Soil-structure interaction of steel fibre reinforced concrete slab strips on grade with geogrid reinforcement

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University of New Brunswick


Performance of slabs on grade is mainly governed by the mutual coupled performance of the slab stiffness and the subgrade support. The use of reinforcement geogrids to increase the structural capacity of the subgrade support can be potentially advantageous, but is currently poorly understood (especially under frequent transient loading conditions). The objective of this experimental study is to investigate the beneficial use of geogrids as a reinforcing material in a loose subgrade. Experiments on three slab strips (300 mm x 150 mm x 2500 mm) are completed by the author. Two slab strips contain steel fibres and one slab strip is reinforced with welded wire fabric (WWF). All slab strips are tested under a central point load and are restrained from uplift at the ends. Both monotonic and cyclic loads are considered. The responses for each slab strip are compared to previous tests carried out at UNB for an unreinforced loose subgrade. It is noted that the geogrid increases the bottom surface cracking load of the slab strip, does not affect the top surface cracking load, and increases the ultimate load carrying capacity of the slab strip. The SFRC proves to be successful in providing post-cracking strength to maintain slab integrity when compared to the WWF reinforced slab strip used in this investigation. The analysis of beams on grade is carried out for the elastic and post-cracking regions. The elastic analysis is based on an analytical solution, and the post-cracking stage is developed by using a plasticity based approach. The predicted values for the SFRC slab strip under monotonic load are compared to the measured load-deformation response. The comparison indicates that the theoretical data underestimate the capacity of the SFRC slab strip.