One of the objective of such problems is to find the stress in each component.įor example, you may have a short column made from a steel pipe filled with concrete, as in the figure.
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There are cases when a member under normal stresses is made out of two (or more) materials.
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Members made from two different materials Find: maximum load magnitude that leads to an acceptable stress.Given: load type and distribution, material properties, member shape and dimensions.Evaluating maximum allowable load on a component.Find: the shape and dimensions of the member so that actual cross-sectional area is greater than minimum required.Given: loads magnitude and distribution, material properties.Determining the shape and dimensions of member’s cross-section.Find: what material type or grade will provide a strength (yield or ultimate) greater than required, while considering the selected or specified safety factor.Given: loads magnitude and distribution, member shape and dimensions.Find: actual stress and compare to the design stress alternatively find the safety factor and decide if it is acceptable based on applicable standards.Given: loads magnitude and distribution, material properties, member shape and dimensions.Estimating if a design/construction is safe or not.While the theoretical concepts are the same, the paths to final answers may be different, as required by each approach. When solving problems students may encounter different scenarios. published by ANSI / AISC, such as Specification for Structural Steel Buildings.Standards are continuously evolving reflecting new and improved design philosophies. Safety factors standards were set by structural engineers, based on rigorous estimates and backed by years of experience. The safety factor is chosen by the designer based on experience, judgment AND guidelines/rules from relevant codes and standards, based on several criteria such as risk of injuries, design data accuracy, probability, industry standards, and last but not least, cost.
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Safety factor (or design factor) N, ratio of maximum strength to the intended load.Material properties, Ultimate Tensile Strength or Yield Strength, depending if breakage must be avoided or deformation must be limited.Consider a heavy condensate line that sags beyond an acceptable limit and while it doesn’t break, the flange connections at the end of the lines will develop leaks due to angular movement.ĭesign stress, σ d, is the maximum level of actual/working stress that is considered acceptable from a safety point of view. Members subjected to an excessive stress may fail by breaking, when actual working stress is greater than the ultimate stress, or due to excessive deformation that renders then inoperable. These topics were covered in 1 st year Strength of Materials and are presented here as a brief review.