Numerical models for seismic assessment of historic structures

The knowledge of the structural behaviour of existing masonry requires a multilevel approach, with proper application of different diagnostic and assessment methodologies. The paper presents successful application of the results of in-situ tests on modelling the behaviour of historical structures. In order to obtain reliable material parameters for the application of different numerical models, different test methodologies a combination of Destructive Tests (DT), Minor Destructive Tests (MDT) and Non-Destructive Tests (NDT) were performed. Following this, two different models were applied for the assessment of seismic resistance of Pišece Castle – structural element model (SEM) for non-linear seismic analysis and 3D finite element model (FEM) for linear analysis by means of modal response spectrum analysis. The results of numerical analysis provided valuable information of the loadbearing capacity of structures, their seismic resistance as well as possible causes for the observed crack patterns

Vulnerability Study of Urban and Rural Heritage Masonry in Slovenia Through The Assessment of Local and Global Seismic Response of Buildings

Uncertainties regarding the influence of modelling strategies for the evaluation of seismic vulnerability of\ud masonry buildings in Slovenia were studied on two case studies– damaged buildings from the rural area of NW\ud Slovenia hit by earthquakes in ’98 and ’04 and the urban buildings from the old city centre of Ljubljana. Two\ud strategies were applied – failure mechanisms analysis by means of FaMIVE methodology and non-linear\ud response analysis by means of storey and global response (SREMB and 3Muri). The accuracy in predicting\ud failure modes by FaMIVE was 50% considering the stock of investigated building in rural area. The most critical\ud failure mechanisms were due to out-of-plane loading. For urban architecture, in-plane failure due to weak\ud spandrels was the predominant one. The mechanism assessment yields more conservative results in respect to\ud non-linear approach and thus may be an efficient tool for the design of strengthening measures for heritage\ud buildings to prevent damage in lower intensity events with higher probability of occurrence

Influence of Ageing and Deterioration of Masonry on Load Bearing Capacity of Historical Building

Numerous heritage buildings in the former Eastern Europe that were neglected in the past are severely deteriorated due to ageing and moisture problems. The paper summarizes experimental and numerical work carried out on 150 yrs. old Kolizej Palace in Ljubljana (Slovenia) which has recently been demolished, despite the overall opinion among conservators that it should be preserved. Experimental tests proved almost completely saturated 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 that extend so that the previous estimations and calculations regarding the state of the structure and its static load bearing capacity were too optimistic. Both storey and global response non-linear seismic analysis have proved that building in its current condition is far below the current seismic code requirements

Seismic resistance of stone masonry building and effect of grouting

Injektiranje je jedan od najdjelotvornijih, a često i najprikladnijih postupaka za ojačanje zidova starih zidanih građevina. Da bi se ocijenio utjecaj raznih vrsta injekcijskih smjesa na mehanička svojstva zidanih građevina, obavljeno je ispitivanje in situ postojeće zidane građevine. Dobiveni rezultati korišteni su za ocjenu seizmičke otpornosti građevine pomoću metode postupnog guranja, uz primjenu pristupa katnog mehanizma i mehanizma globalnog odziva. Prihvatljivije vrste injekcijskih smjesa usporedive su s cementnim injekcijskim smjesama. Dobiveno je da se pristupom globalnog odziva postižu realniji rezultati čak i kod niskih zidanih građevina.Grout injection is one of the most effective and often most appropriate techniques for strengthening of old stone masonry walls. In order to assess the influence of different types of injection grouts on the mechanical properties of masonry, an actual stone masonry building was tested in-situ using various testing methods. The results obtained were used to evaluate seismic resistance of a building using the pushover method, and considering the storey mechanism approach and the global response mechanism. More compatible types of grouts can match cement grouts. The results show that the global response approach provides more realistic results even for low-rise masonry buildings

Testing and analysis of walls strengthened with FRP

U radu je opisana usporedba laboratorijskih i terenskih ispitivanja na posmik zidova ojačanih karbonskim (C) trakama i staklenim (G) mrežicama u polimerima s rezultatima proračunskih modela za zidove s FRP-om. Rezultati ispitivanja na zidovima od nove i stare pune opeke pokazali su povećanje posmične nosivosti i graničnog pomaka - najviše za horizontalne i horizontalno-vertikalne epoksidom zalijepljene trake te mrežice u modificiranom cementnom mortu, a najmanje za dijagonalne trake zbog odstupanja sa zida. ACI i CNR računski modeli pokazali su najbolje podudaranje s eksperimentima.Laboratory and in-situ shear tests of walls strengthened with Carbon FRP (Fiber Reinforced Polymer) strips and Glass FRP grid were compared to the results of different calculation models for masonry with FRP. Tests on new and old solid brick specimens showed an increase in shear strength and ultimate displacement. The best results were obtained with horizontally and horizontally-vertically epoxy-bonded strips and modified cement mortar grid configurations, worse with diagonal strips due to peeling failure. ACI and CNR calculation approaches showed the best agreement with experimental results

In-plane seismic behaviour of ashlar three-leaf stone masonry walls

In light of the forthcoming second generation Eurocodes (EC), the results of conducted systematic in-plane cyclic and compressive tests on three-leaf stone masonry walls are discussed following new requirements and provisions. The new proposal for EC8-3 for existing buildings is based on partial factors safety approach, though it considers different uncertainties in defining input parameters for effective seismic performance-based assessment. Prior to its application, massive calibration effort will be needed since there is no standardized method for shear testing of masonry walls. In this paper, the performance limit states damage, resistance, and displacement capacities from conducted test results were evaluated and assessed through comparison with analytical solutions and imposed limit values, as stated in existing codes. The test results provide a much higher deformation capacity than the limits provided in both existing and new proposal of EC8-3 as well as those in the ASCE code provisions. The reason for this lies in the soft, "ductile" mortar for which the presumed resistance according to code provisions should be significantly higher when considering good quality ashlar three-leaf stone masonry

The relation between concrete, mortar and paste scale early age properties

Microstructure development of concrete, mortar, and paste scale of cement-based material (CBM) during the early hydration stage has a significant impact on CBM%s physical, mechanical, and durability characteristics at the high maturity state. The research was carried out using compositions with increased autogenous shrinkage and extended early age period, proposed within the RRT+ programme of the COST Action TU1404. The electrical conductivity method, used to follow the solidification process of CBM, is capable of determining the initial and final setting time, and the end of the solidification process acceleration stage for the paste and mortar scale. Simultaneous ultrasonic P- and S-wave transmission measurements revealed that the ratio of velocities VP/VS is highly dependent on the presence of aggregates%it is considerably higher for the paste scale compared to the mortar and concrete scale. The deviation from the otherwise roughly constant ratio VP/VS for each scale may indicate cracks in the material. The non-linear correlation between the dynamic and static elastic moduli valid over the three scales was confirmed. Additionally, it was found that the static E-modulus correlates very well with the square of the VS and that the VS is highly correlated to the cube compressive strength%but a separate trendline exists for each CBM scale

Application and properties of pure lime façades - case study

The paper presents experiences obtained during application and testing of different pure lime façades that could be successfully used in restoration of historical buildings in Slovenia. The lime façade consists of a rendering layer (rough mortar), a finishing layer (fine mortar) and a protective layer of lime wash. For the design of the mortars different industrially and traditionally produced limes were chosen, based on the results of preliminary studies of the authors and experiences of a small enterprise (SE) involved in the study. The façade layers were applied to the most problematic northern wall of the historic chapel made from rubble masonry. The chapel belongs to the castle Crnelo, built at the end of the 17th century in the village Turnše, not far from Ljubljana, the capital of Slovenia. The façade layers were made by skilled workers of SE, with about one year time difference between application of rendering and finishing layers, and with a protective layer of coloured lime wash applied to one to three day old finishing layers. On the rendering layers, visual inspection, water absorption tests and determination of carbonation depth were carried out before subsequent finishing layers were applied. The same on-site tests were carried out also on finished façade layers. So far, parallel to the on-site tests, compressive and water absorption tests on prisms prepared from rough mortars were carried out in laboratory

Vulnerability Study of Urban and Rural Heritage Masonry in Slovenia Through The Assessment of Local and Global Seismic Response of Buildings

Uncertainties regarding the influence of modelling strategies for the evaluation of seismic vulnerability of masonry buildings in Slovenia were studied on two case studies- damaged buildings from the rural area of NW Slovenia hit by earthquakes in ʼ98 and ʼ04 and the urban buildings from the old city centre of Ljubljana. Two strategies were applied - failure mechanismsanalysis by means of FaMIVE methodology and non-linear response analysis by means of storey and global response (SREMB and 3Muri). The accuracy in predicting failure modes by FaMIVE was 50% considering the stock of investigated building in rural area. The most critical failure mechanisms were due to out-of-plane loading. For urban architecture, in-plane failure dueto weak spandrels was the predominant one. The mechanism assessment yields more conservative results in respect to non-linear approach and thus may be anefficient tool for the design of strengthening measures for heritage buildings to prevent damage in lower intensity events with higher probability of occurrence

Compression and in-plane seismic behaviour of ashlar three-leaf stone masonry walls

There is a lack of knowledge regarding the parameters needed for the effective seismic performance assessment of historical stone masonry buildings. The paper presents the results of an extensive experimental campaign consisting of four compression and fifteen in-plane cyclic shear tests on three-leaf ashlar stone masonry walls and its constituents. The morphology, level of vertical load, and testing boundary conditions were systematically varied, and their influence on the load-bearing and deformation capacities, stiffness, ductility and energy dissipation was analysed. Good consolidation of the inner core enables in-plane failure mechanism of the walls to occur without decisive out-of-plane damage. The boundary conditions applied significantly influence the failure modes and large deformation capacities obtained, whereas transverse connections in the case of a shear failure mechanism do not significantly influence the overall lateral in-plane response of walls