Ground Acceleration Time Histories Research Articles

EKSPLORASI REKAMAN GEMPA-GEMPA DI INDONESIA DAN KARAKTERISTIK DIRI YANG DINYATAKAN DALAM ACCELERATION BASED SEISMIC INTENSITY MEASURES (SIMs)

Indonesia is a prone country to earthquake hazards. This situation is indicated by the number of earthquakes ranging from small to significant events. However, digital earthquake ground motion data are not available, making it difficult for further research. This paper aims to explore recordings of earthquakes that occurred in Indonesia, which are then presented in digital data and used to identify their damage potential in the form of Seismic Intensity Measures (SIMs). After being traced, it turned out that there were only six earthquakes whose ground acceleration time history was found through the paPers published by researchers. The earthquakes were the Mw 6.2 Yogyakarta (2006), the Mw7.6 Padang (2009), the Mw6.1 Bener Meriah Central Aceh (2013), and the Mw6.5 Pidie Jaya Aceh (2016), the Mw7.5 Palu (2018) and the Mw6.1 Malang (2021) earthquakes. The manual digitization and processing to obtain ground acceleration data every 0.01s time step are required. Eight aspects based on acceleration and two aspects based on response spectrum have been used as parameters for Seismic Intensity Measures SIMs. The exploration results show that the source of the earthquake in Sumatra is still relatively shallow, getting more profound in the Java and Nusa Tenggara subduction. The P.G.A. of the Yogyakarta earthquake is 0.272g with a total duration of more than 50 seconds. In general, according to SNI 1726, 2019, the spectrum has been able to cover all ground acceleration time histories. The Yogyakarta earthquake has the highest Earthquake Power, Arias Intensity, and Potential Destructiveness values, namely PE = 0.255 and IA = 2.201, and P.D. = 0.166.

A Novel Approach to the Integration for Generating Consistent Ground Acceleration, Velocity and Displacement Time Histories

The velocity and the displacement time history obtained by directly integrating the acceleration time history will drift unrealistically because of the over-determinacy of the integration constants. Applying baseline corrections to resolve drift disturbs the frequency content and renders the corrected processes mutually inconsistent. In this study, eigenfunctions of sixth-order eigenvalue problem are introduced as basis functions for decomposing recorded ground motion time history. Taking advantage of the eigenfunctions and their first two order of differentiations are drift-free and consistent, the decomposed and reconstructed acceleration, velocity, and displacement time histories can be drift-free and mutually consistent without direct integration and baseline correction. Two earthquake ground motions are presented as examples, which show that the decomposed acceleration, velocity, and displacement time histories are drift-free, mutually consistent, and almost the same as the seed motion. The new approach can replace integral in the generation of velocity and displacement time histories.

A Novel Whale Optimization Algorithm for the Design of Tuned Mass Dampers under Earthquake Excitations

This paper introduces a novel methodology for the optimum design of linear tuned mass dampers (TMDs) to improve the seismic safety of structures through a novel Whale Optimization Algorithm (WOA). The algorithm is aimed to reduce the maximum horizontal peak displacement of the structure, and the root mean square (RMS) response of displacements as well. Furthermore, four additional objective functions, derived from multiple weighted linear combinations of the two previously mentioned parameters, are also studied in order to obtain the most efficient TMD design configuration. The differential evolution method (DEM), whose effectiveness has been previously demonstrated for TMD applications, and an exhaustive search (ES) process, with precision to two decimal positions, are used to compare and validate the results computed through WOA. Then, the proposed methodology is applied to a 32-story case-study derived from an actual building, and multiple ground acceleration time histories are considered to assess its seismic performance in the linear-elastic range. The numerical results show that the proposed methodology based on WOA is effective in finding the optimal TMD design configuration under earthquake loads. Finally, practical design recommendations are provided for TMDs, and the robustness of the optimization is demonstrated.

Seismic fragility analysis using nonlinear autoregressive neural networks with exogenous input

Rapidly growing societal needs in urban areas are increasing the demand for tall buildings with complex structural systems. Many of these buildings are located in areas characterized by high seismicity. Quantifying the seismic resilience of these buildings requires comprehensive fragility assessment that integrates iterative nonlinear dynamic analysis (NDA). Under these circumstances, traditional finite element (FE) analysis may become impractical due to its high computational cost. Soft-computing methods can be applied in the domain of NDA to reduce the computational cost of seismic fragility analysis. This study presents a framework that employs nonlinear autoregressive neural networks with exogenous input (NARX) in fragility analysis of multi-story buildings. The framework uses structural health monitoring data to calibrate a nonlinear FE model. The model is employed to generate the training dataset for NARX neural networks with ground acceleration and displacement time histories as the input and output of the network, respectively. The trained NARX networks are then used to perform incremental dynamic analysis (IDA) for a suite of ground motions. Fragility analysis is next conducted based on the results of the IDA obtained from the trained NARX network. The framework is illustrated on a twelve-story reinforced concrete building located at Oklahoma State University, Stillwater campus.

Effect of Linear Soil Condition on Seismic Inputs

Seismic inputs to structures in terms of risk consistent response spectrum and seismic hazard curves are developed at bedrock level considering ten independent seismic source zone in the vicinity of the Kathmandu valley. The seismic hazard curve is derived by assuming temporal occurrence of earthquakes to follow Poisson model. Response spectrum is developed using an empirical relationship of spectral ordinates with magnitude of earthquakes and epicentral distance. The seismic risk factor is introduced in response spectrum using conditional probabilities. Power spectral density function consistent with response spectrum is derived and ground acceleration time histories are derived from power spectral density function using Monte Carlo technique. To obtain free field hazard curves and ground motion parameters, one dimensional wave propagation analysis is used for two different underlying soil conditions.

Multi-Objective Optimization of Three Different SMA-LRBs for Seismic Protection of a Benchmark Highway Bridge against Real and Synthetic Ground Motions

Many researchers have taken advantage of adding shape memory alloy (SMA) wires to base isolators to control displacements and residual deformations. In the literature, different arrangements of SMA wires wrapped around the rubber bearings can be found, as examples, straight, cross and double-cross arrangements. SMA wires with various configurations and radii lead to the different characteristics of the isolator system and thus various shear hysteresis. Therefore, the aim of this study is to evaluate the performance of these three SMA wire’s configurations in the seismic retrofitting of a benchmark highway bridge by implementing them in the bridge’s existing lead rubber bearings (LRB). This system is referred to as SMA-LRB isolator. Firstly, because of the crucial influence of the wire’s radius, this parameter is determined using a multi-objective optimization algorithm (non-dominated sorting genetic algorithm (NSGA)-II). This algorithm simultaneously minimizes the deck acceleration and mid-span displacement. Secondly, the optimized SMA-LRBs are implemented in the highway bridge and nonlinear dynamic analysis is conducted. For the nonlinear response history analysis, two strong ground motion records are selected from the PEER database, by studying the site’s conditions. In addition, ten synthetic ground acceleration time histories are generated. The result illustrates that the double-cross SMA-LRB reduces the maximum and residual displacements more than two other devices; however, it causes the largest base shear force and deck acceleration. Besides, the cross-configuration results in the least displacement reduction and has the least shear force and acceleration. To find SMA-LRB with the best overall performance, a multi-objective decision-making method is utilized and the straight SMA-LRB is recognized as the most effective isolator.

Shaking table tests on V-shaped RC columns at the weak ground storey of a building

This paper presents experimental and numerical investigations of the seismic behaviour of V-shaped reinforced-concrete (RC) columns at the weak ground storey of a building. Two half-scaled RC columns were tested to failure by a simulated ground acceleration time history using a shaking table. The test setup was designed to simulate the sliding mechanism of the column specimens, termed the double-curvature mechanism, which is expected to occur in a soft-storey building. The seismic responses of the specimens were evaluated and compared with each other in terms of general performance, hysteresis response and failure modes. Thereafter, a fibre-element model, verified by the test data, was used to conduct a parametric study on the effects of axial load ratio and longitudinal reinforcement arrangement on the seismic performance of irregularly shaped columns.

Seismic response of cable-stayed bridge subjected to single-support excitation on various soil condition

For cable-stayed bridge, pylon and girder are one of the most important factors in the design process. Because of the length this structure, it needs to consider the type of the soil because different soil type can be resulting a different earthquake loads. In this study, the behavior of superstructure was investigated using time history analysis subjected to excitation uniformly on the pylon and girder. The test model was a cable-stayed bridge which classified as a long-span bridge. For obtaining the effects of soil type condition, different response spectrums are considered for three soil types: firm, medium, and soft soil. The response spectrums were thus converted to become ground acceleration time history and displacement time history. The displacement was then applied longitudinally and transversally to the supports of the structure to determine the behavior of the bridge. The result shows that the maximum displacement on the pylon and girder due to longitudinal load was at the top of the pylon and in the middle of the main span. As for the transverse earthquake load, the maximum displacement was in the middle area of the pylon and the middle of the main span. The results also defines that the displacement caused by firm soil is smaller than medium soil and soft soil.

Seismic Response of Reactive Powder Concrete Columns Confined with FRP

Abstract In this research, which is based on the finite element method, the behavior of reactive powder concrete (RPC) columns confined with fiber-reinforced polymer (FRP) under seismic excitation is investigated. The governing theory in the numerical simulation is based on the fiber finite element method. The adequacy of the fiber model in predicting the response of FRP-confined RPC columns is validated through comparisons with the available experimental results. To study the seismic behavior of FRP-confined RPC columns, the fiber model presented was subjected to different earthquakes. In this regard, four ground acceleration time histories with different peak accelerations were applied to investigate the response of FRP-confined RPC columns. The results show that reactive powder concrete columns confined with FRP exhibit an acceptable seismic performance. The investigation also confirms that RPC-confined columns show a high degree of ductility. Additionally, the load capacity (maximum lateral load) is increased, and the concrete’s compressive strength is increased.

Pinching in Steel Rack Joints: Numerical Modelling and Effects on Structural Response

The structural behaviour of beam-to-column joints plays a key role in the seismic response of frame structures. Regarding to steel storage pallet racks, experimental tests have highlighted that the hysteresis loop of their joints is characterized by the pinching, with the consequence of a reduction of the dissipated hysteretic energy and load carrying capacity. In this paper the authors propose a simplified numerical pinching model capable to simulate the mechanical response of beam-to-column joints under cyclic loads. To develop and check this model, several comparisons are performed with both literature data and experimental results of laboratory tests. The proposed model is characterised by three links placed in parallel: two “composed links” describe the non-linear bending moment-rotation curve of the joint, and a linear elastic link transfers the axial and shear force from the beam to the column. The model is appropriate for predicting the down-aisle seismic response of rack systems and it can be easily implemented in commercial software packages, commonly used for non-linear seismic vulnerability analyses. Moreover, features of the model can be estimated from a few structural data and it does not require to perform expensive cyclic experimental tests. For a deeper understanding of the effects of pinching in the seismic response and to highlight the potentiality of the proposed model a case-study example is also considered. The case-study concerns a rack system, whose beam-to-column joints are modelled using two numerical approaches which differ in the deterioration of the rotational stiffness of joints. Non-linear dynamic analyses, with simulated ground acceleration time-histories, have been carried.

A Comparative Study between Pseudo-static and Dynamic Analyses on Rock Wedge Stability of an Arch Dam

In this study, the abutment stability of arch dams for two cases of pseudo-static and dynamic methods were compared based on limit state equilibrium method. For the pseudo-static approach, unit accelerations were applied to the model in three directions for calculating thrust forces. For dynamic analysis, three components of ground acceleration time histories of Kobe earthquake, 1979 were applied to the finite element model of dam-foundation-reservoir, and the thrust forces were obtained. The effect of reduction factors in pseudo-static analysis is investigated in order to obtain the reduction factor that corresponds to wedge movement in dynamic analysis. For this purpose, the reduction factors have been increased from 0.5 to 1. The obtained results indicate that pseudo-static results are more conservative than the dynamic analysis method for small reduction factors and the reduction factor plays a key role on the abutment stability analysis.

Bayesian optimal estimation for output-only nonlinear system and damage identification of civil structures

This paper presents a new framework for output-only nonlinear system and damage identification of civil structures. This framework is based on nonlinear finite element (FE) model updating in the time-domain, using only the sparsely measured structural response to unmeasured or partially measured earthquake excitation. The proposed framework provides a computationally feasible approach for structural health monitoring and damage identification of civil structures when accurate measurement of the input seismic excitations is challenging (e.g., buildings with significant foundation rocking and bridges with piers in deep water) or the measured seismic excitations are erroneous and/or distorted by significant measurement error (e.g., malfunctioning sensors). Grounded on Bayesian inference, the proposed framework estimates the unknown FE model parameters and the ground acceleration time histories simultaneously, using the sparse measured dynamic response of the structure. Two approaches are presented in this study to solve the joint structural system parameter and input identification problem: (a) a sequential maximum likelihood estimation approach, which reduces to a sequential nonlinear constrained optimization method, and (b) a sequential maximum a posteriori estimation approach, which reduces to a sequential iterative extended Kalman filtering method. Both approaches require the computation of FE response sensitivities with respect to the unknown FE model parameters and the values of base acceleration at each time step. The FE response sensitivities are computed efficiently using the direct differentiation method. The two proposed approaches are validated using the seismic response of a 5-story reinforced concrete building structure, numerically simulated using a state-of-the-art mechanics-based nonlinear structural FE modeling technique. The simulated absolute acceleration response time histories of 3 floors and the relative (to the base) roof displacement response time histories of the building to a bidirectional horizontal seismic excitation are polluted with artificial measurement noise. The noisy responses of the structure are then used to estimate the unknown FE model parameters characterizing the nonlinear material constitutive laws of the concrete and reinforcing steel and the (assumed) unknown time history of the ground acceleration in the longitudinal direction of the building. The same nonlinear FE model of the structure is used to simulate the structural response and to estimate the dynamic input and system parameters. Thus, modeling uncertainty is not considered in this paper. Although the validation study demonstrates the estimation accuracy of both approaches, the sequential maximum a posteriori estimation approach is shown to be significantly more efficient computationally than the sequential maximum likelihood estimation approach.

The ground motion simulation of Kangding Mw6.0,2014 by the stochastic finite-fault model

The November 22, 2014, Kangding strike-slip earthquake (Mw 6.0) occurred on the Southern Section of the Xianshuihe Fault Zone. Its epicenter was at 101.69°E, 30.26°N, source mechanism strikes N33°E, dips 82°, and slipped at an angle of –9°. In this work, we simulated ground motions by the stochastic finite-fault model(SFFM), including peak ground acceleration, peak velocity, and acceleration time-histories caused by this earthquake.

Performance-based seismic assessment of vulnerability of dam using time history analysis

The current performance-based seismic assessment procedure can be computationally intensive as it requires many time history analyses (THA) each requiring time intensive post-processing of results. Time history analysis is a part of structural analysis and is the calculation of the response of a structure to any earthquake. It is one of the main processes of structural design in regions where earthquakes are prevalent. The objective of this study is to evaluate the seismic performance of embankment dam located on the Oued RHISS in the Province of AL HOCEIMA using the THA method. To monitor structural behavior, the seismic vulnerability of structure is evaluated under real earthquake records with considering the soil-structure-fluide interaction. In this study, a simple assistant program is developed for implementing earthquake analyses of structure with ANSYS, ground acceleration–time history data are used for seismic analysis and dynamic numerical simulations were conducted to study and identify the total response of the soil-structure system.

Predictive model for site specific simulation of ground motions based on earthquake scenarios

SummaryA predictive stochastic model is developed based on regression relations that inputs a given earthquake scenario description and outputs seismic ground acceleration time histories at a site of interest. A bimodal parametric non‐stationary Kanai‐Tajimi (K‐T) ground motion model lies at the core of the proposed predictive model. The functional forms that describe the temporal evolution of the K‐T model parameters can effectively represent strong non‐stationarities of the ground motion. Fully non‐stationary ground motion time histories can be generated through the powerful Spectral Representation Method. A Californian subset of the available NGA‐West2 database is used to develop and calibrate the predictive model. Samples of the model parameters are obtained by fitting the K‐T model to the database records, and the resulting marginal distributions of the model parameters are efficiently described by standard probability models. The samples are translated to the standard normal space and linear random‐effect regression models are established relating the transformed normal parameters to the commonly used earthquake scenario defining predictors: moment magnitude Mw, closest‐to‐site distance Rrup, and average shear‐wave velocity at a site of interest. The random‐effect terms in the developed regression models can effectively model the correlation among ground motions of the same earthquake event, in parallel to taking into account the location‐dependent effects of each site. For validation purposes, simulated acceleration time histories based on the proposed predictive model are compared with recorded ground motions. In addition, the median and median plus/minus one standard deviation elastic response spectra of synthetic ground motions, pertaining to a variety of different earthquake scenarios, are compared to the associated response spectra computed by the NGA‐West2 ground motion prediction equations and found to be in excellent agreement.

Simulation of Near-Fault High-Frequency Ground Motions from the Representation Theorem

“What is the maximum possible ground motion near an earthquake fault?” is an outstanding question of practical significance in earthquake seismology. In establishing a possible theoretical cap on extreme ground motions, the representation integral of elasticity, providing an exact, within limits of applicability, solution for fault radiation at any frequency, is an under-utilized tool. The application of a numerical procedure leading to synthetic ground displacement, velocity, and acceleration time histories to modeling of the record at the Lucerne Valley hard-rock station, uniquely located at 1.1 km from the rupture of the M w 7.2 Landers, California event, using a seismologically constrained temporal form of slip on the fault, reveals that the shape of the displacement waveform can be modeled closely, given the simplicity of the theoretical model. High precision in the double integration, as well as carefully designed smoothing and filtering, are necessary to suppress the numerical noise in the high-frequency (velocity and acceleration) synthetic motions. The precision of the integration of at least eight decimal digits ensures the numerical error in the displacement waveforms generally much lower than 0.005% and reduces the error in the peak velocities and accelerations to the levels acceptable to make the representation theorem a reliable tool in the practical evaluation of the magnitude of maximum possible ground motions in a wide-frequency range of engineering interest.

Experimental and numerical study of the response of cylindrical steel tanks under seismic excitation

To improve the structural seismic response of liquid storage tanks, in the last 50 years, many researchers have developed different mathematical models, ranging from those based on discrete elements such as simplified two-mass models to those involving fluid–structure interactions by complex formulations. To provide a broad overview on the scope and accuracy of different numerical linear models, in this paper, a comparative study based on the dynamic response assessment of cylindrical ground-supported containers under seismic excitation is conducted. The dynamic response in terms of liquid sloshing height, base shear force and overturning moment is analysed by means of: (a) a simplified mechanical model in which the behaviour of the liquid is represented by a discrete mass-spring system; (b) a complex model based on a Lagrangian fluid finite element approximation and (c) an experimental scaled model whose measured response is considered as benchmark. To obtain robust estimators of the structural response, three different types of cylindrical tanks, including broad and slender tanks, subjected to real ground acceleration time-histories are studied. The results indicate that the finite element model gives good approximation for all response parameters and the simplified mechanical model underestimate the sloshing height and overestimate base shear force and overturning moment.

A Multi-step approach to generate response-spectrum-compatible artificial earthquake accelerograms

Time history records are essential for nonlinear dynamic analysis to determine the response of structures. Considering lack of enough earthquake records, generation of artificial earthquake records and spectrum-matched records are the best method in this regard. This study is motivated by real life applications of designing new structures or evaluating the performance of current ones in Afghanistan where two structures are to be designed and built to withstand earthquakes. In this paper, design response spectrum and time history records are generated for two sites located within the city of Kabul, Afghanistan. The Probabilistic Seismic Hazard Assessment (PSHA) results are employed initially to produce the required parameters and data. Then, the generalized nonstationary Kanai-Tajimi model is applied to simulate the ground acceleration time history using the identified characteristics of the site from preliminary ARMA (Auto Regressive Moving Average) analysis and the site-specific analysis. The response spectrum is developed and iteratively compared to the ARMA model and the site-specific spectrum until a satisfactory match is achieved. Finally, the time domain description of the spectrum-compatible artificial earthquake record is developed exploiting inverse FFT of the design response spectrum. The total errors in spectral matching generated accelerograms are compared to results from a commercially available software. Results demonstrated the effectiveness and robustness of the adapted approach.

A Nonlinear Model Inversion Method for Joint System Parameter, Noise, and Input Identification of Civil Structures

This paper presents a framework for nonlinear system identification of civil structures using sparsely measured dynamic output response of the structure. Using a sequential maximum likelihood estimation (MLE) approach, the unknown FE model parameters, the measurement noise variances, and the input ground acceleration time histories are estimated jointly. This approach requires the computation of FE response sensitivities with respect to the unknown FE model parameters (i.e., FE parameter sensitivities) as well as the FE response sensitivities with respect to the values of the input ground acceleration at every time step (i.e., FE input sensitivities). The FE parameter and input sensitivities are computed using the direct differentiation method (DDM). The presented output-only nonlinear FE model updating method is validated using the numerically simulated seismic response of a realistic three-dimensional five-story reinforced concrete building structure. The simulated building responses to a horizontal bi-directional seismic excitation is contaminated with artificial measurement noise and used to estimate the unknown FE model parameters characterizing the nonlinear material constitutive laws of the reinforced concrete, as well as the root mean square of the measurement noise at each measurement channel, and the full time history of the seismic base acceleration. The method presented in this paper provides a powerful framework for structural system and damage identification of civil structures, when the input excitations are not measured, are partially measured, or the measured input excitations are erroneous.

Seismic behavior of RC structures with absence of floor slab constraints and large mass turbine as a non-conventional TMD: a case study

This paper presents a case study on the influence of absence of floor slab constraints and large mass turbine as a non-conventional tuned mass damper (TMD) on the seismic behavior of the structure and members. The investigated structural system is a reinforced concrete (RC) shear wall-frame power plant structure with large slab openings and a large mass turbine. In RC structures, the existence of floor slabs can usually provide strong constraints on beams so as to greatly increase their bearing capacity. However, due to some special functional demands, large area of slabs may have to be removed so that some floor beams will lose the constraints provided by slabs. In such cases, beams could be subjected to complex internal forces and develop unexpected failure modes under earthquake actions. Nonlinear time history analyses are conducted by using the self-developed program COMPONA-MARC Version 1.0. The numerical model employs fiber beam-column elements with distributed plasticity approach which can elaborately simulate the complex seismic behavior of structural members without slab constraints including the significant transverse vibration damage mechanism. For the seismic effectiveness of the turbine as a TMD with large mass ratio, the optimized parameters are discussed and verified by extensive numerical examples under a wide selection of ground acceleration time histories. The acceleration responses of the turbine are analyzed and found to satisfy the corresponding requirements. The dynamic interaction between the structure and turbine is evaluated and the effects of mass ratio and multiple supporting springs on the dynamic response of the turbine are investigated. It is found that the acceleration response of the turbine modeled with multiple supporting springs is evidently larger than that modeled with a single degree-of-freedom system, and the floor response spectrum decreases significantly with the increase of the mass ratio.