Numerical performance assessment of Tuned Mass Dampers to mitigate traffic-induced vibrations of a steel box-girder bridge

Elyas Bayat,Meysam Bayat,Raheb Hafezzadeh 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.78 No.2

In this paper, the effects of Tuned Mass dampers (TMDs) on the reduction of the vertical vibrations of a real horizontally curved steel box-girder bridge due to different traffic loads are numerically investigated. The performance of TMDs to reduce the bridge vibrations can be affected by the parameters such as dynamic characteristics of TMDs, the location of TMDs, the speed and weight of vehicles. In the first part of this study, the effects of mass ratio, damping percentage, frequency ratio, and location of TMDs on the performance of TMDs to decrease vertical vibrations of different sections of bridge deck are evaluated. In the second part, the performance of TMD is investigated for different speeds and weights of traffic loads. Results show that the mass ratio of TMDs is the more effective parameter in reducing imposed vertical vibration in comparison with the damping ratio. Furthermore, it is found that TMD is very sensitive to its tuned frequency, i.e., with a little deviation from a suitable frequency, the expected performance of TMD significantly decreased. TMDs have a positive and considerable performance at certain vehicle speeds and this performance declines when the weight of traffic loads is increased. Besides, the results reveal that the highest impact of TMD on the reduction of the vertical vibrations is when free vibrations occur for the bridge deck. In that case, maximum reductions of 24% and 59% are reported in the vertical acceleration of the bridge deck for the forced and free vibration amplitudes, respectively. The maximum reduction of 13% is also obtained for the maximum displacement of the bridge deck. The results are mainly related to the resonance condition.

The CRISPR Growth Spurt: from Bench to Clinic on Versatile Small RNAs

( Hadi Bayat ),( Meysam Omidi ),( Masoumeh Rajabibazl ),( Suriana Sabri ),( Azam Rahimpour ) 한국미생물 · 생명공학회 2017 Journal of microbiology and biotechnology Vol.27 No.2

Clustered regulatory interspaced short palindromic repeats (CRISPR) in association with CRISPR-associated protein (Cas) is an adaptive immune system, playing a pivotal role in the defense of bacteria and archaea. Ease of handling and cost effectiveness make the CRISPR-Cas system an ideal programmable nuclease tool. Recent advances in understanding the CRISPRCas system have tremendously improved its efficiency. For instance, it is possible to recapitulate the chronicle CRISPR-Cas from its infancy and inaugurate a developed version by generating novel variants of Cas proteins, subduing off-target effects, and optimizing of innovative strategies. In summary, the CRISPR-Cas system could be employed in a number of applications, including providing model systems, rectification of detrimental mutations, and antiviral therapies.

Metabotropic Effect of Probiotic Supplementation and High-Intensity Interval Training in Menopause-Induced Metabolic Syndrome in Rats

Zeinab Bayat,Arsalan Damirchi,Meysam Hasannejad-Bibalan,Parvin Babaei 대한폐경학회 2023 대한폐경학회지 Vol.29 No.1

Objectives: This study aimed to investigate the interactive effect of supplementation with a native potential probiotic lactobacillus and 8-week high-intensity interval training (HIIT) on insulin resistance and dyslipidemia in a menopause-induced metabolic syndrome.Methods: A total of 40 ovariectomized (OVX) Wistar rats were divided into five groups: control (OVX + Vehicle), exercise (EXE) (OVX + Exe), probiotic (Prob) (OVX + Prob), exercise and probiotic (OVX + Exe + Prob), and sham surgery. After the end of the treatment interventions, body weight, body mass index (BMI), waist circumference (WC), visceral fat, and serum concentrations of glucose, insulin, lipid profile, and adiponectin were measured using colorimetric analysis and enzyme-linked immunosorbent assay, respectively.Results: Data revealed a significant decrease in weight, waist circumference , visceral fat, BMI, and levels of glucose, insulin, homeostasis model assessment of insulin resistance, triacylglyceride, total cholesterol, and low-density lipoprotein (LDL), but an increase in high-density lipoprotein and adiponectin levels (P = 0.001), in OVX + Exe + Prob compared with the OVX + Vehicle group.Conclusions: The present study indicates that native probiotic lactobacillus combined with HIIT effectively reduces body weight, visceral fat, and levels of LDL, glucose, and insulin and increases adiponectin level, although exercise contributes more to fat reduction and probiotics to insulin resistance.

Experimental Study on Mechanical Properties of Cement-Stabilized Soil Blended with Crushed Stone Waste

Mohsen Salehi,Meysam Bayat,Mohsen Saadat,Masoud Nasri 대한토목학회 2021 KSCE Journal of Civil Engineering Vol.25 No.6

Waste generated by the processing of natural stone poses environmental and economic problems. One promising use for stone waste is soil stabilization. In this paper, a number of tests including unconfined compressive strength (UCS) and California bearing ratio (CBR) of crushed stone were performed to study the effect of curing time, soaked and unsoaked conditions and freeze-thaw cycles on the geotechnical characteristics of cement-stabilized specimens. The results indicate that crushed stone waste can be combined with cement as a stabilizer to improve soil properties. Also the optimum moisture content (OMC) and maximum dry density (MDD) are dependent on the cement content and almost independent of the crushed stone waste content. The CBR increased significantly as the crushed stone waste and cement contents increased under both soaked and unsoaked conditions, but these had little effect on the UCS at curing times of less than 14 days. Cement-stabilized specimens with 10% crushed stone waste showed a significant increase in UCS. The CBR and UCS of unsoaked specimens were higher than for soaked specimens at different crushed stone waste and cement contents. The CBR and UCS values increased with an increase in curing time. However, the curing time had a more obvious effect on UCS than on CBR.

Transient analysis of monopile foundations partially embedded in liquefied soil

Barari, Amin,Bayat, Mehdi,Saadati, Meysam,Ibsen, Lars Bo,Vabbersgaard, Lars Andersen Techno-Press 2015 Geomechanics & engineering Vol.8 No.2

In this study, the authors present a coupled fluid-structures-seabed interaction analysis of a monopile type of wind turbine foundations in liquefiable soils. A two dimensional analysis is performed with a nonlinear stiffness degradation model incorporated in the finite difference program Fast Lagrangian Analysis of Continua (FLAC), which captured the fundamental mechanisms of the monopiles in saturated granular soil. The effects of inertia and the kinematic flow of soil are investigated separately, to highlight the importance of considering the combined effect of these phenomena on the seismic design of offshore monopiles. Different seismic loads, such as those experienced in the Kobe, Santa Cruz, Loma Prieta, Kocaeli, and Morgan Hill earthquakes, are analyzed. The pore water pressure development, relative displacements, soil skeleton deformation and monopile bending moment are obtained for different predominant frequencies and peak accelerations. The findings are verified with results in the liter.

Combined Influences of Cement, Rice Husk Ash and Fiber on the Mechanical Characteristics of a Calcareous Sand

Kamran Tavakol,Meysam Bayat,Bahram Nadi,Rassoul Ajalloeian 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.9

Many available stabilisers and reinforcements have been used to enhance the mechanical characteristics of silica sand. So far, many studies have been carried out to understand the influence of various old and new additives such as natural and synthetic fibres or traditional stabilisers on the mechanical characteristics of silica sands. However, there is minimal study on the mechanical characteristics of stabilised or reinforced calcareous sands. The main focus of the current study was to evaluate the influences of relative density (Dr), Portland cement (C) content, rice husk ash (RHA) content and synthetic polypropylene fibre (PPF) content on the mechanical characteristics of a calcareous sand, which were: Dr [30%, 80%], C [0, 3%, 5%, 7.5%], RHA [0, 7%, 7.5%, 10%], and PPF [0%, 1%]. For this purpose, direct shear tests have been conducted on treated calcareous sand subjecting to three curing times (7, 14, and 28 days). The test results indicate that adding cement, rice husk ash and polypropylene fibre increases the shear strength and reduces the volumetric strain under shear loading. Thespecimens containing 7.5% cement and 7.5% RHA generally exhibited the highest shear strength and the lowest volumetric strain. Relative density, cement content, RHA content, fibre content and curing time have more important effects on the cohesion than the friction angle of treated specimens.

Effect of Geogrid Reinforcement and Soil Relative Density on Performance and Contact Pressures of Ring Foundations on Sand

Masoud Rezazadeh Anbarani,Saeed Abrishami,Meysam Bayat 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.12

Reinforcing soil beneath foundations is one of the standard methods to improve the foundation performance. However, soil relative density may affect the efficiency of reinforcement. This experimental study has been conducted on a model ring foundation resting on medium, dense, and very dense geogrid-reinforced sand. For this purpose, 17 tests were carried out to evaluate the effect of soil density and reinforcement depth and size on bearing capacity and settlement of the ring foundation and its normal contact pressure distribution. The results show that geogrid-reinforced sand with higher relative densities improves bearing capacity and decreases settlements significantly. It can be shown that implementing a geogrid layer that is equal to the dimensions of the footing is cost-effective. The scale effect analysis has been conducted for the model foundation, sand, and geogrid used in this research. Additionally, normal contact pressure distributions for unreinforced and reinforced sand are presented. Decreasing the depth of reinforcement transforms the form of normal contact pressure distribution from saddle to parabolic.