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Concrete is one of the most extensively utilized building materials that can be produced, and has the potential to release a significant quantity of CO2 into the environment. In this research, through studying lightweight (LW) concrete, attempts are made to produce environmentally friendly LW concrete with high strength using nanosilica rather than part of the cement and waste glass powder instead of aggregates. Recycled polypropylene fibers are used to increase the concrete’s compressive strength and nonlinear behavior. The use of glass powder was 20, 25, and 30% of the weight of aggregates, the consumption of nanosilica was 1, 2, and 3% of the weight of cement, and the consumption of recycled fibers (FORTA Ferro-Green) was 0.5, 1, and 1.5% of the weight of cement. Leca is also utilized as a LW aggregate. According to 7- and 28-day experimentation results and field emission scanning electron microscope analysis, the best sample had 1.5% fiber, 3% nanosilica, and 25% waste glass powder, and had a compressive and tensile strengths of roughly 1.7 and 1.6 times, respectively, those of the control specimen after 28 days. Also, using 3% nanosilica instead of cement can reduce greenhouse gas emissions by about 3%.

The objective of the present investigation is to introduce a novel adaptive fractional‐order proportional‐integral‐derivative controller, which is characterized by the online tuning of its parameters by utilizing five distinct multilayer perceptron neural networks employing the extended Kalman filter. Utilizing the backpropagation algorithm in training a multilayer perceptron neural network is deemed effective in identifying the structural system and estimating the plant. The controller is applied using the Jacobian derived from the online estimated model. The utilization of adaptive interval type‐2 fuzzy neural networks in conjunction with the extended Kalman filter tuning method and feedback error learning strategy results in enhanced stability and robustness of the controller in the face of estimation error, seismic disturbances, and unknown nonlinear functions. The study aims to validate the efficacy of the proposed controller by examining its performance on a 20‐story nonlinear building. The numerical results show that including a compensator enhances the performance of the adaptive fractional‐order proportional‐integral‐derivative controller. The results show that the proposed adaptive fractional‐order proportional‐integral‐derivative controller has a better performance than other controllers and that the interstory drift ratio criterion under the El Centro earthquake with a magnitude of 1.5 times experienced an improvement of up to 65% compared to other controllers, and this amount in the Kobe earthquake reached more than 58%. Other criteria have also experienced significant improvement using the proposed controller. [ABSTRACT FROM AUTHOR]

Axial forces are generated in the plates of ADAS-yielding dampers when subjected to lateral loading due to their boundary conditions. This on one hand can lead to an increase in strain level of the plates and accelerate the damage process, while on the other hand, the interaction of the bending moment with the tensile axial force leads to increasing strength, which is undesirable in the performance of ductile members. In this paper, a modified ADAS device (MADAS) is introduced to prevent undesirable interaction of axial forces, and its cyclic behavior is evaluated both experimentally and numerically. To this end, in the first step, two test specimens with different number of connection pins were prepared and subjected to cyclic loading in a rigid frame. Experimental and numerical results have shown that due to the removal of the constraint in the vertical direction, the level of forces produced by the damper is almost constant and the X-shaped plates have been able to tolerate significant number of cycles before crack initiation. Afterwards, the cyclic performance of ADAS and MADAS dampers was numerically compared individually and also when placed in the frame. Furthermore, in the frame equipped with ADAS damper, the increase in the level of forces produced by the damper led to the buckling of the braces, while the level of generated forces was totally in the expected range in the frame equipped with MADAS damper. [ABSTRACT FROM AUTHOR]

Summary: Hollow structural section (HSS) and concrete‐filled tube (CFT) cross‐sections have been widely employed in the columns and braces of special concentrically braced frames (SCBFs). Square‐HSS cross‐section widely used in multistory frames is filled with concrete and converted to square‐CFT cross‐section to enhance the behavior of this cross‐section. However, some investigations indicated that circular‐HSS cross‐section filled with concrete (circular‐CFT) showed better behavior in comparison with square‐CFT cross‐section due to more uniform and larger concrete confinement in circular‐CFT cross‐section. The current study was experimentally undertaken to evaluate (1) the seismic performance and the global and local hysteresis responses of HSS and CFT members with various cross‐section shapes from initial elastic range to collapse in the system level of multistory SCBFs, (2) the behavioral differences between square cross‐section and circular cross‐section, and (3) the behavioral differences between HSS cross‐sections and CFT cross‐sections employed in the columns and braces of SCBFs. Four full‐scale one‐bay, two‐story SCBFs with four various cross‐sections, namely, square‐HSS, circular‐HSS, square‐CFT, and circular‐CFT, for columns and braces were subjected to cyclic lateral loading. Evaluating base shear–roof drift hysteretic loops of SCBF specimens demonstrated that SCBF specimens with CFT columns and braces (CFT‐SCBFs) experienced respectively around 107%, 58%, 28%, and 152% higher stiffness, post‐yielding and post‐buckling strengths, ductility, and energy dissipation capacity than SCBF specimens with HSS columns and braces (HSS‐SCBF). In addition, the experimental observations indicated that CFT braces experienced local buckling initiation, crack initiation, and fracture at respectively 2.22, 2.35, and 2.32 times of roof drifts of those exhibited by HSS braces. Moreover, assessing braces with various cross‐sections indicated that CFT braces showed an increase in compression strength, post‐buckling strength, compression axial deformation, and out‐of‐plane buckling approximately by 83%, 152%, 127%, and 100%, respectively, in comparison with HSS braces. Finally, square‐HSS/CFT braces sustained rupture propagation better than circular‐HSS/CFT braces. [ABSTRACT FROM AUTHOR]