Section modulus

When tanks are built having an open top, the wind pressure may cause buckling of the shell. A wind girder of sufficient section modulus is used to stiffen the open top according to... 

Busbars are mounted one below the other, horizontally but in a vertical disposition. The cooling is better and requires less derating. The short-circuit withstand capacity is high due to high sectional modulus but occupies more vertical space. This configuration is also adopted by some manufacturers. 

F = maximum electrodynamic forces acting on each support, in the event of a fault, as calculated above = 514 kgf / = centre distance between two busbar supports = 40 cm M = sectional modulus of each busbar at section x - x... 

To calculate the sectional modulus (or moment of resistance) of the four bus sections in parallel we have multiplied the sectional modulus of one bus by 4. This is a simple method when the busbars of each phase are in the same plane and equally spaced as in Figure 28.33(a) with no additional spacers between them to hold them together. 

But when other configurations are adopted as shown in Figure 28.34, this concept may not hold true. In other configurations, however, the sectional modulus will only rise and reduce the bending stress on the busbars. 

The method adopted to calculate the sectional modulus is therefore simple and on the safe side. However, to calculate the sectional modulus more accurately or to derive it for any other section of the support than considered here reference may be made to a textbook on the strength of materials or a machine handbook. 

Non linal Desig- nation Wall Thick- ness Inside Diam. Weight per Foot Wt. of Water per Ft. of Pipe Sq. Ft. Outside Surface per Ft. Sq. Ft. Inside Surface per Ft. Trans- verse Area in.2 Area of Metal in.2 Moment of Inertia in. " Section Modulus in. Radius of Gyration in. 

It is current practice to select the rotary shoulder connection that provides the balanced bending fatigue resistance for the pin and the box. The pin and the box are equally strong in bending if the cross-section module of the box in its critical zone is 2.5 times greater than the cross-section module of the pin at its critical zone. These critical zones are shown in Figure 4-127. Section modulus ratios from 2.25 to 2.75 are considered to be very good and satisfactory performance has been experienced with ratios from 2.0 to 3.2 [39]. 

The section modulus. Z, of the box should be 2 / times greater than the section modulus, z, of the pin in a drill collar connection. On the right side of the connection are the spots at which the critical area of both the pin (Ap) and box (A ) should be measured for calculating torsional strength. 

From Table 4-71, cross-sectional area body of pipe A = 4.4074 in. and Polar section modulus Z = 8.542 in. ... 

Bending section modulus of Hevi-Wate drill pipe is (4.5) -(2.75) ... 

To maintain BSR of less than 5.5, selection 5-in. heavy-weight drill pipe with unit weight of 49.3 Ib/ft (see Table 4-91) and section modulus of 21.4 in . 

Unit weight of drill pipe corrected for tool joint is 21.34 Ib/ft. Section modulus of this pipe can be calculated to be 5.7 in . 

Rib design An example of how ribbing will provide the necessary equivalent moment of inertia and section modulus will be given. A flat plastic bar of IV2 in. x 3/8 in. thick and 10 in. long, supported at both ends and loaded at the center, was calculated to provide a specified deflection and stress level under a given load. The favorable material thickness of this plastic is 0.150 in. Using... 

Radius of Gyration Moment of Inertia Section Modulus ... 

---