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Uranjek M.,University of Maribor | Uranjek M.,Building and Civil Engineering Institute ZRMK | Bokan-Bosiljkov V.,University of Ljubljana
Construction and Building Materials | Year: 2015

The research presented in this paper focuses on influence of freeze-thaw cycles accompanied by simultaneous moistening on mechanical properties of historical brick masonry. In order to evaluate the rate of reduction in mechanical properties of the masonry due to freezing and thawing, a series of brick wallets built of solid brick and lime mortar or lime-slag mortar representing an actual building envelope was subjected to testing. Besides testing the wallets and triplet specimens as a mortar-brick composite, mortar prisms and brick units were also tested separately. Wallets built with either of analysed types of lime-based mortar were able to withstand 50 freeze-thaw cycles without any effect on their mechanical properties. After 150 freeze-thaw cycles, the damage of brick surface and mortar joints increased, but had no significant effect on the compressive strength of the wallets. However, in case of wallets built with lime-slag mortar, freeze-thaw damage reflected in the reduction of modulus of elasticity. The results indicate that both tested mortar types have the potential in reconstruction and repair works carried out on historical masonry in areas exposed to freezing and thawing. © 2015 Elsevier Ltd. All rights reserved. Source


Krzan M.,University of Ljubljana | Gostic S.,Building and Civil Engineering Institute ZRMK | Bosiljkov V.,University of Ljubljana
Bulletin of Earthquake Engineering | Year: 2014

Within the framework of PERPETUATE project for the case study in Slovenia, the 150 year old Kolizej Palace in Ljubljana was set. The building was for a long time neglected and severely deteriorated due to ageing and moisture problems. Despite the overall opinion among conservators upon its preservation, it was set to be demolished. Prior it’s demolishing in 2011 extensive on-site investigation was carried out, which provided valuable data regarding the influence of deteriorated masonry on the seismic response of the building. Experimental tests proved almost completely saturated moisture conditions in the ground level of the building, while all the stories above were in almost dry condition. The results of tests on masonry revealed that moisture content and state of deterioration affected both strength and stiffness properties of built masonry in large extend. Regardless adopted modelling strategies the vulnerability assessment of the Kolizej Palace has proved that the building in its latest condition was far behind the current code requirements in respect to both static and seismic actions. © 2014, Springer Science+Business Media Dordrecht. Source


Krzan M.,University of Ljubljana | Gostic S.,Building and Civil Engineering Institute ZRMK | Cattari S.,University of Genoa | Bosiljkov V.,University of Ljubljana
Bulletin of Earthquake Engineering | Year: 2014

The structural performance of historical masonry elements can be understood provided the following factors are known: geometry; the characteristics of its masonry texture and morphology, state of damage and decay, physical, chemical and mechanical characteristics of the components (units, infill, mortar); the characteristics of built masonry as a composite material. In order to quantify the mechanical properties of the masonry both laboratory and in-situ tests are required. However, in the case of cultural heritage assets, the setting up of an effective knowledge procedure is strictly related to the minimization of invasiveness on the structure, with the aim of its conservation, rather than the cost–benefit optimization: thus it is essential to have available reference parameters to be adopted for different masonry types. Within this context, this State-of-the-Art paper on this topic is organized with integrated outcomes from the test campaigns carried out through the PERPETUATE project, that are also briefly presented. Reference parameters for effective seismic assessment are provided both for brick and stone masonry together with their upper and lower bound values for both mechanical parameters and damage limits for which proper limit states (LS) may be associated. Apart from the LS for structural elements (SE), the relevant LS’s for artistic assets attached to the SE are also presented in this paper. © 2014, Springer Science+Business Media Dordrecht. Source


Uranjek M.,Building and Civil Engineering Institute ZRMK | Bosiljkov V.,University of Ljubljana | Zarnic R.,University of Ljubljana | Bokan-Bosiljkov V.,University of Ljubljana
Materials and Structures/Materiaux et Constructions | Year: 2012

The injection of grout into multi-leaf stone masonry walls with a sufficient amount of voids can be an effective technique for the seismic strengthening of such walls. In order to evaluate the effectiveness of different types of commercial grouts that fulfilled the adopted criteria, the stone masonry walls of an actual building were strengthened by means of grout injection, using cement and combined cement-lime grouts. The quality and effectiveness of grout injection technique was assessed by non-destructive tests (sonic and radar tests), minor destructive tests (surface and in-depth probing and coring, and the double flat jack test), and destructive test (shear-compressive test), all in situ. Preliminary laboratory tests were also performed on mortar and stone specimens, on the injection grouts, and on cylinders representing the inner core of the strengthened walls. Finally, the seismic resistance of the building was evaluated in non-strengthened and strengthened variants (i.e. after grout injection of the walls with cement or lime-cement grout) by means of non-linear static analysis, using the pushover method. Obtained results show that shear characteristics of the walls (tensile strength and stiffness) depend significantly on the type and properties of the injected grout, i.e. on the grout's ability to achieve a solid bond between the stones and the leaves including the properties (strength and stiffness) of the grout itself. In the case of the type of masonry under consideration, an adequate level of seismic resistance can be achieved also by using combined cement-lime grouts, although cement grout can provide higher seismic resistance. © RILEM 2011. Source


Uranjek M.,Building and Civil Engineering Institute ZRMK | Bosiljkov V.,University of Ljubljana | Zarnic R.,University of Ljubljana | Bosiljkov V.B.,University of Ljubljana
RILEM Bookseries | Year: 2013

Most of the historical masonry buildings in Slovenia were built out of local stone or stone and brick with lime-based mortars. An efficient technique for improving the mechanical properties of stone or stone-brick walls is grout injection. In order to evaluate the quality and compatibility of commercially available injection grouts with materials present in historical masonry buildings, several types of hydraulic lime-pozzolana, lime-cement and cement grouts were tested. Chemical, physical and mechanical criteria to select optimal grout mixture for strengthening of historical masonry buildings were proposed, by which tested grouts were classified in three quality classes A, B and C. Only two commercial lime-cement grouts and one cement grout were able to meet the set requirements and were qualified in class B as medium quality grout (one lime-cement grout) or in class C as low quality grouts. Therefore, the design of hydrated lime-based grouts was carried out in continuation of our study, in order to obtain a grout that is highly compatible with the historical masonry in Slovenia. Among available limes, hydrated lime in powdered state and lime putty were used. Ground granulated blast furnace slag (GGBS), volcanic tuff, and limestone powder were used as mineral additives. It was found that the added combination of limestone powder and supplementary cementitious material (GGBS or tuff) has a beneficial influence on the properties of designed grout compositions. © RILEM 2012. Source

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