scholarly journals Monitoring historical masonry structures with operational modal analysis: Two case studies

2010 ◽  
Vol 24 (5) ◽  
pp. 1291-1305 ◽  
Author(s):  
L.F. Ramos ◽  
L. Marques ◽  
P.B. Lourenço ◽  
G. De Roeck ◽  
A. Campos-Costa ◽  
...  
Keyword(s):  
Modal Analysis ◽  
Case Studies ◽  
Operational Modal Analysis ◽  
Masonry Structures ◽  
Historical Masonry

scholarly journals Effects of Structural Parameters on Seismic Behaviour of Historical Masonry Minaret

2017 ◽  
Author(s):  
Barış Erdil ◽  
Mücip Tapan ◽  
İsmail Akkaya ◽  
Fuat Korkut
Keyword(s):  
Modal Analysis ◽  
Structural Parameters ◽  
Masonry Structure ◽  
Operational Modal Analysis ◽  
Shear Cracks ◽  
Seismic Behaviour ◽  
New Model ◽  
The Core ◽  
Historical Masonry ◽  
Stiffness Distribution

The October 23, 2011 (Mw = 7.2) and November 9, 2011 (Mw = 5.6) earthquakes increased the damage in the minaret of Van Ulu Mosque, an important historical masonry structure built with solid bricks in Eastern Turkey, resulting in significant shear cracks. It was found that since the door and window openings are not symmetrically placed, they result in unsymmetrical stiffness distribution. The contribution of staircase and the core on stiffness is ignorable but its effect on the mass is significant. The pulpit with chamfered corner results in unsymmetrical transverse displacements. Brace wall improves the stiffness however contributes to the unsymmetrical behaviour considerably. The reason for the diagonal cracks can be attributed to the unsymmetrical brace wall and the chamfered pulpit but the effect of brace wall is more pronounced. After introducing the cracks, a new model was created and calibrated according to the results of Operational Modal Analysis. Diagonal cracks were found to be likely to develop under earthquake loading. Drifts are observed to increase significantly upon the introduction of the cracks.

scholarly journals Determination of characteristic Parameters of masonry Structures via Operational Modal Analysis

2019 ◽  
Vol 12 (3) ◽  
Author(s):  
Ali Koçak ◽  
Burak Toydemir ◽  
Melih Bulgur
Keyword(s):  
Modal Analysis ◽  
Operational Modal Analysis ◽  
Physical Models ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Model Parameters ◽  
Masonry Structures ◽  
Characteristic Parameters ◽  
Characteristic Model

Commonly, material and vibration characteristics of masonry structures remain uncertain in the evaluation of existing structures under external loads such as earthquake, heat, wind, etc. In addition, determination of compressive and tensile strength of a masonry walls is not straightforward. However, it is very important to know the characteristic parameters such as eigen values, periods and mode shapes of a structure beforehand in order to create accurate and reliable physical models. Since each historical structure has its own unique wall and bearing characteristics, it is not possible to accept random initial values for the bearing capacity and other parameters of the structure. Besides, conducting vertical and lateral loading experiments is costly and time consuming. An alternative way to determine these parameters that govern the structural behavior is to carry out experimental vibration tests using accelerometers. This method, which is also called as Operational Modal Analysis (OMA), is used to obtain the free and forced vibration response of structures by experimental means and to determine the modal parameters of the structure. OMA is very important for the appropriate use of an analysis method and the model parameters used in the analysis. In this study, two masonry buildings, one of which is historical, are discussed and the modal parameters of buildings are determined experimentally with OMA. Characteristic values obtained from OMA were compared with the three dimensional finite element method by adjusting characteristic model parameters.

scholarly journals Seismic Assessment in a Historical Masonry Minaret by Linear and Non-linear Seismic Analyses

2020 ◽  
Author(s):  
Emin Hökelekli ◽  
Ali Demir ◽  
Emre Ercan ◽  
Halil Nohutçu ◽  
Abdurrahman Karabulut
Keyword(s):  
Finite Element ◽  
Modal Analysis ◽  
Dynamic Properties ◽  
Ground Motions ◽  
Element Model ◽  
Operational Modal Analysis ◽  
Finite Element Models ◽  
Non Linear ◽  
Concrete Damage ◽  
Historical Masonry

Operational Modal Analysis (OMA) method is frequently used in order to determine dynamical properties of historical masonry structures. In this study, damage pattern of historical Alaca minaret which is selected as application is investigated under different ground motions by updating finite element models (FEM) depending on operational modal analysis test. Initial Finite element model was prepared in ABAQUS V10 program and numerical dynamic characteristics of minaret were determined. In addition, experimental dynamic properties of minaret were provided by operational modal analysis. Initial numerical model of brick masonry structure was calibrated via OMA method. Then, linear and non-linear seismic analyses of calibrated FEM of historical minaret were performed by using different earthquakes acceleration records that occurred in Turkey. Concrete Damage Plasticity model was taken into account in non-linear seismic analyses. As a result of the analyses, it is concluded that the stresses obtained with linear analyses aren’t as realistic as the non-linear analyses results and the earthquakes can cause some damages in the minaret.  

scholarly journals Operational Modal Analysis: A Tool for Assessing Changes on Structural Health State of Historical Constructions after Consolidation and Reinforcement Works—Jura Chapel (Jerez de la Frontera, Spain)

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Manuel Romero ◽  
Pablo Pachón ◽  
Víctor Compán ◽  
Margarita Cámara ◽  
Francisco Pinto
Keyword(s):  
Modal Analysis ◽  
Dynamic Properties ◽  
Operational Modal Analysis ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Health Improvement ◽  
Health State ◽  
Structural Behaviour ◽  
Structural Health ◽  
Historical Masonry

Today’s society is sensitive to the architectural heritage conservation. This implies to perform works to maintain these buildings and to assure their structural security. In the last years, the structural analysis of historical masonry constructions has experienced a great progress, thanks to the use of techniques based on the study of the dynamic properties of building structures. In this context, changes on the structural health state of a building are one of the elements that can be assessed considering changes on their dynamic properties. This is useful to evaluate the effectiveness of structural interventions on this kind of buildings by analysing these properties before and after it. This paper focuses on the Jura Chapel, in Jerez de la Frontera (Spain). This chapel is part of San Juan de los Caballeros Church and is dated from the 15th century. In 2015 and after the identification of some structural damages in the chapel vault, an intervention was initiated to improve its structural behaviour and to recover its original appearance. The present work reports the evaluation of the effects that this intervention has on the structural health state of the building, using nondestructive techniques based on ambient vibration tests (AVT) and Operational Modal Analysis (OMA). The AVT were performed for both prerestored and restored states and under environmental loads. A discussion about the validity of doing AVT from extrados when a vault presents disconnection between ribs and web is included in the paper. As a result, the first five natural frequency values have increased while the corresponding mode shapes have not changed significantly. This proves a structural health improvement caused by the repairing process without changing the original behaviour of the structure. This work shows OMA capabilities for evaluating the effectiveness of intervention works on the health state of a historical masonry structure.

Structural Health Monitoring of a Historical Masonry Bell Tower Using Operational Modal Analysis

2017 ◽  
Vol 747 ◽  
pp. 440-447 ◽  
Author(s):  
Elisa Bassoli ◽  
Marianna Forghieri ◽  
Loris Vincenzi ◽  
Marco Bovo ◽  
Claudio Mazzotti
Keyword(s):  
Modal Analysis ◽  
Monitoring System ◽  
Structural Response ◽  
Operational Modal Analysis ◽  
Evolutionary Strategy ◽  
Fe Model ◽  
Structural Behaviour ◽  
Structural Health ◽  
Bell Tower ◽  
Historical Masonry

This paper addresses the modal and structural identification of the historical masonry bell tower of Ficarolo, in Italy. After the seismic sequence of May 2012, the tower reported a serious damage pattern. Retrofitting interventions were designed and they mainly consisted in the rebuilding of cracked zones and the strengthening of masonry walls with carbon bars embedded in the masonry with epoxy resin. Afterwards, a continuous dynamic monitoring system has been installed on the tower. From the recorded structural response under ambient excitation, the dynamic characteristics of the tower are identified using Operational Modal Analysis techniques. Results of the first months of continuous monitoring are presented in this paper. Moreover, in order to analyse the evolution of the structural behaviour, the effect of changing temperature on the identified natural frequencies is investigated. The experimental modal parameters are also used to identify the elastic modulus of the reinforced masonry through the calibration of a Finite Element (FE) model of the tower. In addition, the influence of the soil-foundation system on the structural behaviour is evaluated. The calibration procedure is performed adopting an improved surrogate-assisted evolutionary strategy. The calibrated FE model can be adopted to simulate the structural response to far-field earthquakes. Moreover, the monitoring system can give valuable information on the structural behaviour and the structural health in the case of seismic events.

Operational Modal Analysis of Torsional Modes in Rotating Machinery

2014 ◽  
Vol 137 (2) ◽  
Author(s):  
Eoin Peter Carden ◽  
Mattias Lindblad
Keyword(s):  
Modal Analysis ◽  
Case Studies ◽  
Rotating Machinery ◽  
Operational Modal Analysis ◽  
Modal Testing ◽  
Damping Factor ◽  
Industrial Practice ◽  
Marine Propulsion ◽  
Lateral Modes ◽  
Marine Propulsion System

Traditional experimental modal testing techniques rely on controlled and measured excitation together with measured responses in order to identify the mode shape, natural frequency, and damping factor of each mode. Applying a controlled and measured excitation to a rotor train when in operation is logistically difficult and especially challenging in the field. Operational modal analysis (OMA) identifies the modal parameters of a system from measurement of response due to some (unknown) excitation. OMA has proven successful over the past several decades on nonrotating structures but has relatively rarely been applied to rotating machinery. Case studies are presented demonstrating the use of OMA in identifying torsional modes on an electric motor driven reciprocating compressor, on a diesel engine driven fire water pump, and on a marine propulsion system. In contrast to lateral modes, torsional modes of rotor trains are typically not speed dependent. However, phenomena exist whereby the torsional modes may be different at stand still, off-load and at different loads. The case studies provide examples of such phenomena and also of significant differences between predicted and measured behavior which suggests that improvements in industrial practice would be beneficial. Such improvements should be based on reconciliation of measured and predicted behavior and OMA offers a valuable tool to facilitate this. OMA provides a significant benefit in investigating and understanding torsional behavior in operation.

Operational Modal Analysis of Torsional Modes in Rotating Machinery

2014 ◽  
Author(s):  
Eoin Peter Carden ◽  
Mattias Lindblad
Keyword(s):  
Modal Analysis ◽  
Case Studies ◽  
Rotating Machinery ◽  
Operational Modal Analysis ◽  
Modal Testing ◽  
Damping Factor ◽  
Industrial Practice ◽  
Marine Propulsion ◽  
Lateral Modes ◽  
Marine Propulsion System

Traditional experimental modal testing techniques rely on controlled and measured excitation together with measured responses in order to identify the mode shape, natural frequency and damping factor of each mode. Applying a controlled and measured excitation to a rotor train when in operation is logistically difficult and especially challenging in the field. Operational modal analysis (OMA) identifies the modal parameters of a system from measurement of response due to some (unknown) excitation. OMA has proven successful over the past several decades on non-rotating structures but has relatively rarely been applied to rotating machinery. Case studies are presented demonstrating the use of OMA in identifying torsional modes on an electric motor driven reciprocating compressor, on a diesel engine driven fire water pump and on a marine propulsion system. In contrast to lateral modes, torsional modes of rotor trains are typically not speed dependent. However phenomena exist whereby the torsional modes may be different at stand still, off-load and at different loads. The case studies provide examples of such phenomena and also of significant differences between predicted and measured behaviour which suggests that improvements in industrial practice would be beneficial. Such improvements should be based on reconciliation of measured and predicted behaviour and OMA offers a valuable tool to facilitate this. OMA provides a significant benefit in investigating and understanding torsional behaviour in operation.

Synergistic application of operational modal analysis and ambient noise deconvolution interferometry for structural and damage identification in historic masonry structures: three case studies of Italian architectural heritage

2019 ◽  
Vol 19 (4) ◽  
pp. 1250-1272 ◽  
Author(s):  
Enrique García-Macías ◽  
Alban Kita ◽  
Filippo Ubertini
Keyword(s):  
Modal Analysis ◽  
Case Studies ◽  
Ambient Noise ◽  
Damage Identification ◽  
Operational Modal Analysis ◽  
Bell Tower ◽  
Wave Velocities ◽  
Historic Structures ◽  
Deconvolution Interferometry

Conservation techniques within the framework of structural health monitoring, particularly through dynamic measurements and operational modal analysis, are becoming popular for condition-based maintenance and decision-making in historic structures. Nonetheless, while effective for giving insight into the overall behaviour of structures, these techniques may fail at detecting local damages with limited effects on the modal features of the system. In this regard, the analysis of propagating waves throughout the structure poses an attractive alternative for data-driven damage identification. Specifically, some encouraging results have been reported on the application of seismic interferometry to reinforced concrete structures, albeit the number of works concerning ambient vibrations is far scarce, and practically nonexistent in the realm of historic structures. In this light, this article explores the synergistic application of operational modal analysis and ambient noise deconvolution interferometry for the structural identification of historic structures through three different case studies, namely the Sciri Tower in Perugia, the Consoli Palace in Gubbio and the bell-tower of the Basilica of San Pietro in Perugia. The first case study represents a typical example of a masonry tower inserted into a building aggregate, while the second one constitutes a particular case of a monumental masonry palace. The presented results and discussion cover diverse aspects of the identification of wave velocities, signal processing strategies, effects of dispersion and robustness of the identification. Finally, the case study of the bell-tower of the Basilica of San Pietro illustrates the application of operational modal analysis and deconvolution interferometry for damage identification. To do so, two different ambient vibration tests conducted before and after the 2016 Central Italy seismic sequence are studied. The results show concentrated reductions in the wave velocities in the area of the belfry, which demonstrates that deconvolution interferometry constitutes a complementary technique to operational modal analysis for damage localization and, to some extent, damage quantification.

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