The Effect of Bottom Reinforcement Spacers on Reinforced Concrete Structures Loaded by Explosion

Plastic spacers create a linear and systemic weakening of the structure. The extreme loading of the structure tests the structure itself to its load-bearing limit or even locally exceeds this limit, thus revealing all its weak points, which are the spacers. Nevertheless, the influence of the spacers is not included in the design calculation of the reinforced concrete element. In addition, products intended as spacers for the placement of reinforcement do not belong to the specific families of construction products covered by a harmonized standard of European parliament regulation. For these reasons, it is not required to demonstrate any characteristics of these products. This fact allows the use of arbitrary spacers’ shapes and materials. As shown by the experiment carried out, the use of commonly used plastic liners will result in a weakening of the cross-section. The normal assessment of the ultimate or serviceability limit state is not affected by this weakening. An example of an experiment carried out where this problem was captured is the subject of this paper. With Europe’s current deteriorated safety situation, understanding the influence of spacers in blast-loaded reinforced concrete structures on structural failure is important, and it is appropriate to further address this issue. Based on this experiment, it is not possible to accurately identify the causes of the explosion cracks. In order to determine with certainty the effect of spacers on the strength of the structure under abnormal blast loadings, research needs to focus on this area. In the field experimental measurements and numerical simulations, it was found that the use of linear spacers has an effect on crack formation under the blast action of the tested slab.

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