Marios Kyriakides

Shake-Table Tests of a 3-Story Masonry-Infilled RC Frame Retrofitted with Composite Materials

AbstractThis 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 ...

Seismic performance of non-ductile RC frames with brick infill

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.

Simulation of Unreinforced Masonry Beams Retrofitted with Engineered Cementitious Composites in Flexure

AbstractA two-dimensional non-linear finite-element analysis micro-modeling approach to simulate unreinforced masonry beams in bending is extended to include a retrofit with a thin layer of ductile fiber-reinforced cement-based material referred to as engineered cementitious composite (ECC). The retrofit method is one that has been demonstrated to add significant ductility to unreinforced masonry infill walls under in-plane cyclic loading and is further expected to enhance out-of-plane bending resistance. The objective of the research is to identify and propose a modeling approach for this complex system of four materials and three different types of interface using basic material properties and established model parameters for future analyses of the retrofit system in structural applications. Of the two geometric models investigated, a simplified approach using expanded brick units with zero-thickness mortar elements is recommended and validated. Brick-mortar interface opening, cracking of the ECC layer ...

Harvesting energy from vibrations of the underlying structure

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.

Cyclic Response of Nonductile Reinforced Concrete Frames with Unreinforced Masonry Infills Retrofitted with Engineered Cementitious Composites

AbstractA new seismic retrofit technique for unreinforced masonry infills in nonductile reinforced concrete frames is presented. The objective was to develop a light and easy to apply retrofit technique for the infills that both delays shear failure at the columns of the nonductile bounding frame when subjected to an earthquake by preventing severe deterioration of the infill wall, and enhances the ductility of the system. The retrofit technique uses sprayable engineered cementitious composites (ECCs), a micromechanically designed cement-based material reinforced with short, randomly distributed polymeric fibers. Four small-scale unreinforced masonry infilled nonductile reinforced concrete frames were tested under in-plane quasi-static cyclic lateral loading. One unretrofitted wall and three different retrofit schemes were evaluated. Continuous steel reinforcement was embedded in the ECC layer and a bonding agent was applied between the masonry wall and the ECC layer. In two retrofits the impact of two di...

Numerical evaluation of multi-metric data fusion based structural health monitoring of long span bridge structures

Abstract This work focuses on structural health monitoring of long span bridges for damage detection. A feature extraction level data fusion based damage isolation strategy is presented using multi-metric sensing. The multi-metric sensing uses two types of sensors, namely strain sensors and accelerometers. The methodology combines the advantages offered by each type of sensors, while at the same time overcomes their limitations. The flexibility index method is applied and the flexibility matrices based on the strain and displacement data are combined after performing co-ordinate transformation. A study has been carried out on a simulated finite element model of the Great Belt East Bridge where realistic damage scenarios like damage in the girder, breaking of hanger cables, pier settlement, and loss of cable pretension were introduced on the structure. The study indicates that multi-metric sensing is indeed necessary as it reduces the possibility of false detections and increases the sensitivity and robustness of the methodology.