Large-scale Engineering Structures Research Articles

Identification of the nonlinear vibration characteristics in hydropower house using transfer entropy

The nonlinear behavior is the primary attribute of the dynamic system stability. In this study, the time-delayed transfer entropy method is proposed to identify the nonlinear dynamic behavior of hydropower house and civil construction, including the transport directionality of information, cracked damage location, and degree of dynamic nonlinearity. Differing from the objects investigated in currently available literature, large-scale civil engineering structures such as hydropower house are more complex and larger size, which stimulate the demand for special identification techniques. Due to the fact that nonlinearity of hydropower house can be induced by many types of interactions between structure and mechanism, a simple similarity model of a multistory building, including damaged contact nonlinearity is studied first following by a discussion of the method for identifying information transmission directionality of the linear or nonlinear structure. The method for identifying the source and degrees of structural nonlinearity vibration is described. Furthermore, the procedure for identification of nonlinearity dynamic behavior in the hydropower house structure based on transfer entropy is studied based on a prototype field experiment under various load cases. Rather than the traditional linear signal processing tools and identification methods, the advantage of this proposed method is to identify the nonlinearity dynamic characteristics of hydropower house structure. This study provides a valuable reference for identifying the damage-induced nonlinearities in civil engineering structures as well as studying the nonlinear dynamic characteristics of hydropower house.

Modern fracture mechanics

Alan Cottrell had a unique ability to impact the metallurgical/materials research community via his fundamental approaches at various length scales and by providing micromechanistic approaches to fracture in crystalline materials, culminating in the macro-mechanics of large-scale engineering structures. His concepts/techniques/analyses have been successfully applied to a range of structural materials and are being applied to an ever-increasing range of more complicated materials systems, ranging from ferrous-based crystalline systems to amorphous metals and biological systems. The field of Modern Fracture Mechanics requires an increasingly complex set of experimental and computational tools to capture material deformation, damage accumulation and failure across multiple size and time scales and builds directly from some of the earliest works and desires of Sir Alan, as reviewed herein.

Random Vibrations of a Cable-Stayed Bridge under Multi-Dimensional Seismic Excitations

It is a challenging problem for scientists and engineers to calculate the random vibration responses of a large scale engineering structure, during which, the calculating efficiency and accuracy are always the main concerns. In civil engineering, there are some even more difficult cases that have to be considered, such as a large span cable-stayed bridge under multi-dimensional seismic loads consisting of evolutionary random processes. In this paper, such a problem is analyzed by using equivalent excitation method, in which the equivalent excitations are constructed by using continuous wavelet transform, and the affections of multi-dimensional seismic excitations are investigated. Simulations of a typical cable-stayed bridge show some of the plausible features of the method presented.

SHAKING TABLE TESTS AND NUMERICAL ANALYSIS FOR VERTICAL SEISMIC RESPONSE OF QUAYSIDE CONTAINER CRANES

Vertical seismic performance is an important issue for the seismic design of large-scale engineering structures. The structure, which is relatively flexible and unrestricted vertically, may resonate and its response is obviously magnified under vertical earthquake excitations. The main objective of this study is to investigate the earthquake-resistance performance of a quayside container crane under vertical seismic excitations. To this end, a geometric-scaled model of 1:50 was firstly constructed according to the similitude law. Then using this model, a hammering modal test and a series of shaking table tests were successively conducted to obtain the dynamic characteristics and vertical seismic responses. Furthermore, the experimental results were compared with the computed results of prototype obtained from numerical analysis and agreed fairly well. From dynamic response results, it is found that the large-scale structure has relatively high vertical earthquake-resistance capacity and could satisfy the seismic design requirement. The findings reported in this paper are expected to provide some valuable information for studying other similar structures in the future.

EDITORIAL The Implementation of Composite Materials in Engineering Structures where Total Safety is of the Essence

on Deformation and Fracture (DFC-11) and Structural Integrity (SI-5), a combined meeting on Composite Materials held for the first time at Queens’ College, Cambridge, England, 13–15th April, 2011. Predicting precisely where a crack will develop in a material under stress and exactly when in time catastrophic fracture of the component will occur is one the oldest unsolved mysteries in the design and building of large-scale engineering structures. Where human life depends upon engineering ingenuity, in aircraft design for instance, the burden of testing to prove a “fracture safe design” is immense. When human life depends upon structural integrity as an essential design requirement, it takes thousands of material test coupons for every composite laminate configuration to evaluate an airframe plus loading to ultimate failure tails, wing boxes, and fuselages to achieve airworthiness certification. Fitness considerations for long-life implementation of critical load-carrying components in aerospace structures, for example, include, on the one hand, understanding deformation and fracture phenomena resulting from impact, fatigue, creep, and stress corrosion cracking. Structural integrity analysis, on the other, treats the design, the materials used, and figures out how best components and parts can be joined, while taking into account reliability, life expectancy, and durability of structure in service. However, there are conflicting aims in the complete “cradle to grave” process of designing simultaneously for high efficiency and safety assurance throughout an economically viable lifetime with an acceptable level of risk. For two decades, the Deformation and Fracture of Composites (DFC) conference series of Sheffield University has provided an international forum for the discussion of critical engineering issues and impact of composite materials on different industry sectors. Likewise, Cambridge University has provided the stage to present ideas on the Structural Integrity (SI) of composite materials and structures at bi-annual meetings held in Cambridge Appl Compos Mater (2012) 19:767–768 DOI 10.1007/s10443-012-9254-y

The Influence of Stochastic Imperfection Field on the Bearing Capacity of Hyperbolic Cooling Towers

The uncontrollable factors such as construction errors, material inhomogeneity, etc. will inevitably lead to a certain initial imperfections. It is generally known that the stochastic initial imperfection of the structure is an important factor for affecting structural stability and bearing capacity. Since these imperfections are random in nature, this paper proposes the method mainly based on the standard orthogonal basis to expand the stochastic field, taking into account the decomposition of the stochastic initial imperfections related to structures, which is projected in the buckling mode orthogonal basis. In the end, the article by the stability analysis example shows that this method can use less random variables effectively describing the original stochastic imperfection field, and efficiently search for the most unfavorable initial imperfection distribution form in order to ensure the imperfection sensitivity structures have a higher reliability, so it can be applied to large-scale engineering structure stochastic imperfection analysis.

Theoretical design and experimental verification of a 1/50 scale model of a quayside container crane

An effective way to study the dynamic performances and seismic behaviours of large-scale engineering structures is using a scale model. This article aims to develop a geometric-scaled model of the 1/50 for a quayside container crane such that the dynamic characteristics of the prototype can be accurately predicted from the relevant features of this scale model. To this end, a detailed design process for the main components of a 1/50 scale model of the quayside container crane was first presented according to the similitude law. Then, a hammering modal test and the Ling dynamic system shaking table test were successively carried out to obtain the dynamic characteristics of this 1/50 scale model. Furthermore, the experimental results were compared with the computed results of the prototype obtained from numerical simulation and they showed a fairly good agreement. From the comparison results, it can be seen that the model design is instructive enough to provide some valuable information and practical use for professionals and researchers involved in the design of large-scale port facilities.

Wavelet-based structural modal parameter identification

SUMMARY A new wavelet-based modal parameter identification method was proposed in this paper. Under the assumption that the ambient excitation loads were white noise, the covariance was calculated from multiple-sensor structural acceleration measurements. Utilizing the wavelet transform, the time-domain covariance responses were transformed into time–frequency domain wavelet coefficients. The constructed matrix at each wavelet scale was subsequently decomposed by singular value decomposition, and structural modal parameters could be estimated from the singular values and singular vectors. The proposed method was proved theoretically, and a numerical example was used to validate this method, which showed that this wavelet-based method was not affected by the measurement noise. Finally the method was applied to ambient vibration records measured on the Donghai Bridge to demonstrate the performance of the proposed technique. Results confirmed its ability in identifying structural modal parameter for large-scale civil engineering structures. Copyright © 2011 John Wiley & Sons, Ltd.

Identification of flutter derivatives from full-scale ambient vibration measurements of the Clifton Suspension Bridge

The estimated response of large-scale engineering structures to severe wind loads is prone to modelling uncertainties that can only ultimately be assessed by full-scale testing. To this end ambient vibration data from full-scale monitoring of the historic Clifton Suspension Bridge has been analysed using a combination of a frequency domain system identification method and a more elaborate stochastic identification technique. There is evidence of incipient coupling action between the first vertical and torsional modes in strong winds, providing unique full-scale data and making this an interesting case study. Flutter derivative estimation, which has rarely previously been attempted on full-scale data, was performed to provide deeper insight into the bridge aerodynamic behaviour, identifying trends towards flutter at higher wind speeds. It is shown that, as for other early suspension bridges with bluff crosssections, single-degree-of-freedom flutter could potentially occur at wind speeds somewhat below requirements for modern designs. The analysis also demonstrates the viability of system identification techniques for extracting valuable results from full-scale data.

Numerical lower bound shakedown analysis of engineering structures

We propose a numerical method for the computation of shakedown loads of engineering structures subjected to varying thermo-mechanical loading. The method is based on Melan’s lower bound shakedown theorem using the von Mises yield criterion. The resulting nonlinear convex optimization problem is presented in a generalized formulation and then solved by an interior-point algorithm, which is characterized by a problem-tailored solution strategy, particularly suitable for application to large-scale engineering structures. Theoretical and numerical issues of the algorithm are described. It’s efficiency is shown by application to thermo-mechanical problems from power plant engineering. The results are compared to those found in literature as well as to calculations with other optimization codes lancelot, ipopt and ipdca.

Historical Development of Iron Screw-Pile Foundations: 1836–1900

Beginning around 1836 screw-pile and screw-cylinder elements were used successfully as helical foundations throughout the world to support a variety of large-scale civil engineering structures. Their development and use is largely attributed to engineers from the UK and the USA. The origins and rise of screw-pile and screw-cylinder foundations are reviewed from an historical perspective focusing on the period from 1836 to 1900. A summary of the use of screw-piles as successful foundations for lighthouses, bridges, and piers as well as their use for other engineering applications is given. A description of the common geometries of screw-piles and screw-cylinders during this period is also presented. The information illustrates that helical foundations have been in use for over 170 years throughout the world and can be considered perhaps the single most important development in geotechnical engineering foundation construction of the mid to late nineteenth century.

Targeting Problems of Composite Failure

Predicting precisely where a crack will develop in a material under stress and exactly when in time catastrophic fracture of the component will occur is one the oldest unsolved mysteries in the design and building of large-scale engineering structures. Fitness considerations for long-life implementation of aerospace composites include understanding phenomena such as fatigue, creep and stress corrosion cracking that affect reliability, life expectancy, and durability of structure. Structural integrity analysis treats the design, the materials used, and figures out how best components and parts can be joined; furthermore, SI takes into account service duty.

An evaluation on the multi-agent system based structural health monitoring for large scale structures

Different kinds of sensors have to be adopted to have a reliable monitoring of large scale engineering structures. Multi-agent system (MAS) based structural health monitoring (SHM) technology is researched to deal with the diverse, heterogeneous and distributed information. This paper introduces an evaluation on a multi-agent system based structural health monitoring to validate the efficiency of the multi-agent technology. Through the cooperation of different agents and different subsystems, the whole system can fuse three kinds of sensor information including strain gauge sensor, fiber optic sensor and piezoelectric sensor, can automatically choose sensing object, can self-organize the sensor network and discard useless sensor data, and can recognize three typical kinds of structure states which may indicate structural damages including impact load, joint failure, strain distribution change on every substructure and the edge area between two adjacent substructures. In the evaluation work besides adopting conventional monitoring instruments, the strain signal of the strain gauge is also demonstrated to be monitored by smart wireless sensor with on-board microprocessor developed in the lab. In this paper the evaluated experimental aluminium plate and the sensor distribution are firstly introduced. The corresponding agents are defined based of the designed multi-agent system frame presented by the authors. The monitoring strategies in the validation work including monitoring principle and monitoring equipments for three typical kinds of structure states are proposed. After the process of developing the impact load diagnostic agent as the basis work of the whole system is introduced in detail, the implementation of the whole multi-agent system based structural health monitoring for the plate is presented. This paper shows the efficiency of the multi-agent technology for the development of the SHM system on the large practical structures.

Nonlinear normal modes, Part I: A useful framework for the structural dynamicist

The concept of nonlinear normal modes (NNMs) is discussed in the present paper and its companion, Part II. Because there is virtually no application of the NNMs to large-scale engineering structures, these papers are an attempt to highlight several aspects that might drive their development in the future. Specifically, we support that (i) numerical methods for the continuation of periodic solutions pave the way for an effective and practical computation of NNMs, and (ii) time–frequency analysis is particularly suitable for the analysis of the resulting dynamics. Another objective of the present paper is to describe, in simple terms, and to illustrate the fundamental properties of NNMs. This is achieved to convince the structural dynamicist not necessarily acquainted with them that they are a useful framework for the analysis of nonlinear vibrating structures.

Optimal placement of sensors for structural system identification and health monitoringusing a hybrid swarm intelligence technique

Setting up a health monitoring system for large-scale civil engineering structures requires alarge number of sensors and the placement of these sensors is of great significance for suchspatially separated large structures. In this paper, we present an optimal sensorplacement (OSP) algorithm by treating OSP as a combinatorial optimizationproblem which is solved using a swarm intelligence technique called particle swarmoptimization (PSO). We propose a new hybrid PSO algorithm by combininga self-configurable PSO with the Nelder–Mead algorithm to solve this ratherdifficult combinatorial problem of OSP. The proposed algorithm aims precisely toachieve the best identification of modal frequencies and mode shapes. Numericalexperiments have been carried out by considering civil engineering structures toevaluate the performance of the proposed swarm-intelligence-based OSP algorithm.Numerical studies indicate that the proposed hybrid PSO algorithm generates sensorconfigurations superior to the conventional iterative information-based approaches whichhave been popularly used for large structures. Further, the proposed hybrid PSOalgorithm exhibits superior convergence characteristics when compared to other PSOcounterparts.

Recent Progress on Distributed Structural Health Monitoring Research at NUAA

This study introduces recent research advances on the structural health monitoring (SHM) at Nanjing University of Aeronautics and Astronautics (NUAA). Distributed SHM technology for large-scale engineering structures is discussed. First, a hybrid wing box health monitoring evaluation system is presented. This evaluation system is developed to verify the piezoelectric sensor array-based active Lamb wave diagnostic method and the fiber Bragg grating sensor-based structural strain monitoring method. Second, distributed health monitoring technology based on the multi-agent system (MAS) technology is discussed. This research includes the individual agent design, the MAS-based SHM system architecture design, and three important aspects in designing the MAS-based SHM system. An evaluation case is presented in detail to show the advantages of the MAS-based SHM system. Finally, the study illustrates the motivation of the agents realized by a wireless sensor network. The developed wireless sensor nodes are also described.

Damage Localization Based on Power Spectral Density Analysis

An environmental excitation having random characteristics may be more effective and cost-efficient than other excitation means for non-destructive damage identification purpose on most of the large-scale engineering structures under operation. In general, many existing damage indexes are constructed based on the modal properties derived firstly from the power spectral density (PSD) analysis of the structures under random excitation. However, the derivation procedures for the modal parameters usually introduce some extra errors into the indexes. This paper aims to propose a simple and feasible damage location index (DLI) constructed directly derived from the analysis results of the structural response PSD. The performance of DLI was verified using an aluminum beam with fixed ends and an experimental reinforced concrete (RC) beam under free boundary condition. Our results show that the damage location of the aluminum beam can be determined via the plot of DLI value by selecting the peaks with the amplitudes exceeding a predefined threshold value in both single- and multi-damaged scenarios. And the index may also predict the possible damage zones in the RC beam experimentally tested.

Designing strategy for multi-agent system based large structural health monitoring

Density and different kinds of sensors have to be adopted to have a reliable monitoring of large scale engineering structures. To deal with the diverse, heterogeneous and distributed information obtained by these sensors at different sites on the structure, multi-agent system (MAS) based structural health monitoring (SHM) technology is researched in detail in this paper. A general framework to design the multi-agent system for large scale structural health monitoring is proposed. Compared to past work, this framework is typical and flexible, which is easy to be referenced by other researchers to develop their own multi-agent based SHM system. The design strategy of the MAS based SHM is discussed in detail, including function design, ontology design, individual agent design, facilitator design, society behavior and learning behavior design. A MAS based composite SHM system is researched as a case study to evaluate the efficiency of the proposed MAS based SHM system design strategy and the advantages of the MAS based SHM system. Very detail introduction of the implementation of this system is given in the paper.

Sensor placement selection of SHM using tolerance domain and second order eigenvalue sensitivity

Monitoring large-scale civil engineering structures such as offshore platforms and high-large buildings requires a large number of sensors of different types. Innovative sensor data information technologies are very extremely important for data transmission, storage and retrieval of large volume sensor data generated from large sensor networks. How to obtain the optimal sensor set and placement is more and more concerned by researchers in vibration-based SHM. In this paper, a method of determining the sensor location which aims to extract the dynamic parameter effectively is presented. The method selects the number and place of sensor being installed on or in structure by through the tolerance domain statistical inference algorithm combined with second order sensitivity technology. The method proposal first finds and determines the sub-set sensors from the theoretic measure point derived from analytical model by the statistical tolerance domain procedure under the principle of modal effective independence. The second step is to judge whether the sorted out measured point set has sensitive to the dynamic change of structure by utilizing second order characteristic value sensitivity analysis. A 76-high-building benchmark mode and an offshore platform structure sensor optimal selection are demonstrated and result shows that the method is available and feasible.

Nonlinear normal modes and their application in structural dynamics

Recent progress in the area of nonlinear modal analysis for structural systems is reported. Systematic methods are developed for generating minimally sized reduced-order models that accurately describe the vibrations of large-scale nonlinear engineering structures. The general approach makes use of nonlinear normal modes that are defined in terms of invariant manifolds in the phase space of the system model. An efficient Galerkin projection method is developed, which allows for the construction of nonlinear modes that are accurate out to large amplitudes of vibration. This approach is successfully extended to the generation of nonlinear modes for systems that are internally resonant and for systems subject to external excitation. The effectiveness of the Galerkin-based construction of the nonlinear normal modes is also demonstrated for a realistic model of a rotating beam.