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1.
Brendon A. Bradley Rajesh P. Dhakal Misko Cubrinovski John B. Mander Greg A. MacRae 《地震工程与结构动力学》2007,36(14):2211-2225
An improved seismic hazard model for use in performance‐based earthquake engineering is presented. The model is an improved approximation from the so‐called ‘power law’ model, which is linear in log–log space. The mathematics of the model and uncertainty incorporation is briefly discussed. Various means of fitting the approximation to hazard data derived from probabilistic seismic hazard analysis are discussed, including the limitations of the model. Based on these ‘exact’ hazard data for major centres in New Zealand, the parameters for the proposed model are calibrated. To illustrate the significance of the proposed model, a performance‐based assessment is conducted on a typical bridge, via probabilistic seismic demand analysis. The new hazard model is compared to the current power law relationship to illustrate its effects on the risk assessment. The propagation of epistemic uncertainty in the seismic hazard is also considered. To allow further use of the model in conceptual calculations, a semi‐analytical method is proposed to calculate the demand hazard in closed form. For the case study shown, the resulting semi‐analytical closed form solution is shown to be significantly more accurate than the analytical closed‐form solution using the power law hazard model, capturing the ‘exact’ numerical integration solution to within 7% accuracy over the entire range of exceedance rate. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
2.
Water losses risk assessment: an example from Carpathian karst 总被引：1，自引：1，他引：0
The multipurpose dam and reservoir “Bogovina” in the Crni Timok valley is one of several projects that have been initiated
to improve water availability in Serbia. The site and height of the dam were initially proposed without consideration of risk
factors such as water leakage or stability of the banks. Later, complex hydrogeological and speleological surveys and tests
identified the potential of significant water losses from the reservoir area connected mainly to the karstic aquifer, and
the nearby Bogovina cave system. The analyses show that once the reservoir is filled up, groundwater flow currently oriented
towards the future reservoir would saturate the upper part of the karstified rocks, reactivate currently unsaturated pathways
and form a reverse discharge outside of the reservoir area. In response to these findings, the dam design and technical details
have been adapted accordingly: the dam height has been reduced by 9 m, and it is proposed that grouting and consolidation
work be conducted both at the foundation of the dam and extensively on the embankments. It was concluded that although the
proposed remedial measures cannot guarantee reservoir tightness, they can reduce the risk of large-scale leaking. 相似文献
3.
Brendon A. Bradley Misko CubrinovskiRajesh P. Dhakal Gregory A. MacRae 《Soil Dynamics and Earthquake Engineering》2009
In this study the efficacy of various ground motion intensity measures for the seismic response of pile foundations embedded in liquefiable and non-liquefiable soils is investigated. A soil-pile-structure model consisting of a two-layer soil deposit with a single pile and a single degree-of-freedom superstructure is used in a parametric study to determine the salient features of the seismic response of the soil-pile-structure system. A suite of ground motion records scaled to various levels of intensity are used to investigate the full range of pile behaviour, from elastic response to failure. Various intensity measures are used to inspect their efficiency in predicting the seismic demand on the pile foundation for a given level of ground motion intensity. It is found that velocity-based intensity measures are the most efficient in predicting the pile response, which is measured in terms of maximum curvature or pile-head displacement. In particular, velocity spectrum intensity (VSI), which represents the integral of the pseudo-velocity spectrum over a wide period range, is found to be the most efficient intensity measure in predicting the seismic demands on the pile foundation. VSI is also found to be a sufficient intensity measure with respect to earthquake magnitude, source-to-site distance, and epsilon, and has a good predictability, thus making it a prime candidate for use in seismic response analysis of pile foundations. 相似文献
4.
Hydrogeological characteristics of some deep siphonal springs in Serbia and Montenegro karst 总被引：1，自引：0，他引：1
Saša Milanovic 《Environmental Geology》2007,51(5):755-759
In terms of hydrogeological, engineering-geological, and hydrotechnical tapping in karst in relation to ground waters, karst
channels, springs and ponors, speleodiving is the only research method which enables direct observation, studying and exact
geological mapping of karst channels and caverns. Data collected during speleodiving research contribute considerably to the
analysis of karst evolution process in the given region, which is very important in evaluating the depth of karstification
and determining the main direction of the groundwater flow. In the past 30 years in Serbia and Montenegro, speleodivers have
investigated over 40 siphonal springs, active cave channels and ponors, of which more than 20 are proof of deep siphonal circulation
in karstic aquifers. The karstic springs are the most interesting phenomenon from a hydrogeological view point, and their
investigations need particular attention. Most of significant karstic springs are on the rims of erosion basins—perimeters
of karst poljes, river valleys, sea coasts and contact areas between karst aquifers and hydrogeological barriers. General
characteristics of the spring regime are the direct correlation between precipitation and spring discharge. Moreover, the
hydrogeological regime of these springs also depends on the size of the catchment area, karstic aquifer retardation capacity,
total porosity, as well as lithological and structural characteristics. 相似文献
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Masoud Moghaddasi Misko Cubrinovski J. Geoff Chase Stefano Pampanin Athol Carr 《地震工程与结构动力学》2011,40(2):135-154
Complex seismic behaviour of soil–foundation–structure (SFS) systems together with uncertainties in system parameters and variability in earthquake ground motions result in a significant debate over the effects of soil–foundation–structure interaction (SFSI) on structural response. The aim of this study is to evaluate the influence of foundation flexibility on the structural seismic response by considering the variability in the system and uncertainties in the ground motion characteristics through comprehensive numerical simulations. An established rheological soil‐shallow foundation–structure model with equivalent linear soil behaviour and nonlinear behaviour of the superstructure has been used. A large number of models incorporating wide range of soil, foundation and structural parameters were generated using a robust Monte‐Carlo simulation. In total, 4.08 million time‐history analyses were performed over the adopted models using an ensemble of 40 earthquake ground motions as seismic input. The results of the analyses are used to rigorously quantify the effects of foundation flexibility on the structural distortion and total displacement of the superstructure through comparisons between the responses of SFS models and corresponding fixed‐base (FB) models. The effects of predominant period of the FB system, linear vs nonlinear modelling of the superstructure, type of nonlinear model used and key system parameters are quantified in terms of different probability levels for SFSI effects to cause an increase in the structural response and the level of amplification of the response in such cases. The results clearly illustrate the risk of underestimating the structural response associated with simplified approaches in which SFSI and nonlinear effects are ignored. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
8.
Brendon A. Bradley Rajesh P. Dhakal Gregory A. MacRae Misko Cubrinovski 《地震工程与结构动力学》2010,39(6):591-613
A companion paper has investigated the effects of intensity measure (IM) selection in the prediction of spatially distributed response in a multi‐degree‐of‐freedom structure. This paper extends from structural response prediction to performance assessment metrics such as probability of structural collapse; probability of exceeding a specified level of demand or direct repair cost; and the distribution of direct repair loss for a given level of ground motion. In addition, a method is proposed to account for the effect of varying seismological properties of ground motions on seismic demand that does not require different ground motion records to be used for each intensity level. Results illustrate that the conventional IM, spectral displacement at the first mode, Sde(T1), produces higher risk estimates than alternative velocity‐based IM's, namely spectrum intensity, SI, and peak ground velocity, PGV, because of its high uncertainty in ground motion prediction and poor efficiency in predicting peak acceleration demands. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
9.
Brendon A. Bradley Misko Cubrinovski Rajesh P. Dhakal Gregory A. MacRae 《Soil Dynamics and Earthquake Engineering》2010,30(5):395-411
This paper presents the probabilistic seismic performance and loss assessment of an actual bridge–foundation–soil system, the Fitzgerald Avenue twin bridges in Christchurch, New Zealand. A two-dimensional finite element model of the longitudinal direction of the system is modelled using advanced soil and structural constitutive models. Ground motions at multiple levels of intensity are selected based on the seismic hazard deaggregation at the site. Based on rigorous examination of several deterministic analyses, engineering demand parameters (EDP's), which capture the global and local demand, and consequent damage to the bridge and foundation are determined. A probabilistic seismic loss assessment of the structure considering both direct repair and loss of functionality consequences was performed to holistically assess the seismic risk of the system.It was found that the non-horizontal stratification of the soils, liquefaction, and soil–structure interaction had pronounced effects on the seismic demand distribution of the bridge components, of which the north abutment piles and central pier were critical in the systems seismic performance. The consequences due to loss of functionality of the bridge during repair were significantly larger than the direct repair costs, with over a 2% in 50 year probability of the total loss exceeding twice the book-value of the structure. 相似文献
10.
Brendon A. Bradley Misko CubrinovskiJennifer J.M. Haskell 《Soil Dynamics and Earthquake Engineering》2011
This paper presents the development, implementation, and application of a probabilistic framework for the pseudo-static analysis of pile foundations in liquefied and lateral spreading soils. The framework allows for rigorous consideration and propagation of the large uncertainties regarding quantification of seismic loads and soil–pile interaction relationships, which exist in the pseudo-static method. Building upon previous relationships proposed by others, the key features of the presented framework are outlined. In particular, the uncertainty estimation of the induced lateral soil displacements; superstructure inertia loads; and stiffness and strength of the liquefied soils are discussed in detail. The results of applying the pseudo-static method to a case study bridge structure are compared to that obtained using a rigorous seismic effective stress analysis within a similar framework. It is illustrated that the consideration of uncertainties in the pseudo-static framework provides enhanced communication of the foundation's seismic performance to end-users, and that the pseudo-static method provides seismic performance prediction consistent with that obtained using advanced seismic effective-stress analyses. 相似文献