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The conventional modal strain energy (MSE), as a practical objective function, suffers from the lack of access to the damaged stiffness matrix and uses the intact stiffness matrix of the structure instead. To overcome the aforementioned deficiency of the MSE, this study proposes a reformed elastic strain energy-dissipation criterion called the "augmented modal strain energy" (AMSE) which is composed of relative differences of natural frequency and mode shape. In the AMSE not only the effects of the energy-dissipation criterion as a function of natural frequency but also the equilibria of the elastic strain energy as a function of mode shape are considered. Hereupon, the AMSE is implemented along with the interactive autodidactic school (IAS) optimization algorithm to investigate the effectiveness of the proposed identification method. In this regard, the AMSE is verified by assessing three benchmark truss and frame structures. The obtained results confirm the reliable performance of AMSE in both terms of intensification and diversification. Furthermore, it is observed that despite using noise-polluted modal data, the proposed AMSE not only identifies the damage location accurately, but also anticipates the extent of damage precisely. Consequently, the proposed energy-dissipation-based objective function (AMSE) is suggested, along with the IAS optimization algorithm, as a robust technique for the damage detection of structures. [ABSTRACT FROM AUTHOR]

Fiber concretes, as a new generations of concrete, have considerably attracted the attention of researchers and engineers for a couple of decades. Fibers play a very important role for improving the weaknesses of concrete, including the tensile and flexural strengths of concrete. In this paper, the effect of length and percentage of steel fibers on the tensile and compressive strengths of concrete is investigated. For this propose, three concrete samples including plain concrete and fiber concretes with steel fibers with lengths of 3 and 5 cm each with different volume ratios (i.e., 0.5, 1, and 1.5%) have been tested. In addition, the samples of the plain concrete are made to determine the effect of fibers on the strength of the concrete. Afterward, using the hydrulic jack machine, both tension and compression strength tests are performed on the concrete specimens. Based on the obtained results, it is observed that with increasing the length and percentage of steel fibers, the tensile and compressive strengths of the concrete specimens are increased. Furtheromre, the samples containing a combination of 3 and 5 cm steel fibers in concrete have lower strength than samples with only 5 cm fibers and more strength than samples with only 3 cm fibers. According to experiments, in order to increase the tensile and compressive strength of concrete, the use of 5 cm steel fibers with different percentages is preferable to 3 cm steel fibers. [ABSTRACT FROM AUTHOR]

In the past few years, many studies have proved the efficiency of Simple Adaptive Control (SAC) in mitigating earthquakes' damages to building structures. Nevertheless, the weighting matrices of this controller should be selected after a large number of sensitivity analyses. This step is time-consuming and it will not necessarily yield a controller with optimum performance. In the current study, an innovative method is introduced to tuning the SAC's weighting matrices, which dispenses with excessive sensitivity analysis. In this regard, we try to define an optimization problem using intelligent evolutionary algorithm and utilized control indices in an objective function. The efficiency of the introduced method is investigated in 6-story building structure equipped with magnetorheological dampers under different seismic actions with and without uncertainty in the model of the proposed structure. The results indicate that the controller designed by the introduced method has a desirable performance under different conditions of uncertainty in the model. Furthermore, it improves the seismic performance of structure as compared to controllers designed through sensitivity analysis. [ABSTRACT FROM AUTHOR]

From the past up to now, selecting a reliable structural system as well as analyzing and designing it accurately have considerably attracted the attention of researchers and engineers. An appropriate evaluation of the dynamic characteristics of the structures such as natural frequency and damping ratio has a considerable effect on the accurate analysis and design of structures. In addition, the vulnerability assessment of structures plays a significant role in selecting a resilient structural system against the seismicity of the area. In the light of these facts, one of the most important challenges is that the effects of non-structural components (NSCs) are commonly considered as a concentrated/distributed mass in most FE models and their stiffness and damping ratio are ignored. Therefore, this research aims to figure out the effects of NSCs on the dynamic characteristics and the vulnerability indices of concrete structures using microtremor measurements. For this purpose, the ambient vibrations of four concrete buildings (with two bending frame and two shear wall structural systems) during the construction process are measured in three independent stages: (1) after the completion of the structural system; (2) after the completion of the interior and exterior partition walls; (3) after the completion of the flooring, facade, and parapet elements (when the building is completely constructed). Afterward, to extract the dynamic characteristics and to compute the vulnerability indices of the structures, the measured microtremors are subjected to two signal processing techniques, i.e., floor spectral ratio (FSR) and random decrement method (RDM). It is observed that, by taking the effects of NSCs into account, the values of both dynamic characteristics of the concrete structures (i.e., natural frequency and damping ratio) are increased when the buildings are under the erection process. Furthermore, the obtained results for the concrete structures with the bending frame structural system demonstrate that the vulnerability index increases in the second stage compared with the first one, whereas it remarkably decreases in the third stage compared with the second one. Reciprocally, the obtained vulnerability indices for the concrete structures with the shear wall structural system show a similar behavior. • The effects of NSCs on the dynamic characteristics and the vulnerability of concrete structures are investigated. • The ambient vibrations of four concrete buildings during the construction process are measured. • Two robust signal processing techniques, i.e., floor spectral ratio and random decrement method, are utilized. • The NSCs have considerable effect on the dynamic characteristics and the vulnerability index of structures. • The effects of the stiffness and damping of the NSCs should be basically considered and applied in the structural models. [ABSTRACT FROM AUTHOR]

On 10 April 2020, Iran reported 68,192 COVID-19 cumulative cases including 4232 death and 35,465 recovery cases. Numerous factors could influence the transmission rate and survival of coronavirus. On this basis and according to the latest epidemiological researches, both ambient temperature (AT) and population size (PS) can be considered as significant transmissibility factors for coronavirus. The analysis of receiver operating characteristics (ROC) allows measuring the performance of a classification model using the confusion matrix. This study intends to investigate the sensitivity of AT and PS on the transmission rate of the novel coronavirus in different provinces of Iran. For this purpose, the information of each province of Iran including the annual average of AT and the number of healthy and diseased cases are categorized. Subsequently, the sensitivity and specificity analyses of both AT and PS factors are performed. The obtained results confirm that AT and PS have low sensibility and high sensitivity, respectively. Thus, there is no scientific reason to confirm that the number of COVID-19 cases in warmer climates is less than that of moderate or cold climates. Therefore, it is recommended that the cities/provinces with a population of over 1.7 million people have stricter inspections and more precise controls as their management policy. Unlabelled Image • The population size (PS) sensitivity on the spread rate of COVID-19 is assessed. • Likewise, the ambient temperature (AT) sensibility is estimated. • The transmission rate of the COVID-19 has a low sensibility to the variations of AT. • The transmission rate of the COVID-19 has a high sensitivity to the variations of PS. • The PS of over 1.7 million can enhance the transmission rate of the COVID-19 disease. [ABSTRACT FROM AUTHOR]

• A new metaheuristic algorithm, Interactive Autodidactic School (IAS), is proposed. • IAS is inspired by interactions of a group of autodidactic students. • Twenty mathematical and seven structural design optimization problems are examined. • The results obtained by IAS are compared with other optimization methods. • The obtained results indicate the consummate performance of the IAS algorithm. A new efficient and robust metaheuristic algorithm called "Interactive Autodidactic School (IAS)" is proposed in this paper to solve numerical optimization and structural design optimization problems. IAS is a population-based algorithm on the basis of the interactions between students in an autodidactic school with the goal of increasing their knowledge through a combination of self-teaching/self-learning, interactive discussion, criticism, and the competition. IAS is tested in twenty mathematical optimization and seven structural optimization problems. Subsequently, its optimum solution is compared with other well-known optimization algorithms. The obtained results confirmed that the proposed IAS algorithm gives best optimal solution and has excellent performance compared with other optimization methods. [ABSTRACT FROM AUTHOR]