Anchor Chair

------------- - . PAGE 63 , SAUDI TOYO - K. S. A +955-4-3955188 68/29/1998 13:60 steel t V)<1't\ee vl na 2 'Y!l - , Part VII Anchor Bolt Chairs ., When anchor bolts are required at supports for a r '" least radius of gyration, in. shell, chairs are necessary 10 distribute the load to the shell. Small tubular columns (less than 4 ft in R = nominal shell radius. in_. either to inside or diameter) may be an exception if the base plate is centerline of plate (r.ldius normal to cone adequate to take the bending. Otherwise, chairs at bottom end for conical shells) are always needed to minimize secondary bending S '" stress at point, ksi in the shell. For flat-bottomed tanks, choose a bolt circle to r = shell or column thickness. in. just barely clear the bottom without notching it. For other structures, follow the minimum clearances w = weld size (leg dimension), in_ shown in Fig. lOa. W ::: total load on weld, kips per lin. in. of weld Notation WH = horizontal load. kips per lin in. of weld a = top-plate width, in.. along shell Wv = vertical load, kips per lin in. of weld b = top·plate length, in .• in radial direction o = cone angle. degrees, measured from axis of c = top·plate thickness, in. cone Z == reduction for factor d '" anchor-bolt diameter. in. Top Plate e := anchor·bolt eccentricity. in. Critical stress in the top plate occurs between the hole and the free edge of the plate. For convenience emin == 0.8860' + 0.572, based on a heavy hex nut we can consider this portion of the top p late as a clearing shell by 1/2 in. See Table 5. beam with partially fixed ends, with a portion of f = distance. in., from outside of top plate to the total anchor bolt load distributed along part edge of hole of the span. See Fig. 11. f min = d /2 + 1/8 s = --; (O.375g - O.22d) (44) fe 9 = distance. in .. between vertical plates (pre· ferred 9 rz:: d + 1) or h = chair height. in. c '" [L. (0.3759 _ O.22d)] 1/2 (45) Sf i =vertical-plate thickness, in. k = vertical-plate width, in. (average width for Top plate may project radially beyond vertical tap·ered plates) plates as in Fig. 100', but no more than 1/2". L '" column length, in. • Chair Height m = bottom or base plate thickness, in. Chair must be high enough to distribute anchor bolt load to shell or column without overstressing _ P ::a design load, kips, or maximum allowable it. If the anchor bolt were in line with the shell anchor-bolt load or 1.5 times actual bolt the problem would be simple - the difficulty lies load, whichever is less in the bending caused by eccentricity of the 47 ... -._-----.---

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Anchor chair calc

Transcript of Anchor Chair

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PAGE 63 , SAUDI TOYO - K. S. A

+955-4-395518868/29/1998 13:60

steel .pla.t~ t V)
~~--_._- - ._

PAGE 64A SAUDI TOYO - K. S. A+955-4-3955188

.f

(bl Vertical Column or Skirt

(aJ Typical.Plan & Outside Views

(c) Flat Bottom Tank (dl Conical Skirt

Fig. 10. Anchor-bolt Chairs_

Fig. 11. Assumed top-plate beam.

anchor bolt with respect to the shell. Except for the case where a continuous ring is used at the top of chairs, maximum stress occurs in the vertical direction and is a combination of bending plus direct stress. Formulas which follow are approximations, based on the work of Bijlaard.

s - Pe [1.32 Z .031 ] (461-7 1 43ah1 +-=

-'-R-l- + (411h 2l:J33 y Rl

48

Table 4. Top-Plate Dimensions B...d on ."ellor.bolt .tr.nes up 10 12 ... lor l-l/2-;".-
PAGE 05.3:00 +966-a-3955188 A SAUDI TOYO - K. S. A

Note that the base plate or boltom is also subjected to this same horizontal force, except inward instead of outward. This is true even if a continuous ring is not used around the top of the cha irs - but it should never cause any very high stresses in the base, so we do not normally check it. However, it is a good thing to keep in mind in case you have a very light b