circular prestressing ppt

Thcrc arc 21 bars for each of six columns: A, = 21 X 6 X 0.79 = 100 sq.in., which is sufficient. The amount of reinforcement provided must be sufficient for strength and serviceability including temperature and shrinkage effects. 32, some of the bars are in the top, others in the bottom of the slab, depending on the sign of the tangential moments. The change will be even smaller when the taper is from 14 in. 40 will give good performance not only at the PAGE 27 base but anywhere in the wall. Presentation Transcript. Design is restricted in principle only by material properties and . 0 4 9 0 + 0 . The change in moment is from -27,100 to -22,000 in the Total mom. mom. 24. If the uniformly distributed ring tension due to load in the tank is, say, 300 p.s.i., the combined stress will be: 675 p.s.i. which holds a liquid with a temperature T, = 120 deg. For ring tension, multiply coefficients from Table VI by MR/H2 = 6,700 X 27/202 = 450 lb. The wires or tendons lay outside the concrete core. Modification 2 ACI 350-01 requires that the value of U be increased by using a multiplier called the sanitary coefficient. Fixed end moment omitting surpressure = -0.049 (400 + 125) X 232 = -13,600 ft.lb. Length of this section is 2n X 82.5 = 518 in. Prestressing places the entire tank wall into a state of permanent compression. Such modified design moments have been thoroughly investigated by numerous test loadings of flat slab floors and are generally accepted for use in design. 36, February, 1930, pages 37-39. 10 / ll,bbO 33,750 lb I lb c!2 FIG. H=5 m D=10 m Floor Slab 35 cm Drop Panel d=2.5 m and 50 cm thick. This area is in addition to the regular ring steel. In the examples in the preceding sections, 15 in. 17 Total ring ten. The maximum tension for hinged base is 33,700 lb. 1 l.OOR 31, +0.0614 +0.0539 +0.0451 +0.0352 1 +0.0245 moments, to.0629 10.0578 +0.0518 r0.0452 +0.0381 +0.0566 +0.0532 +0.0494 +0.0451 +0.0404 +0.0437 +0.0416 +0.0393 +0.0368 1 +0.0340 +0.0247 +0.0237 +0.0226 10.0215 +0.0?00 0 0 0 0 0 +0.0175 10.0134 +0.0097 +0.0065 +0.0038 +0.0234 +0.0197 +0.0163 +0.0132 +0.0103 +0.0251 +0.0218 +0.0186 +0.0158 +0.0132 +0.0228 +0.0199 +0.0172 +0.0148 +0.0122 +0.0168 +0.0145 +0.0123 +0.0103 +0.0085 0.80R 0.90R 1 .OOR ~~ +0.718 to.692 +0.663 10.624 10.577 ~~~ to.824 +0.808 +0.790 10.768 +0.740 ~__~~ +0.917 to.909 to.900 10.891 10.880 +l.OOO 11.000 fl.000 +l.OOO +l.OOO to.212 10.185 10.157 +0.129 to.099 +0.314 +0.290 10.263 10.240 to.714 +0.405 10.384 10.363 +0.340 +0.320 +0.486 +0.469 to.451 to.433 to.414 .Wf -0.0121 -0.0153 -0.0175 -0.0184 -0.0184 +0.0061 +0.0020 -0.0014 -0.0042 -0.0062 Table XV Moments in circular slab with center support Moment per ft., M, applied at edge Hinged edge Mom. 44 is built by means of a vertical board or bulkhead which must be notched for passage of the ring bars. Looks like youve clipped this slide to already. **A thcorccically correct cocticicnt of 0.0169 was determined in the same way as those in Table XIII, but the 11 per cent reduction is considered permissible since the cdgc is not fully fixed. per ft., and for moments, multiply coefficients from Table XI by M = 6,700 ft.lb. Tangential moment at a fixed edge equals radial moment times Poissons ratio = 11,ooO X 0.2 = 2,200 ft.lb. A Contribution to the Calculation of Circular Tanks in Reinforced Concrete by H. Carpenter, Cc?nrrctc lrnd Cvzstructio& Engierring, Vol. The radius of the smallest ring bar may be 1 ft. per ft. mom.. per ft. /I - 6,700 j - 8,800 j - 7,700 1 - 5,700) - 1,900 1 + 700 / + 2,300 / + 2,700 1 + 2.100 / + 500 / - 1,800 PAGE 23 Maximum steel area will be required at edge of drop panel. The concrete should be deposited at frequent intervals around the periphery of the tank. The SlideShare family just got bigger. Contrary to popular belief, "linear prestressing" refers to any sort of prestressing in which the cables are straight or curved but not looped in circles around a circular structure. is considered allowable, the IO-in. The condition to be investigated in this section is illustrated in Fig. The effect of a radial displacement at the base is discussed in Section 8. 19. *(1)(5)(10) t/m M=Coef. Now customize the name of a clipboard to store your clips. Use twentyone l-in. Above 0.6H reduce ring steel in proportion to the ring tension values in Schedule D. Check stress in concrete by Equation 1: f = 0.0003 x 30 x 10s X 1.92 + 27,300 = 273 p.s.i. The total over-all length of positive reinforcement is 22.4 - 8.1 + 2 X ;8 = 16.0 ft. Moment at the base is changed from -9,300 ft.lb. Calculate the ring tension caused by applied moment at the top of the wall using Table A-10 3. . Fig. Coefficient from Table XIII is x X (-0.1433 0.1089) = -0.126. per ft. (for moment at edge). Free access to premium services like Tuneln, Mubi and more. per ft of width \ I 4 E a r s B4 a r s Total : lG-%+~ 18'-3" FIG. At the interior column in Fig. Determine the proper length of bars by sketching the moment curve as described in Section 12. = 24,100 lb., occurs at Point 0.7H. per ft. Point 1 0.15R 1 0.2R 1 0.25R When edge is fixed: 1.007 pR2 = 1.007 X 650 X 272 = 478,000 lb. 6 1 1 1 0.711 ~__- 0.811 ( 0.911 4.0 + 0.26 + 0.04, - 0.28 i 0.76 6.0 i+ 0.22 + 0.07 - 0.08 1- 0.64 / *Whenthastable is used for moment applied at the top, while the top IS hinged, O.OH is the bottom of the wall and 1.011 IS the top. The value of c is 4.5 ft., but RI is as yet unknown. The wires or the tendons lay outside the concrete centre. The excess amount of ring tension is shown cross-hatched in Fig. 30. TU fy fs 50 150ton Tu 3.0 50 103 As f y 0.9 4200 39.7 cm 2 / m 19.8 cm 2 / m use 1016 mm at each side provided 20 cm 2 / m Example 1 Bottom edge Sliding Vertical Reinforcement Minimum ratio of vertical reinforcement ACI section (14.3) is taken 0.0012 for deformed bar 16 mm in diameter or less. The maximum steel area is 14.3 = 0.95 sq.in. 4. Length of this section is 2~ X 64.5 = 405 in. has been chosen in this example as a reasonable value. PRESTRESSED CONCRETE STRUCTURES . in artificial stone and concrete arches. Specifications should be explicit in demanding the best possible kind of curing that can be obtained at reasonable cost with the facilities available at the job site. 3 and 6 is between fixed and hinged, but probably closer to hinged. mom. tends to rotate the fixed joint as shown in Fig. Any significant cracking in a liquid containing tank is unacceptable. per ft. In this example, the same data as in Section 12 are used. Section 10. 13 with Fig. As computed in the example, a temperature differential of 75 deg. thickness estimated is ample. Under such circumstances the pressure on the tank wall is a combination of the pressure due to the weight of the liquid plus a uniformly distributed loading due to the vapor pressure. co~ret~ 1.35 for h < 16 in (40cm). 40 top of the footing is given a trowel finish and then covered with mastic. per ft. CIRCULAR CONCRETE TANKS WITHOUT PRESTRESSING Section 2.2, April, 1927, pages 237-241. The numbers of systems are available which are patented for the linear prestressing and with modifications to circular prestressing also. perodua total protect contact number; cybex solution b2-fix. Design of Cylindrical Concrete Tanks by Lavcrnc Lccpcr, Civil Enginrrring, Vol. between the inside liquid and the outside air. But surpressure acts on both top and bottom and creates moments in slabs and walls. 2 1 1 ( 0.3/f , 0.411 (0.511 0 . The load on a center column supporting a slab with radius RI and having fixed edge equals: Coef. Use 18-in. The column load is determined by multiplying coefficients taken from Table XVII by PRJ. Edge of column capital - 2 Bars u 4 Bars - 4 Ears Total: IO Bars FIG. Design data for rectangular distribution of pressure may be useful also for design of tanks in which the liquid surface may rise considerably above the top of the wall, as may accidentally happen in tanks built underground. Maximum are,t is required AI ZJ near the center and equals ri, = ~- = 8.9 = 0.73 1.44 x 8.5 sq.in. If desired, some of the bars in Fig. Maximum positive radial moment at O.6R = 8,500 X 2a X 0.6 X 23 = 736,000 ft.lb. Distribution Moment Final Moment 3.37 6.37 9.74 -15.49 5.75 -9.74 3.37 t.m/m 15.49 t.m/m Tank Cylindrical Wall Ring Tension Force in Wall From Table A-1 T=Coef. This rectifies several deficiencies of concrete. round bars spaced 4% in. Whatever material is used, it should be resistant to attack by the liquid stored and must not be ruptured by the small movements that may occur in the joint. I 0.111 Point I / 0.28 0.3H +19,400) ~23.800) / 0.4H / = 21,100 + 33,700 203.4 = 269 p.s.i. per ft. No surpressure on the liquid is considered in computing this moment and, therefore, it must also be disregarded in the design of the wall. 0.4H I 1 $#0.59~+0.234+7,900 +11,600 -1,200+ -0.3440.05100+14,900 + 0.441 + 2,600+17,000 1.21 + + +17,400 X141+ 6.YltlO.28 0.504 7,000 ++ +13.800 +15,100 0.514 + +21,7000.447 +10,200 +27,600 13.080.301+24,100 + + 11.411 0.112 + 3,800 The rotation of the base and the consequent distribution of moment reveal a significant fact. The relative stiffness factors are 0.86 for the wall and 0.14 for the slab (JCC Section 9). By comparing the ring tension curve in Fig. 14. The general procedure in this section is the same as in Section 11. 26(a), and the final moments in Fig. per ft. Multipliers of T al c o e f f i c i e n t s .I from Table XI I I = 824 lb. Use of quality concrete placed using proper construction procedures. 0 The actual condition of restraint at a wall footing as in Figs. Maximum area of ring steel is J A = Tmax. F. gives a stress of 375 p.s.i. Rqort a W,mrRctaining Cmcntr Structurrr, Institution of Structural Engineers, London, 1934, 8 pages. * equals -7,800 ft.lb. 7 9 0 + 0 . ACIR Guide to Design and Construction . 44 In contrast to the joint discussed, a horizontal joint can be made highly resistant to tensile forces. 8. Load on area within the section is 650 X P X 6.882 = 96,000 lb. (see Section 12). *M = Coef. due to water Table A-1 T force due to water pressure B. per ft. Completely revised to reflect the new ACI Building Code and International Building Code, IBC , this popular text offers a unique approach to examining the design of prestressed concrete members in a logical, step-by-step trial and adjustment procedure. Prestressed concrete pipes and tanksCircular prestressing When the prestressed members are curved, in the direction of prestressing, the prestressing is called circular prestressing. 3,500 j+ 3,100 / Distribution factors 2,900 = 28 p.s.i. *HR= Coef. In other words, the shear of V = 2,ooO lb. Source of Prestressing Force Hydraulic Prestressing Electrical Prestressing Mechanical Prestressing 28 . 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