Earthquake Probability of the “Seismic Gap” on the Longmenshan Fault     

Song Jin  Jiang Haikun  Meng Lingyuan  Zang Yang 《中国地震研究》2018,32(1):15-27

Using the layered viscoelastic medium model, this paper calculated the coulomb stress loading effect on the Lushan epicenter generated by the Wenchuan earthquake. Then combined with the rate-state friction law proposed by Dieterich J. (1994), we obtain the probability of an M_W ≥ 6.0 earthquake occurring in the vicinity of Lushan. The results show that the probability of M_W ≥ 6.0 earthquake of the Lushan region in 2013 is up to 18%, indicating that the stress disturbance caused by the Wenchuan earthquake accelerated the Lushan earthquake. This paper also calculates the coulomb stress accumulation on the "seismic gap" generated by the two earthquakes of Wenchuan and Lushan, and combined with the background seismicity, gives the M_W>6.0 earthquake probability of the "seismic gap". Although there may be a certain error in the results because of the Dayi earthquake, selection of the medium model parameters and background seismicity, the seismic probability of the "seismic gap" is increasing. Thus, we think destructive earthquakes are still likely to occur in the "seismic gap".  相似文献   

龙门山断层地震周期及其动力学过程模拟研究   总被引：1，自引：1，他引：0       下载免费PDF全文

马林飞  陶玮  张永  曾明会  郑茜 《地球物理学报》2018,61(5):1824-1839

在断层面上引入速率-状态相依摩擦本构关系、考虑铲形逆冲断层几何结构特征、断层下盘和上盘中下地壳及上地幔为黏弹性介质、上盘上地壳为弹塑性介质,本文用二维有限元动力学模型模拟了龙门山断层上大震准周期复发行为、分析了断层上地震孕育位置、地震周期不同阶段的应力/应变场演化特征.不同于近垂直走滑断层上的地震周期行为,大陆铲形逆冲断层上的构造应力的积累和释放过程更复杂、有其独特性.我们得到如下认识：（1）铲形逆冲断层上的地震复发是准周期行为.（2）龙门山断层最大库仑应力位于断层17~20 km深处,应力长期积累和同震释放都在此深度最大,说明地震会在此处孕育、发动.（3）在断层破裂的深部和浅部,同震滑动大小和构造应力释放大小并非同步,而是差异悬殊.（4）地震仅部分释放区域积累的应变能,断层上盘上地壳顶部和底部的褶皱、破裂等永久变形形式也是释放应变能的重要形式.（5）应变能密度增量的演化图像分为：震间、同震、震后期,清晰反应了龙门山断层附近的地震动力学过程.（6）地震发生除释放能量外,同时也对近断层的中地壳和断层底部有很大的应变能加载;这些加载,在震后期可能通过震后滑移、余震或中下地壳乃至上地幔的驰豫形变用几十年时间释放.以上对大陆内铲形逆冲断层上变形特征的了解,有助于我们在其地震周期行为中评估地震危险性.  相似文献   

Influence of connection typology on seismic response of MR‐Frames with and without ‘set‐backs’          下载免费PDF全文

Rosario Montuori  Elide Nastri  Vincenzo Piluso  Marina Troisi 《地震工程与结构动力学》2017,46(1):5-25

The work presented is aimed at the investigation of the influence of beam‐to‐column connections on the seismic response of MR‐Frames, with and without ‘set‐backs’, designed according to the Theory of Plastic Mechanism Control. The investigated connection typologies are four partial strength connections whose structural details have been designed to obtain the same flexural resistance. The first three joints are designed by means of hierarchy criteria based on the component approach and are characterized by different location of the weakest joint component, leading to different values of joint rotational stiffness and plastic rotation supply and affecting the shape of the hysteresis loops governing the dissipative capacity. The last typology is a beam‐to‐column connection equipped with friction pads devoted to the dissipation of the earthquake input energy, thus preventing the connection damage. An appropriate modelling is needed to accurately represent both strength and deformation characteristics, especially with reference to partial‐strength connections where the dissipation of the earthquake input energy occurs. To this aim, beam‐to‐column joints are modelled by means of rotational inelastic springs located at the ends of the beams whose moment‐rotation curve is characterized by a cyclic behaviour which accounts for stiffness and strength degradation and pinching phenomena. The parameters characterizing the cyclic hysteretic behaviour have been calibrated on the base of experimental results aiming to the best fitting. Successively, the prediction of the structural response of MR‐Frames, both regular frames and frames with set‐backs, equipped with such connections has been carried out by means of both push‐over and Incremental Dynamic Analyses. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Seismic reliability‐based ductility demand evaluation for inelastic base‐isolated structures with friction pendulum devices          下载免费PDF全文

Paolo Castaldo  Bruno Palazzo  Tatiana Ferrentino 《地震工程与结构动力学》2017,46(8):1245-1266

The aim of this work is to propose seismic reliability‐based relationships between the strength reduction factors and the displacement ductility demand of nonlinear structural systems equipped with friction pendulum isolators (FPS) depending on the structural properties. The isolated structures are described by employing an equivalent 2dof model characterized by a perfectly elastoplastic rule to account for the inelastic response of the superstructure, whereas, the FPS behavior is described by a velocity‐dependent model. An extensive parametric study is carried out encompassing a wide range of elastic and inelastic building properties, different seismic intensity levels and considering the friction coefficient as a random variable. Defined a set of natural seismic records and scaled to the seismic intensity corresponding to life safety limit state for L'Aquila site (Italy) according to NTC08, the inelastic characteristics of the superstructures are designed as the ratio between the average elastic responses and increasing strength reduction factors. Incremental dynamic analyses (IDAs) are developed to evaluate the seismic fragility curves of both the inelastic superstructure and the isolation level assuming different values of the corresponding limit states. Integrating the fragility curves with the seismic hazard curves related to L'Aquila site (Italy), the reliability curves of the equivalent inelastic base‐isolated structural systems, with a design life of 50 years, are derived proposing seismic reliability‐based regression expressions between the displacement ductility demand and the strength reduction factors for the superstructure as well as seismic reliability‐based design (SRBD) abacuses useful to define the FPS properties. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Evaluating simplified models in predicting global seismic responses of a shake table–test building isolated by triple friction pendulum bearings     

Nhan D. Dao  Keri L. Ryan  Hieu Nguyen-Van 《地震工程与结构动力学》2019,48(6):594-610

This paper evaluates the ability of simplified superstructure models, including two shear frame models and a single-story model, in predicting global responses of a full-scale five-story steel moment-frame buildings isolated by triple friction pendulum bearings subjected to earthquake motions. The investigated responses include displacement of the isolation system, roof drift, story drift, and floor acceleration. Mechanical properties of the simplified superstructure models were derived from the modal information of a verified full 3-D model. The comparison between the analytical responses and experimental responses shows that the simplified models can well predict the displacement of the isolation system. Furthermore, the shear-frame models are adequate for predicting floor acceleration when the specimen is subjected to horizontal ground motions. However, when the specimen is subjected to 3-D motions, the shear-frame models un-conservatively predict floor acceleration. The full 3-D model improves the prediction of story drift compared with the simplified models for both horizontal and 3-D motions.  相似文献   

FVD与FPB在大跨长联减隔震体系梁桥中的联合作用机理研究          下载免费PDF全文

刘正楠  陈兴冲  张永亮  丁明波  张熙胤 《地震工程学报》2019,41(3):619-625

为验证液体黏滞阻尼器(FVD)与摩擦摆支座(FPB)组合在大跨长联减隔震体系梁桥中的应用效果,以一联(50+8×100+50) m预应力混凝土连续梁桥为工程背景,建立全桥有限元模型,通过输入场地地震安评报告提供的50年超越概率为2%的三条人工模拟地震波,开展单独及组合使用液体黏滞阻尼器和摩擦摆支座的大跨长联梁桥减隔震研究,从能量耗散的角度揭示液体黏滞阻尼器与摩擦摆支座组合在大跨长联减隔震体系梁桥中的联合作用机理。结果表明,大跨长联梁桥仅使用黏滞阻尼器,其长周期特性激发黏滞阻尼器充分发挥耗能,但无法避免对固定墩的地震损伤;仅使用摩擦摆支座隔震在纵(横)向强震下会引起支座位移超限;摩擦摆支座与黏滞阻尼器组合的减震机理为摩擦摆支座提供墩梁间的弱连接,激发墩梁间的相对速度,促进黏滞阻尼器(速度型)充分发挥阻尼耗能作用。另外,组合减震方案中摩擦摆支座为辅助耗能装置,黏滞阻尼器为主要耗能装置,且主控梁体位移;相比仅使用摩擦摆支座隔震,由于黏滞阻尼器激发的阻尼力增强了墩梁间约束,这种组合减隔震可能使结构输入能量增加,从而导致地震反应加剧。  相似文献   

Numerical modeling of MDOF structures with sliding supports using rigid‐plastic link     

A. Vafai  M. Hamidi  G. Ahmadi 《地震工程与结构动力学》2001,30(1):27-42

In this paper, the responses of multi‐degree‐of‐freedom (MDOF) structures on sliding supports subjected to harmonic or random base motions are investigated. Modeling of the friction force under the foundation raft is accomplished by using a fictitious rigid link which has a rigid–perfectly plastic material. This will result in identical equations of motion for the sliding structure, both in the sliding and non‐sliding (stick) phases which greatly simplifies the implementation of the method into a numerical algorithm. In this model the phase transition times are determined with high accuracy. This has two advantages: first, it prevents the so‐called high‐frequency oscillation of the relative velocity at the end of the sliding phase, and second, the time steps can be selected so that each falls exactly within one phase of motion. In this case, the stiffness matrix of the structure remains constant throughout each phase and thus any method for solving the non‐linear differential equations of motion (e.g. Newmark method) can be used without iteration. The proposed method, besides its simplicity, is numerically very efficient and considerably reduces the required analysis time compared with most of the other methods. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Equilibration of saltation     

Peter‐Jost Spies  Ian K. McEwan 《地球表面变化过程与地形》2000,25(4):437-453

A two‐dimensional numerical model of the saltation process was developed on a parallel computer in order to investigate the temporal behaviour of transport rate as well as its downwind distribution. Results show that the effects of unsteady flow on the transportation of particulates (sediment) have to be considered in two spatial dimensions (x, y). Transport rate Q(x, t) appears in the transport equation for mass M(x, t): where A = ΔxW denotes unit area composed of unit streamwise length Δx and width W. S(x, t) (units kg m⁻² s⁻¹) stands for the balance over the splash process. A transport equation for transport rate itself is suggested with U _c (x, t) a mean particle velocity at location x as the characteristic velocity of the grain cloud. For a steadily blowing wind over a 50 m long sediment bed it was found that downwind changes in Q cease after roughly 10–40 m, depending on the strength of the wind. The onset of stationarity (∂/∂t=0) was found to be a function of the friction velocity and location. The local equilibrium between transport rate and wind was obtained at different times for different downstream locations. Two time scales were found. One fast response (in the order of 1) to incipient wind and a longer time for equilibrium to be reached throughout the simulation length. Transport rate also has different equilibrium values at different locations. A series of numerical experiments was conducted to determine a propagation speed of the grain cloud. It was found that this velocity relates linearly to friction velocity. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Seismic response of rotating machines–structure–RFBI systems     

Wen‐Chyi Su  Alan G. Hernried  Solomon C. S. Yim 《地震工程与结构动力学》2000,29(2):213-240

The seismic response of a critical rotating machine either rigidly attached to a floor or independently isolated housed within an initially aseismically designed or uncontrolled structure are investigated. A particular isolation system, the Resilient‐Friction Base Isolator (RFBI), is employed. Finite element formulations of a rotor‐disk‐bearing model on a rigid base are developed. The equations of motion for the combined rotating machine–structure–RFBI systems are presented. Parametric studies are performed to investigate the effects of variations in system physical properties including friction coefficient, mass ratio, shaft flexibility, bearing rigidity, bearing damping and speed of rotation on the response of rotating machines for the combined rotating machine–structure–isolator systems. Comparative studies in the peak response of the rotating machine supported on various isolation systems and the corresponding fixed base system are carried out. The study indicates that the Resilient‐Friction Base Isolator can significantly reduce the seismic response of rotating components to potentially damaging ground excitations. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Design of friction damped structures using lateral force procedure     

Yaomin Fu  Sheldon Cherry 《地震工程与结构动力学》2000,29(7):989-1010

A trilinear model is used to simulate the seismic resisting mechanism of a single‐degree‐of‐freedom friction‐damped system to reflect the situation in which both dampers and frame members lose their elastic resistance. The seismic response of the friction‐damped system is normalized with respect to the response of its corresponding linear system by an approach that incorporates a credible equivalent linearization method, a damping reduction rule and the algebraic specification of the design spectrum. The resulting closed‐form solutions obtained for the normalized response are then used to define a force modification factor for friction‐damped systems. This force modification factor, together with the condensation procedure for multi‐degree‐of‐freedom structures, enables the establishment of a quasi‐static design procedure for friction‐damped structures, which is intended for the benefit and use of structural practitioners. A curve‐fitting technique is employed to develop an explicit expression for the force modification factor used with the proposed design procedure; it is shown that this simplification results in satisfactory accuracy. Finally, a design example is given to illustrate the validation of the proposed design procedure. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献