Análisis comparativo por capacidad del cortante por punzonamiento en losas planas que no se diseñan como parte del sistema de cargas sísmicas, de acuerdo a la norma ecuatoriana de construcción, con otras normativas

Abstract

Structural flat slabs systems have become increasingly popular in the field of construction because of the advantages they offer compared to traditional systems. However, when they are affected by lateral seismic loads, the main problem of these is that they are susceptible to a punching shear failure in the connection between the slab and the column or wall. The objective of this work is to analyze the phenomenon of punching shear failure in flat slabs, which are not designed as part of the seismic loading system.

The modeling of 4, 6 and 8-story buildings was made in the structural software of analysis and design (ETABS). These buildings were simulated with the spectral seismic design from Quito, Guayaquil and Cuenca. Then the ultimate shear stresses were determined on the critical elements. The increase of shear stress due to the unbalanced moments produced by the effect of the seismic loads was calculated. Finally the punching shear demand / capacity ratio was compared, before and after considering the shear increase due at unbalanced moments. This was done through the North American code, on which the Ecuadorian Construction Standard (NEC-2015) is based; and also by British, European and Mexican codes.

After the structures were modeled, the analysis and interpretation of results was performed. Then it was concluded that the effect of punching shear in flat slabs (which are not part of the seismic loading system) is the main reason for failure in these structural systems. This occurs because the flat slabs are designed only to resist gravitational loads and the shear increase in the connection (given by the presence of unbalanced moments produced by lateral displacements) is not considered.