m. r. mohammadizadeh

In recent years, there has been a lot of interest in the development and deployment of control methods that use different components of the building to mitigate the seismic response of the structure. Meanwhile, the building facade, as a non-structural component, can be a suitable alternative in affecting the structure's behavior because of its role as an envelope of the building with a significant weight. Among the modular cladding systems, the Double Skin Facade (DSF) can be considered a passive system due to the distance of the exterior layer from the main structure and sufficient continuity and rigidity.  In this study, DSF systems are used as Peripheral Mass Dampers (PMDs) that control structural movements by dissipating energy during strong motions. The PMD system provides a building with several inherent dampers without the need for extra mass. To show the reliability and efficiency of the proposed approach, the PMD model is investigated and compared with results available in uncontrolled and Tuned Mass Damper (TMD) models. The PMD model is examined in three structural frames with 10, 20, and 30 stories with the extreme Mass Ratios (MRs) of 5% to 20%. The Particle Swarm Optimization (PSO) is performed on damper parameters of PMD and TMD systems to minimize structural responses. The results demonstrate that an optimal PMD system with multiple inherent mass dampers outperforms a single TMD system.

This study presents a new method of damage detection using a combination of the second-order gradient Levenberg-Marquardt algorithm (SOGLMA) and fuzzy logic (FL) to solve the nonlinear damage detection equation for space frame structures. For damage detection in structures with a large number of degrees of freedom using the second-order gradient Levenberg-Marquardt algorithm, it is necessary to perform an iterative process of analysis and solving a set of simultaneous nonlinear equations that requires a lot of time. Therefore, the computation time and the number of iterations are reduced by using the proposed method "Combination of the second-order gradient Levenberg-Marquardt algorithm and fuzzy logic (SOGLMA-FL)". Acceleration response in sensor nodes obtained at different time steps from dynamic analysis are considered as input values for fuzzification. The output values of the proposed method after defuzzification are the damage extent of structural elements. The results show that the proposed damage detection method (SOGLMA-FL) has faster convergence, lower numbers of iteration and reduced computation time than the damage detection method (SOGLMA) for space frame structures.

This paper describes the changes in TiO2/SiO2 nanolayers properties induced by Ultraviolet- visible spectroscopy (UV) irradiation in terms of hydrophilicity/photocatalycity. The TiO2/SiO2 nano particles were synthesized by the sol-gel method and deposited on soda-lime glass by dip-coating. X-ray diffraction (XRD) of the TiO2 particles showed that the nano-particles were crystallized in anatase crystal structure with a crystallite size of ~12 nm. The morphology and surface roughness of TiO2 nanolayer were observed by scanning electron microscope (SEM) and atomic force microscopy (AFM) analysis. The surface roughness (Ra) for TiO2/Glass and TiO2/SiO2 was measured ~ 5 and 19 nm, respectively. The hardness of nanolayers on the glass was evaluated and scratch thickness for 1000 g sinker was measured ~150 nm. The self-cleaning properties were tested in dry condition (RH<15%) under UV irradiation by evaluating the oleic acid photodegradation and monitoring the hydrophilic properties of the surface with a contact angle measurement. The  result showed that contact angle of the layer decreases from 77 to 42° after 25 h UV irradiation. Fourier-transform infrared spectroscopy- Attenuated total reflectance (FTIR-ATR) showed the elimination of C=O bonds of oleic acid on the surface after UV light irradiation. Water droplet contact angle measurement on TiO2 nano-layer exhibited a less hydrophilicity after UV irradiation and the contact angle changed  from 15 to 40°, which may be due to the low atmospheric humidity. Adding SiO2 nanoparticles increases roughness of the nano-layer, from 5 to 19 nm, without a significant effect on the photodegradation rate of oleic acid.

The purpose of the present study is the damage detection in the thin plates in terms of the wide application of such structures in various branches of engineering such as structural, mechanical, aerospace, shipbuilding, etc. using gradient-based second-order numerical optimization techniques. The technique used for optimization in this study is the second-order Levenberg-Marquardt algorithm (SOLMA). Using the acceleration response in a number of structural nodes under dynamic excitation, identification of the location and extent of damage in the plate elements are obtained by the proposed algorithm over an iterative cycle and by updating the sensitivity matrix. The damage has been assumed in the form of decreased modulus of elasticity in linear mode. A numerical problem has been solved and presented in order to verify and compare the proposed damage detection method with other methods. Also several numerical problems have been solved and its results have been presented in order to evaluate different scenarios such as one or more damages, small or large damage extent, absence or presence of noise with different levels, number of measured responses (number of sensors), position of measured points and the dynamic analysis time of the damage detection problem with the proposed method. The results show the appropriate accuracy, efficiency and performance of the proposed damage detection method.

In this work structural defects were created in P25-TiO2 nanoparticles by using hydrogen DC plasma treatment in different temperatures and exposure times. X-Ray diffraction measurements show that the structure of TiO2 remains unchanged after hydrogenation. Diffuse reflectance spectroscopy measurements demonstrated band gap of TiO2 was not changed considerably by the hydrogenation. However, by applying the hydrogen plasma for 40 min at temperature of 350 °C photocatalytic activity of TiO2 nanoparticles enhances. No more change was observed in the photocatalytic activity of the samples with plasma exposure time more than 40 min. Photoluminescence analysis shows the sample prepared at 350 °C has a large amount of defects which have been created by the plasma treatment. It seems both, structural defects and hydrogen doping in the samples are important for more efficient photocatalytic behavior of TiO2 nanoparticles.