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This paper investigates the problem of consensus for one kind of sampled-data heterogeneous multi-agent system. We first discretize the continuous-time networked system by the method of sampled-data. Then we use a system transformation to transform the multi-agent system into the reduced-order error system. Two consensus algorithms with and without velocity measurement will be considered respectively. We obtain two sufficient conditions for the networked systems with and without velocity measurement to reach consensus through analyzing the stable problem of the reduced-order systems. Simulations are given to verify the effectiveness of the results.

This article investigates the observer-based finite-time $H_\infty$ control problem for interconnected fuzzy systems with quantization and random network attacks, where two types of network attacks including denial-of-service (DoS) and fault data injection (FDI) attacks are considered. In order to achieve the occupancy reduction of network resources, the measured outputs of interconnected systems are quantized through a logarithmic quantizer before being transmitted by the communication channel. Combining the effects of quantization and random network attacks, an observer-based control model is first constructed. Then, based on Lyapunov functional approach and stochastic analysis technique, some sufficient conditions are presented such that the considered closed-loop interconnected system is stochastically finite-time bounded with a prescribed disturbance attenuation level, and the gain matrices of fuzzy observer and fuzzy controller can be found by solving an optimization algorithm with linear matrix inequalities constraints. Finally, two simulation examples are given to illustrate the validity of the proposed approach.

This paper provides a practical design method for hybrid unbonded post-tensioned precast concrete joints. Such joints featured with self-centering capacities have been widely favored in recent years. However, the absence of design methods hinders their further promotion. To solve the issue, two methods for calculating mechanical behavior of the joints were first studied: characteristic points method and iterative method. The effectiveness of the methods was verified by the existing test results. On this basis, a joint design method considering both yield bearing capacity and energy dissipation capacity was proposed. Moreover, to facilitate design, some factors affecting the bearing capacity were discussed. A five-story frame structure was designed by the proposed design method, and the influence of two design factors on structural response was analyzed by utilizing nonlinear time-history method. The analysis results show that: with the increase of energy dissipation factor αs, the post-earthquake residual deformation of the structure tends to increase linearly, while the accumulated damage of the structure will decrease continuously; both overdesign and underdesign of bearing capacity of the joint are unfavorable; and near-field earthquake may cause irreparable damage to structural columns, making the residual deformation of structures contrary to the self-centering capacity of joints, which shall be considered during engineering design.

In this technical note, the problem of observer-based controller design is considered for sensor networked systems subject to distributed hybrid-triggered transmission scheme and input quantisation. A novel observer model based on coupled transmission signals from multi-channel is first proposed to estimate unavailable state variables and exploited in the feedback protocol. In order to provide a trade-off between saving network resources and improving system performance, a distributed hybrid-triggered transmission scheme with communication delays is adopted to update the observer input signals. For the sake of further reducing the occupancy of network resources, the control input signal is quantised by a logarithmic quantiser. Then, by making use of the Lyapunov stability theory, the sufficient conditions guaranteeing the system asymptotically stable are presented. Moreover, the explicit expressions of observer and controller parameters are achieved by solving a set of linear matrix inequalities. Finally, two simulation examples are provided to illustrate the rationality of the proposed control method.

This paper is engaged in investigating the observer-based event-triggered output feedback control issue for fractional-order cyber–physical systems with stochastic network attacks, where the order scale of the fractional derivative used is 0 α 1 . An event-triggered scheme (ETS) with output-independent threshold is proposed to renew the observer input so as to reduce the redundant data communications. Considering the effects of the ETS and network attacks, a novel closed-loop fractional-order control system model is constructed. By making use of fractional-order Lyapunov indirect approach, sufficient conditions that can insure the global stochastic asymptotic stability of the established closed-loop control system are obtained. Moreover, according to the singular value decomposition (SVD) of matrix, the co-design of the gains of the desired observer and controller is addressed by finding the solution of the linear matrix inequalities (LMIs). Finally, a numerical example and a diesel engine control system are provided to validate the feasibility of the adopted observer-based control method.

The additional damping ratio (ADR) is an important indicator for evaluating the damping effect of structures with energy-dissipation devices. Most existing methods for determining the ADR require an analysis of the structural dynamic response and complex iterative calculations. An innovative simplified calculation method for determining the ADR of a structure supplemented by nonlinear viscous dampers is proposed. This method does not require the dynamic response of the structure to be calculated and only requires the structural characteristics, excitation frequency, and damper parameters. In this study, several typical calculation methods for the ADR were analysed. Then, a calculation formula for the ADR was derived with consideration of harmonic excitation under the condition where the excitation frequency is equal to the structural natural frequency, without calculation of the structural dynamic response or an iterative process. The effect of the excitation frequency on the calculated value of the ADR with different damping exponents was studied. Accordingly, the response spectrum average period (RSAP) was considered as the excitation period of ground motion to evaluate the excitation frequency, and a simplified calculation method for the ADR considering the effect of the excitation frequency characterised by the RSAP of the ground motion was established. Finally, the accuracy and effectiveness of the proposed method were verified by comparison with ADRs calculated using other methods.

In order to improve the fault diagnosis theory of switched systems, observer-based method is proposed to deal with the fault diagnosis issue subjected to the parameter uncertainty, unknown process disturbances and unexpected faults. By employing proportional-integral observer (PIO) technique and the average dwell-time (ADT) method, an H∞/H− performance level is considered to ensure the worst case of robustness to the disturbance and sensitivity to the fault simultaneously. Moreover, the obtained fault diagnosis observer can give accurate fault estimation online for the piecewise constant fault. Finally, a two-tank system example is introduced in the end to show the effectiveness of the proposed results.

The paper is concerned with the observer-based robust control problem for fractional-order (FO) nonlinear uncertain systems subject to control input saturation and measurement quantization, in which the fractional commensurate order satisfies α ∈ ( 0 , 1 ) . The state measurements of observer are quantized by a logarithmic quantizer. Firstly, by introducing a continuous frequency distributed equivalent model of fractional integrator, sufficient condition for guaranteeing the asymptotic stability of closed-loop FO systems is established via the indirect Lyapunov approach. Then, by using matrix’s singular value decomposition (SVD) and linear matrix inequality (LMI) technique, the co-design problem of desired observer and controller gains are derived, which will be shown that the solution guarantees the stability of closed-loop FO nonlinear uncertain control systems. Finally, a simulation example is given to illustrate the validity of this method.

This paper investigates the problems of fault estimation and fault accommodation for a class of nonlinear switched systems. First, an augmented switched system is constructed by forming an augmented state vector composed of the state vector and the fault vectors. Then, an unknown input observer (UIO) is designed for the augmented switched system to estimate the augmented state vector. With the assist of the average dwell-time (ADT) method and the switched Lyapunov function technique, sufficient conditions are obtained to guarantee that the error system is globally uniformly asymptotically stable (GUAS) with a prescribed H∞ performance index. An algorithm is provided to show the procedures on how to design the UIO. Moreover, the results are extended to the measurement disturbances case. Based on signal compensation principle, a dynamic output feedback controller is designed to ensure the asymptotical stability of the closed-loop system. Finally, simulation results are presented to demonstrate the proposed technique.

The intensity non-stationarity is one of the basic characteristics of ground motions, the influences of which on the dynamic responses of structures is a pressing issue in the field of earthquake engineering. The BP neural network modified by the genetic algorithm was adopted in this research to investigate the influence of intensity nonstationary inputs on the structural dynamic responses from a new perspective. Firstly, many training data were generated from the prediction formula of dynamic response. The BP neural network was then pre-trained by sparsely selected data to optimize the initial weights and biases. Finally, the BP neural network was trained by all data, and the mean square error of predicted responses compared with the target response were less than 10−5. The calculation formula of sensitivity was also derived here to quantify the influence of the input change on the output. The presented method combines the advantages of neural networks in nonlinear multi-variable fitting and provides a new perspective for the study of earthquake nonstationary characteristics and their influence on the structural dynamic responses.

In this paper, the robust fault estimation observer problem for discrete-time switched systems with unknown input is investigated. First of all, The state vector and fault vector of the initial system are transformed into the state vector of the augmented system, and then we can obtain the augmented system. Next, an unknown input observer(UIO) is designed based on the P-radius technique to estimate the state and fault of the augmented system, that can ensure the stability of the error system. In order to achieve the exothermic goal in this paper, some assumptions are given, and the observer is solved by using linear matrix inequality (LMI) technique and Schur complement lemma. At the last, an interval hull computation approximation algorithm of fault estimation is obtained. Compared with other methods, this method is more precise and efficient.

In this paper, the problem of fault estimation for continuous-time switched system with actuator and sensor faults is investigated. Firstly, based on the average dwell-time method and switched Lyapunov function, a fault estimation observer is designed for the augmented switched system, which can ensure that the error system is asymptotically stable with an H ∞ performance index. Next, an algorithm is proposed to realize fault estimation accurately. Finally, an example is given to illustrate the effectiveness of the designed methods.

Insufficient grouting of sleeve connection in precast concrete (PC) structure will significantly decrease the bearing capacity of connection joints and increase the risk of premature failure of PC structures. To evaluate the bond behavior of insufficiently grouted sleeve connection, a total of 126 specimens with four types of insufficient grouting configuration (uniform, longitudinal, radial and inclined) have been experimentally investigated. The influences of the configuration and defect level of insufficient grouting on the bond failure mode and bond stress-slip curves were analyzed. The test results show that the specimens fail in the shifting failure mode from the tensile fracture of rebar to the pulling out of rebar with the increase of defect level for all types of grouting defects, especially when the defect level excesses 30%. Moreover, the bond strength and the slip are found to decrease with the increasing of defect level, and empirical expressions have been presented for both the normalized bond strength and slip. Finally, a bond stress-slip constitutive model has been proposed considering the failure modes under different defect levels, which is helpful to the assessment of structural performance of PC structures in practice.

This paper is concerned with the state feedback H∞ control problem for hybrid-triggered networked control systems (NCSs) with stochastic nonlinearity and state quantization. In order to establish a higher utilization of the network resources, a hybrid-triggered transmission scheme (HTTS) and measurement size reduction scheme are introduced. Firstly, the HTTS is presented such that the signal can be transmitted according to the law. Then the measurement size reduction scheme, i.e., the logarithmic quantization is applied. Then, considering the effect of HTTS and quantization, the original NCSs model is reformulated as a new hybrid-triggered NCSs with communication delay. By using Lyapunov functional method and linear matrix inequality technique, sufficient conditions for stochastical stability with a prescribed H∞ performance level are established, and the design of controller and trigger parameters can be obtained. Finally, a simulation example is given to illustrate the effectiveness of the proposed method.

The presence of cracks in concrete will accelerate the corrosion of steel reinforcement causing the performance degradation of reinforced concrete (RC) structure. Based on the electrochemical principle, a numerical model of macro-cell corrosion has been developed to predict the corrosion rate of steel reinforcement in cracked RC members. In this model, the areas of the separate anode and cathode are established by the crack width, and the electric resistivity of concrete material is modified by considering the effects of water-binder ratio and other factors. When the corrosion rate of steel reinforcement is taken as the mean value of the corrosion current density of anode zone, the corrosion rate can then be numerically solved from the proposed model with given boundary conditions. Test data from the 2-year laboratory experiments of authors and literature has been collected to verify the proposed model. The comparisons between the test and prediction results show that the proposed model is of capability to predict the corrosion rate with a good accuracy. Finally, the parametric studies show that the crack width, water/cement ratio, chloride concentration, thickness of concrete cover, and relative humidity has significant influences on the corrosion rate of reinforcement in cracked RC structure.

In this paper, the problem of fault detection filter design for a class of nonlinear switched systems is investigated. First, the nonlinear switched system is transferred into a Takagi–Sugeno fuzzy switched model by using fuzzy if-then rules. Then, based on the persistent dwell-time switching signal and the quasi-time-dependent Lyapunov function technique, an efficient condition of the performance analysis result is obtained. Based on this, a fuzzy-parameter-dependent fault detection filter is designed such that the resulting error system is globally uniformly asymptotically stable with a nonweighted $H_\infty$ performance index. Finally, simulation results are provided to show the effectiveness of the proposed technique.

This paper addresses the problem of H ∞ filter design for T-S fuzzy systems with saturation nonlinearities. For the purpose of reducing network burden, an output-dependent triggering scheme and a quantizer are introduced at the same time. The output-dependent triggering scheme is applied to determine whether or not the current instant information should be transmitted to the quantizer. Saturation nonlinearities, as a common phenomenon in networked systems due to the physical or technological constraints, is also considered here. Then a filtering error model with aforementioned characteristics is established. By using Lyapunov functional approach and stochastic analysis techniques, some matrix inequality-based sufficient conditions for the existence of the fuzzy filter are obtained. Moreover, a co-design algorithm for solving the suitable filter and the event generator is derived. Finally, a numerical example is provided to demonstrate the effectiveness of the proposed approach.

In this paper, the finite-frequency fault detection filter design for discrete-time switched systems is investigated. The frequencies of the faults and the unknown disturbance input are assumed to be finite and in three known intervals, qualified as low-, middle-, and high-frequency intervals. Based on the switched Lyapunov function and the generalized Kalman-Yakubovic-Popov lemma, efficient conditions are obtained to guarantee the existence of a finite-frequency fault detection filter, such that the error system is asymptotically stable with an H∞/H- performance index. Finally, a chemical reactor control system is employed to illustrate the obtained techniques.

In this paper, the problem of actuator fault detection for discrete-time switched systems with output disturbance is investigated. By using the descriptor observer method, an H∞ fault detection filter is designed to guarantee that the augmented system is admissible and satisfies a prescribed H∞ performance index. By utilizing switched Lyapunov function approach, a sufficient condition for the admissible of the augmented system is obtained. Based on the obtained results, a desired fault detection filter can be designed. All the results are formulated in the form of linear matrix inequalities. Finally, an example is proposed to illustrate the effectiveness of the developed method.

This paper investigates the problem of fault detection for the time-delayed networked systems. Different from the traditional fault detection systems, the considered system has the following feature: (i) the measured output of system is subject to sensor saturations; (ii) the system considers the influence of transmission delay and disturbance, which are two common phenomenon under the network environment; (iii) an output-dependent triggered scheme and measurement quantization are introduced in order to reduce the network bandwidth burden and improve communication efficiency. Considering aforementioned characteristics, a new type of fault detection filter model is builded. By constructing a Lyapunov functional, some new sufficient conditions for both the existence of above filter and the mean square stability of networked systems are obtained in terms of linear matrix inequalities (LMIs). Moreover, the suitable fault detection filter and the event generator can be co-designed simultaneously. Finally, a simulation example and an industrial continuous stirred tank reactor system are employed to verify the effectiveness and usefulness of the proposed method.

In this paper, the problems of sensor fault estimation and accommodation for discrete-time dynamic systems are investigated. Firstly, an augmented system is constructed where the sensor fault variable is added to the state vector. Then based on the descriptor observer technique, the efficient conditions of fault estimation under the disturbance and without the disturbance are both obtained. Finally, a static output feedback controller is employed to tolerate the sensor fault such that the closed-loop system is asymptotically stable. At last, a numerical example is provided to illustrate the proposed technique.

In this study, simplified numerical models are developed to analyze the soil-structure interaction (SSI) effect on frame structures equipped with viscoelastic dampers (VEDs) based on pile group foundation. First, a single degree-of-freedom (SDOF) oscillator is successfully utilized to replace the SDOF energy dissipated structure considering the SSI effect. The equivalent period and damping ratio of the system are obtained through analogical analysis using the frequency transfer function with adoption of the modal strain energy (MSE) technique. A parametric analysis is carried out to study the SSI effect on the performance of VEDs. Then the equilibrium equations of the multi degree-of-freedom (MDOF) structure with VEDs considering SSI effect are established in the frequency domain. Based on the assumption that the superstructure of the coupled system possesses the classical normal mode, the MDOF superstructure is decoupled to a set of individual SDOF systems resting on a rigid foundation with adoption of the MSE technique through formula derivation. Numerical results demonstrate that the proposed methods have the advantage of reducing computational cost, however, retaining the satisfactory accuracy. The numerical method proposed herein can provide a fast evaluation of the efficiency of VEDs considering the SSI effect.

This paper investigates the problem of actuator fault detection filter design for discrete-time linear systems with output disturbance. By using the descriptor observer method, an H∞ fault detection filter is designed to guarantee the residual system is admissible and satisfies the H∞ performance. By utilizing Lyapunov function approach, a sufficient condition for the admissible of the residual system is obtained in the form of linear matrix inequality (LMI). The desired fault detection filter can be designed by solving a set of LMIs. Finally, a numerical example is proposed to illustrate the effectiveness of the developed method.

The seismic response control of multistory frame structures using optimally placed viscoelastic dampers (VEDs) within consideration of soil-structure interaction (SSI) effect is investigated in this paper. The system is assumed to be elastic and responses of the system are obtained in frequency domain for stationary random seismic excitations. The optimal designs of VEDs in structures are achieved through genetic algorithm (GA) by minimizing the maximum response quantities of the system for a determined total amount of viscoelastic material. Two typical elastic multistory frame structures with different soil types and foundation embedment ratios are considered to demonstrate the optimization process. It is shown that the VEDs have the best control of the structural response for fixed base condition and the control efficiency decreases as the soil becomes softer. The optimal placement types of VEDs for different soil types differ from each other. With the decrease of soil stiffness, the optimal locations of VEDs have a tendency to shift to top floors.

A series of shaking table tests were performed to investigate the seismic behavior of the pre-fabricated steel frame structure infilled with autoclaved aerated concrete (AAC) external wall panels. The reliability of a new type of joint connections adopted in the structure between the steel frame and the wall panels was particularly validated during the test. Dynamic tests were carried out on a two-story full-scaled steel frame, considering seismic loading of three earthquake waves with different imposed peak accelerations in the range of 70[Formula: see text]cm/s2 to 400[Formula: see text]cm/s2. The experimental analyses encompassed cracking patterns, failure mechanisms, dynamic property and seismic response of the structure. The results show that the structural components, including the joint connections between the steel frame and the walls, behaved well even under the rare earthquake at 8∘. The structural stiffness of the steel frame infilled with wall panels was increased by 56%, compared with the steel frame infilled without wall panels. The damping ratio of the undamaged steel frame installed with wall panels was 7.25%.

In this paper, the problem of robust fault estimation observer design for continuous-time switched systems subject to unknown input is investigated. Firstly, based on the average dwell-time method and the switched Lyapunov function technique, an unknown input observer is designed for the augmented switched system by eliminating the unknown input, which can guarantee that the error system is globally uniformly asymptotically stable with a prescribed H∞ performance index. Next, the method is extended to the measurement disturbances case. Finally, an example is presented to illustrate the design and efficiency of the proposed fault estimation observer technique.

Previous researchers have made a lot of contributions on carbonation reaction. However, effects of multi-cracks and interfacial transition zone (ITZ) on the diffusivity of carbon dioxide are critical and thorny problems. In this study, numerical simulation of carbonation process using the COMSOL Multiphysics are presented based on in-situ 3D microstructure evolution of X-ray CT. Firstly, micro X-ray computed tomography (X-ray CT) was used to monitor the carbonation depth evolution of cement mortar with different additions of blast furnace slag (BFS). It is shown that the optimal addition of blast furnace slag (BFS) against the carbonation is no more than 50%. In addition, COMSOL Multiphysics numerical model based on micro X-ray CT image was used to investigate effects of transverse crack and interfacial transition zone (ITZ) on the diffusivity of carbon dioxide. Finally, effects of different crack width, length, ITZ of polygon Random Aggregate Structure (RAS), and aggregate size and content on the diffusivity of carbon dioxide have been investigated.

This paper investigates the problems of actuator fault estimation and accommodation for discrete-time switched systems with state delay. By using reduced-order observer method and switched Lyapunov function technique, a fault estimation algorithm is achieved for the discrete-time switched system with actuator fault and state delay. Then based on the obtained online fault estimation information, a switched dynamic output feedback controller is employed to compensate for the effect of faults by stabilizing the closed-loop systems. Finally, an example is proposed to illustrate the obtained results.

This paper investigates the state estimation problem of Markovian jump systems with time-varying delay. The purpose is to design a state estimator to estimate system states through available output measurements. A novel event-triggered scheme is proposed, which is used to determine whether the sampled state information should be transmitted. The main idea is that the proposed event-triggered scheme provides a supervision of the system state in discrete instants and the newly sampled sensor measurements violating specified triggering condition will be transmitted to the estimator. Firstly, a state estimation model is constructed which describes the transmission delay, Markov parameters and an event-triggered mechanism in a unified framework. Secondly, based on the model, the criteria for the exponential mean square stability are proposed by using Lyapunov functional method and convexity property of the matrix inequality. Under the obtained conditions and the event-triggered scheme, the desired state estimator of Markovian jump systems with time delay is established by solving some linear matrix inequalities. Finally, a numerical example is given to illustrate the effectiveness of the proposed method.

An innovative retrofit scheme is proposed for the strengthening of old brick masonry buildings: the floor area is increased using newly added and isolated upper stories, and the lower brick masonry part is strengthened using precast concrete wall panels. To investigate the seismic performance of the innovative proposed strengthening scheme, a theoretical analysis and shaking-table tests were conducted, and the proposed scheme is compared with two conventional retrofitting schemes. The results of linear and nonlinear analyses of the three strengthening schemes indicated that all three schemes can mitigate seismic damage to old brick masonry buildings. The shaking-table tests confirmed that the proposed scheme is more effective than the two conventional schemes. Additionally, the seismic performance of the proposed strengthening scheme with post-test damage is investigated via a theoretical analysis and shaking-table tests. The results revealed that the stiffness degradation of the substructure can negatively affect the adding-story isolation system.

At present, the engineering designers generally design and analyze the precast structural models according to the equivalent cast-in-situ principle, and have a vague understanding of non-identical problems. However, these issues cannot be ignored, especially for high-intensity areas. This paper considers the differences of the hysteretic relationship between two typical precast joints and cast-in-situ (RC) joints, and researches the influence of these differences on the seismic response of frame structures. For the monolithic precast joint, the force mechanism was analyzed based on its assembly form, and the differences with the RC joint in the testing phenomena were explained accordingly. The dimensionless hysteresis models of two types of joints were proposed, and the rationality of the monolithic precast joint model was verified according to the existing experimental results. Different performances of joints were realized by assigning the constitutive models calculated from sectional reinforcement to the spring elements of analysis models. Considering two possible performance deficiencies of each type of precast joint separately, a total of seven structural analysis models were formed. Nonlinear static analysis and dynamic time-history analysis methods were adopted to reveal the differences between precast frames and the RC frame in terms of structural capacity curve, displacement response, ductility demands of components and structural residual deformation. The results showed that under strong seismic excitation, the response differences between precast frames and the RC frame were significant, so it is worthwhile to establish nonlinear models suitable for precast frames in seismic analysis. This study is valuable for understanding and distinguishing the nonlinear response of precast frames and traditional RC frames.

In this paper, the problems of fault estimation (FE) observer and optimal fault tolerant controller (FTC) design for singular perturbation switched systems are addressed. Firstly, an augmented system is constructed for actuator fault, sensor fault and system state. Then, based on the average dwell-time (ADT) method and the switched Lyapunov function technique, a proportional integral (PI) observer is designed for the augmented system. Furthermore, sufficient conditions are obtained to guarantee that the error system asymptotically stable with $H_{\infty}$ performance. An algorithm for the PI observer design is proposed. Finally, an optimal fault tolerant controller is engineered to ensure that the closed-loop system have optimal performance.

The bond behavior of deformed bar in concrete is important for the design and analysis of concrete structures, especially with insufficient concrete cover or confinement. This paper presents an analytical solution for the bond strength of deformed bar in concrete due to the splitting failure of concrete cover. A hypothesis of the equivalent elastic deformation field is proposed to approximate the deformation within the inner cracked concrete, while a linear crack profile is assumed to formulate the width of fictitious cracks. In conjunction with a realistic softening relationship, the analytical solutions of the internal pressure and bond strength are then derived for the splitting failure. The comparisons between the analytical predictions and the extensive experimental results demonstrate that the presented analytical model is capable of predicting the bond capacity with good accuracy. Finally, the influences of geometric and material parameters on the prediction results are examined, and an expression for the required bonded or splice length is suggested for design applications.

This paper considers the problem of robust fault estimation for discrete-time switched system. Firstly, an augmented system is constructed such that the fault as part of the state. Then an unknown input observer (UIO) is employed to estimate the state of the augmented system. Based on the switched Lyapunov function and the generalized Kalman-Yakubovic-Popov (KYP) lemma, a finite-frequency UIO-based fault estimation observer is designed. Finally, the proposed technique is illustrated by a numerical example.

This paper deals with the problem of actuator fault estimation observer design for discrete-time switched systems with finite-frequency. The frequencies of the fault and the unknown input disturbance are assumed to be in a finite range. A finite frequency fault estimation observer is proposed to estimate the actuator fault in the entire frequency domain. Based on the generalized Kalman–Yakubovic–Popov (KYP) lemma and the switched Lyapunov function method, the efficient conditions are obtained to achieve the fault estimation observer design. Finally, an example is given to illustrate the proposed technique.

The improvement effect of a new strengthening strategy on dynamic action of masonry structure, by installing prefabricated concrete walls on the outer facades, is validated by shaking table test presented in this paper. We carried out dynamic tests of two geometrically identical five-story reduced scaled models, including an unstrengthened and a strengthened masonry model. The experimental analysis encompasses seismic performances such as cracking patterns, failure mechanisms, amplification factors of acceleration, and displacements. The results show that the strengthened masonry structure shows much more excellent seismic capacity when compared with the unstrengthened one.

Seismic isolation technology is being applied in large long-span-structured public buildings more and more often worldwide. Aimed to investigate the horizontal and vertical dynamic response of long-span gird structure, the shaking table tests of 1/20 scale long-span grid structures with and without base-isolation considering horizontal two-dimensional (2D) and three-dimensional (3D) seismic excitations were conducted. The test model was designed as ordinary long-span spatial grid structure, but with lead rubber bearings. Data on the acceleration, displacement, strain, and shear force of the base-isolation model and fixed-base model were collected and compared. The dynamic responses of the structure subjected to the horizontal and vertical ground motions with different intensities were studied. The experimental results showed that compared with the fixed-base model, the horizontal period and damping ratio of the base-isolation model can be significantly improved, reducing the horizontal dynamic response of the superstructure, and the horizontal isolation effect was improved with the increase of the seismic excitation intensity. The horizontal acceleration of the roof layer for the base-isolation model was amplified in 3D excitation compared to horizontal input due to horizontal-vertical coupling. Meanwhile, significant vertical acceleration and displacement responses of long-span roof for fixed-base structure were induced by horizontal seismic excitation. Although base isolation could not provide protection against vertical excitation, vertical isolation effect under 3D input could be achieved by effectively suppressing the vertical dynamic response of grid roof induced by the horizontal seismic component.

International audience; This paper investigates the problem of fault detection filter design for discrete-time switched systems with interval time-varying delays. The residual generator is constructed based on a mode-dependent fault detection filter, i.e., the designed fault detection filter is also a switched system as well. By constructing a novel switched Lyapunov functional, a new criterion is obtained for the residual system. Based on this, a sufficient condition for the existence of the above filter is established in terms of linear matrix inequalities (LMIs). The designed fault detection filter can guarantee the difference between the generated residual signal and the fault signal as small as possible. An example is provided to illustrate the effectiveness of the proposed method.

Based on the shaking table test of 1:20 scale structural models of the large-span isolated and non-isolated flat grid structures under the action of horizontal-bidirectional (2D) and three-dimensional (3D) rare earthquake, the dynamic characteristics, including natural vibration frequency, damping ratio, the acceleration and displacement responses are investigated. The results show that the base isolation could significantly prolong the structural vibration periods and increase the damping ratio. The capacity of energy dissipation for the base-isolated structure can also be improved. The horizontal acceleration amplification factors (AAFs) of the structure can be reduced greatly due to the base isolation, which effectively reduces the vertical vibration of the large-span grid. Under the 3D seismic input, the horizontal AAF of each layer is greater than that under the 2D one, which illustrates that the vertical seismic input increases the horizontal dynamic response of the structure. Furthermore, the finite element models of the isolated and non-isolated structures were simulated. The experimental results are in good agreement with the numerical results. The parameter optimization of isolation bearings was conducted by using finite element software. The seismic response of each layer under different shear to weight ratios (μ) was analyzed. It can be found that the parameters of the isolation layer have an optimal range which makes the dynamic response of the structure reach a minimum value under the rare earthquake.

Recent developments in particle astrophysics and cosmology are described, with an emphasis on new observations and their impacts on the way we formulate the main open questions in the field.