Pushover analysis of base-isolated steel–concrete composite structures under near-fault excitations     

C.P. Providakis   《Soil Dynamics and Earthquake Engineering》2008,28(4):293-304

In the present study, the seismic behavior of steel–concrete composite structures isolated by base-isolation devices under near-fault earthquake excitations is numerically investigated. The seismic analysis is performed by means of the static non-linear (pushover) analysis procedure conducted on two five-storey three-dimensional (3-D) buildings with steel columns and steel–concrete composite slabs and beams. The present 3-D building examples are assumed to be located at a near-fault area in order to take into account the effect of strong ground motion on the isolation devices. The results of this study allowed the verification of the adequacy of the attachment isolation system as well as the comparison of the behavior of the seismic-protected building with or without bracings to the unprotected buildings with or without bracings, showing the benefits of the application of the isolation devices, the limitations and the characteristics of their performance.  相似文献   

A note on strength-reduction factors for design of structures near earthquake faults   总被引：1，自引：0，他引：1  

Reza S. Jalali  Mihailo D. Trifunac   《Soil Dynamics and Earthquake Engineering》2008,28(3):212-222

Strength-reduction factors are analyzed for simplified near-fault, fault-normal and fault-parallel strong-motion displacements. It is shown that the common design rules for selection of the strength-reduction factors are conservative and properly describe the reduction amplitudes near faults of strong earthquakes, for fault-normal pulses. However, for fault-parallel displacements, the same reduction factors are not conservative and should be changed. It is recommended that for design close to active faults, the strength-reduction factors for all components of motion should be constant for all periods and equal to (2μ−1)^1/2, where μ is ductility.  相似文献   

Earthquake damage detection in the Imperial County Services Building III: Analysis of wave travel times via impulse response functions   总被引：1，自引：0，他引：1  

Maria I. Todorovska  Mihailo D. Trifunac   《Soil Dynamics and Earthquake Engineering》2008,28(5):387-404

The majority of structural health monitoring methods are based on detecting changes in the modal properties, which are global characteristics of the structure, and are not sensitive to local damage. Wave travel times between selected sections of a structure, on the other hand, are local characteristics, and are potentially more sensitive to local damage. In this paper, a structural health monitoring method based on changes in wave travel times is explored using strong motion data from the Imperial Valley Earthquake of 1979 recorded in the former Imperial County Services (ICS) Building, severely damaged by this earthquake. Wave travel times are measured from impulse response functions computed from the recorded horizontal seismic response in three time windows—before, during, and after the largest amplitude response, as determined from previous studies of this building, based on analysis of novelties in the recorded response. The results suggest initial spatial distribution of stiffness consistent with the design characteristics, and reduction of stiffness following the major damage consistent with the spatial distribution of the observed damage. The travel times were also used to estimate the fundamental fixed-base frequency of the structure f₁ (assuming the building deformed as a shear beam), and its changes during this earthquake. These estimates are consistent with previous estimates of the soil–structure system frequency, f_sys, during the earthquakes (f₁<f_sys as expected from soil–structure interaction studies), and with other estimates of frequency (f₁ from ETABS models, and f_sys from ambient vibration tests, and “instantaneous” f₁ from high-frequency pulse propagation).  相似文献   

Tunnelling in soils – ground movements, and damage to buildings in Workington, UK     

A.R. Selby 《Geotechnical and Geological Engineering》1999,17(3-4):351-371

Tunnelling through soils results in ground loss, causing surface settlements and transverse movements. Where the tunnel drive passes below an existing structure, it is important to estimate the effects upon the structure. However, the free ground deformations should not simply be imposed upon a structure, because the structure contributes to stiffening of the ground. A computational soil-structure interaction analysis is required, to otain detailed stress–deformation response. First, linear finite element and Lagrangian finite difference methods are used to estimate ground movements due to a tunnel in free ground, and the results are compared with values based on empirical equations. The two linear methods and an additional hybrid FE method are then used to assess with soil-structure interaction; two cases of a typical short wall and a long wall lying across the route of tunnels of different depths. The results support the validity of the hybrid method which is used to estimate interactive ground settlements for comparison with a reported case of tunnelling below a building in central London. A more detailed case study is then undertaken to assess building damage caused by gross settlements during tunnelling in mixed soils, at a site in Workington, west Cumbria. A survey allowed estimation of free ground movements. Analysis by the hybrid method on the soils plus uncracked structures indicated intolerable horizontal stresses. Re-analysis with major cracks introduced into the structures resulted in close agreement between measured and computed settlements.  相似文献   

Ice Induced Low Temperature Fatigue Crack Propagation in Offshore Structural Steel A131     

DUAN Menglan  GAO Zhaojie  LIU Chuntu Senior Engineer  China Classification Society  Beijing  China. Research Professor 《中国海洋工程》1998,(3)

To investigate the low temperature fatigue crack propagation behavior of offshore structuralsteel A131 under random ice loading,three ice failure modes that are commonly present in the Bohai Gulfare simulated according to the vibration stress responses induced by real ice loading.The test data are pro-cessed by a universal software FCPUSL developed on the basis of the theory of fatigue crack propagationand statistics.The fundamental parameter controlling the fatigue crack propagation induced by randomice loading is determined to be the amplitude root mean square stress intensity factor K_(arm).The test resultsare presented on the crack propagation diagram where the crack growth rate da/dN is described as thefunction of K_(arm).It is evident that the ice failure modes have great influence on the fatigue crack propaga-tion behavior of the steel in ice-induced vibration.However,some of the experimental phenomena and testresults are hard to be physically explained at present.The work in this paper is an init  相似文献   

Optimum Environmental Load Design Criterion for Marine Structures Based on Investment and Benefit Analysis     

ZHANG Shuhua  YU Yifa  LI Benxia Associate Professor  Ocean University of Qingdao  Qingdao  P. R. China. Master  Ocean University of Qingdao  Qingdao  P. R. China. 《中国海洋工程》1998,(2)

Marine structures operating in natural ocean environment are subjected to various stochasticloads.For design of the marine structures,the most important task is to determine environmental load de-sign criterion.This paper presents a method to determine the optimum environmental load design criteri-on for marine structures.This method is based on the investment and benefit analysis and it can reach thedesign purpose of decreasing total costs during the service life of the structures and increasing economicbenefits.  相似文献   

Hybrid three-dimensional finite-difference and finite-element analysis of seismic wave induced fluid–structure interaction of a vertical cylinder     

Bang-Fuh Chen 《Ocean Engineering》1998,25(8):639-656

The two-dimensional finite-difference scheme has been extended to three dimensions to solve nonlinear hydrodynamic pressures and structural responses of a deformable, vertical and circular surface-piercing offshore cylinder during earthquakes. A complete three-dimensional analysis has been made with both the three-dimensional equations of motion and the simultaneous action of three components of ground acceleration included in the analysis. Not only the magnitude but also the direction of the acting ground motion can be varied with time. The dynamic response of a cylinder is approximated by the displacements in the fundamental modes of vibration. A comparison of the dynamic displacement of the cylinder with and without surrounding sea water has been made. The flexibility of the offshore cylinder can significantly increase the hydrodynamic pressures acting on cylinder faces, that is, the fluid-structure interaction is necessary in offshore cylinder analysis. Although the hydrodynamic pressure induced by the vertical ground acceleration of the El Centro 1979 earthquake is significant, the calculated structural dynamic response of a cylinder is very small and the corresponding resultant hydrodynamic force is almost nil. The hydrodynamic force induced by two-horizontal ground acceleration is about the same as that by three simultaneous components of ground acceleration. For a solid and stubbier circular cylinder, the vertical component of ground acceleration may be neglected.  相似文献   

Reef margin collapse, gully formation and filling within the Permian Capitan Reef: Carlsbad Caverns, New Mexico, USA     

Gill M. Harwood  & Alan C. Kendall 《Sedimentology》1999,46(3):443-461

An area of reef margin collapse, gully formation and gully fill sedimentation has been identified and mapped within Left Hand Tunnel, Carlsbad Caverns. It demonstrates that the Capitan Reef did not, at all times, form an unbroken border to the Delaware Basin. Geopetally arranged sediments within cavities from sponge–algal framestones of the reef show that the in situ reef today has a 10° basinwards structural dip. Similar dips in adjacent back-reef sediments, previously considered depositional, probably also have a structural origin. Reoriented geopetal structures have also allowed the identification of a 200-m-wide, 25-m-deep gully within the reef, which has been filled by large (some  >15 m), randomly orientated and, in places, overturned blocks and boulders, surrounded by finer reef rubble, breccias and grainstones. Block supply continued throughout gully filling, implying that spalling of reef blocks was a longer term process and was not a by-product of the formation of the gully. Gully initiation was probably the result of a reef front collapse, with a continued instability of the gully bordering reef facies demonstrated by their incipient brecciation and by faults containing synsedimentary fills. Gully filling probably occurred during reef growth, and younger reef has prograded over the gully fill. Blocks contain truncated former aragonite botryoidal cements, indicating early aragonite growth within the in situ reef. In contrast, former high-magnesian calcite rind cements post-date sedimentation within the gully. The morphology of cavern passages is controlled by reef facies variation, with narrower passages cut into the in situ reef and wider passages within the gully fill. Gully fills may also constitute more permeable zones in the subsurface.  相似文献   

山东招-掖金矿带的西延去向探讨   总被引：3，自引：0，他引：3  

朱光 《地质与勘探》1999,35(2):6-9

山东招（远）－掖（县）金矿带所处的胶北隆起带与五河一蚌埠金矿带所处的淮河地块,在中生代以前为处于华北板块南缘的同一构造单元,郯庐断裂中生代大规模左行平移使两者错开,招－掖金矿带与五河－蚌埠金矿带具有类似的基底,矿源层,成矿期,矿床类型,成矿期岩浆活动,控矿构造等。因而,推测五河－蚌埠金矿带是招－掖金矿带在郯庐断裂带以西的延伸。由于淮河地块燕山期岩浆活动和郯庐断裂系的发育较弱于胶北隆起带,估计五河－  相似文献   

Dynamic pressures on inclined cylinders due to freak waves   总被引：1，自引：0，他引：1  

V. Sundar  P. M. Koola  A. U. Schlenkhoff 《Ocean Engineering》1999,26(9):346

The dynamic pressure distribution around a cylinder tilted along and against the principal wave direction is measured. The cylinder was exposed to the action of random waves in the presence and absence of extreme waves. Six inclinations from the vertical plane, three along and three against the wave direction, were considered. The cylinder in upright position was also studied. The variation of dimensionless peak pressure (pressure maximum/average highest one-third wave height, H_1/3) with the relative wave height (maximum wave height/H_1/3) for locations facing the wave and at the rear of the cylinder for different angles of inclinations of the cylinder are reported for the two kinds of waves mentioned earlier. The statistical properties of the different asymmetries in the pressure traces are also discussed.  相似文献