Structural control optimisation and health monitoring using newly developed techniques

University of Technology, Sydney. Faculty of Engineering and Information Technology.Vibration is usually undesirable and yet it occurs in most machines, vehicles, structures, buildings and dynamic systems. The resulting unpleasant motions and the dynamic stresses may lead to fatigue and failure of the structure or machines. In the field of civil engineering, control and identification of the state of health of the structure during the dynamic loads, such as earthquakes and attempt to suppress the vibrations and detect any damage or potential hazard are of vital importance and have posed a great challenge to the research community. This thesis presents new techniques for optimisation, real-time health monitoring and semi-active vibration control of structures subjected to seismic loads. First, a new encoding scheme is presented for a fuzzy-based nonlinear system identification methodology, using subtractive Fuzzy C-Mean clustering and non-dominated sorting genetic algorithm. The method is able to automatically select the best inputs as well as the structure of the fuzzy model in such a way that both accuracy and compactness of model are guaranteed. The proposed method is then employed to identify the forward and inverse models of a MR damper. Numerical and Experimental results show that the developed evolving TSK fuzzy model can identify and grasp the nonlinear dynamics of both forward and inverse systems very well, while a small number of inputs and fuzzy rules are required for this purpose. The optimal design and placement of control devices, is an important problem that affects the control of civil engineering structures. This study also presents a multi-objective optimisation method for simultaneous finding of optimal number and location of actuators and MR dampers, in active and semi-active controlled structures. The method is applied to a nonlinear 20-storey benchmark building. The obtained optimal layout of active actuators is compared to the original benchmark problem definition in which 25 actuators are located in non-optimal places. Results show the effect of proposed strategy where similar level of structural performance, in terms of proposed objective indices, is achieved by use of only 7 actuators in optimal locations. Also, the optimal configuration of different number of MR dampers in the same nonlinear benchmark building is also studied. Results are then compared with optimal locations of actuators in the equivalent active system and the differences are shown. Two new semi-active control algorithms named TSKInv and MaxMin, are also introduced in this research study to convert the force generated by nominal controller to the required voltage of MR dampers. TSKInv algorithm is developed by modelling the inverse dynamics of MR damper using TSK fuzzy inference systems and MaxMin controller is designed based on the maximum (maximum voltage) and minimum (minimum voltage) load of MR damper at each time-step. Applications of these two newly developed methods are compared to some other semi-active control strategies through the 20-storey nonlinear benchmark building. Results show the superiority of these two models over the other algorithms in tracking the desired force using less amount of control force and power. Also, an investigation on different Kalman Filtering algorithms used in system identification is carried out in this dissertation work, on which EKF, IEKF, UKF and IUKF have been applied to some numerical examples to estimate the parameters of targeted structures in real-time using acceleration responses only. Results demonstrate that IUKF and UKF are the most reliable and robust estimators even if the structure is highly nonlinear and measured data are contaminated with noise. Then, a novel recursive least square based method with adaptive multiple forgetting factor is proposed and applied to different structural identification problems with unknown excitations. It is found from the results that, the proposed algorithm can effectively identify the time-varying parameters as well as the unknown inputs to the structure with high computational efficiency. Using the developed techniques, this project aims to prepare a platform for real-time structural integrity assessment of civil infrastructures, during or after earthquakes

Application of Kalman Filtering Methods to Online Real-Time Structural Identification: A Comparison Study

© 2016 World Scientific Publishing Company. System identification refers to the process of building or improving mathematical models of dynamical systems from the observed experimental input-output data. In the area of civil engineering, the estimation of the integrity of a structure under dynamic loadings and during service condition has become a challenge for the engineering community. Therefore, there has been a great deal of attention paid to online and real-time structural identification, especially when input-output measurement data are contaminated by high-level noise. Among real-time identification methods, one of the most successful and widely used algorithms for estimation of system states and parameters is the Kalman filter and its various nonlinear extensions such as extended Kalman filter (EKF), Iterated EKF (IEKF), the recently developed unscented Kalman filter (UKF) and Iterated UKF (IUKF). In this paper, an investigation has been carried out on the aforementioned techniques for their effectiveness and efficiencies through a highly nonlinear single degree of freedom (SDOF) structure as well as a two-storey linear structure. Although IEKF is an improved version of EKF, results show that IUKF generally produces better results in terms of structural parameters and state estimation than UKF and IEKF. Also IUKF is more robust to noise levels compared to the other approaches

Relative growth of the fiddler crab, Uca sindensis(Crustacea: Ocypodidae) in a subtropical mangrove in Pohl Port, Iran

The relative growth of the fiddler crab Uca sindensis in Pohl Port was studied. Ten 0.5 m^2 quadrates were randomly sampled monthly during low tide periods from October 2009 to September 2010. A total of 840 crabs, 449 (53.45%) males and 391 (46.5%) ‌ females, were sampled. The Carapace width of males ranged from 5.5 to 13.5 mm (mean ± SD) (8.92 ± 2.04), and of females from 5.0 to 11.5 mm (mean ± SD) (7.95 ± 1.34). Carapace height (CH) and Carapace length (CL), height of the major cheliped (HMC) of males, abdomen width of females (AW), major cheliped length (LMC), dactiluse (D), feeding cheliped (CHF) and merouse (M) were employed as dependent variables and carapace width (CW) as independent variable. The relationship between CW × CH was positive in males and females. The equation (Log CH=Log-4.881+4.681LogCW) for males (P<0.05) and Log CH=Log-1.882+3.299LogCW for females (P<0.05). The females showed allometric positive growth for CW × AW relation to male (Log AW= Log0.784+1.217Log CW) (P<0.05). Also four male crabs were found with two major cheliped in this study. Remarkable ontogenetic changes were observed in the allometric growth of the male major cheliped and the female abdomen, indicating that these structures are closely connected to the timing of sexual maturity. The allometric growth of U. sindensis in Pohl Port mangrove differed from other Uca populations so far studied, indicating that growth could have been influenced by environment variables such as food availability, population density, distribution of vegetation, sex ratio, soil temperature , organic matter, different of surface and sediment

Nutrient and sediment transport from two different agriculture land uses

For the past decades, the number of research on Non Point Source (NPS) pollution has increased due to its nature being the major source of pollution to water degradation around the world. The study of NPS in Malaysia is scarce especially in agricultural areas. This research aims to provide quality and quantity of runoff pollutant loadings from an agricultural farm at a plot scale. Two plots were constructed at different land use (fruit orchard and vegetable farm). Tipping bucket flow gauges were installed at the end of each slope to measure runoff volume and collect water sample. The water samples were collected over a period of three months, immediately following rainfall events. Nine water parameter (Nitrite, Nitrate, Ammonia, Total Nitrogen, Phosphate, Total Phosphorus, Chemical Oxygen Demand, Total Suspended Solid, pH) analyses were conducted by using the DR5000 UV-Spectrometer. Result indicated that Total Suspended Solid (TSS) from fruit orchard is much higher while the nutrient and Chemical Oxygen Demand (COD) in vegetable farm is higher in comparison. COD is higher in vegetable farm runoff than fruit orchard since organic fertilizers such as chicken manure are applied. Runoff collected is much higher in the fruit orchard since no effective cover crop there. Overall, the results confirmed that runoff waters from agricultural areas are heavily polluted and could affect the nearby receiving water in long term if it is not monitored and controlled

A closed form for the electrostatic interaction between two rod-like charged objects

We have calculated the electrostatic interaction between two rod-like charged objects with arbitrary orientations in three dimensions. we obtained a closed form formula expressing the interaction energy in terms of the separation distance between the centers of the two rod-like objects, $r$, their lengths (denoted by $2l_1$ and $2l_2$), and their relative orientations (indicated by $\theta$ and $\phi$). When the objects have the same length ($2l_1=2l_2=l$), for particular values of separations, i.e for $r\leq0.8 l$, two types of minimum are appeared in the interaction energy with respect to $\theta$. By employing the closed form formula and introducing a scaled temperature $t$, we have also studied the thermodynamic properties of a one dimensional system of rod-like charged objects. For different separation distances, the dependence of the specific heat of the system to the scaled temperature has been studied. It is found that for $r<0.8 l$, the specific heat has a maximum.Comment: 10 pages, 9 figures, 1 table, Accepted by J. Phys.: Condens. Matte