Integral abutment bridges – continuum modelling of soil-structure interaction using finite element analysis with interface elements.

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dc.contributor.advisorVan Zijl, Gideon P. A. G.en_ZA
dc.contributor.advisorFataar, Humairaen_ZA
dc.contributor.authorDreyer, Tashreeqen_ZA
dc.contributor.otherStellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.en_ZA
dc.date.accessioned2024-02-15T13:06:49Zen_ZA
dc.date.accessioned2024-04-27T00:58:14Zen_ZA
dc.date.available2024-02-15T13:06:49Zen_ZA
dc.date.available2024-04-27T00:58:14Zen_ZA
dc.date.issued2024-02en_ZA
dc.descriptionThesis (MEng)--Stellenbosch University, 2024.en_ZA
dc.description.abstractENGLISH ABSTRACT: This thesis presents a computational study on the soil-structure interaction (SSI) behaviour stemming from cyclic thermal-induced movements of integral abutment bridges (IABs) using finite-element engineering software DIANA-FEA. An existing IAB, the Van Zylspruit Bridge in South Africa, is used as a template for the modelling presented in this study, with instrumented earth pressure and abutment displacement readings serving as validation of the models. The abutment-backfill section of the bridge is considered for the SSI modelling using continuum element methodology. The hardening soil model (HSM or HS model) is a numerical soil model that approximates real soil behaviour, including densification due to plastic deformation, stress-dependent stiffness, plastic straining (or yielding) in primary compression and deviatoric loading, isotropic hardening, and dilation. Soil failure is governed by a modified Mohr-Coulomb criterion in this model. The HS model is used to model the backfill, whereas the concrete and in-situ soil materials are assigned linear elastic models for simplicity. In continuum mechanics, ratcheting is the incremental build-up in pressure due to imposed cyclic loading. Ratcheting is prevalent in the backfills of IABs due to imposed cyclic thermal-induced displacements in the deck which are transferred to the abutments. Models presented in this thesis include interface modelling to allow separation between the integral abutment and retained granular (silica sand) fill to capture ratcheting and settlement behaviour in the backfill. The effective bridge temperature (EBT) with daily and seasonal cycles was measured on site from January 2016 to August 2017. This EBT “double cycle” is used to model imposed deformations on the abutment in order to capture ratcheting behaviour in the backfill. The Van Zylspruit bridge has a buried approach slab with one end fixed to the abutment (as a cantilever member). To evaluate the effect that approach slabs have on SSI behaviour, two models were created: one with an approach slab (Slab model) and the other without (No-Slab model). In the Slab model, interface elements were defined between the edges of the approach slab and the backfill to capture SSI behaviour stemming from the slab’s inclusion. The presence of the slab typically reduced settlements, but the development of a gap beneath the slab that grew with seasonal cycles prompts engineers to exercise caution with cantilevered slab designs. Results from both models showed reasonable agreement with measured data in terms of lateral earth pressure and abutment displacement. Two additional clay materials (one stiff and one soft) are used as alternative fill materials (with HSM parameters) to evaluate their effectiveness as backfill materials for IABs, with and without the approach slab present. The stiff clay was found to behave similarly to granular soil both in terms of stress ratcheting and backfill settlement. The soft clay was found to behave unfavourably, especially with the slab present, causing excessive backfill settlements over three times that of the stiff clay. A parameter study on the Mohr-Coulomb parameters (cohesion, friction angle, and dilatancy angle) of the HS model is conducted on the Slab model with granular fill. The values are modulated in reasonable ranges to provide settlement data on granular soils that might be considered as fill material in South Africa. It was observed that high dilatant granular materials with low friction cause excessive heave at the far end of backfill, in excess of 5mm after 5 cycles of ±5.5 mm abutment displacement amplitude. Low-friction and low-dilatant materials typically behaved unfavourably, with settlements across the backfill reaching 4 mm with the same aforementioned displacement criteria. The findings in this study may be beneficial to the current discourse surrounding IABs in the bridge engineering industry as well as the enhancement of modelling IABs using continuum mechanics methodology.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Hierdie tesis bied 'n berekeningstudie oor die grondstruktuur-interaksie- (GSI)-gedrag wat voortspruit uit sikliese termiese-geïnduseerde bewegings van integrale aanligbrûe (IABs) deur gebruik te maak van eindige-element-ingenieursagteware DIANA-FEA. 'n Bestaande IAB, die Van Zylspruit-brug in Suid-Afrika, word gebruik as 'n sjabloon vir die modellering wat in hierdie studie aangebied word, met geinstrumenteerde aarddruk- en brughoof-verplasingslesings wat as validering van die modelle dien. Die aanlig-terugvul gedeelte van die brug word oorweeg vir die GSI modellering deur gebruik te maak van kontinuum element metodologie. Die verhardingsgrondmodel (VGM- of VG-model) is 'n numeriese grondmodel wat werklike grondgedrag benader, insluitend verdigting as gevolg van plastiese vervorming, spanningsafhanklike styfheid, plastiese vervorming (of opbrengs) in primêre kompressie en afwykende belading, isotropiese verharding, en dilatasie. Grondfaling word in hierdie model deur 'n gewysigde Mohr-Coulomb-kriterium beheer. Die VG-model word gebruik om die opvulling te modelleer, terwyl die beton en in-situ grondmateriaal lineêre elastiese modelle vir eenvoud toegeken word. In kontinuummeganika is ratcheting die inkrementele opbou in druk as gevolg van opgelegde sikliese belading. Ratchetting kom algemeen voor in die opvullings van IAB's as gevolg van opgelegde sikliese termiese-geïnduseerde verplasings in die dek wat na die landings oorgeplaas word. Modelle wat in hierdie tesis aangebied word, sluit koppelvlakmodellering in om skeiding tussen die integrale steunpunt en behoue korrel- (silikasand) vulling moontlik te maak om rateling- en versakkingsgedrag in die opvulling vas te vang. Die effektiewe brugtemperatuur (EBT) met daaglikse en seisoenale siklusse is op die perseel gemeet vanaf Januarie 2016 tot Augustus 2017. Hierdie EBT "dubbelsiklus" word gebruik om opgelegde vervormings op die brughoofte modelleer om ratelgedrag in die opvulling vas te vang. Die Van Zylspruit-brug het 'n begrawe naderingsblad met een punt wat aan die brughoof vasgemaak is (as 'n vrykrag-lid). Om die effek wat benaderingsblaaie op GSI-gedrag het, te evalueer, is twee modelle geskep: een met 'n benaderingsplaat (Blad-model) en die ander sonder (Geen-Blad model). In die Blad-model is koppelvlak-elemente gedefinieer tussen die rande van die aanloopblad en die opvulling om GSI-gedrag wat voortspruit uit die plaat se insluiting vas te vang. Die teenwoordigheid van die plaat het tipies versakkings verminder, maar die ontwikkeling van 'n gaping onder die plaat wat met seisoenale siklusse gegroei het, spoor ingenieurs aan om versigtig te wees met vrydraende bladontwerpe. Resultate van beide modelle het redelike ooreenstemming met gemete data in terme van laterale aarddruk en brughoof verplasing getoon. Twee bykomende kleimateriale (een styf en een sag) word as alternatiewe vulmateriaal (met VGM-parameters) gebruik om hul doeltreffendheid as opvulmateriaal vir IAB's te evalueer, met en sonder die aanloopblad teenwoordig. Daar is gevind dat die stywe klei soortgelyk aan korrelgrond gedra het, beide in terme van rateling en versakking. Daar is gevind dat die sagte klei ongunstig optree, veral met die plaat aanwesig, wat oormatige opvul-versakkings meer as drie keer dié van die stywe klei veroorsaak het. 'n Parameterstudie oor die Mohr-Coulomb-parameters (kohesie, wrywingshoek en dilatansiehoek) van die VG-model word uitgevoer op die Blad-model met korrelvul. Die waardes word in redelike reekse gemoduleer om versakkingsdata op korrelgronde te verskaf wat as vulmateriaal in Suid-Afrika beskou kan word. Daar is gevind dat hoë dilatante korrelmateriale met lae wrywing oormatige oplig aan die verste punt van opvulling veroorsaak, meer as 5 mm na 5 siklusse van ±5.5 mm brughoof verplasing amplitude. Lae-wrywing en lae dilaterende materiale het tipies ongunstig gedra, met versakkings oor die opvulling wat 4 mm bereik met dieselfde voorgenoemde verplasingskriteria. Die bevindinge in hierdie studie kan voordelig wees vir die huidige diskoers rondom IAB's in die brugingenieurswese-industrie sowel as die verbetering van modellering van IAB's deur gebruik te maak van kontinuummeganika-metodologie.af_ZA
dc.description.versionMastersen_ZA
dc.format.extentxviii, 131 pages : illustrations.en_ZA
dc.identifier.urihttps://scholar.sun.ac.za/handle/10019.1/130640en_ZA
dc.language.isoen_ZAen_ZA
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subject.lcshBridges -- Abutmentsen_ZA
dc.subject.lcshSoil-structure interactionen_ZA
dc.subject.lcshFinite element methoden_ZA
dc.subject.lcshContinuum mechanicsen_ZA
dc.titleIntegral abutment bridges – continuum modelling of soil-structure interaction using finite element analysis with interface elements.en_ZA
dc.typeThesisen_ZA
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