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Bridge networks are expensive and complex infrastructures and are essential components of today's transportation systems. Despite the advancement in computer aided modeling and increasing the computational power which is increasing the accessibility for developing the fragility curves of bridges, the complexity of the problem and uncertainties involved in fragility analysis of the bridge structures in addition to difficulties in validating the results obtained from the analysis requires precaution in utilization of the results as a decision making tool. The main focus of this research is to address, study and treatment of uncertainties incorporated in various steps of performance based assessments (PBA) of the bridge structures. In this research the uncertainties is divided into three main categories. First, the uncertainties that come from ground motions time and frequency content alteration because of scarcity of the recorded ground motions in the database. Second, uncertainties associated in the modeling and simulation procedure of PBA, and third uncertainties originated from simplistic approach and methods utilized in the conventional procedure of PBA of the structures. Legitimacy of the scaling of ground motions is studied using the response of several simple nonlinear systems to amplitude scaled ground motions suites. Bias in the response obtained compared to unscaled records for both as recorded and synthetic ground motions. Results from this section of the research show the amount of the bias is considerable and can significantly affect the outcome of PBA. The origin of the bias is investigated and consequently a new metric is proposed to predict the bias induced by ground motion scaling without nonlinear analysis. Results demonstrate that utilizing the predictor as a scaling parameter can significantly reduce the bias for various nonlinear structures. Therefore utilizing the new metric as the intensity measuring parameter of the ground motions is recommended in PBA. To address the uncertainties associated in the modeling and simulation, MSSS concrete girder bridge class were selected due to the frequency of the construction in USCS region and lack of seismic detailing. A large scale parameters screening study is performed using Placket-Burman experimental design that considers a more complete group of parameters to decrease the computational expense of probabilistic study of the structure's seismic response. Fragility analysis for MSSS bridge is performed and the effect of removing the lesser important parameters the probabilistic demand model was investigated. This study reveals parameters reduction based on screening study techniques can be utilized to increase efficiency in fragility analysis procedure without compromising the accuracy of the outcome. The results from this study also provides more direct information on parameter reduction for PBA as well as provide insight into where future investments into higher fidelity finite element and constitutive models should be targeted. Conventional simplistic PBA approach does not account for the fundamental correlation between demand and capacity models. A more comprehensive PBA approach is presented and fragility analysis is performed with implementation of a new formulation in the component fragility analysis for MSSS bridge class and the outcome is compared with the one from conventional procedure. The results shows the correlation between demand and capacity affects the outcome of PBA and the fragility functions variation is not negligible. Therefore using the presented approach is necessary when accuracy is needed.

Syftet med denna komparativa, enkätbaserade studie var att synliggöra eventuella skillnader i uppfattningen om processen för bedömning av lärares prestationer hos skolledare i några skolor i Sverige och på några internationella skolor. I litteratur-genomgången gick jag igenom ett antal faktorer alt. delmoment som skulle kunna stödja en systematisk utvärderingsprocess och jag placerade in lärarutvärdering som ett led i skolutvecklingsarbete, ett led i den enskilde lärarens professionsutveckling och ett verktyg som stöd för att individuell lönesättning (på de skolor där lön/anställnings-kontrakt kopplas till prestation). Sex olika förutsättningar för utvärdering av lärare presenterades, vilka kopplades till ett systematiskt arbete med lärarutvärdering på skolor. Utifrån dessa ställde jag upp två utgångspunkter, vilka jag avsåg att utvärdera genom denna enkätundersökning: att skolenheter som har en tydlig vision/mission/värdegrund har en mer strukturerad process för bedömning av lärares individuella prestationer och att skolledarna på de internationella skolorna som deltar i undersökningen genomför en mer systematisk utvärdering av lärarnas arbete. Enkäten skickades ut till 94 skolledare genom ett bekvämlighetsurval, med en svarsfrekvens på 38 (40 %). Resultaten visar att den första utgångspunkten inte kunde styrkas genom resultaten men däremot visar det sig att de deltagande skolledarna på de internationella skolorna arbetar något mer systematiskt med lärarutvärdering. Några av de områden där de skiljer sig från de svenska skolledarna i sina svar och som är potentiella utvecklingsområden i det pedagogiska skolledarskapet är utbildning i ämnet, processinriktad utvärdering och tid ägnad åt detta, frekvensen i användandet av observationer/lektionsbesök i utvärderingsprocessen, en tydlig struktur för utvärderingsarbetet och systematik för dokumentation om lärarnas arbete. Utifrån resultaten ser jag en risk att skolledare saknar ett systematiskt och strategiskt förhållningssätt och kunskap om lärarutvärderingar både vad gäller varför, vad, hur och när de ska göras. Kanske gör de bedömningar av lärares individuella prestationer mest på en höft, går på känslan, saknar underlag, utgår från personliga relationer och fattar ad hoc beslut. Vad detta innebär för skolutvecklingsprocessen måste utredas vidare. / The purpose of this comparative, online survey was to bring forth any differences in the perception of the process around teacher performance evaluation among school leaders of a few public schools in Sweden and of a few international schools. In the literature review a number of factors and modules were presented that could support a good systematic evaluation process and I positioned teacher assessment within the frame of school development, within the frame of individual teacher professional development and as a tool to support individual salary systems (at schools were salary and/or contracts are connected to performance). Six main presumptions were put forward concerning teacher assessment, which were connected to a systematic approach to teacher evaluations.  Based on these, two main assumptions were made and aimed to be evaluated through the survey; that schools with a clear vision/mission/value statement have a more structured process for individual teacher assessment and that the participating international school leaders have a more systematic evaluation process for teacher assessment. The survey was sent out to 94 school leaders chosen through a convenience sample, with a response rate of 38 (40 %). The results from this study do not support the first assumption but do show that the school leaders at the represented international schools have a somewhat more systematic work process for teacher assessment. Some of the areas were differences are present and that can be considered potential development areas within the pedagogic leadership are: education about teacher assessment, a process orientated assessment system and time spent on this process, the frequency in usage of lesson observations during the assessment process, a clear structure for the assessment process and the use of a systematic method to document collected data. Based on the results I see a risk that school leaders lack a systematic and strategic approach and knowledge about teacher assessment both considering the why, the what, the how and the when it should be conducted. Maybe they judge teachers’ individual achievements based on coincidence, feeling, limited information, and personal relationship and/or make ad hoc decisions. How this effects school development needs to be researched further.