MIDTERM NSCP TERMS Flashcards
used to transfer force from pre-stressed reinforcement to the concrete
ANCHORAGE DEVICE
is an anchorage device used with any single strand or a single 16 mm or smaller diameter bar
ANCHORAGE DEVICE, BASIC MONOSTRAND
is an anchorage device with multiple strands bars or wires or with single bars larger than 16 mm diameter
ANCHORAGE DEVICE, BASIC MULTISTRAND
is an anchorage device that satisfies test required
ANCHORAGE DEVICE, SPECIAL
includes the disturbed regions ahead of and behind the anchorage device
ANCHORAGE ZONE
is a concrete in which internal stresses have been introduced to reduce potential tensile stresses in concrete resulting from service loads
CONCRETE, PRESTRESSED
is a conduit, plane, or corrugated to accommodate free stressing reinforcement for post tensioning applications
DUCT
is a stress remaining in prestressing reinforcement after all losses
EFFECTIVE PRESTRESS
temporary force exerted by device that introduces tension into prestressing reinforcement.
JACKING FORCE
is a method of prestressing in which prestressing reinforcement is tensioned after concrete has hardened.
POST-TENSIONING
is a portion of a prestressed member where flexural tension, calculated using gross section properties, would occur under service loads if the prestress force was not present.
PRECOMPRESSED TENSILE ZONE
is a method of prestressing in which prestressing reinforcement is tensioned before concrete is cast.
PRETENSIONING
is a prestressing reinforcement that has been tensioned to impart forces to concrete.
REINFORCEMENT, PRESTRESSED
is a pretensioned reinforcement or prestressed reinforcement in a bonded tendon.
REINFORCEMENT, BONDED PRESTRESSED
is a high- strength reinforcement such as strand, wire, or bar
REINFORCEMENT, PRESTRESSING
is a material encasing prestressing reinforcement to prevent bonding of the prestressing reinforcement with the surrounding concrete, to provide corrosion protection, and to contain the corrosion inhibiting coating.
SHEATHING
is a complete assembly consisting of anchorages, prestressing reinforcement, and sheathing with coating for unbounded applications or ducts filled with grout for bonded applications.
TENDON
is a tendon in which prestressed reinforcement is continuously bonded to the concrete through grouting of ducts embedded within the concrete cross section.
TENDON, BONDED
is a tendon external to the member concrete cross section in post-tensioned applications.
TENDON, EXTERNAL
is a tendon in which prestressed reinforcement is prevented from bonding to the concrete. The prestressing force is permanently transferred to the concrete at the tendon ends by the anchorages only.
TENDON, UNBONDED
is an act of transferring stress in prestressing reinforcement from jacks or pretensioning bed to concrete member.
TRANSFER
is a length of embedded pretensioned reinforcement required to transfer the effective prestress to the concrete.
TRANSFER LENGTH
Φ = 0.60
Plain concrete elements
Φ = 0.65
Bearing
Φ = 0.75
-Shear
-Struts
-Torsion
-Ties
-Brackets
-Bearing areas
-Corbels
-Nodal zones
Φ = 0.85
Post tensioned anchorage zones
Strength reduction factor for Components of connection of precast members controlled by yielding of steel elements in tension
Φ = 0.90
Φ = 0.65 to 0.90
-Moments
-Axial force
-Combined moment and Axial force
Prestress losses shall be considered in the calculation of the effective tensile stress in the prestressed reinforcement, fse, and shall include (a) through (f):
a. Prestressed reinforcement seating at transfer;
b. Elastic shortening of concrete;
c. Creep of concrete;
d. Shrinkage of concrete;
e. Relaxation of prestressed reinforcement;
f. Friction loss due to intended or unintended curvature in post-tensioning tendons.
2 Calculated friction loss in post-tensioning tendons shall be based on experimentally determined ________
wobble and curvature friction coefficients.
special moment frames and special structural walls, prestressing reinforcement shall conform to (a), (b), (c), or (d):
a. ASTM A416M- strand;
b. ASTM A421M - wire;
c. ASTM A421M- low-relaxation wire including, Supplementary Requirement S1 “Low-Relaxation Wire and Relaxation Testing”;
d. ASTM A722M-high-strength bar.
all components of special structural walls including coupling beams and wall piers, cast using precast concrete shall comply with ______
ASTM A416M or A722M.
Effect of loss of area due to open ___ shall be considered in computing section properties before grout in post-tensioning ducts has attained design strength.
ducts
shall include self-weight; applied loads; and effects of prestressing, earthquakes, restraint of volume change, and differential settlement.
Loads
shall include internal load effects due to reactions induced by prestressing with a load factor of 1.0.
Required strength U
For post-tensioned anchorage zone design, a load factor of ____ shall be applied to the maximum prestressing reinforcement jacking force.
1.2
Anchorage and couplers for tendons shall develop at least ____ of fpu
95%
Anchorages and couplers for BONDED TENDONS shall be located so that ____ of fpu shall be developed
100%
Total quantity of As and Aps shall be adequate to develop a factored load at least ____ times the cracking load on the basis of ___
1.2
fr
For ______ , gross concrete area shall consist of the total beam area including the slab thickness and the slab area within half the clear distance to adjacent beam webs
monolithic,
cast-in-place,
post tensioned beam and
slab construction
If the slabs are supported on walls or not cast monolithically with beams, gross concrete area is the slab section _______ to the tendon or tendon group
Tributary
the distance between the face of the beam or wall to the nearest slab tendon shall not exceed ____
1.8m
If spacing of slab tendons exceeds _____, additional deformed shrinkage and temperature reinforcement.
1.4m
is used as a multiplier of √f’c
modification factor, λ
λ = 0.75
All-lightweight
λ = 0.75 to 0.85
Lightweight, Fine blend
λ = 0.85
Sand-Lightweight
λ = 0.85 to 1.00
Sand-Lightweight, Coarse Blend
λ = 1.00
Normal-weight
Composition of aggregates: Fine of Coarse: ASTM C33M
Linear interpolation from 0.75 to 0.85 is permitted based on absolute volume of normal weight ________
fine aggregates
Linear interpolation from 0.85 to 1.00 is permitted based on absolute volume of normal weight ________
coarse aggregates
The value of Δfps shall not exceed _____
250 Mpa
The local zone shall be assumed to be _____
rectangular prism
_______ includes the local zone and shall be assumed to be the portion of the member.
The general zone
_______ anchorage devices shall meet the bearing resistance and local zone requirements of ACI 423.7
Mono strand or single 16mm or smaller diameter bar
______ anchorage devices shall meet the bearing resistance of AASHTO LRFD Bride Design Specfications
Basic multi-strand
AASHTO stands for?
American Association of Highway and Transportation Officials (AASHTO)
LRFD stands for?
Load and Resistance Factor Design (LRFD)
the ____ of the general zone shall be taken as the spacing of the tendons
depth
SIMPLIFIED EQUATIONS
a. Member cross sections are non-rectangular;
b. Discontinuities in or near the general zone cause deviations in the force flow path;
c. Minimum edge distance is less than 1.5 times the anchorage device lateral dimension in that direction;
d. Multiple anchorage devices are used in other than one closely spaced group;
e. Centroid of the tendons is located outside the kern;
f. Angle of inclination of the tendon in the general zone is less than -5 degrees from the centerline of axis of the member, where the angle is negative if the anchor force points away from the centroid of the section;
g. Angle of inclination of the tendon in the general zone is greater than +20 degrees from the centerline of axis of the member, where the angle is positive if the anchor force points towards the centroid of the section.
Centroid of the tendons is located outside the ______
kern
Angle of inclination of the tendon in the general zone is less than ______ from the centerline of axis of the member, where the angle is NEGATIVE if the anchor force points away from the centroid of the section
-5 degrees
Angle of inclination of the tendon in the general zone is greater than _____ from the centerline of axis of the member, where the angle is POSITIVE if the anchor force points towards the centroid of the section.
+20 degrees
For anchorage devices located away from the end of the member, bonded reinforcement shall be provided to transfer at least _____
0.35Ppu
_____ shall be provided parallel to the slab edge
Two horizontal bars at least 12mm ⌀
If the center-to-center spacing of anchorage devices is ____ or less, the anchorage devices shall be considered as a group
300mm
Compressive strength of ____ for single strand or bar tendons
17 Mpa
Compressive strength of ____ for multi strand tendons
28 Mpa
Compressive stress in concrete at nominal strength shall not exceed ____
0.7λf’ci
Maximum design tensile stress for Non-prestressed reinforcement
fy
Maximum design tensile stress for UNBOUNDED, prestressed reinforcement
fse + 70
Maximum design tensile stress for Bonded, prestressed reinforcement
fpy
Slabs prestressed with an average effective compressive stress less than ____ shall be designed as non-prestressed slabs
0.90 Mpa
Prestressed two way slabs shall be designed as ____ with ft ≤ 0.50√ f’c
Class U
Resultant tensile force acting on the portion
Nc
the value of fy shall not exceed ____
420 Mpa
In positive moment areas, length of reinforcement shall be at least _____ and be centered in those areas
ln/3
In negative moment areas, length of reinforcement shall be at least _____ on each side of the face of support
ln/6
In prestresses beams, _____ of thin webs and flanges shall be considered.
buckling
Vu Critical section located ____ from the face of the support for non-prestressed beams.
d
Vu Critical section located ____ from the face of the support for prestressed beams.
h/2
For prestresses beams, the total area of longitudinal reinforcement , As and Aps, at each section shall be designed to resist ______
Mu
_______ shall be attached to the member in a manner that manner that maintains the specified eccentricity
External tendons
For non-prestressed columns and for prestressed columns with average fpe < ____ MPa, area of longitudinal reinforcement shall be at least ______ but shall not exceed ______.
1.6
0.01Ag
0.08Ag
For non-prestressed columns and for prestressed columns with average fpe < 1.60 MPa, the minimum number of longitudinal bars shall be (a), (b), or (c):
a. Three within triangular ties;
b. Four within rectangular or circular ties;
c. Six enclosed by spirals or for columns of special moment frames enclosed by circular hoops.
For prestressed columns with average fpe ≥ 1.6 MPa, transverse ties or hoops need not satisfy the ____ spacing requirement
16db
Precast prestressed concrete piles shall have a specified compressive strength f’c of not less than ____ and shall develop a compressive strength of not less than _____ before driving.
35 MPa
27 MPa
The longitudinal reinforcement shall be high-tensile seven-wire strand conforming to _______.
ASTM Standards
Longitudinal reinforcement shall be laterally tied with _______.
steel ties or wire spirals
Ties or spiral reinforcement shall not be spaced more than _____ apart, center to center, for a distance of 600 mm from the ends and not more than 200 mm elsewhere.
75 mm
At each end of the pile, the first five ties or spirals shall be spaced ______ center to center.
25 mm
Effective prestress shall be based on an assumed loss of _______ in the prestressing steel.
200 MPa
For piles having a diameter of 600 mm or less, wire shall not be smaller than _______
For piles having a diameter greater than 600 mm but less than 900 mm, wire shall not be smaller than ________
For piles having a diameter greater than 900 mm, wire shall not be smaller than ______
5.5 mm (No. 5 B.W.gage).
6 mm (No. 4 B.W.gage).
6.5 mm (No.3 B.W.gauge).
The effective prestress in the pile shall not be less than
______ for piles up to 10 m in length,
_______ for piles up to 15 m in length, and
_______for piles greater than 15 meters in length.
2.5 MPa
4 MPa
5 MPa
The dowels and the faces shall then be joined by ______
Structural epoxy
Prestressing steel shall be _____ in potential plastic regions
unbonded
Anchorages of post tensioning tendons resisting earthquake induced forces shall be capable of allowing tendons to withstand ____ cycles of loading with prestressed reinforcement forces bounded by _______ percent of the specified tensile strength of the prestressing steel.
50
40 and 85
For the upper 20 ft (6 m) of precast prestressed piles, the minimum volumetric ratio of spiral reinforcement shall not be less than ______
0.007
Yield strength of spiral reinforcement
586 MPa
ASTM stands for?
American Society for Testing and Materials
The average prestress, fpc, calculated for an area equal to the smallest cross-sectional dimension of the beam multiplied by the perpendicular cross-sectional dimension shall not exceed the lesser of ______
3.5 MPa and f’c/10
Prestressing steel shall be ______ in potential plastic hinge regions, and the calculated strains in prestressing steel under the design displacement shall be less than _____
unbonded
one percent
Prestressing steel shall not contribute more than ________ of the positive or negative flexural strength at the critical section in a plastic hinge region and shall be anchored at or beyond the exterior face of the joint
one- fourth
Water soluble chloride ion content for bonded tendons shall not exceed _____ when tested with ________
0.06
ASTM C1218M
Modulus of elasticity for prestressing
Ep
Tensile strength for prestressed
fpu
Maximum value of fpu for
Type: Strand (Stressed relieved and low relaxation)
ASTM 416M
1860 Mpa
Maximum value of fpu for
Type: Wire (Stressed relieved and low relaxation)
ASTM 421M
1725 Mpa
Maximum value of fpu for
Type: High strength bar
ASTM 722M
1035 Mpa