An Integrated Laboratory Method to Measure and Verify Directional Hydraulic Conductivity in Fine‐to‐Medium Sandy Sediments          下载免费PDF全文

Jialiang Cai  Thomas Taute  Enrico Hamann  Michael Schneider 《Ground water》2015,53(1):140-150

The constant‐head permeameter test (CHPT) is widely used in sandy samples as a standard method in the laboratory to investigate hydraulic conductivity (K). However, it neither can be used to consistently determine directional hydraulic conductivity (DHC) nor guarantee the comparability of measured K values of samples with different sizes. Therefore, this paper proposes an integrated laboratory method, called modified CHPT (MCHPT), for the efficient determination and verification of consistent DHC values in fine‐to‐medium sandy sediments, based on a new methodological framework. A precise and standardized procedure for preparing the experimental setup of MCHPT was conducted, based on the integrated experimental setup of CHPT and tracer tests. Moreover, a formula was yielded for the time‐optimized sample saturation control. In comparison with grain size‐based methods, the validity of consistent K_h and K_v values determined by MCHPT was convincing.  相似文献   

Shaking table testing of an existing masonry building: assessment and improvement of the seismic performance          下载免费PDF全文

Nuno Mendes  Paulo B. Lourenço  Alfredo Campos‐Costa 《地震工程与结构动力学》2014,43(2):247-266

This paper aims to assess and improve the seismic performance of an existing masonry building with flexible floors, representative of a Portuguese building typology—‘gaioleiro’ buildings. The study involved seismic tests and dynamic identification tests of two models (nonstrengthened and strengthened) in the shaking table. Each model was subjected to several seismic tests with increasing amplitude. Before the first test and after each seismic test, the dynamic identification of the model was carried out, aiming at obtaining their seismic vulnerability curves based on a damage indicator obtained from the decrease of the frequencies of the modes. In the strengthened model, steel elements were used to improve the connection between walls and floors, together with ties in the upper stories. The results show that adopted strengthening technique is effective for reducing the seismic vulnerability of ‘gaioleiro’ buildings, namely for improving the out‐of‐plane behavior of the facades. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Seismic sensitivity analysis of the common structural components of Nepalese Pagoda temples     

Manjip Shakya  Humberto Varum  Romeu Vicente  Aníbal Costa 《Bulletin of Earthquake Engineering》2014,12(4):1679-1703

Nepal is located in a highly active tectonic region of the Himalayan belt, one of the most severe earthquake prone areas of the world. Nepal is lying between the Indian and the Eurasian plate, which are moving continuously, resulting in frequent devastating earthquakes. Moreover, different authors state that the accumulated slip deficit (central seismic gap) is likely to produce large earthquakes in the future. Cultural heritage buildings and monuments are, therefore, at risk, and the eventual cultural loss in the consequence of an earthquake is incalculable. Post-seismic surveys of past earthquakes have shown the potential damage that unreinforced masonry structures, particularly Pagoda temples, may suffer in future earthquakes. Most of the Nepalese Pagoda temples, erected during XIV century, are considered non-engineered constructions that follow very simple rules and construction detailing in respect to seismic resistance requirements and, in some cases, without any concern for seismic action. Presently, conservation and restoration of Nepalese temples is one of the major concerns, since they are considered world heritage with universal value. The present paper is devoted to outline particular building characteristics of the UNESCO classified Nepalese Pagoda temples and the common structural fragilities, which may affect their seismic performance. Moreover, based on a parametric sensitivity analysis, structural weaknesses and fragilities of Pagoda temples were identified associated to the local and traditional construction techniques, detailing and common damages.  相似文献   

Modeling the release and transport of <Superscript>90</Superscript>Sr radionuclides from a superficial nuclear storage facility     

Francesco Cadini  Edoardo Tosoni  Enrico Zio 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(2):693-712

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Evolution of earthquake losses in Portuguese residential building stock     

Maria Luísa Sousa  Alfredo Campos Costa 《Bulletin of Earthquake Engineering》2016,14(7):2009-2029

The evolution of the expected earthquake losses in different Portuguese regions was studied in order to determine whether the natural regeneration of buildings could contribute to the mitigation of seismic risk, although the building exposure has increased over time in most analysed regions. To achieve this goal, five inter-related risk indicators were estimated, based on the Portuguese censuses’ surveys of residential buildings and inhabitants obtained in two different moments in time: 2001 and 2011. The FEMA (2008) approach was used to estimate the risk indicators, i.e., the Annualized Economic and Human earthquake Losses, either in absolute terms or normalised by building and population exposure. This study offers a perspective of the seismic risk in the Portuguese mainland, provides a comparison of risk levels between different epochs, and analyses the obtained results in order to compare the risk among Portuguese regions. It is important to mention that the comparison of economic losses based on the building stocks surveyed in 2001 and in 2011 took into account the Portuguese inflation rate in that time interval. The main findings of the study show that the natural regeneration of the residential housing stock contributes to the reduction of the expected seismic economic losses in Portugal, at an average rate of 14 % per 10 years, and to the reduction of the expected annualized human losses to almost one half after 10 years. The results support the conclusion that the natural regeneration of the residential housing stock contributed to the mitigation of the seismic risk in mainland Portugal, in the 10 year period under analysis, even though there was an increase of the building exposure in the region.  相似文献   

Influence of the nonlinear behavior of viscous dampers on the seismic demand hazard of building frames   总被引：1，自引：0，他引：1       下载免费PDF全文

Andrea Dall′Asta  Enrico Tubaldi  Laura Ragni 《地震工程与结构动力学》2016,45(1):149-169

This paper analyzes the influence of damper properties on the probabilistic seismic performance of building frames equipped with viscous dampers. In particular, a probabilistic methodology is employed to evaluate the influence of the damper nonlinearity, measured by the damper exponent, on the performance of structural and nonstructural components of building frames, as described by the response hazard curves of the relevant engineering demand parameters. The performance variations due to changes in the damper nonlinearity level are evaluated and highlighted by considering two realistic design scenarios and by comparing the results of a set of cases involving dampers with different exponents designed to provide the same deterministic performance. By this way, it is possible to evaluate the influence of the nonlinear response and of its dispersion on the demand hazard. It is shown that the damper nonlinearity level strongly affects the seismic performance and different trends are observed for the demand parameters of interest. A comparison with code provisions shows that further investigation is necessary to provide more reliable design formulas accounting for the damping nonlinearity level. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Shaking table testing for masonry infill walls: unreinforced versus reinforced solutions          下载免费PDF全文

Paulo B. Lourenço  João M. Leite  Manuel F. Paulo‐Pereira  A. Campos‐Costa  P. X. Candeias  Nuno Mendes 《地震工程与结构动力学》2016,45(14):2241-2260

Several factors influence the behaviour of infilled frames, which have been a subject of research in the past with moderate success. The new generation of European design standards imposes the need to prevent brittle collapse of the infills and makes the structural engineer accountable for this requirement, yet it fails to provide sufficient information for masonry infills design. Therefore, the present work aims at understanding the seismic behaviour of masonry infill walls within reinforced concrete frames, using both unreinforced and reinforced solutions (bed joint reinforcement and reinforced plaster). For this purpose, three reinforced concrete buildings with different infill solutions were constructed at a scale of 1:1.5, all with the same geometry, and were tested on the shaking table of the National Laboratory for Civil Engineering, Portugal. All solutions performed adequately for the design earthquake, with no visible damage. Still, the experimental tests show that the double‐leaf‐unreinforced infill walls underperformed during a large earthquake, collapsing out of plane by rotating as rigid bodies with multiple configurations. Also the reinforced concrete buildings collapsed, because of the adverse interaction with the infill walls. The infill walls with bed joint reinforcement and reinforced plaster did not collapse out of plane, because of their connection to the concrete frame, which is an essential requirement. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Probabilistic seismic demand model for pounding risk assessment          下载免费PDF全文

Enrico Tubaldi  Fabio Freddi  Michele Barbato 《地震工程与结构动力学》2016,45(11):1743-1758

Earthquake‐induced pounding of adjacent structures can cause severe structural damage, and advanced probabilistic approaches are needed to obtain a reliable estimate of the risk of impact. This study aims to develop an efficient and accurate probabilistic seismic demand model (PSDM) for pounding risk assessment between adjacent buildings, which is suitable for use within modern performance‐based engineering frameworks. In developing a PSDM, different choices can be made regarding the intensity measures (IMs) to be used, the record selection, the analysis technique applied for estimating the system response at increasing IM levels, and the model to be employed for describing the response statistics given the IM. In the present paper, some of these choices are analyzed and evaluated first by performing an extensive parametric study for the adjacent buildings modeled as linear single‐degree‐of‐freedom systems, and successively by considering more complex nonlinear multi‐degree‐of‐freedom building models. An efficient and accurate PSDM is defined using advanced intensity measures and a bilinear regression model for the response samples obtained by cloud analysis. The results of the study demonstrate that the proposed PSDM allows accurate estimates of the risk of pounding to be obtained while limiting the number of simulations required. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

MeMoVolc report on classification and dynamics of volcanic explosive eruptions     

C. Bonadonna  R. Cioni  A. Costa  T. Druitt  J. Phillips  L. Pioli  D. Andronico  A. Harris  S. Scollo  O. Bachmann  G. Bagheri  S. Biass  F. Brogi  K. Cashman  L. Dominguez  T. Dürig  O. Galland  G. Giordano  M. Gudmundsson  M. Hort  A. Höskuldsson  B. Houghton  J.C. Komorowski  U. Küppers  G. Lacanna  J.L. Le Pennec  G. Macedonio  M. Manga  I. Manzella  M. de’ Michieli Vitturi  A. Neri  M. Pistolesi  M. Polacci  M. Ripepe  E. Rossi  B. Scheu  R. Sulpizio  B. Tripoli  S. Valade  G. Valentine  C. Vidal  N. Wallenstein 《Bulletin of Volcanology》2016,78(11):84

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A methodology for the probabilistic assessment of behaviour factors     

Aníbal Costa  Xavier Romão  Carlos Sousa Oliveira 《Bulletin of Earthquake Engineering》2010,8(1):47-64

Given the importance that traditional force-based seismic design still currently exhibits, studies addressing issues related to the definition of the behaviour factor values are considered to be of most interest. A probabilistic methodology is proposed for the calibration of the q-factor relating its value with two fundamental parameters, the displacement ductility capacity measured at a relevant location of the structure and the failure probability P _f . The general foundation of this procedure is based on the probabilistic quantification of the seismic action and, by applying a transformation procedure, of the structural seismic demand in terms of displacement ductility. By recalling well established structural reliability procedures and by making use of nonlinear analysis methods, both static and dynamic, a general probabilistic framework, which is able to relate the ductility capacity, the failure probability P _f and the behaviour factor, is defined. In order to illustrate some of the potentialities of the methodology, an application example is presented, addressing the q-factor assessment for a set of regular and irregular reinforced concrete frame structures, enforcing a given P _f and two different ductility levels.  相似文献