Application of Tuned Mass Dampers for Structural Vibration Control: A State-of-the-art Review

Given the burgeoning demand for construction of structures and high-rise buildings, controlling the structural vibrations under earthquake and other external dynamic forces seems more important than ever. Vibration control devices can be classified into passive, active and hybrid control systems. The technologies commonly adopted to control vibration, reduce damage, and generally improve the structural performance, include, but not limited to, damping, vibration isolation, control of excitation forces, vibration absorber. Tuned Mass Dampers (TMDs) have become a popular tool for protecting structures from unpredictable vibrations because of their relatively simple principles, their relatively easy performance optimization as shown in numerous recent successful applications. This paper presents a critical review of active, passive, semi-active and hybrid control systems of TMD used for preserving structures against forces induced by earthquake or wind, and provides a comparison of their efficiency, and comparative advantages and disadvantages. Despite the importance and recent advancement in this field, previous review studies have only focused on either passive or active TMDs. Hence this review covers the theoretical background of all types of TMDs and discusses the structural, analytical, practical differences and the economic aspects of their application in structural control. Moreover, this study identifies and highlights a range of knowledge gaps in the existing studies within this area of research. Among these research gaps, we identified that the current practices in determining the principle natural frequency of TMDs needs improvement. Furthermore, there is an increasing need for more complex methods of analysis for both TMD and structures that consider their nonlinear behavior as this can significantly improve the prediction of structural response and in turn, the optimization of TMDs

Impact Resistance of Concrete Containing LLDPE–Waste Tire Rubber and Silica Fume

Some of the desirable properties of concrete include high impact resistance and great energy-sucking capacity to name a few. These properties can be improved through the use of sustainable materials. This study investigated the effects of partly replacing fine aggregate with linear low-density polyethylene (LLDPE) and waste rubber (WR) as fine aggregates on the efficiency of concrete under impact loading. Two water to binder ratio (W/B) percentages of (0.40 and 0.55) were selected, with six (LLDPE-R) replacement grades (0%, 5%, 10%, 15%, 20%, and 30%) and two silica fume (SF) replacement grades (0% and 15%). Six cylinders with 150 and 60 mm were subjected to an impact by a 4.45 kg hammer striking. Test results indicated that impact resistance for the first visible crack and the ultimate failure increased with LLDPE-R content, where it increased by 4.76 times. This study also demonstrated that the impact resistance for the first visible crack of LLDPE-R concrete was improved by an average of 295% for specimens without SF and 292% for specimens containing SF. This enhancement for the ultimate failure is 291% and 290% for specimens without SF and containing SF, respectively

An Experimental Investigation of Mechanical Properties of The Ultra-High Performance Fiber Reinforced Concrete (UHPFRC)

Ultra-high performance concrete (UHPC) is a novel relatively construction material exhibiting enhanced mechanical and durability properties, which can lead to economical construction through reducing the cross-sections of structural. A study has been made through this investigation to understand the behavior of Ultra-High-Performance Concrete members with steel and polypropylene fibers. The research included the use of a cement, quartz sand, silica fume , steel fibers, polypropylene, superplasticizers and without using any type of aggregates other than the quartz sand Results show that it is possible to produce UHPFRC using materials that are available at the local markets if they are carefully selected and will achieve a minimum compressive strength of (170.32) MPa and The flexural strengths of (23.54 ) MPa and splitting tensile of( 19.1) MPa at the age of 28 days. This can be seen the experimental results showed a significant improvement in the residual mechanical properties of the concretes which contain the mix of fibers compared to concrete mixes without fibers. Keywords: Polypropylene  Fibers; Steel Fibers; Ultra High Performance Concrete DOI: 10.7176/CER/11-12-01 Publication date: December 31st 201

Tripartite symbiosis of Lentil (Lense culinaris L.), Mycorrhiza and Azospirillum brasilense under Rainfed Condition

A field experiment was conducted aiming to determine the possibility of improving the lentil performance when co-inoculated with Vesicular Arbuscular Mycorrhiza (VAM) fungi and Azospirillum under natural rain-fed conditions, in Iran. Results showed the substantial impact of VAM fungi on grain protein, root colonization and shoot dry weight. Highest value for shoot dry weight recorded in plants which inoculated with G. intraradices and highest values for root colonization and grain protein content was observed in plants which inoculated with G. mosseae. Also, Azospirillum had a significant effect on shoot dry weight and root colonization. A significant differences on grain protein content observed when combination of both microorganisms have been used

Study on the effect of Shahin-Dezh green Tuff on the mechanical characteristics of roller compact concrete

Due to the growing popularity of concrete structure and increasing use of them, especially Roller compacted concrete, applying Pozzolan and replacing cement with Pozzolan is very important. Nowadays, the use of the additive for cement replacement is common in RCC mix design due to its technical advantages and economic benefits as there is large quantity of Pozzolan mineral resources in Iran. In this paper the impact of produced concrete has been fully considered as well as the effect of this Pozzolan on the compressive strength, tensile strength and permeability by using green Tuff obtained from available Pozzolan in western Azarbaijan. The due results prove that Shahin-Dezh green Tuff improves concretes quality

Comparison of the Experimental and Predicted Data for Thermal Conductivity of Fe3O4/water Nanofluid Using Artificial Neural Networks

Objective(s): This study aims to evaluate and predict the thermal conductivity of iron oxide nanofluid at different temperatures and volume fractions by artificial neural network (ANN) and correlation using experimental data. Methods: Two-layer perceptron feedforward artificial neural network and backpropagation Levenberg-Marquardt (BP-LM) training algorithm are used to predict the thermal conductivity of the nanofluid. Fe3O4 nanoparticles are prepared by chemical co-precipitation method and thermal conductivity coefficient is measured using 2500TPS apparatus. Results: Fe3O4 nanofluids with particle size of 20-25 nm are used to test the effectiveness of ANN. Thermal conductivity of Fe3O4 /water nanofluid at different temperatures of 25, 30 and 35℃ and volume concentrations, ranging from 0.05% to 5% is employed as training data for ANN. The obtained results show that the thermal conductivity of Fe3O4 nanofluid increases linearly with volume fraction and temperature. Conclusions: the artificial neural network model has a reasonable agreement in predicting experimental data. So it can be concluded the ANN model is an effective method for prediction of the thermal conductivity of nanofluids and has better prediction accuracy and simplicity compared with the other existing theoretical methods

Effect of Twisted-Tape Turbulators and Nanofluid on Heat Transfer in a Double Pipe Heat Exchanger

Heat transfer and overall heat transfer in a double pipe heat exchanger fitted with twisted-tape elements and titanium dioxide nanofluid were studied experimentally. The inner and outer diameters of the inner tube were 8 and 16 mm, respectively, and cold and hot water were used as working fluids in shell side and tube side. The twisted tapes were made from aluminum sheet with tape thickness (d) of 1 mm, width (W) of 5 mm, and length of 120 cm. Titanium dioxide nanoparticles with a diameter of 30 nm and a volume concentration of 0.01% (v/v) were prepared. The effects of temperature, mass flow rate, and concentration of nanoparticles on the overall heat transfer coefficient, heat transfer changes in the turbulent flow regime Re≥2300, and counter current flow were investigated. When using twisted tape and nanofluid, heat transfer coefficient was about 10 to 25 percent higher than when they were not used. It was also observed that the heat transfer coefficient increases with operating temperature and mass flow rate. The experimental results also showed that 0.01% TiO2/water nanofluid with twisted tape has slightly higher friction factor and pressure drop when compared to 0.01% TiO2/water nanofluid without twisted tape. The empirical correlations proposed for friction factor are in good agreement with the experimental data