Dynamic Response of Masonry Buildings with Rigid or Flexible Floors

Student: Marco Gallonelli
Supervisors: Dr Guido Magenes, Dr Andrea Penna

ABSTRACT

The target of this study is to understand the influence of different types of structural floors slab in the seismic response of the masonry structure.

Trough the static non linear and dynamic non linear analyses, it is been studied the behaviour of a set of two story masonry building with three different type of floors, that, from the point of view of the stiffness (in and out of horizontal plane), have a very different characteristics.

The first one has a rigid diaphragm; this characteristic is obtained designing a orthotropic mixed floors (brick-concrete); the second one has a flexible diaphragm, obtained considering a timberfloors and the third can be considered as a typical seismic retrofit of the second building.

In this way it is been studied the behaviour of three masonry buildings under a several number of real seismic motion, underlining the differences in the seismic response in terms of displacements, acceleration and distribution of horizontal loads on the walls.

Analyzing the effect of the stiffness floors it is clear as the bigger value of shear stiffness produce a better global response. From the point of view of the relative displacement of the walls the influences of the floors stiffness in the behaviour are evident above all for the flexible floor case. Due to the distribution of the load more or less equal for the walls, the displacement of thestiffer wall is very small in comparison with the other one, being the displacement in firs approximation inversely proportional to the stiffness. The better global response mechanism of the first building is favoured above all by the stiffness of the floors, but also the connections between the orthogonal walls, as for example using steel tie-beams, improve the global behaviour.

The solution adopted for the retrofit produces a behaviour closer to the rigid floors idealization either for the forces distribution and above all for the walls displacements.

So it is been possible to set, trough the numerical analyses, the structural configuration of the prototypes that will be really tested on the Eucentre's shacking table with a full-scale dynamic test, real finally target of this study.

You may download a digital version of this MSc dissertation here.