Asymmetric one‐storey elastic systems with non‐linear viscous and viscoelastic dampers: Simplified analysis and supplemental damping system design     

Wen‐Hsiung Lin  Anil K. Chopra 《地震工程与结构动力学》2003,32(4):579-596

Investigated is the accuracy in estimating the response of asymmetric one‐storey systems with non‐linear viscoelastic (VE) dampers by analysing the corresponding linear viscous system wherein all non‐linear VE dampers are replaced by their energy‐equivalent linear viscous dampers. The response of the corresponding linear viscous system is determined by response history analysis (RHA) and by response spectrum analysis (RSA) extended for non‐classically damped systems. The flexible and stiff edge deformations and plan rotation of the corresponding linear viscous system determined by the extended RSA procedure is shown to be sufficiently accurate for design applications with errors generally between 10 and 20%. Although similar accuracy is also shown for the ‘pseudo‐velocity’ of non‐linear VE dampers, the peak force of the non‐linear VE damper cannot be estimated directly from the peak damper force of the corresponding linear viscous system. A simple correction for damper force is proposed and shown to be accurate (with errors not exceeding 15%). For practical applications, an iterative linear analysis procedure is developed for determining the amplitude‐ and frequency‐dependent supplemental damping properties of the corresponding linear viscous system and for estimating the response of asymmetric one‐storey systems with non‐linear VE dampers from the earthquake design (or response) spectrum. Finally, a procedure is developed for designing non‐linear supplemental damping systems that satisfy given design criteria for a given design spectrum. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Inelastic displacement ratios for evaluation of existing structures     

Jorge Ruiz‐García  Eduardo Miranda 《地震工程与结构动力学》2003,32(8):1237-1258

Results of a detailed statistical study of constant relative strength inelastic displacement ratios to estimate maximum lateral inelastic displacement demands on existing structures from maximum lateral elastic displacement demands are presented. These ratios were computed for single‐degree‐of‐freedom systems with different levels of lateral strength normalized to the strength required to remain elastic when subjected to a relatively large ensemble of recorded earthquake ground motions. Three groups of soil conditions with shear wave velocities higher than 180m/s are considered. The influence of period of vibration, level of lateral yielding strength, site conditions, earthquake magnitude, distance to the source, and strain‐hardening ratio are evaluated and discussed. Mean inelastic displacement ratios and those associated with various percentiles are presented. A special emphasis is given to the dispersion of these ratios. It is concluded that distance to the source has a negligible influence on constant relative strength inelastic displacement ratios. However, for periods smaller than 1s earthquake magnitude and soil conditions have a moderate influence on these ratios. Strain hardening decreases maximum inelastic displacement at a fairly constant rate depending on the level of relative strength for periods of vibration longer than about 1.0s while it decreases maximum inelastic displacement non‐linearly as the period of vibration shortens and as the relative‐strength ratio increases for periods of vibration shorter than 1.0s. Finally, results from non‐linear regression analyses are presented that provide a simplified expression to be used to approximate mean inelastic displacement ratios during the evaluation of existing structures built on firm sites. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Landslide susceptibility analysis using GIS and artificial neural network     

Saro Lee  Joo‐Hyung Ryu  Kyungduck Min  Joong‐Sun Won 《地球表面变化过程与地形》2003,28(12):1361-1376

The purpose of this study is to develop landslide susceptibility analysis techniques using an arti?cial neural network and to apply the newly developed techniques to the study area of Yongin in Korea. Landslide locations were identi?ed in the study area from interpretation of aerial photographs, ?eld survey data, and a spatial database of the topography, soil type and timber cover. The landslide‐related factors (slope, curvature, soil texture, soil drainage, soil effective thickness, timber age, and timber diameter) were extracted from the spatial database. Using those factors, landslide susceptibility was analysed by arti?cial neural network methods. The landslide susceptibility index was calculated by the back‐propagation method, which is a type of arti?cial neural network method, and the susceptibility map was made with a geographic information system (GIS) program. The results of the landslide susceptibility analysis were veri?ed using landslide location data. The validation results showed satisfactory agreement between the susceptibility map and the existing data on landslide location. A GIS was used to ef?ciently analyse the vast amount of data, and an arti?cial neural network to be an effective tool to maintain precision and accuracy. The results can be used to reduce hazards associated with landslides and to plan land use and construction. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

A procedure for evaluating seismic energy demand of framed structures     

Chung‐Che Chou  Chia‐Ming Uang 《地震工程与结构动力学》2003,32(2):229-244

Energy serves as an alternative index to response quantities like force or displacement to include the duration‐related seismic damage effect. A procedure to evaluate the absorbed energy in a multistorey frame from energy spectra was developed. For low‐ to medium‐rise frames, it required a static pushover analysis of the structure to determine the modal yield force and ductility factor of an equivalent single‐degree‐of‐freedom system for the first two modes. The energy spectra were then used to determine the energy contribution of each mode. A procedure was also developed to distribute the energy along the frame height based on energy shapes. This study showed that the second‐mode response in some cases needs to be considered to reflect the energy (or damage) concentration in the upper floors. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

System identification of the Vincent Thomas suspension bridge using earthquake records     

Andrew W. Smyth  Jin‐Song Pei  Sami F. Masri 《地震工程与结构动力学》2003,32(3):339-367

The Vincent Thomas Bridge in the Los Angeles metropolitan area, is a critical artery for commercial traffic flow in and out of the Los Angeles Harbor, and is at risk in the seismically active Southern California region, particularly because it straddles the Palos Verdes fault zone. A combination of linear and non‐linear system identification techniques is employed to obtain a complete reduced‐order, multi‐input–multi‐output (MIMO) dynamic model of the Vincent Thomas Bridge based on the dynamic response of the structure to the 1987 Whittier and 1994 Northridge earthquakes. Starting with the available acceleration measurements (which consists of 15 accelerometers on the bridge structure and 10 accelerometers at various locations on its base), an efficient least‐squares‐based time‐domain identification procedure is applied to the data set to develop a reduced‐order, equivalent linear, multi‐degree‐of‐freedom model. Although not the main focus of this study, the linear system identification method is also combined with a non‐parametric identification technique, to generate a reduced‐order non‐linear mathematical model suitable for use in subsequent studies to predict, with good fidelity, the total response of the bridge under arbitrary dynamic environments. Results of this study yield measurements of the equivalent linear modal properties (frequencies, mode shapes and non‐proportional damping) as well as quantitative measures of the extent and nature of non‐linear interaction forces arising from strong ground shaking. It is shown that, for the particular subset of observations used in the identification procedure, the apparent non‐linearities in the system restoring forces are quite significant, and they contribute substantially to the improved fidelity of the model. Also shown is the potential of the identification technique under discussion to detect slight changes in the structure's influence coefficients, which may be indicators of damage and degradation in the structure being monitored. Difficulties associated with accurately estimating damping for lightly damped long‐span structures from their earthquake response are discussed. The technical issues raised in this paper indicate the need for added spatial resolution in sensor instrumentation to obtain identified mathematical models of structural systems with the broadest range of validity. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Temperatures of Granulite-facies Metamorphism: Constraints from Experimental Phase Equilibria and Thermobarometry Corrected for Retrograde Exchange   总被引：17，自引：7，他引：17  

PATTISON  DAVID R. M.; CHACKO  THOMAS; FARQUHAR  JAMES; MCFARLANE  CHRISTOPHER R. M. 《Journal of Petrology》2003,44(5):867-900

This study assesses temperatures of formation of common granulitesby combining experimental constraints on the P–T stabilityof granulite-facies mineral associations with a garnet–orthopyroxene(Grt–Opx) thermobarometry scheme based on Al-solubilityin Opx, corrected for late Fe–Mg exchange. We appliedthis scheme to 414 granulites of mafic, intermediate and aluminousbulk compositions. Our findings suggest that granulites aremuch hotter than traditionally assumed and that the P–Tconditions of the amphibolite–granulite transition portrayedin current petrology textbooks are significant underestimatesby over 100°C. For aluminous and intermediate granulites,mean corrected temperatures based on our method are 890 ±17 and 841 ± 11°C, respectively (uncertainties reportedas 95% confidence limits on the mean), consistent with minimumtemperatures for orthopyroxene production by fluid-absent partialmelting in these bulk compositions. In contrast, mean temperaturesbased on Grt–Opx Fe–Mg exchange equilibria, usingthe same thermodynamic data, are 732 ± 22 and 723 ±11°C, respectively, well below the minimum temperaturesfor Opx stability. For mafic granulites, the mean correctedtemperature using our method is 816 ± 12°C, similarto the mean temperature of 793 ± 13°C from Fe–Mgexchange. Reasons for the differences between the mafic granulitesand aluminous–intermediate granulites are unclear butmay be due to the lower Al concentrations in Opx in the maficrocks and possible deficiencies in the thermodynamic modellingof these low concentrations. We discuss a number of well-knowngranulite terrains in the context of our findings, includingthe Adirondacks, the Acadian granulites of New England, theincipient charnockites of southern India and Sri Lanka, andthe Kerala Khondalite Belt. Our findings carry implicationsfor thermotectonic models of granulite formation. A computerprogram to perform our thermobarometry calculations, RCLC, isavailable from the Journal of Petrology website at http://www.petrology.oupjournals.orgor from the authors at http://www.geo.ucalgary.ca/~pattison/drm_pattison-rclc.htm. KEY WORDS: granulite-facies metamorphism; thermobarometry; garnet; orthopyroxene  相似文献   

TransCom 3 CO₂ inversion intercomparison: 1. Annual mean control results and sensitivity to transport and prior flux information     

KEVIN ROBERT GURNEY  RACHEL M. LAW  A. SCOTT DENNING  PETER J. RAYNER  DAVID BAKER  PHILIPPE BOUSQUET  LORI BRUHWILER  YU-HAN CHEN  PHILIPPE CIAIS  SONGMIAO FAN  INEZ Y. FUNG  MANUEL GLOOR  MARTIN HEIMANN  KAZ HIGUCHI  JASMIN JOHN  EVA KOWALCZYK  TAKASHI MAKI  SHAMIL MAKSYUTOV  PHILIPPE PEYLIN  MICHAEL PRATHER  BERNARD C. PAK  JORGE SARMIENTO  SHOICHI TAGUCHI  TARO TAKAHASHI  CHIU-WAI YUEN 《Tellus. Series B, Chemical and physical meteorology》2003,55(2):555-579

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Spillover models for axial rivers in regions of continental extension: the Rio Mimbres and Rio Grande in the southern Rio Grande rift, USA     

GREG H. MACK  DAVID W. LOVE†  WILLIAM R. SEAGER 《Sedimentology》1997,44(4):637-652

The Pliocene-early Pleistocene history of the ancestral Rio Grande and Quaternary history of the Rio Mimbres in the southern Rio Grande rift, New Mexico, illustrate how axial rivers may alternately spill into and subsequently abandon extensional basins. Three types of spillover basins are recognized, based on the angle at which the axial river enters the basin and whether it descends the hanging wall dip slope or footwall scarp to reach the basin floor. In the Mimbres basin type, the axial river enters and flows through the spillover basin nearly parallel to the footwall scarp, resulting in a narrow belt of basin-axis-parallel channel sand bodies located near the footwall scarp. In contrast, an axial river may enter a spillover basin at a high angle to its axis, either descending the hanging wall dip slope (Columbus basin type) or footwall scarp (Tularosa basin type), and construct a fluvial fan, consisting of radiating distributary channels orientated nearly perpendicular to the basin axis. Faulting exerts significant control on river spillover by creating the topographic gaps through which the axial river moves and by terminating spillover by subsequently uplifting or tilting the gap. Spillover may also be autocyclic in origin as a result of aggradation to the level of a pre-existing gap, headward erosion creating and/or intersecting a gap, or simple river avulsion upstream of a gap. Predicting facies architecture in the three types of spillover basins is critical to successful subsurface exploration for hydrocarbon reservoirs, groundwater aquifers or placer mineral deposits.  相似文献   

CAPTAIN COOK AND HOW WE UNDERSTAND HIM     

DAVID R. STODDART 《Geographical review》1997,87(4):537-541

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Rapid Variscan exhumation and the role of magma in core complex formation: southern Brittany metamorphic belt, France   总被引：6，自引：0，他引：6  

MICHAEL BROWN  R. DAVID DALLMEYER 《Journal of Metamorphic Geology》1996,14(3):361-379

ABSTRACT The high-grade migmatitic core to the southern Brittany metamorphic belt has mineralogical and textural features that suggest high-temperature decompression. The chronology of this decompression and subsequent cooling history have been constrained with ⁴⁰Ar/³⁹ Ar ages determined for multigrain concentrates of hornblende and muscovite prepared from amphibolite and late-orogenic granite sheets within the migmatitic core, and from amphibolite of the structurally overlying unit. Three hornblende concentrates yield plateau isotope correlation ages of c. 303–298 Ma. Two muscovite concentrates record well-defined plateau ages of c. 306–305 Ma. These ages are geologically significant and date the last cooling through temperatures required for intracrystalline retention of radiogenic argon. The concordancy of the hornblende and muscovite ages suggest rapid post-metamorphic cooling. Extant geochronology and the new ⁴⁰Ar/³⁹Ar data suggest a minimum time-integrated average cooling rate between c. 725 °C and c. 125 °C of c. 14 ± 4°C Ma^-1, although below 600 °C the data permit an infinitely fast rate of cooling. Mineral assemblages and reaction textures in diatexite migmatites suggest c. 4 kbar decompression at 800–750 °C. This must have pre-dated the rapid cooling. Emplacement of two-mica granites into the metamorphic belt occurred between 345 and 300 Ma. The youngest plutons were emplaced synkinematically along shallow-dipping normal faults interpreted to be reactivated Eo-Variscan thrusts. A penetrative, west-plunging stretching lineation developed in these granites suggests that extension was orogen-parallel. Extension was probably related to regional uplift and gravitational collapse of thermally weakened crust during constrictional (escape) tectonics in this narrow part of the Variscan orogen. This followed slab breakoff during the terminal stages of convergence between Gondwana and Laurasia; detachment may have been consequent upon a change in kinematics leading to dextral displacement within the orogen. Dextral ductile strike-slip displacement was concentrated in granites emplaced synkinematically along the South Armorican Shear Zone. Rapid cooling is interpreted to have resulted from tectonic unroofing with emplacement of granite along decollement surfaces. The high-grade migmatitic core of the southern Brittany metamorphic belt represents a type of metamorphic core complex formed during orogen-parallel extensional unroofing and regional-scale ductile flow.  相似文献