Search Results (49)

Historic masonry towers represent a significant part of the cultural heritage, which is often subject to retrofitting for preservation purposes. Due to the poor quality of the mortar, if present at all, the connection of existing towers to the foundation is generally such that it cannot ensure their monolithic behaviour under seismic action. When choosing a retrofitting technique, engineers often find themselves in a dilemma, whether to strengthen the connection between the tower and the foundation in order to enable the transfer of bending moments from the tower to the foundation due to seismic action, or to leave the towers freely rested on the foundation in order to enable the rocking motion mechanism. The aim of this paper was to investigate how the connection between the tower and the foundation affects the seismic resistance of masonry towers. For this purpose, a series of numerical analyses were performed on 2D numerical models that were created based on the geometry of five towers from the Italian region. In these numerical analyses, each of the towers is subjected to an incremental dynamic analysis in time for the case that it is freely supported on the base and for the case that it is freely rested base. The numerical analyses showed that: (i) unretrofitted towers have relatively low seismic resistance and rocking mechanisms cannot be realised to a significant extent; (ii) retrofitted masonry towers resting freely on the base have a significantly higher seismic resistance compared to the same towers connected to the base due to the rocking motion mechanism. The conclusions drawn on the basis of the conducted studies can serve engineers when choosing a technique for strengthening masonry towers. Full article

The church of Saint Felix in Girona (Spain) is crowned by an octagonal bell tower with a stone pinnacle at each corner. It was built using dry-joint stone masonry, a technique that involves laying stones in a precise pattern to create a solid and durable structure. In order to strengthen the connection between the stone blocks of the pinnacles, a wooden bar was placed through a central hole carved in the stone structure. Today, the inner structure has completely disappeared. During maintenance and repair work, it was decided to restore the functionality of the disappeared reinforcement by installing a titanium bar in its place. Due to the uncertainty associated with the pinnacle’s behaviour and the lack of both, a proper numerical model of the monument, and an extensive characterization of the materials, a strategy based on multiple approaches was designed. The proposed strategy was based on combining numerical and experimental models, the final objective being to determine the length and mechanical properties of the metallic inclusion, considering the effects of gravity, wind, and seismic forces. A scale model of the pinnacle was evaluated in laboratory conditions. The results were used to calibrate a numerical model representing the scale specimen. After calibration, the results were extrapolated to a full-scale numerical model. The experimental and numerical results showed that the pinnacles needed to be reinforced along their entire height. The tensile stresses cause by wind and seismic forces at different levels, could not be compensated without the contribution of the titanium bar inserted into the pinnacle. Full article

Bell towers, due to their slender geometry and structural configuration, are among the buildings most susceptible to deterioration from weathering and seismic events. These aspects influence the structural assessment of these historic towers, which is essential for their conservation and maintenance. The “Carmine Maggiore” bell tower in Naples (Italy) has been an important and prominent landmark of the city for centuries. It is square in plan and 72 m high. Over time, it suffered extensive damage and was severely damaged by the earthquake of 1456. Reconstruction began in the first decade of the 17th century and the original design was modified, adding two stories and changing the shape of the plan to octagonal. In the centuries that followed, the structure was damaged again and further interventions were carried out, adding tie-rods and replacing damaged elements. Today, the bell tower has very elaborate façades with mouldings and decorations, so that the supporting structure appears to be covered with plaster, stucco, and stone elements. This paper describes the results of FEM analyses of the bell tower, obtained from models with different levels of complexity to evaluate the influence of stone cladding elements on the seismic behaviour. In particular, the difference in the IS safety indices, calculated as the ratio of capacity to demand, exceeds 15%, due to the mechanical consistency of the cladding elements, which contribute significantly to both stiffness and strength. Full article

The Beyazıt Tower, located within the Beyazıt Campus of İstanbul University, was chosen as a reference structure to assess its dynamic characteristics due to its historical significance. The tower, which is a historic masonry structure, was analyzed using the finite element method with shell and solid 3D models. Ambient vibration tests were conducted to evaluate the accuracy of the analysis results. Based on the findings from the experimental study, the numerical models were updated, and the most suitable material properties were identified. The accuracy of the analysis results among the different models was also discussed. Additionally, a foundation was established for long-term monitoring studies by determining the dynamic characteristics through experimental methods. These studies will help identify any changes that may occur over time, allowing for the monitoring of potential damage and the detection of any impacts from natural disasters or human activities on this unique structure. Full article

The seismic assessment of historical masonry bell towers is of significant interest, particularly in Italy, due to their widespread presence and inherent vulnerability given by their slenderness. According to technical codes and standard practice, the seismic evaluation of masonry bell towers can be conducted using a range of methodologies that vary in their level of detail. This paper presents a case study of a historical masonry bell tower located in the Caserta Province (Italy). Extensive investigative efforts were undertaken to determine the tower’s key geometric and structural characteristics, as well as to document ongoing damage phenomena. The dynamic behavior of the tower was assessed through ambient vibration testing, which enabled the identification of the principal modal shapes and corresponding frequencies, also highlighting peculiar dynamical characteristics caused by the damage conditions. Subsequently, the seismic assessment was carried out using both Level 1 (simplified mechanical) and Level 2 (kinematic limit analysis) methodologies. This assessment helped identify the most probable collapse mechanisms and laid the foundation for employing more advanced methodologies to design necessary retrofitting interventions. The study emphasizes the importance of Level 2 analyses for structures where out-of-plane failure mechanisms are likely due to pre-existing cracking. Both approaches provide less-than-unity acceleration factors, ranging from 0.45 for Level 1 (assuming non-ductile behavior) to 0.59 for Level 2, in this case specifically using the information available about existing cracking pattern. Full article

Masonry towers are peculiar structures with complex structural behavior despite biased conclusions deriving from their geometrical regularity and simplicity. Their geometrical features and the epistemic uncertainty that masonry material bears strongly influence their static and seismic behavior. This paper investigates a remarkable and representative case study. The bell tower of Portogruaro (Italy) is a 57 m high tall construction, built in the XII-th century, and has a notable inclination. The Italian Guideline for the safety assessment of masonry towers is a key focus in this paper, highlighting the pros and cons of different suggested approaches. Some relevant proposals are presented in this paper in order to address the seismic safety assessment of masonry bell towers. The findings show that very slender structures do not meet the guidelines recommendations due to limitations in their current stress state. In addition, in similar cases, the recommended values for the mechanical properties of masonry material led to predicting non-withstanding structural behavior, questioning the correct choice of the adapted material properties. Advanced pushover analysis has been conducted in order to investigate the results of the simplified approach in terms of failure patterns and seismic safety estimation. The simulations are implemented for four different hypothetical scenarios of the existing masonry mechanical properties. The results obtained for the case study tower reflect a different perspective in the seismic assessment of masonry towers when specific approaches are defined. The preliminary results on the safety of Portogruaro Tower show a significant variability of seismic safety based on the adopted scenario, highlighting the necessity to pay attention to the preservation state of the present case and of similar ones. Full article

This paper presents research concerning the numerical simulation of existing masonry buildings when subjected to pushover analysis. A nonlinear static analysis is undertaken using the commercial software ABAQUS standard, in which masonry structures are modelled using damage mechanics. To validate the chosen input parameters, this study compares two different approaches for static nonlinear modelling, the Finite Element Method (FEM) and the Equivalent Frame Method (EFM), for a simple masonry building. The two methods are compared using the guidelines from Part 3 of Eurocode 8. This study identifies the advantages and disadvantages of various modelling approaches based on the results obtained. The results are also compared in terms of capacity curves and damage distributions for the simple case study of a masonry building created to compare numerical methods. Subsequently, nonlinear pushover analyses with ABAQUS (FEM) were performed on the North Tower of Monserrate Palace, Portugal, in which the material parameters were calibrated by considering the results of dynamic characterisation tests conducted in-situ. Regarding the circular body of Monserrate Palace, the damage distribution of the structure is analysed in detail, aiming to contribute to the modelling of such structural configurations through the Equivalent Frame Method. Full article

This paper focuses on the reliability of a synergistic procedure, involving dynamic tests complemented by documentary and architectural research, for the structural assessment of heritage towers. The reliability of the presented method is exemplified in a relevant case study, the Zuccaro’s Tower in Mantua. As is known, historic buildings require addressed procedures in order to consider past building transformation and eventual damage/decay, which can affect the masonry properties and, more generally, the structural behavior. The proposed investigation procedure is based on multidisciplinary information (i.e., merging data) from historical and document studies, direct inspections, surveys of geometry and front surfaces, and dynamic tests in operational conditions. The processed information allowed the development and the calibration of a simplified numerical model, useful in driving the seismic/structural assessment of the tower. The results of past investigations, found during the archival research, contributed to the structural evaluation. This paper describes the main research outcomes and the model tuning with a special focus on the key role of the synergy between the applied methods for the assessment of a historic building. Full article

In this study, modal and structural identification of a historic masonry bell tower in Čuntići, Croatia, damaged during the recent Petrinja earthquake, was performed. The results of the ambient vibration tests (AVT) and operational modal analysis (OMA) were used to update the finite element numerical model of the bell tower. Three modes were experimentally determined: the first two were bending modes (f₁ = 4.395 Hz and f₂ = 4.639 Hz), and the third was a torsional mode (f₃ = 10.303 Hz). The experimentally determined and the originally calculated (preliminary NM) modal shapes agreed well, but in terms of modal frequencies, the correlation was poor. After model updating, some structural parameters were identified, and a reliable finite element numerical model was established. The proposed method can provide a reliable evaluation of the structural parameters of historic masonry buildings. Full article

The fundamental frequency plays a primary role in the dynamic assessment of Cultural Heritage towers. Local and global features may impact its value: geometric, material features, interaction with the soil and adjacent buildings, aging, the construction phase, and repairs. A database is assembled to study the relationship between the fundamental frequency and the slender masonry structure features. Empirical and physics-based approaches were developed to assess the fundamental frequency from different sources of information. A Rayleigh–Ritz approach is proposed and compared with a 3D finite element model. A sensitivity analysis is then performed to quantify the contribution of each feature. As expected, it is shown that the height of the tower contributes the most to the fundamental frequency. The other tower features have a second-order impact on both the fundamental frequency and the mode shape. A comparison between the different approaches shows that the Rayleigh–Ritz drastically minimizes the difference between numerical and experimental frequencies when all information is available. Empirical relations are a good compromise when less information is available. Full article

This paper presents the path of knowledge developed for assessing the structural safety of the Norman-age Pisan Tower, which is mostly incorporated into the Royal Palace in Palermo, Italy. Historical, geomatic, and mechanical investigations were conducted and the most relevant results are herein collected and presented. The research path was addressed to specific tasks: identification of the building, geometric surveys, recognition of the sequence of phases of building transformation, detection of the components of the load-bearing structure, structural diagnostic surveys, and investigation of the subsoil and foundations. The explicit vulnerabilities found were mostly confined to the Piazzi library floor, while implicit vulnerabilities were identified in the presence of false walls and in high loads and fillings on the vaults of the last levels. The results of the analyses allowed the individuation of the confidence factors to use in structural analysis models aimed at the assessment of the seismic safety of the building. Full article

The Tower of Hercules is an icon of the city where it is located, A Coruña, and it is supposed to be the world’s only surviving Roman lighthouse. Its function continues today: it provided a warning to shipping in antiquity and continues to do so now, in the 21st century. Furthermore, it is a paradigmatic case of architectural intervention in an ancient monument: in the 18th century, the Spanish engineer Eustaquio Giannini restored the tower, applying scientific criteria and maintaining the authenticity of the monument. For all these reasons, the Tower of Hercules is an exceptional benchmark through which the development and evolution of the different signaling and navigation aid systems can be studied from the beginning of our era to the present day. Full article

The construction of the tunnels of Metro Line 4 and Gulou Station in central Nanjing poses a potential threat to the nearby historic building, Gulou Tower, due to the relatively small spacing and the deteriorated structure behaviors. Two aspects are important for the protection of Gulou Tower: (i) reducing the soil movement caused by the tunnel–station construction and (ii) increasing the total stiffness of this sensitive building. This research first presents the main features of two tunnels and the triple-arch tunnel as the connection between the two tunnels and Gulou Station. The details of the excavation means and construction procedures of the tunnels, together with the engineering measures that tend to reduce soil disturbance during tunnel excavation, are presented. Meanwhile, to improve the overall stiffness of Gulou Tower, additional support for the masonry terrace and the upper timber structure is also discussed. Moreover, the construction procedures of the tunnels and the station that could influence the settlement development of Gulou Tower are also suggested. The measured ground settlement and structure displacement are found to be limited to the allowable values, indicating that the aforementioned protective measures are adequate to protect hybrid timber–masonry historical structures nearby tunneling. Full article

In seismic-prone areas, ecclesiastical masonry complexes have shown very high vulnerability, as detected after the last Italian earthquakes, such as those that occurred in L’Aquila (2009), Emilia-Romagna (2012), Central Italy (2016), and Ischia (2017). Partial collapses often affect these types of aggregate buildings due to the presence of highly vulnerable elements, such as bell towers. Preliminary analyses, including straightforward and quick methods, are necessary to assess their vulnerability. This paper proposes a simplified method to analyse bell tower dynamic behaviour and the results obtained are compared with several different approaches. The first is based on the dynamics of two rigid blocks (bell tower and lower building), and the second concerns a single block (bell tower only). The proposed method can be considered as a quick procedure involving few parameters to provide a preliminary analysis before use of more complex models such as finite element models. It aims to provide a valuable tool for the initial evaluation of the stability and risk index of the structure. The double-block model considers the associations between the rocking of the bell tower and the sliding motion of the underlying building. A parametric evaluation for different friction coefficients is proposed. The results are represented as rotation time histories and compared with analysis of the single vulnerable element, i.e., the bell tower subjected to the floor spectrum. The results show that high excitation frequency and friction coefficient values make the bell tower stable, and that the simplified model provides a clear safety advantage. Full article

Resonance frequencies of a masonry bell tower were estimated by means of ambient noise measurements and compared with those computed by using fixed base, Winkler, and FE numerical, including subsoil. Given the geological complexity that characterizes the subsurface of the analyzed area, despite the presence of massive volcanic outcrops near the bell tower, we carried out a geophysical characterization of the subsoil by using active and passive seismic surveys. These surveys have identified a soft substrate underneath the construction; for this reason, the dynamic identification of the tower was performed, including the interaction with the soil. The resonance frequencies of the masonry bell tower computed by the models are very similar to those obtained using ambient noise. Results suggest that building resonance frequencies, estimated by ambient noise surveys, can be used because of their reliability especially when quick analyses are required at historical buildings located in seismically active areas needing plan actions to reduce their vulnerability. Moreover, such analyses, being performed on samplings acquired within the structure, allow for estimating its dynamic response, taking into account the effect of subsurface characteristics as well. Full article