Papers by Marios Kyriakides
Seismic Performance of Non-Ductile RC Frames with Brick Infill
Improving the Seismic Performance of Existing Buildings and Other Structures, 2009
This paper summarizes some of the findings of a research project that investigates the seismic pe... more This paper summarizes some of the findings of a research project that investigates the seismic performance of masonry‐infilled, non‐ductile, RC frames, including the development of reliable analytical methods for performance assessment and effective retrofit techniques. Quasi‐ ...
Optimisation of Multi-type Sensor Placement for SHM based on application demands
IABSE Symposium, Kolkata 2013: Long Span Bridges and Roofs - Development, Design and Implementation, 2013
The research presents a multi-objective optimisation problem for a multi-type sensor placement fo... more The research presents a multi-objective optimisation problem for a multi-type sensor placement for Structural Health Monitoring (SHM) on a long span bridge. The problem is formulated for simultaneous placement of strain sensors and accelerometers (heterogeneous network) based on the application demands for SHM system. The primary demands for SHM are Modal Identification (MI) and Accurate Mode Shape Expansion (AMSE). The optimisation problem is solved through the use of Integer Genetic Algorithm (GA) to maximise a common metric to ensure adequate MI and AMSE. The performance of the joint optimisation problem solved by GA is compared with other established methods for homogenous sensor placement. The results indicate that the use of a multi-type sensor system improves the quality of SHM and the use of GA improves the overall quality of the sensor placement compared to other methods for optimisation of sensor placement.
Understanding and assessing the seismic performance of masonry infilled reinforced concrete struc... more Understanding and assessing the seismic performance of masonry infilled reinforced concrete structures has been a significant area of research over the last several decades. There is both field and laboratory evidence that demonstrates the detrimental impact an unreinforced masonry infill imparts on a structure due to its interaction with the bounding frame. There is a current lack of reliable and effective retrofit techniques for this group of structures. A new retrofit technique specifically for unreinforced masonry infills in non-ductile reinforced concrete frames is under investigation and presented here. The technique uses a ductile fiber-reinforced mortar material referred to as Engineered Cementitious Composites, or ECC. A series of experiments have been performed in order to examine the impact of a thin layer of ECC applied on masonry alone as well as when it is applied on a masonry wall bounded by a non-ductile reinforced concrete frame. Results indicate that the ECC can he...
Physico-mechanical characterization of non-stabilized Compressed Earth Blocks
<p>... more <p>Recent challenges faced by humanity in relation to the ongoing climatic changes around the globe, have led many practitioners and researchers search for new environmentally friendly materials to use in construction, such as earth-based materials. A specific form of an earth-based building material that nowadays receives particular attention is Compressed Earth Blocks (CEBs). CEBs comprise of soil mixed at low moisture content and are formed under high pressure in compression, without firing. The end-products can be non-stabilized, i.e., without any cement or lime added, or stabilized, whereby a small quantity of stabilizer (<12% by weight) is added, mainly for enhancing their mechanical and durability properties. CEBs, particularly the non-stabilized ones, are considered to be less expensive and environmentally friendlier, compared to the traditional fired clay bricks, due to their lower production cost and excellent recyclability potential, which significantly reduces the end-product’s environmental impact.</p><p>In Cyprus, CEBs were not used in the past, as the prevailing earth building technique on the island was adobe masonry. Recently, however, there appears to be an interest in the use of this material for contemporary construction. The work hereby presented is part of an ongoing research project that focuses on the design, production and characterization of a sustainable and eco-friendly prototype CEB masonry system that will be fabricated using raw materials originating from Cyprus. The project is funded by the European Regional Development Fund and the Republic of Cyprus, through the Cyprus Research and Innovation Foundation (Project ENTERPRISES/0618/0007).</p><p>In the framework of the aforementioned project, various types of locally sourced soils, with different mineralogical/granular composition and plasticity characteristics have been selected and used for the production of non-stabilized CEBs. A series of tests, including particle-size analysis, Atterberg limits determination, shrinkage and compaction measurements, and X-ray diffraction analyses have been carried out to determine the characteristics of the raw materials selected. In addition, compression and 3-point bending tests, capillary absorption measurements and thermal conductivity analyses have been conducted to assess the physico-mechanical properties of the CEBs produced.</p><p>XRD analyses have shown that the soils investigated are mainly composed of carbonates and silicates at different ratios. Preliminary capillary absorption tests have demonstrated that the use of a non-reactive liquid, such as acetone, is better over water in determining the sorptivity of non-stabilized CEBs. In addition, the thermal conductivity of all specimens ranged between 0.60-0.85 W/mK. Finally, the results suggest that, despite the different granular composition of the soils used, all soils demonstrated adequate mechanical properties in terms of compressive (over 5 MPa) and flexural (over 0.5 MPa) strength.  </p>
An improved measure of ground motion intensity that is well correlated with structural and many k... more An improved measure of ground motion intensity that is well correlated with structural and many kinds of nonstructural damage is presented. The proposed intensity measure is based on the peak interstory drift demand computed using a simplified continuous model that consists of a combination of a flexural beam and a shear beam. This new intensity measure accounts for the influence of higher modes and for concentrations of lateral deformation demands along the height of buildings. It is then proposed to compute this new intensity measure at all stations that recorded a seismic event in order to generate improved ShakeMaps for loss estimation and emergency response. The 2004 Parkfield event is used to illustrate both concepts.
An improved measure of ground motion intensity that is well correlated with structural and many k... more An improved measure of ground motion intensity that is well correlated with structural and many kinds of nonstructural damage is presented. The proposed intensity measure is based on the peak interstory drift demand computed using a simplified continuous model that consists of a combination of a flexural beam and a shear beam. This new intensity measure accounts for the influence
Damage assessment of bridges using compound SHM- signal processing and communication challenges
21St European Signal Processing Conference, Sep 1, 2013
Layout optimization of wireless sensor networks for structural health monitoring
SMART STRUCTURES AND SYSTEMS
ABSTRACT
Improving the Seismic Performance of Existing Buildings and Other Structures, 2009
This paper summarizes some of the findings of a research project that investigates the seismic pe... more This paper summarizes some of the findings of a research project that investigates the seismic performance of masonry-infilled, non-ductile, RC frames, including the development of reliable analytical methods for performance assessment and effective retrofit techniques. Quasi-static tests were conducted on small and large-scale, single-story, single-bay, RC frames infilled with brick masonry walls with and without openings. Some of the infill walls were strengthened with an engineered cementitious composite material. Furthermore, two 2/3-scale, three-story, two-bay, masonry-infilled, RC frames were tested on a shake table. One was tested with no retrofit measures, and the other had infill walls strengthened with the engineered cementitious composite and fiber reinforced polymeric material in the first and second stories, respectively. The tests have demonstrated the effectiveness of the retrofit measures. Computation models that combine smeared and discrete cracks have been developed and validated by the experimental data. Some of the experimental and numerical results are presented in this paper.
A Seismic Retrofit for Masonry Infill Walls using Ductile Concrete
IABSE Congress Report, 2008
Behavior of unreinforced masonry prisms and beams retrofitted with engineered cementitious composites
Materials and Structures, 2013
ABSTRACT The impact of a thin layer of a ductile fiber-reinforced concrete referred to as enginee... more ABSTRACT The impact of a thin layer of a ductile fiber-reinforced concrete referred to as engineered cementitious composites (ECC) on unreinforced masonry (URM) prisms and beams has been evaluated. The objective of the research was to characterize the performance and potential benefits of using ECC to retrofit URM with eventual application to masonry infill walls in non-ductile reinforced concrete frames. Compression tests of masonry prisms and flexural tests of masonry beams with different ECC retrofit schemes were conducted. The variables studied were the use of wall anchors to improve the ECC-masonry bond and alternate steel reinforcement ratios within the ECC layer in the form of welded wire fabric. The ECC retrofit was found to increase the strength and stiffness of URM prisms by 45 and 53 %, respectively compared to those of a plain specimen. When wall anchors were installed on the masonry specimens, the bond between the ECC layer and the masonry surface was improved. Four-point bending tests indicated that the strength and more importantly the ductility of an ECC retrofitted brick beam are increased significantly, especially when light reinforcement is added to the ECC layer, relative to an URM beam. Analytical models for estimating the strength and stiffness of ECC retrofitted masonry specimens are proposed and evaluated.
Harvesting energy from vibrations of the underlying structure
Journal of Vibration and Control, 2013
ABSTRACT The use of wireless sensors for structural health monitoring offers several advantages s... more ABSTRACT The use of wireless sensors for structural health monitoring offers several advantages such as small size, easy installation and minimal intervention on existing structures. However the most significant concern about such wireless sensors is the lifetime of the system, which depends heavily on the type of power supply. No matter how energy efficient the operation of a battery operated sensor is, the energy of the battery will be exhausted at some point. In order to achieve a virtually unlimited lifetime, the sensor node should be able to recharge its battery in an easy way. Energy harvesting emerges as a technique that can harvest energy from the surrounding environment. Among all possible energy harvesting solutions, kinetic energy harvesting seems to be the most convenient, especially for sensors placed on structures that experience regular vibrations. Such micro-vibrations can be harmful to the long-term structural health of a building or bridge, but at the same time they can be exploited as a power source to power the wireless sensors that are monitoring this structural health. This paper presents a new energy harvesting method based on a vibration driven electromagnetic harvester. By using an improved Maximum Power Point Tracking technique on the conversion circuit, the proposed method is shown to maximize the conversion coefficient from kinetic energy to applicable electrical energy. © The Author(s) 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.
Journal of Structural Engineering, 2013
This paper presents a study that investigated the effectiveness of retrofitting unreinforced maso... more This paper presents a study that investigated the effectiveness of retrofitting unreinforced masonry infill walls with composite materials to enhance the seismic performance of infilled nonductile RC frames. The primary retrofit scheme considered was the use of engineered cementitious composite overlays. Shake-table tests were conducted on a 2/3-scale, 3-story, 2-bay, masonry infilled RC frame that had one bottom-story wall retrofitted with engineered cementitious composites. The influence of this retrofit on the performance of the structure was investigated using the experimental observations and results of nonlinear finite element analyses. Furthermore, after walls in the second story of the structure were damaged, they were repaired by injecting epoxy into cracked mortar joints, and strengthened with a glass-fiber reinforced polymer overlay. It has been shown that both retrofit schemes are effective in enhancing the seismic performance of the structure and preventing diagonal shear failures of the RC columns.
Evaluation of a Sprayable, Ductile Cement-Based Composite for the Seismic Retrofit of Unreinforced Masonry Infills
Improving the Seismic Performance of Existing Buildings and Other Structures, 2009
Energy Harvesting for Sensors in Infrastructure Monitoring and Maintenance
IABSE Symposium Report, 2013
ABSTRACT Infrastructure monitoring and maintenance needs various kinds of sensors; all these sens... more ABSTRACT Infrastructure monitoring and maintenance needs various kinds of sensors; all these sensors are expected to have long lifetime and self- maintenance and not be replaced. For non-destructive infrastructure monitoring, these sensors should be wireless, however, wireless sensors have an inherent problem on energy efficiency and energy consumption. Thus, how to power sensors efficiently or how to design a self-powered sensor is a key issue to this problem. Energy harvesting technique emerges as a new direction on getting power from environment. Piezoelectric and electromagnetic harvesting methods on vibration are analysed in this paper, and a low cost self-powered conversion circuit is modelled and simulated. Other kinds of energy harvesting are also briefly compared with those two methods; the solar-electric, vibration-electric, thermal-electric and electromagnetic-electric energy harvesting methods are briefly compared in this paper.
Optimisation of Multi-type Sensor Placement for SHM based on application demands
IABSE Symposium Report, 2013
ABSTRACT The research presents a multi-objective optimisation problem for a multi-type sensor pla... more ABSTRACT The research presents a multi-objective optimisation problem for a multi-type sensor placement for Structural Health Monitoring (SHM) on a long span bridge. The problem is formulated for simultaneous placement of strain sensors and accelerometers (heterogeneous network) based on the application demands for SHM system. The primary demands for SHM are Modal Identification (MI) and Accurate Mode Shape Expansion (AMSE). The optimisation problem is solved through the use of Integer Genetic Algorithm (GA) to maximise a common metric to ensure adequate MI and AMSE. The performance of the joint optimisation problem solved by GA is compared with other established methods for homogenous sensor placement. The results indicate that the use of a multi-type sensor system improves the quality of SHM and the use of GA improves the overall quality of the sensor placement compared to other methods for optimisation of sensor placement.
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Papers by Marios Kyriakides