海城小孤山区辽河群大石桥组地层中硅质岩与成矿探讨     

尤洪喜  赵东芳 《地质与资源》2004,13(3):152-155

在海城市小孤山区辽河群大石桥组一段、三段地层中,都发现了硅质岩的分布.小孤山区硅质岩具有微-细粒变晶结构特点,与铅、锌、银、金矿化密切伴生.通过与青城子硅质岩岩石化学成分及组构特征的对比分析,认为小孤山区硅质岩属于海底火山喷溢-热水沉积成因,与成矿关系极为密切,从而展示了小孤山及外围地区辽河群地层找矿的前景.  相似文献   

近断层地震动下摇摆-自复位桥墩连续梁地震反应          下载免费PDF全文

(葛超洋  孙治国  付建宇  王东升) 《世界地震工程》2023,39(2):113-124

为讨论近断层地震动下摇摆-自复位(Rocking Self-Centering, RSC)桥墩连续梁的地震反应及其抗震优缺点。基于OpenSees有限元分析平台讨论了RSC桥墩三维建模方法,通过对6个试验构件的模拟,比较模拟与试验桥墩滞回曲线、预应力筋最大应力等指标,验证了模型准确性。建立设置RSC桥墩和普通钢筋混凝土(Reinforced Concrete, RC)桥墩的上部结构相同的两座连续梁桥,输入3组含有强速度脉冲的近断层地震波进行非线性动力时程分析,对比其抗震性能。结果表明：在0.4 g近断层地震动下,RSC桥墩与普通RC桥墩相比,RSC桥墩的最大位移角为普通RC桥墩的78.1%～97.6%,墩底曲率延性系数仅为普通RC桥墩的24.0%～34.0%,减小了桥墩的最大变形,也减轻了桥墩地震损伤,不利的一点是使用RSC桥墩会导致支座位移增大。RSC桥墩震后的残余位移较小,且预应力筋处于弹性受力阶段,为实现震后桥梁功能的快速恢复提供了条件。  相似文献   

构造柱和砌筑砂浆对砌体结构抗震能力影响分析     

王骁  孙柏涛  闫培雷  赵河先 《震灾防御技术》2019,14(3):501-512

以汶川地震宏观震中映秀镇(实际烈度Ⅺ度)中裂而未倒且保存较完好的漩口中学南西栋教师宿舍楼为原型,采用有限元软件ABAQUS进行建模分析,研究构造柱布置数量、砂浆强度对砌体结构抗震能力的影响。分别通过改变构造柱布置数量和砂浆强度等级,建立3个模型进行对比分析,选取底层间位移角最大值作为衡量标准。研究结果表明:在遭遇烈度不高于Ⅷ度的地震时,构造柱的作用微乎其微,其布置数量的多少对砌体结构抗震能力的增加效果不明显;在遭遇烈度高于Ⅷ度的地震时,构造柱作用能够显现出来,其布置数量的增加能够有效增加砌体结构的抗震能力;砌体结构的抗震性能随砂浆强度等级的增加而提高。  相似文献   

方钢管混凝土柱-不等高钢梁框架节点抗剪承载力分析          下载免费PDF全文

许成祥  费建宝  简齐安  彭胜 《世界地震工程》2020,(4):053-61

为研究方钢管混凝土柱-H型不等高钢梁框架节点的抗剪承载力,分析其破坏机理,建立适用于不等高钢梁节点的抗剪计算模型,提出了节点的抗剪承载力计算公式,比较了基于不同抗剪模型建立的抗剪承载力计算值与试验值的差异性。结果表明:节点域的破坏模式主要为上核心区的剪切斜压破坏;节点域抗剪承载力主要由钢管腹板、核心区混凝土主斜压杆及约束斜压杆共同承担。对比分析表明:提出的节点屈服抗剪承载力和极限抗剪承载力理论公式计算值更为接近试验值,验证了方钢管混凝土柱-不等高钢梁框架节点传力机理和承载力计算公式的正确性。  相似文献   

The Weathering of Granodiorite Porphyry in the Thiel Mountains, Inland Antarctica   总被引：2，自引：0，他引：2  

Satoshi Ishimaru  & Kenji Yoshikawa 《Geografiska Annaler: Series A, Physical Geography》2000,82(1):45-57

The weathering of granodiorite porphyry is examined in the extremely cold and dry environment of the inland part of Antarctica. Weathering features include granular disintegration, rock varnish, and sheeting. Sheeting has gradually proceeded since the exposing of the nunatak, but the other types of weathering have not actively advanced in recent times.
Granular disintegration primarily comprises the release of individual crystals. The mechanism of this release is that cracks are created along crystal boundaries and cleavages in phenocrysts mainly due to differential thermal expansion. Plagioclase and hypersthene are released more readily than quartz. Disintegration of plagioclase has produced many prism-shaped holes, 0.5 to 2.0 mm in length, while fine-grained quartz crystals, 0.05 to 0.1 mm in diameter, are incidentally released without cracking.
The reddish brown (10R4/4) rock varnishes result from oxidation and consist of limonite, which fills cracks and penetrates into crystals. Ferrous iron in hypersthene, biotite, ilmenite and magnetite is transformed into limonite by oxidation. Manganese is not found in the varnishes. Sulfur, which is important for oxidation and which may have originated from adhered snow, is concentrated on the surface of the rock.
Sheeting has precipitated rock falls, and has gradually formed a gray mosaic on the varnished wall. The sheeting was caused by gravitational body force, which is internal stress of the rock body due to the mass of the overburden.  相似文献   

Reinforced concrete scaled columns under cyclic actions     

Y. Lu  E. Vintzileou  G. -F. Zhang  T. P. Tassios 《Soil Dynamics and Earthquake Engineering》1999,18(2):709

In the area of reduced-scale model testing, increasing the size of model structures as a means of improving the model performance is often inhibited by the capacity limitation of the available seismic testing facilities. This was the case in a recent experimental programme conducted at NTUA in which several 1:5.5-scale model frames were tested on an earthquake simulator. In order to improve the model reliability, the following measures were taken: strictly obeying the geometric scaling in almost all aspects; using deformed bars as model reinforcement; and using stone-aggregate microconcrete for constructing the models, etc. To evaluate the effectiveness of these measures, a parallel column test programme was conducted in which duplicates of typical columns in the test model frames were prepared, along with those of large sizes following similitude laws. The column specimens were tested under reversals of lateral load. Besides the scale effects, general rules regarding the influences of transverse confinement and axial force on the ductility and strength of columns were also confirmed on the small-scale model columns.  相似文献   

钢筋混凝土框架柱震损程度量化鉴定方法          下载免费PDF全文

曲博闻  张昊宇  毛晨曦  张亮泉 《世界地震工程》2018,34(3):085-93

钢筋混凝土结构震后损伤鉴定中,最常见的方式是鉴定者观察房屋破坏现象,根据经验给出震损等级。该方法直观高效,但对鉴定者的专业经验要求较高,且鉴定结果的主观差异较大。对此以RC框架柱为对象,开展了基于震损现象的震损量化鉴定方法研究:在RC框架柱震损现象量化试验基础上给出基于构件骨架曲线特征阶段的震损分级方法;对7个RC框架柱试件进行了改进Park-Ang损伤指数分析,建立了RC框架柱损伤指数-震损分级-震损现象的对应关系;基于RC框架柱的试验结果及典型震害编制了RC框架柱震损图集,并给出了使用图集进行框架柱震损鉴定的流程及方法。使用该方法对2个实际震害中的RC框架柱进行了震损鉴定,可为更加客观以及准确地开展钢筋混凝土结构的震损鉴定提供参考。  相似文献   

Finite element analysis of the seismic response of ancient columns     

Konstantinos Papadopoulos  Elizabeth Vintzileou  Ioannis N. Psycharis 《地震工程与结构动力学》2019,48(13):1432-1450

This paper presents a numerical study of the response to earthquake actions of eight ancient Greek multidrum columns, which were chosen as representative of a broad spectrum of the ancient columns preserved to date. The study was conducted using the FE software Abaqus, in three steps. At first, the software efficiency to predict the rocking response of dry-stone structures was verified. Afterwards, various numerical models of one typical ancient multidrum column were seismically excited. Records of four real earthquakes differing in frequency content were used for the excitation of the models. Each column model was different from the others at least in one geometric or modeling parameter. Although the examined parameters affected the numerical results, their variation did not alter significantly the overall behavior of the column. In the last step of the study, numerical models of eight columns were seismically excited using four seismic records. In these analyses, among the simulation approaches tested in the second step, the simpler one was adopted. On the basis of the numerical results, conclusions were drawn regarding the seismic resistance of the columns and its correlation with the dynamic characteristics of the columns (size, slenderness, and frequency parameter) and with the basic intensity measures and frequency content indicator of the seismic motions (PHA, PHV, PHD, and T_g). Thus, criteria of seismic collapse for the multidrum columns are proposed, which can be used for the approximate assessment of the seismic vulnerability of free-standing ancient columns, provided that the columns are in good preservation state.  相似文献   

BEYOND FAILURE IN GRANULAR MATERIALS     

Wei Wu  Andrzej Niemunis 《国际地质力学数值与分析法杂志》1997,21(3):153-174

Recent investigations on the hypoplastic constitutive model for granular materials show that the failure surface can be surpassed by some stress paths. This is contradictory to the conventional definition of failure surface in plasticity, according to which the stress is allowed to move on the failure surface but never across it. In the present paper, the interrelations among the different constitutive models are discussed with special reference to failure and stability. For the hypoplastic constitutive equation, the accessible stress states and the stable stress states are found to be enclosed by a bound surface and a stability surface in the stress space, respectively. Theoretical findings about the bound surface and the stability surface are verified qualitatively by presenting results of triaxial tests on dry sand. © 1997 by John Wiley & Sons, Ltd.  相似文献   

A numerical representation of fracturing granular materials     

D. Robertson  M. D. Bolton  G. R. McDowell 《国际地质力学数值与分析法杂志》1997,21(12):825-843

This paper describes the computer algorithms used in a numerical simulation of the compression of an aggregate of crushable grains. It has been used in a model for the evolution of a granular medium under one-dimensional compression, in which the probability of fracture for individual particles is a function of applied stress, particle-size and co-ordination number. The information relating to the particles is represented in a compact way on the computer which allows the number of particles produced to become sufficiently large for satisfactory comparisons to be made with experimental data and which allows information, such as the positions and sizes of the particles, to be easily extracted. An algorithm based on the representation is used to locate neighbouring particles in a way which does not deteriorate unacceptably in terms of speed as the number of particles increases. © 1997 by John Wiley & Sons, Ltd.  相似文献