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Text Book of Machine Design Part 16

Columns and Struts | CONTENTS C H A P T E R 16 Columns and Struts 1. Introduction. 2. Failure of a Column or Strut. 3. Types of End Conditions of Columns. 4. Euler s Column Theory. 5. Assumptions in Euler s Column Theory. 6. Euler s Formula. 7. Slenderness Ratio. 8. Limitations of Euler s Formula. 9. Equivalent Length of a Column. 10. Rankine s Formula for Columns. 11. Johnson s Formula for Columns. 12. Long Columns Subjected to Eccentric Loading. 13. Design of Piston Rod. 14. Design of Push Rods. 15. Design of Connecting Rod. 16. Forces Acting on a Connecting Rod. 16.1 Introduction A machine part subjected to an axial compressive force is called a strut. A strut may be horizontal inclined or even vertical. But a vertical strut is known as a column pillar or stanchion. The machine members that must be investigated for column action are piston rods valve push rods connecting rods screw jack side links of toggle jack etc. In this chapter we shall discuss the design of piston rods valve push rods and connecting rods. Note The design of screw jack and toggle jack is discussed in the next chapter on Power screws . 16.2 Failure of a Column or Strut It has been observed that when a column or a strut is subjected to a compressive load and the load is gradually increased a stage will reach when the column will be subjected to ultimate load. Beyond this the column will fail by crushing and the load will be known as crushing load. 600 CONTENTS It has also been experienced that sometimes a compression member does not fail entirely by crushing but also by bending i.e. buckling. This happens in the case of long columns. It has also been observed that all the short columns fail due to their crushing. But if a long column is subjected to a compressive load it is subjected to a compressive stress. If the load is gradually increased the column will reach a stage when it will start buckling. The load at which the column tends to have lateral displacement or tends to buckle is called Columns and Struts .