Structural Response Research Articles

Nearby Real-Time Earthquake Simulation on an Urban Scale Based on Structural Monitoring

The real-time input of ground motions can effectively assess earthquake disasters in building structures. In this study, we proposed a nearby real-time simulation method that can be applied to assess regional earthquake disasters using structural monitoring recordings based on an urban earthquake simulation system. Real-time accelerations recorded during the 5.1 magnitude Tangshan earthquake were used to update and modify the computing models. El Centro waves were calibrated to 400 cm/s2 for structural seismic resilience analyses. The results indicated that approximately 70% of the structural functions were lost during the rare earthquake. Regional numerical models of 216 buildings were constructed and timeously updated using a geographic information system and measured data. The inputting ground motions recorded in the 5.1 magnitude Tangshan earthquake and typical El Centro waves were selected to analyze the structural seismic response, in which the damage indexes were computed, and the damage predictions of the regional 216 buildings were also simulated in different levels of earthquakes by being combined with the simplified principles of structural damage estimation. Finally, the evaluation results were visualized in three dimensions using ParaView software. The simulated results of earthquake disasters at an urban scale will promote the prediction abilities of local earthquake administration agencies and have considerable potential to provide essential information for emergency responses and regional disaster mitigation.

Predictive modeling for hat-stiffener delamination during low velocity impact

Barely visible impact damage poses a significant threat to composite structures, particularly prevalent in the aerospace industry. The occurrence of low velocity impact (LVI) events can lead to substantial deformations in composite structures, causing interlaminar delamination and diminishing their compression load carrying capacity. Beyond LVI-induced interlaminar delamination, it is crucial to investigate failures occurring between co-cured composite structures. This study focuses on hat-stiffened coupon structures, to investigate the delaminating phenomenon between the hat and skin components. The outcomes of experimental results inform the development of a finite element model, enabling to capture the structural response and delamination dynamics. The primary objective of the experiments is to understand the delamination process which occurs suddenly upon impact. LVI experiments are conducted to understand the structural behavior at varied impact locations. A mesh study establishes the relationship between cohesive parameters and element size in the model to enable computational efficiency by avoiding the need for a highly refined mesh. When the mesh is relatively coarse, the finite element model’s capability to resolve stresses at near singular locations is limited, however the computational time is lower. Therefore, the balance between computational efficiency on the one hand, and resolving gradients on the other, requires a fine balance in order to carry out a large number of design iterations efficiently. This research significantly contributes to advancing our understanding of delamination mechanisms at free edges in composite structures, offering valuable insights for computational modeling.

Numerical Study of Air Cushion Effect in Notched Disk Water Entry Process Using Structured Arbitrary Lagrangian–Eulerian Method

This paper presents a novel numerical investigation into the air cushion effect and impact loads during the water entry of notched discs, utilizing the Structured Arbitrary Lagrangian–Eulerian (S-ALE) algorithm in LS-DYNA. Unlike prior studies that focused on smooth or unnotched geometries, the present study explores how varying notch parameters influence the fluid–solid coupling process during high-speed water entry. The reliability and accuracy of the computational method are validated through grid independence verification and comparisons with experimental data and empirical formulas. Systematic analysis of the effects of notch size, water entry velocity, and entry angle on the evolution of the free surface, impact loads, and structural responses uncovers several novel findings. Notably, increasing the notch diameter significantly enhances the formation and stability of the air cushion, leading to a considerable reduction in peak impact loads—a phenomenon not previously quantified. Additionally, higher water entry Froude numbers are shown to accelerate air cushion compression and formation, markedly affecting free surface morphology and force distribution. The results also reveal that varying the water entry angle alters the air cushion’s morphological characteristics, where larger angles induce a more pronounced but less stable air cushion, influencing the internal structural response differently across regions.

Response and seismic resilience of metro tunnels under normal fault dislocation evaluated based on the quantitative method of concrete damage state

The damage to tunnels crossing active fault zones caused by earthquakes can be of a severe and irreversible nature. The paper defines the quantification of the concrete damage state based on the uniaxial compression equation and the tensile-compression curve equation. Furthermore, the paper refines the concrete damage level in conjunction with the damage factor and crack width formulas, which is one of the most significant factors affecting the durability of concrete. A three-dimensional refinement model, constructed using ABAQUS software, was employed to analyse the mechanical response and seismic resilience of the tunnel structure under normal fault displacement with variable section mitigation measures. The model incorporated a number of key parameters, including fortification length, joint location and thickness. The following conclusions were obtained: the tunnel structure is susceptible to tensile damage and the damage is widely distributed under normal fault d; the use of variable section measures can help improve and reduce the overall damage of the cross-fault metro tunnel structure; the use of tensile damage state classification to assess the damage of the tunnel structure can determine the location and extent of the damage; an appropriate protection length is required, too long/short does not maximise the mitigation effect of setting variable section measures; an appropriate lining length is required; and the lining structure is not suitable for the tunnel structure. An appropriate location and thickness of the lining structure will help to reduce the overall damage to the structure. The application of localised reinforcement to the structure, in conjunction with variable section, serves to minimise the probability of collapse of the tunnel as a whole and to enhance the seismic resilience of the underground structure across the active fault zone.

Structural damage detection using a sensitivity-based model updating approach with autocorrelation function data

ABSTRACT This study presents a novel sensitivity equation for estimating structural parameters using autocorrelation function (ACF) data of dynamic responses. The proposed method reduces the need for extensive excitation frequencies, making structural parameter identification more practical and cost-effective, especially for large-scale structures. Furthermore, due to the quadratic relationship between ACF and the structural dynamic response, this approach exhibited greater sensitivity to damage than time-history-based methods. The method’s effectiveness was evaluated using simulated data from truss and offshore jacket platform models. Incomplete measurements were addressed by using partially measured structural characteristics without model reduction and data expansion processes. Measurement and modelling errors were simulated by adding uniformly distributed random error into the damaged structure data. The low values of the coefficient of variation indicated the method’s robustness against these errors. The accuracy of the method was confirmed through low root mean square error (RMSE) values and high variance accounted for (VAF) values.

Finite element modeling to explore static bending responses of four-layer FG beam structures considering sliding motions

Finite element modeling to explore static bending responses of four-layer FG beam structures considering sliding motions

Nonlinear finite element model updating and fourier neural operator for digital twin of reinforced concrete containment vessel under seismic excitations

A series of unidirectional seismic excitation tests on a 1/20 scaled reinforced concrete containment vessel (RCCV) specimen was conducted using a 6-DOF shake table. This study presents the development of a digital twin to accurately capture the complex behavior of reinforced concrete structures under seismic effects. With the aid of finite element (FE) software Abaqus, the RCCV structure was initially modeled and analyzed to obtain preliminary structural acceleration and displacement results. To enhance the accuracy of these simulations, a nonlinear FE model updating framework was developed by integrating Abaqus software with Python. The model updating of RCCV was conducted subsequently based on the shake table measured data to obtain results with significantly improved accuracy. It is shown that the FE simulations and the nonlinear FE model updating algorithm are highly effective for the high-fidelity simulation of large and complex structures. Furthermore, a Fourier neural operator (FNO) model is used to learn the FE simulation database and predict the FE simulation results. It is observed that FNO has an excellent performance in predicting the structural responses with various material and damping parameters and accomplished speedup over 5000 times compared to the FE simulations. The findings provide a basis for the application of nonlinear model updating algorithms at the structure system level through the high-performance GPU-based parallel computing and underscore that the strategy of FE analysis combined with artificial intelligence (AI) has great potential in the field of digital twins for large and complex structures.

Exact Solution of Nonlinear TVMD Based on Maximizing Damping Enhancement Effect for Acceleration Response Control

The tuned viscous mass damper (TVMD) exhibits superior control effect and energy dissipation capability compared to the viscous damper (VD). Existing literature has primarily focused on the control of absolute acceleration response in structures by linear TVMD, with limited research on nonlinear damper for controlling structural performance and efficiency. This study proposes a methodology for determining the optimal parameters of linear TVMD. The closed-form solution of the nonlinear TVMD is derived through stochastic linearization based on the linear TVMD, aiming to minimize the damping ratio of TVMD by utilizing the damping enhancement effect of the system. For lightly damped structures, the closed-form solution remains a reliable method for accurately approximating TVMD design parameters. Compared to traditional fixed-point theory, the TVMD developed through the proposed methodology demonstrates superior control performance, especially in terms of absolute acceleration, with a smaller damping ratio and minimal deviation from the optimal state of the TVMD. Additionally, the study investigated the influence of the damping index on the optimal parameters and the efficacy of the TVMD in vibration control. It is observed that reducing the damping index can improve structural performance, particularly in long-period structures with small mass ratios, although it may reduce the efficiency of the TVMD. Notably, TVMDs with lower mass ratios maintain higher efficiency regardless of the structural natural period. The damping index does not affect the optimal frequency ratio or the mean square response. Ultimately, the effectiveness of the optimization method is displayed through the examination of response spectra following 22 real seismic events, showcasing its adaptability across various structural types. The comparison of the root-mean-square response between the VD and TVMD across different periods shows consistent results, with a maximum deviation of only 10%. The TVMD is highly effective at regulating the structural response, excelling particularly in controlling the absolute acceleration of long-period structures, where it reduces maximum absolute acceleration by 20% more than displacement. The proposed exact solution rapidly and precisely identifies the design parameters of nonlinear TVMD by the desired specifications, thereby offering theoretical guidance for practical engineering applications.

Detection of Nonlinearity in Photonic Lattices

AbstractAlthough periodic photonic structures, especially associated with nonlinearity, play a prominent role in optics nowadays, effective detection of their nonlinearity still remains a critical challenge. Here, an approach is proposed to detect the nonlinearity of photonic lattices in a direct way. By properly launching structured beams, namely Airy beams, into the lattices, the nonlinear response function of the discrete system can be directly obtained in the nonlinearly‐shaped beam profiles. To be specific, a single Airy beam is utilized to map self‐defocusing nonlinearity, while self‐focusing nonlinearity, which is hard to visualize in the bulk case, is readily discerned by employing double Airy beams in photonic structures. The proposed method is validated numerically and experimentally by detecting different types of nonlinearities of photonic lattices fabricated in a nonlinear crystal. These findings introduce a promising route for characterizing the nonlinear response of optical structures, thereby broadening the scope of nonlinear measurement and is expected to be extended into other periodic photonic structures.

Shaking Table Test Studies on Adaptive-Passive Variable Frequency Gas-Spring DVA for Structural Seismic Response Mitigation

The control performance of a passive dynamic vibration absorber (DVA) is known to be sensitive to its frequency deviation. This study upgrades the conventional device and proposes an adaptive-passive variable frequency gas-spring DVA (APVF-GSDVA) for controlling the structural seismic response, while an adaptive control algorithm is developed that requires only a single input signal. The DVA’s vibration frequency is precisely modulated by adjusting the gas pressure in the gas-spring, aligning it with the inherent frequency of the multi-degree-of-freedom (MDOF) structure. The working principle and control algorithm of the APVF system is introduced and derived in detail, the corresponding gas-spring DVA and implementation are designed, and the configuration of the entire control system is realized. An adaptive variable frequency test scheme is designed and the frequency retuning function of the prototype APVF-GSDVA device installed on an MDOF structure is experimentally validated. The seismic response control effectiveness of the retuned DVA is demonstrated by comparing the detuned DVA, highlighting the necessity of implementing adaptive frequency adjustment of the gas-spring DVA. Experimental findings demonstrate that APVF-GSDVA accurately identifies the inherent frequency of the MDOF structure in ambient excitation, it then adjusts the pressure of the gas-spring according to the frequency-pressure relationship, optimally retuning the DVA. A retuned GSDVA can effectively suppress the structural seismic responses, compared to a detuned DVA, its control effectiveness on peak and RMS responses can be improved by a maximum of nearly 13.5% and 53.3% at a frequency deviation of 10%. Furthermore, results from two “detuning-retuning” test paths with distinct seismic excitations indicate that the retuned DVA exhibits superior control effectiveness, underscoring the significance of the adaptive frequency adjustment function in passive DVAs.

Symbolic Regression: An Alternative Method to Model the Optical Response of Photonic Biological and Bio-inspired Structures

Symbolic Regression: An Alternative Method to Model the Optical Response of Photonic Biological and Bio-inspired Structures

Non‐linear time history analyses of a rigid block isolated with unbonded fiber‐reinforced elastomeric isolators (UFREIs): A comparison between 3D finite element and phenomenological models

AbstractNumerical modeling represents a pivotal tool in the seismic analysis and design of structural systems, enabling the detailed prediction and examination of structural responses under seismic loading. This research conducts a comparative analysis of two numerical modeling approaches aimed at simulating the seismic response of unbonded fiber‐reinforced elastomeric isolators (UFREIs). The research focuses on a finite element (FE) model developed using Abaqus and a developed phenomenological model implemented in OpenSees, outlining the development and calibration processes for each. The FE model is developed based on simple rubber material testing data, while the phenomenological model is calibrated using experimental results from cyclic shear tests conducted on the UFREI device and the FE model. The primary objective of this study is to assess the effectiveness of these modeling approaches in predicting UFREI behavior under seismic conditions. This evaluation entails comparing model predictions with experimental data obtained from unidirectional shake table tests performed on a rigid block isolated by two UFREIs. This paper highlights the distinct advantages and limitations of each model in simulating UFREI dynamic responses during seismic events. Furthermore, it provides insights into the modeling techniques and discusses the computational demands and data requirements of each model, thereby aiding in their application to various aspects of seismic analysis and design.

Three-Dimensional Numerical Analysis of Seismic Response of Steel Frame–Core Wall Structure with Basement Considering Soil–Structure Interaction Effects

In recent years, numerous studies highlighted the crucial role of the soil–structure interaction (SSI) in the seismic performance of basement structures. However, there remains a limited understanding of how this interaction affects buildings with basement structures under varying site conditions. Based on the three-dimensional (3D) numerical analysis method, the influence of the SSI on the seismic response of high-rise steel frame–core wall (SFCW) structures situated on shallow-box foundations were investigated in this study. To further investigate the effects of the SSI and site conditions, three types of soil profiles—soft, medium, and hard—were considered, along with a fixed-foundation model. The results were compared in terms of the maximum lateral displacement, inter-story drift ratio (IDR), acceleration amplification coefficient, and tensile damage for the SFCW structure under different site conditions, with both fixed-base and shallow-box foundation configurations. The findings highlight that the site conditions significantly affected the seismic performance of the SFCW structure, particularly in the soft soil, which increased the lateral deflection and inter-story drift. Moreover, compared with non-pulse-like ground motion, pulse-like ground motion resulted in a higher acceleration amplification coefficient and greater structural response in the SFCW structure. The RC core wall–basement slab junction was a critical region of stress concentration that exhibited a high sensitivity to the site conditions. Additionally, the maximum IDRs showed a more significant variation at incidence angles between 20 and 30 degrees, with a more pronounced effect at a seismic input intensity of 0.3 g than at 0.2 g.

Fish–Seascape Associations Within an Offshore Protected Area in the Arabian Gulf

ABSTRACTCoral reef ecosystems support high fish biodiversity through ecological interactions with structural complexity across multiple spatial scales including coral colony architecture and the surrounding seascape structure. In an era where the complexity of coral reef ecosystems is being diminished, understanding the importance of structural characteristics beyond single focal patches has the potential to better inform actions for protecting, restoring or creating habitat for reef‐associated species. A seascape ecology approach was applied to explore the associations between multiple scales of seascape structure and fish assemblage response variables within a small (49.6 km2) offshore no‐take MPA, Sir Bu Nair Island Protected Area, in Sharjah, United Arab Emirates. Fish–seascape associations were modelled with single regression trees. Both in situ and remote sensing–derived variables produced the best models with highest contributions from coral cover, amount of hard‐bottom habitat type and structural complexity of the seafloor terrain. Fish species richness was significantly higher where coral cover exceeded 35%. The hard‐bottom areas with coral supported diverse assemblages dominated by carnivorous and omnivorous fishes. The Sir Bu Nair Island Protected Area provides a critical refuge for threatened and regionally overexploited species including those with low resilience to fishing. The ecological success of this protected area is key to safeguarding regional marine biodiversity and recovering fish populations to enhance food security.

Dynamic analysis of a pedestrian bridge using monitoring and computational techniques

Soil-structure interaction (SSI) represents an important parameter when analyzing the dynamic behavior of bridges, considering the combined effects of soil, foundation, and structure to ensure an adequate structural representation. This paper applied a computational modeling strategy associated with soil-structure interaction methodology to represent the dynamic behavior of a timber-concrete pedestrian bridge of the Polytechnic School of the University of São Paulo. The computational models were validated and calibrated using monitoring results from an extensive structural health monitoring campaign. The bridge monitoring program was characterized using embedded sensors and remote monitoring technology: ground-based radar interferometry and video motion amplification. The instrumentation results were compared to establish the capabilities and advantages of this novel remote monitoring technique. The experimental results obtained from free and forced vibrations in the asset served as a basis for validating the developed computational model and allowed the evaluation of the asset behavior in service for different loading conditions. This paper emphasizes the importance of considering an SSI approach to represent the bridge dynamic behavior more accurately, enabling the use of more reliable numerical models to assess the bridge structural responses throughout its life-cycle.

H2 Optimization of a New Type of Tuned Lever Inerter-like Mass Damper (TLIMD) for Attenuating Structure Vibrations

The lever or the lever-type mechanism can achieve an inertia amplification effect by appropriately calibrating its structural configuration, and it is also proven to be one of the most cost-effective solution for the inerter realization compared with other mechanical devices. Benefitting from this property, the present paper adopted a new type of tuned lever inerter-like mass damper (TLIMD) for attenuating stochastic load-induced structure dynamic responses. A set of closed-form formulae for the TLIMD optimal parameters are developed by the use of H2 norm optimization criterion, wherein the structure’s inherent damping is explicitly accounted for. It is theoretically demonstrated that the TLIMD optimal parameters are mainly dominated by three critical parameters, i.e., the damper mass ratio, the lever length ratio (known as the inertia amplification ratio) and also the host structural damping. The proposed formulae for the TLIMD optimization are validated through the seismic analysis, where two classic inerter-based dampers (i.e., the tuned mass damper inerter (TMDI) and the tuned inerter damper (TID)) optimized by the numerical technique are included in the discussion. It is found that the TLIMD has a superior advantage in reducing the structure responses and also exhibits stronger robustness for the detuning condition than the classic inerter-based dampers. Furthermore, the increase in the damper mass ratio and the lever length ratio can be beneficial for enhancing its performance.

Deep learning-based ground motion inversion through recursive structural acceleration response using DRA-LSTM Net

Known ground motion time history is crucial for the precise numerical analysis of structural response and evaluation of its safety. This study introduces the Deep Recursive Attentive Long Short-Term Memory Network (DRA-LSTM Net), a framework designed for the inversion of ground motion (GM) from recorded structural response (SR) during an earthquake. By integrating an attention mechanism in network along with a strategic recursive approach for dataset management, the DRA-LSTM Net achieves high precision in GM inversion. The method incorporates a novel pre-processed matrix format to capture unique recursive behaviour patterns in GM data, enhancing the model’s training, validation efficiency, and prediction accuracy on unseen test datasets. Case studies on single-degree-of-freedom (SDOF) and multi-degree-of-freedom (MDOF) structures highlight the method’s potential for real-time and high-precision GM inversion. Additionally, transfer learning was implemented to fine-tune the pre-trained model with real-world sensor data and structural responses from different floors, demonstrating the model’s adaptability and ability to retain high prediction accuracy across diverse datasets. This approach is particularly useful for regions with limited seismic instrumentation but equipped with structural response sensors.

Mechanical characterization of a 3D printed lattice core sandwich structure

AbstractSandwich structures have garnered interest as versatile structures for applications in advanced engineering structures. To fabricate sandwich structures, plastics have replaced conventional materials; however, most of these plastics remain in the environment beyond their functional lifespan. This study describes the fabrication of sustainable hybrid sandwich structures with 3D printed poly‐lactic acid (PLA) cores and self‐reinforced polyethylene terephthalate (srPET) face sheets. The mechanical responses of the hybrid sandwich structures with three types of lattice cores, S‐90, S‐45, and S‐V, were compared with those of the parent material sandwich structures after performing bending and impact tests. The face sheet in the hybrid sandwich structure transferred the load to the core without failure. The hybrid sandwich structure containing the S‐90 core exhibited a higher fracture strength (52.4 MPa) and tangent modulus of elasticity (2860 MPa) than those of the other structures. S‐V exhibited the highest fracture strains of 3.3% and 5% for parent material and hybrid sandwich structures, respectively. This study highlights the sandwich structures with excellent mechanical properties for structural applications.Highlights Novel sandwich structures with 3D printed PLA cores are fabricated. Three‐point bending and low‐velocity impact tests are performed. Failure occurred in the core, but the Sr‐PET face sheets did not deform. Hybrid sandwich structures significantly improve mechanical performance.

Probabilistic seismic demand analysis for bridges based on earthquake scenarios

The current probabilistic seismic demand analysis of structures predominantly considers the correlation between the ground motion intensity measure (IM) and structural seismic demand, but fails to effectively capture regional source characteristics. It is essential to integrate earthquake engineering with seismic response of structures using source parameters to quantify regional ground motion uncertainties and determine appropriate IMs. This study presented a probabilistic seismic demand analysis method for structures based on earthquake scenarios, characterized by 1) utilizing the stochastic finite-fault method to simulate ground motions at a specific site instead of employing multiple seismic waves from different source areas, and 2) incorporating the correlation between IMs and the key indicator of source parameters, stress drop, into the probabilistic seismic demand analysis. Taking a continuous girder bridge as an example, the performance of the stress drop and 14 individual IMs in predicting the longitudinal seismic demand and reflecting source characteristics was evaluated. The results revealed that it was difficult to establish a reliable relationship between the stress drop and structural seismic demand. Owing to the complexities of ground motion and structural parameters, the individual IMs were challenging to effectively capture their characteristics simultaneously. Therefore, composite IMs have been proposed to cover the characteristics of both the source and seismic demand. The optimal solutions were derived using a multi-objective genetic algorithm, which exhibited desirable capabilities in both aspects, providing a comprehensive guide for the seismic performance assessment of regional transportation networks.

Multi-objective optimal design of Tuned Mass Damper Inerter for base isolated structures

The BIS-TMDI is a hybrid control strategy that significantly reduces the seismic response of structures compared to conventional BIS through proper tuning, albeit with the trade-off of increased control forces exerted by the TMDI on the host building structure. However, these potentially significant forces are generally not considered in current TMDI tuning approaches. In this paper, a multi-objective optimization design method is herein developed to determine the compromise between the competing objectives of suppressing earthquake-induced vibrations in buildings and avoiding the generation of excessive control forces of TMDI. The study shows that under non-stationary excitations, the average control force of the TMDI system can be reduced by 16% compared to single optimization constraint, with a maximum reduction of up to 25%. Finally, the optimization design methods of this paper are applied to an 8-story frame as a validation case.