Influence of the construction process and nonstructural components on the modal properties of a five‐story building          下载免费PDF全文

Rodrigo Astroza  Hamed Ebrahimian  Joel P. Conte  José I. Restrepo  Tara C. Hutchinson 《地震工程与结构动力学》2016,45(7):1063-1084

A full‐scale five‐story reinforced concrete building was built and tested on the NEES‐UCSD shake table during the period from May 2011 to May 2012. The purpose of this test program was to study the response of the structure and nonstructural components and systems (NCSs) and their dynamic interaction during seismic base excitation of different intensities. The building specimen was tested first under a base‐isolated condition and then under a fixed‐based condition. As the building was being erected, an accelerometer array was deployed on the specimen to study the evolution of its modal parameters during the construction process and placement of major NCSs. A sequence of dynamic tests, including daily ambient vibration, shock (free vibration) and forced vibration tests (low‐amplitude white noise and seismic base excitations), were performed on the building at different stages of construction. Different state‐of‐the‐art system identification methods, including three output‐only and two input‐output methods, were used to estimate the modal properties of the building. The obtained results allow to investigate in detail the effects of the construction process and NCSs on the dynamic parameters of this building system and to compare the modal properties obtained from different methods, as well as the performance of these methods. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Soil compaction under different management practices in a Croatian vineyard     

Igor Bogunovic  Darija Bilandzija  Zeljko Andabaka  Domagoj Stupic  Jesús Rodrigo Comino  Marija Cacic  Luka Brezinscak  Edi Maletic  Paulo Pereira 《Arabian Journal of Geosciences》2017,10(15):340

The use of machinery in vineyards is increasing soil compaction and erosion. However, there is a lack of information about the impacts of different management practices on soil conditions of vineyards. Therefore, the aim of this study was to assess soil compaction in Croatian vineyards under four different management systems: no-tillage (NT) system, conventional tillage (CT), yearly inversed grass covered (INV-GC) and tillage managed (INV-T) treatments. Four key top-soil (0–20 cm) parameters were assessed in the different land uses: bulk density (BD), penetration resistance (PR), soil water content (SWC) and carbon dioxide (CO₂) fluxes. Tractor traffic increased the BD and PR in all treatments, with exception of CT treatment, as consequence of tillage. SWC showed higher values in INV-GC treatment during the dry period; meanwhile, it was similar during the wet season in every management type. Lower CO₂ fluxes were found in INV-GC and NT than in the CT and INV-T treatments.  相似文献   

Correlations between deep convection and lightning activity on a global scale     

Eldo E. Ávila  Rodrigo E. Bürgesser  Nesvit E. Castellano  Andrew B. Collier  Rosa H. Compagnucci  Arthur R.W. Hughes 《Journal of Atmospheric and Solar》2010,72(14-15):1114-1121

Satellite observations of cloud top temperature and lightning flash distribution are used to examine the relationship between deep convection and lightning activity over the tropical regions of the northern and southern hemispheres. In agreement with previous work, the analysis of the results shows that, in the summer of both hemispheres, the lightning activity in continental deep convective storms is more intense than that in marine deep convective storms by a factor of between 7 and 10. Furthermore, it was observed that on average the daily lightning rate per 1°×1° grid cell for the southern hemisphere (SH) is about 20% greater than that of the northern hemisphere (NH), which can be attributed to a larger fractional cover by deep convective clouds in the SH. By using a set of independent indicators, it is shown that deep convection and lightning activity over land are well correlated (with correlation coefficients of 0.8 and 0.6 for NH and SH, respectively). This suggests the capacity for observations to act as a possible method of monitoring continental deep convective clouds, which play a key role in regulating the Earth’s climate. Since lightning can be monitored easily from ground networks and satellites, it could be a useful tool for validating the performance of model convective schemes and for monitoring changes in climate parameters.  相似文献   

Diseases leading to accelerated decline of reef corals in the largest South Atlantic reef complex (Abrolhos Bank, eastern Brazil)     

Francini-Filho RB  Moura RL  Thompson FL  Reis RM  Kaufman L  Kikuchi RK  Leão ZM 《Marine pollution bulletin》2008,56(5):1008-1014

Although reef corals worldwide have sustained epizootics in recent years, no coral diseases have been observed in the southwestern Atlantic Ocean until now. Here we present an overview of the main types of diseases and their incidence in the largest and richest coral reefs in the South Atlantic (Abrolhos Bank, eastern Brazil). Qualitative observations since the 1980s and regular monitoring since 2001 indicate that coral diseases intensified only recently (2005–2007). Based on estimates of disease prevalence and progression rate, as well as on the growth rate of a major reef-building coral species (the Brazilian-endemic Mussismilia braziliensis), we predict that eastern Brazilian reefs will suffer a massive coral cover decline in the next 50 years, and that M. braziliensis will be nearly extinct in less than a century if the current rate of mortality due to disease is not reversed.  相似文献   

Groundwater Level Prediction/Forecasting and Assessment of Uncertainty Using SGS and ARIMA Models: A Case Study in the Bauru Aquifer System (Brazil)     

Takafuji  Eduardo Henrique de Moraes  Rocha  Marcelo Monteiro da  Manzione  Rodrigo Lilla 《Natural Resources Research》2019,28(2):487-503

Natural Resources Research - Best water management practices should involve the prediction of the availability of groundwater resources. To predict/forecast and consequently manage these water...  相似文献   

Stretch-free generalized normal moveout correction     

Jorge H. Faccipieri  Tiago A. Coimbra  Rodrigo Bloot 《Geophysical Prospecting》2019,67(1):52-68

The effective application of normal moveout correction processes mainly depends on four factors: the chosen traveltime approximation, the stretching associated with the given traveltime, crossing events and phase changes, the last two being inherent to the seismic data. In this context, we conduct a quantitative analysis on stretching considering a general traveltime expression depending on half-offset and midpoint coordinates. Through this analysis, we propose a mathematically proven procedure to eliminate stretching, which can be applied to any traveltime approximation. The proposed method is applied to synthetic and real data sets, considering different traveltime approximations and achieved complete elimination of stretching.  相似文献   

Predominant period and equivalent viscous damping ratio identification for a full‐scale building shake table test          下载免费PDF全文

Michelle C. Chen  Rodrigo Astroza  José I. Restrepo  Joel P. Conte  Tara Hutchinson  Yehuda Bock 《地震工程与结构动力学》2017,46(14):2459-2477

The predominant period and corresponding equivalent viscous damping ratio, also known in various loading codes as effective period and effective damping coefficient, are two important parameters employed in the seismic design of base‐isolated and conventional building structures. Accurate determination of these two parameters can reduce the uncertainty in the computation of lateral displacement demands and interstory drifts for a given seismic design spectrum. This paper estimates these two parameters from data sets recorded from a full‐scale five‐story reinforced concrete building subjected to seismic base excitations of various intensities in base‐isolated and fixed‐base configurations on the outdoor shake table at the University of California, San Diego. The scope of this paper includes all test motions in which the yielding of the reinforcement has not occurred and the response can still be considered ‘elastic’. The data sets are used with three system identification methods to determine the predominant period of response for each of the test configurations. One of the methods also determines the equivalent viscous damping ratio corresponding to the predominant period. It was found that the predominant period of the fixed‐base building lengthened from 0.52 to 1.30 s. This corresponded to a significant reduction in effective system stiffness to about 16% of the original stiffness. The paper then establishes a correlation between predominant period and peak ground velocity. Finally, the predominant periods and equivalent viscous damping ratios recommended by the ASCE 7‐10 loading standard are compared with those determined from the test building. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Seismic control of flexible rocking structures using inerters     

Rodrigo Thiers-Moggia  Christian Málaga-Chuquitaype 《地震工程与结构动力学》2020,49(14):1519-1538

Allowing flexible structures to uplift and rock during earthquakes can significantly reduce the force demands and residual displacements. However, such structures are still susceptible to large deformations and accelerations that can compromise their functionality. In this paper, we examine the dynamic response of elastic rocking oscillators and suggest that their lateral drifts and accelerations can be limited effectively by using inerter devices. To this end, we offer a detailed examination of the effects of structural flexibility on the efficiency of the proposed system. The analytical expressions governing the motion of deformable structures with base uplift are revisited to incorporate the effects of the supplemental rotational inertia. The proposed model is then used to study the structural demands of flexible rocking structures under coherent pulses as well as noncoherent real pulse-like ground motions. Our results show that combining rocking with inerters can be an efficient strategy to control the deformation and acceleration demands in uplifting flexible systems.  相似文献   

A hybrid deterministic and stochastic approach for tsunami hazard assessment in Iquique,Chile     

González  Juan  González  Gabriel  Aránguiz  Rafael  Melgar  Diego  Zamora  Natalia  Shrivastava  Mahesh N.  Das  Ranjit  Catalán  Patricio A.  Cienfuegos  Rodrigo 《Natural Hazards》2020,101(1):231-253

Natural Hazards - This paper presents an investigation of the collapse of a 325-year-old multi-tiered heritage temple during the 2015 Gorkha earthquake in Kathmandu, Nepal. The research comprises a...  相似文献   

Strong CO₂ outgassing from high nutrient low chlorophyll coastal waters off central Chile (30°S): The role of dissolved iron     

Rodrigo Torres  Patricio Ampuero 《Estuarine, Coastal and Shelf Science》2009

Carbonate system parameters (pH and alkalinity) were used to estimate the coastal water CO₂ fluxes off central Chile (30°S) during September 2007. Coastal waters rich in nitrate and silicate were strongly CO₂ supersaturated and normally poor in chlorophyll a. MODIS satellite chlorophyll a data suggest that phytoplankton biomass remained particularly low during September 2007 although coastal waters were highly fertilized with nitrate and silicate. The phytoplankton gross primary productivity in macronutrient-rich waters was very low with the exception of shallow waters (e.g. within or near bays). Several iron-enrichment bottle experiments show that fCO₂ rapidly decreases during iron-enrichment treatments compared to controls. This suggests that iron limitation of phytoplankton growth (mainly diatoms) plays a role in maintaining high-CO₂ outgassing by preventing rapid interception of upwelled CO₂.  相似文献