Unshoring Process of a Temporary Pillar, in a Seventeen-Storey Building in Sant Adrià del Besós

Abstract

In the new construction of a seventeen-storey building, a provisional prop of fourteen-meter height, horizontally braced on two intermediate levels, has been used. Despite the fact that structural logic suggests that it can be cut without having any added safety precautions, the structure of the building, made up of cores and reinforced concrete slabs working spatially, indicates that certain mechanisms be introduced so that, in the event that different and worse behaviors than expected are detected, the process can be stopped and the consequences of the new situation observed can be analyzed. For this purpose, two pairs of four metallic cantilevers were introduced at mid-height with four hydraulic pistons. In addition, the best position of a series of strain gauges as well as transducers were analyzed. At first, a load test was carried out to check that the brackets worked correctly. Once this step was verified, the abutment was cut, and the results were read. The results of stresses and deformations were compared with those expected, always being satisfactory. Finally, four provisional profiles were placed in case after a few days the structure suddenly gave way. The research focuses on obtaining an efficient control system and achieving total security throughout the process, with the comparison of the results strictly necessary for this case. Few resources were used so as not to make the work excessively expensive. We have found important divergences, on the side of security, between calculation and reality. We have also considered that the construction process has an impact on the final results. In the same way, the rigidity of the temporal abutment must be considered before the calculation. All these factors have generated a lower-than-expected deformation in an 8 m cantilever