Abstract

The interaction between frames and infills in case of earthquake is a topic of great significance in structural engineering. Infills, often considered non-structural elements, in fact behave as they were. Sometimes they make low engineering buildings behave better than one would expect, other times they are responsible of rather bad seismic performances even in recently built constructions. Infills, often stiff and brittle if constructed with common fired bricks and strong mortar, are able to change to a great extent the seismic structural response, invalidating many of the basic design assumptions. Nevertheless, it is not possible to think of buildings without infills, due to the requirement of controlling energy consumption for residential climate control. To overcome this problem, the possibility of assembly ductile infills was investigated in the current thesis. The basic idea was to use weakness as the main tool, pursued both through the choice of materials and the proposal of a new, simple though effective building technique. Particular attention was devoted to adobe (earthen bricks) infills, specifically chosen in a structural perspective to take advantage of the intrinsic weakness, often unacceptable for other applications. Sustainability and thermo-hygrometric performances are considered important characteristics, even though background themes in comparison with weakness, according to the main perspective of this research work. The aim of the research was to evaluate the possibility of forcing a predefined damage pattern, consistent with reuse requirements, by means of ductile mechanisms. The modus operandi was to lay weak (horizontal) surfaces in the panels, breaking their continuity to allow a frictional, stable and ductile sliding to take place. The idea was investigated both numerically and experimentally. During a first phase, shear behavior of mud mortar joints was tested. Then, four full scale panels, confined by a steel frame, were subjected to lateral cyclic load. The four tests differed both in building technique, traditional or with internal partitions, and in material, hollow clay bricks or adobes. The experimental work was then extended numerically by means of FE analysis (through two modeling techniques) to different geometrical and mechanical situations. Attention was focused on the role of partitions in the structural response and on the possibility of capturing global behavior through a local calibration (on small assemblies) of model parameters. As a conclusion, the use of partitioned adobe infills was proposed in association with ductile timber frames because of the compatibility of materials. The solution may provide adequate stiffness and energy dissipation in case of earthquake. Moreover, this kind of buildings usually suffer for a lack of summer thermal insulation: the addition of mud infilling would improve such a performance.