04/13/2016

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Wooden Structures The calculation and design elements of wooden structures and buildings. Until recently, the calculation was made of wooden structures on the allowable stress. Under this method, the calculated stress in a wooden element of operating loads compared with the permitted, the latter is obtained by dividing the tensile strength on the safety factor. In this case the tensile strength was taken on the basis of routine laboratory tests on small wood samples. Influence of the duration of the load of wood defects and other factors on the strength of the wooden structures were estimated to be the safety factor, which had different meanings for the lax, compressed and curved wooden elements. This calculation method gives an indication of the wooden structures at the operational load, but did not give a correct idea of the wooden structures in the state close to destruction. The source of the method of allowable stress of a linear relationship between stress and strain are not applicable in practice for many materials, especially wood, even at low voltages. Ignoring the plastic properties of materials, lack of consideration of the actual conditions of the structure under load, the method of calculation of allowable stress, do not give a correct idea of the true margin of safety. As a result of extensive research carried out by Soviet scientists had solved the problem of calculating the wooden structures in engineering limit states. This new method calculation takes into account the effect of various circumstances on the strength of the wooden structure. In the method of limit analysis, in contrast to the method of allowable stress, safety factor is divided into a number of individual coefficients, which take into account the probable change in the load (overload factor n), a possible change in material strength (quality factor k) and the...