A review on acoustic emission monitoring for damage detection in masonry structures

Acoustic emission monitoring is widely used for damage detection in materials research and for site monitoring. Its use for masonry structures is however challenging due to the highly heterogenic nature of masonry and rapid signal attenuation. However, the non-invasive nature and high sensitivity of the technique also provide interesting opportunities, especially for historical masonry structures, to locate damage, identify severity of damage and rate of deterioration. Aim of this paper is to provide an extensive literature review on the application of the acoustic emission technique for masonry structures, addressing specific challenges and recent findings. AE-based methods for damage assessment in masonry are discussed in view of monitoring approaches, wave propagation, source location and crack development under static, fatigue and creep loading. Site applications are discussed for identifying crack location and crack propagation in historical masonry towers, buildings and masonry arch bridges. The paper concludes with future challenges identified in this research field

Soil Settlement and Uplift Damage to Architectural Heritage Structures in Belgium: Country-Scale Results from an InSAR-Based Analysis

Soil movement may be induced by a wide variety of natural and anthropogenic causes, which are detectable in the local scale, but may influence the movement of the soil over vast geographical expanses. Space borne interferometric synthetic aperture radar (InSAR) measurements of ground movement provide a method for the remote sensing of soil settlement and uplift over wide geographic areas. Based on this settlement and uplift evaluation, the assessment of the potential damage to architectural heritage structures is possible. In this paper an interdisciplinary monitoring and analysis method is presented that processes satellite, cadastral, patrimonial and building geometry data, used for the calculation of settlement and uplift damage to architectural heritage structures in Belgium. It uses processed InSAR data for the determination of the soil movement profile around each case study, of which the typology is determined from patrimonial information databases and the geometry is calculated from digital elevation models. The impact on the historic structures is calculated from the determined soil movement profile based on various soilstructure interaction models for buildings. The resulting damage is presented in terms of a numerical index illustrating its severity according to different criteria. In this way the potential soil movement damage is quantified in a large number of buildings in an easily interpretable and user-friendly fashion. The processing of InSAR data collected over the previous 3 decades allows the determination of the progress of settlement- and uplift-induced damage in this time period. With the integration of newly acquired and more accurate data, the methodology will continue to produce results in the coming years, both for the evaluation of soil settlement and uplift in Belgium as for introducing related damage risk data for existing architectural heritage buildings. Results of the analysis chain are presented in terms of potential current damage for selected areas and buildings

Research developments at K.U.Leuven for diagnostics and restoration of historical masonry

This contribution deals with the ongoing research topics related to diagnostics and restoration of historical masonry. For damage assessment, the focus is on masonry subjected to long term high stress levels and the resulting damage accumulation caused by creep effects. The Acoustic Emission technique is evaluated as a NDT to quantify the damage evolution. To have a better understanding of the brick-mortar interaction the collapse mechanism of masonry is studied by means of micro-focus X-ray imaging. The available test setup allows 3D tomographic imaging of the damage pattern during compressive tests on small scale samples. A comparative study of the collapse mechanism of the same brick with different mortar types is aimed at. Related to consolidation measures, the technique of grout injection is often applied for brick masonry structures. Its applicability towards earthen structures is looked for. Within a preliminary phase, the design requirements are addressed.status: publishe

Semi-automated Creation of Accurate FE Meshes of Heritage Masonry Walls from Point Cloud Data

© 2019, RILEM. The structural analysis of buildings requires accurate spatial models. Additionally, spatial information on pathologies such as settlement-induced damage is paramount in the assessment of heritage assets. This spatial information is used as a basis for Finite Element Methods (FEM) to evaluate the stability of the structure. Traditional data acquisition approaches rely on manual measurements which are labor intensive and error prone. Therefore, major simplifications are made to document structures efficiently. The goal of this research is to provide faster and more accurate procedures to capture the spatial information required by a Finite Element (FE) mesh. This paper presents a semi-automated approach to create accurate models of complex heritage buildings for the purpose of structural analysis. By employing remote sensing techniques such as terrestrial laser scanning and photogrammetry, a complex mesh of the structure is created. Also, a methodology is proposed to capture crack information. A stepwise approach is elaborated to illustrate how the spatial information is adapted towards a FE mesh. The results show a significant difference between the geometry of our model and a traditional wire-frame model. Not only does accurate modelling result in deviating loads, it also affects the behavior of the object. Through the proposed approach, experts can develop highly accurate FE meshes to assess the stability of the structure up to as-built conditions and taking into account existing damage patterns.status: publishe