改进的前馈型神经网络模型在承压水漏斗水位预报中的应用     

吴蓉  周志芳 《江苏地质》2002,26(1):19-21

建立了以改进Powell法优化的前馈型神经网络模型，模型既具有强大的函数逼近功能，又克服了传统神经网络优化方法的缺点。将神经网络模型用于承压水漏斗的动态水位预报，实例表明：模型预报效果较好。  相似文献   

约束砖砌体结构的弹塑性时程分析     

徐德良  刘伟庆  刘经伟 《地震工程与工程振动》2002,22(5):57-61

本文对超《规范》的大开间采取在墙体中增设钢筋混凝土墙中柱和水平条带的加强措施，为验证原型结构的抗震能力，在大比例模型试验的基础上，对约束砖砌体原型结构进行弹塑性时程分析，得出结构层次位移反应包络图，论证了结构采取此项加强措施后能满足7度区相应的抗震设防要求。  相似文献   

Yield design of dry‐stone masonry retaining structures—Comparisons with analytical,numerical, and experimental data     

A. S. Colas  J. C. Morel  D. Garnier 《国际地质力学数值与分析法杂志》2008,32(14):1817-1832

Over the past few years, there has been a steady increase in the interest in dry‐stone walling not only to preserve existing constructions but also to build new ones. Yet, dry masonry's expansion is slowed down by the lack of scientific knowledge to assess its reliability. This study aims at contributing to the construction of this scientific frame using a simplified model based on yield design and homogenization, which can be directly exploited for engineering purposes. A new analytical expression of the ultimate load is thus established. Then, the validity of the method is assessed by comparisons with limit equilibrium analysis, distinct element method, and field trials. Finally, possible improvements of the model are discussed. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Rigid element model for in‐plane dynamics of masonry walls considering hysteretic behaviour and damage     

Siro Casolo  Fernando Peña 《地震工程与结构动力学》2007,36(8):1029-1048

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Failure of masonry arches under impulse base motion     

Laura De Lorenzis  Matthew DeJong  John Ochsendorf 《地震工程与结构动力学》2007,36(14):2119-2136

Recent seismic events have caused damage or collapse of invaluable historical buildings, further proving the vulnerability of unreinforced masonry (URM) structures to earthquakes. This study aims to understand failure of masonry arches—typical components of URM historic structures—subjected to horizontal ground acceleration impulses. An analytical model is developed to describe the dynamic behaviour of the arch and is used to predict the combinations of impulse magnitudes and durations which lead to its collapse. The model considers impact of the rigid blocks through several cycles of motion, illustrating that failure can occur at lower ground accelerations than previously believed. The resulting failure domains are of potential use for design and assessment purposes. Predictions of the analytical model are compared with results of numerical modelling by the distinct element method, and the good agreement between results validates the analytical model and at the same time confirms the potential of the distinct element framework as a method of evaluating complex URM structures under dynamic loading. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Tectonic significance of Late Neoproterozoic granites from the Tibesti massif in southern Libya inferred from Sr and Nd isotopes and U–Pb zircon data   总被引：1，自引：0，他引：1  

Ismail B. Suayah  Jonathan S. Miller  Brent V. Miller  Tovah M. Bayer  John J.W. Rogers   《Journal of African Earth Sciences》2006,44(4-5):561

The Neoproterozoic crust of the Tibesti massif was stabilized by magmatism that included subduction-generated batholithic suites and post-orogenic granite plutons. All of the magmatism occurred in a period of about 20 million years centered around 550 Ma, and nearly all of the granites have initial ⁸⁷Sr/⁸⁶Sr ratios of about 0.706. The Wadi Yebigue pluton has U–Pb zircon ages of 563 Ma and 558 Ma on two different phases and ε_Nd at 550 Ma from −0.5 to −2.2. These isotopic data and the geologic history of the massif suggest that granites in the Tibesti massif developed during and shortly after closure of a short-lived ocean basin that developed by fragmentation of pre-existing continental crust of the Saharan region.  相似文献   

砌体结构并联复合隔震建筑有限元分析     

赵士永  李旭光 《华北地震科学》2011,29(2):23-26

本文以某六层砌体橡胶隔震支座与摩擦滑移支座的并联复合隔震结构为例,运用有限元分析程序,对该建筑的一般抗震结构和并联复合隔震结构分别进行了地震作用下的有限元时程分析,结果显示:并联复合隔震结构能够降低上部结构的地震反应,提高建筑物的抗震能力,有明显的隔震、减震效果.  相似文献   

Assessment indices for the seismic vulnerability of existing R.C. buildings     

G. E. Thermou  S. J. Pantazopoulou 《地震工程与结构动力学》2011,40(3):293-313

The seismic vulnerability of old multi‐storey reinforced concrete (R.C.) buildings reinforced with substandard details is assessed as a function of interstorey drift demand imposed by the design earthquake while considering brittle termination of elastic response of the critical members of the structure due to a premature shear failure. Interstorey drift demand is related to column and wall translational stiffnesses which are expressed through analytical derivations in terms of the floor area ratios of gravity and lateral load bearing members in the critical floor. Interstorey drift capacity is related to the available transverse reinforcement and the axial load ratio of the vertical members. The significance of the area ratio of vertical members in the typical floor as an index of vulnerability is explored with reference to the limitations in the value of axial load ratio used in R.C. design in order to secure ductile flexural behavior, and also with reference to the stability index of gravity load bearing members. Interstorey Drift Spectra are derived for the existing R.C. buildings suitable for rapid seismic vulnerability screening but also as a guide for rehabilitation of the existing structures. Lightly reinforced or substandard reinforced concrete buildings that reportedly collapsed during previous earthquakes are used as example case studies in order to calibrate the proposed methodology. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Shaking‐table tests of a full‐scale single‐story masonry veneer wood‐frame structure     

Hussein O. Okail  P. Benson Shing  William M. McGinley  Richard E. Klingner  Seongwoo Jo  David I. McLean 《地震工程与结构动力学》2011,40(5):509-530

This paper presents the findings of shaking‐table experiments conducted to examine the seismic performance of a full‐scale, one‐story, wood‐framed structure with masonry veneer. The structure was designed and constructed in accordance with current U.S. code provisions. The veneer was attached to the wood backing with two kinds of metal anchors, corrugated ties fastened with 8d nails and rigid ties fastened with #8 screws. The tests have shown that the use of nails to fasten veneer anchors to the wood studs is highly unreliable due to the high variation of the nail extraction capacity, which can be influenced by the moisture content of the wood. Other than this, both the wood frame and the masonry veneer performed well under severe ground motions far exceeding a design level earthquake for Seismic Design Category D. Good performance was observed for the rigid veneer ties, which were attached to the wood studs with screws. The results have shown that the veneer walls parallel to the direction of shaking helped to restrain the motion of the wood structure and therefore should not be simply treated as added mass. The detailing of wood roof diaphragms requires special attention in consideration of the out‐of‐plane inertia force of the veneer that can be transmitted through the top plate of the wood‐stud wall to the rim joist. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

In situ cyclic tests on existing stone masonry walls and strengthening solutions     

Alexandre A. Costa  António Arêde  Aníbal Costa  Carlos Sousa Oliveira 《地震工程与结构动力学》2011,40(4):449-471

The present work reports on an in situ experimental test campaign carried out on abandoned traditional masonry houses after the 9th July 1998 earthquake that seriously hit the Faial island of Azores. For the testing purposes, an experimental test setup was developed based on a self‐equilibrated scheme, which is herein described reporting on the advantages and drawbacks of this in situ test setup. Five specimens were tested aiming at characterizing the out‐of‐plane behavior of stone masonry walls and strengthening solutions recommended for post‐earthquake interventions. A detailed comparison between solutions' efficiency is presented including a cost vs benefit analysis. In order to assess the efficiency of the developed test setup for other applications on stone masonry walls, an in‐plane test on an existing URM panel is also presented. Several related issues are discussed, namely the advantages of dealing with the real boundary conditions and the capacity of providing valuable information of the response, as well as a detailed analysis of the obtained results. The authors believe that this work provides an increase in knowledge on the seismic behavior of the existing masonry constructions, resulting from the development of an in situ test setup and the efficiency quantification of strengthening solutions. Therefore, the work is thought to positively contribute for the preservation of architectural heritage and for its seismic vulnerability reduction. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献