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This paper presents the closing step of a synthesis process aiming at deriving, from a previously developed more complex model, a simple design formula to evaluate the shear strength contribution provided by a system of Near Surface Mounted (NSM) Fiber Reinforced Polymer (FRP) strips to a Reinforced Concrete (RC) beam. The self-contained and ready-to-implement set of analytical equations and logical operations is presented along with the main underlying physical-mechanical principles and assumptions. The formulation proposed is appraised against some of the most recent experimental results and its predictions are also compared with those obtained by the two previous and more sophisticated versions of the same modeling strategy. Monte Carlo simulations are carried out in order to appraise the sensitivity of the NSM shear strength contribution prediction to the value assumed by the input parameters. © 2013 Elsevier Ltd. All rights reserved

A modified real-coded genetic algorithm to identify the parameters of large structural systems subject to the dynamic loads is presented in this article. The proposed algorithm utilizes several subpopulations and a migration operator with a ring topology is periodically performed to allow the interaction between them. For each subpopulation, a specialized medley of recent genetic operators (crossover and mutation) has been adopted and is briefly discussed. The final algorithm includes a novel operator based on the auto-adaptive asexual reproduction of the best individual in the current subpopulation. This latter is introduced to avoid a long stagnation at the start of the evolutionary process due to insufficient exploration as well as to attempt an improved local exploration around the current best solution at the end of the search. Moreover, a search space reduction technique is performed to improve, both convergence speed and final accuracy, allowing a genetic-based search within a reduced region of the initial feasible domain. This numerical technique has been used to identify two shear-type mechanical systems with 10 and 30 degrees-of-freedom, assuming as unknown parameters the mass, the stiffness, and the damping coefficients. The identification will be conducted starting from some noisy acceleration signals to verify, both the computational effectiveness and the accuracy of the proposed optimizer in presence of high noise-to-signal ratio. A critical and detailed analysis of the results is presented to investigate the inner work of the optimizer. Finally, its performances are examined and compared to the most recent results documented in the current literature to demonstrate the numerical competitiveness of the proposed strategy

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Base isolation has become a widely applied technique for protecting buildings located in highly seismic areas. Due to the strongly non-linear constitutive behaviour typical of many isolation devices, the seismic response of base-isolated buildings is usually evaluated through non-linear dynamic analysis. In this type of analysis a suitable set of ground motions is needed for representing the earthquake loads and for exciting the structural model. Many methods can be found in the literature for defining the ground motions. When natural accelerograms are used, the methods mainly differ from each other based on the intensity measures used for scaling the records to the defined earthquake intensity level. Investigations have been carried out for evaluating the predictive capability of the intensity measures used in these methods: while many studies focused on ordinary buildings, only a few focused on base-isolated ones. The objective of this paper is to evaluate the most commonly used intensity measures, which are currently available in the literature, with respect to their capability to predict the seismic response of base-isolated buildings. Selected for the investigation are two frame structures characterized by a different number of storeys and base-isolated with systems having different properties. Two sets of accelerograms, consisting of ordinary and pulse-like near-fault records, are used in the analyses and in the evaluation of the intensity measures. Modified versions of existing intensity measures are also proposed, with the intent of improving the correlations between the considered intensity measures and response quantities

The need to provide a rational explanation to the observed peculiar failure mode affecting the behaviour, at ultimate, of a Reinforced Concrete (RC) beam strengthened in shear by Near Surface Mounted (NSM) Fibre Reinforced Polymer (FRP) strips, led the authors to develop a comprehensive numerical model for simulating the NSM shear strength contribution to RC beams throughout the entire loading process as function of the Critical Diagonal Crack (CDC) opening angle. That model was respectful of equilibrium, kinematic compati-bility and constitutive laws. Despite its high level of prediction accuracy, taking into account all of the possible failure modes, as well as the interaction among adjacent strips, that model resulted relatively complex to be easily implemented in a practitionersaddressed building regulations code. Yet, it can be conveniently simplified into a more user-friendly and closed-form design formula. Crucial point of that simplification is the development of a reliable constitutive analytical law providing the single strip strength as function of the imposed end slip. This paper presents the modelling strategy adopted to determine that constitutive law, as well as its final analytical expression. © Tsinghua University Press, Beijing and Springer-Verlag Berlin Heidelberg 2011