Seismic safety assessment of buildings with fly-ash concrete

Sustainable concrete construction has encouraged the utilization of industrial wastes [fly ash (FA), silica fume, ground granulated blast furnace slag, metakaolin, and so forth] as a composite cementitious material due to its high pozzolanic activity. Among them, fly-ash concrete is gaining high popularity in the construction industry due to its many benefits to concrete structures, including increased structural performance. To estimate the seismic performance of FA concrete buildings, a probabilistic study was performed to determine its mechanical parameters at various performance limit states. Weibull, normal, log-normal, and gamma distribution probability distribution models were considered for three goodness-of-fit tests: the Kolmogorov–Smirnov (KS), chi-square (CS), and log-likelihood (LK) tests. Among them, the lognormal distribution was found to be the closest distribution describing the variations in the mechanical properties of FA concrete compared with other distributions. It was observed that 20%–40% partial replacement of FA with cement improves the performance of structures with enhanced structural safety at economical cost

Variability of silica fume concrete and its effect on seismic safety of reinforced concrete buildings

Design of structures made using silica fume (SF) concrete to an acceptable level of safety requires the probabilistic evaluation of its mechanical properties. An extensive experimental program was carried out on compressive strength, flexural strength, and tensile splitting strength of SF concrete. Seven concrete mixes with different proportions of SF were designed to produce 490 concrete samples. The probabilistic models to describe the variability of the mechanical properties of SF concrete were proposed. Two-parameter probability models such as Weibull, normal, lognormal, and gamma distribution were considered for the representation of variability. The probability distribution models were selected based on goodness-of-fit tests such as the Kolmogorov-Sminrov (KS), chi-square (CS), and log-likelihood (LK) tests. The results obtained from the models are useful for description of the variability of selected mechanical properties of SF-incorporated concrete. This study proposes the lognormal distribution function as the distribution model that most closely describes the variations of different mechanical properties of SF concrete from a practical point of view. Further, the performance of typically selected buildings using SF concrete was evaluated through fragility curves and reliability indices incorporating the proposed probability distributions and variability of compressive strength property. It was found that 15%-25% of partial replacement of cement with SF may yield better performance of the frames