Dynamic Seismic Analysis Research Articles

An Improved Approach for Nonstationary Strong Ground Motion Simulation

A new stochastic ground motion model for generating a suite of ground motion time history with both temporal and frequency nonstationarities for specified earthquake and site characteristics is proposed based on the wavelet method. This new model is defined in terms of 6 key parameters that characterize the duration, evolving intensity, predominant frequency, bandwidth and frequency variation of the ground acceleration process. All parameters, except for peak ground acceleration (PGA), are identified manually from a database of 2444 recorded horizontal accelerations. The two-stage regression analysis method is used to investigate the inter- and intra-event residuals. For any given earthquake and site characteristics in terms of the fault mechanism, moment magnitude, Joyner and Boore distance and site shear-wave velocity, sets of the model parameters are generated and used, in turn, by the stochastic model to generate strong ground motion accelerograms, which can capture and properly embody the primary features of real strong ground motions, including the duration, evolving intensity, spectral content, frequency variation and peak values. In addition, it is shown that the characteristics of the simulated and observed response spectra are similar, and the amplitude of the simulated response spectra are in line with the predicted values from the published seismic ground motion prediction equations (SGMPE) after a systematic comparison. The proposed method can be used to estimate the strong ground motions as inputs for structural seismic dynamic analysis in engineering practice in conjunction with or instead of recorded ground motions.

Seismic elastic analysis of light timber-frame multi-storey buildings: Proposal of an iterative approach

This paper deals with the static and dynamic seismic analysis of light timber-frame buildings. Through the use of the UNITN-model proposed in a previous work, the study is here extended to full-scale buildings. An iterative procedure to properly distribute a horizontal load to the shear-walls, considering the coupled action of the vertical-load and the hold-downs state, is developed; three methods for the application of the response spectrum analysis are proposed as well. These methods may be used to predict the seismic-behaviour and to design non-regular timber shear-walls buildings. A numerical example illustrates the application of the procedures.

The Force Analysis of Anchor Anti-Slide Pile in Slope Reinforcement under Seismic Load

The force affect factors of anchor anti-slide pile in slope reinforcement under seismic load are studied in this paper. First of all, the method of dynamic analysis is introduced in FLAC3D. At the same time, seismic wave is selected in seismic dynamic analysis. Then, the sensitivity influence of anti-slide pile design parameters on dynamic contact stress, shear force and dynamic bending moment is analyzed by applying the seismic wave, giving the most significant effect factors of the dynamic contact stress and dynamic moment. In the end, the distribution regular of the contact force and the pile body stress under earthquake action is analyzed by selecting a case, laying a theoretical foundation for the further study of the dynamic performance of the reinforced slope.

Ground motion selection for simulation‐based seismic hazard and structural reliability assessment

SummaryThis paper examines four methods by which ground motions can be selected for dynamic seismic response analyses of engineered systems when the underlying seismic hazard is quantified via ground motion simulation rather than empirical ground motion prediction equations. Even with simulation‐based seismic hazard, a ground motion selection process is still required in order to extract a small number of time series from the much larger set developed as part of the hazard calculation. Four specific methods are presented for ground motion selection from simulation‐based seismic hazard analyses, and pros and cons of each are discussed via a simple and reproducible illustrative example. One of the four methods (method 1 ‘direct analysis’) provides a ‘benchmark’ result (i.e., using all simulated ground motions), enabling the consistency of the other three more efficient selection methods to be addressed. Method 2 (‘stratified sampling’) is a relatively simple way to achieve a significant reduction in the number of ground motions required through selecting subsets of ground motions binned based on an intensity measure, IM. Method 3 (‘simple multiple stripes’) has the benefit of being consistent with conventional seismic assessment practice using as‐recorded ground motions, but both methods 2 and 3 are strongly dependent on the efficiency of the conditioning IM to predict the seismic responses of interest. Method 4 (‘generalized conditional intensity measure‐based selection’) is consistent with ‘advanced’ selection methods used for as‐recorded ground motions and selects subsets of ground motions based on multiple IMs, thus overcoming this limitation in methods 2 and 3. Copyright © 2015 John Wiley & Sons, Ltd.

Elastic-Plastic Seismic Response Analysis on the Special-Shaped Chimney

Based on one 240-meter-high special-shaped RC chimney, the structure’s dynamic performance and elastic-plastic seismic response analysis has been studied in detail. From the analysis, it demonstrates the weak areas in the chimney. The interlayer displacement angle about corresponding performance points under four kinds of loading mode were also acuired, and the response of four loading patterns were analyzed.

An optimization method for the generation of ground motions compatible with multi-damping design spectra

For some crucial engineering projects, a compatible time history of ground motions is required as a loading input for seismic dynamic analysis. The compatibility with multi-damping design spectra is critical to make sure the high reliability of analysis results. In previous methods, ground motions were hard to be tuned highly compatible with multi-damping design spectra.Hence we propose a method to optimize the compatibility of a seed ground motion history, which is either obtained from actual seismic records or generated from previous methods, by superimposing adjusted ground motions in the time domain through the L∞ norm minimization. The optimization process makes the influences of the superimposed ground motions to the response spectra be under control by constraining objective variables. The high precision of the method is demonstrated by a concrete example, in which the max difference between the response spectra of the optimized ground motions and the design spectra for RG1.60 data [1] is 5.06% under five different damping ratios, and all response spectra envelope the design spectra.

Seismic low-cycle fatigue evaluation of welded beam-to-column connections in steel moment frames through global–local analysis

A general methodology for seismic low-cycle fatigue assessment of welded beam-to-column connection in steel moment resisting frames (SMRFs) is presented. Fatigue deformability curves of seven connection categories are elaborated using the available cyclic tests. Inter-storey drift history imposed on each connection of SMRF is generated by seismic dynamic analysis and adopted in fatigue damage calculation based on Palmgren–Miner’s rule and the experimentally determined fatigue curve. The most critical connection identified by preliminary fatigue evaluation is refined with solid finite elements in global–local model where the cyclic void growth model is integrated to give a more accurate fatigue prediction including load sequence effects. The proposed approach is applicable to fatigue evaluation of welded connections in SMRFs under earthquakes.

The Flat Truss Dynamic Characteristics and Seismic Response Analysis

Flat truss is a new form of truss and are widely used in large-span space structure, Suzhou Railway Station roof of the main use of space for large-span steel diamond plate truss structure, the local two-way cross-diamond-shaped truss.Sap2000 v14 large general-purpose finite element analysis software, the modal analysis of the structure, and the modal response spectrum method the structure of X, Y, Z three earthquake, so as to arrive seismic coefficient of internal force distribution law, obtained the natural frequency of the structure, the vibration characteristics of the structure, so that the corresponding structural measures its weak parts of the structure, provides a sufficient basis for the safe use of the design and construction of the structure.

Seismic Vulnerability Assessment of Multistory Timber Braced Frame Traditional Masonry Structures

Research carried out on the seismic investigation of timber braced frame (TBF) masonry structures of traditional construction practice is presented, essential for seismic performance evaluation of such construction type using engineering approaches. An innovative simplified equivalent frame method (EFM) based on macro modelling approach is presented for nonlinear dynamic seismic analysis of TBF masonry structures. The modelling include EFM idealization of wall using stiff elastic beam-column element assigned with moment-rotation (M-θ) nonlinear lumped plasticity hinges. Earlier, the approach i.e. the EFM idealization and M-θ constitutive law, is calibrated with the experimental results obtained through quasi-static cyclic test on full scale walls. The technique is further extended herein for seismic dynamic analysis of multistory structures. Generalization of the technique for modelling walls of various geometry and loading is performed. It included nonlinear static pushover analysis of various case study walls, by means of SAP2000 calibrated earlier with experimental results, for the derivation of lateral force-deformability behavior towards the development of generalized M-θ constitutive law for TBF masonry walls. Three representative structures, from one to three storeys, are analyzed using a suite of ten natural accelerograms and incremental dynamic analysis technique. Structure fragility and resilience functions are derived using a fully probabilistic and dynamic approach. The structures analyzed in the present study represent TBF masonry wall structures, called as Dhajji-Dewari structures, common in Northern areas of Pakistan.

Simplified engineering tools for seismic analysis and design of traditional Dhajji-Dewari structures

This paper presents simplified engineering tools for seismic analysis of traditional Dhajji-Dewari structures, a concentrically braced timber frame with masonry infill, within the context of vulnerability assessment of existing stock, strengthening and restoration of historical heritage and feasibility analysis of future construction projects. Similar like structures can be found in various parts of America, Asia, Europe and the Middle-East. The study included tools for the evaluation of lateral force-deformability characteristics of Dhajji walls using non-linear static pushover analysis, simplified models for nonlinear dynamic time history analysis of Dhajji wall structures subjected to ground shaking, and simplified models for seismic performance evaluation of Dhajji wall structures using hand calculations. Three full scale Dhajji walls tested quasi-static-cyclically, with additional 18 tension and bend tests on timber frame connections, at the Earthquake Engineering Center of Peshawar are analyzed to understand the damage mechanism and salient features of the system in resisting lateral load, retrieve lateral force-deformability behavior, hysteresis response and viscous damping (energy dissipation) of Dhajji walls in order to calibrate tools for nonlinear static and dynamic seismic analysis of Dhajji wall structures. Applications are shown on the seismic performance assessment of example structures and design of new construction schemes. The findings from the present research study can provide help on the seismic performance evaluation of similar like concentrically braced timber frame masonry wall structures.

Dynamic Characteristics and Seismic Response Analysis of Self-Anchored Suspension Bridge

Self-anchored suspension bridge is widely used in Chinese City bridge engineering for the past few years. Because the anchorage system of main cable has been changed from anchorage blocks to the ends of the girder, its’ dynamic mechanics behavior is greatly distinguished with the traditional earth anchored suspension bridge. This paper studies the dynamic characteristics and seismic response of one large-span self-anchored suspension bridge which is located in China/Shenyang city. Using a spatial dynamic analysis finite element mode, the dynamic characteristics are calculated out. An artificial seismic wave is adopted as the ground motion input which is fitted with acceleration response spectrum according to the Chinese bridge anti-seismic design code. Time-integration method is used to get the seismic time-history response. Geometry nonlinear effect is considered during the time-history analysis. At last, the dynamic characteristics and the behavior of earthquake response of this type bridge structure are discussed clearly. The research results can be used as the reference of seismic response analysis and anti-seismic design for the same type of bridge.

Dynamic Performance and Seismic Analysis of Tied Arch Bridge

Dynamic Performance and Seismic Analysis of Tied Arch Bridge

Seismic Response Analysis of Different Plane Structure in Horizontal Direction

The results of theoretical research and earthquake damage investigation show that seismic response analysis of different plane structure in horizontal direction is different. Dynamic characteristics and seismic response analysis of four kinds of architectural models with different planes were analyzed by using the finite element analysis software. The inherent characteristics and earthquake time-history curves in different intensity level X, Y direction of displacement, velocity, acceleration and angle displace were studied. The results show that the seismic response of the four kinds of structures separates gradually, and the separation gap increases with increase of earthquake intensity. The building structure is safer in the long side direction than that in the short side in lateral earthquake response. The irregular structure can cause strong response in both horizontal in a single direction of earthquake effect. The second floor is a weak layer of the building structure which should be paid more attention to.

Dynamic Properties Analysis for Self-Anchored Suspension and Cable-Stayed Combination System Bridge

In view that dynamics research for self-anchored suspension and cable-stayed combination system bridge lags behind the practical application, this thesis analyzed its dynamic properties and seismic responses. By means of constructing a dynamic finite element model of the bridge for the dynamic properties and seismic response analysis, the thesis discovered the dynamic properties and the seismic responses laws of self-anchored suspension and cable-stayed combination system bridge. The dynamic finite element model was constructed based on the dynamic analysis theory and method, under the background of the first self-anchored suspension and cable-stayed combination system bridge in the world, and it was verifyed by on-site vibration test. The dynamic properties and the seismic responses laws provides a valuable reference for the design and maintenance of this type of bridge.

Analysis on Aseismic Performance of the Beijing Yintai Center

In this study, the seismic behavior of the main tower building of Beijing Yintai Center is presented with regard to the dynamic characteristics analysis and seismic response analysis. Firstly, by means of three-dimensional finite element analysis software, the dynamic properties and seismic responses under frequent earthquake action of the structure are obtained, respectively. It can be seen that the structure has a rational arrangement for structural elements and has a good seismic behavior. Then, the seismic behavior of the structure is studied through the dynamic elasto-plastic analysis method and static elasto-plastic analysis method under rare earthquake. Analysis results of both analysis methods show that the behavior of the structure accords with the earthquake performance objectives and the structure would not collapse under the rare earthquake action.

시간영역 인공지진파 생성

국내에서 내진설계의 중요성이 점차적으로 부각되고 있으며 이에 따라 설계 시 동적 지진해석의 수행빈도가 높아지고 있다. 동적 지진해석을 수행하기 위한 가장 중요한 입력변수 중 한가지는 입력지진파이다. 그러나 현재 국내에서는 지진학적 검토 없이 미국, 일본 등에서 계측된 강진 기록을 입력지진파로 사용하거나 주파수영역에서 생성된 인공지진파를 사용하고 있다. 국외 계측 지진기록은 지진 규모에 따라 변화하는 지속시간과 에너지를 고려할 수 없어서 국내 지진환경에는 적합하지 않으며, 주파수 영역에서 생성되는 설계응답스펙트럼에 맞춤형 인공지진파는 실제 지진기록과 주파수 특성이 상이한 문제가 있다. 본 연구에서는 이와 같은 입력지진파의 문제점을 극복하기 위하여 시간영역에서 수행되는 응답스펙트럼 맞춤형 인공지진파 알고리즘을 적용하여 입력 지진파를 생성하였다. 생성된 지진파는 계측 지진기록의 고유한 성질인 Non-stationary 특성을 보존하며 동시에 설계 응답스펙트럼과 거의 완벽한 일치성을 보이는 것으로 나타났다. The importance of seismic design is greatly emphasized recently in Korea, resulting in an increase in the number of dynamic analysis being performed. One of the most important input parameters for the dynamic seismic analysis is input ground motion. However, it is common practice to use recorded motions from U.S. or Japan without considering the seismic environment of Korea or synthetic motions generated in the frequency domain. The recorded motions are not suitable for the seismic environment of Korea since the variation in the duration and energy with the earthquake magnitude cannot be considered. The artificial motions generated in frequency domain used to generated design response spectrum compatible ground motion has the problem of generating motions that have different frequency characteristics compared to real recordings. In this study, an algorithm that generates target response spectrum compatible ground motions in time domain is used to generate a suite of input ground motions. The generated motions are shown to preserve the non-stationary characteristics of the real ground motion and at the same, almost perfectly match the design response spectrum.

A modified method for simulating non-stationary multi-point earthquake ground motion

A spectral-representation-based algorithm is proposed to simulate non-stationary and stochastic processes with evolutionary power, according to a prescribed non-stationary cross-spectral density matrix. Non-stationary multi-point seismic ground motions at different locations on the ground surface are generated for use in engineering applications. First, a modified iterative procedure is used to generate uniformly modulated non-stationary ground motion time histories which are compatible with the prescribed power spectrum. Then, ground motion time histories are modeled as a non-stationary stochastic process with amplitude and frequency modulation. The characteristic frequency and damping ratio of the Clough-Penzien acceleration spectrum are considered as a function of time in order to study the frequency time variation. Finally, two numerical examples are presented to validate the efficiency of the proposed method, and the results show that this method can be effectively applied to the dynamic seismic analysis of long and large scale structures.

Earthquake prediction: basics, achievements, perspectives

The recent scientific advances in understanding the hierarchical nature of the lithosphere and its dynamics based on systematic monitoring and evidence of its space-energy similarity at global, regional, and local scales did result the design of reproducible intermediate-term middle-range earthquake prediction technique. The real-time experimental testing aimed at prediction of the largest earthquakes world-wide from 1992 to the present proved statistically a possibility of practical earthquake forecasting although of limited precision. In the first approximation, an accuracy of 1-5 years and 5-10 times the anticipated source dimension is achieved. Further analysis of seismic dynamics allows reducing the spatial uncertainty down to 1-3 source dimensions, although at the cost of additional failures-to-predict. Despite of limited accuracy a considerable damage could be prevented by timely knowledgeable use of the existing predictions and earthquake prediction strategies. The link of theoretical research in modeling earthquake sequences in frames of statistical physics on the one hand and instrumental and algorithm developments on the other hand help developing a new generation of earthquake prediction technique of higher accuracy.

Pivot Hysteresis Model for Reinforced Concrete Members

For nonlinear dynamic seismic analysis of bridge structures to be practical, only the dominant nonlinear characteristics of the structure should be included. Based on capacity design principles, the current seismic bridge design philosophy is generally to force all member nonlinearities into the ends of ductile columns. Therefore, nonlinear characteristics of the columns must be adequately defined. In this paper, a hysteresis model is presented that accurately captures the nonlinear behavior of reinforced concrete members in terms of a force-displacement, or moment-rotation, response. What makes this model attractive, when compared with other hysteresis models, is that unsymmetric sections (nonsymmetric cross-section geometry and/or tension reinforcement amounts in the two loading directions), a cyclic axial load, and strength degradation may be included. The model is based on a few simple rules. Results based on the proposed hysteresis model show close agreement with various experiments on reinforced concrete members.

A Cyclic Nonlinear Model for Concrete-Filled Tubes. I: Formulation

This paper presents a three-dimensional (3D) cyclic nonlinear finite-element model for concrete-filled steel tube (CFT) beam-columns and composite frame structures. This CFT beam finite element is incorporated into a matrix analysis program suitable for conducting monotonic static, cyclic static, or transient dynamic seismic analyses of complete composite unbraced frame structures composed of steel I-girders framing biaxially into CFT beam-columns. The material formulation consists of a concentrated plasticity bounding surface model in 3D stress-resultant (force) space. A polynomial expression developed in previous work to represent CFT cross-section strength is incorporated into this material model to represent the force-space yield surfaces. In addition, new formulations are present for isotropic and kinematic hardening of the loading and bounding surfaces to model strength degradation and stiffness deterioration of CFTs subjected to cyclic loading. Part II of this two-part paper presents the calibration and verification of the CFT element. This formulation is verified against a comprehensive set of experimental data and is accurate for a wide range of CFT cross-section sizes and material strengths.