scholarly journals Study on Quasi-Static Loading Protocols considering the Action Characteristics of Long-Period Ground Motions

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Ke Yang ◽  
Bo Wang ◽  
Jiawei Zhang ◽  
Zhe Li ◽  
Boquan Liu
Keyword(s):  
Seismic Performance ◽  
Static Loading ◽  
Ground Motions ◽  
Low Frequency ◽  
Time History ◽  
Experimental Investigations ◽  
Structural Components ◽  
Cycle Number ◽  
Long Period ◽  
Nonlinear Time History

Due to abundant low-frequency components of long-period ground motions (LPGMs), long-period structures are susceptible to severe damage. The corresponding time-history displacement responses have significant “large-displacement” and “long-duration” characteristics. These action characteristics essentially reflect the different loading paths imposed on structures of LPGMs from ordinary ground motions (OGMs). Hence, revealing the influence mechanism of the action characteristics on the seismic performance of structural components is the key to investigating the influence of LPGMs on the whole structure. This paper presents a kind of quasi-static loading protocol considering the action characteristics of LPGMs. Firstly, nonlinear time-history analyses on structural systems subjected to 50 selected representative LPGMs were conducted. Inelastic cycles and corresponding amplitudes of time-history displacement responses under LPGMs were statistically analyzed through the rainflow method. Then, considering two of the most significant factors, structural period and target ductility, a prediction model of cycle number and cycle amplitude was obtained by regression. On this basis, the quasi-static loading protocol considering the action characteristics of LPGMs was developed. Proposed protocols can be directly applied to experimental investigations on the seismic performance for structural components under LPGMs.

scholarly journals Evaluation of seismic performance measures for MDOF RC structures subjected to simulated and real ground motions

2020 ◽  
Vol 323 ◽  
pp. 02003
Author(s):  
Shaghayegh Karimzadeh ◽  
Aysegul Askan ◽  
Ahmet Yakut
Keyword(s):  
Ground Motion ◽  
Seismic Performance ◽  
Performance Measures ◽  
Ground Motions ◽  
Time History ◽  
Motion Simulation ◽  
Ground Motion Simulation ◽  
Nonlinear Time History Analyses ◽  
Nonlinear Time History ◽  
Simulated Ground Motions

Nonlinear time history analyses of structures require full time series of ground motion records. For regions with sparse seismic networks or potential large earthquakes, ground motion simulation has gained more attention in recent years. Simulated records are required to be generated using regional input dataset and then verified against existing recorded ground motions of past events. To use simulated ground motions in engineering applications, estimation of reliable seismic demand parameters is essential. In this study, the real and simulated records of the 2009 L’Aquila, Italy earthquake with (Mw=6.3) are investigated for their use in engineering practice. In the first step, misfits are evaluated for alternative seismological measures (peak values, duration and frequency as well as energy content of the time histories). Next, varying multi-degree-of-freedom reinforced concrete structures with different number of stories are selected. Numerical models of the structures are performed in the OpenSees platform. Seismic performance measures in terms of inter-story drift ratio for the selected structures are assessed through nonlinear time history analyses for both the real and simulated ground motions. Then, the misfits are estimated in terms of structural demand parameters. Results reveal a good fit between the seismological and engineering demand misfits for the selected ground motion simulation approaches.

Seismic response analysis of steel–concrete hybrid wind turbine tower

2021 ◽  
pp. 107754632110075
Author(s):  
Junling Chen ◽  
Jinwei Li ◽  
Dawei Wang ◽  
Youquan Feng
Keyword(s):  
Wind Turbine ◽  
Response Spectrum ◽  
Ground Motions ◽  
Time History ◽  
Seismic Action ◽  
Response Spectrum Method ◽  
Spectrum Method ◽  
Wind Turbine Tower ◽  
Ground Types ◽  
Nonlinear Time History

The steel–concrete hybrid wind turbine tower is characterized by the concrete tubular segment at the lower part and the traditional steel tubular segment at the upper part. Because of the great change of mass and stiffness along the height of the tower at the connection of steel segment and concrete segment, its dynamic responses under seismic ground motions are significantly different from those of the traditional steel tubular wind turbine tower. Two detailed finite element models of a full steel tubular tower and a steel–concrete hybrid tower for 2.0 MW wind turbine built in the same wind farm are, respectively, developed by using the finite element software ABAQUS. The response spectrum method is applied to analyze the seismic action effects of these two towers under three different ground types. Three groups of ground motions corresponding to three ground types are used to analyze the dynamic response of the steel–concrete hybrid tower by the nonlinear time history method. The numerical results show that the seismic action effect by the response spectrum method is lower than those by the nonlinear time history method. And then it can be concluded that the response spectrum method is not suitable for calculating the seismic action effects of the steel–concrete hybrid tower directly and the time history analyses should be a necessary supplement for its seismic design. The first three modes have obvious contributions on the dynamic response of the steel–concrete hybrid tower.

A Seismic Effective Method for Double-Layer Reticulated Shell Using Buckling-Restrained Braces

2010 ◽  
Vol 163-167 ◽  
pp. 2852-2856
Author(s):  
Chang Wu ◽  
Xiu Li Wang
Keyword(s):  
Double Layer ◽  
Seismic Performance ◽  
Linear Time ◽  
Ground Motions ◽  
Equations Of Motion ◽  
Time History ◽  
Original Structure ◽  
Loading Test ◽  
Strong Earthquakes ◽  
Buckling Restrained Braces

In this study a kind of buckling-restrained braces (BRBs) as energy dissipation dampers is attempted for seismic performance of large span double-layer reticulated shell and the effectiveness of BRBs to protect structures against strong earthquakes is numerically studied. The hysteretic curve of such members is obtained through the simulation of the cyclic-loading test, and the equations of motion of the system under earthquake excitations are established. BRBs are then placed at certain locations on the example reticulated shell to replace some normal members, and the damping effect of the two installation schemes of BRBs is investigated by non-linear time-history analyses under various ground motions representing major earthquake events. Compared with the seismic behavior of the original structure without BRBs, satisfactory seismic performance is seen in the upgraded models, which clarifies the BRBs can reduce the vibration response of spatial reticulated structure effectively and the new system has wide space to develop double layer reticulated shell.

scholarly journals Influence of Optimal Intensity Measures Selection in Engineering Demand Parameter of Fixed Jacket Offshore Platform

2021 ◽  
Vol 11 (22) ◽  
pp. 10745
Author(s):  
Sajib Sarker ◽  
Dookie Kim ◽  
Md Samdani Azad ◽  
Chana Sinsabvarodom ◽  
Seongoh Guk
Keyword(s):  
Seismic Performance ◽  
Oil And Gas ◽  
Time History ◽  
Coefficient Of Determination ◽  
Statistical Parameters ◽  
Ground Acceleration ◽  
Jacket Platform ◽  
Intensity Measures ◽  
Optimal Intensity ◽  
Nonlinear Time History

This research identifies the significant optimal intensity measures (IM) for seismic performance assessments of the fixed offshore jacket platforms. A four-legged jacket platform for the oil and gas operation is deployed to investigate the seismic performance. The jacket platform is applied with nonlinearly modeled using finite element (FE) software OpenSees. A total of 80 ground motions and 21 different IMs are incorporated for numerical analyses. Nonlinear time-history analyses are performed to obtain the jacket structure’s engineering demand parameters (EDP): peak acceleration and displacement at the top of the structure. Four important statistical parameters: practicality, efficiency, proficiency, and coefficient of determination, are then calculated to find the significant IMs for seismic performance of the jacket structure. The results show that acceleration-related IMs: effective design acceleration (EDA), A95 parameter, and peak ground acceleration (PGA) are optimal IMs, and the acceleration-related IMs have good agreements with the acceleration-related EDP.

Effect of bidirectional excitation on seismic performance of regular RC frame buildings designed for modern codes

2021 ◽  
pp. 875529302110478
Author(s):  
Payal Gwalani ◽  
Yogendra Singh ◽  
Humberto Varum
Keyword(s):  
Seismic Performance ◽  
Time History ◽  
Nonlinear Time History Analysis ◽  
Inelastic Behavior ◽  
Moment Frame ◽  
Frame Buildings ◽  
Bidirectional Excitation ◽  
Rc Frame Buildings ◽  
Nonlinear Time History ◽  
Hinge Model

The existing practice to estimate seismic performance of a regular building is to carry out nonlinear time history analysis using two-dimensional models subjected to unidirectional excitations, even though the multiple components of ground motion can affect the seismic response, significantly. During seismic shaking, columns are invariably subjected to bending in two orthogonal vertical planes, which leads to a complex interaction of axial force with the biaxial bending moments. This article compares the seismic performance of regular and symmetric RC moment frame buildings for unidirectional and bidirectional ground motions. The buildings are designed and detailed according to the Indian codes, which are at par with the other modern seismic codes. A fiber-hinge model, duly calibrated with the biaxial experimental results, is utilized to simulate the inelastic behavior of columns under bidirectional bending. A comparison of the estimated seismic collapse capacity is presented, illustrating the importance of considering the bidirectional effects. The results from fragility analysis indicate that the failure probabilities of buildings under the bidirectional excitation are significantly higher as compared to those obtained under the unidirectional excitation.

scholarly journals Assessment of Earthquake Destructive Power to Structures Based on Machine Learning Methods

2020 ◽  
Vol 10 (18) ◽  
pp. 6210
Author(s):  
Ruihao Zheng ◽  
Chen Xiong ◽  
Xiangbin Deng ◽  
Qiangsheng Li ◽  
Yi Li
Keyword(s):  
Neural Network ◽  
Machine Learning ◽  
Ground Motions ◽  
Low Frequency ◽  
Time History ◽  
Time History Analysis ◽  
Machine Learning Algorithms ◽  
Learning Networks ◽  
History Analysis ◽  
Deep Layers

This study presents a machine learning-based method for the destructive power assessment of earthquake to structures. First, the analysis procedure of the method is presented, and the backpropagation neural network (BPNN) and convolutional neural network (CNN) are used as the machine learning algorithms. Second, the optimized BPNN architecture is obtained by discussing the influence of a different number of hidden layers and nodes. Third, the CNN architecture is proposed based on several classical deep learning networks. To build the machine learning models, 50,570 time-history analysis results of a structural system subjected to different ground motions are used as training, validation, and test samples. The results of the BPNN indicate that the features extraction method based on the short-time Fourier transform (STFT) can well reflect the frequency-/time-domain characteristics of ground motions. The results of the CNN indicate that the CNN exhibits better accuracy (R2 = 0.8737) compared with that of the BPNN (R2 = 0.6784). Furthermore, the CNN model exhibits remarkable computational efficiency, the prediction of 1000 structures based on the CNN model takes 0.762 s, while 507.81 s are required for the conventional time-history analysis (THA)-based simulation. Feature visualization of different layers of the CNN reveals that the shallow to deep layers of the CNN can extract the high to low-frequency features of ground motions. The proposed method can assist in the fast prediction of engineering demand parameters of large-number structures, which facilitates the damage or loss assessments of regional structures for timely emergency response and disaster relief after earthquake.

scholarly journals The Effect of Long Duration Earthquakes on the Overall Seismic Behavior of Steel Structures Designed According to Eurocode 8 Provisions

Vibration ◽  
2020 ◽  
Vol 3 (4) ◽  
pp. 464-477
Author(s):  
Panagiota Katsimpini ◽  
Foteini Konstandakopoulou ◽  
George A. Papagiannopoulos ◽  
Nikos Pnevmatikos ◽  
George D. Hatzigeorgiou
Keyword(s):  
Seismic Performance ◽  
Time History ◽  
Steel Structures ◽  
Eurocode 8 ◽  
Steel Buildings ◽  
Long Duration ◽  
Base Steel ◽  
Fixed Base ◽  
Permanent Settlement ◽  
Nonlinear Time History

Premature and simultaneous buckling of several steel braces in steel structures due to the prolonged duration of a seismic motion is one of the issues that must be addressed in the next version of Eurocode 8. In an effort to contribute towards the improvement of the seismic design provisions of Eurocode 8, an evaluation of the overall behavior of some steel building-foundation systems under the action of long duration seismic motions is performed herein by means of nonlinear time-history seismic analyses, taking into account soil–structure interaction (SSI) effects. In particular, the maximum seismic response results—in terms of permanent interstorey drifts, overturning moments and base shears of the steel buildings as well as of the permanent settlement and tilting of their foundations—are computed. It is found that the seismic performance of steel buildings when subjected to long duration seismic motions is: (i) acceptable for the two and five-storey fixed base steel buildings and for the two-storey steel buildings with SSI effects included; (ii) unacceptable for the eight-storey fixed base steel buildings and for the five and eight-storey steel buildings with SSI effects included. In all cases of steel buildings with SSI effects included, the seismic performance of the mat foundation, as expressed by the computed values of residual settlement and tilting, is always acceptable.

Strengthening Research in the Longitudinal Frames of Prefabricated Structures with Viscous Dampers

2013 ◽  
Vol 671-674 ◽  
pp. 782-785
Author(s):  
Bin He ◽  
Jin Lai Pang ◽  
Cheng Qing Liu
Keyword(s):  
Seismic Performance ◽  
Pushover Analysis ◽  
Vertical Direction ◽  
Time History ◽  
Nonlinear Time History Analysis ◽  
Viscous Dampers ◽  
Existing Building ◽  
Concrete Frame ◽  
Uniform Drift ◽  
Nonlinear Time History

For the lack of research in the longitudinal frame of prefabricated structure for its weak lateral stiffness, pushover analysis is conducted to evaluate the seismic performance of a fabricated concrete frame. Based on case study, the strengthening strategies with viscous dampers are analyzed. In view of the undesirable drift distribution and failure mode in the existing building, it is believed that arrangement of dampers should be designed to attain a uniform drift distribution. Based on the nonlinear time history analysis method, the strategy of damper allocation in vertical direction of the structure is investigated .Results indicate that a proper design might be attained based on the property of existing system, leading to a uniform drift distribution and better seismic performance.

Fling-step recovering from near-source waveforms and ground displacement attenuation models

2020 ◽  
Author(s):  
Maria D'Amico ◽  
Erika Schiappapietra ◽  
Giovanni Lanzano ◽  
Sara Sgobba ◽  
Francesca Pacor
Keyword(s):  
Low Frequency ◽  
Time History ◽  
Strong Motion ◽  
Response Spectra ◽  
Ground Displacement ◽  
Permanent Displacement ◽  
Processing Scheme ◽  
Long Period ◽  
Fling Step ◽  
Attenuation Models

<p>We present a processing scheme (eBASCO, extended BASeline COrrection) to remove the baseline of strong-motion records by means of a piece-wise linear de-trending of the velocity time history. Differently from standard processing schemes, eBASCO does not apply any filtering to remove the low-frequency content of the signal. This approach preserves both the long-period near-source ground-motion, featured by one-side pulse in the velocity trace, and the offset at the end of the displacement trace (fling-step). Hence, the software is suitable for the identification of fling-containing strong-motion waveforms. Here, we apply eBASCO to reconstruct the ground displacement of more than 400 three-component near-source waveforms recorded worldwide (NESS1, http://ness.mi.ingv.it/; Pacor et al., 2019) with the aim of: 1) extensively testing the eBasco capability to capture the long-period content of near-source records; 2) calibrating attenuation models for peak ground displacement (PGD), 5% damped displacement response spectra (DS), permanent displacement amplitude (PD) and period (Tp). The results could provide a more accurate estimate of ground motions, to be adopted for different engineering purposes such as performance-based seismic design of structures.</p><p>Pacor F., Felicetta C., Lanzano G., Sgobba S., Puglia R., D’Amico M., Russo E., Baltzopoulos G., Iervolino I. (2018). NESS v1.0: A worldwide collection of strong-motion data to investigate near source effects. Seismological Research Letters. https://doi.org/10.1785/0220180149</p>

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