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PRESTRESSED CONCRETE DESIGN EXAM NEWEST
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When a tendon is stressed at an intermediate location, the remainder of the tendon should ---------CORRECT ANSWER-----------------remain coiled until the next pour sequence is ready for tendon placement When inspecting a post- tension installation, the inspector is responsible for checking all of the following except ---------CORRECT ANSWER--------------- --verify that the contractor has stressed the fixed-end anchorages to ensure wedges have been seated The jacking force specified for 1/2- inch diameter tendons is normally --------
- CORRECT ANSWER-----------------33 kips The inspection of a post- tension system is the responsibility of --------- CORRECT ANSWER-----------------The engineer of record ,the special inspector , the general contractor, and a PTI certified installer Temperature tendon profiles will ---------CORRECT ANSWER----------------- remain at a constant height throughout the slab The edge form should be marked showing the center of each post tension tendon from ---------CORRECT ANSWER-----------------The approved installation drawings
All of the following can affect tendon elongation field measurements except ---------CORRECT ANSWER-----------------the jack extends or retracts slowly Prior to stressing tendons, the inspector should check that --------- CORRECT ANSWER-----------------the tendon is perpendicular to the anchor & the amchor is parallel to the face of the concrete, unless the plans specify a different angle During stressing operations,the special inspector ---------CORRECT ANSWER-----------------should measure the tendon elongations after each cable is stressed The last calibration date of the stressing equipment must ---------CORRECT ANSWER-----------------not exceed 6 months from the stressing date Cleaning the tendon tails prior to stressing improves ---------CORRECT ANSWER-----------------The consistency and permanence of the paint mark & the efforts to keep the underside of the jack clean A contractor pursuing approval for submittal items prior to construction ------ ---CORRECT ANSWER-----------------shop drawings and design drawings showing detailed engineering and installation The transition between the corrosion protection for the bond and free stressing lengths shall be designed to ensure ---------CORRECT ANSWER- ----------------continuous protection from corrosive attack
Type II Portland cement shall be used for grouting anchor system provided that ---------CORRECT ANSWER-----------------the sulfate content is between 0.1 and 0.2 percent Grout socks must conform to ---------CORRECT ANSWER----------------- ASTM D 4751 Plastic tubing wall thickness is acceptable for use in anchorage systems when ---------CORRECT ANSWER-----------------its normal thickness for PVC os .040 inches The test method for the melting point of wax ---------CORRECT ANSWER--- --------------is ASTM D- 566 A trumpet should have a minimal wall thickness of ---------CORRECT ANSWER-----------------.125 inches A permanently free stressing length in a soil anchor can be protected by all of the following except ---------CORRECT ANSWER-----------------epoxy The minimum free stressing length for a prestressing steel bar is --------- CORRECT ANSWER-----------------10 feet
Centralizers in an anchorage system should be spaced ---------CORRECT ANSWER-----------------at 10 feet on center or less The corrosion protection surrounding the unbonded length of the tendon --- ------CORRECT ANSWER-----------------shall not contact the bearing plate or the anchorhead ___ are approved for repair on damaged corrugated sheath --------- CORRECT ANSWER-----------------a heat shrink sleevs or heat shrink tape Drill bits used to drill a hole for an anchor ---------CORRECT ANSWER------- ----------must not be more than 1/8th-inch smaller than the diameter of the drill hole The temperature of grout at the time of the placement must --------- CORRECT ANSWER-----------------not exceed 90A when ambient temperatures rise above 100A and be balanced with the use of a suitable admixture that will prevent the grout from flash setting when ambient temperatures rise above 100A and its unavoidable that the grout temperature would rise above 90A Fahrenheit When handling prestressing steel on site, care should be taken --------- CORRECT ANSWER-----------------not to expose the prestressing steel to a heat source above 450A Fahrenheit If the drilling subcontractor plans to dill and anchor hole at 3:00pm today for an anchor that will not be installed tomorrow morning at 7:00 am , the the
in prestressed concrete members ---------CORRECT ANSWER----------------- Steel is in Tension Concrete is in Compression Give atleast 3 reasons for prestressing: ---------CORRECT ANSWER--------- --------1. Eliminate cracking at service loading conditions.
- Improve shear and torsion strengths
- Add protection to the steel A Sufficient precompression to ensure "Cracked free" at full design load. By Freyssinet 1930 ---------CORRECT ANSWER-----------------Full prestressing Pre composition is not sufficient to prevent the cracks and it is commonly used. ---------CORRECT ANSWER-----------------Partial Prestressing Method of mechanical prestressing when concrete is cast around the prestressing tendon against external abutment. ---------CORRECT ANSWER-----------------Pre Tensioning Method of designing prestressed beam.And Have chosen to provide upward load or equal and opposite to the given downward load. --------- CORRECT ANSWER-----------------Load Balancing It Increases under increasing applied load. ---------CORRECT ANSWER----- ------------Internal Lever Arm
A homogeneous and Elastic ---------CORRECT ANSWER----------------- Prestressed Beam What are the Basic concepts? ---------CORRECT ANSWER-----------------1. Combined loading concept
- Internal Couple concept
- Equivalent load concept(Load balancing) What are the stages in a Prestressed Concrete beam? ---------CORRECT ANSWER-----------------1. Casting
- Stressing
- Transfer (temporary load)
- Loading (specified load) It considers simply supported beam prestressed w/ deaped tendon. --------- CORRECT ANSWER-----------------Internal Couple Concept It is Useful in design and gives some idea to the eccentricity which can be given to the prestressing force once the cross section has been selected. -- -------CORRECT ANSWER-----------------Internal Couple It is assumed parabolic ---------CORRECT ANSWER----------------- Equivalents load concepts (load balancing) A negative sign that indicates the load is acting upward on concrete load balancing method of design. ---------CORRECT ANSWER----------------- Equivalents Loading
In ____ , Engineer of San Francisco, Callifornia named ____________ obtained patents for tightening steel tie rods in artificial stones and concrete arches to serve as floor slabs ---------CORRECT ANSWER----------------- 188 6, P.H Jackson In ____, C. E. __________ of Germany , Independent secured a patent for concrete reinforced with metal that had tensile stress applied to it before the slab was loaded. ---------CORRECT ANSWER-----------------1888, W. Doehring in ____, ________ of United Stated suggested possibility of retighting the reinforcing rods. ---------CORRECT ANSWER-----------------1908, C.R. Steiner in ____, ____________ of Nebraska tried high strength steel bars coated to prevent bond with concrete by means of NUTTS. ---------CORRECT ANSWER-----------------1925, R.E Dill In what year that the Modern Development Of Prestressed Concrete by Freyssinet developed?? ---------CORRECT ANSWER----------------- 1928 How many total loss due to shrinkage and creep of concrete? --------- CORRECT ANSWER-----------------0. From Germany who applied practical application of scheme pretensioning where the steel was bonded to the concrete without end anchorage. --------- CORRECT ANSWER-----------------E. Hoyer
it consist of stretching wires between two buttresses hundred feet apart. ---- -----CORRECT ANSWER-----------------Hoyer System in ______, ________ developed conical wedges for end anchorages and designed double acting Jacks. ---------CORRECT ANSWER----------------- 1939, Freyssinet When did Professor G. Magnel of Belgium developed the Magnel System? ---------CORRECT ANSWER----------------- 1940 says that 2 wires were stretched at a time ---------CORRECT ANSWER------ -----------Magnel System In what year did the 47% of all bridges built in Germany? ---------CORRECT ANSWER----------------- 1965 How many percent % of all bridges built in Germany? ---------CORRECT ANSWER-----------------47% In 1978, Soviet Russia annually produced ______ m3 of prestressed concrete ---------CORRECT ANSWER-----------------25 Million
When did PCI formed? ---------CORRECT ANSWER----------------- 1954 In ______, The introduction of PCI's " Prestressed Concrete Handbook" and also the acceptance of P.C as structural designers ---------CORRECT ANSWER----------------- 1971 Classification and types ---------CORRECT ANSWER-----------------1. Externally /Internally Prestressed
- Linear/Circular Prestressing 3.. Pretensioning & Posttentioning
- End- Anchored / Non-End- Anchord tendons
- Bonded/Unbonded tendon
- PreCast, Cast in Place, Composite construction
- Partial & Full prestressing It is where the arch was prestressed by jacking against its abutments. ------- --CORRECT ANSWER-----------------Externally or Internally Prestressed Term applied to prestressed concrete in circular structures such as Round tanks, silos and pipes. ---------CORRECT ANSWER-----------------Circular Prestressing Any method of prestressing in which the tendons are tensioned before concrete is placed. ---------CORRECT ANSWER-----------------Pretensioning
Method of prestressing in which the tendons are tensioned after the concrete has hardened. ---------CORRECT ANSWER----------------- Posttensioning It is bonded throughout their length to the sorrounding concrete --------- CORRECT ANSWER-----------------Bonded tendon Protection from corrosion must be provided by galvanizing, greasing is greased & wrapped with paper of plastic material ---------CORRECT ANSWER-----------------Unbonded tendon Involves the placing of concrete away from its final position --------- CORRECT ANSWER-----------------Precast It requires more form and falsework ---------CORRECT ANSWER-------------- ---Cast in Place The procedure of economical to pre cast part of a member , erect it, and then cast remaining portion in place ---------CORRECT ANSWER-------------- ---Composite construction The concrete is said to be ________ when a member is designed so that under the working load there are no tensile stress in it ---------CORRECT ANSWER-----------------Full Prestressing
form of concrete in which internal stresses are introduced by means of high strength pre strained reinforcement ---------CORRECT ANSWER-------------- ---Prestressed Concrete Prestressed relies on _______ or __________ to achieve stress transfer to concrete. ---------CORRECT ANSWER-----------------bond or bearing mechanism Induce internal actionsof such magnitude distribution to counter actthe external loading ---------CORRECT ANSWER-----------------Prestressing Forces It combines concrete and steel bars ---------CORRECT ANSWER-------------- ---Reinforced Concrete combines high strength with high strength steel in an "active manner" ------- --CORRECT ANSWER-----------------Prestressed Concrete What is prestressed concrete ---------CORRECT ANSWER-----------------The tensioning of steel - stranded cables prior to concrete placement. the tensioning of steel- stranded cables after concrete has been placed and hardened. Concrete that has recieved a tensile load prior to any service loads. The use of a prestressed concrete system will achieve the following --------- CORRECT ANSWER-----------------Reduced thickness of concrete, less traditional reinforcing steel, and adequate crack control
Once tensioned, Tensioning cables are held securely in a tensioned state by ---------CORRECT ANSWER-----------------wedges that have been seated The end of a cable that terminates within a concrete slab,thus rendering it inaccessible from outside the concrete is known as ---------CORRECT ANSWER-----------------the dead emd The presence of sheathing on a wire-stranded cable indicates that --------- CORRECT ANSWER-----------------it will be used in an unbonded system application The most common post-tension cable tendons in use today are made up of ---------CORRECT ANSWER-----------------steel strands of wire wrapped together In a unbonded system, the force applied to the concrete after tensioning ---- -----CORRECT ANSWER-----------------comes from the anchorage zone only Post-tension manufacturing plants must be certified by ---------CORRECT ANSWER-----------------PTI unbonded plant certification program Prior to cutting the tendon tails after tensioning,the field records of stressing activities must be forwarded to and approved by ---------CORRECT ANSWER-----------------the engineer of record
On a two-way flat plate,a minimum of __ over each column first --------- CORRECT ANSWER-----------------2 uniform tendons should be placed A minimum of _- of tendon tail must be available at the stressing end. ------- --CORRECT ANSWER----------------- 12 inches When installing a post-tension system,the installer should have a minimum of ---------CORRECT ANSWER-----------------5 years experience, be a PTI certified installer, and use the same crew that installs the system to stress the system The layout and installation of post- tension cables ---------CORRECT ANSWER-----------------takes precedence over the placement of electrical and mechanical conduit & other necessary reinforcing steel First and foremost, it is the responsibility of the __ to review the post- tension installation during placement ---------CORRECT ANSWER------------- ----Installer No more than __ tendons should be bundled into the group --------- CORRECT ANSWER-----------------1/2 dia tendons and those (4) 6" dia. tendons When installing post- tension cables, all of the following practices are acceptable except ---------CORRECT ANSWER-----------------In order to facilitate removing the pocket former after concrete has been placed,
applying PT coating to grease the outer surface of the pocket former during cable installation Tolerance on the vertical placement of post- tension cables is limited to ----- ----CORRECT ANSWER-----------------1/2 when placed in a 48-inch thick concrete member When tying a tendon in place ,the installer, as a matter of practice, should - --------CORRECT ANSWER-----------------tie the tendon, support bar, and chair as a single unit. Tensioning cables should not begin until ---------CORRECT ANSWER-------- ---------concrete cylinder breaks show that member has attained the minimum compressive strength specified for stressing on the project plans When preparing for stressing, it is necessary to ---------CORRECT ANSWER-----------------Check to make sure the stressing equipment is clean, especially the jack gripper and seating plunger areas,remove PT coating from the tendon and clean out the anchor cavity, and seat the wedges with use of hand seating tool __ is an acceptable field measured elongation of a tendon with a theoretical delta of 6-3/4" ---------CORRECT ANSWER----------------- 6 - 3/ When recording post- tension stressing results, the inspector should note -- -------CORRECT ANSWER-----------------The serial number of the jack and gauge, weather conditions, the name of the general contractor and the name of the equipment operator
