Response Of Civil Engineering Structures Research Articles

LSTM, WaveNet, and 2D CNN for nonlinear time history prediction of seismic responses

Predicting the nonlinear time-history responses of civil engineering structures under seismic loading remains an essential task in earthquake engineering. This paper explores the promise of developing three deep learning (DL) models, i.e., long short-term memory (LSTM), WaveNet, and 2D convolution neural network (CNN), to predict seismic response time histories of three benchmark structures, including a single degree-of-freedom (SDOF) system, a steel building frame, and a multi-component bridge structure. LSTM has been previously developed and is utilized to serve as a reference model, while WaveNet and 2D CNN (i.e., it deals with the data in coupled time–frequency dimensions) are newly developed in the current study. One other novel contribution is to replace the final layer of the WaveNet with an LSTM layer, which significantly improves the model performance. Methodological backgrounds of these DL models are introduced, followed by discussions on model architectures and hyperparameters, the list of evaluation metrics, and the ground motion (GM) suite selected for data generation. High-fidelity numerical models are developed for conducting nonlinear time history analyses that generate numerous motion-response pairs for training, validating, and testing the DL models. The LSTM and WaveNet directly use time series GM inputs and seismic response outputs to train the models, whereas the CNN makes inferences on time–frequency spectrogram images converted through the short-time Fourier transform (STFT). These three DL models are investigated by comparing deterministic predictions under one testing GM and probabilistic distributions of six evaluation metrics. The models’ accuracy, efficiency, and robustness are further examined using a sensitivity study under different training samples and model architectures. Research findings from this study provide a sound reference for the community to leverage these three DL models to achieve reliable and efficient time history response predictions, which are crucial for fulfilling cutting-edge research/practical tasks such as regional seismic risk assessment and performance-based seismic design.

Probabilistic model updating via variational Bayesian inference and adaptive Gaussian process modeling

The estimation of the posterior probability distribution of unknown parameters remains a challenging issue for model updating with uncertainties. Most current studies are based on stochastic simulation techniques. This paper proposes a novel variational Bayesian inference approach to estimate posterior probability distributions by using the vibration responses of civil engineering structures. An adaptive Gaussian process modeling technique is used to represent the “expensive-to-evaluate” likelihood function, and the unknown posterior probability distribution is represented using a Gaussian mixture model. The evidence lower bound (ELBO) and its gradients can be computed analytically using the built Gaussian process and mixture models. The unknown parameters in the Gaussian mixture model can be identified by maximizing the value of ELBO. The stochastic gradient descent method is applied to perform the optimization. Numerical studies on an eight-story shear-type building and a simply supported beam are conducted to verify the accuracy and efficiency of using the proposed approach for probabilistic model updating and damage identification. Experimental studies on a laboratory steel frame structure are also conducted to validate the proposed approach. Results demonstrate that the posterior probability distributions of the unknown structural parameters can be successfully identified, and reliable probabilistic model updating and damage identification can be achieved.

The Torsional Response of Civil Engineering Structures during Earthquake from an Observational Point of View

The Torsional Response of Civil Engineering Structures during Earthquake from an Observational Point of View

The Torsional Response of Civil Engineering Structures during Earthquake from an Observational Point of View.

This paper discusses the origins of torsion and its effect on the response of structures with a focus on the contribution of experimental data. The fact that torsion increases the stresses in structures, augmenting strain and damage during earthquakes, was confirmed in the 1960s. Over the years, the torsional response of structures has mainly been analysed through numerical studies, because few buildings are equipped with translational sensors, and even fewer are equipped with rotational sensors. This is likely to change as building instrumentation becomes more widespread and new generations of rotational sensors are developed. Therefore, this paper focusses on a number of scientific questions concerning the rotational response of structures during earthquakes and the contribution of experimental data to the understanding of this phenomenon.

Parameter identification of the dynamic Winkler soil–structure interaction model using a hybrid unscented Kalman filter–multi-objective harmony search algorithm

Soil–structure interaction is a key aspect to take into account when simulating the response of civil engineering structures subjected to dynamic actions. To this end, and due to its simplicity and ease of implementation, the dynamic Winkler model has been widely used in practical engineering applications. In this model, soil–structure interaction is simulated by means of spring–damper elements. A crucial point to guarantee the adequate performance of the approach is to accurately estimate the constitutive parameters of these elements. To this aim, this article proposes the application of a recently developed parameter identification method to address such problem. In essence, the parameter identification problem is transformed into an optimization problem, so that the parameters of the dynamic Winkler model are estimated by minimizing the relative differences between the numerical and experimental modal properties of the overall soil–structure system. A recent and efficient hybrid algorithm, based on the combination of the unscented Kalman filter and multi-objective harmony search algorithms, is satisfactorily implemented to solve the optimization problem. The performance of this proposal is then validated via its implementation in a real case-study involving an integral footbridge.

METACity‐Quito: A Semi‐Dense Urban Seismic Network Deployed to Analyze the Concept of Metamaterial for the Future Design of Seismic‐Proof Cities

ABSTRACTThe presence of multiscale interactions means that the complex urban wavefield must be observed and analyzed in order to understand seismic ground motion in urban environments. Originally called site–city interaction, the interactions between soil and structures, structures and soil, and between structures contribute to the modification of urban seismic ground motion. This may affect the lateral variability of the ground motion observed in relation to earthquake damage, the characterization of site effects in urban areas, and also the response of civil engineering structures designed without consideration of the immediate urban environment. The METACity‐Quito experiment was designed to take accurate measurements of the effects of the resonator array formed by structures in the seismic wavefield, in the manner of an urban metamaterial. Current applications in the fields of physics, acoustics and, more recently, geophysics have shown the existence of forbidden bands, that is, frequencies at which seismic energy vanishes. This concept could help to understand the heterogeneous distribution of damage in urban areas as well as to imagine the future design of seismic‐proof cities.

Passive damping of suspension bridges using multi-degree of freedom tuned mass dampers

Tuned Mass Dampers (TMDs) are a very popular, economical and robust way of mitigating the dynamic response of civil engineering structures. However, their classical implementation involves as many TMDs as there are critical modes. This paper analyzes a TMD with two degrees of freedom targeted at mitigating simultaneously a bending and a torsion mode of a bridge deck. The system parameters can be tuned independently for the bending and the torsion mode. The study is conducted numerically and experimentally on a laboratory mock-up of a suspension bridge.

Investigation of Geographical impact on Power Dissipation during simulation of Electronics Design on 28nm FPGA

In this paper, an optimal control matrix, based on the modified differential equation of Riccati, will be formulated, for the active isolation analysis of structures subjected to earthquakes, and a passive mechanical isolator device which is will be also proposed. The combination of the active and the passive isolators compose a Semi-Active Variable Stiffness and Friction Isolator (SAVSFI) model which proposed for the nonlinear analysis of structures subjected to earthquakes. The active feedback gain is determined in terms of the optimal control matrix for which with the passive device model present indeed, new propositions to reduce actively and semi-actively the effect of earthquakes on the responses of civil engineering structures. Three examples of structures (two buildings and a bridge) have been analyzed for the three uncontrolled, active-controlled and semi-active-controlled cases and subjected to a strong earthquake. The results obtained either displacements or stresses for the active and the semi-active cases, show good and excellent reductions, in comparison with those deducted for the uncontrolled cases. This good reduction of the effect of such strong earthquake would be turns to the good formulation of the optimal active feedback gain computed and to the good passive mechanical model proposed.

Analysis of the Response of a Frame Structure during an Earthquake Using the Transfer Matrix Method of a Multibody System

AbstractFinite-element methods such as ANSYS are widely used in traditional structural dynamic analysis. The low computational efficiency of ANSYS is a hindrance in finite-element methods when computing the responses of special engineering structures. This paper details an innovative study in which the transfer matrix method of multibody system (MS-TMM) is introduced to analyze the dynamic response of civil engineering structures. Although the responses obtained by the MS-TMM are similar to the responses obtained by ANSYS, ANSYS requires a larger computation time. The results indicate that the MS-TMM can satisfy the computation efficiency and calculation accuracy requirements.

Dynamic Monitoring of Concrete Structure Using Piezoelectric Sensor

Dynamic response of civil engineering structures was monitored in the paper, on basis of the excellent properties of piezoelectric smart sensor. There were two experiments: One was to study the relationship between the loading frequency and the piezoelectric sensor output by concrete block cyclic loading test; the other was to study the relationship between the sensor output and the stress amplitude by steel cantilever beam dynamic test. The results show that piezoelectric sensors have a good linear output performance.

Optimum tuning of Tuned Mass Dampers for frame structures under earthquake excitation

Tuned Mass Damper (TMD) devices are one of the oldest vibration control means and are widely used in different engineering contexts. Despite the bulk of literature on various TMD-related issues, the effectiveness of TMDs in reducing the earthquake response of civil engineering structures is still debated. This paper deals with the optimum tuning of the free parameters of a passive TMD applied to sample frame structures subjected to selected seismic excitations. A tuning procedure consisting of a numerical Minimax optimization algorithm is implemented within MATLAB. The so-conceived TMD turns out to be optimum with respect to the specific seismic event, hence allowing for optimum reduction in primary seismic response. Both optimization process and seismic analysis are carried out in the time domain, through direct integration of the equations of motion. The method is tested on benchmark single-DOF and multi-DOF shear-type prototype structures from the literature by assuming first the Imperial Valley 1940 seismic input, as a sort of benchmark excitation, and then additional recent strong motion earthquakes. In essence, this paper shows that, in principle, with present reference to frame structures, the optimum tuning of TMD parameters at given seismic input is theoretically possible.

The response of embedded strain sensors in concrete beams subjected to thermal loading

A wide range of commercially available sensors are frequently used to record the response of civil engineering structures that may be subjected to unexpected loading scenarios, changes of environmental conditions or material deterioration. However, a common problem faced when using these sensors is to distinguish strain changes experienced by the structure due to a temperature change from strain changes that occur due to other causes. Temperature effects on strain sensors are usually accommodated by allowing for temperature effects (temperature compensation); however, there is limited research in the literature that investigates the performance of strain sensor measurements when subjected to temperature change. Understanding the temperature effect on strain sensors will greatly enhance the ability of civil engineers to monitor the performance of structural materials. In this paper, different types of commonly used and advanced strain sensors have been installed in a reinforced concrete beam to measure the thermal strain response of concrete under different temperature conditions. The experimental results demonstrated a 25–30% difference in strain measurements from the different sensors. It is shown in this paper that this difference is due to the combined effects of sensor inaccuracy, uncertainties related to the testing conditions and uncertainties associated with the temperature compensation methods.

A state-of-the-art review of structural control systems

The utilization of structural control systems for alleviating the responses of civil engineering structures, under the effects of different kinds of dynamics loadings, has become a standard technology, although there are still numerous research approaches for advancing the effectiveness of these methodologies. The aim of this article is to review the state-of-the-art technologies in structural control systems by introducing a general literature review for all types of vibrations control systems that have appeared up to now. These systems can be classified into four main groups: (a) passive; (b) semi-active; (c) active; and (d) hybrid systems, based on their operational mechanisms. A brief description of each of these main groups and their subgroups, with their corresponding advantages and disadvantages, is also given. This article will conclude by providing an overview of some innovative practical implementations of devices that are able to demonstrate the potential and future direction of structural control systems in civil engineering.

Multi-stage identification scheme for detecting damage in structures under ambient excitations

Structural damage identification methods are critical to the successful application of structural health monitoring (SHM) systems to civil engineering structures. The dynamic response of civil engineering structures is usually characterized by high nonlinearity and non-stationarity. Accordingly, an improved Hilbert–Huang transform (HHT) method which is adaptive, output-only and applicable to system identification of in-service structures under ambient excitations is developed in this study. Based on this method, a multi-stage damage detection scheme including the detection of damage occurrence, damage existence, damage location and the estimation of damage severity is developed. In this scheme, the improved HHT method is used to analyse the structural acceleration response, the obtained instantaneous frequency detects the instant of damage occurrence, the instantaneous phase is sensitive to minor damage and provides reliable damage indication, and the damage indicator developed based on statistical analysis of the Hilbert marginal spectrum detects damage locations. Finally, the response sampled at the detected damage location is continuously analysed to estimate the damage severity. Numerical and experimental studies of frame structures under ambient excitations are performed. The results demonstrate that this scheme accomplishes the above damage detection functions within one flow. It is robust, time efficient, simply implemented and applicable to the real-time SHM of in-service structures.

Analysis of Elastic-Plastic Responses of a New Single-Story Frame-Bent Structure during an Earthquake Based on the Transfer Matrix Method of Multibody System

Finite element methods, such as the ANSYS, are widely used as traditional structural dynamic analysis methods. Due to the low calculation efficiency of the ANSYS, there is a hindrance factor in using the finite element method to compute the elastic-plastic responses of special engineering structures. In this paper, we detail a pioneer study in which the transfer matrix method of multibody system (MS-TMM) was introduced to analyze the dynamic responses of civil engineering structures. Although the responses obtained by the MS-TMM are similar to the responses obtained by the ANSYS, the ANSYS requires a greater amount of computation time. The results indicate that the MS-TMM can satisfy the requirements of calculation efficiency and calculation accuracy.

Cost-effective vision-based system for monitoring dynamic response of civil engineering structures

This study develops a cost-effective vision-based displacement measurement system for real-time monitoring of dynamic responses of large-size civil engineering structures such as bridges and buildings. The system simply consists of a low-cost digital camcorder and a notebook computer equipped with digital image-processing software developed in this study. A target panel with predesigned marks is attached to a structure, whose movement is captured by the digital camcorder placed at a fixed point away from the measurement point. The captured images are streamed to the notebook computer and processed by the software to compute displacement in real time. The efficacy of the system in measuring dynamic responses was demonstrated through laboratory tests, seismic shaking table tests on a steel building frame, and a field experiment on a bridge. In order to simultaneously measure displacements of multiple points, this study further developed a time synchronization system, in which TCP/IP protocol is employed for communications. The effectiveness of the time synchronization system was also experimentally verified. The vision-based system developed in this study is simple, cost-effective, easy to install, and capable of real-time measurement of dynamic responses, making the system ideal for monitoring civil engineering structures. Copyright © 2009 John Wiley & Sons, Ltd.

Adaptive base-isolation of civil structures using variable amplification

Semi-active dampers are used in base-isolation to reduce the seismic response of civil engineering structures. In the present study, a new semi-active damping system using variable amplification will be investigated for adaptive base-isolation. It uses a novel variable amplification device (VAD) connected in series with a passive damper. The VAD is capable of producing multiple amplification factors, each corresponding to a different amplification state. Forces from the damper are amplified to the structure according to the current amplification state, which is selected via a semi-active control algorithm specifically tailored to the system’s unique damping characteristics. To demonstrate the effectiveness of the VAD-damper system for adaptive base-isolation, numerical simulations are conducted for three and seven-story base-isolated buildings subject to both far and near-field ground motions. The results indicate that the system can achieve significant reductions in response compared to the base-isolated buildings with no damper. The proposed system is also found to perform well compared to a typical semi-active damper.

Predictive Control of Structures

Different continuous‐time approaches have been proposed in recent years to formulate active control algorithms to reduce the response of civil engineering structures under dynamic excitations. In this paper, a general formulation of a new discrete‐time control methodology is presented and applied to structural control. This methodology, based on the concept of predictive control, is discussed and compared to the optimal control methodology by means of numerical examples.

Use of a very-high-resolution tiltmeter for the study of the response of civil engineering structures (In French) : Aste, J P; Blum, P A; Bordes, J L; Memier, B; Salch, B Rev Fr Geotech N34, 1986, P57–67

Use of a very-high-resolution tiltmeter for the study of the response of civil engineering structures (In French) : Aste, J P; Blum, P A; Bordes, J L; Memier, B; Salch, B Rev Fr Geotech N34, 1986, P57–67