Finite element analyses of FRP-strengthened concrete beams with corroded reinforcement

Existing deteriorated reinforced concrete (RC) structures need strengthening to extend service life. Fibre reinforced polymer (FRP) has been widely used to strengthen sound structures, but its application on damaged concrete structures still needs to be investigated. This paper presents non-linear finite element analyses conducted to assess the flexural behaviour of corrosion-damaged RC beams strengthened with externally bonded FRP. Beams in four different categories were analysed: a reference beam, a corroded but non-strengthened beam, and corroded beams strengthened with glass FRP (GFRP) and carbon FRP (CFRP) respectively. Furthermore, the strengthened beams were modelled with different modelling choices to investigate the effectiveness of FRP applied to the beam soffit and as U-jackets. Pre-loading and corrosion-induced cracks were incorporated by reducing the tensile strength of concrete elements at crack locations. Average and pitting corrosion were incorporated by reducing the cross-sectional area of the reinforcement corresponding to the measured corrosion levels. Interface elements were used to simulate the bond between FRP and concrete. The modelling methods were validated against experimental results. It was found that modelling of pitting corrosion, especially the location of pits, lengths and number of pits considered, were influential in predicting the load and deformation capacity of beams. A CFRP plate at the beam soffit, combined with inclined U-jackets at its ends of the CFRP plate provided sufficient flexural strengthening. Thus, intermediate U-jackets did not further increase the load-bearing capacity for the studied beam geometry and corrosion damages. However, with a GFRP sheet at the beam soffit, both inclined and intermediate U-jackets were needed to provide full utilisation of the GFRP sheet for the studied beam geometry. In further studies of the effectiveness of the strengthening methods, it is recommended to investigate beams of varying dimensions, corrosion patterns and levels, and FRP spacing and dimensions

Carbon footprint calculation of floor structures

This thesis is written as the concluding part of the program Bachelor of Science in Building Engineering.   The report details the climate impact of three different types of floor structures in the form of carbon dioxide. A concrete slab, a light weight floor structure and a timber floor cassette. The floor structures build-up and the various constituent materials are studied and then designed with the goal to provide as low of a carbon footprint as possible. The climate impact is calculated based only on the production and extraction of the materials to the respective floors.   A central part of this work was to study how the climate impact of a concrete slab changes depending on the thickness of the slab. This due to how the reinforcement relates to the slab thickness. The calculations show that the concrete slabs should be designed as thin as possible to provide the lowest carbon footprint. Finally the calculated climate impact of each floor structure is compared to each other, which shows that the light weight floor structure has the lowest impact on the environment.   The construction industry are most of the time focused on being as effective as possible and do things as always done. This means that new methods of construction are only rarely realized.   Altogether the three floor structures have different advantages and disadvantages. The conclusion from the work is that with more studies that compare various materials, as well as actual results from buildings where new methods proves profitable while sustainable for the future the construction industry will change.Examensarbetet redovisar klimatpåverkan för tre olika typer av bjälklag i form av koldioxidutsläpp. En betongplatta, ett lättbjälklag och ett kassettbjälklag av trä. Bjälklagens uppbyggnad och de olika ingående materialen studeras för att sedan dimensioneras med mål att ge så låg klimatpåverkan som möjligt. Klimatpåverkan beräknas endast utifrån tillverkning och utvinning av materialen till respektive bjälklag. En central del i arbetet var att studera hur klimatpåverkan hos en betongplatta förändras beroende på tjockleken för plattan. Detta tillföljd av hur armeringen förhåller sig till platttjockleken. Beräkningarna visar att betongplattor bör konstrueras så tunna som möjligt för att ge minst koldioxidutsläpp. Med tunnare platta måste dock en alternativ lösning för ljudisolering utredas. Slutligen jämförs den beräknade klimatpåverkan hos vardera bjälklag med varandra vilket visar att lättbjälklaget har den lägsta belastningen på miljön. Byggnadsbranschen vill oftast vara effektiv och göra som de alltid har gjort. Detta gör att nya metoder endast i undantagsfall förverkligas. De olika bjälklagen har alla olika för- och nackdelar. Slutsatsen från arbetet är att med fler studier där man jämför olika material, och med resultat från byggnader där nya metoder visar sig lönsamma och samtidigt hållbara för framtiden kommer byggnadsbranschen förändras