Multi-level structural modeling of an offshore wind turbine

Petrini, Francesco,Gkoumas, Konstantinos,Zhou, Wensong,Li, Hui Techno-Press 2012 Ocean systems engineering Vol.2 No.1

Offshore wind turbines are complex structural and mechanical systems located in a highly demanding environment. This paper proposes a multi-level system approach for studying the structural behavior of the support structure of an offshore wind turbine. In accordance with this approach, a proper numerical modeling requires the adoption of a suitable technique in order to organize the qualitative and quantitative assessment in various sub-problems, which can be solved by means of sub-models at different levels of detail, both for the structural behavior and for the simulation of loads. Consequently, in a first place, the effects on the structural response induced by the uncertainty of the parameters used to describe the environmental actions and the finite element model of the structure are inquired. After that, a meso-level FEM model of the blade is adopted in order to obtain the detailed load stress on the blade/hub connection.

Basis of design and numerical modeling of offshore wind turbines

Petrini, Francesco,Li, Hui,Bontempi, Franco Techno-Press 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.36 No.5

Offshore wind turbines are relatively complex structural and mechanical systems located in a highly demanding environment. In the present paper the fundamental aspects and the major issues related to the design of these special structures are outlined. Particularly, a systemic approach is proposed for a global design of such structures, in order to handle coherently their different parts: the decomposition of these structural systems, the required performance and the acting loads are all considered under this philosophy. According to this strategy, a proper numerical modeling requires the adoption of a suitable technique in order to organize the qualitative and quantitative assessments in various sub-problems, which can be solved by means of sub-models at different levels of detail, for both structural behavior and loads simulation. Specifically, numerical models are developed to assess the safety performances under aerodynamic and hydrodynamic actions. In order to face the problems of the actual design of a wind farm in the Mediterranean Sea, in this paper, three schemes of turbines support structures have been considered and compared: the mono pile, the tripod and the jacket support structure typologies.

Coupling effects between wind and train transit induced fatigue damage in suspension bridges

Francesco Petrini,Pierluigi Olmati,Franco Bontempi 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.70 No.3

Long-span steel suspension bridges develop significant vibrations under the effect of external time-variable loadings because their slenderness. This causes significant stresses variations that could induce fatigue problems in critical components of the bridge. The research outcome presented in this paper includes a fatigue analysis of a long suspension bridge with 3300 meters central suspended span under wind action and train transit. Special focus is made on the counterintuitive interaction effects between train and wind loads in terms of fatigue damage accumulation in the hanger ropes. In fact the coupling of the two actions is shown to have positive effects for some hangers in terms of damage accumulation. Fatigue damage is evaluated using a linear accumulation model (Palmgren-Miner rule), analyses are carried out in time domain by a three-dimensional non-linear finite element model of the bridge. Rational explanation regarding the above-mentioned counterintuitive behavior is given on the basis of the stress time histories obtained for pertinent hangers under the effects of wind and train as acting separately or simultaneously. The interaction between wind and train traffic loads can be critical for a some hanger ropes therefore interaction phenomena within loads should be considered in the design.

Basis of design and numerical modeling of offshore wind turbines

Francesco Petrini,Hui Li,Franco Bontempi 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.36 No.5

Offshore wind turbines are relatively complex structural and mechanical systems located in a highly demanding environment. In the present paper the fundamental aspects and the major issues related to the design of these special structures are outlined. Particularly, a systemic approach is proposed for a global design of such structures, in order to handle coherently their different parts: the decomposition of these structural systems, the required performance and the acting loads are all considered under this philosophy. According to this strategy, a proper numerical modeling requires the adoption of a suitable technique in order to organize the qualitative and quantitative assessments in various sub-problems, which can be solved by means of sub-models at different levels of detail, for both structural behavior and loads simulation. Specifically, numerical models are developed to assess the safety performances under aerodynamic and hydrodynamic actions. In order to face the problems of the actual design of a wind farm in the Mediterranean Sea, in this paper, three schemes of turbines support structures have been considered and compared: the mono pile, the tripod and the jacket support structure typologies.

Numerical analyses for the structural assessment of steel buildings under explosions

Olmati, Pierluigi,Petrini, Francesco,Bontempi, Franco Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.45 No.6

This paper addresses two main issues relevant to the structural assessment of buildings subjected to explosions. The first issue regards the robustness evaluation of steel frame structures: a procedure is provided for computing "robustness curves" and it is applied to a 20-storey steel frame building, describing the residual strength of the (blast) damaged structure under different local damage levels. The second issue regards the precise evaluation of blast pressures acting on structural elements using Computational Fluid Dynamic (CFD) techniques. This last aspect is treated with particular reference to gas explosions, focusing on some critical parameters (room congestion, failure of non-structural walls and ignition point location) which influence the development of the explosion. From the analyses, it can be deduced that, at least for the examined cases, the obtained robustness curves provide a suitable tool that can be used for risk management and assessment purposes. Moreover, the variation of relevant CFD analysis outcomes (e.g., pressure) due to the variation of the analysis parameters is found to be significant.

Pretreatment of normal responders in fresh in vitro fertilization cycles: A comparison of transdermal estradiol and oral contraceptive pills

Pereira, Nigel,Petrini, Allison C.,Zhou, Zhen N.,Lekovich, Jovana P.,Kligman, Isaac,Rosenwaks, Zev The Korean Society for Reproductive Medicine 2016 Clinical and Experimental Reproductive Medicine Vol.43 No.4

Objective: The aim of this study was to investigate the impact of pretreatment with transdermal estradiol ($E_2$) compared to oral contraceptive pills (OCPs) on controlled ovarian stimulation (COS) response in normal responders undergoing fresh in vitro fertilization (IVF)-embryo transfer (ET) cycles. Methods: A retrospective cohort study was performed of normal responders undergoing fresh IVF-ET cycles who received pretreatment with transdermal $E_2$ versus OCPs prior to fresh IVF-ET. The total days of ovarian stimulation, total dosage of gonadotropins, total number of oocytes, and mature oocytes retrieved were noted. Pregnancy outcomes after ET were also recorded. Results: A total of 2,092 patients met the inclusion criteria: 1,057 and 1,035 patients in the transdermal $E_2$ and OCP groups, respectively. Patients in the OCP group had a longer duration of COS ($10.7{\pm}1.63days$, p< 0.01) than the $E_2$ group ($9.92{\pm}1.94days$). Patients in the OCP group also required higher cumulative doses of gonadotropins ($2,657.3{\pm}1,187.9IU$) than those in the $E_2$ group ($2,550.1{\pm}1,270.2IU$, p= 0.002). No statistically significant differences were found in the total and mature oocytes retrieved or in the rates of biochemical pregnancy, clinical pregnancy, spontaneous miscarriage, and live birth between the groups. Conclusion: Our findings suggest that compared to OCPs, pretreatment with transdermal $E_2$ is associated with a shorter duration of ovarian stimulation and lower gonadotropin utilization, without compromising the oocyte yield or pregnancy outcomes in normal-responder patients undergoing fresh IVF.

Improving the Force and Time Response of a DC Solenoid Electromagnetic Actuator by Changing the Lower Core Angle

Eduard Plavec,Miroslav Petrini?,Mladen Vidovi? 한국전자파학회JEES 2021 Journal of Electromagnetic Engineering and Science Vol.21 No.2

The aim of almost any electromagnetic actuator development is to increase the electromagnetic force with which an actuator acts on a plunger with as fast a time response as possible while maintaining the dimensions as small as possible. This paper presents research on the impact of the lower core angle on the force and time response of a DC solenoid electromagnetic actuator. The research method is based on the analytical analysis of the magnetic path of the DC solenoid electromagnetic actuator and a comparison with the numerical simulation results. A transient numerical simulation was performed on a 2D axial-symmetric model of the electromagnetic actuator and included simultaneously solving time-dependent partial differential equations of the electromagnetic actuator’s magnetic, electrical, and mechanical subsystems. The magnetic subsystem was analyzed by the finite element method (FEM) using the ANSYS Electronics software package. The three prototype models with different lower core angles were produced and tested in the accredited Laboratory Center of KONČAR Electrical Engineering Institute. The obtained measurements are compared with the analytical results and numerical simulation results.

Numerical analyses for the structural assessment of steel buildings under explosions

Pierluigi Olmati,Francesco Petrini,Franco Bontempi 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.45 No.6

This paper addresses two main issues relevant to the structural assessment of buildings subjected to explosions. The first issue regards the robustness evaluation of steel frame structures: a procedure is provided for computing “robustness curves” and it is applied to a 20-storey steel frame building, describing the residual strength of the (blast) damaged structure under different local damage levels. The second issue regards the precise evaluation of blast pressures acting on structural elements using Computational Fluid Dynamic (CFD) techniques. This last aspect is treated with particular reference to gas explosions, focusing on some critical parameters (room congestion, failure of non-structural walls and ignition point location) which influence the development of the explosion. From the analyses, it can be deduced that, at least for the examined cases, the obtained robustness curves provide a suitable tool that can be used for risk management and assessment purposes. Moreover, the variation of relevant CFD analysis outcomes (e.g., pressure) due to the variation of the analysis parameters is found to be significant.

Prevalence and risk factors for carriage of multi-drug resistant Staphylococci in healthy cats and dogs

Paola Gandolfi-Decristophoris,Gertraud Regula,Orlando Petrini,Jakob Zinsstag,Esther Schelling 대한수의학회 2013 Journal of Veterinary Science Vol.14 No.4

We investigated the distribution of commensal staphylococcal species and determined the prevalence of multi-drug resistance in healthy cats and dogs. Risk factors associated with the carriage of multi-drug resistant strains were explored. Isolates from 256 dogs and 277 cats were identified at the species level using matrix-assisted laser desorption ionisation-time of flight mass spectrometry. The diversity of coagulase-negative Staphylococci (CNS) was high, with 22 species in dogs and 24 in cats. Multi-drug resistance was frequent (17%) and not always associated with the presence of the mecA gene. A stay in a veterinary clinic in the last year was associated with an increased risk of colonisation by multi-drug resistant Staphylococci (OR = 2.4, 95% CI: 1.1∼5.2, p value LRT = 0.04). When identifying efficient control strategies against antibiotic resistance, the presence of mechanisms other than methicillin resistance and the possible role of CNS in the spread of resistance determinants should be considered. We investigated the distribution of commensal staphylococcal species and determined the prevalence of multi-drug resistance in healthy cats and dogs. Risk factors associated with the carriage of multi-drug resistant strains were explored. Isolates from 256 dogs and 277 cats were identified at the species level using matrix-assisted laser desorption ionisation-time of flight mass spectrometry. The diversity of coagulase-negative Staphylococci (CNS) was high, with 22 species in dogs and 24 in cats. Multi-drug resistance was frequent (17%) and not always associated with the presence of the mecA gene. A stay in a veterinary clinic in the last year was associated with an increased risk of colonisation by multi-drug resistant Staphylococci (OR = 2.4, 95% CI: 1.1∼5.2, p value LRT = 0.04). When identifying efficient control strategies against antibiotic resistance, the presence of mechanisms other than methicillin resistance and the possible role of CNS in the spread of resistance determinants should be considered.

Knowledge, attitude, practice and barriers of cervical cancer screening among women living in mid-western rural, Nepal

Niresh Thapa,Muna Maharjan,Marcia A. Petrini,Rajiv Shah,Swati Shah,Narayani Maharjan,Navin Shrestha,Hongbing Cai 대한부인종양학회 2018 Journal of Gynecologic Oncology Vol.29 No.4

OBJECTIVE: To find out the knowledge, attitude, practice, and barriers of cervical cancer screening in mid-western rural, Nepal. METHODS: A hospital-based cross-sectional study was conducted. Women aged 20 or more were interviewed using a structured questionnaire regarding the socio-demographic information, knowledge, attitude, practice, and barriers to the cervical cancer screening. RESULTS: Total of 360 participants were recruited for this study, mean age was 30.13±10.4 years. More than 87% of participants had inadequate knowledge, but around 72% had a favorable attitude towards cervical cancer screening. There was a significant portion of women (86.4%) had never done any cervical cancer screening test. Despite being higher literacy rate of Brahmin and Chhetri ethnic group, they were less likely to attend the cervical cancer screening than Dalit and Janajati (p<0.001); and those who had a positive family history of cancer were more likely to attend the cervical cancer screening (p<0.001). Similarly, married women, who had adequate knowledge and or favorable attitude, were more likely to practice cervical cancer screening, though statistically not significant. Factors such as "No symptoms," "Lack of awareness," "Embarrassment," etc. were the most common barriers for the cervical cancer screening. CONCLUSION: The adequate knowledge and practice of cervical cancer screening were meager among rural Nepalese women, but most of them had a favorable attitude. There is an imperative need for related awareness programs to promote the uptake of cervical cancer screening tests.