Experimental Research on Bond Behaviour of Fabric Reinforced Cementitious Matrix Composites for Retrofitting Masonry Walls

Fayu Wang,Nicholas Kyriakides,Christis Chrysostomou,Eleftherios Eleftheriou,Renos Votsis,Rogiros Illampas 한국콘크리트학회 2021 International Journal of Concrete Structures and M Vol.15 No.3

Fabric reinforced cementitious matrix (FRCM) composites, also known as textile reinforced mortars (TRM), an inorganic matrix constituting fibre fabrics and cement-based mortar, are becoming a widely used composite material in Europe for upgrading the seismic resistance of existing reinforced concrete (RC) frame buildings. One way of providing seismic resistance upgrading is through the application of the proposed FRCM system on existing masonry infill walls to increase their stiffness and integrity. To examine the effectiveness of this application, the bond characteristics achieved between (a) the matrix and the masonry substrate and (b) the fabric and the matrix need to be determined. A series of experiments including 23 material performance tests, 15 direct tensile tests of dry fabric and composites, and 30 shear bond tests between the matrix and brick masonry, were carried out to investigate the fabric-to-matrix and matrix-to-substrate bond behaviour. In addition, different arrangements of extruded polystyrene (XPS) plates were applied to the FRCM to test the shear bond capacity of this insulation system when used on a large-scale wall.

3-D and Anisotropic Effects on the Prediction of Burst in Aluminum Tube Hydroforming

Y.P. Korkolis,S. Kyriakides 한국소성가공학회 2010 기타자료 Vol.2010 No.6

Thin-walled Al-6260-T4 aluminum tubes were hydroformed in a custom testing facility [1,8]. The major mode of failure observed in the experiments was bursting, despite the simultaneous application of axial compression while inflating the tubes. At the same time, a series of FE models were developed in the nonlinear code ABAQUS to simulate the experiments; however, initial computations failed to yield accurate predictions of burst. This was attributed to the adoption of the classical J2 plasticity, which is unsuitable for an anisotropic aluminum alloy, and led to an extensive study of the constitutive behavior of Al-6260-T4 and of its forming limits (see [2-4]). With the benefit of this improved understanding of the material behavior, the hydroforming simulations were revisited and models of different degrees of sophistication were developed. Starting with shell element models, the anisotropic yield functions calibrated earlier in [2-4] were shown to improve predictions over the J2 plasticity, but were found to still be deficient in predicting the failures observed in the experiments. This was in turn attributed to the fact that shell elements cannot capture the stress triaxiality associated with the gradual evolution of necking encountered in hydroforming. In addition, despite the relatively thinwalled geometries involved, significant through-thickness stresses develop in the regions of the tube in contact with the die. These stresses are again missed by a shell element discretization. Both of these observations point to the use of solid element models, to capture the stress triaxiality. We will show that when these models are run in conjunction with nonquadratic anisotropic constitutive models, accurate predictions of failure in tube hydroforming are obtained. The conclusion that solid elements are required for failure calculations in tube hydroforming and that shell element models are deficient in that respect, contrasts sharply the current industrial practice in hydroforming simulations.

Benchmarking of Phase Locked Loop based Synchronization Techniques for Grid-Connected Inverter Systems

Yongheng Yang,Lenos Hadjidemetriou,Frede Blaabjerg,Elias Kyriakides 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

Grid-connected renewables are increasingly developed in recent years, e.g. wind turbine systems and photovoltaic systems. Synchronization of the injected current with the grid is mandatory. However, grid disturbances like voltage sags, harmonics, and frequency deviations may occur during operation, becoming inevitable challenges to the synchronization of the grid-connected renewable energy systems. In order to ensure the quality of the power generation from the renewables, robust and reliable synchronization methods are in demand. Among the prior-art solutions, Phase Locked Loop (PLL) based synchronization methods have gained much popularity in grid-connected applications. However, an appropriate selection and thus a proper design of the selected PLL synchronization remain of interest in practice, especially for single-phase systems. Therefore, in this paper, a benchmarking of the main PLL synchronization methods for single-phase grid-connected inverter systems in terms of accuracy, dynamic response, harmonic immunity, etc., has been conducted. Experiments on a 1-kW single-phase gridconnected system, suffering from different grid disturbances, are performed for the benchmarking. The experimental results have verified the discussions.

Multi-type, multi-sensor placement optimization for structural health monitoring of long span bridges

Rohan N. Soman,Toula Onoufriou,Marios A. Kyriakides,Renos A. Votsis,Christis Z. Chrysostomou 국제구조공학회 2014 Smart Structures and Systems, An International Jou Vol.14 No.1

The paper presents a multi-objective optimization strategy for a multi-type sensor placement for Structural Health Monitoring (SHM) of long span bridges. The problem is formulated for simultaneous placement of strain sensors and accelerometers (heterogeneous network) based on application demands for SHM system. Modal Identification (MI) and Accurate Mode Shape Expansion (AMSE) were chosen as the application demands for SHM. The optimization problem is solved through the use of integer Genetic Algorithm (GA) to maximize a common metric to ensure adequate MI and AMSE. The performance of the joint optimization 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 can improve the quality of SHM. It has also been demonstrated that use of GA improves the overall quality of the sensor placement compared to other methods for optimization of sensor placement.

Layout optimization of wireless sensor networks for structural health monitoring

Jalsan, Khash-Erdene,Soman, Rohan N.,Flouri, Kallirroi,Kyriakides, Marios A.,Feltrin, Glauco,Onoufriou, Toula Techno-Press 2014 Smart Structures and Systems, An International Jou Vol.14 No.1

Node layout optimization of structural wireless systems is investigated as a means to prolong the network lifetime without, if possible, compromising information quality of the measurement data. The trade-off between these antagonistic objectives is studied within a multi-objective layout optimization framework. A Genetic Algorithm is adopted to obtain a set of Pareto-optimal solutions from which the end user can select the final layout. The information quality of the measurement data collected from a heterogeneous WSN is quantified from the placement quality indicators of strain and acceleration sensors. The network lifetime or equivalently the network energy consumption is estimated through WSN simulation that provides realistic results by capturing the dynamics of the wireless communication protocols. A layout optimization study of a monitoring system on the Great Belt Bridge is conducted to evaluate the proposed approach. The placement quality of strain gauges and accelerometers is obtained as a ratio of the Modal Clarity Index and Mode Shape Expansion values that are computed from a Finite Element model of the monitored bridge. To estimate the energy consumption of the WSN platform in a realistic scenario, we use a discrete-event simulator with stochastic communication models. Finally, we compare the optimization results with those obtained in a previous work where the network energy consumption is obtained via deterministic communication models.

Layout optimization of wireless sensor networks for structural health monitoring

Khash-Erdene Jalsan,Rohan N. Soman,Kallirroi Flouri,Marios A. Kyriakides,Glauco Feltrin,Toula Onoufriou 국제구조공학회 2014 Smart Structures and Systems, An International Jou Vol.14 No.1

Node layout optimization of structural wireless systems is investigated as a means to prolong the network lifetime without, if possible, compromising information quality of the measurement data. The trade-off between these antagonistic objectives is studied within a multi-objective layout optimization framework. A Genetic Algorithm is adopted to obtain a set of Pareto-optimal solutions from which the end user can select the final layout. The information quality of the measurement data collected from a heterogeneous WSN is quantified from the placement quality indicators of strain and acceleration sensors. The network lifetime or equivalently the network energy consumption is estimated through WSN simulation that provides realistic results by capturing the dynamics of the wireless communication protocols. A layout optimization study of a monitoring system on the Great Belt Bridge is conducted to evaluate the proposed approach. The placement quality of strain gauges and accelerometers is obtained as a ratio of the Modal Clarity Index and Mode Shape Expansion values that are computed from a Finite Element model of the monitored bridge. To estimate the energy consumption of the WSN platform in a realistic scenario, we use a discrete-event simulator with stochastic communication models. Finally, we compare the optimization results with those obtained in a previous work where the network energy consumption is obtained via deterministic communication models.