Experimental aerodynamical modeling of a generic bridge-deck section

master's thesis

• Title (croatian): Eksperimentalno aerodinamičko modeliranje generičkog presjeka mosta
• Author: Leo Pavletić
• Mentor: Hrvoje Kozmar (mentor)
• Mentor: Claudio Mannini https://orcid.org/0000-0002-3866-879X (komentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2023-03-29, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering

Abstract

Wind is a major natural phenomenon that needs to be considered while designing structures such as bridges. In wind-prone areas, it can cause large loads on bridges, followed by instabilities that lead to reduced performance, fatigue, or even failure. Its effect on structures can be investigated using various methods. In this thesis, the focus is on the experimental wind-tunnel testing method.
Two small-scale sectional models were made, each representing a generic box-girder bridge section with different width-to-depth ratios. Experiments were carried out in a boundary layer wind tunnel at the Inter-University Research Centre on Building Aerodynamics and Wind Engineering (CRIACIV) at the University of Florence, Italy. Static and dynamic tests were conducted in high- and low-turbulent flows. Aerodynamic loads (drag force, lift force, and pitch moment) were measured by a pair of high-frequency force balances for various flow incidence angles. Dynamic measurements were performed by the system containing a pair of optical lasers and shear-type frames for three different flow incidence angles. The dynamic response was determined for a single degree of freedom in a vertical direction.
The results indicate that aerodynamic loads in high- and low-turbulent flows have similarities in the trends observed on both models. However, a smaller width-to-depth ratio model is characterized by greater magnitudes of forces and moments. Dynamic test results indicate that the larger width-to-depth ratio model starts to oscillate at two different flow velocities. The model oscillates at a lower flow velocity due to secondary resonance at all flow incidence angles in a low-turbulent flow, while only the model at the flow incidence angle of +3° oscillates at a higher flow velocity due to galloping.

Abstract (croatian)

Vjetar je značajan prirodni fenomen koji je potrebno razmotriti prilikom projektiranja konstrukcija poput mostova. U područjima podložnim vjetru, vjetar može uzrokovati velika opterećenja praćena nestabilnostima, koja uzrokuju smanjenje stabilnosti mosta, zamor materijali te čak i urušavanje. Utjecaj vjetra na konstrukcije se može ispitati pomoću nekoliko različitih metoda. U okviru ovog rada, aerodinamička ispitivanja mostova su provedena eksperimentalnim metodama u zračnom tunelu.
Izrađena su dva sekcijska modela, od kojih svaki predstavlja generički sandučasti gredni most s određenim omjerom širine i visine. Eksperimenti su provedeni u zračnom tunelu za generiranje modela atmosferskog graničnog sloja u istraživačkom centru CRIACIV na Sveučilištu u Firenci, Italija. Statička i dinamička ispitivanja su provedena u visoko- i nisko-turbulentnom strujanju. Aerodinamička opterećenja (sila otpora, sila uzgona i moment posrtanja) su mjerena dvjema visokofrekventnim vagama za različite kuteve nastrujavanja zraka. Dinamički odziv mosta je mjeren za jedan stupanj slobode gibanja (u vertikalnom smjeru). Dinamička mjerenja su provedena pomoću sustava koji se temelji na lisnatim oprugama čiji su pomaci mjereni optičkim laserima za tri različita kuta nastrujavanja zraka.
Rezultati ukazuju na činjenicu da su aerodinamička opterećenja slična za dva ispitivana modela sekcije mosta. Model s većim omjerom širine i visine je podložan većim silama i momentima. Model s manjim omjerom širine i visine oscilira pri dvije različite brzine u nisko turbulentnom strujanju. Osciliranje pri nižim brzinama se javlja zbog sekundarne rezonancije za sve ispitane kuteve nastrujavanja zraka, dok je pri višim brzinama strujanja zraka model mosta s kutem nastrujavanja zraka +3° podložan oscilacijama uslijed galopiranja.

• Keywords: Bridge section; aerodynamic forces and moments; dynamic response; boundary layer wind tunnel
• Keywords (croatian): Sekcija mosta; aerodinamičke sile i momenti; dinamički odziv; zračni tunel za modeliranje atmosferskog graničnog sloja
• Language: english
• URN:NBN: urn:nbn:hr:235:289303
• Study programme: Title: Mechanical Engineering; specializations in: Design, Process and Energy Engineering, Production Engineering, Engineering Modelling and Computer Simulation, Marine Engineering, Industrial Engineering and Management, Materials Engineering, Mechatronics and Robotics, Autonomous Systems; Course: Engineering Modelling and Computer Simulation; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka strojarstva (magistar/magistra inženjer/inženjerka strojarstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Embargoed access; Embargo expiration date: 2028-03-29
• Created on: 2023-03-28 11:47:02