<p>After only two years of service, extensive cracking was found in the webs of two light-rail commuter line bridges in Stockholm, the Gröndal and Alvik bridges. Due to this incident it was found necessary to study the means available for analysing shear cracking in concrete structures subjected to in-plane stresses. The aim of this PhD project is to study shear cracking with these two bridges as reference. In this thesis, the first part aims to study the possibility of using finite element analysis as a tool for predicting shear cracking for plane state stresses. The second part is concerning how the shear cracks are treated in the concrete design standards.</p><p>Shear cracking in reinforced beams has been studied with non-linear finite element analyses. In these analyses the shear cracking behaviour was compared to experiments conducted to analyse the shear failure behaviour. Finite element analyses were performed with two different FE programs Abaqus and Atena. The material model used in Atena is a smeared crack model based on damage and fracture theory with either fixed or rotated crack direction. The material model used in Abaqus is based on plasticity and damage theory. The fixed crack model in Atena and the model in Abaqus gave good results for all studied beams. For the two studied deep beams with flanges the results from the rotated crack model were almost the same as obtained with the fixed crack model. The rotated crack model in Atena gave though for some beams a rather poor estimation of the behaviour.</p><p>The calculation of crack widths of shear cracks has been studied for the long-term load case in the serviceability state for the Gröndal and Alvik bridges, with the means available in the design standards. The methods based on the crack direction corresponding to the principal stress and do not include the effect of aggregate interlocking seems to be too conservative. Two of the studied methods included the effect of aggregate interlocking, it was made either by introducing stresses in the crack plane or implicitly by changing the direction of the crack so that it no longer coincide with the direction of principal stress. For calculations based on probable load conditions, these methods gave estimations of the crack widths that were close to the ones observed at the bridges. Continuous measurements of cracks at the Gröndal and the Alvik bridges have also been included. Monitoring revealed that the strengthening work with post-tensioned tendons has, so far, been successful. It also revealed that the crack width variations after strengthening are mainly temperature dependent where the daily temperature variation creates movements ten times greater than those from a passing light-rail vehicle. Monitoring a crack between the top flange and the webs on the Gröndal Bridge showed that the top flange was moving in a longitudinal direction relative to the web until the strengthening was completed. The crack widths in the sections strengthened solely by carbon fibre laminates seem to increase due to long-term effects.</p>

After only two years of service, extensive cracking was found in the webs of two light-rail commuter line bridges in Stockholm, the Gröndal and Alvik bridges. Due to this incident it was found necessary to study the means available for analysing shear cracking in concrete structures subjected to in-plane stresses. The aim of this PhD project is to study shear cracking with these two bridges as reference. In this thesis, the first part aims to study the possibility of using finite element analysis as a tool for predicting shear cracking for plane state stresses. The second part is concerning how the shear cracks are treated in the concrete design standards. Shear cracking in reinforced beams has been studied with non-linear finite element analyses. In these analyses the shear cracking behaviour was compared to experiments conducted to analyse the shear failure behaviour. Finite element analyses were performed with two different FE programs Abaqus and Atena. The material model used in Atena is a smeared crack model based on damage and fracture theory with either fixed or rotated crack direction. The material model used in Abaqus is based on plasticity and damage theory. The fixed crack model in Atena and the model in Abaqus gave good results for all studied beams. For the two studied deep beams with flanges the results from the rotated crack model were almost the same as obtained with the fixed crack model. The rotated crack model in Atena gave though for some beams a rather poor estimation of the behaviour. The calculation of crack widths of shear cracks has been studied for the long-term load case in the serviceability state for the Gröndal and Alvik bridges, with the means available in the design standards. The methods based on the crack direction corresponding to the principal stress and do not include the effect of aggregate interlocking seems to be too conservative. Two of the studied methods included the effect of aggregate interlocking, it was made either by introducing stresses in the crack plane or implicitly by changing the direction of the crack so that it no longer coincide with the direction of principal stress. For calculations based on probable load conditions, these methods gave estimations of the crack widths that were close to the ones observed at the bridges. Continuous measurements of cracks at the Gröndal and the Alvik bridges have also been included. Monitoring revealed that the strengthening work with post-tensioned tendons has, so far, been successful. It also revealed that the crack width variations after strengthening are mainly temperature dependent where the daily temperature variation creates movements ten times greater than those from a passing light-rail vehicle. Monitoring a crack between the top flange and the webs on the Gröndal Bridge showed that the top flange was moving in a longitudinal direction relative to the web until the strengthening was completed. The crack widths in the sections strengthened solely by carbon fibre laminates seem to increase due to long-term effects. / QC 20101119

O sistema estrutural de pisos com lajes mistas, também chamadas de lajes com fôrma de aço incorporada e popularmente conhecido como steel deck&#174;, é de desenvolvimento recente no Brasil e tem ganhado espaço na indústria da construção civil. Pesquisas internacionais recentes têm mostrado que os efeitos da retração não-uniforme, da fluência e da fissuração são significativos para a evolução dos deslocamentos verticais. No entanto, não há referências na literatura nacional de investigações sobre o tópico, como é usual para as estruturas de concreto armado. Desta forma, o presente trabalho tem como foco estudar o comportamento em serviço de lajes mistas de aço e concreto, com ênfase nos deslocamentos verticais (flechas) diferidos no tempo. São considerados os efeitos da retração e da fluência do concreto, além da interação entre o perfil de aço e o concreto. Um programa experimental exploratório com dois protótipos de lajes mistas idênticas, uma submetida a um carregamento imposto e outra sujeita apenas ao peso próprio, submetidos a um ensaio de longa duração de 260 dias. Os deslocamentos foram medidos diariamente e as condições de temperatura e umidade do ambiente foram monitoradas. Observou-se a evolução das flechas diferidas ao longo dos 260 dias na ordem de 3,20 vezes maior que as flechas imediatas. Ensaios de flexão a quatro pontos foram realizados com as duas lajes submetidas ao ensaio de longa duração e a outras duas com idade de 28 dias, não sendo observado influência do tempo quanto à capacidade resistente das lajes mistas. Finalmente, abordagens analíticas de previsão de flechas foram aplicadas aos protótipos testados e também a outros modelos experimentais presentes na literatura. Os valores previstos por diferentes abordagens de avaliação foram comparados aos resultados experimentais, observando-se que as abordagens que não levam em conta os efeitos da retração não-uniforme e fluência tendem a subestimar a previsão. As abordagens com consideração dos efeitos diferidos apresentaram boa acurácia e destaca-se a importância da consideração dos efeitos dependentes do tempo na previsão dos deslocamentos verticais das lajes estudadas. / The structural floor system using steel-concrete composite slabs also called slabs with profiled steel decking and popularly known as steel deck&#174;, has a recent development in Brazil and has taken space in the civil construction industry. Recent international researches have shown that non-uniform shrinkage, creep and cracking are significant for the time-dependent deflections of those slabs. However, there is no reference in the Brazilian literature of any study investigating the time-dependent behavior of composite slabs, as it is usual for reinforced concrete structures. So, this work focuses on the study of the in-service behavior of steel-concrete composite slabs under long-term conditions. The main emphasis lies on considering the time-dependent effects due to concrete shrinkage and creep, besides the influence of the steel-concrete interaction to calculate the slabs deflections. An exploratory experimental program with two prototypes of identical composite slabs, one subjected to an imposed loading and another subject only to self-weight, submitted to the 260-day long test. During all testing time, they were taken daily measurements of deflection and temperature and humidity conditions were monitored to understand its influence. The time-dependent deflections during the 260-days on the order of 3.20 times greater than the instantaneous deflection were observed. Four-point bending tests were performed with the two slabs submitted to the long-duration test 260-day and two others with a 28-day age. No influence of time was observed on the resistant capacity of composite slabs. Finally, analytical approaches to predict the deflections of the slabs were applied to the prototypes tested and other experimental tests from the literature. The calculated values by different evaluation approaches were compared to the experimental results. The evaluation approaches that do not take into account the effects of non-uniform shrinkage and creep tend to underestimate the previsions. The evaluation approaches considering the time-dependent effects presented good accuracy. The importance of the time-dependent effects for the deflections is demonstrated.

This diploma thesis deals with design and assessment of selected parts of the reinforced concrete frame of multi-storey administrative building according to the ultimate and serviceability limit state. The aim of this thesis was to design and assess the reinforced concrete structure of a slab above the first floor, one column, a foundation pad and a staircase. In addition to the static calculation, drawing documentation is included. Internal forces were obtained from the 3D model created in computational software Scia Engineer 16.1.

The aim of this thesis is the design and analysis of pedestrian bridge across the lagoon. Three variants were designed. The variant of structure, which combines stress ribbon with steel arches, was chosen for analysis. There is a chapter in this thesis which deals with an ideal shape of arches for different types of loads. The calculation of load effects was made in software Ansys 17.0, considering scnstruction stages. Ultimate limit state and state limit state are evaluated. For evaluation of concrete cross sections was used MS Excel. Steel cross sections were evaluated in software Ansys 17.0. d Dynamic behaviour of construction was assessed. The mode shapes and natural frequencies were calculated. The harmonic excitation response was studied. The loss of stability was checked. The design and assessment are according to the european standards.

The main focus of this master thesis is the design and assessments of the bridge structure consist of a stress ribbon supported by a steel arch. Three preliminary studies of pedestrian bridges above the valley were created and the one with semi-through deck supported by arch through cables was chosen to detail processing. This thesis includes a chapter, which deals with finding the ideal shape of arch. The computational beam model for the analysis of the structure was created in software Ansys Mechanical including the construction stages. The correctness of the computational model was verified by the secondary model created in the software Midas Civil. For evaluation of the structure in crosswise direction was created slab model in software Midas Civil. The structure was evaluated considering the ultimate serviceability state and ultimate limit state according to currently valid standards. The thesis also includes dynamic analysis.