Title:
In Plane Shear Behavior of Calcareous Masonry Panels Strengthened by FRCM
Author(s):
Margherita Stefania Sciolti, Francesco Micelli, Allen Dudine, Maria Antonietta Aiello
Publication:
Symposium Paper
Volume:
324
Issue:
Appears on pages(s):
11.1-11.20
Keywords:
Diagonal, Fibers, FRCM, FRP, Grid, Masonry, Mesh, Shear, Strengthening
DOI:
10.14359/51702363
Date:
4/1/2018
Abstract:
Unreinforced masonry construction are typically prone to brittle failures due to the nature of their
constituent materials, and in many cases their strength is related to the shear strength of the primary walls. In regions
affected by intense seismic events, the presence of heritage construction made by poor masonry, strongly enhance
this type of vulnerability. The recent earthquakes that occurred in the past ten years in the Eurasian regions drew the
attention of researchers and engineers in this sense, since entire cities formed by ancient masonry buildings were
affected by extensive disasters and human losses. In order to find an effective solution to these important structural
problems, composite materials in forms of Fiber Reinforced Polymers (FRP) were found to be effective and
attractive in many cases, showing a good applicability both in reinforced concrete (RC) buildings and masonry
construction. In this last case they are well accepted in modern masonry construction, but the use of epoxy resin as
matrix and adhesive, combined with high performance fibers (i.e. carbon) have shown some limitations in the field
of heritage masonry construction, in which the substrate is very poor. In this perspective two main issues obstacle an
effective use of FRP: the mechanical compatibility and the saturation of the surface respect to transpiration of
humidity. For these reasons in Europe there are some real applications of heritage masonry buildings in which the
use of FRP is not welcome by the authorities that are asked to evaluate the strengthening proposals The problem of
the mechanical compatibility is due to the differences between the stiffness and strength of the fibers (typically
carbon) and the properties of the masonry substrate which may be 10-3 times those of the fibers. The problem of
breathability is due to the fact that polymeric resins create an impermeable jacket which interrupts the cycle of
humidity transpiration through the masonry. This may lead to a degradation of the masonry, in the long terms,
because of the saline formations. For these reasons the use of a new generation of fibrous materials named as
Fiber/Fabric Reinforced Cementitious Matrix (FRCM) was introduced, in order to use long reinforcing fibers into an
inorganic matrix based on lime or cement mixes. These new materials have lower mechanical properties respect to
FRP composites, but they show higher compatibility with poor masonry.
The present manuscript illustrates the results of an extensive experimental campaign, in which masonry panels,
made with limestone and poor hydraulic mortar, were tested under diagonal shear forces, until failure. The panels
were tested in unreinforced configuration, then different FRCM reinforcement systems were applied and tested to
compare the respective results. Both single wall and double wall panels were tested in order to represent different
cases found in real applications. Totally thirty specimens were tested. The results, illustrated and discussed in the
paper, show the significant increase in terms of mechanical properties that was measured in all cases of FRCMstrengthened
walls. Due to the use of different mortars and fibrous systems some differences in terms of failure
modes and damage at failure will be shown, even if it is reasonable to believe that for the type of masonry tested
herein, all the strengthening methods resulted tremendously effective in terms of load capacity and energy
dissipation, without showing a sudden brittle collapse.