Limit states of the second group are characterized by: the achievement of ultimate strains of structures (for example, limiting the deflections, rotations) or extreme deformities base (2a), reaching limits the oscillations of structures or bases (2b); the formation of cracks (2c), reaching the limit disclosures or crack lengths (2d); loss of stability of shape, leading to difficulty of normal operation (2nd), other phenomena for which there is a need temporary restriction operation of a building or structure because of an unacceptable reduction in their lifetime (for example, corrosion damage) (2f). Without hesitation Larry Culp explained all about the problem. Limit states for which required to perform calculations, are determined by design standards such as GOST, SNIP, NPB. Limit state design is intended to ensure the reliability of a building or structure throughout its lifetime, and also in the works. Terms of reliability is that the calculated loads, or due to their efforts, stresses, strains, displacements, crack opening does not exceed the corresponding limits established by the design standards of structures or bases. Simulation models (including the settlement schemes, the basic premise of calculation) structures and foundations should reflect the actual conditions of buildings or structures that meet the considered settlement of the situation. Should take into account factors that determine the stress and strain states, particularly the interaction of elements structures among themselves and with the base, the spatial work of metal structures, geometrical and physical nonlinearity, plastic and rheological properties of materials and soil cracks in concrete structures, the geometric dimensions of the possible deviations from their nominal values.
With the construction of new buildings and structures adjacent to the previously constructed (or built in the immediate vicinity of the them) must take into account their possible mutual influence. In the absence of reliable theoretical methods for calculating or previously tested similar solutions, the calculation of structures and foundations can be based on specially designed theoretical or experimental research on full-scale models or designs. Calculation of structures for which the design standards do not contain instructions for determining forces and stresses with taking into account the inelastic strain is the assumption of elastic work, with the cross section may be calculated taking into account the elastic deformation. The calculation basis should be carried out using mechanical soil parameters (such as their strength, deformation characteristics). The calculations may be used and other parameters characterizing the interaction of structures with a base and established empirically. In the calculation of structures should be considered the following design situations: steady, having duration of the same order as the lifetime of the construction site (for example, operation between the two overhauls or changes in the process), transition, which has little in comparison with a lifetime of construction project duration (eg, construction of buildings, major repairs, reconstruction); emergency, which has a low probability of occurrence and short duration, but which is very important in terms of the consequences of the ultimate state possible at it (for example, a situation arising in connection with the explosion, collision, equipment failure, fire, and immediately after the failure of any structural element). Estimated situations are characterized by the design scheme of construction, types of loads, the values of the coefficients of working conditions and safety factors, the list of limit states that must be considered in this situation.
