Structural safety analysis of reinforced concrete buildings during construction (fuzzy set)

The reliability associated with the construction of cast-in-place reinforced concrete multi-story buildings is studied. A methodology of reliability assessment of reinforced concrete buildings during construction is proposed. The risk of failure of a building at any stage of construction, measured in terms of the probabilities of failure, as well as the variation of these probabilities with changes in planning, scheduling, field practices, site condition, and/or the experience of construction personnel are estimated using the proposed methodology. Simulation techniques and variance reduction techniques which are appropriate for structural reliability are proposed. The basic theory of fuzzy set and system is presented briefly. Different techniques of load and load effect combination, system reliability modeling, decision theory are reviewed and discussed. The uncertainties in the basic resistance parameters and their variations with time are examined. The uncertainties in the different kinds of construction loads are discussed. It is found that a two-way shear failure mode is the most critical one during the construction of buildings. Bond failure, and flexural failure in tension are unlikely during construction. The effect of increasing the number of shored and reshored floors on the probabilities of failure for reinforced concrete elements is small. Moreover, the risk of failure of falsework is mainly due to design and construction errors and omissions, and accidents. The contribution of the construction operations' safety, which is a function of the experience of construction personnel, site conditions, weather, stage of construction, equipment, etc. , to the probability of failure of the incomplete structure is incorporated by the proposed methodology. However, since most of the parameters defining and affecting the safety of construction operations are measured by linguistic terms, the fuzzy set theory is used to model these parameters, and to estimate the safety of construction operations. The reliability of a five-story reinforced concrete building, which failed during construction in Cocoa Beach, Florida, in March 1981, is examined. The probability of failure of the building is estimated to be in the range of 0. 8413 to 0. 9563. The contribution of punching-shear mode of failure to the probability of the failure of the building is found to be the largest.