Why no stresses develop in a determinate structure due to lack of fit or thermal changes?
Answers
Answered by
3
Lack of fit is an occurence in trusses in which there is a difference between the length of a member and the distance between the nodes it is supposed to fit.
This happens because the connecting member is either too long or too short as compared to the distance between corresponding nodes.
It must also be noted here that lack of fit occurs only in indeterminate trusses because in determinate trusses the variation in member length automatically adjusts the spacing between the nodes, hence, lack of fit cannot occur.
A lack of fit may be unintentionally introduced in a truss due to fabrication errors or it may be deliberately introduced as a part of the design by the engineer.
In cases of lack of fit, the member is either forcibly lengthened or forcibly shortened to fit the truss depending on whether it is too short or too long respectively. This causes the various members meeting at these joints to develop stresses of opposite nature. This prestress occurring due to lack of fit may be used advantageously in design of truss.
The members that develop tension due to loading may be introduced with a compressive prestress and the members that develop compression may be introduced with a tensile prestress. This effectively increases the stress range over which a member may be loaded and the maximum load carrying capacity of the truss. It also increases the factor of safety available at a particular load. Such a design may be developed using lack of fit case.
This happens because the connecting member is either too long or too short as compared to the distance between corresponding nodes.
It must also be noted here that lack of fit occurs only in indeterminate trusses because in determinate trusses the variation in member length automatically adjusts the spacing between the nodes, hence, lack of fit cannot occur.
A lack of fit may be unintentionally introduced in a truss due to fabrication errors or it may be deliberately introduced as a part of the design by the engineer.
In cases of lack of fit, the member is either forcibly lengthened or forcibly shortened to fit the truss depending on whether it is too short or too long respectively. This causes the various members meeting at these joints to develop stresses of opposite nature. This prestress occurring due to lack of fit may be used advantageously in design of truss.
The members that develop tension due to loading may be introduced with a compressive prestress and the members that develop compression may be introduced with a tensile prestress. This effectively increases the stress range over which a member may be loaded and the maximum load carrying capacity of the truss. It also increases the factor of safety available at a particular load. Such a design may be developed using lack of fit case.
Similar questions