PRESTRESSED CONCRETE CONTAINMENT MODEL
PRESTRESSED CONCRETE CONTAINMENT MODELBy Sami H. Rizkalla l 1 A. M. ASeE, Sidney H. Simmonds, 2and James G. MacGregor/ Members, ASeEAeSTRACT: The construction and testing of a model of a prestressed concretecontainment structure is described. The test structure consisted of a reinforcedconcrete base, cylindrical wall, ring beam and dome built of prestressed concrete with construction details patterned after the Canadian CANDU reactorcontainment. The overall height above the base was 12 ft-6 in. (3,810 mm), andthe outer diameter was 10 ft-6 in. (3,200 mm). Internal pressure was obtainedusing water, and leakage was prevented by using a flexible plastic liner. Measurements made during the test included internal pressure, steel and concretestrains, crack widths and spacing, and curvatures at the base of the cylindricalwall. The test structure began to exhibit cracking at a pressure of 30 psi (0.28MPa), and yielding of the reinforcement at approximately 110 psi (0.76 MPa).The structure displayed considerable ductility before failing at internal pressureof 159 psi (1.10 MPa) by rupture of three horizontal tendons at midheight ofthe wall. Outward deflection of the walls damaged the anchorage zones of someof the tendons. The cracking behavior and failure mechanism are described.INTRODUCTIONContainment structures are built around the reactors and the primarycontainments in nuclear generating plants to enclose heat exchanges,and to prevent the release of any possible radioactive materials into theatmosphere. These structures frequently are constructed from prestressed concrete.The design specification for the prototype secondary containmentstructure required that the concrete on the interior face remain free oftensile stresses under normal operating conditions, pressure test loading, a certain specified design basis accident pressure, and earthquakeconditions. Consequently, the serviceability requirements under designbasis accident pressure constitute one of the governing limit states ofthe structure design. The prototype structure did not have a steel liner.Hypothesizing that internal pressure may increase without limit, a series of additional limit states can be identified. During a continuous increase of the internal pressure, areas of the interior face will be subjectedto tension followed by cracking of concrete and yielding of the reinforcement. With further increases of the pressure, the cracks would penetrate through the concrete, followed, after further load, by plastic deformation of the reinforcement and prestressing tendons'a{1d would finallyrupture, an event which constitutes collapse of the structure.To evaluate the behavior of such structures at these various limit states,a comprehensive analytical and experimental study was undertaken atthe University of Alberta, Edmonton, Canada. The analytical techniquesIAssoc. Prof. of Civ. Engrg., Univ. of Manitoba, Winnipeg, Manitoba.2prof. of Civ. Engrg., Univ. of Alberta, Edmonton, Alberta.lProf. of Civ. Engrg., Univ. of Alberta, Edmonton, Alberta.Note.-Discussion open until September 1, 1984. To extend the closing dateone month, a written request must be filed with the ASCE Manager of Technicaland Professional Publications. The manuscript for this paper was submitted forreview and possible publication on February 25, 1983. This paper is part of theJournal of Structural Engineering, Vol. 110, No.4, April, 1984. A5CE, 155N0733-9445/84/0004-0730/ 01.00. Paper No. 18761 .730
from the vertical wall. A 24-in. x 3D-in. (610-mm x 762-mm) tunnel alonga diam provided access through the base to the interior of the structurethrough a 30-in. square hatch which was sealed by an aluminum door.The thickness of the wall and dome were selected on the basis of construction of the test structure and the desired sequence of behavior rather(a)(b)(e)FIG. 4.-Relnforcement Details Prior to Placing Concrete: (a) Dome Reinforcement; (b) Base Reinforcement; (e) Wall Reinforcement733
than as scaled values of the prototype. The dome thickness selected was4 in. (100 mm) which was the minimum thickness that could be used toaccomodate two l.O-in. (25-mm) ducts for post-tensioning in orthogonaldirections, and two layers of reinforcing in each face, and to maintain1/2-in. (13-mm) cover. For a similar reason, the wall thickness was selected as 5 in. (127 mm). The amounts of both horizontal and verticalprestressing were selected to obtain the desired cracking sequence.The circumferential steel in the wall was provided by #3 bars (10 mmdiam) spaced at 3 in. (76 mm) on centers with a yield strength of 50 ksi(345 MPa). Nominal 6-mm diam deformed bars conforming to Swedishspecification with a yield paint of 70 ksi (482 MPa) were used for boththe vertical wall reinforcing and dome reinforcing. Details of the reinforcing and prestressing tendons for base-wall connection, wall, and domereinforcing are given in Fig. 3(a- c). Fig. 4(a - c) shows the base, wall, anddome reinforcing prior to placing of concrete. Further details are provided in Ref. 3.Normal sand and gravel concrete with a maximum aggregate size of3/8 in. (10 mm) and a compressive strength of 4,500 psi (30 MPa) wasspecified for the model. Liquid plasticizer Melment LlO was specified toimprove workability. However. due to delays in placing the concrete inthe wall the life of the plasticizer was exceeded during casting of thewall, resulting in poor compaction of the concrete in the upper portionof the wall. This required chopping out the upper layer of the poorlycompacted concrete. The remainder of the wall section was placed byshotereting. The properties of the two types of concrete were accountedfor in the analysis of the test structure and did not significantly influencethe behavior or the mode of failure .POST-TENSIONING SEQUENCEThe vertical wall tendons were post-tensioned first. Each tendon wasanchored at the base where a load cell was located and tensioned fromthe top. Four jacks were used so that four tendons located at 90 intervals around the perimeter could be pulled simultaneously to full tensionof 14 kips (62 kN).The horizontal wall tendons extended over only one-hall of the circumference to reduce friction, The tendons were anchored in verticalbuttresses shown in Figs. 1 and 3(c). Adjacent pairs of tendons werestaggered by 90 resulting in the four buttresses to accommodate theanchorages being located symmetrically around the wall. The two horizontal tendons at a given elevation were tensioned simultaneously fromeach end using four jacks to half the design tension in a sequence tomaintain as close to a uniform stress distribution as possible. The samesequence was then used to retension all tendons to full design tension.The dome tendons were tensioned in pairs using four jacks, one ateach end, with a load cell at one end only. Starting with the tendoncrossing the crown in one direction and progressing symmetrically toparallel tendons all of the tendons in one direction were stressed to halfthe design force, The sequence was repeated in the orthogonal direction.The same procedure was then used to pull the tendons to final values.It was noted that with both the horizontal wall tendons and the dome734
tendons some had to be retensioned to achieve final values within theacceptable tolerance, After all tendons had been fully stressed, they weregrouted with cement grout using a pressure grouting system,INSTRUMENTATIONExtensive measurements were made during the various tests of thecontainment structure. Measured quantities included internal pressure,deflections, steel and concrete strains, meridian rotations, crack widthsand crack locations.A total of 24 deflection readings were taken electronically along themeridian referred to as line 1. Line 1 extended from the base of the cylinder to the top of the dome and was located on the south face midwaybetween buttresses, and along a circumferential line 2,25 ft (686 mm)from the base in the south quadrant,Strains were measured using electric resistance gages along and acrossline 1 located, as previously mentioned, on line 2 located on the meridian diametrically opposite line 1, and on line 3 located along the southwest buttress. In addition, average strains were measured manually alongand across line 2 using Demec mechanical extensometers. A total of 207electric resistance strain gages located on steel reinforcing, 38 electricalresistance gages on concrete faces, and 74 Dernec gages were read.Along a vertical line located 6 in, (150 mm) east of line 1 and startingat the base, a series of five 1/2 in, diam rods at 5 in, spacing protrudedfrom the wall, Dial gages graduated in 0,0001 in, clivisions were mountedon these rods in such a manner that it was possible to compute the anglechanges at each of the rods and the elongation of the midplane of thewall. From the angle changes the average curvatures and horizontal deflection of the wall could be calculated,All the cr cks observed on the west quadrant were marked with feltpens. Crack widths were measured across and along two vertical andtwo horizontal lines on both the north and west faces using a 40 powermicroscope, Readings were recorded to the nearest 0,001 in, (0,025 mm),In general, strain and deflection readings were taken electronically atintervals of internal pressure of 5 psi and manual readings of crack widthsand strain at 10 psi, although in later stages readings were taken at smallerintervals, the interval being controlled by strain measurements. Above140 psi (0,97 MPa) only electronic readings were taken,The internal pressure, deflections and electric resistance strain gageswere read and recorded into data files automatically using the Nova 210/E digital computer and data acquisition system. Manual readings weretyped into computer files immediately after each test so that data reduction and plotting of results could be completed quickly using computer routines.TESTINGWater was the agent used to develop the internal pressure in the teststructure, The pressure was obtained using a hand-operated pump topressures of 140 psi (0,97 MPa) above which a truck mounted, highcapacity, high-pressure pump was used, To prevent the water from leak735
ing through the containment wall after cracking and still provide theopportunity of viewing the interior concrete face after selected loadingsequences, a removable liner made from a heavy plastic material wasfitted to the inside surface. A series of five test runs below the initialcracking pressure were made to test the effectiveness of the liner andto evaluate the response of the instrumentation and data reduction routines. As a result of these runs the seal around the hatch was replacedand certain gages were replaced and rewired.The first major loading sequence, referred to as load F, was terminatedat an internal pressure of 80 psi (0.55 MPa) due to the difficulty of maintaining pressure because water was leaking through the cracks in thewalls. After draining the tank and removing the liner it was found thatseveral seams in the liner had failed. A new liner was fabricated thatincorporated several modifications learned from experiences with the firstliner. Using this liner the final load test, referred to as load G, was takento rupture of the structure at a pressure of 159 psi (1.10 MPa). No leakage of the second liner was observed until the test structure failed.OVERALL BEHAVIOR OF TeST STRUCTUREThe first crack developed at a pressure of 30 psi (0.2 MPa) on the inside face of the dome. The first visible signs of meridional and circumferential cracking in the cylindrical wall occurred at 40 psi (0.28 MPa).With further loading these cracks became wider and new cracks developed. Fig. 5 shows the crack pattern on the west face of the wall at apressure just over 130 psi (0.90 MPa) at which time the crack patternwas essentially fully developed. Cracks also appeared at 40 psi in theouter surface of the dome in directions essentially parallel and perpendicular to the meridians except in the region extending approximately 4It (1,220 mm) from the outer edge of the ring beam in which there wereno visible cracks even at the end of the test. The widths of cracks at theFIG. 5.-Crack Pallern and Bulging ofWall at 130 psi (0.90 MPajFIG. 6.-Crack Pallern In Dome at 130psi (0.90 MPaj736
r """, dOomr 0 0-.-131\""."15.,.,.a-. . 225 ".0. .15.iI30 :;Oefleclion (inches)FIG. 7.-Pressure versus Deflectiontop of the dome increased rapidly near the end of loading, being about1/10 in. (2.5 mm) at 130 psi (0.90 MPa), and 3/8 in. (10 mm) at 140 psi(0.97 MPa), with accompanying spalling of adjacent concrete. The crackpattern for the dome at 130 psi (0.90 MPa) is shown in Fig. 6.Outward bulging of the cylindrical walls was noticeable at pressuresabove 80 psi (0.56 MPa) and increased markedly at approximately 110psi (0.76 MPa) . The buttresses also bulged outward but less noticeably(Fig. 5).This marked increase in deformation at approximately 110 psi (0.76MPa) is associated with the beginning of widespread yielding of the reinforcement. The degree of ductility inherent in the structure is evidentfrom Fig. 7 in which the outward deflection of the wall at midheight(channel 225) and the upward deflection near the crown of the dome(channel 237) are shown. The measured deflections at these points immediately prior to the apparent drop in load associated with failure are2.5 in. (64 mm) and 3.0 in. (76 mm), respectively. The break in the loaddeflection curves corresponding to a drop in load from 148 psi (1.02 MPa)to 135 psi (0.93 MPa) and subsequent reloading indicates the amount ofdeflection occurring after the first day of load test G. The pressure wasintentionally reduced to 137 psi when leaving the structure overnight.When loading was resumed after an interval of 14 hr, the pressure haddropped only 2 psi (0.01 MPa). The gap between the two points afterreloading to the previous pressure is an indication of the creep that occurred
PRESTRESSED CONCRETE CONTAINMENT MODEL By Sami H. Rizkallal 1 A. M. ASeE, Sidney H. Simmonds,2 and James G. MacGregor/ Members, ASeE AeSTRACT: The construction and testing of a model of a prestressed concrete containment structure is described. The test structure consisted of a reinforced
Lecture 24 – Prestressed Concrete Prestressed concrete refers to concrete that has applied stresses induced into the member. Typically, wires or “tendons” are stretched and then blocked at the ends creating compressive stresses throughout the member’s entire cross-section. Most Prestressed concrete is precast in a plant.
DIRECT-PLUMBED Containment Tanks Models 2478SQ-NA-DP 1100Lb/150Gal Containment Tank 3072-NA-DP 1500Lb/200Gal Containment Tank 4280-NA-DP 2650Lb/353Gal Containment Tank. About this manual Read this manual for the following information about inside Direct-Plumbed containment tanks:
Introduction to Prestressed Concrete 1 / 7 In prestressed concrete, compressive stresses are applied to the concrete prior to loading. Under service loads, the entire cross section is essentially in compression, which takes advantage of concrete’s considerable compressive
prestressed concrete members, the bonding action between the prestressing element and the concrete is a result of friction as well as adhesion and mechanical resistance. In the fabrication of a pre-tensioned prestressed concrete member the prestressing strand is first tensioned to the desired stress level. Concrete is then cast about the strand and
Single Storage Tank Containment Wall Height Calculation 61 . 3. Example Multiple Storage Tank Containment Wall Height. Calculations 63 . 4. Multiple Storage Tank Containment Wall Height Calculations 64 . D. Bulk Facility Containment Construction Criteria 66 . 1. Outline of General Specifications for cast concrete secondary. containment systems .
Precast/Prestressed Concrete Institute, Design Handbook-Precast and Prestressed Concrete: Code of Standard Practice for Precast/Prestressed Concrete (PCI MNL-120) Structural Material Specifications Concrete Foundations (Pile Caps and Grade Beams): 6,000 p
As prestressed concrete became widely produced and adopted, a second concept was formulated, commonly known as the ultimate strength theory. Under that concept, prestressed concrete is treated as a combination of h\Ph strength con crete and high strength steel, with concrete to carry the compression
transactions: (i) the exchange of the APX share for EPEX spot shares, which were then contributed by the Issuer to HGRT; (ii) the sale of 6.2% stake in HGRT to RTE and (iii) the sale of 1% to APG. The final result is that the Issuer has a participation in HGRT of 19%. For information regarding transactions (i) and (ii) please refer to the press release dated 28 August 2015 (in the note 4 pp .
