Study in construction higher educational institutions of such disciplines as, for example, resistance of materials or construction mechanics demand definition in seals of reactions of support. Without having calculated these reactions, it is impossible to calculate tasks on durability, stability and rigidity, so not to master material which forms a basis for design of buildings and constructions.
Instruction
1. Before the solution of a task write out a task condition. Draw the set scheme of a frame, beam, farm, arch in strictly chosen scale. Specify all sizes and the operating loadings on your scheme. If numerical values are given, then too surely sign them. Draw the scheme by means of drawing tools, considering all set parameters. Designate all characteristic points by letters, and numerical values of the sizes, loadings and basic reactions surely designate with their values.
2. Start definition of reactions in seal. It can be done, having worked out the equation of the moments concerning any point in the set scheme. As a rule, the point is chosen so that the problem was solved by the easiest way. In the chosen point reactions which are unknown can be enclosed, i.e. temporarily consider them equal to zero.
3. Choose the direction by drawing up the equation of the moments. In most cases in construction mechanics take for the positive direction counterclockwise. If as a result reaction turns out negative, then you should not be afraid of it: it means that it has an opposite direction. But you remember that at the further solution of a task that sign which turned out as a result of your calculation is always considered.
4. It is impossible to define reactions in seal in one of parts of the set scheme. Reactions are defined, considering everything that is given in a task initially. Do not use at all such method as symmetry as it does not work in this case.
5. To check whether reactions in seals are correctly calculated it is possible, having worked out the equation of the sum of the moments on an axis of X or Y. At the right decision you have to receive zero. Remember that working out such equations you consider also the distributed loading both power and even those reactions which were unknown. If you do not consider at least one of loadings, then the equation will not be equal to zero and all calculations should be executed anew.