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Service performance evaluation is of great significance to the safety, durability, and reliability of bridge engineering. Over the last decade, structural health monitoring (SHM) systems have been widely used for condition monitoring of cable-stayed bridges, massive monitoring data are measured and stored by the sensing subsystems, which provides the basis for service performance evaluation of bridge engineering. Meanwhile, the load test is a common method to assess the construction and service performance of bridges. Combined the SHM systems and a load test of a thousand-meter level cable-stayed bridge after ten years of service, this paper investigates the operating conditions of main structures, including bridge towers, main girders, and steel cables. 52 trucks were used to conduct a quasi-static load on three key sections of bridges. Meanwhile, the GPS displacement of towers and main girders, stress of the main girders and acceleration responses of cables were measured synchronously by the SHM systems. Based on the health monitoring data, the dynamic responses, structural deformation, and cable tension of the bridge were investigated and evaluated by comparing with the finite element (FE) model load test at construction stage. The results show that the service performance of the bridge is basically within the designed conditions.

A nonlinear thermoelastic model of a circular plate is presented in the paper. The model, based on the Mindlin plate theory, is extended by taking into account nonlinear geometrical terms. Partial differential equations of plate’s dynamics are derived for a fully coupled thermal and mechanical fields. Then the model is reduced to a set of ordinary differential equations taking into account the first three natural modes and assuming a constant thermal field. The influence of elevated temperature on the resonance curves and the mode involvement due to nonlinear and thermal couplings is presented. The analysis shows that the increased temperature may lead to various bifurcation scenarios. The buckling phenomenon and post-buckling nonlinear regular and chaotic oscillations are studied.

Fatigue damage is a type of damage usually occurring to repeatedly loaded elements of structures in various engineering fields. Accumulation of fatigue damage may cause failure of structural elements. Identification of incipient fatigue damage is essential to ensure safety of structures. Fatigue crack under repeated loads commonly behaves in a nonlinear dynamic manner, typically manifested by both occurrence of higher harmonic components and interaction of harmonic components. Interrogation of nonlinear dynamic manner provides a promising way to characterize structural fatigue damage. This study aims at developing a new method to interrogate nonlinear dynamic manner for fatigue damage identification. This method is based on bispectral analysis of structural vibrational responses. This method portrays fatigue damage by inspecting the presence of higher harmonic components and quantifying the interaction of these harmonic components. The method can precisely locate and quantify a small-sized fatigue damage in a cantilever beam, presenting great accuracy in fatigue damage identification.

Hidden damage severely threatens the safety of structures due to its invisibility and indistinguishability. Debonding is typical hidden damage in steel-reinforced bridges. Detection of multiple debondings in steel-reinforced bridges poses a challenge for traditional nondestructive methods that require damage location as prior knowledge, but this condition is usually not satisfied for debonding located within the bridge. Differing from existing studies, this study explores a vibrational method of detecting multiple debondings needing no prior knowledge, that uses a scanning laser vibrometer to acquire densely-sampled operating deflection shapes of bridges. The operating deflection shape carries richer information than mode shapes for damage characterization. Nevertheless, densely-sampled deformed quantities are commonly susceptible to noise when used to identify damage. To detect multiple debondings, a new feature is developed, the wavelet-transform curvature operating deflection shape. This feature is used to identify multiple debondings in a steel-reinforced concrete slab dismantled from a bridge, clearly demonstrating the strengths of suppressing noise, intensifying the signatures of debonding, and requiring no prior knowledge of damage location. The proposed method holds promise for detecting multiple hidden damage in various structures besides bridges.

Dynamics of a Timoshenko beam under an influence of mechanical and thermal loadings is analysed in this paper. Nonlinear geometrical terms and a nonuniform heat distribution are taken into account in the considered model. The mathematical model is represented by a set of partial differential equations (PDEs) which takes into account thermal and mechanical loadings. The problem is simplified to two PDEs and then reduced to ordinary differential equations (ODEs) by means of the Galerkin method taking into account three modes of a linear Timoshenko beam. Correctness of the analytical model is verified by a finite element method. Then, the nonlinear model is studied numerically by a continuation method or by a direct numerical integration of ODEs. An effect of the temperature distribution on the resonance near the first natural frequency and on stability of the solutions is presented. The increase of mechanical loading results in hardening of the resonance curve. Thermal loading may stabilise the beam dynamics when the temperature is decreased. The elevated temperature may transit dynamics from regular to chaotic oscillations.

This special issue is a result of discussions performed during a workshop (with the same name) held in Lublin, February 2014. This meeting served as the seed to invite several experts in the field to present contributions for this Special Topics issue which reflect the present state of the art for research and development of smart materials and their possible applications for energy control and energy harvesting.

This engineering research focus issue was inspired by the workshop organised by us on March 19th 2012 at the Lublin University of Technology (in the framework of CEMCAST) titled “Dynamics of functionally graded materials and systems with hysteresis” The collection of the present research papers followed our fruitful discussions focussing on “Dynamics of composite nonlinear systems and materials for engineering applications and energy harvesting” which is now the title of the present volume. In the next two sections we briefly discuss the topics included in this focus issue.

In this work numerical and experimental study of the dynamic behaviour of a composite laminated beam having delamination is presented. The model of delamination takes into account a contact interaction between sublaminates including normal forces, shear forces and additional damping. In order to verify the model special samples of multilayered beams have been manufactured. Small parts of adjacent layers have been cut and replaced by inclusions from different materials modelling delamination. The mechanical properties of the inclusions have been considered during the numerical calculations. The beams were subjected to a short pulse loading and then their response was registered. The results from the numerical simulation were in a good agreement with the experimental results. The significance of the additional damping due to delamination on the response of the beam was confirmed numerically and experimentally.

In this work dynamic behaviour of a composite beam having delamination is presented. The model of delamination takes into account a contact interaction between sublaminates including normal forces, shear forces and additional damping. Numerical calculations are performed in order to estimate the influence of the new terms included into the model.

In this work numerical and experimental study of the vibration of laminated beams with damage, subjected to dynamic loading and temperature variations is presented. The goal of the study is to check the applicability of the damage detection technique based on an analysis of the Poincare maps of the beam response. The geometrically nonlinear version of the Timoshenko beam theory is used to model the beam behavior. The damage is represented as a reduction of the effective elastic modulus of the beam material in a small area of the structure. The beams are subjected to a harmonic loading, leading to large amplitude vibrations and to temperature changes. The main results are focused on establishing the influence of the damage on the vibration response of heated or unheated structures and the change in the time-history diagrams and the Poincare maps, caused by a damage and elevated temperature. The damage detection criterion formulated earlier for nonheated plates, based on analysing of the Poincare maps of the damaged and healthy plate, is modified and tested for the case of beams additionally subjected to elevated temperatures. The importance of taking into account the actual temperature in the process of damage detection is shown. Performed experimental tests (by an optical method) confirm the applicability and sensitivity of the proposed method.

The main aspect of the paper is to give an answer to the question of what specific kind of defect has actually occurred in a structure and how to distinguish between different kinds of discontinuities. For this purpose composite rods and beams with fatigue cracks, step changes in cross-sectional area and small changes in material properties have been investigated. The objective of the work has been to propose a signal processing methodology based on wavelet transformation for identification of specific discontinuity. The identification of a fatigue crack from other discontinuities has been demonstrated. It has been also found that the proposed methodology might be useful for precise indication of the size of the identified fatigue damage.

This study investigates a possibility for representing, interpreting and visualising the vibration response of aircraft panels using time domain measurements. The aircraft panels are modelled as thin orthotropic plates and their vibration response is simulated using FE modelling. The vibration response of a thin aluminium panel is simulated using FE modelling. The first ten resonant frequencies are estimated for the FE model and for the dynamically tested panel. They were found to show somewhat low sensitivity to damage. Then the simulated vibration response of the panel is transformed and expanded in a new phase space. This presents an alternative way to study and analyse the dynamics of a structure. A two dimensional phase space is used in this investigation. Thus instead of studying the single dimension measured vibration characteristics one is faced with expanded two dimensional variables which can be visualised and this facilitates the comparison between the damaged and the non-damage states.

The main goal of this work is to develop accurate and time efficient numerical approaches to study geometrically nonlinear vibrations of moderately thick beams under the combined action of mechanical and thermal loads. The influence of the thermal loading duration and thermal loading amplitude on the response of the structures is studied. Beams subjected to short heat flux and mechanical harmonic loading, with the excitation frequencies close to the natural frequencies of the beams, are investigated.

This paper discusses and illustrates the influence of transverse shear on the response of a thick elastic-plastic beam when it is subjected to a pulse load. The pseudo-normal mode superposition method is used for solving the equations of motion. Numerical results are obtained for simply supported and clamped beams subjected to a pulse load of finite duration.

The dynamic contact interaction between an elastic-plastic beam with a variable cross-section and a two-parametric elastic foundation with a finite thickness is studied. The beam is subjected to an impulsive loading and its plastic properties are described by a linear isotropic strain-hardening model. The finite difference approximation is applied to the spatial domain and the fourth-order Runge-Kutta method is used to solve the nonlinear problem in the time domain. The development of the contact spot in time and the influence of the contact forces and foundation properties on the elastic and elastic-plastic beam response are presented.

The problem of thermally induced vibrations of a simply supported elastic-plastic Timoshenko beam with a linear work hardening is studied. The applied load is a short time thermal flow acting on the upper beam surface. The problem is solved using two models: the joint thermo-elasto-plastic equations and decoupled ones. Numerical results are obtained for three types of heat flow pulse loads (rectangular and two triangular pulses) with different durations and amplitudes. The coupling effects on the transverse beam displacements and on the temperature bending moment are studied. The influence of the pulse shape and pulse duration on the beam response is considered also.

An electro-mechanical system of vibrational energy harvesting is studied. The beam is excited by external and kinematic periodic forces and damped by an electrical resistor through the coupled piezoelectric transducer. Nonlinearities are introduced by stoppers limiting the transverse displacements of the beam. The interaction between the beam and the stoppers is modeled as Winkler elastic foundation. The mechanical properties of the piezoelectric layer are taken into account and the beam is modeled as a composite structure. For the examined composite beam, the geometrically nonlinear version of the Timoshenko’s beam theory is assumed. The equations of motion are derived by the principle of virtual work considering large deflections. An isogeometric approach is applied for space discretization and B-Splines are used as shape functions. Finally, the power output and the efficiency of the system due to harmonic excitations are discussed. The influence of the position of the stoppers and their length on the dynamics of the beam and consequently on the power output are analyzed and presented.