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This paper focuses on the unidirectional dynamic shake-table test performed on a prototype of a natural stone masonry building aggregate. The half-scale prototype was designed to reproduce the features of existing unreinforced stone masonry building aggregates, typical of the historical centres in many European cities, including the city of Basel, Switzerland. The three-storey-high aggregate prototype consisted of two weakly connected structural units, with double-leaf undressed stone masonry walls incorporating a limited percentage of river pebbles. The specimen included flexible timber floor diaphragms and side-gabled timber roofs with different heights above the two units. Scaling the material mechanical properties of the specimen was necessary to satisfy similitude relationships without altering accelerations and material densities. An incremental, unidirectional dynamic test was performed up to near-collapse conditions of the prototype, using input ground motions selected to be compatible with realistic seismic scenarios for the region of Basel. This paper summarizes the main characteristics of the specimen and illustrates the evolution of its dynamic response and damage mechanisms. [ABSTRACT FROM AUTHOR]

Masonry walls are typically subjected to eccentric compressive loadings in common buildings. However, the design of walls towards this type of solicitation remains very empirical, often leading to oversizing the structure. This is especially true for natural stone masonry, for which experimental data are quite scarce. This paper presents an experimental campaign on 15 natural stone masonry wallettes subjected to centred and eccentric compression until failure. Different values of the eccentricity of the load, ranging from h /12 to h /4 (where h is the thickness of the wallette) were investigated, highlighting the noticeable effect of such a value on the compressive failure load. During the tests, the displacements were recorded by a Digital Image Correlation system, providing insights into the different failure mechanisms that depend on the value of the eccentricity. The so-obtained experimental failure loads are then compared to the predictions of Eurocode 6. Finally, a finite-element yield-design analysis of these tests is proposed which shows that this modelling framework is suitable to find the ultimate bearing capacity of a masonry wallette. • The greater the eccentricity of a compressive load, the lower the failure load. • Two types of failure mechanisms were identified depending on the eccentricity value. • Eurocode 6 underestimates the compressive strength of the wallettes by a 3.4 factor. • Experimental results corroborate the eccentricity correction factor from Eurocode 6. • 3D yield design provides accurate predictive results. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and numerical study on different retrofit solutions for stone masonry buildings with timber diaphragms in earthquake-prone regions, aiming at enhancing wall-to-diaphragm connections, diaphragms’ stiffness, and masonry properties. The experimental results of incremental dynamic shake-table tests on three full-scale two-story buildings, complemented by material and component characterization tests, are initially summarized. The first building specimen was unstrengthened. The second one was retrofitted at the floor and roof levels with improved wall-to-diaphragm connections and a moderate increase in diaphragm stiffness. Connections were also improved in the third specimen together with a significant enhancement of diaphragm stiffness. The calibration of two numerical models, versus the experimental response of the retrofitted building specimens, is then presented. The models were further modified and reanalyzed to assess the effects of masonry mechanical upgrades, which could be achieved in practice through deep joint repointing or various types of jacketing. These solutions were simulated by applying correction coefficients to the masonry mechanical properties, as suggested by the Italian building code. The effectiveness of the experimentally implemented and numerically simulated interventions are discussed in terms of strength enhancement and failure modes.

A unidirectional shake-table test was performed on the half-scale prototype of a natural stone masonry building aggregate, to investigate the seismic performance of this type of historical construction and to assess the effectiveness of two retrofit solutions. The specimen represented a building aggregate with two adjacent three-storey units, connected along one side as if they were built at different times. Double-leaf stone masonry with undressed blocks and river pebbles was used for the walls. Timber floors constituted flexible diaphragms in their planes. Roofs with different timber truss configurations and heights covered the two units. Improved wall-to-diaphragm connections and tie rods were pre-installed, although initially not fastened, on the prototype. Both retrofit systems were activated after significant damage was reached testing the unstrengthened specimen. This paper describes the seismic behaviour of the prototype, focusing on the effects of the retrofit interventions on damage mechanism evolution, lateral displacement demand, hysteretic response, and dynamic properties degradation. [ABSTRACT FROM AUTHOR]

Cathedral Church of St Mary, Erfurt – repair and restoration of the vaulted arches The medieval master builders of Erfurt created two churches that are inseparately linked with the city and its history – the collegiate churches of St Mary and Severus – on the Cathedral Hill, or Domberg, both impressive examples of Gothic church design that are famous far beyond the borders of Thuringia. What is unusual here is the Cathedral Hill, "mons Sancti Severi – mountain of Saint Severus", sloping away steeply to the east and enclosed by massive, multi‐storey substructures in the form of vaulted arches. In addition to the impressive history of the construction, this article also describes the latest repair measures to support the vaulted arches. After an analysis of the structural condition and the formulation of the repair objectives, the stone restoration and the renewal of the upper structure are explained. Finally, the experimental load‐bearing capacity evaluation carried out as part of the building measures is discussed. [ABSTRACT FROM AUTHOR]

The ÖBB-Infrastruktur AG operates and maintains 246 tunnels and similar structures with an overall length of approx. 250 km. Nearly 150 of these structures are more than 100 years old, 35 of them are over 150 years old. Ageing processes, the impact of train traffic, ground conditions and environmental conditions are causing progressive damage to the tunnel linings, which - in order to maintain safe railway operation - requires ongoing maintenance procedures. Those procedures are carried out under a range of restrictions concerning availability, which is one of the most important principles at the ÖBB after safety. In order to obtain continuous availability of the facility, new methods of refurbishment were developed for the two double-track tunnels Rekawinkler Tunnel and Kleine Dürreberg. The described methods enabled extensive repair works of the tunnels, mostly with uninterrupted train traffic on the second track. [ABSTRACT FROM AUTHOR]

• The evolution of natural stone masonry stiffness exposed to multi-level cyclic load is revealed. • A novel secant modulus-based failure prediction method is proposed. • A constitutive model is proposed to characterize stone deformation under multi-level fatigue load. Stiffness loss and catastrophic failure frequently occur in natural stone masonry subject to freeze–thaw action and cyclic stress, which may incur serious engineering disasters and casualties. This work strives to experimentally unveil the mechanical responses of a medium-grained building sandstone exposed to dual effects of freeze–thaw and cyclic stress. Testing results are presented from the insights of volumetric deformation, secant modulus evolution. A drop in secant modulus of the first cycle is observed in the failure cyclic loading stage, whereas all former stages exhibit a modulus increase. This precursor well applies to all samples which is freeze–thaw and stress level independent. The development of Poisson's ratio as well as stress level at onset of volume reversal are also presented. A theoretical modelling is put forward to characterize the axial and circumferential strains exposed to variable cyclic stress. The model shows decent effectiveness calibrated by testing results, the way to determine constants in models is introduced in detail, which can be used by readers in a broader range of construction materials. [ABSTRACT FROM AUTHOR]

For many years it has been realised that the weathering of stone is not merely determined by physical and chemical factors but also by biological agents. When the stone in question is a historic building or monument, the damage done constitutes an irretrievable loss of our heritage and history. Laboratory studies have commenced in Paisley to study the effect of photoautotrophs on the major sedimentary rock forming minerals, with a view to expanding this work to study the overall effect of these micro-organisms on heritage masonry. Tests were carried out on Albite, Calcite, Dolomite, Orthoclase, Siderite and Quartz, using axenic cultures of the following: Chlorella vulgaris, Chlorococcum tetrasporum, Scenedesmus obliquus, Oocystis marsonii, Stichococcus bacillaris. The rock chips were immersed in either water or bolds basal media and exposed to a mix of the micro-organisms listed above and then tested weekly for their pH, fortnightly for the waters chemical composition using inductively coupled plasma-atomic emission spectrometry (ICP-AES) and visually utilising the university’s SEM facilities. Work so far has revealed biologically mediated etching of minerals, a well-defined pH profile over a period of 90 days, as well as a variety of elemental release patterns for the different minerals. [ABSTRACT FROM AUTHOR]

This paper presents an experimental and numerical study on different retrofit solutions for stone masonry buildings with timber diaphragms in earthquake-prone regions, aiming at enhancing wall-to-diaphragm connections, diaphragms' stiffness, and masonry properties. The experimental results of incremental dynamic shake-table tests on three full-scale two-story buildings, complemented by material and component characterization tests, are initially summarized. The first building specimen was unstrengthened. The second one was retrofitted at the floor and roof levels with improved wall-to-diaphragm connections and a moderate increase in diaphragm stiffness. Connections were also improved in the third specimen together with a significant enhancement of diaphragm stiffness. The calibration of two numerical models, versus the experimental response of the retrofitted building specimens, is then presented. The models were further modified and reanalyzed to assess the effects of masonry mechanical upgrades, which could be achieved in practice through deep joint repointing or various types of jacketing. These solutions were simulated by applying correction coefficients to the masonry mechanical properties, as suggested by the Italian building code. The effectiveness of the experimentally implemented and numerically simulated interventions are discussed in terms of strength enhancement and failure modes. [ABSTRACT FROM AUTHOR]