Contracts for the operation and maintenance of roads and streets are today characterized by short-term perspectives and a low rate of development. One reason for this is that the client placing an order, within the framework of traditional contract procedures, specifies in detail what shall be done and sometimes even orders a certain type of machinery and equipment. The contractors are not made aware of the longterm quality ambitions of the client with respect to traffic safety and ease of flow. A performance contract means that the client, instead of presenting technical solutions, makes measurable functional demands with regard to the finished product. The demand is for example made that the road surface shall have a certain smoothness and a certain friction The functional requirements are formulated so that they have a direct relevance for the safety and flow of traffic. The functional requirements should be divided into an absolutely lowest permissible level (acute level) and a target level. The target level shall be maintained both as an average functional level during the contract period and when the contract is completed. Functionally directed road maintenance should include measures to reduce traffic disturbances to a minimum. It should also be required of the contractor that he reports planned measures to the relevant road-user information centres. Performance contracts radically change the roles of both the client and the contractor. The client's efforts are concentrated on controlling the quality of the final product from a user point of view, while the contractor takes over many of the traditional roles of the client such as planning, projecting, choice of technical solutions, choice of material and duty activities. Direct contact with road-users and residents will also be included in the tasks of the contractor. The advantages of a performance contract are the functional expectations of the users become the guiding star for the contractor it stimulates the development of creative solutions by the contractor the responsibility boundary between client and contractor becomes "sharp" Trials with performance contracts for operation and maintenance have been carried out in both Sweden and the USA. / Godkänd; 1993; 20070426 (ysko)

Probabilistic methods are presented for the assessment of bridges. Load carrying capacity calculations and evaluations of strengthening methods are carried out for three road bridges in northern Sweden: 1) The E4-bridge over Pite River - A four span steel beam bridge with a concrete deck built in 1969. The capacity of the edge beams are evaluated with use of calculations and monitoring results. Strengthening measures are discussed and recommended. 2) Bridge over Kuivajärvi - A one span concrete slab-frame bridge built in 1954. The supports have moved transversally towards each other causing cracking in the deck. Strains and deflections are monitored and the capacity is evaluated. 3) Bridge over Åhedån - A one span concrete beam-frame bridge built in 1934. The bridge was to be widened and the load carrying capacity of an increased cross section is studied. Monitoring and testing of material properties have given valuable information of the real behaviour of the studied bridges. Bayesian updating of original data has been shown to be very useful. Further research work is needed regarding the uncertainty coefficients for the studied models and parameters in order to fully take advantage of the possibilities to assess existing bridges with probabilistic methods. / Godkänd; 2008; 20080512 (ysko)

This thesis aims to answer questions regarding material and fatigue properties of bridges built between the end of the 19th century to 1940's. Regarding material properties the study involves the creation of a data base consisting of material properties of bridges. The establishment of a data base was done by retrieval of test certificates from material investigations conducted on existing bridges. The bridges in question were road and railway bridges produced before 1940's. The aim of the investigation was to determine the material properties of bridges in the specified interval and compare these with properties in evaluation codes. From the evaluation of the data base it became apparent that the yield strength of the existing bridges was higher than specified in the evaluations codes of Sweden and Denmark. Also a big divergence regarding the toughness properties were established for the investigated bridges. Regarding fatigue endurance, a literature survey of fatigue tests performed on riveted structures were conducted. The survey concerned both full scale structures retrieved from bridges taken out of service and small scale tests. The objective was to investigate the fatigue resistance of riveted structures. Factors as hole preparation, corrosion, clamping force and influence from materials properties on the fatigue performance was also inquired. In the evaluation of the fatigue tests it was concluded that fatigue endurance of riveted assembled girders was best described by the detail category C=63. / Godkänd; 2006; 20070109 (haneit)

Asphalt compaction is one of the most important phases of road construction, being the decisive phase when the structure of the asphalt pavement layer is formed. In spite of its importance, the knowledge about this construction phase is still based on empirical and technological background and therefore surprisingly limited. This lack of knowledge is also due to the fact that the existing laboratory scale compaction devices for mix design are not fully capable of simulating the field compaction. The simulation of asphalt compaction in the laboratory is normally focused on the vertical rearrangements of asphalt particles whereas the flow behavior of these particles in other directions is mostly neglected. However, existing literature suggests that the neglected flow is one of the most important factors for the quality of the road construction, particularly in special cases such as asphalt joints. Therefore, building up a better understanding of the flow behavior of asphalt mixtures subjected to compaction loads is needed for improving the quality of the pavements. In this study, a new test setup, the so called Compaction Flow Test (CFT), was developed to simulate the flow behavior of asphalt mixtures at early stages of compaction. In the first step, feasibility tests were performed, substituting asphalt mixtures by model materials with simple geometries and less complex properties. X-ray Computed Tomography (CT) was utilized for capturing 2D radiography images of the flow patterns in the model material during the test. Results of the CFT showed the capability of the new test setup to clearly distinguish between model mixtures with different characteristics. Hence, in the next step, the CFT was applied to real asphalt mixtures and the obtained results were found to support the findings of the feasibility tests with the model materials. The results from the feasibility tests encouraged examining the possible use of an ultrasonic sensor as alternative to the complex and costly X-ray imaging for flow measurements during the CFT. Hence, the CFT was used along with a distance measuring ultrasonic sensor for testing asphalt mixtures with different characteristics. The test results confirmed that an ultrasonic sensor could be effective for capturing the differences of the flow behavior of asphalt mixtures tested by the CFT.  In addition, a parametric study with the X-ray setup was carried out to examine the capability of the CFT in reflecting the possible changes of the flow behavior in asphalt mixtures due to the change of construction parameters such as lift thickness, bottom roughness and compaction modes. The results obtained also confirmed the capability of the CFT in showing the possible differences in the flow behavior of the mixtures under the chosen conditions. The encouraging results suggested that the CFT may have potential to become a simple but effective tool for assessing compactability of the mixtures on-site, right after production in an asphalt plant or before placing the mixture on the road. Hence, discrete element method (DEM) was utilized to understand both the influence of selected boundaries of the CFT and the effect of its design on the results. As one specific example of application, an investigation was carried out using the CFT to find the most suitable tracking method for flow measurements in the field. Based on the literature review and feasibility tests, a tracking method with the highest potential for conducting flow measurements during field compaction was introduced. X-ray radiography confirmed the validity of the results obtained with the suggested method. The overall results obtained from this study suggest that the recommended CFT along with the suggested field tracking method may be helpful in building up a comprehensive basis of knowledge on the flow and compaction behavior of asphalt mixtures thus helping to close the gap between the field and laboratory. / <p>QC 20171214</p>

No description available.

<p>Godkänd; 1995; 20080330 (ysko)</p>

The product model approach for the construction industry is fairly new subject field, especially the implementation of the result in the building process. The aim of the research and the contribution to the goal of better utilize processes is shortly described below. Limited to concrete building constructions, including both in-situ (cast in place) and precast (prefab) structures. Focus on product data models and us of product models. Standardized as well as own developed product data models are included. Consist of studied and evaluation of international standards, the applicable to the construction industry and the possibilities to develop implementations. Developing of effective workprocesses for structural designers is essential. This even includes relations to the production phase. Use commercial software system for demonstrations purposes, by implement new technology in StruSoft existing product assortment. The implementation prototypes give the opportunity to demonstrate the result to the construction industry and to promote a useful debate about working methods. The long-term goal is to give the actors in the structural design process, tools for sharing information and more efficient design methods. This research project includes four sub projects, all with different scope, main goals but the target groups are the same, namely structural designer, the concrete industry and software developer in this domain. / Godkänd; 2003; 20070217 (ysko)

<p>Godkänd; 1992; 20080407 (ysko)</p>

Dagens vägbroar utgörs ofta av samverkanskonstruktioner med bärande huvudbalkar av stål och farbana av betong. Detta sätt att bygga har visat sig vara kostnadseffektivt. På senare tid har det blivit allt viktigare att byggtiden dessutom skall minimeras så långt som möjligt för att på detta sätt minska investeringskostnaden. Dessutom ställs det krav på hög kvalitet och säkerhet. Uppsatsen presenterar en metod som gör det möjligt att uppfylla dessa krav vid byggande av samverkansbroar. Metoden baseras på ett system som har hög prefabriceringsgrad. Förutom stålbalkarna så är även betongfarbanan prefabricerad. Det unika med metoden som beskrivs i denna licentiatuppsats är att fogarna mellan elementen är torra. I stället för att ha en kontinuerlig skarv med genomgående armering så används överlappande betongklackar för att föra över vertikal krafterna mellan elementen som uppstår då ett fordon passerar fogen. Metoden är provad på ett verkligt objekt, en enspanns bro med tryckta fogar. För detta fall föreligger det inte några stora hinder eftersom fogen aldrig kan öppna sig. Om bron däremot utförs som en flerspannsbro kan det uppstå problem över ett innerstöd eftersom fogen då blir dragen och därmed vill öppna sig. För att undersöka hur den beter sig under sådan belastning har det utförts försök vid Testlab vid LTU. Syftet var att undersöka hur mycket fogen öppnar sig i vertikal såväl som horisontell riktning vilket har betydelse för isoleringsskiktet och beläggningen. En annan del av försöket bestod i att undersöka om de skjuvförbindande svetsbultarna skulle utmattas då bron böjer sig över innerstödet till följd av passerande fordon. För att underlätta utvärderingen skapades också en FE-modell där det var möjligt att variera storleken på elementen och se hur detta påverkade resultaten. Ett av syftena med denna modellering var att undersöka hur stor betongbredd som medverkande vid olika förhållanden mellan längd och bredd på elementen. Det har också utförts fältmätningar på den verkliga bron för att se hur stor samverkan som fanns mellan stålet och betongen. Även dessa undersökningar FE modellerades för att underlätta utvärderingen. Dessutom har ett examensarbete löpt under projektets utförande som tittade på de samhällsekonomiska effekterna för detta koncept jämfört med andra mer traditionella metoder. Även effekter som trafikantstörningar vägdes in för att få en så allomfattande jämförelse som möjligt. En litteraturfördjupning har också utförts för att ge en uppfattning om vad som är gjorts runt om i världen på liknade koncept och lite grann om vilken forskning som har utförts av andra. / <p>Godkänd; 2001; 20070313 (ysko)</p>

<p>Godkänd; 1996; 20080417 (ysko)</p>