Advances in Science and Technology Vol. 56

Abstract: The post-earthquake rehabilitation and retrofitting of historical structures is an important issue in the entire Mediterranean basin, which is characterized by its richness in historical masonry structures as well as its high seismicity. For the restoration of historical structures and monuments, high demands are raised, due to their great significance as cultural heritage carries. The high importance of these structures, the need for evaluation of their present state and often the determination of the extent and the possible ways of reinforcement, impose the development of a methodology that could offer an estimation of their behaviour, taking into account the uncertainties that are introduced during the analysis. These uncertainties caused by the variety of structural materials used in the same monument, the difficulty of determining their mechanical properties and the random action and intensity of the earthquake phenomenon make essential the presentation of the vulnerability assessment presented in probabilistic terms. This is being accomplished by a methodology which leads to the construction of the fragility curves that can graphically represent the probability of certain damage ranks under the effect of various earthquakes intensities. Through this family of curves, it is possible to investigate the way that each factor affects the vulnerability of the structure, relatively to others. The application of the methodology proposed is illustrated through three typically buildings made of masonry, situated in Crete, Greece and constructed between the 18th and 19th century. Through these case studies the correlation of the earthquake intensity is being shown.

Abstract: This paper presents an on-going research project on development of a wireless sensor node equipped a MEMS accelerometer, which is aiming to design a wireless sensor node to meet specific requirements of the drive-by bridge monitoring for short span bridges. The performance of a trial piece of the sensor node is investigated through vibration tests on a model bridge in laboratory and a real pedestrian bridge. This paper also covers brief statements about the sensor node. The results indicate that acceleration responses taken from the wireless sensor node are comparable with those from the conventional sensing device with wired acceleration transducers.

Abstract: This paper investigates how the cost of structural health monitoring (SHM) technologies competitively fits into the life-cycle management of civil infrastructure. After a brief review of the aging infrastructure problem and a discussion of the technological, organizational, and societal complexities present, the need for synergistic adoptions-in-concert of common metrics, methods, and means of communication is addressed to develop a supporting platform upon which SHM systems can be developed and implemented. Using the costs associated with a recent bridge collapse, methods for the quantification of the utility of SHM are demonstrated. These methods include expanding upon existing and accepted practices, employing risk-based decision making, and calculating the benefit of monitoring in reliability-based life-cycle management models.

Abstract: This paper describes the development of a mechanized wing concept for a perching micro air vehicle. The wings are capable of rotating in pitch at two spanwise joints to simulate the motion of a bird’s wings during a perching maneuver. This project focuses on the wing mechanization design and analysis as well as the structure/mechanism integration. The advantage of a perching type of landing is that it allows the vehicle to land with approximately zero vertical and horizontal velocity on a tree branch, power line, or ledge. The requirements to perform this maneuver were investigated, the structural design was developed, and the mechanization integration to achieve this motion was determined. A model was designed and manufactured to demonstrate the kinematic mechanism making this wing motion possible. Wind tunnel testing and analytical simulation were also completed to further develop the model.

Abstract: In this research the possibilities of the realization of an interactive architecture with the use of dynamic materials is examined. The reason for the use of dynamic materials can be found in the urge to implement material innovation technologies in an architectural context. An inventory of different actuators is made, used for the deformation of the design concept. Shape memory alloys are the most suitable actuators for this application, even though a lot of disadvantages are found. Experiments should point out the possibilities of the application of Shape Memory Alloys.

Abstract: Textile structures are extensively used in construction in forms of geotextiles. The retrofitting of existing masonry walls and soil structures is particularly important for earthquake protection of historic buildings and protection of earthworks against landslides. Unreinforced masonry structures are highly vulnerable because being originally designed mainly for gravity loads they often cannot withstand the dynamic horizontal loads in case of strong earthquakes. Soil structures, such as embankments, are subjected to landslides after heavy rainfalls or during earthquakes. Hence the necessity to develop efficient methods for the retrofitting of existing masonry buildings and earthworks and of related monitoring systems to possibly prevent the structural damage. To solve the above issues new multifunctional textile structures are being developed for application in construction for the retrofitting of masonry structures and earthworks, integrating a combination of different functions, including structural health monitoring.

Abstract: We present a new concept for compact, tunable antennas. Traditional approaches have circuits and switchable elements which can be bulky and lossy. Here we investigate structures which offer direct tuning through voltage-controlled deformation of the radiating structure itself. The antenna is a dielectric resonator (DRA), where the antenna impedance and tuning depends on the shape of the dielectric. The deformation action is through using electro-active polymer (EAP) for the dielectric. EAPs have promising properties for smart antennas and ongoing developments are continuing to improve its suitability.