ENSC1002StaticsLectureNotes.pdf

Structureobject as either statically indeterminate or

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structure/object as either statically indeterminate or statically determinate. i.e. statically determine CAN be solved using equations of equilibrium alone statically indeterminate CANNOT be solved using equations of equilibrium alone How do we tell if a structure is determinate or indeterminate.. A rigid body (single object) is indeterminate if two (or more) non-collinear unknowns forces in a particular direction + one (or more) moment reactions
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Week 9 Lecture 2 6 more than two unknown forces in a particular direction two collinear unknowns in a particular direction.
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Week 9 Lecture 2 7 Stability For an object or structure to be stable, it must be properly held (or constrained) at supports. An object will be unstable if it has no reaction force in a particular direction if all reaction forces are concurrent
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Week 9 Lecture 2 8 A bike is an example of a structure that is intentionally unstable (i.e. partially constrained).. the bike above could be idealised as
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Week 9 Lecture 2 9 Examples Are the following structures determinate or indeterminate?
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Week 9 Lecture 2 10 are the following structures stable or unstable??
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Week 9 Lecture 2 11 Further equilibrium example
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Week 9 Lecture 2 12
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Week 10 Lecture 1 1 Summary We have now gained experience in; idealising objects or structures by considering the types of forces generated at the support points drawing FBDs solving for unknown reaction forces for objects or structures that are statically determinate We can also identify if an object/structure is statically determinate, statically indeterminate or unstable (i.e. a mechanism). These are very important skills as an engineer, as we often need to assess the stability of objects and also make sure the support conditions are strong enough to hold the structure in place. For example, now that we know the forces at the base of the traffic lights, we could design a suitable foundation… But this is only part of the problem. We must also be able to determine if the members making up the structure are strong enough to carry the loads. For example, how strong does member AB need to be??
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Week 10 Lecture 1 2 To determine if a member is strong enough, we must be able to determine the forces within the member. So far we have considered only "external forces". Now we will consider "internal forces" (i.e. forces within the members of a structure). We will begin by analysing a particular type of structure known as a truss. Truss All structures are made up of "members". A truss is a special type of structure because it is made up of members that only carry "axial" loads. Axial loads can either be "tension" or "compression" loads. Note, the axial force always acts in the same direction ( ) as the orientation of the member.
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