Bidirectional shaking table tests of a low-cost friction sliding system with flat-inclined surfaces     

Miguel B. Brito  Mitsuyoshi Akiyama  Yoshitaka Ichikawa  Hiroki Yamaguchi  Riki Honda  Naomitsu Ishigaki 《地震工程与结构动力学》2020,49(8):817-837

A novel low-cost friction sliding system for bidirectional excitation is developed to improve the seismic performance of reinforced concrete (RC) bridge piers. The sliding system is a spherical prototype developed by combining a central flat surface with an inclined spherical segment, characterized by stable oscillation and a large reduction in response accelerations on the flat surface. The inclined part provides a restoring force that limits the residual displacements of the system. Conventional steel and concrete are employed to construct a flat-inclined spherical surface atop an RC pier. The seismic forces are dissipated through the frictions generated during the sliding movements; hence, the seismic resilience of bridges can be ensured with a low-cost design solution. The proposed system is fabricated utilizing a mold created by a three-dimensional printer, which facilitates the use of conventional concrete to construct spherical shapes. The concrete surface is lubricated with a resin material to prevent abrasion from multiple input ground motions. To demonstrate the effectiveness of the system, bidirectional shaking table tests are conducted in the longitudinal and transverse directions of a scaled bridge model. The effect of the inclination angle and the flat surface size is investigated. The results demonstrate a large decrease in response acceleration when the system exhibits circular sliding displacement. Furthermore, the inclination angle that generates the smallest residual displacement is identified experimentally.  相似文献   

How much does an extreme rainfall event cost? Material damage and relationships between insurance,rainfall, land cover and urban flooding   总被引：1，自引：0，他引：1  

Miguel Leal  Inês Boavida-Portugal  Marcelo Fragoso  Catarina Ramos 《水文科学杂志》2019,64(6):673-689

This research aims to understand how insurance, rainfall, land cover and urban flooding are related and how these variables influenced the material damage in the Lisbon Metropolitan Area (LMA) during the 2000–2011 period. Correlation coefficients show strong relationships between built-up areas and claims (0.94) and payouts (0.88). Despite no significant relationships being found between rainfall and the amount of material damage per event, three likelihood levels of flooding were determined for hourly rainfall. Unlike the studied period, the number of claims and their spatial distribution during the 2008 extreme rainfall event were strongly dependent on rainfall. Flooding related to the old watercourses assumed greater importance during this extreme event, recovering a more natural/ancient hydrological behaviour. In the LMA, the greatest material damage was the result of high-magnitude/low-probability rainfall events. Lower magnitude events can trigger numerous claims in heavily built-up areas, but they are hardly capable of producing large material damage.  相似文献   

Field investigation of siltation at a tidal harbor: North Port of Incheon,Korea     

Lee  Guan-hong  Shin  Hyun-Jung  Kim  Young Taeg  Dellapenna  Timothy M.  Kim  Kuk Jin  Williams  Joshua  Kim  Seok-Yun  Figueroa  Steven Miguel 《Ocean Dynamics》2019,69(9):1101-1120

Ocean Dynamics - To understand siltation processes within the North Port of Incheon, Korea, this study estimated the sedimentation rate and then determined the dominant mechanisms for the...  相似文献   

A New Appraisal of Sri Lankan BB Zircon as a Reference Material for LA‐ICP‐MS U‐Pb Geochronology and Lu‐Hf Isotope Tracing          下载免费PDF全文

Maristella M. Santos  Cristiano Lana  Ricardo Scholz  Ian Buick  Mark D. Schmitz  Sandra L. Kamo  Axel Gerdes  Fernando Corfu  Simon Tapster  Penelope Lancaster  Craig D. Storey  Miguel A.S. Basei  Eric Tohver  Ana Alkmim  Herminio Nalini  Klaus Krambrock  Cristiano Fantini  Michael Wiedenbeck 《Geostandards and Geoanalytical Research》2017,41(3):335-358

A potential zircon reference material (BB zircon) for laser ablation‐inductively coupled plasma‐mass spectrometry (LA‐ICP‐MS) U‐Pb geochronology and Hf isotope geochemistry is described. A batch of twenty zircon megacrysts (0.5–1.5 cm³) from Sri Lanka was studied. Within‐grain rare earth element (REE) compositions are largely homogeneous, albeit with some variation seen between fractured and homogeneous domains. Excluding fractured cathodoluminescence bright domains, the variation in U content for all analysed crystals ranged from 227 to 368 μg g^?1 and the average Th/U ratios were between 0.20 and 0.47. The Hf isotope composition (0.56–0.84 g/100 g Hf) is homogeneous within and between the grains – mean ¹⁷⁶Hf/¹⁷⁷Hf of 0.281674 ± 0.000018 (2s). The calculated alpha dose of 0.59 × 10¹⁸ g^?1 for a number of BB grains falls within the trend of previously studied, untreated zircon samples from Sri Lanka. Aliquots of the same crystal (analysed by ID‐TIMS in four different laboratories) gave consistent U‐Pb ages with excellent measurement reproducibility (0.1–0.4% RSD). Interlaboratory assessment (by LA‐ICP‐MS) from individual crystals returned results that are within uncertainty equivalent to the TIMS ages. Finally, we report on within‐ and between‐grain homogeneity of the oxygen isotope systematic of four BB crystals (13.16‰ VSMOW).  相似文献   

Evaluation of the removal of heavy metals in a natural wetland impacted by mining activities in Mexico     

Juan Miguel Gómez-Bernal  Esther Aurora Ruiz-Huerta  María Aurora Armienta-Hernández  Víctor Manuel Luna-Pabello 《Environmental Earth Sciences》2017,76(23):801

This research is focused on evaluating heavy metals (Cd, Cu, Fe, Mn, Pb, and Zn) uptake and removal by Eleocharis ovata, Cyperus manimae, Typha dominguensis, and Pteridium aquilinum in a natural wetland impacted by mining activities. We analyzed heavy metals content and distribution in native plants, soils, and water of a semipermanent natural wetland in Taxco de Alarcón, Guerrero, and we also determined the physicochemical characteristics of the water. Translocation factor (TF) and bioconcentration factor (BCF) were evaluated. Results showed that physical and chemical conditions are favorable for plants development. Correlation analysis showed a good and positive relation (0.95) between Cu and Pb in soils and plants. In the analyzed matrices: Zn (0.62–2.20 mg/L) exceeded the permissible limits in water, high concentrations of Pb and Zn (26.57–525.67 and 266.67–983.33 mg/kg, respectively) were detected in the studied soils, and Pb exceeded the normal range for E. ovata and P. aquilinum in the analyzed plants. Uptake of heavy metals in the tissues of different species was found in the following order: root > leaf. Data of TF and BCF showed that E. ovata is a tolerant plant with respect to heavy metals exposure since TF value was greater than 1. This study showed that E. ovata could be considered as a bioaccumulator of heavy metals in contaminated soils.  相似文献   

Two-Dimensional Coupled Distributed Hydrologic–Hydraulic Model Simulation on Watershed     

Miguel Cea  Martin Rodriguez 《Pure and Applied Geophysics》2016,173(3):909-922

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Identification of Bedrock Lithology using Fractal Dimensions of Drainage Networks extracted from Medium Resolution LiDAR Digital Terrain Models     

Joaquín Cámara  Vicente Gómez-Miguel  Miguel Ángel Martín 《Pure and Applied Geophysics》2016,173(3):945-961

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Active Crustal Deformation in the Area of San Carlos,Baja California Sur,Mexico as Shown by Data of Local Earthquake Sequences     

Luis Munguía  Mario González-Escobar  Miguel Navarro  Tito Valdez  Sergio Mayer  Alfredo Aguirre  Victor Wong  Manuel Luna 《Pure and Applied Geophysics》2016,173(10-11):3631-3644

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Estimation of Seismic and Aseismic Deformation in Mexicali Valley,Baja California,Mexico, in the 2006–2009 Period,Using Precise Leveling,DInSAR, Geotechnical Instruments Data,and Modeling     

Olga Sarychikhina  Ewa Glowacka  Braulio Robles  F. Alejandro Nava  Miguel Guzmán 《Pure and Applied Geophysics》2015,172(11):3139-3162

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The effect of El Niño Southern Oscillation cycles on the decadal scale suspended sediment behavior of a coastal dry‐summer subtropical catchment          下载免费PDF全文

Andrew B. Gray  Gregory B. Pasternack  Elizabeth B. Watson  Jonathan A. Warrick  Miguel A. Goñi 《地球表面变化过程与地形》2015,40(2):272-284

Rivers display temporal dependence in suspended sediment–water discharge relationships. Although most work has focused on multi‐decadal trends, river sediment behavior often displays sub‐decadal scale fluctuations that have received little attention. The objectives of this study were to identify inter‐annual to decadal scale fluctuations in the suspended sediment–discharge relationship of a dry‐summer subtropical river, infer the mechanisms behind these fluctuations, and examine the role of El Niño Southern Oscillation climate cycles. The Salinas River (California) is a moderate sized (11 000 km²), coastal dry‐summer subtropical catchment with a mean discharge (Q_mean) of 11.6 m³ s^?1. This watershed is located at the northern most extent of the Pacific coastal North America region that experiences increased storm frequency during El Niño years. Event to inter‐annual scale suspended sediment behavior in this system was known to be influenced by antecedent hydrologic conditions, whereby previous hydrologic activity regulates the suspended sediment concentration–water discharge relationship. Fine and sand suspended sediment in the lower Salinas River exhibited persistent, decadal scale periods of positive and negative discharge corrected concentrations. The decadal scale variability in suspended sediment behavior was influenced by inter‐annual to decadal scale fluctuations in hydrologic characteristics, including: elapsed time since small (~0.1 × Q_mean), and moderate (~10 × Q_mean) threshold discharge values, the number of preceding days that low/no flow occurred, and annual water yield. El Niño climatic activity was found to have little effect on decadal‐scale fluctuations in the fine suspended sediment–discharge relationship due to low or no effect on the frequency of moderate to low discharge magnitudes, annual precipitation, and water yield. However, sand concentrations generally increased in El Niño years due to the increased frequency of moderate to high magnitude discharge events, which generally increase sand supply. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献