Chapter 3 - Axially loaded members. The following will be discussed in this chapter: Normal stress and normal strain, tension and compression test, poisson’s ratio, shearing strain, allowable stress – factor of safety, statically indeterminate problem. | STRENGTH OF MATERIALS 1 10 2013 TRAN MINH TU - University of Civil Engineering 1 Giai Phong Str. 55 Hai Ba Trung Dist. Hanoi Vietnam Axially loaded CHAPTER members 3 1 10 2013 2 Contents . Introduction Stress and Normal Strain . Tension and Compression Test . Poisson s ratio . Shearing Strain . Allowable Stress Factor of Safety . Statically Indeterminate Problem 1 10 2013 3 . Introduction Suitability of a structure or machine may depend on the deformations in the structure as well as the stresses induced under loading. Statics analyses alone are not sufficient. Considering structures as deformable ones allows us to determinate the member forces and reactions which are statically indeterminate. Determination of the stress distribution within a member also requires the consideration of deformations in the member. Chapter 3 is concerned with the stress and deformation of a structural member under axial loading. Later chapters will deal with torsional and pure bending loads. 1 10 2013 4 . Introduction Prismatic bar Straight structural member with the same cross- section throughout its length Axial force Load directed along the axis of the member Axial force can be tensile or compressive Axially loaded members are structural components subjected only to axial force tension or compression 1 10 2013 5 . Introduction 1 10 2013 6 . Introduction Axial force diagram Using the method of section the internal axial force is obtained from the equilibrium as a function of coordinate z Z 0 N z . Kinematic assumptions Before deformation After deformation 1 10 2013 7 . Normal stress and normal strain Kinematic assumptions 1. The axis of the member remains straight 2. Cross sections which are plane and are perpendicular to the axis before deformation remain plane and remain perpendicular to the axis after deformation. And the cross sections do not rotate about the axis Normal stress Nz z z const A normal stress at any point on the .
