Marco Andreini

MECHANICAL CHARACTERIZATION OF MASONRY WALLS WITH CHAOTIC TEXTURE: PROCEDURES AND RESULTS OF IN-SITU TESTS

An in-situ experimental testing campaign on stone masonry walls performed in the Volterra (Pisa, Italy) hospital complex is described herein. The test-site is a disused building, dated back to the early 1930s, which offered the opportunity to perform destructive and non-destructive tests with multiple purposes: the masonry mechanical characterization of a wide group of nearby similar buildings, the comparison of several testing methods applied on masonry with chaotic texture and the development of the innovative twin panel test procedure. In this context, the failure mode for panels under shear and compression forces was interpreted and, through the results obtained from different techniques (flat-jack test, drilling test, diagonal compression test and shear compression test), a safety domain shear vs. compression for the rubble masonry type was also drawn up. The cross validation of several testing methods can suggest strategies to determine shear strength, deformation properties and ductility capacity of stone masonry walls with highly irregular texture.

Structural damage in the cities of Reggiolo and Carpi after the earthquake on May 2012 in Emilia Romagna

This paper addresses the structural damage to the main buildings of the cities of Reggiolo and Carpi after the primary earthquake shocks on May 20th and 29th, 2012, in Emilia Romagna. The damage survey, performed via form-based methods, highlights the different seismic behaviour of several types of buildings, especially those having historical features, and the consequences of the damage in terms of costs. Moreover, an analysis of some failure mechanisms activated in Reggiolo enables the evaluation of the local peak ground acceleration, due to the soil amplification.

Archaeological consolidation of UNESCO masonry structures in Oman: the Sumhuram Citadel of Khor Rori and the Al Balid Fortress

A series of missions, starting from early 2005 up to 2009, have been managed to restore the ancient city walls of Sumhuram(4th century bc to 6th century ad) in the site of Khor Rori, with a group of archaeologists of the University of Pisa. Also, from early 2007, a series of missions have been managed to consolidate the dry masonry Fortress in UNESCO site of Al Balid erected circa 1100 ad with archaeologists of the University of Missouri. Both sites are located in the area of Salalah in southern part of the Sultanate of Oman. The sequence of dry season and rainy season during the Khareef period (Monsoon phenomena) caused several collapses on the excavated masonry structures, with risks for safety of visitors and archaeologists. The walls of Sumhuram, affected by the loss of connection between the two limestone masonry faces, have been rebuilt with the original texture of bricks using a new mix design for mortar joints with the same colors, consistency, and proper strength and durability. The safety level of the consolidation works is evaluated by observing on site the shape of the collapse surfaces and using the classical limit analysis approach. The collapses of Al Balid dry masonry walls have been originated by the loss of permeability of the external wall faces due to the progressive filling of joint by soil. Consolidation activities consisted of rebuilding with the same blocks down and substituting the earth behind the external layers with gravel and high permeability filling. An analytical model of dry rigid block masonry with frictional interfaces has been used to represent the out-of-plane behavior, in order to define the maximum height of excavation and the maximum free height of the restored walls to guarantee safety for workers.

Structural Analysis and Consolidation Strategy of the Historic Mediceo Aqueduct in Pisa (Italy)

The present work assesses the state of conservation of the historical Mediceo Aqueduct in Pisa, with classification of architectural elements, decay of materials and failures in view of the restoration. The preview of collapses and the design of interventions in a significant part of the aqueduct are performed. New masonry buttresses for the entire path with optimal distribution are determined to ensure safety and integrity to the monument.

Collapse of the Historic City Walls of Pistoia (Italy): Causes and Possible Interventions

In the paper are discussed the likely causes of the collapse and the temporary safety features adopted to secure a collapsed portion of the Historic Walls of the city of Pistoia (Italy). The walls of medieval origin, affected by various subsequent modifications and alterations, have been subjected to a sudden collapse, after a period of heavy rain, for a length of about 25 meters. Hereby are described the probable causes of the collapse, due to a poor quality of the walls (external façades with external layer made up of river pebbles and inner filling material in-coherent), height of building is not modest (approximately eleven meters), a significant differential in height between the two faces (about four meters) and a not unlikely rotation of the base. It is proposed a technique of temporary reinforcement with a system of steel tie-beams and braces with a view to the work of reconstruction of the partially collapsed and consolidation of the lateral parts of wall.

An Innovative Low Cost Solution for Bamboo Trusses with High-Ductility Connections

Innovative solutions of bamboo connections and an application on Polonceau trusses to use for simple constructions are presented. Experimental tests show the performances and the high level of ductility of the proposed technique, joined with simplicity, with low-level of technology and low cost of all used materials. Their applications with sustainable maintenance are suitable in developing countries.

Probabilistic models for the erosion rate in embankments and reliability analysis of earth dams

Abstract Probabilistic models for the concentrated leak erosion of earthen water retaining structures are presented. The models predict the values of the critical shear stress, the coefficient of erosion and the pipe radius enlargement, starting from other measurable soil properties and the geometrical dimensions of the embankment. The models account for both the non-cohesive and cohesive contributions to the erosion behavior. A Bayesian approach is used for the treatment of the unknown parameters. An importance sampling simulation is adopted to calibrate the models and estimate the posterior distribution of the unknown model parameters using laboratory and in situ experimental data. The new proposed probabilistic model for the pipe radius is then used to develop fragility curves that capture the pipe enlargement as a function of time for a given earth dam.

Seismic Consolidation of ’60s Pilotis R.C. Building for Social Housings with SCC-Steel Shear Walls

The reinforcement of a r.c. building for social housing has been achieved by using Steel-Concrete Composite (SCC) walls at the ground floor, preceded by temporary brick pillars for structural deficiency to vertical loads, due to the poor load capacity of the r.c. columns. The SCC walls have been realized first by placing steel columns on both sides of the existing pillars and, after removal of the temporary brick piers, by merging the steel columns in the cast of the new walls. The top of the walls has been connected to the upper floor in order to ensure the diffusion of the seismic forces. Foundations have been reinforced to support the seismic base shear.

Simple tests and mechanical model for masonry materials at high temperatures

An experimental procedure for tests on specimens made of several materials is performed to detect the mechanical properties depending from temperature. About 200 cylindrical specimens of several materials (clay, lightweight concrete, aerate autoclaved concrete, mortar) are tested from 20°C to 700°C. The free thermal strain and the decay of axial strength are determined; proposals for the stress-strain curves and the secant modulus of elasticity in function of temperature are illustrated. The data base from tests are able to calculate the collapse domains (bending moment - axial force - time of exposure to nominal fire) which represent a simple model for the assessment of masonry panel sections subjected to fire action.

Application of RCW Base Dissipator on a Set of Masonry Buildings

An application of the RCW –Reinforced Cut Wall- on a set of four masonry buildings for council housing estate with a total of 43 lofts is presented. The performances of this low-cost base energy dissipation technique has been evaluated with some experimental on-site tests performed on a couple of specimen (40x60x30 cm) subjected to a series of cyclic quasi-static time histories with increasing intensity. Trials show the high properties of self-centering and of wide hysteretic behavior of the RCW. Numerical analyses confirm the mechanical properties and provide parameters to the evaluation of cyclic dissipation properties.