Key Engineering Materials Vol. 628

Abstract: The paper describes a study carried out for historical centre of Faenza (RA), developed by the Dept. of Architecture (UniCT) within an agreement with Faenza Municipality. The study aimed at elaborating guidelines for mitigation of buildings’ vulnerability in historical urban fabric to be used in ordinary government of the city as seismic prevention intervention.

Abstract: The structure of many historical buildings relies on unreinforced masonry load-bearing walls. In the case of large slenderness or significant eccentricity of the vertical compressive loads the mechanism formation failure mode is likely. Considering the second order bending effects and the tensile strength of the masonry is essential to accurately calculate the load-bearing capacity of these structures, which is required for maintenance tasks. An analytical methodology has proposed with this aim. This original method, the Southwell plot method and the formulations from two standard codes (ACI-530 and Eurocode-6) are applied to calculate the resistance of 18 experimentally tested walls to conclude that the proposed methodology brings correct results, the standards are conservative and the Southwell plot method is the most suitable for the analysis of the considered cases but it is not always applicable.

Abstract: In 2003, people working in the San Luzi, Zuoz, bell tower reported excessive tower vibrations when ringing bells. Zuoz is a village in the Upper Engadin Valley, Switzerland. Measurements performed in 2004 showed a maximum tower vibration velocity amplitude of 16 mm/s which is more than five times the acceptable value ([1], [2], [3]). In 2008 the two large bells (out of four) were equipped with cranked yokes and their pendulum frequency was reduced to get a larger distance to the tower natural frequency. Measuring again in 2009 yielded the two large bells no longer exciting large tower vibrations. However, this was not true for bell No. 3. Subsequently, this bell's pendulum frequency was also reduced. In 2011, measurements showed that this last measure had negative instead of positive effects. And, now disposing of three values, the tower natural fundamental frequency was found to be somewhere in the f = 1.43...1.50 Hz region. It was then decided to monitor the tower dynamic behavior for one year to get reliable information on the natural frequency scatter. Monitoring started June 11, 2012, and ended October 7, 2013. The results: a) The tower fundamental frequency varied in an f = 1.42...1.59 Hz range, b) The tower is stiffer in winter than in summer, c) On a daily or weekly schedule, the tower fundamental frequency is following the temperature curve: increasing stiffness with increasing temperature and vice versa. A possible explanation for this contradiction is given. Due to space restrictions, also monitored bell ringing excited tower vibrations can not be discussed here.

Abstract: The surveys following severe earthquakes show that existing unreinforced masonry buildings are highly vulnerable to local collapse mechanisms. However, their assessment is strongly sensitive to the choice of the mechanism, whose boundary conditions are largely unknown. In the past the mechanism has been selected based on the crack survey alone, because the survey of the deformations is very difficult if traditional tools are used. In the last years advanced survey techniques have been developed, the most powerful of whom resorts to laser scanning. A laser scanner allows the acquisitions of a very large amount of information: building overall dimensions and single elements detailed survey, detection of anomalies, and identification of very limited deformations undetectable with the naked eye. Moreover, contrary to traditional procedures, it allows the survey of the façades without any direct contact with the building, which could be damaged after an earthquake. A laser-scanner survey has been performed in the whole historical centre of Rovere, in the municipality of Rocca di Mezzo, affected by the 2009 L’Aquila earthquake. This survey has been used to study the façades of three different building units, recognising the collapse mechanism triggered by the earthquake ground motion. The mechanisms are fairly different from what suggested by the crack pattern alone and pertain to deformations that cannot be recognised in the photos. Moreover, the faithful geometric models that can be generated from laser scanning allow accounting for deformations and out-of-plumb. Thus, the acceleration activating the mechanism can be estimated much more accurately compared to a perfectly vertical and parallelepiped wall.

Abstract: In this paper, the use of ultrasonic pulse velocity (UPV) testing as a reliable technique to determine the compressive strength of a calcarenitic stone typical of Salento (South of Italy), known as Lecce Stone (LS) has been investigated. The scope of the experimental research is to establish correlations between the results obtained by non-destructive and destructive tests, in order to reduce the use of destructive methods within the diagnostic procedures for the mechanical analysis and qualification of ancient masonries. Furthermore, the presence of water as a variable affecting the test was investigated. The results of the tests show that the UPV values are well correlated with the compressive strengths and this method showed to be efficient in predicting the strength of LS.

Abstract: This paper - the first of two companion papers [1] - focuses on some considerations about the issue of the knowledge of masonry buildings in aggregate, which aims at evaluating the safety and, at the same time, the preservation inquiry of this built heritage.

Abstract: This paper is the second one of two companion papers [1] that deal with the experience carried out in the post-seismic reconstruction plans activity in the Abruzzo region done by the research groups of the University of Catania (Coord. C.F.Carocci) and University of Genoa (S. Lagomarsino). In particular, this paper focuses on the issues related to the choice and use of the most suitable modeling strategies and analysis methods to perform the seismic assessment at scale of buildings in aggregate. Both recurring seismic responses of masonry, that is the global one and the local mechanisms, are considered. The strong complementarity with the knowledge phase, faced in detail in [1], is discussed by illustrating an application based on the use of an analytical mechanical model for the in-plane response and that of Macro Block model for the out-of-plane response.

Abstract: The outcomes of an in-situ experimental campaign in the context of the seismic assessment of 71 existing road bridges belonging to the Veneto regional roadway network have been described. An in-situ and laboratory experimental campaign on basic materials was carried out with the aim of characterizing the main mechanical material parameters of each bridge. Structural assessment has been subsequently carried out, comparing the obtained results with those deriving from a preliminary analysis conducted on the basis of some assumptions on materials’ mechanical characteristics related to the original design documents and the construction practice at the time of the structures’ edification.

Abstract: We characterize the elastic response of Apricena marble by using advanced ultrasonic nondestructive techniques. An innovative experimental device for ultrasonic immersion tests is employed for the determination of ultrasonic velocities of waves travelling into the sample for any angle of propagation. The interpretation of the experimental results within the theoretical framework of wave propagation in elastic materials allows for both the classification of the anisotropy and the determination of the elastic moduli.

Abstract: This paper presents a structural analysis of a masonry chimney built in the 1940s, which is currently being cataloged as local interest heritage. This structure has not served any industrial purpose for the last thirty years. The chimney is located in the town of Agost (Alicante - Spain) and directly exposed to the prevailing winds from the sea, as it is approximately 12 km away from the waterfront and there are not any significant barriers, which could protect the structure against the wind. There are longitudinal cracks and fissures all along the shaft because of the chimney’s geometrical characteristics, the effect of the masonry creep and especially the lack of maintenance. Moreover, there is also a permanent bending deformation in the upper 1/3 of the height due to the wind pressure. A numerical analysis for the static behavior against gravity and wind loads was performed using the structure’s current conditions after a detailed report of its geometry, its construction system and the cracking pattern. Afterwards, the dynamic behavior was studied, i.e. a seismic analysis using both response spectra and accelerograms in order to examine the structural stability. This work shows the pre-monitoring analysis before any experimental testing. Using the current results the future test conditions will be determined (e.g. number of sensors and monitoring point location, excitation systems, etc) prior to a possible structural reinforcement by applying composite material (fiber reinforced polymers).