in the length of the prestressing steel |
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Elastic shortening |
The shortening of a member which occurs immediately after the application of the prestressing force. |
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Elongation |
Increase in the length of the prestressing steel |
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Encapsulated system |
A system which provides watertight connections at all stressing. |
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Elastic shortening |
The shortening of a member which occurs immediately after the application of the prestressing force. |
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Elongation |
Increase in the length of the prestressing steel |
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Encapsulated system |
A system which provides watertight connections at all stressing. |
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Fixed-end anchorage |
The anchorage at the end of the tendon which is usually installed prior to the tendon arriving onsite. |
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Force |
The product of the mass of an object by its acceleration. |
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Force |
The product of the mass of an object by its acceleration. |
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Fiction loss |
The stress loss in a prestressing tendon resulting from friction created due to wobble and/or profile of the tendon |
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Hand seating tool |
Hand held device used to properly seat the wedges in the anchor |
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Hand seating tool |
Hand held device used to properly seat the wedges in the anchor |
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Initial prestress |
The stress in the tendon immediately after transferring the prestressing force to the concrete. |
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Hand seating tool |
Hand held device used to properly seat the wedges in the anchor |
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Initial prestress |
The stress in the tendon immediately after transferring the prestressing force to the concrete. |
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Intermediate anchorage |
An anchorage located at any point along the tendon length, which can be used to stress a given length of a tendon without the need to cut the tendon. |
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Jack grippers |
Wedges used in the jack to hold the strain during stressing |
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Jack grippers |
Wedges used in the jack to hold the strain during stressing |
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Jack gripper plates |
Steel plates designed to hold the jack grippers in place |
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Jack grippers |
Wedges used in the jack to hold the strain during stressing |
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Jack gripper plates |
Steel plates designed to hold the jack grippers in place |
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Jacking force |
Maximum temporary force exerted by the jack |
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Jack grippers |
Wedges used in the jack to hold the strain during stressing |
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Jack gripper plates |
Steel plates designed to hold the jack grippers in place |
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Jacking force |
Maximum temporary force exerted by the jack |
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Monostrand |
One single strand |
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Jack grippers |
Wedges used in the jack to hold the strain during stressing |
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Jack gripper plates |
Steel plates designed to hold the jack grippers in place |
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Jacking force |
Maximum temporary force exerted by the jack |
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Monostrand |
One single strand |
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Multi-use splice chuck |
A coupler which uses 3 piece wedges and is made for repeated use |
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Jack grippers |
Wedges used in the jack to hold the strain during stressing |
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Jack gripper plates |
Steel plates designed to hold the jack grippers in place |
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Jacking force |
Maximum temporary force exerted by the jack |
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Monostrand |
One single strand |
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Multi-use splice chuck |
A coupler which uses 3 piece wedges and is made for repeated use |
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MUTS |
Minimum ultimate tensile strength |
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Jack grippers |
Wedges used in the jack to hold the strand during stressing |
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Jack gripper plates |
Steel plates designed to hold the jack grippers in place |
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Jacking force |
Maximum temporary force exerted by the jack |
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Monostrand |
One single strand |
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Multi-use splice chuck |
A coupler which uses 3 piece wedges and is made for repeated use |
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MUTS |
Minimum ultimate tensile strength |
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Nose-piece |
The front part of the jacking device that fits into the stressing pocket. |
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Partial prestressing |
Prestressing of Concrete to the stress levels such that tensile stresses can exist under design service loads. |
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Pocket former |
A temporary device used at the stressing-end during casting of the Concrete to provide an opening to the anchor cavity |
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Post-tensioning |
Prestressing of tendons are tensioned after the Concrete had hardened. |
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Post-tensioning |
Prestressing of tendons are tensioned after the Concrete has hardened. |
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Pressure |
Force acting per unit area |
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Prestress |
To place a material (Concrete) in a state of compression prior to the application of loads |
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Prestress |
To place a material (Concrete) in a state of compression prior to the application of loads |
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Prestressed concrete |
Concrete in which internal stresses are induced by means of prestressing steel tendons. Two methods- posttensioned prestressing and pretensioned prestressing |
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Prestressing steel |
High Strength steel which is used to prestress concrete, commonly it is seven wire Strand or bar. |
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Profile |
The outline or path a tendon follows in the concrete from End to end |
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P/T coating |
Corrosion inhibiting coating material meeting or exceeding the performance criteria of the PTI specifications for unbonded single strand tendons |
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Seating loss |
The relative movement of the wedges into the anchor cavity during the transfer of the prestressing force to the anchorage resulting in some loss of prestressing force |
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Sheathing |
A material covering forming an enclosure in which the pre-stressing steel is encased to prevent bonding during concrete placement, to provide corrosion protection and to contain the P/T coating. |
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Slab bolster |
Continuous hardware used to support or hold post tensioning tendons at the bottom of the slabs |
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Split pocket former |
A temporary two-piece device used at the intermediate and during casting of the concrete to provide an opening in the concrete, allowing the stressing equipment access to the anchor cavity |
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Stage stressing |
Sequential stressing of tendons in separate steps or stages in Lieu of stressing all the tendons during the same stressing operation |
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Strand |
High strength steel wires twisted around a center wire. For unbonded tendons, seven wire strand conforming to ASTM a –416 is almost exclusively used |
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Strength |
A body or objects capacity to exert or resist force |
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Stresses |
Internal forces acting on adjacent parts of a body |
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Stresses |
Internal forces acting on adjacent parts of a body |
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Stressing end |
The Anchorage at the stressing end of a tendon which is used to stress the prestressing steel |
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Stressing equipment |
Consists normally of a jack, pump, hoses, and a pressure gauge |
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Tendon |
A complete assembly consisting of anchorages, prestressing steel, P/t Coding and sheathing. |
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Tendon |
A complete assembly consisting of anchorages, prestressing steel, P/T coating and sheathing. |
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Tendon tail |
The excess strand protruding from the stressing end anchor |
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Tensile stresses |
Internal forces directed away from the part of a body on which they act |
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Tensile stresses |
Internal forces directed away from the part of a body on which they act |
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Tension |
The effect of tensile forces on a body |
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Troubleshooting anchor |
A tendon in which the prestressed steel is prevented from bonding to the concrete |
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Wedges |
Pieces of tapered metal with teeth, which bite into the prestressing steel during transfer of the prestressing force. The teeth are beveled at the front end to a sure gradual development of the tendon force over the length of the wedge. Two-piece wedges or normally used for monostrand tendons. |
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Wobble friction |
The friction caused by the unintended horizontal deviation of the tendon |
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What is prestressed concrete? |
Concrete members, such as beams and slabs in which internal stresses are induced by means of prestressed reinforcement |
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True or false: Is concrete very strong in compression but relatively weak in tension? |
True |
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Concrete has to be at what percent strength before the tendon can be pulled? |
75% |
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When are tendons in tension and the concrete is in compression? |
When you stress the tendons to 33kips |
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Pre-tensioned prestressed concrete |
Steel tendons are stressed before the concrete is placed, at a precast plant remote from the construction site |
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Post-tensioned prestressed concrete |
Still tendons are stressed after the concrete has been placed and gain significant street at the construction site. |
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Where are prestressing strands stressed between? |
Two buttresses anchored to a stressing bed which holds the force in the stretched bare strand |
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Post-tensioned prestressed concrete provides what 7 Advantages over pre-tensioned prestressed concrete |
1. Structural continuity of members 2. Stage prestressing 3. Field prestressing 4. Reduced pre-stress losses 5. Field connections for precast elements 6. Construction and limited or restricted access areas 7. use of local labor and materials |
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Two types of commonly framed concrete structures |
1. One way slab or joist supported by bench supported by columns/walls.
2. Two-way slabs, with or without drop panels supported by columns/walls. |
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Concrete is efficient in taking what kind of stress? |
Compressive stress |
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Concrete is efficient in taking what kind of stress? |
Compressive stress |
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Post tensioning tendons and rebar are efficient in taking what kind of stress? |
Tensile stress |
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A slab or Beam supporting its own weight or supporting its own weight and uniform load bends or deflects which way? |
Downward |
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In cases of significantly different span lengths and/or differences in load magnitude what can be done? |
1. Reduce the drape while still keeping the same amount of pre-stress
2. Maintain the full drape but reduce the pre-stress force |
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In the case of post-tensioned ground supported foundations, the loads applied to the slab come from where? |
Above (the structure) and below (the soil) |
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Post tensioned ground supported Slabs do or do not attempt to take advantage of any uplift by draping the tendons |
Do not |
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Are tendons in ground supported foundation slab’s flat or draped? |
Flat |
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The designer of ground supported foundation slabs use only the blank forced induced into the slab by the tendons as they blank the concrete slab together, which increases the slabs blank strength. ? |
Compressive Compress Tensile |
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If tendons are draped, or placed above or below the neutral axis of the concrete, the result can be unintended blank or blank forces being induced into a slab. |
Uplift or downward |
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Most post tension ground supported slabs do not attempt to take advantage of any blank by draping the tendons. |
Uplift |
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What are the pertinent documents needed to provide a trouble free installation and stressing? |
Installation drawings, shipping lists, material certifications, Jack calibrations and stressing records. |
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The issued for construction drawings should detail what? |
Number, size, length, marking, elongation, profile and location of all tendons, as well as the tendon support plan and bursting steel requirements |
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All tendons should be stored in a dry area on blank to keep the tendons off the ground. |
Dunnage |
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Vertical deviations for elevated concrete with depths up to 8 inches should be kept to what tolerance? |
+/- 1/4” |
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Vertical deviations for elevated concrete with Depths greater than 8 inches up to 24 inches should be kept to what tolerance? |
+/- 3/8” |
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Vertical deviations for elevated concrete with depths over 24 inches should be kept to what tolerance? |
+/- 1/2” |
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Vertical deviations for slabs on ground up to 5 inches thick should be kept to what tolerance? |
+/- 1/2” |
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Vertical deviations for slabs on ground over 5 inches thick should be kept to a tolerance? |
+/- 10% Of the slab thickness not to exceed 1 inch |
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Vertical deviations for slap on ground draped beam tendons should be kept at what tolerance? |
+/- 1” |
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When tendons are designed for use in an aggressive environment, the tendon is required to be blank over it’s entirely. |
Watertight |
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Bottom back bar should also be placed on blank. |
Forms |
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Unroll the tendons in the proper location beginning from the blank and then uncoil them toward blank. |
Fixed-end Stressing-end |
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Unroll the tendons in the proper location beginning from the blank and then uncoil them toward blank. |
Fixed-end Stressing-end |
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When stressing tendons from both ends you must leave how much tendon tail outside the edge form at each end for stressing? |
12” minimum |
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Unroll the tendons in the proper location beginning from the blank and then uncoil them toward blank. |
Fixed-end Stressing-end |
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When stressing tendons from both ends you must leave how much tendon tail outside the edge form at each end for stressing? |
12” minimum |
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Just enough sheathing should be removed so that not more than blank inches of greased strand exists behind the anchor. |
1” |
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What are pocket formers designed to prevent? |
Concrete slurry from entering into the anchor cavity |
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What can be used to prevent excess coated strand from being exposed? |
Split plastic tube, a protection sleeve, or sheathing removed from the stressing tail and butt tightly against the anchor face |
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What can be used to prevent excess coated strand from being exposed? |
Split plastic tube, a protection sleeve, or sheathing removed from the stressing tail and butt tightly against the anchor face |
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Not more than blank diameter tendons and more than blank diameter tendons should be banded in a group? |
5- 1/2” diameter 4 - 0.6” diameter |
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If tendons are not placed into Anchorage correctly what could happen? |
Strand breakage, blowout, wedge seating failure, low elongation, excessive seating loss or other stressing problems |
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What is the minimum clearance that should be maintained around all blockouts? |
6” |
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For larger openings, it is always desirable to reinforce the top and bottom of the slab at openings with blank bars to control blank initiated at the corners of the opening |
Diagonal Cracking |
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The fixed end Anchorage should be secured in its proper position using support blank and anchor zone reinforcement |
Chairs |
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Tendon placing at low points will have support bars shown typically blank feet on center |
4’ |
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Main slab tendons are placed before or after the beam tendons are installed? |
After |
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If a conflict occurs and the anchors cannot be placed for slab on ground they may be moved horizontally up to blank inches in either direction. |
12” |
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How many inches should be maintained between the outside face of the Anchorage and the edge form? |
1 1/2” |
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How many inches should be maintained to allow adequate concrete coverage over the end of the strand that protrudes through the Anchorage? |
3/4” |
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How should you properly straighten tendons? |
Pulling the tendon from the stressing end against the fixed-end Anchorage that has been attached to the edge form. |
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What are typically placed at each tendon intersection and halfway between intersections in cases where the tendon spacing exceeds 4’6”? |
Chairs |
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When slab tendons Cross a transition area such as a dropped or raised area less than 12 inches what is the ratio of the transition that should be made for the tendons? |
1:6 ratio |
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How should intersecting slab tendons be secured? |
Using tie wire beginning at the fixed end then working toward the stressing end |
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How many inches of sheathing has to be removed in front of the bearing side of the anchor to provide significant length for the Jack grippers? |
12”-18” |
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Blank blank or other materials containing blank show not be used as an admixture and post tension concrete. |
Calcium chloride Chloride |
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For a successful Anchorage to be completed what are the six area is working simultaneously? |
Anchor, strand, wedges, storage and condition of materials, condition and calibration of stressing equipment, working knowledge to understand and follow procedures correctly |
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Acceptable anchorage system must pass a static load test of blank percent at the minimum Ultimate Tensile strength of the strand |
95% |
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The blank is designed to compensate for all the inherent irregularities between the seven wire strand and the tapered bearing surface of the anchor |
Wedge |
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The blank is harder than the anchor and the blank is harder than the strand. |
Strand Wedge |
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True or false Longitudinal cracking of a wedge will frequently occur due to the amount of movement the wedge will undergo when conforming to its final position |
True |
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In stressing operations where two or more extensions of the stressing Jack are required to achieve the required elongation, the final stress should be precalculated to use an approximately blank percent of the full stroke of the jack on the final pull. |
60% |
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Preparations for stressing |
Edge form should be removed remove pocket former clean out anchor cavity check integrity of concrete check that the tendon is perpendicular to the anchor Remove excess P/T coding any dirt Replace any P/T coding that has been removed Install the wedges evenly Seat the wedges |
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The seating plunger that is fully retracted should be approximately blank inches below the end of the nose piece. |
5/8” |
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When using an 8 inch stroke Jack try to leave approximately blank inches for the final pull |
5” |
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What is the acceptable tolerance for tendons used in residential and light commercial ground supported slaps |
+/-10% |
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What is the acceptable tolerance for tendons used in residential and light commercial ground supported slaps |
+/-10% |
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What is the acceptable tolerance for tendons used in all other applications? |
+/-7% |
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The wedges should be placed and set with what kind of tool? |
Hand seating tool |
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Marking tendons should be marked from what? |
Anchor |
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What should the strand length protruding beyond the wedges be between, after cutting? |
1/2”-3/4” |
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Strands maybe cut by which approved methods? |
Oxyacetylene Cutting, abrasive wheel or hydraulic shears |
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For encapsulated systems a watertight cap filled with P/T coating shall be installed within blank hours but not to exceed blank hours |
24hrs 96hrs |
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What are the only type of slings that are allowed for handling of tendons? |
Nylon |
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The capping of the stressing ends shall be accomplished by what? |
cleaning of the pocket and installing a cap Filled with an approved P/T coating. |
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The capping of the stressing ends shall be accomplished by what? |
cleaning of the pocket and installing a cap Filled with an approved P/T coating. |
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The final step of an encapsulated system is what? |
Stressing, cutting, capping, and grouting of the stressing pockets |
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Where are barrier cables installed? |
Along ramps, around the perimeter of the structure or anywhere a car or a person has potential of going off the edge of the slab. |
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What is the most common strand size used for barrier cables? |
1/2” |
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In a typical parking structure where is the first barrier cable placed? |
4” Above the slab then placed 4” on center to a height of about 3’6” or about 11 strands |
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What are the two methods of installing barrier cables? |
First one is to thread the cables through plastic sleeves located in the interior columns and then anchored to the end columns.
Second one is to attach the cables to the edge of interior and end columns with structural steel tubes, angles or channels |
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Anchoring cables end columns
Anchorage lock off behind the column normally employs an anchor on blank end. |
Each |
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Anchoring cables end columns Method 1
Anchorage lock off behind the column normally employs an anchor on blank end. |
Each |
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Anchoring cables end columns Method 2
The anchor/insert method employs a special blank device which threads into an insert placed into the leading face of the blank columns |
Anchoring End |
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True or false:
Anchoring cables at the end columns, method 2, backstressing is not required to properly set the wedges in the anchoring devices. |
False |
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Is back stressing required for anchoring the cables at the end columns, method 1? |
Yes |
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Are barrier cables accessible for repairs and maintenance? |
Yes |
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At each column edge, for installation, attach a blank, blank or blank near the center of the column. |
Tube, angle or channel |
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For installation of cables at edge of columns, how many piece wedges are needed into each anchor at each end? |
2-3 |
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True or False:
When stressing steel tubes, angles or channels is it required that the Anchorage at the non-stressing-end be installed to a force equal to 80% of the ultimate strength of the strand. |
True |
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When stressing steel tubes, angles or channels will the lateral force required to properly seat wedges exceed the column design criteria? |
Yes |
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Is backstressing required when seating the wedges for stressing steel tubes, angles or channels?
If so, when Must it be done? |
Yes After the cables are stressed to the required force. |
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Are elongation records required when stressing barrier cables? |
No, since there’s no way to determine at which point the SAG of the cable has been eliminated and when you actually start to elongate the cable |
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Tendon tails may be cut using what? |
OXYACETYLENE torch, a metal cut-off saw with a reinforced bonded metal cutting blade, or a pocket-shear |
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True false
Barrier cable finishing is accomplished in the same way as tendon finishing, using the anchor/insert method or the cables are installed at the edge of the columns |
False |
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When using galvanized strand, how many coats of GALVANEX or equal must be applied where Jack gripper teeth have marked the barrier cable during backstressing |
2 |
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Where Epoxy or polyester coated cable is used any damage caused by blank must be repaired |
Backstressing |
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What is considered the high stress zone? |
The area behind the anchors (18 inch behind the anchor and from the back of the anchor at 45° angle’s on each side) |
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For encapsulated system the sheathing should be connected to the what? |
Anchor |
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What is the maximum length of greased unsheathed strand behind an anchor? |
1” |
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If more than blank inches is exposed the unsheathed area is excessive, repair the sheathing right up to the back of the blank |
1” Anchors |
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If obstructions are in the way make a circular cut on the sheathing blank inches to blank inches back from the anchor, slide the sheathing forward until it touches the anchor and then repair the bare spot. |
18”-24” |
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What is the most common cause for wedges to fail to hold the strand? |
Concrete slurry in the wedge seat of the anchor cavity. |
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When patching, use a high strength blank concrete grout mix, with a blank binder. |
Non-shrink Epoxy |
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What are the most common causes of blowouts? |
Rock pockets, San pockets or voids, lack of anchorage zone reinforcement or reverse tendon curvatures |
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Depending on the location and severity of the blowout, blank tendons may have to be blank before concrete removal can begin. |
Adjacent Detensioned |
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Strand breakage can occur how? |
Misalignment of wedges, over stressing and/or internal damage to the tendon |
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Misalignment of wedges occur when? |
Wedges are offset prior to stressing |
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If a tendon is too short to stress using a standard Jack what can be done? |
Removing the nose piece and using jack feet
Or by using a coupler with a short piece of strand fixed on one end of the coupler |
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Coupler installation
Should couplers be located side by side when installing? |
No |
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If more than one tendon requires splicing, couplers should be blank at half bay increments per tendon group |
Staggered |
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How is a lift off conducted? |
Using a standard post tensioning stressing jack on a specified tendon to determine the force in the tendon |
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When a lift off is performed you will have to overstress the blank of the tendon to pull the wedges out of the anchor thus allowing the strand to be free of the blank |
Tail Anchor |
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To perform a lift off you should start by opening the jack at least blank inches |
4” |
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You should never go above blank percent of the force in the tendon to accomplish a lift-off? |
85%
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What is the common cause for excessive seating-loss? |
Concrete slurry into the anchor cavity |
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Power cord should not be less than blank gauge and should not be longer than blank feet. |
12 gauge 100’ |
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Which end of the tendon is the pocket former located? |
Stressing end |
