The increased amount of traffic combined with higher traffic loads leads to many existing bridges needing strengthening in the future to ensure their expected lifespan. This means the bridge owners will be focusing more on strengthening projects and smart solutions will be crucial for preserving a healthy bridge stock. When strengthening existing non-composite bridges (with steel girder and concrete deck) one potential method is to achieve composite action by installing shear connectors. The post-installed shear connectors prevent slip between the steel girders and the concrete. The composite action will reduce bending stresses and deflection of the bridge, due to the increase in moment of inertia and relocation of the neutral axis. Different types of shear connectors can be used for achieving composite action and each type of connector has its own installation method. The biggest distinction between the methods is how the connectors gain access to the steel girder for installation and what technique is used when installing them. This thesis presents the theory behind composite action, the current methods used for achieving composite action on existing bridges and to what extent a bridge can be strengthened by composite action. The thesis also provides a status of the existing road bridge stock around the world. The four case studies examined in this thesis have used different post-installed shear connectors to manage different strengthening problems like weight restriction, fatigue life of shear connectors and a unique problem on the Pitsund Bridge where loud bangs appeared from the bridge when truck passed in the morning. For the case study on the Pitsund Bridge an interview was conducted that explains the entire procedure of the project, from the noise problem to how the installation of coiled spring pins was performed. The bridge over Lule River at Akkatsfallen consists of two steel girders and a concrete deck. This bridge is chosen as a real case study to determine to what extent a bridge can increase its capacity by achieving composite action. The calculations are performed in accordance with the Eurocodes on both non- and full-composite action and the result is compared to the other case studies.

Syfte: I Sverige råder det en stor bostadsbrist. En lösning för att skapa nya bostäder i tätbebyggda områden är vertikal förtätning. Detta kan ske via våningspåbyggnad av bostäder på parkeringshus. Denna typ av påbyggnad ställer dock krav på den befintliga byggnaden. Rapportens syfte är att fungera som ett underlag vid projektering av konstruktion, brand och installationer vid framtida projekt av liknande slag. Målet är vidare att analysera och sammanställa olika byggnadstekniska lösningar som används vid våningspåbyggnad av bostäder på parkeringshus. Detta skall besvaras genom följande frågeställningar: Vilka konstruktionstyper tillämpas vid våningspåbyggnad på ett parkeringshus och vilka krav ställer påbyggnaden på den befintliga stommen? Vilka brandkrav ställs på denna typ av våningspåbyggnad och hur uppfylls dessa? Hur förses påbyggnaden med installationer?   Metod: Rapporten bygger på en kvalitativ fallstudie där intervjuer och dokumentanalyser legat till grund för empirin. För att styrka studien med teori har en litteraturstudie genomförts.   Resultat: Resultatet visar att en lätt stomme har använts till samtliga våningspåbyggnader, däremot har valet av stommaterial skiljt sig åt. Kapaciteten på den befintliga byggnadens grund har varit avgörande för om en våningspåbyggnad varit möjlig. Placering av våningspåbyggnaden har berott på om boyta eller antalet parkeringsplatser prioriterats högst. Brandkraven på denna typ av byggnad kan likställas med kraven som ställs på en nybyggnad av bostäder. Detta har inneburit att förändringar på de befintliga parkeringshusen varit nödvändiga för att uppfylla kraven. Nya installationsschakt har placerats både in- och utvändigt av den befintliga byggnaden.   Konsekvenser: De slutsatser och rekommendationer, utifrån rapportens innehåll, består främst av vikten i att göra en noggrann inventering av den befintliga byggnaden. Det handlar om byggnadens kapacitet och vilka eventuella förstärkningsarbeten som krävs innan en våningspåbyggnad.   Begränsningar: Studien avgränsar sig från byggnadstekniska beräkningar och ekonomiska kalkyler. Arbetet har begränsats utifrån en viss mängd ord och tidsram, utan dessa hade möjligheten funnits att göra en mer djupgående analys av studiens referensobjekt. Detta genom att intervjua ytterligare aktörer inom fler konsultområden för de valda referensobjekten. / Purpose: In Sweden, there is a shortage of housing and a solution for creating new housing in urban areas is vertical densification. Vertical densification can be done by adding floors of housing on top of existing parking garages. This type of extension sets demands on the existing building. The purpose of this thesis is to serve as a basis for the planning of construction, fire requirements and installations for future similar projects. The goal is furthermore to analyze and compile various building-technical solutions that are used when floors of housing are built on top of existing parking garages. The goal is answered by the following questions: Which types of construction are used for additional floors of housing on top of parking garages and what requirements does the extension have on the existing building? What fire requirements are imposed on this type of extension and how are they fulfilled? How are the additional floors of housing provided with installations?   Method: The report is based on a qualitative case study in which interviews and document analysis formed the basis of empirical data. To confirm the study with theory, a literature study has been conducted. Findings: The result shows that a light framework has been used for additional floors of housing, however, the choice of framework material has been different. The capacity of the existing building's foundation has been vital for whether an extension with housing has been possible. Placement of the extension has been due to whether the living space or the number of parking spaces is given as the highest priority. The fire requirements for this type of building can be equated with the requirements imposed on a new building of housing. This has meant that changes to the existing parking garages have been necessary to meet the requirements. New shafts for installations have been placed on both inside and outside of the existing building. Implications: The conclusions and recommendations, based on the content of the thesis, consist primarily of the importance of making an accurate inventory. It’s about the existing building's capacity and what possible reinforcement work it requires before an extension with housing. Limitations: The study delimits itself from construction engineering calculations and economic calculations. The work has been limited based on a variety of words and timeframe, without these it would be possible to make a more in-depth analysis of the study's reference objects. This would be done through interviewing more actors from additional consulting areas for the selected reference objects.