Thermal stresses in concrete structures at early ages

This thesis deals with the problem of formulating constitutive models for the analysis of early-age thermal stresses in concrete due to hydration. The main features of the work are constitutive modelling of early-age concrete behaviour experimental studies to check the models and to determine material parameters application of the models to some design and construction situations. The proposed model for thermal stress analysis in young con- crete is based on a rate-type viscoelastic law which is supplemented with a strain-softening model for high stress level nonlinearity in tension and by an adjustment for low- stress nonlinearity in compression. In order to demonstrate the potential of the model it has been applied to some typical cases in practical engineering. Thus, the risks of thermal cracking are computed for A - a section poured between inflexible supports B - a differential temperature field across a wall section C - a wall cast on a concrete slab D - a box tunnel element E - a concrete cover layer applied on a bridge pier. From the computations it is concluded that the magnitude of thermal stresses do not only depend on temperature variations but to a critical extent also on the mechanical behaviour of the hardening concrete as well as on the nature and degree of the restraint. The thermal stresses are in most cases not proportional to the temperature field within the structures as defined by maximum temperature rise, maximum temperature differences etc. It is evident from this study that, in some early-age applications, an analysis solely based on the temperature field may not even reveal whether a part of the concrete structure is in tension or compression.Godkänd; 1989; 20070424 (ysko

Temperature stresses in massive concrete structures : viscoelastic models and laboratory tests

Godkänd; 1985; 20080404 (ysko)</p

Temperature stresses in massive concrete structures : viscoelastic models and laboratory tests

Godkänd; 1985; 20080404 (ysko)</p

Fatigue strength of cable couplers in prestessed concrete beams

Godkänd; 1988; 20150226 (mem

Robust self compacting concrete for bridge construction

Validerad; 2011; 20111215 (mem

Industrialization in Swedish bridge engineering : a case study of lean construction

The purpose of the project has been to evaluate and possibly improve the degree of industrialization and productivity when constructing bridges in full scale. Earlier theoretical studies have indicated that, if prefabricated reinforcement, self compacting concrete (SCC) and permanent formwork are used the degree of industrialization can be increased markedly. To be able to realize this, Lean Construction principles prove to be important utensils during the planning and design phase as well as during the construction of a full scale project.Throughout the design and planning of this first full scale bridge project, intensive contacts between designer, contractor, client and material suppliers were established. The design team concluded that the production time at site could be reduced with up to 20 % and the number of workers could be reduced by virtually 50 % during almost half theproject. This was realized by planning with Last Planner ideas, and designing the project properly using modern construction tools and materials. The design team also concluded that if the concrete class increased some of the very dense shear force reinforcement could be left out.The evaluated outcome of the demonstration project, i.e. potential productivity improvements, structural quality improvements, immediate feasible waste and cost reductions and the positive impact on the working environment, shows that the predicted benefits made were fulfilled.Godkänd; 2007; 20070913 (ysko

Increasing the market share of SCC

Godkänd; 2010; 20110225 (ysko

Elsa och Sven Thysells Stiftelse för konstruktionsteknisk forskning inom väg och vatten vid Luleå tekniska universitet : En skrift tillägnad Donator Sven Thysell på 100-årsdagen 2016-09-02

Denna skrift ger en kort beskrivning av Elsa och Sven Thysells stiftelse för konstruktionsteknisk forskning inom väg- och vatten vid Luleå tekniska universitet. Skriften har sammanställts inför donator Sven Thysells 100-årsdag den 2 september 2016. Vi är mycket tacksamma för det stöd Stiftelsen har gett och ger till konstruktionsteknisk forskning vid LTU. Stödet betyder mycket för att vår verksamhet skall kunna utvecklas till nytta för samhälle

Increasing productivity through utilization of new construction techniques and lean construction philosophies in civil engineering projects

The implementation of Self Compacting Concrete (SCC) together with two types of reinforcement and form techniques makes it possible to increase the degree of industrialization at construction sites markedly. To be able to realize this, Lean Construction principles prove to be important utensils during the planning and design phase. Also, the working environment is improved vastly when using SCC and different prefabricated reinforcement solutions. At the construction of the first full scale project "The Industrialized Concrete Bridge", which was built during 2006 in Sweden, the new techniques were applied. It was concluded that the working environment was improved by three fold, production time at site could be reduced with up to 20 % and that the number of workers could be reduced by virtually 25 %.Validerad; 2009; 20091202 (petsim