Performance of bridges during previous earthquakes has demonstrated that many structural failures could be attributed to seismic deficiencies in bridge columns. Lack of transverse reinforcement and inadequate splicing of longitudinal reinforcement in potential plastic hinge regions of columns constitute primary reasons for their poor performance. A number of column retrofit techniques have been developed and tested in the past. These techniques include steel jacketing, reinforced concrete jacketing and use of transverse prestressing (RetroBelt) for concrete confinement, shear strengthening and splice clamping. A new retrofit technique, involving fibre reinforced polymer (FRP) jacketing has emerged as a convenient and structurally sound alternative with improved durability. The new technique, although received acceptance in the construction industry, needs to be fully developed as a viable seismic retrofit methodology, supported by reliable design and construction procedures. The successful application of externally applied FRP jackets to existing columns, coupled with deteriorating bridge infrastructure, raised the possibility of using FRP reinforcement for new construction. Stay-in-place formwork, in the form of FRP tubes are being researched for its feasibility. The FRP stay-in-place tubes offer ease in construction, convenient formwork, and when left in place, the protection of concrete against environmental effects, including the protection of steel reinforcement against corrosion, while also serving as column transverse reinforcement. Combined experimental and analytical research was conducted in the current project to i) improve the performance of FRP column jacketing for existing bridge columns, and ii) to develop FRP stay-in-place formwork for new bridge columns. The experimental phase consisted of design, construction and testing of 7 full-scale reinforced concrete bridge columns under simulated seismic loading. The columns represented both existing seismically deficient bridge columns, and new columns in stay-in-place formwork. The existing columns were deficient in either shear, or flexure, where the flexural deficiencies stemmed from lack of concrete confinement and/or use of inadequately spliced longitudinal reinforcement. The test parameters included cross-sectional shape (circular or square), reinforcement splicing, column shear span for flexure and shear-dominant behaviour, FRP jacket thickness, as well as use of FRP tubes as stay-in-place formwork, with or without internally embedded FRP crossties. The columns were subjected to a constant axial compression and incrementally increasing inelastic deformation reversals. The results, presented and discussed in this thesis, indicate that the FRP retrofit methodology provides significant confinement to circular and square columns, improving column ductility substantially. The FRP jack also improved diagonal tension capacity of columns, changing brittle shear-dominant column behavior to ductile flexure dominant response. The jackets, when the transverse strains are controlled, are able to improve performance of inadequately spliced circular columns, while remain somewhat ineffective in improving the performance of spliced square columns. FRP stay-in-place formwork provides excellent ductility to circular and square columns in new concrete columns, offering tremendous potential for use in practice. The analytical phase of the project demonstrates that the current analytical techniques for column analysis can be used for columns with external FRP reinforcement, provided that appropriate material models are used for confined concrete, FRP composites and reinforcement steel. Plastic analysis for flexure, starting with sectional moment-curvature analysis and continuing into member analysis incorporating the formation of plastic hinging, provide excellent predictions of inelastic force-deformation envelopes of recorded hysteretic behaviour. A displacement based design procedure adapted to FRP jacketed columns, as well as columns in FRP stay-in-place formwork provide a reliable design procedure for both retrofitting existing columns and designing new FRP reinforced concrete columns.

Denna studie är en del i projektet Framtida kompetensförsörjning och arbetslivets längd inom Västerbottens läns landsting. Studien har syftet att kvalitativt utforska resonemang rörande pensionsintentioner hos äldre medarbetare inom landstinget, med ett specifikt fokus på påverkande faktorer inom arbetslivet. Sju semistrukturerade intervjuer har utförts med respondenter från olika yrkeskategorier. Vid analysen av intervjuerna framkom likheter i respondenternas pensionsresonemang, trots deras skilda livssituationer och tänkta pensionsåldrar. Den mest framträdande likheten var den funna kärnkategorin: möjligheten att göra ett bra arbete. Den framställdes av respondenterna som en avgörande del i hur arbetssituationen påverkade deras pensionsintentioner. Att uppleva det som möjligt att fortsätta utföra sina arbetsuppgifter på ett för en själv fullgott vis verkade vara mycket viktigt för deras fortsatta arbetsdeltagande. Faktorer i arbetet som försvårar det verkar också kunna bidra med tidigare pensionsintentioner. Samtidigt som faktorer vilka underlättar för att fortsätta göra ett bra arbete verkar bidra med senare pensionsintentioner. Kärnkategorin kan också knytas till den tänkta pensionstidpunkten. För respondenterna vekar det vara mycket viktigt att inte göra en svag arbetsinsats, varpå de överlag resonerar att arbetslivet bör avslutas innan en tänkt oförmåga manifesteras.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2005. / Härtill 4 uppsatser.

Lic.-avh. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 2 uppsatser.

Dissertation (Ph.D.) -- University of Texas Southwestern Medical Center at Dallas, 2008. / Vita. Bibliography: p. 154-178.

Thesis (M.H.A.)--University of Michigan, 1975.

Thesis (M.S.)--University of Michigan, 1969.

Thesis (M.H.A.)--University of Michigan, 1975.

Thesis (M.S.)--University of Michigan, 1993.

Thesis (M.S.)--University of Michigan, 1993.