Patch repairs are sometimes considered to be capable of contributing to the resisting of externally applied load when the repairs are applied to deteriorated concrete structural members, particularly when the repair is subj ected to compression. However, it is generally known that many patch repair materials shrink and creep significantly relative to the concrete substrate. This thesis presents an experimental and numerical study of the contribution of patch repairs to load carrying in reinforced concrete columns, its quantification and the effect of shrinkage and creep. Twelve reinforced concrete columns were cast with a cavity located halfway up one side of the column. Two control columns were cast without a cavity. The parameters varied in the experimental testing were the depth of the repair cavity, type of repair material (one polymeric and the other polymer-modified), and whether the repaired columns were monitored under load or without being loaded. Test results prior to repair indicate that the loss of concrete from the column induces bending in the loaded column. Both the polymer-modified and polymeric mortar contributed to the column's resistance of the applied load in the short term, but in the long term the contribution of the polymer-modified mortar decreased substantially while that of the polymeric mortar was sustained. Repaired columns which were monitored with no load showed that shrinkage of the polymer-modified mortar can induce bending in the repaired column; this bending increased with cavity depth. Bending strain distributions in the repaired area are close to a straight line, particularly for columns monitored under load. The finite element numerical simulations showed good qualitative agreement with the test results. The analyses also indicated that strain distributions outside but close to the repaired area are nonlinear. However, predictions of the engineer's theory of bending showed favourable quantitative agreement with the finite element analyses.

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One of the great challenges to increasing the use of wind generation is the need to ensure generation adequacy. In this dissertation, we address that need by investigating and assessing the planning and operational generation adequacy of power systems with significant wind generation. At the onset of this dissertation, key metrics are presented for determining a power system’s generation adequacy assessment based on loss-of-load analytical methods. With these key metrics understood, a detailed methodology is put forward on how to integrate wind plants in the assessment’s framework. Then, through the examination of a case study, we demonstrate that wind generation does contribute capacity to the system generation adequacy. Indeed, results indicates that at wind penetration levels of less than 5%, a wind plant’s reliability impact is comparable to an energy equivalent conventional unit. We then show how to quantify a wind plant’s capacity contribution by using the effective load carrying capability metric (ELCC), providing a detailed description of how to implement this metric in the context of wind generation. However, as certain computational setbacks are inherent to the metric, a novel noniterative approximation is proposed and applied to various case studies. The accuracy of the proposed approximation is evaluated in a comparative study by contrasting the resulting estimates to conventionally-computed ELCC values and the wind plant’s capacity factor. The non-iterative method is shown to yield accurate ELCC estimates with relative errors averaging around 2%. Case study findings also suggest the importance of period-specific ELCC calculations to better evaluate the variable capacity contribution of wind plants. Even when considering a well-planned system in which wind generation has been appropriately integrated in the adequacy assessment, wind plants do create significant challenges in maintaining generation adequacy on an operational level. To address these challenges, a novel operational reliability assessment tool is proposed to quantitatively evaluate the system’s operational generation adequacy given potential generator forced outages, load and wind power forecasts, and forecasting deviations. / text

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The Swedish government is planning to increase the maximum vehicle gross load regulations on parts of the national roads from the present 60 t, for the load carrying capacity class BK1, to 74 t, for the proposed new load carrying capacity class BK4. The initial implementation of the new load carrying capacity class for 74 t vehicles will only regard major highways and important roads, however, at a later stage the plan is to implement the new BK4 class on the full current BK1 road network. The biggest obstacle which arises when implementing these increased traffic loads is insufficient load carrying capacity for the bridges on the road network.   Thus, the objective of this thesis is to examine and analyze the effects of the increased traffic loads on Swedish road bridges. In order to identify the structural effects of the load increase, and draw general conclusions regarding the effects on the bridge network as a whole, a case study with load carrying capacity calculations is carried out on a two-span concrete slab fram bridge at a highway interchange in Värö in western Sweden. The bridge is classified as critical by Trafikverket. The load carrying capacity calculation is carried out using the Swedish standards, in which maximum load values for the axle load, A, and the bogie load, B, is calculated.   The load effects acting on the bridge are calculated using the finite element software BRIGADE/Standard, with input traffic A and B loads amounting to 12 t and 21 t respectively for the new BK4 class and to 12 t and 18 t respectively for class BK1. In addition to the load carrying capacity calculations with BK4 traffic loads, a comparison is carried out between the results obtained when using the axle- and bogie loads from the BK1 versus the BK4 load carrying capacity class in the load carrying capacity calculations.   The load carrying capacity calculations performed on the studied bridge shows that the capacity of the bridge, both in regards to moment and shear force, is insufficient to meet the new, increased, BK4 A/B – requirements. The critical A/B – values for the whole bridge are 17 t and 18 t respectively, to be compared with the required 12- and 21 t limit for the new BK4 load carrying capacity class, thus, making the load carrying capacity of the bridge inadequate. The critical A/B – values appear for the longitudinal shear force load case at the point where the shear force reinforcement over the column support ends. Moreover, the difference between the results obtained when using the BK1 versus the BK4 traffic loads in the calculations were found to be negligible.   Due to the differing properties and characteristics of each individual bridge on the Swedish road network it is difficult to make general statements regarding the effects of the increased traffic loads on the bridge network as a whole. Specific load carrying capacity calculations will need to be performed on each individual bridge in order to evaluate its capability to withstand the new increased BK4 traffic load. However, capacity calculations regarding the BK1 load carrying capacity class can, with sufficient accuracy, be used to evaluate the capability of a bridge to withstand the increased traffic loads in the BK4 load carrying capacity class, thus, making it easier to evaluate the strengthening needs for the bridge network as a whole. / Sveriges regering planerar en utökning av den maximalt tillåtna bruttovikten för fordon på delar av det allmänna vägnätet från den nuvarande begränsningen på 60 t, för bärighetsklass BK1, till 74 t, för den nya föreslagna bärighetsklassen BK4. I det första skedet kommer den nya bärighetsklassen, för fordon med bruttovikt upp till 74 t, bara att implementeras på stora motorvägar och andra ur transportsynpunkt viktiga vägar, men, i ett senare skede finns också planer på att implementera den nya bärighetsklassen, BK4, på hela det nuvarande BK1 vägnätet. Det största problemet som förväntas uppkomma under införandet av de nya, ökade, trafiklasterna är otillräcklig bärighet på vägnätets broar.   Således är målet med denna uppsats att undersöka och analysera effekterna av dessa ökade trafiklaster för broar på det Svenska vägnätet. För att identifiera effekterna, och dra generella slutsatser, gällande denna ökade trafiklast för broarna på det Svenska vägnätet i sin helhet kommer en fallstudie med bärighetsberäkningar utföras på en plattrambro vid trafikplats Värö - en bro som Trafikverket bedömer som kritisk. Bärighetsberäkningen utförs enligt svenska standarder, där maximala tillåtna värden på axellasten, A, och bogielasten, B, beräknas.   Lasteffekterna som verkar på bron beräknas med hjälp finita element programvaran BRIGADE/Standard med trafiklaster, A och B, som uppgår till 12  respektive 21 t för den nya BK4 bärighetsklassen och 12 respektive 18 t för bärighetsklass BK1. Som tillägg till bärighetsberäkningarna med BK4 laster utförs också en jämförelse av resultaten som uppkommer när axel- och bogielasterna från BK1 respektive BK4 används i beräkningarna.    Bärighetsberäkningarna på den studerade bron visar att brons kapacitet, både gällande moment och tvärkraft, är otillräcklig när den belastas med de ökade BK4 trafiklasterna. De kritiska A- och B- värdena för bron är 17 respektive 18 t, värden som skall jämföras med kraven på 12 respektive 21 t för den nya bärighetsklassen BK4 – därmed är brons bärighet otillräcklig. De kritiska A- och B-värdena för bron uppkommer för lastfallet med longitudinell tvärkraft vid punkten där tvärkraftsarmeringen över mittstödet slutar verka. Jämförelsen mellan beräkningsresultaten som uppkom med trafiklaster enligt BK1 respektive BK4 visade att skillnaden mellan beräkningsresultaten var försumbar.   På grund av de varierande egenskaperna hos varje enskild bro på det Svenska vägnätet är det svårt att dra generella slutsatser gällande effekterna av lastökningen för vägnätet som helhet. Specifika bärighetsberäkningar måste utföras på varje individuell bro för att kunna utvärdera dess kapacitet att klara av de nya, ökade, BK4 trafiklasterna. Emellertid kan bärighetsberäkningar som beträffar bärighetsklassen BK1, med tillräcklig tillförlitlighet, användas för att bedöma en bros möjlighet att motstå de ökade trafiklasterna i den nya bärighetsklassen BK4, vilket förenklar utvärderingen av vilka broar som kräver förstärkning.

Alkali-kiselsyrareaktionen (AKR) är en kemisk reaktion som medför att spänningar uppstår i betongen då den bildade silikatgelen expanderar. Reaktionen kräver tillräcklig hög alkalihalt, reaktiv ballast samt vatten. På grund av de AKR-inducerade spänningarna är det av intresse att få kunskap i hur reaktionen påverkar betongens böjmomentkapacitet, förankring samt skjuvnings- och genomstansningskapacitet. För att besvara frågeställningen har därför en omfattande litteraturinventering tillsammans med tre kompletterande intervjuer utförts. Resultat som har erhållits, påvisar att två huvudsakliga effekter fås av AKR. Utöver en reducerad hållfasthet på grund av expansioner och sprickbildningar, erhålls även en gynnsam förspänningseffekt när armering motverkar expansioner. Med hänsyn till dessa huvudeffekter påverkas betongs bärighet i olika stor utsträckning beroende på expansionens storlek samt armeringens läge och typ i tvärsnittet. Resultaten tyder på att draghållfastheten reduceras till 40 % medan tryckhållfastheten reduceras till 60 % vid 5 mm/m expansion. För böjkapaciteten har ingen större reduktion uppmäts då expansioner understiger 6 mm/m. Emellertid har en reduktion på 25 % observerats vid expansioner större än 6 mm/m. Skjuvkapaciteten i AKR-skadad betong beror till stor del av byglars närvaro samt expansionens omfattning. I balkar utan byglar reduceras skjuvkapaciteten med 15-25 % för slät armering och 20-30 % för räfflad armering. Genomstansningskapaciteten i ett dubbelarmerat betongtvärsnitt reduceras obetydande till dess att expansionen överstiger 6 mm/m varpå en mer påtaglig reduktion fås. Hållfastheten för vidhäftning minskar med ca 40 % då täckande betongskikt understiger 1.5Æ och/eller att inga byglar är närvarande. Om byglar är närvarande samt om täckande betongskikt överstiger 4Æ visas inga tecken på försämrad vidhäftningshållfasthet. Utöver en minskad bärighet, öppnar AKR upp betong och skapar gynnsammare förutsättningar för rost-och frostangrepp. / Alkali-silica reaction (ASR) is a chemical reaction that causes stresses in concrete when the produced alkali silica gel expands. The reaction requires sufficiently high alkali content, reactive aggregates and water. Due to ASR-induced stresses it is of interest to gain insight in how ASR affects the concrete’s bending capacity, anchoring together with shear- and punching shear capacity. An extensive literature review was therefore carried out together with three complementary interviews in order to answer the question at issue. Obtained results show two main effects of ASR. In addition to a reduced strength because of cracking and expansion, an advantageous pre-stress is gained due to restraint to expansion. Thus, the load-carrying capacity of concrete is affected in various extents depending on the size of expansion and location and type of the reinforcement. The results indicate that the tensile strength is reduced to 40 % whereas the compressive strength is reduced to 60 % at 5 mm/m expansions. While expansions lesser than 6 mm/m has not shown a greater reduction of the bending capacity, a reduction of 25 % has been observed in concrete with expansions greater than 6 mm/m. The shear capacity of an ASR-affected concrete structure depends mainly on the presence of links and the extent of expansions. In beams without links, shear capacity is reduced to 15-25 % for smooth bars and 20-30 % for ribbed bars. The punching strength of a concrete structure reinforced in both faces is not reduced until expansions exceed 6 mm/m, whereas a more significant reduction is obtained. The bond strength decreases by about 40 % if the concrete cover is less than 1.5 Æ and/or if no links are present. Meanwhile if links are present and if concrete cover is more than 4Æ, no signs of reduction of the bond strength has been observed. Additionally, to a reduced load-carrying capacity, ASR also opens up the concrete and consequently creates beneficial circumstances for corrosion and frost attacks.

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