Masonry cross vaults: an overview of the historical developments

The cross vault represents one of the most diffused and fascinating structural typologies of the European architectural heritage. Its history began almost two thousand years ago and reached a widespread use during the Middle Ages with the outstanding gothic cathedrals. Without any proper scientific support but only using trial-and-error methods, considering each building as a scaled specimen of a new one to be built, the ancient workmanship achieved a proper competence represented by the so-called rules of thumb. However, despite this long-lasting history, it is only from the eighteenth centuries that scholars have tried to tackle the problem of analytically describing its structural behaviour. In this regard, the first part of the present study is devoted to the evolution of cross vaults from the geometrical and constructive standpoint, whereas the second one describes the historical advancements of its structural behaviour, until the development of modern limit analysis

Investigation on compressive behaviour of tuff masonry panels

Existing buildings and cultural heritage in the Mediterranean area are commonly composed by tuff masonry made by squared or roughly squared tuff stones. The Neapolitan yellow tuff, in particular, is a high porous volcanic stone that has been widely used as a building material to forge traditional and monumental architecture in the Campania Region. Recent building codes focus their attention on the quantitative evaluation of the performance of existing structures under different limit states. In this context, it is evident that the availability of experimental data is of paramount importance for the vulnerability assessment and performance upgrading of existing tuff constructions. This paper reviews the experimental research carried out on medium-large yellow tuff masonry panels with single and multiple-leaf cross sections. The main target of the current work is to develop an extensive database on material data and mechanical properties of tuff masonry, in the light of recent test results. Based on the collected data, the reliability of available empirical-based relationships for estimation of strength and elastic stiffness of base materials and masonry was investigated. Moreover, the reference values of compressive strength and Young’s modulus given by the Instructions to the Italian Technical Code, 2009 for soft stone masonry, have been compared against available data, and the main results are presented

Mechanical properties of tuff and calcarenite stone masonry panels under compression

A significant number of historic and monumental buildings located in Mediterranean areas, and in particular in South-central Italy, are characterized by soft stone masonry, i.e. tuff or calcarenite. Many are exposed to seismic risk, so that a reference data base in terms of mechanical properties is of paramount importance in seismic assessment of this type of masonry structures. Over the past decades, relevant experimental research has been carried out on masonry panels that represent traditional arrangements. Investigations on their in-plane response under compression, shear and combined shear-compression loading are available. In the present work, a systematic interpretation of available data is carried out with reference to compressive behaviour of tuff and calcarenite stone masonry. The aim is to widen our knowledge about large single and multiple-leaf panel response. Results can be used to validate the estimation of mechanical properties in view of nonlinear analyses of historic masonry structures

Simplified numerical analysis of bond degradation of FRP-masonry systems for durability purposes

Fiber Reinforced Polymers have become a popular material for external strengthening of masonry structures in the last years, but still further investigations are needed in order to develop appropriate design procedures. Investigating the behaviour and performance of retrofitted masonry elements with FRP composite sheets requires considering different mechanisms and issues. Among them, the most important is the bond between FRP and substrate due to its function in transferring the stresses from the FRP sheets to the structure. Hence, conducting experimental and numerical studies for understanding the bond and its degradation mechanism due to environmental exposure is a critical subject in predicting the performance of strengthened structures. As the available information on the durability of bond in FRP retrofitted masonry elements is still rare, conducting extensive experimental and numerical studies for characterizing this phenomenon is an important issue. This paper presents a simple degradation model into an available interface model for investigating the bond degradation in retrofitted masonry elements. For this reason, at first the interface model is calibrated with the experimental tests performed at University of Minho, and then the degradation of the bond is implemented in this model through a simplified approach

In-plane behavior of tuff masonry panels strengthened with FRP diagonal layout

The present paper deals with a quantitative analysis of the shear strength behavior of masonry panels strengthened with diagonal layout. The objective of the study is to progress towards understanding the shear strength contributions from masonry and FRP to the lateral resistance of strengthened panels. To this aim, relevant experimental results of monotonic shear-compression tests are analyzed. The local behavior of the reinforcement is investigated in terms of FRP strain profiles (i.e. the transferrable tension force within FRP), and its effects on the global response of the panels assessed. The experimental results show the effectiveness of the anchorage system in restraining the FRP at the anchored edges, avoiding premature failure due to FRP debonding. As a result, the specimens were allowed to develop their full lateral resistance. A truss model approach, combined with a proper masonry strength criterion for masonry is proposed and validated. A comparison between computed and experimental data confirms the validity of the procedure in view of practical applications and code recommendations

Meso-scale three-dimensional modeling of bond in FRP-strengthened masonry

Performance of masonry elements externally strengthened with fiber reinforced polymers (FRPs) is intrinsically dependent on the bond behavior between the composite material and masonry substrate. Therefore, a sound understanding of the interface behavior is crucial at the design stage. In this paper, a three-dimensional model based on the smeared crack modeling approach is presented for investigating the bond behavior in FRP-strengthened masonry elements. The threedimensional aspects of bond behavior in FRP- strengthened masonry elements are investigated. Moreover, the effect of mortar joints in the bond behavior of strengthened masonry prisms is studie

Moisture effects on the bond strength of FRP-masonry elements

Moisture exposure has been observed to be one of the degrading environmental agents which affects the durability of the FRP-strengthened elements by changing the constituent material or bond properties. This paper presents the experimental investigation on the effects of moisture on the pull-off bond strength of GFRP-strengthened brick specimens. The specimens have been prepared following the wet lay-up procedure and exposed to constant moisture level of 100% R.H. at 23̊C for 8 weeks. The degradation in the bond performance has been investigated by performing pull-off tests on the conditioned specimens after 4 and 8 weeks of exposure. The reversibility of the bond degradation has been also studied by storing some specimens in the laboratory conditions for 1 week after conditioning and before performing the pull-off tests. Comparative analysis has been performed and the main results are presented and discussed

Numerical analysis of bond behaviour between masonry bricks and composite materials

Fiber Reinforced Polymers have become a popular material for external strengthening of masonry structures. The performance of this strengthening technique is strongly dependent on the bond between FRP and substrate. This paper presents numerical modeling of the bond behavior in FRP-strengthened masonry components using interface elements, based on a recent testing program at the University of Minho. A trilinear bond-slip model is proposed for the interface elements based on observed experimental behavior of strengthened components. The comparison between numerical and experimental results shows that the proposed model is suitable for numerical simulation of the bond behavior and allows a better understanding of the mechanisms involved in the failure process.This work was partly funded by project FP7-ENV-2009-1-244123-NIKER of the 7th Framework Programme of the European Commission, which is gratefully acknowledged. The experimental results mentioned in the paper were obtained within the framework of the RILEM TC 223-MSC activities, for which the authors are grateful

Numerical study of the role of mortar joints in the bond behavior of FRP-strengthened masonry

The performance of the interface between FRP and masonry is one of the key factors affecting the behavior of strengthened masonry elements. Therefore, a sound understanding of the interface behavior is crucial at the design stage. In this paper, the effect of mortar joints in the bond behavior of FRP-strengthened masonry prisms is investigated through numerical modeling. The numerical simulation is performed by adopting a nonlinear three-dimensional micro-modeling approach. Different smeared crack models are considered, and the results are compared in terms of local stress and strain distributions, global force–slip response, and cracking pattern. The accuracy of the FE predictions have been assessed by comparing the results with test data and it was found that three-dimensional FE modeling combined with a rotating smeared crack approach gives the best results, both at local and global levels. Finally, the numerical results obtained considering the presence of mortar joints with different mechanical properties are presented and critically discussed.This work was partly funded by Project FP7-ENV-2009-1-244123-NIKER of the 7th Framework Program of the European Commission, which is gratefully acknowledged. The first author also acknowledges the financial support of the Portuguese Science Foundation (Fundacao de Ciencia e Tecnologia, FCT), through Grant SFRH/BD/80697/2011

Water degrading effects on the bond behavior in FRP-strengthened masonry

Fiber reinforced polymers are being extensively used for external strengthening of masonry structures. However, durability of this strengthening technique under environmental conditions is still under inves- tigation. Previous studies indicate that moisture plays an important role in the durability of bond between FRP and substrate. Moisture can cause degradation in the bond behavior and also in the mechan- ical properties of the constituent materials. This paper presents and discusses the results of an experi- mental investigation on the effects of moisture on the bond behavior in FRP-strengthened masonry bricks. The degradation in the bond performance has been investigated by performing pull-off and pull-out tests on the conditioned specimens. The change in the mechanical properties of the materials has also been investigated. Comparative analysis has been performed and the results are presented and critically discussed.This work was partly funded by project FP7-ENV-2009-1-244123-NIKER of the 7th Framework Program of the European Commission, which is gratefully acknowledged. The first author also acknowledges the financial support of the Portuguese Science Foundation (Fundacao de Ciencia e Tecnologia, FCT), through grant SFRH/BD/80697/2011