Robustness of Reinforced Concrete Slab Structures: Lessons Learned from Two Full-Scale Tests

Abstract

Dentro del proyecto de investigación ITSAFE, se construyeron dos estructuras a escala real: una formada por un pórtico de hormigón armado de una sola planta y dos vanos con losa maciza de 7,00 × 14,00 m2, y otra consistente en un pórtico de dos plantas de 7,00 × 7,00 m2 con losas macizas. En el pórtico de dos vanos, uno de los apoyos centrales se demolió inicialmente mediante un martillo neumático, produciendo daños limitados (una flecha de 14–15 cm en la posición del apoyo eliminado). Sin embargo, aparecieron fisuras torsionales en la interfaz entre un pilar y la losa en uno de los apoyos exteriores. Cuando se retiró el segundo apoyo central, la estructura colapsó por el fallo de la conexión pilar–losa. En la estructura de dos plantas se observaron fisuras del mismo tipo tras la eliminación dinámica de un pilar, con una flecha medida de 22 cm. Estos resultados cuestionan la práctica actual basada únicamente en caminos alternativos de carga o en análisis de líneas de rotura, y sugieren la necesidad de un refuerzo específico en la conexión pilar–losa para evitar fallos prematuros.

Within the research project ITSAFE, two full-scale structures were built, one consisting of a single-storey, two-span, 7.00 × 14.00 m2 RC frame with a solid slab and another consisting of a two-storey, 7.00 × 7.00 m2 RC frame with solid slabs. In the two-span frame, one of the central supports was first demolished using a pneumatic hammer, resulting in rather limited damage (a 14–15 cm deflection at the removed support location). However, torsional cracks appeared at the interface between a column and slab in one of the outer supports. When the second central support was removed, the structure collapsed with the failure of the support–slab connection. The same type of cracking was observed in the two-storey structure, where the column removal was dynamic, and a 22 cm deflection was measured. These experimental results question current practice in which, for internal supports, alternative load path mobilizing membrane forces in the slab are said to prevent their collapse, or in the cases of edge and corner columns, rupture line analysis is used and suggests that special reinforcement at the column–support connection is also needed to prevent the premature failure of the structure.