Masonry panels consisting of piers and spandrels in buildings are vulnerable to in-plane actions caused by seismicity and soil subsidence. Tectonic seismicity is a safety hazard for masonry structures, whereas low-magnitude induced seismicity can be detrimental to their durability due to the accumulation of light damage. This is particularly true in the case of unreinforced masonry. Therefore, the development of models for the accurate prediction of both damage initiation and force capacity for masonry elements and structures is necessary. In this study, a method was developed based on analytical modeling for the prediction of the damage initiation mode and capacity of stand-alone masonry piers; the model was then expanded through a modular approach to masonry walls with asymmetric openings. The models account for all potential damage and failure modes for in-plane loaded walls. The stand-alone piers model is applicable to all types of masonry construction. The model for walls with openings can be applied as is to simple buildings but can also be extended to more complex structures with simple modifications. Model results were compared with numerous experimental cases and exhibited very good accuracy.

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Reconstruction of historic building elements is often necessary in adaptive re-use projects. Optimally this is performed with as much original material as can be salvaged. However, the use of hydraulic lime mortars with no cement content in reconstructed masonry can lead to long curing time and excessive deformation under mechanical loads. Therefore, local masonry reconstruction in adaptive re-use projects using historic materials that need to adhere to pressing construction schedules should always be closely monitored. The objective of the paper is to demonstrate the need for accurate geometric survey of vault structures in order to achieve accurate deformation results using numerical analysis. Focusing on a complex reconstruction project involving a masonry vault at the Royal Academy of Fine Arts in Ghent, practical aspects of damage monitoring, geometric survey and computational analysis of historic structures are jointly presented and addressed. The vault was dismantled and reassembled using the original bricks and a newly made hydraulic lime mortar, the latter of which was mechanically characterized. Existing cracks in the masonry walls supporting the vault were monitored for the detection of new damage. Detailed geometric surveys were carried out using terrestrial laser scanning at two points in time after the reconstruction of the vault: a) before the removal of the formwork and b) after the removal. These scans are able to not only register the geometry of the vault in great detail, but also to measure the deflection of the structure under its self-weight non-intrusively and with good accuracy. Structural analysis of the vault has been carried out employing two approaches: a) by using simple geometric models of the vault and b) by using the detailed laser scanning data. Major differences between the two approaches are obtained in terms calculated deflection, highlighting the importance of detailed geometric survey for the analysis of historic structures. Detailed geometric survey data is shown to be critical in achieving accurate analysis results in structures whose deformation behaviour is mainly governed by their geometry.

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Induced seismicity due to gas extraction in the province of Groningen in the Netherlands has a noticeable impact on building structures. Historic masonry structures in the area, which are non-engineered and lacking empirical design features often present in traditionally seismic regions, are especially vulnerable to dynamic loading. Compounding the problem, gas extraction additionally generates soil settlement, which can induce damage to masonry buildings and thus reduce their capacity to bear seismic loads. The objective of this paper is the evaluation of the performance of a widely used structural intervention method applied in masonry structures in the Groningen region of the Netherlands. This method, initially developed against soil subsidence damage, consists in the embedment of stainless steel helical bars in repointed bed joints. Additionally, diagonal anchors are placed in drilled holes across existing cracks in the masonry. The increase in induced seismicity in Groningen raises the question whether this intervention technique can additionally enhance the behaviour of masonry structures during seismic loading. A masonry wall was experimentally tested in two configurations: a) a pre-damaged state, with simulated damage typical of imposed soil settlement, and b) a post-damaged and postintervention state, this being the wall from the previous configuration after being tested to its maximum base shear and subsequently strengthened. Differences between the two configurations in terms of stiffness, peak force and prevalent damage patterns are discussed. Accompanying the experimental campaign, results of finite element simulations of the strengthened wall are presented. The strengthened wall is simulated using non-linear macro-modelling techniques. The model accounts for the experimentally simulated damage as well as for the damage arising after the testing in the first configuration. The analysis results clarify and quantify the experimental observations on the strengthened wall, particularly as regards stress development and bond-slip in the reinforcement bars. Based on the experimental and numerical results, the effectiveness of the intervention in restoring the strength of the wall and in preventing the re-emergence of major diagonal cracking is confirmed.@en

The province of Groningen in the Netherlands is experiencing the continuous impact of gas extraction in the form of induced seismicity. Due to the absence of naturally occurring seismicity in the region, the historic building stock of Groningen was constructed without empirical design features typically encountered in naturally seismic regions. Further, gas extraction, in combination with soft topsoil, is responsible for substantial amounts of ground subsidence. This subsidence may compromise the capacity of existing structures to bear seismic loading. Historic masonry structures, particularly those lacking traditional earthquake-resistant features, are vulnerable to seismic loads. Further, their substantial weight, in-plane stiffness, low tensile strength and brittleness renders them vulnerable to settlement-induced damage. Given the cultural significance of architectural heritage, the performance of historic buildings in the Damage Limitation (DL) state is a matter of importance. Additionally, due to the incorporation of both vernacular and monumental architectural heritage buildings in the urban setting, their performance in the Near Collapse (NC) state is as important as that of ordinary building structures. Therefore, methods and techniques for enhancing the behaviour of historic buildings in both States need to be devised and evaluated. This paper focuses on the application and assessment of a retrofitting technique commonly used for damage prevention and repair in unreinforced masonry structures in the Netherlands, namely bed joint reinforced repointing. The technique consists in the embedment of stainless-steel bars in continuous bed joints, as well as their dry placement across cracks in the masonry. The technique is applied on a masonry wall tested under quasi-static cyclic in-plane shear loading for the evaluation of its performance not only in the DL state for which it was conceived, but also in the NC states. The wall features artificially introduced cracks that simulate settlement-induced damage prior to the installation of the bars. A finite element meso-model is used for the simulation of the wall tests, featuring the artificial damage and reinforcement elements. The model is used in non-linear cyclic analyses for the simulation of the experiments. Through experimental testing and numerical modelling, the efficiency of the strengthening technique is evaluated in terms of resulting shifts in wall capacity, stiffness and failure mode. Further comments are provided concerning its applicability and structural compatibility.

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In the present work, the effective elastic modulus of carbon nanotube (CNT) polymer nanocomposites has been evaluated through micromechanics modeling and finite element analysis (FEA). In the micromechanics model, the inherent trend of CNTs to aggregate is taken into account, considering a two-phase material system, that of the matrix with the finely dispersed CNTs and the inclusions, involving agglomerated CNTs and matrix material. A new model is proposed for the elastic stiffness evaluation of the two phases and the elastic stiffness of the nanocomposite, introducing two aggregation parameters. It was proved that this analysis was rational and operative. The same aggregation concept has been investigated using FEA, and a comparative study between the two procedures was performed. Furthermore, an additional treatment with FEA was performed, based on a three-phase model, including the matrix, the CNTs and the interphase. A parametric analysis has been executed and a comparison with experimental data of linear low density polyethylene (LLDPE)/CNT nanocomposites has been performed.@en

Historic masonry structures are particularly sensitive to differential soil settlements. These settlements may be caused by deformable soil, shallow or inadequate foundation, structural additions in the building and changes in the underground water table due to the large-scale land use change in urban areas. This paper deals with the numerical modeling of a church nave wall subjected to differential settlement caused by a combination of the above factors. The building in question, the church of Saint Jacob in Leuven, has suffered extensive damage caused by centuries-long settlement. A numerical simulation campaign is carried out in order to reproduce and interpret the cracking damage observed in the building. The numerical analyses are based on material and soil property determination, the monitoring of settlement in the church over an extended period of time and soil-structure interaction. A sensitivity study is carried out, focused on the effect of material parameters on the response in terms of settlement magnitude and crack width and extent. Soil consolidation over time is considered through an analytical approach. The numerical results are compared with the in-situ observed damage and with an analytical damage prediction model.

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Differential soil settlements can induce structural damage to heritage buildings, causing not only economic but also cultural value losses. In 1963, the Saint Jacob’s church in Leuven was permanently closed to the public because of severe settlement-induced damage caused by insufficient bearing capacity of the foundation. Currently, the church is stabilized using a temporary shoring system. This work aims at implementing a practical modelling approach to predict damage on church nave walls subjected to differential settlements. For that purpose, a finite element model of the Saint Jacob’s church nave was generated and validated through on-site monitoring data including levelling, damage survey and laser scanning. The model takes into account the non-linear behavior of the masonry by means of continuum smeared cracking. The paper introduces two approaches to model the settlement on the structure. One of them consists in the direct application of vertical displacements underneath the structure according to the deformation profile measured on-site. In the second approach, interfaces with different stiffness are placed at the base allowing the structure to deform under its self-weight. In addition, the effect of the settlement profile type in the damage level is analyzed.

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Limited experimental data of mechanical properties of brick masonry are available in the literature, especially for those properties that determine the cracking behaviour, such as tensile strength and fracture energy. Moreover, the cracking behaviour is influenced by several other factors such as the type of components, bond type, size of the element and loading conditions. Therefore, the aim of this paper is to determine properties of the masonry composite as a function of the properties of its components. The proposed methodology uses numerical analyses to obtain the material properties of a continuum smeared cracking model from discrete cracking models loaded in different directions. For that purpose, discrete cracking meso-models of masonry panels are subjected to tension and compression to numerically determine the stress-strain curves and the mechanical properties of the composite. For evaluation, material properties for the meso-models are taken from laboratory testing and from the literature. For model calibration, experimental tests on bricks, mortar and couplets are performed. The laboratory testing includes compression tests on masonry panels monitored with digital image correlation (DIC). Parameters such as the Young's modulus, tensile strength and tensile fracture energy for the masonry composite are determined for loading applied parallel and perpendicular to the bed joints.@en