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CONTENTS
Volume 4, Number 2, March 2008
 

Abstract
Shape memory alloys (SMA) have been emphasized, studied and understood in the controlled world of the laboratory. Any attempt to implement one of these alloys in engineered products requires a jump from the controlled world of the laboratory to the actual environment of the application. The first step is to move from single grain specimens to multigrain samples. One works with a material for which any stock is different from that previously available. This paper reviews the milestones in the familiarization process the authors had to overcome during their cooperation within a project funded by the European Union. The main items cover transformation temperatures, thermal treatment and properties understanding.

Key Words
shape memory alloys testing specimens; thermal treatment; transformation temperatures; vibration mitigation.

Address
Fabio Casciati; Department of Structural Mechanics, University of Pavia, Pavia, Italy
Casper van der Eijk; SINTEF Material and Chemistry, 7465 Trondheim, Norway

Abstract
Damping capacity of SMA damping devices is simulated numerically under distinct geometry and loading conditions. Two-dimensional numerical simulations are performed on the basis of a phenomenological model of dynamics of martensite-austenite phase boundaries. Results of the simulations predict the time delay and the value of the stress transferred to other parts of a construction by a damper device.

Key Words
shape-memory alloys; martensitic phase transformation; moving phase boundary; numerical simulation; specific damping capacity.

Address
Arkadi Berezovski; Centre for Nonlinear Studies, Institute of Cybernetics at Tallinn University of Technology,
Akadeemia tee 21, 12618 Tallinn, Estonia

Abstract
The work presented in this paper includes material characterisation and an investigation of suitability in seismic dampers for two commercially available NiTi-alloys, along with a numerical analysis of a new damper system employing composite NiTi-wires. Numerical simulations of the new damper system are conducted, using Brinson

Key Words
shape memory alloys; NiTi; seismic damper; pseudoelasticity; WIND-CHIME; numerical simulation; design principles; residual strain; one-dimensional constitutive model; parameter study.

Address
J. S. Olsen; Norwegian University of Science and Technology, 7491 Trondheim, Norway
C. Van der Eijk; SINTEF Materials and Chemistry, 7465 Trondheim, Norway
Z. L. Zhang; Norwegian University of Science and Technology, 7491 Trondheim, Norway

Abstract
The use of pre-tensioned shape memory alloy (SMA) wires to retrofit historic masonry structures is investigated. A small wall, serving as a prototype masonry specimen, is constructed to undergo a series of shaking-table tests. It is first studied in its original state, and its dynamic characteristics (in terms of modal frequencies) are extracted from the recorded signals. The results are then compared with those obtained when an increasing number of couples of pre-stressed SMA wires are introduced in the specimen to link the bricks together. A three-dimensional finite element model of the specimen is developed and calibrated according to the modal parameters identified from each experimental test (with and without SMA wires). The calibration process is conducted by enhancing the masonry mechanical behaviour. The results and the effectiveness of the approach are presented.

Key Words
masonry; numerical modelling; shaking table tests; shape memory alloys; system identification.

Address
Sara Casciati; ASTRA Department, School of Architecture, University of Catania, Siracusa, Italy
Karim Hamdaoui; Department of Structural Mechanics, University of Pavia, Pavia, Italy

Abstract
In this paper, a methodology for the estimation of masonry elasticity and shear moduli is presented, for linear elasticity considerations. The methodology is based on the assumption that for a

Key Words
modulus of elasticity; shear modulus; masonry; microanalysis; finite element method.

Address
Institute of Structural Analysis and Aseismic Research, National Technical University of Athens,
9, Iroon Polytechniou st., GR15773, Zografou Campus, Athens, Greece

Abstract
An important historical monument of Cyprus is an aqueduct that was built in 1747 to provide water to the city of Larnaca and to its port. Because of its importance to the cultural heritage of Cyprus, the aqueduct has been selected as one of the case-study monuments in the project Wide-Range Non-Intrusive devices toward Conservation of Historical Monuments in the Mediterranean Area (WIND-CHIME). Detailed drawings of the aqueduct obtained from the Department of Antiquities of Cyprus have been used for the development of a computational model. The model was fine-tuned through the measurement of the dynamic characteristics of the aqueduct using forced and ambient vibrations. It should be noted that measurement of the dynamic characteristics of the structure were performed twice in a period of three years (June of 2004 and May of 2007). Significant differences were noted and they are attributed to soil structure interaction effects due to seasonal variations of the water-level in a nearby salt-lake. The system identification results for both cases are presented here. This monument was used to test the effectiveness of shape memory alloy (SMA) pre-stressed devices, which were developed during the course of the project, in protecting it without spoiling its monumental value.

Key Words
health monitoring; shape-memory-alloy; monuments; masonry structure seismic-protection; system-identification; model updating.

Address
Christis Z. Chrysostomou; Higher Technical Institute, PO Box 20423, 2152 Nicosia, Cyprus
Themos Demetriou; Cyprus University of Technology, PO Box 50329, 3603 Limassol, Cyprus
Andreas Stassis; Higher Technical Institute, PO Box 20423, 2152 Nicosia, Cyprus

Abstract
This paper summarizes the experimental vibration-based structural health monitoring study on a historical monument in Jordan. In this work, and within the framework of the European Commission funded project

Key Words
vibration-based health monitoring; system identification; ambient vibrations; historical building.

Address
Khaldoon A. Bani-Hani; Department of Civil Engineering, Qatar University Doha, Qatar
Hazem S. Zibdeh; Department of Mechanical Engineering, Jordan University of Science and Technology, P.O. Box 3030, Irbid, Jordan
Karim Hamdaoui; Department of Structural Mechanics, University of Pavia, Pavia, Italy

Abstract
A methodology for the seismic vulnerability assessment of historical monuments is presented in this paper. The ongoing work has been conducted in Tunisia within the framework of the FP6 European Union project (WIND-CHIME) on the use of appropriate modern seismic protective systems in the conservation of Mediterranean historical buildings in earthquake-prone areas. The case study is the five-century-old Zaouia of Sidi Kassem Djilizi, located downtown Tunis, the capital of Tunisia. Ambient vibration tests were conducted on the case study using a number of force-balance accelerometers placed at selected locations. The Enhanced Frequency Domain Decomposition (EFDD) technique was applied to extract the dynamic characteristics of the monument. A 3-D finite element model was developed and updated to obtain reasonable correlation between experimental and numerical modal properties. The set of parameters selected for the updating consists of the modulus of elasticity in each wall element of the finite element model. Seismic vulnerability assessment of the case study was carried out via three-dimensional time-history dynamic analyses of the structure. Dynamic stresses were computed and damage was evaluated according to a masonry specific plane failure criterion. Statistics on the occurrence, location and type of failure provide a general view for the probable damage level and mode. Results indicate a high vulnerability that confirms the need for intervention and retrofit.

Key Words
ambient vibration testing; output-only modal identification; enhanced frequency domain identification technique; finite element model updating and seismic vulnerability.

Address
Applied Mechanics and Systems Research Laboratory, Tunisia Polytechnic School, B.P. 743, La Marsa 2078, Tunisia

Abstract
This paper represents the final results of a research program sponsored by the European Commission through project WIND-CHIME (Wide Range Non-INtrusive Devices toward Conservation of HIstorical Monuments in the MEditerranean Area), in which the possibility of using advanced seismic protection technologies to preserve historical monuments in the Mediterranean area is investigated. In the current research, the dynamic characteristics of two outstanding Mamluk-Style minarets, which similar minarets were reported to experience extensive damage during Dahshur 1992 earthquake, are investigated. The first minaret is the Qusun minaret (1337 A.D, 736 Hijri Date (H.D)) located in El-Suyuti cemetery on the southern side of the Salah El-Din citadel. The minaret is currently separated from the surrounding building and is directly resting on the ground (no vaults underneath). The total height of the minaret is 40.28 meters with a base rectangular shaft of about 5.42 ?5.20 m. The second minaret is the southern minaret of Al-Sultaniya (1340 A.D, 739 H.D). It is located about 30.0 meters from Qusun minaret, and it is now standing alone but it seems that it used to be attached to a huge unidentified structure. The style of the minaret and its size attribute it to the first half of the fourteenth century. The minaret total height is 36.69 meters and has a 4.48 ?4.48 m rectangular base. Field investigations were conducted to obtain: (a) geometrical description of the minarets, (b) material properties of the minarets?stones, and (c) soil conditions at the minarets?location. Ambient vibration tests were performed to determine the modal parameters of the minarets such as natural frequencies and mode shapes. A 1/16th scale model of Qusun minaret was constructed at Cairo University Concrete Research Laboratory and tested under free vibration with and without SMA wire dampers. The contribution of SMA wire dampers to the structural damping coefficient was evaluated under different vertical loads and vibration amplitudes. Experimental results were used along with the field investigation data to develop a realistic 3-D finite element model that can be used for seismic risk evaluation of the minarets. Examining the updated finite element models under different seismic excitations indicated the vulnerability of such structures to earthquakes with medium to high a/v ratio. The use of SMA wire dampers was found feasible for reducing the seismic risk for this type of structures.

Key Words
shape-memory alloy; seismic mitigation, SMA dampers; historical monuments.

Address
Cairo University, Giza, Egypt

Abstract
For historical masonry structures existing in the Mediterranean area, structural strengthening is of primary importance due to the continuous earthquake threat that is posed on them. Proper retrofitting of historical structures involves a thorough understanding of their structural pathology, before proceeding with any intervention measures. In this paper, a methodology is presented for the evaluation of the actual state of historical masonry structures, which can provide a useful tool for the seismic response assessment before and after the retrofitting. The methodology is mainly focused on the failure and vulnerability analysis of masonry structures using the finite element method. Using this methodology the retrofitting of historical structures with innovative techniques is investigated. The innovative technique presented here involves the exploitation of Shape Memory Alloy prestressed bars. This type of intervention is proposed because it ensures increased reversibility and minimization of interventions, in comparison with conventional retrofitting methods. In this paper, a case study is investigated for the demonstration of the proposed methodologies and techniques, which comprises a masonry Byzantine church and a masonry Cistern. Prestressed SMA alloy bars are placed into the load-bearing system of the structure. The seismic response of the non-retrofitted and the retrofitted finite element models are compared in terms of seismic energy dissipation and displacements diminution.

Key Words
masonry; seismic respons; finite element analysis; failure; vulnerability; seismic retrofitting; SMA.

Address
Institute of Structural Analysis and Aseismic Research, National Technical University of Athens,
9, Iroon Polytechniou St., GR15773, Zografou Campus, Athens, Greece

Abstract
The potential use of Cu-based shape memory alloys (SMA) in retrofitting historical monuments is investigated in this paper. This study is part of the ongoing work conducted in Tunisia within the framework of the FP6 European Union project (WIND-CHIME) on the use of appropriate modern seismic protective systems in the conservation of Mediterranean historical buildings in earthquake-prone areas. The present investigation consists of a finite element simulation, as a preliminary to an experimental study where a cantilever masonry wall, representing a part of a historical monument, is subjected to monotonic and quasi-static cyclic loadings around a horizontal axis at the base level. The wall was retrofitted with an array of copper SMA wires with different cross-sectional areas. A new model is proposed for heat-treated copper SMAs and is validated based on published experimental results. A series of nonlinear finite element analyses are then performed on the wall for the purpose of assessing the SMA device retrofitting capabilities. Simulation results show an improvement of the wall response for the case of monotonic and quasi-static cyclic loadings.

Key Words
copper shape memory alloy; nonlinear finite element analysis; crack modeling; monotonic static loading; cyclic quasi-static loading.

Address
Applied Mechanics and Systems Research Laboratory, Tunisia Polytechnic School, B.P. 743, La Marsa 2078, Tunisia

Abstract
The results of the application of shape memory alloy (SMA) prestressing devices on an aqueduct are presented in this paper. The aqueduct was built in 1747 to provide water to the city of Larnaca and to its port. Because of its importance to the cultural heritage of Cyprus, the aqueduct has been selected as one of the case-study monuments in the project Wide-Range Non-Intrusive devices toward Conservation of Historical Monuments in the Mediterranean Area (WIND-CHIME). The Department of Antiquities of Cyprus, acting in a pioneering way, have given their permission to apply the devices in order to investigate their effectiveness in providing protection to the monument against probable catastrophic effects of earthquake excitation. The dynamic characteristics of the structure were determined in two separate occasions and computational models were developed that matched very closely the dynamic characteristics of the structure. In this paper the experimental setup and the measured changes in the dynamic characteristics of the monument after the application of the SMA devices are described.

Key Words
health monitoring; shape-memory-alloy; monuments; masonry structure; seismic-protection; system-identification; model updating.

Address
Christis Z. Chrysostomou and Andreas Stassis; Higher Technical Institute, POBox 20423, 2152 Nicosia, Cyprus
Themos Demetriou; Heras 13, Nicosia, Cyprus
Karim Hamdaoui; University of Pavia, Via Ferrata, No. 1, 27100 Pavia, Italy


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