DAMAGE QUANTIFICATION OF BEAMS USING FREQUENCY SIGNATURE

ABSTRACT: A rapid method for determining the damage severity sustained by a beam proved to be challenging due to either limited studies conducted on the subject or alternative methods require highly sophisticated and costly equipment to perform. In this research, the unique frequency signature emitted by a beam when excited by an external force was utilized in order to determine the changes in the properties of the beam. Experiments were performed using a roving accelerometer hammer impact test on a beam with a grounded configuration to test the changes occurring as the controlled damage sustained by the beam increases. The acceleration response of the beam obtained from the experiment is then processed using software incorporating Kalman Filter and structural dynamics. Results show that the dominant frequency obtained in both the Fast Fourier Transform and Power Spectral Density of the acceleration response of the beam decreases as the damage incurred by the beam increases. The results also show that regardless of the position of the accelerometer, dominant frequencies tend to converge to a value depending on the damage sustained in the beam. Damping ratio of the beam also decreased as the damage sustained by the beam increased. Inversely, the increase in damage of the beam corresponds to an increase in the dissipation rate of the beam. The study was able to achieve its goal of quantifying damage in a beam through the use of frequency signature by identifying the changes in its dominant frequencies and the damping ratio and dissipation rate

Design and Simulation of a Model Predictive Controller (MPC) for a Seismic Uniaxial Shake Table

Shake table is one of the apparatus that aids in researches to generate techniques, structural developments, and strategies to prevent, prepare, and minimize an earthquake’s devastating effects. One important factor that should be considered in a shake table is the system dynamics due to control-structural interactions, which could either be linear or non-linear. To accurately model both has always been the challenge but becomes more plausible with the availability of faster hardware and computers and the continuous decrease in latency. Model Predictive Controller (MPC) is a type of controller extensively used in the industry that can be used on linear and non-linear systems. This study presents the design and simulation of an MPC for a uniaxial shake table intending to analyze the system’s behavior and accuracy. MATLAB Simulink was utilized to handle the simulation analysis of the controller. Different MPC parameters such as sample time, prediction horizon, control horizon, and closed-loop performance were manipulated and adjusted to observe their effects on the output of the system. A signal that mimics the actual earthquake data was inputted into the controller, and the system's behavior and outputs were measured and presented through graphical representations. To determine the accuracy of the system’s output, its relationship with the reference signal was compared. From the simulation produced, the system demonstrated high accuracy levels and could be adjusted depending on the set performance aggressiveness of the system

An integrated micro-computer based qualitative and quantitative superstructure rating system for highway RCDG bridges

An integrated micro-computer based qualitative and quantitative superstructure rating system for highway bridges is developed. The purpose of this developed Windows-based software is to evaluate the qualitative condition of the components including the overall condition and to determine the strength of the bridge superstructure. A new approach is introduced in the qualitative condition rating. These improvements are the following: a criteria for quantifying and determining the condition of the various superstructure component, an importance factor for each component under various deterioration degree and a weighed average technique combining the rating of each component with its structural importance to determine the overall rating of the bridge. In the quantitative rating method, the Load and Resistance Factor Method is used instead of the operating and inventory rating.The software consists of three major modules: Bridge Inventory and Data module, qualitative and quantitative module and the on-line help module. These modules interact to perform an integrated superstructure bridge rating system

New design wind speed for a wind turbine generator (WTG) considering typhoon loads

Strong typhoons in Asian countries occur frequently. Therefore if WTGs are constructed in these areas these extreme loads should be taken into account. In view of this, we analyzed the probability of buckling failure (pf) of a WTG considering extreme wind speeds distributions from both typhoon and non-typhoon prone areas and the buckling resistance of a tower in terms of wind speeds. Since the pf decreases when typhoons are considered we introduced a new buckling resistance against this load. This assertion maintains the original pf between the original buckling resistance and the non-typhoon load distribution. Based on this new wind speed resistance a new 50-year design wind speed (V e50new) and a new reference wind speed (V refnew) is obtained. Some numerical simulation were done to illustrate the proposed concept using typhoon data from 50 weather stations in the Philippines. For a specific diameter and thickness of the tower V e50new was calculated. Using kriging method of of ArcGIS geostatistical analyst the results were interpolated to other unmeasured areas to create a prediction surface for V e50new. The results are useful for wind farm owners

The Manito geothermal livelihood project: Stimulating economic development in rural areas

A drying plant and a 1.5 MW power plant was constructed in Manito, Albay, Philippines. The project was made possible through a government inter-agency joint undertaking. This project is the energy sector\u27s contribution to the government\u27s thrust to improve and accelerate the delivery of basic services, particularly to marginalized communities

Optimal maintenance strategy for buried pipelines

Decision strategy of inspection, repair and safety levels of buried pipelines under corrosive environment and third party incident risk is described. Pipe damages, which are caused by potential defect, corrosion, and third party accident, are classified into three typical damage models which include minor leakage, moderate leakage to cause eruption and major damage to develop a crack propagation. Risk assessment are made for a transmission pipeline system which is surrounded with various hazards spatially distributed along the pipeline route. The effect of risk reduction by the maintenance activities including periodic inspections and repair works are also taken into consideration, while the insurance premium approach is discussed to transfer the risk from the owner to the insurance company. Numerical calculations provide useful information on the effectiveness of the proposed four maintenance strategies

Performance-based design of a wind turbine under typhoon and earthquake loads

Two extreme load levels, Levels 1 and 2, for typhoons and earthquakes were considered in the performance-based design of a wind turbine. The failure modes considered are tower buckling failure, anchor bolt pull-out and soil bearing capacity failure. For each load case the probabilities of failure for three damage states (minor, moderate and major) were analyzed. The cost of strengthening and the failure costs were also obtained. Finally an optimal investment cost is proposed which is important for wind farm owners for capital budgeting purposes. This value also corresponds to a target probability of failure of a wind turbine which can be used in the design of wind turbines in typhoon and earthquake-prone areas

Managing the risks of a wind farm in typhoon-prone areas

The paper first ascertains the increase in buckling failure risk of a wind turbine due to typhoons. This condition necessitates a study of an efficient way of managing the risks in order to avoid financial ruin. Consequently the authors proposed methods for managing typhoons risk for existing and proposed wind farms. For the former, we explore the option of transferring the added risk to insurance. In this case, an optimum insurance premium is determined. For the latter, the risk is mitigated, by increasing the thickness of the tower. The optimum thickness is determined considering the projects\u27 net present value and the internal rate of return

Estimating the limit state exceeding probability of a deteriorating structure using the Kalman filter, extended Kalman filter, unscented Kalman filter and the sequential Monte Carlo simulation

This paper focuses on determining the limit state exceeding probability of a deteriorating model using optimal and sub-optimal Bayesian algorithms. Specifically the Kalman filter (for a linear system), extended Kalman filter, unscented Kalman filter and the sequential Monte Carlo simulation (for non-linear systems) are used to approximate the present state of a deteriorating system given measurements tainted with noise of the system output. In addition to the comprehensive discussion of the theory, numerical implementation and comparison of the results through numerical examples are shown