Operational Problems in Structural Nodes of Reinforced Concrete Constructions

Abstract

Reinforced concrete structures are frequently designed and executed in such facilities as: halls, warehouses, factories, multi-family buildings, single-family buildings, tanks, silos and many others. For this type of structures, it is particularly relevant to provide an appropriate thickness of concrete lagging, which aims at protecting reinforcement against corrosion, and to design it with appropriate spacing allowing the in-between space to be filled with a concrete mix. A frequent problem met while making reinforced concrete structures is such a density of reinforcing bars, particularly within structural nodes, that there is no possibility of filling the space between them with a concrete mix or it is not possible to vibrate the concrete mix in order to prevent segregation of mixture components. Structural nodes are points where special attention should be paid to careful compaction of concrete mixes and application of measures that prevent concrete from adhering to molds. The case study illustrates two structural nodes connecting a column with a bolt, located in a wall with a column-transom structure. During the modernisation works carried out in the production hall there were exposed two structural nodes completely unfilled with a concrete mix and with visible reinforcing bars that showed little buckling and the onset of corrosion. The columns, due to their location in the general static scheme of the wall, were subjected to compression or locally compressed and affected by bending. Particularly unfavourable was the fact that the columns did not feature the concrete lagging in the compression zone of the element. Removal of concrete lagging in the compression zone always results in decrease in the bearing capacity of a structure. It can be concluded that due to faulty workmanship the columns had a lower load bearing capacity than anticipated in the building permit design. The paper provides software-derived guidelines for repairing reinforced concrete columns so as to obtain the value of load bearing capacity equal or higher than expected in the design and on the assumption that repair works would be carried out on columns subjected to loading.