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Climate Change and Effects of Scour on the Soil Structure Interaction of Foundation
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Engineering and Bridges.
2020 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

As human induced climate change continues due to greenhouse gas emission, radicalchanges in local climate and extreme weathering is increasing rapidly. Climate changeis impacting the environment and the human systems, which is evident through reportspublished by IPCC. The built environment is the domain where human interaction andactivity occurs, and it is important to protect it for a better living from the vulnerabilitiesof climate change. Bridge form a key component of the built environment andthey are vulnerable to these changes, so identification and monitoring of bridges are ofutmost importance for the proper functioning of the transport network. Scour is regardedas a major threat to bridges and it is the removal of material around the bridgefoundation by the erosive action of water.Detecting scour by observing changes in the dynamic properties of bridges is becomingmore feasible due to the development in measuring devices and this thesis will exploresuch possibilities by analysing the dynamic soil structure interaction (SSI) of foundation.To begin, a finite element model is developed to simulate SSI by using perfectly matchedlayers (PML) as absorbing mediums. A verification study is performed on the modelby comparing the computed impedance functions with an existing solution to ensurethe results produced reflects the underlying mathematics. Then a shallow foundationof rectangular shape is modelled, and scour is mimicked by removing contact with soilin steps and the impedance functions are computed.In addition to SSI, a decrease in the buckling capacity of piles due to an increase in scourdepth is also explored for deep foundations. A finite element model is created wherethe soil is modelled as nonlinear springs and the pile is modelled as beam elements.A validation study is performed against experimental results to ensure reliable resultsare produced and then a commonly available pile type is studied for buckling capacityreduction due to scour. Springs are removed in steps to represent scour action andbuckling capacity is calculated for each step.By using PML it was possible to truncate the domain size to the region of interestdecreasing the computational time and propagating waves were absorbed without artifacts.The results for shallow foundation showed a decrease in damping and stiffnesscoefficients with an increase in scour depth. The impedance functions were coupledwith superstructure and by performing eigenvalue analysis the natural frequencies ofthe bridges decreased showing considerable potential for the detection of scour. Thebuckling capacity of the pile also reduced reasonably for increasing scour depth signifyingthe importance of scour protection methods collectively. It is emphasized basedon the observed changes in climate, that consideration of climate change factors is veryimportant in the design and maintenance of infrastructure.

Place, publisher, year, edition, pages
2020.
Series
TRITA-ABE-MBT ; 2015
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-268644OAI: oai:DiVA.org:kth-268644DiVA, id: diva2:1394488
Available from: 2020-02-19 Created: 2020-02-19

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