Marija Kušter

Modeling damage in concrete caused by corrosion of reinforcement: coupled 3D FE model

Reinforced concrete structures, which are exposed to aggressive environmental conditions, such as structures close to the sea or highway bridges and garages exposed to de-icing salts, often exhibit damage due to corrosion. Damage is usually manifested in the form of cracking and spalling of concrete cover caused by expansion of corrosion products around reinforcement. The reparation of corroded structure is related with relatively high direct and indirect costs. Therefore, it is of great importance to have a model, which is able to realistically predict influence of corrosion on the safety and durability of reinforced concrete structures. In the present contribution a 3D chemo-hygro-thermo-mechanical model for concrete is presented. In the model the interaction between non-mechanical influences (distribution of temperature, humidity, oxygen, chloride and rust) and mechanical properties of concrete (damage), is accounted for. The mechanical part of the model is based on the microplane model. It has recently been shown that the model is able to realistically describe the processes before and after depassivation of reinforcement and that it correctly accounts for the interaction between mechanical (damage) and non-mechanical processes in concrete. In the present paper application of the model is illustrated on two numerical examples. The first demonstrates the influence of expansion of corrosion products on damage of the beam specimen in cases with and without accounting for the transport of rust through cracks. It is shown that the transport of corrosion products through cracks can significantly influence the corrosion induced damage. In the second example the numerically predicted crack patterns due to corrosion of reinforcement in a beam are compared with experimental results. The influence of the anode–cathode regions on the corrosion induced damage is investigated. The comparison between numerical results and experimental evidence shows that the model is able to realistically predict experimentally observed crack pattern and that the position of anode and cathode strongly influences the crack pattern and corrosion rate.

Holistic Approach to Design of New Bridges Across Sava River in Zagreb

Zagreb, Croatian capital, is situated on both Sava river banks. However, currently there are only seven bridges across the river in the inner city limits. To solve the problem of the inadequate capacity of the Sava River crossing in Zagreb, two new bridges are planned in the near future as part of the solution for sustainable development of the Sava River banks area in Zagreb. Differences in planning and design of bridges in 20th and 21st century will be analyzed highlighting new applied, holistic approach to design Jarun and Bundek Bridge.

Sustainable Large Arch Bridge Maintenance through Inspections, Assessments, Monitoring, Repairs and Service Life Modelling

The paper provides an overview of maintenance activities on seven large reinforced concrete arch bridges in Croatia located on Adriatic coastline, built in two periods: in the 1960’s and 1970’s and at the last turn of the century. Inadequate attention to durability issues in combination with very aggressive maritime environment has led to expensive and technically demanding repair works on older arch bridges. The design of more recent constructed bridges took into account the experience from the in-service performance of older arch bridges. Moreover, structural health monitoring systems have been installed on those bridges. As chloride-induced corrosion is the major cause of deterioration of the Adriatic RC arch bridges, a numerical model, which can realistically simulate effects of reinforcement corrosion in concrete is developed and implemented into the finite element code to predict service life of new or already damaged structure.