No abstract

The distribution of restraint stresses in bottom-restrained walls is an important information for the efficient crack control of wall-like concrete members. Practical examples are retaining walls, bridge abutment walls or tank walls, for which the results can be used in order to assess the risk and intensity of harmful separating cracks over the wall height. Different solutions exist for the determination of these stress distributions, ranging from advanced computational methods over analytical and semi-analytical solutions up to empirical approaches. The aim of the present contribution is twofold. On the one hand, the general applicability as well as commonalities and differences of the investigated solutions were demonstrated by using them for the analysis of a given demonstration example. On the other hand, a parametric study was carried out in order to assess the dependence of the prediction quality of the applied solutions on changing conditions. Altogether it was found that advanced computational methods and analytical or semi-analytical solutions showed a good agreement for common design tasks. Solutions with empirical modifications, however, were proved to be less satisfying from engineering perspective due to predefined parameters or mechanically inconsistent modifications.

Considering the importance of leaking cracks in terms of serviceability and durability of watertight concrete structures, emphasis is placed on thermal movements and their effect on foundation slabs and walls. Both members are usually restrained to some degree externally and/or internally. The results indicate that restrained thermal stresses are the primary cause of early-age cracks in concrete members. This paper offers a discussion of mitigation strategies to prevent the formation and propagation of early-age separating cracks. A FEM-based analysis was used to determine the development of stresses in walls on mat foundations in relation to the crack risk assessment.

When concrete structures with specific performance requirements call for cracking to be avoided, a reliable crack assessment of hardening concrete members is a crucial task for the design. Concrete walls cast onto already hardened foundation slabs represent an example of externally restrained members commonly subjected to strains resulting from early-age movements. As a consequence, unacceptable cracks may develop. The key parameter for a reliable design of such members is a correct assessment of the hardening phase with respect to the deformation behavior followed with parallel evolution of stiffness and strength properties.This contribution aims to present a macroscopic numerical thermodynamic model which can be used for solving the transient thermal field of a chosen structural detail subjected to thermal loads during early ages. In connection with stress development control, the model represents a mechanical based crack assessment tool for hardening concrete members. Its applicability is discussed at a model solution of a wall-to-slab connection detail in a waterproof concrete basement structure. The model outcome values are verified using data from experimental field measurements.

The paper reports the results of a case study for achieving longer service life and increasing the environmental sustainability of concrete silos. Damage mechanisms in concrete silo walls, and respectively in cylindrical structures (e.g., chimneys, cooling towers, and tanks), are widely diverse. The common causes of failures include those due to poor design considerations, construction deficiencies, non-compliance with operational rules and regulations, lack of maintenance, and insufficient and/or corroded reinforcements, together with the environmental conditions affecting the walls. In addition to the ultimate limit state design, temperature-induced cracking may often be underestimated in the design of reinforced concrete silos, leading to premature deterioration and losses in serviceability. Cracks from environmental or service conditions facilitate the ingress of moisture and corrosive agents. Therefore, there is an increased interest in reducing the appearance of cracks and limiting their width. The aim of this paper is to highlight the synergistic effects in the design, construction, and operation of silo walls, particularly under varying environmental influences. The research undertaken indicates that systematic errors can be identified and corrected.