11 research outputs found
Fluid-Structure Interaction Simulation Of Submerged Floating Tunnels
No full text. A two-dimensional section model of the submerged tunnel problem is analyzed with the multiphysics finite element code SPECTRUM. The model consist of a circular cylinder submerged in sea water and subjected to constant current and regular waves. The waves are modeled by prescribing the velocity profile along the inflow boundary according to linear wave theory and by using free surface boundary conditions on the water surface. Structural boundary conditions are consistent with a global model of the submerged tunnel. A detail description of the computational model and the solution strategy that is used to solve this problem is given. The global response parameters of the cylinder (force coefficients, displacements, velocities and accelerations) obtained from the FSI-simulations are compared with a global nonlinear analysis of the tunnel using simplified models for representing the environmental loads. Knut M. Okstad, Terje Haukas, Svein Remseth and Kjell M. Mathisen 1 INTRODUCTION Be..
Cyclic stress-strain behaviour of alloy AA6060, part I: Uniaxial experiments and modelling
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Reliability analysis of submerged tunnel taught mooring elements subjected to parametric excitation
No full textLinear and Nonlinear Analysis of a High-rise Building Excited by Earthquake: Lineær og ikke-lineær analyse av høyhus utsatt for jordskjelveksitasjon
No full textThe purpose of this thesis is to evaluate the linear and nonlinear response of a high-rise building located in Norway. The Oslo Plaza building, located in Oslo, has been chosen for this purpose. A finite element model of the structure was created in the structural analysis program SAP2000 with emphasis on representing the nonlinear behavior as correctly as possible. Modifications of ground motion data was performed to betterrepresent a typical earthquake in a Norwegian environment, and the seismic response ofthe building was investigated using several different analysis methods.Oslo Plaza was found to behave linearly for earthquakes with an expected return periodof 475 years, while for a 3000-year earthquake major nonlinear effects are expected tooccur especially in the longitudinal direction. Oslo Plaza should however still not collapse during an earthquake of this size, even though it is expected to experience permanent deformations.While dimensioning high-rise buildings for 475-year earthquakes the response spectrummethod described in EC8 was found to be adequate. For most engineering firms this isby far be the easiest method for analysing a high-rise building considering its simplicity and the fact that nonlinear direct integration time history analyses require significantly more computational power and calculation times.An interesting point found during the work with this thesis is that the swimming poollocated in the top-stories of Oslo Plaza might work as a tuned liquid damper during thebuilding s linear seismic response. This damping effect was found to have the potentialto be significant if the dimensions of the swimming pool had been altered by only a fewmeters.Keywords: Ground-motion; High-rise structure; Oslo; Nonlinear; Tuned liquid damper;Dynamic analysi
Linear and Nonlinear Analysis of a High-rise Building Excited by Earthquake : Lineær og ikke-lineær analyse av høyhus utsatt for jordskjelveksitasjon
No full textThe purpose of this thesis is to evaluate the linear and nonlinear response of a high-rise building located in Norway. The Oslo Plaza building, located in Oslo, has been chosen for this purpose. A finite element model of the structure was created in the structural analysis program SAP2000 with emphasis on representing the nonlinear behavior as correctly as possible. Modifications of ground motion data was performed to betterrepresent a typical earthquake in a Norwegian environment, and the seismic response ofthe building was investigated using several different analysis methods.Oslo Plaza was found to behave linearly for earthquakes with an expected return periodof 475 years, while for a 3000-year earthquake major nonlinear effects are expected tooccur especially in the longitudinal direction. Oslo Plaza should however still not collapse during an earthquake of this size, even though it is expected to experience permanent deformations.While dimensioning high-rise buildings for 475-year earthquakes the response spectrummethod described in EC8 was found to be adequate. For most engineering firms this isby far be the easiest method for analysing a high-rise building considering its simplicity and the fact that nonlinear direct integration time history analyses require significantly more computational power and calculation times.An interesting point found during the work with this thesis is that the swimming poollocated in the top-stories of Oslo Plaza might work as a tuned liquid damper during thebuilding’s linear seismic response. This damping effect was found to have the potentialto be significant if the dimensions of the swimming pool had been altered by only a fewmeters.Keywords: Ground-motion; High-rise structure; Oslo; Nonlinear; Tuned liquid damper;Dynamic analysi
Earthquake Response of Suspension Bridge Crossing the Sognefjord
No full textSammendragDenne avhandlingen vurderer den foreslåtte byggingen av en hengebru i et spenn over Sognefjorden i lys av jordskjelv. Den foreslåtte broen har et spenn på 3700 meter og tårnene har en høyde på 455 meter. Om broen blir bygd vil den være den lengste hengebro noensinne bygd med god margin. Dagens regelverk er ikke utviklet for å håndtere konstruksjoner som dette. Det har derfor blitt gjennomført en litteraturstudie for å undersøke teorier utviklet for å beregne jordskjelv respons på lange hengebruer. En metode som ble funnet er «the Pseudo Excitation Method» utviklet for å vurdere seismiske påvirker på hengebroer med lange spenn ved å bruke teori om stokastiske svingninger. Denne metoden har i Kina vært brukt i seismisk utforming av flere lange hengebroer og er i den kinesiske retningslinjen for seismisk utforming av lange broer den foretrukne metoden. Denne metoden er presentert i denne avhandlingen.Modellering av den foreslåtte hengebroen over Sognefjorden ble utført ved bruk av SAP2000. Analyse viste at den første eigenmoden hadde en periode på 36 sekunder og at over 2000 forskjellige moder ble identifisert i systemet. De modale deltagelses faktorer avslører at det er moder så høye som mode 1200 som bidrar vesentlig til responsen i systemet. Før respons analysene for systemet ble utført ble to dempings modeller for systemet vurdert, Rayleigh og hysterese demping. Når frekvens responsen ble beregnet for de 300 første frekvensene og Rayleigh-dempingen ble kontrollert ved den første og hundre naturlige frekvensene viste resultatene at Rayleigh demping ga en respons dobbelt så stor som ved bruk av hysterese demping for flere av frekvenser i området mellom mode 1 og mode 100. Dermed ble hysterese demping brukt i analysene av broen.I Eurocoden, NS-EN 1998-2 er det satt at vind ikke skal tas hensyn til i jordskjelv analyser. Men siden den foreslåtte broen over Sognefjorden er en veldig slank struktur ble demping effekter fra vinden vurdert. Dette ble gjort ved hjelp av kvasi-statiske teori. Siden de aerodynamiske konstantene for denne broen ennå ikke er undersøkt, ble verdiene for Hardangerbrua brukt. Dette ga et grovt estimat av virkningene av den aerodynamiske dempingen, som ga en reduksjon for frekvens responsen på 25 % for den første naturlige frekvens for forskyvning i y-retningen i midt-spennet. Reduksjonen ble mindre for høyere moder, men var fortsatt betydelig.Respons beregning for jordskjelv ble gjennomført i MATLAB, ved å bruke stokastisk vibrasjons teori i frekvensdomenet. Tre analyser ble gjennomført hvor det ble forutsatt stasjonære forhold; seismisk bølge i lengderetningen av broen hvor både «Wave-passage» og «Incoherence» effekter ble tatt hensyn til, seismisk bølge in lengderetning av broen hvor bare «Wave-passage» effekter er tatt hensyn til og seismisk bølge som kommer vinkelrett på broen hvor det derfor ikke er romlige effekter til stede. Resultatene viste at det var betydelige forskjeller responsen fra de tre analysene både i størrelse og form. Maksimal respons ble funnet i z-retning i analysen hvor både «Wave-passage» og «Incoherence» effektene ble vurdert og var 0,81 meter.Som følge av den høye perioden i den første eigenmoden i systemet, er antagelsen om stasjonære forhold ikke gyldig. For å vurdere effekten av ikke-stasjonær forhold er en forenklet metode hvor responsen i hver frihetsgrad er beregnet som for et system av en frihetsgrad. Responsspekter kurvene for de undersøkte punktene viser at dette er et godt estimat siden de er smalbåndet. Ved hjelp av dette ble det vist at standardavviket av responsen for stasjonære forhold bør reduseres betydelig. For den maksimale respons ble reduksjonen omkring 50%
The Development of Submerged Floating Tunnels as an innovative solution for waterway crossings
No full textThe present Thesis is organized in 10 chapters. In particular Chapter 1
gives a general overview of the modern solutions and technologies available
in the field of waterway crossings, introducing briefly the revolutionary
concept of Submerged Floating Tunnel.
Chapter 2 provides a deeper insight into the main characteristics of this
innovative structural solution for waterway crossings: first its structural
features are described and the relevant loading conditions discussed,
subsequently the main advantages of the SFT with respect to the traditional
crossing solutions, such as the Cable Supported Bridges and the Underground
and Immersed Tunnel are described.
Chapter 3 traces the history of the SFT, starting from its first proposal
made in 1969 for the Messina Strait crossing, describing all the feasibility
studies and preliminary designs developed all over the world in the following
years. This Chapter is concluded by a description of the Sino-Italian
cooperation programmes, involving among the other partners the University
of Naples “Federico II”, which led to a feasibility study relative to the
crossing of the Jintang Strait (P.R. of China) with a SFT and to the complete
design of the first SFT full-scale prototype, planned to be realized in the
forthcoming years in the Qiandao Lake (P.R. of China). A potential SFT
crossing in the Pulau Seribu Archipelago (Indonesia), preliminary studied in
the last years by the research team headed by Prof. Mazzolani, is also briefly
illustrated.
Chapter 4 explains in the detail of the various aspects faced in the design of
the Archimedes Bridge prototype. The features of the selected location and the
structural scheme are illustrated. The structural analyses aimed at
investigating the prototype behaviour under the environmental loads are
discussed. The conception and the design of the constructional details are
presented. Finally, the fabrication and erection procedures are briefly
described.
Chapter 5 provides a description of the structural models which can be used
to analyse the SFT structural behaviour: the beam on elastic foundation, which
2 Outline of the Thesis
can be used in the preliminary phase of the design, and a SFT Finite Element
Model.
Chapters 6 and 7 are devoted to the study of the response of the SFT to the
main environmental loads to which is subjected: the hydrodynamic actions
due to the presence of waves and currents and the earthquakes. Numerical
analyses are carried out with the Finite Element analyses aimed at the
understanding of the SFT structural behaviour and at the definition of the
optimal structural configurations.
In Chapter 8 potential SFT solutions developed for the Messina Strait and
Gibraltar Strait crossings are illustrated and a technical-economical
comparison with the Suspension Bridges designed for the same locations is
made.
Chapter 8 describes a simple procedure for a quick comparison of the SFT
and CSIB solutions with the Cable Supported Bridges one, providing useful
curves highlighting the conditions under which the former ones are more
competitive than the latter ones.
Finally, in Chapter 9 the future steps and challenges to be faced in the
development of Submerged Floating Tunnel are presented. An alternative
typology of floating tunnel is introduced too: the Cable Supported Immersed
Inversed Bridge (CSIB), which is conceived as a combination of the
submerged floating bridge concept with the cable system configurations and
features several advantages also with respect to the “traditional” SFT solution
