Freeze-thaw damage evaluation and model creation for concrete exposed to freeze–thaw cycles at early-age

Concrete subjected to freeze–thaw cycles action at early-age will suffer serious physical damage, resulting in degradation of the concrete’s performance. The subsequent curing conditions after early-age freeze–thaw cycles (E-FTCs) are critical to the development of the properties of frost-damaged concrete. Four test environments were set up for this study, based on different numbers of E-FTCs and subsequent curing conditions. The later-age resistance to freeze–thaw of concrete exposed to E-FTCs was evaluated by analysing the influence of precuring times and curing conditions. Results show that the earlier the FTCs occur, the worse the later-age freeze–thaw resistance is. In particular, for the frost-damaged concrete with a pre-curing time of 18 h, its freeze–thaw resistance is significantlypublishedVersio

Remote bridge inspection using optical methods

Routine bridge inspections usually consist of visual observations. These inspections are time-consuming and subjective. There is a need to identify new inspection techniques for infrastructure that reduce traffic disturbance, and improve the efficiency and reliability of the acquired data. This study compared the performance of three different imaging technologies for the three-dimensional (3D) geometric modelling of existing structures: terrestrial laser scanning, close-range photogrammetry, and infrared scanning. Each technology was used to assess six existing concrete railway bridges. The results suggest that all methods investigated can be used to create 3D models, however, with different level of completeness.Remote bridge inspection using optical methodspublishedVersio

Mechanical and durability properties of concrete subjected to early-age freeze–thaw cycles

Early-age frost damage to concrete used in winter construction or in cold environments negatively affects the development of the hydration process and the performance of the concrete, thereby reducing the service life of the building structure. Experimental research was carried out to investigate the compressive strength,resistance to chloride penetration and resistance to freeze–thaw of concrete specimens subjected to earlyage freeze–thaw cycles (E-FTCs). The effects that different pre-curing times of concrete and mineral admixtures have on the properties of early-age frostaffected concrete were also analyzed. Results show that the earlier the freeze–thaw cycles (FTCs), the poorer the later-age performance. Later-age water-curing cannot completely restore the damage that E-FTCs do to concrete. In the same conditions used in this study, the effects of E-FTCs on later-age mechanical and durability properties of ordinary Portland cement concrete (OPC)are small. The incorporation of fly ash significantly reduces the resistance to freeze–thaw of concrete during early-age and later-age. The presence of silica fumes has an adverse effect on the later-age resistance to freeze–thaw. In general, the recovery percentage of later-age durability indexes of concrete subjected to E-FTCs is lower than that of compressive strength. For concrete subjected to E-FTCs, it is more important to ensure the recovery of later-age durability.publishedVersio

Upgrading of freight railways to meet operational and market demands

The European objective of a modal shift of freight transports to railways will require extensive upgrading of existing railway lines since very few dedicated freight railways are currently being built and existing lines were built for traffic demands at the time of construction. A transition to increased and enhanced railway freight operations can therefore be costly and complicated. To minimize negative effects, a guideline for upgrading was developed within the Capacity4Rail project. The current paper presents the major findings from this guideline. In particular it outlines different upgrading possibilities and their implications, and details structured approaches to upgrading analyses. Setting out from the Capacity4Rail handbook, the current paper discusses possibilities for upgrading of substructures, bridges, tunnels, and the track structure. In these areas, an overview of challenges and possibilities is presented together with examples of experience from operational upgrading. The paper concludes that freight line upgrading using a more streamlined approach as outlined in the guideline is a necessity if EU objectives on modal shifts in transportation are to be met. Further, it demonstrates why a political drive is necessary to increase efforts to upgrade freight lines

Application of fracture mechanics to concrete structures

Various examples are presented on how fracture mechanics can be used to get a better insight into the behaviour of structural concrete components. Special emphasis is given to the phenomenon of size dependence. Since dependence is shown to be a function of a brittleness number which is derived from a simple study of energy. The concept of brittleness has similar features as slenderness -  a well established parameter in the design of elements in compressionISBN för värdpublikation: 9789061919889</p

Torsion-bending-shear in concrete beams : a kinematic model

A kinematic solution according to the theory of plasticity is presented for reinforced concrete beams loadid in combined torsion, bending and shearGodkänd; 1979; 20061113 (ysko

Arne Hillerborg and Fracture Mechanics

The paper gives an overview of Arne Hillerborg's contributions to Fracture Mechanics. Arne Hillerborg was born in 1923 and was a professor at Lund Institute of Technology 1968-1989.Godkänd; 1991; 20150411 (elfgren

Reinforced concrete beams loaded in combined torsion, bending and shear : a study of the ultimate load-carrying capacity

Upprättat; 1972; Bibliografisk uppgift: Ph D Thesis at Chalmers University of Technology New Series No 28; 20090214 (elfgren

Amerikansk forskning om byggkonstruktioner : Rapport från ett akademiskt år i USA och Kanada 1972-73

Godkänd; 1975; 20090723 (elfgren

Field investigation of load‑curvature characteristics of reinforced ice

Load-deformation characteristics are studied for three types of top reinforcement in a floating ice cover: (a) sand, (b) birch branches and (c) sawn timber. The curvature of the ice cover is measured during application of a constant load. A three-parameter creep model is proposed for the ice deformation. Expressions are deduced for the characteristic lenght and the maximum deflection of the ice cover based on the curvature.Godkänd; 1986; 20071204 (pafi)</p