924 publications from this institution
Abstract In this paper, the feasibility of Structural Health Monitoring (SHM) employing a novel Fibonacy Sequence (FS)-based Optimization Algorithms (OAs) and up-to-date computing techniques is investigated for a large-scale railway bridge. During recent decades, numerous metaheuristic intelligent OAs have been proposed and immediately gained a lot of momentum. However, the major concern is how to employ OAs to deal with real-world problems, especially the SHM of large-scale structures. In addition to the requirement of high accuracy, a high computational cost is putting up a major barrier to the real application of OAs. Therefore, this article aims at addressing these two aforementioned issues. First, we propose employing the optimal ability of the golden ratio formulated by the well-known FS to remedy the shortcomings and improve the accuracy of OAs, specifically, a recently proposed new algorithm, namely Salp Swarm Algorithm (SSA). On the other hand, to deal with the high computational cost problems of OAs, we propose employing an up-to-date computing technique, termed superscalar processor to conduct a series of iterations in parallel. Moreover, in this work, the vectorization technique is also applied to reduce the size of the data. The obtained results show that the proposed approach is highly potential to apply for SHM of real large-scale structures.
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Measurement results of the impact sound insulation of (floating) floors are generally limited to one-third octave bands. As a consequence, detailed information on modal behavior and on the influence of the impact source, are largely lost due to band-integration. To this end, narrow-band measurements are performed on five different layered floors. Various tapping machine locations are considered and the results are averaged over several receiver positions for each tapping machine location in order to reduce the influence of the spatial distribution of the sound pressure in the receiver room. A new prediction model for impact sound transmission, termed the modal TMM, or mTMM, is used to interpret and investigate the measurement results. This prediction method includes a detailed source model and accounts for the finite dimensions of the layered floors. The measurement results of the layered floors clearly indicate the importance of considering all five impact hammer locations of the tapping machine to achieve a high prediction accuracy, especially at low frequencies. The influence of the impact source and the modal behavior of the floor can lead to high peaks in the radiated sound power level.
Plates with attached beams or ribs, rather than monolithic plates, are commonly employed in civil and mechanical engineering for reasons of weight and static stiffness.Unfortunately, attaching stiffeners to a plain plate generally increases its radiation efficiency and reduces its airborne sound insulation.This contribution aims at gaining insight into the sound insulation of rib-stiffened plates in the mid-frequency range, where the modal behavior of the plate is still important, but the neighboring sound fields can already be considered as diffuse.A detailed finite element model of a PMMA plate with steel stiffeners attached is constructed and coupled to a reverberant sound field model of the adjoining room(s) within the recently developed hybrid finite element -statistical energy analysis framework.This framework is computationally very efficient, it enables to compute the coupling loss factors between the sound fields in a rigorous, straight forward way, and the uncertainties due to random wave scattering -which is the physical origin of the diffuse field -can be quantified.The finite element model of the plate is first calibrated by minimizing the difference between its lowest natural frequencies and mode shapes and the corresponding measured values.The hybrid model is then employed for predicting the sound reduction index across the building acoustics frequency range.These predictions are validated against airborne sound insulation measurements.Within a wide frequency range, pronounced dips are observed at specific natural frequencies of the plate, at which the wavelength of the corresponding mode shape is close to the free acoustic wavelength.Since there is an obvious connection with the coincidence phenomenon for infinite plates, the observed phenomenon is termed the semi-discrete coincidence phenomenon.It is shown that in the mid-frequency range, an important increase in airborne sound insulation can be achieved by suppressing only a few particular resonances of the considered rib-stiffened plate.
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A method is developed for computing the mean and variance of the diffuse field sound transmission loss of finite-sized layered wall and floor systems that consist of solid, fluid and/or poroelastic layers. This is achieved by coupling a transfer matrix model of the wall or floor to statistical energy analysis subsystem models of the adjacent room volumes. The modal behavior of the wall is approximately accounted for by projecting the wall displacement onto a set of sinusoidal lateral basis functions. This hybrid modal transfer matrix-statistical energy analysis method is validated on multiple wall systems: a thin steel plate, a polymethyl methacrylate panel, a thick brick wall, a sandwich panel, a double-leaf wall with poro-elastic material in the cavity, and a double glazing. The predictions are compared with experimental data and with results obtained using alternative prediction methods such as the transfer matrix method with spatial windowing, the hybrid wave based-transfer matrix method, and the hybrid finite element-statistical energy analysis method. These comparisons confirm the prediction accuracy of the proposed method and the computational efficiency against the conventional hybrid finite element-statistical energy analysis method.
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A specific strategy is required when performing vibration tests on civil engineering structures. The use of artificial excitation sources such as shakers or drop weights is often unpractical and expensive. Ambient excitation on the contrary is freely available (traffic, wind), but it causes other challenges. The ambient input remains unknown and the system identification algorithms have to deal with output-only measurements. Also typical for vibration testing of large structures is that not all degrees of freedom can be measured at once but that they are divided in several setups with overlapping reference sensors. These reference sensors are needed to obtain global mode shapes. In this paper a novel approach of stochastic subspace identification is presented that incorporates the idea of the reference sensors already in the identification step. The algorithm is validated with an extensive Monte-Carlo simulation study and two real-life examples. Keywords: Civil engineeringoutput-only system identificationconcrete bridge *Corresponding author.bart.peeters@bwk.kuleuven.ac.be *Corresponding author.bart.peeters@bwk.kuleuven.ac.be Notes *Corresponding author.bart.peeters@bwk.kuleuven.ac.be
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No abstract is provided for this article.
