Miloš Drdácký

Enhanced affordable methods for assessing material characteristics and consolidation effects on stone and mortar

It is rather difficult to set up non-destructive or considerate in situ tests for assessing material characteristics and consolidation effects on historic stone and mortar. However, some simple methods have proved to be helpful when applied appropriately and this paper provides brief information about two such methods: peeling tests, also known as the Scotch tape method, and surface water uptake measurements using a digitized microtube. Both methods have some history of development and use Mora and Torraca (1965 Bollettino Istituto Centrale del Restauro (Rome) pp 109–32), Giorgi et al (2000 Stud. Conserv. 45 154–61), Tiano et al (2006 J. Cult. Heritage 7 49–55), Lehmann (2004 Thesis, Hochschule fur Bildende Kunste, Dresden pp 33–34), Drdacký et al (2011 Proc. European Workshop on Cultural Heritage Preservation pp 126–30) and Zima (2011 Proc. 49th Int. Scientific Conf. on Experimental Stress Analysis pp 441–8) without any standardized support. This lack of a validated procedure can lead to some deficiencies and misinterpretations for applying the peeling test. Also, in the case of the digitized micro-tube, there can be some difficulties when the device is applied, which could prevent its wider adoption or even lead to rejection of the micro-tube technique. The paper summarizes basic principles for the application of both methods and reports illustrative results for laboratory and historic building investigations.

In Situ Compression Stress-Deformation Measurements along the Timber Depth Profile

The paper presents a novel concept and a prototype of a diagnostic tool for in-situ assessment of timber in existing structures and buildings. The device enables direct determination of conventional compressive strength and modulus of deformation in arbitrary depth along timber profile. The measurement of the stress-deformation relationship is performed in a prepared hole of a very small diameter by means of a special small size symmetrical loading jack. Testing and verification of the new device behaviour during loading of wood along the fibres has been carried out on fir which is the most frequent wood species in European buildings. The comparison of stress-strain diagrams acquired by means of the new device with those measured in compliance with the European standard for testing of wood shows a very good correlation including the determination of the compressive strength values. This semi-destructive method causes a very gentle damage and can be also used for the assessment of historic timber structures.

Hybrid Testing of Historic Materials

The paper describes hybrid approaches to testing of mechanical properties of historic materials which are mostly available in very small amounts and bulks unsuitable for standard testing procedures and techniques. Three case studies are presented. In all three, simple mechanical testing procedures were combined with special optical measurements and tailored software tools.

Experimental and numerical analysis of semi-destructive device for in situ assessment of wood properties in compression parallel to grain

A reconstruction of historical timber structures requires precise diagnostics of mechanical properties of particular structural members, which would subsequently underlie a reliable plan of the reconstruction. Mechanical properties of wood are determined most exactly using destructive techniques, but often they cannot be used in historical constructions. This calls for using nondestructive or semi-destructive techniques that are still reasonably exact, not too invasive and can be profitably used in situ. This work examines a new nondestructive diagnostic tool that enables to determine strength and stiffness parameters of wood parallel to the grain in situ. The function of the instrument was verified using standard compression tests parallel to the grain that correlated with the instrument well (rxa0=xa00.92). Complicated stress state in the drilled hole was examined by contact finite element analysis and revealed high contribution of longitudinal elastic moduli in force measurement (rxa0=xa00.96).

Torsional Shear Testing of Mortar

This paper presents a complex multidisciplinary approach to characterize the torsional shear on thin-walled cocciopesto lime mortar tubes. The approach employs (i) an in-house developed biaxial electro-mechanical loading frame designed for torsional loading, (ii) an optical measurement setup based on the digital image correlation technique to monitor and record the deformation during loading and (iii) a numerical model using finite element simulation to assess localization of shear failure. Prior to torsional loading, the mortar specimen needs to be firmly secured into the loading frame without exposing it to unwanted tensile or bending loading and possible crushing at fixture points. During the torsional loading, the mortar tube must be able to freely move axially. An optical measurement setup based on the digital image correlation technique allowed to quantify deformation measurements during torsional testing and provided the strain field on the observed surface. The mode of torsional failure was finally assessed from finite element simulations and compared to experimental measurements.

Soils and Earthen Building Materials Used for the Buddhist Temple Complex

ABSTRACT This article presents a comprehensive study of the local soils and historic earthen building materials used in Nako temple complex in Western Himalayas. On-site and laboratory investigations followed a holistic approach to characterize materials and identify historic manufacturing formulas. The interdisciplinary and novel methodology used for analysis of the earthen building materials combine geological, chemical, mineralogical, geotechnical, and mechanical approach. The results presented in this article enable a better understanding of material culture and advance the study of damage and decay processes found in the temple buildings. In addition, a suitable conservation and preservation strategy is presented.

Preventive Measures for the Protection of Architectural Heritage. Structures against Flooding

stände im Hinblick auf ihre besondere Gefährdung durch Hochwasser entwickelt wurden. Das historische Bauerbe wird hierfür in fünf Kategorien eingeteilt: 0: Gegen Hochwasser widerstandfähige Strukturen, 1: Strukturen aus Materialien mit hoher Volumenausdehnung bei Feuchtigkeit, 2: Konstruktionen aus Materialien, die bei Feuchtigkeit erheblich an Festigkeit einbüßen (einschließlich Böden), 3: Konstruktionen, die für partielle Schäden bei Hochwasser anfällig sind, und schließlich 4: Konstruktionen und Elemente, bei denen die Gefahr des Einsturzes oder des Wegschwemmens durch Hochwasser besteht. Für jede Kategorie und ihre typischen Schadensphänomene werden geeignete präventive oder restaurative Maßnahmen benannt, einschließlich einiger Empfehlungen zum generellen Risi-

Radiographical investigation of fluid penetration processes in natural stones used in historical buildings

In order to ensure sustainability if historic buildings their technical state has to be inspected on regular basis. Damage assessment has to be preferably carried out using non-destructive methods otherwise damage accumulation may occur during life-cycle of the constructions. According to character of detected damage appropriate intervention measures (i.e. strengthening, consolidation, etc.) have to be then efficiently applied. Among other factors significantly influencing life span of constructions weathering agents (rain, erosion, dissolution, etc.) may cause rapid degradation of mechanical properties. In this paper X-ray radiograhical imaging was used to describe fluid penetration process in porous Maastricht limestone that is commonly used for restoration purposes. The imaging was performed in custom radiography device simulating practical in-situ measurements using microtube device. This device is a modified Karsten tube capable of determining absorbed volume and its speed even on inclined surfaces. However actual fluid penetration process in terms of saturation depth/volume ratio and shape of fluid wave propagating through microstructure is indeterminable using microtube. For this purpose real-time radiography imaging of fluid saturation process was performed to investigate behaviour of fluid in the material. Furthermore X-ray computed microtomography was performed to develop finite element model for simulation of fluid flow in the porous microstructure. Using the real-time imaging relations between penetration speed, penetration depth and penetrated volume were assessed. These results can be used to validate results from microtube measurements including nonlinear regions present when semi-spherical wave propagates through the material. Using a set of finite element simulations of the microtube experiment fluid velocity distribution in the material together with effective Darcys flux were calculated and results were compared to those from real-time imaging.

Historical and Condition Survey of the St. Stefan Bulgarian Metal Church in Istanbul

This article presents data on the history, the material characteristics, and the present-day condition of a metal church structure built at the end of the 19th century in Istanbul. The facts have been acquired through several archive surveys, through investigations in situ, and through laboratory experiments in which a small sample of an original steel sheet was tested and compared to the original analysis. The all-metal building is one of a number of such churches built all over the world by leading steel workshop companies. The church in Istanbul was produced and assembled by the Rudolph Waagner Company in 1895–1896. The typology is compared with that of several other churches built in America and Europe. The present-day condition of the monument is strongly influenced by the unstable subsoil condition of the site and also by the quite aggressive exterior conditions (exposed to wind and salt) and interior conditions (a high level of water condensation). The structure therefore shows very high corrosion damage and very severe structural damage, mainly heavy cracks in the cast iron elements, loss of material, and subsidence of the foundations.