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Performance-based seismic assessment of skewed bridges with and without considering soil-foundation interaction effects for various site classes

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Earthquake engineering and engineering Vibration 2014年第3期13卷 357-373页

作者： Abdoul R.Ghotbi Civil & environmental engineering department University of California

The seismic behavior of skewed bridges has not been well studied compared to straight bridges. Skewed bridges have shown extensive damage, especially due to deck rotation, shear keys failure, abutment unseating and column- bent drift. This research, therefore, aims to study the behavior of skewed and straight highway overpass bridges both with and without taking into account the effects of Soil-Structure Interaction （SSI） due to near-fault ground motions. Due to several sources of uncertainty associated with the ground motions, soil and structure, a probabilistic approach is needed. Thus, a probabilistic methodology similar to the one developed by the Pacific Earthquake engineering Research Center （PEER） has been utilized to assess the probability of damage due to various levels of shaking using appropriate intensity measures with minimum dispersions. The probabilistic analyses were performed for various bridge configurations and site conditions, including sand ranging from loose to dense and clay ranging from soft to stiff, in order to evaluate the effects. The results proved a considerable susceptibility of skewed bridges to deck rotation and shear keys displacement. It was also found that SSI had a decreasing effect on the damage probability for various demands compared to the fixed-base model without including SSI. However, deck rotation for all types of the soil and also abutment unseating for very loose sand and soft clay showed an increase in damage probability compared to the fixed-base model. The damage probability for various demands has also been found to decrease with an increase of soil strength for both sandy and clayey sites. With respect to the variations in the skew angle, an increase in skew angle has had an increasing effect on the amplitude of the seismic response for various demands. Deck rotation has been very sensitive to the increase in the skew angle; therefore, as the skew angle increased, the deck rotation responded accordingly. Furthermor

关键词： skewed bridges SSI demand model probabilistic assessment damage probability

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Use of polymeric sub-micron ion-exchange resins for removal of lead,copper,zinc,and nickel from natural waters

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Journal of environmental Sciences 2019年第1期31卷 247-254页

作者： Audrey Murray Banu ?rmeci department of Civil and environmental engineering Carleton University

This research investigated the removal capacity of polymeric sub-micron ion-exchange resins(SMR) for removal of lead, copper, zinc, and nickel from natural waters in competition with natural organic matter(NOM). Polymeric SMR particles were created and tested to ensure that they were adequately dispersed in the solution. They removed little NOM(10%or less) from river water and wastewater, indicating that competition from NOM was not a major concern. SMR were able to remove 82% ± 0.2% of lead, 46% ± 0.6% of copper, 55% ±20% of zinc, and 17% ± 2% of nickel from river water spiked with 500 μg/L of each. Similarly,in wastewater, they were able to remove 86% ± 0.1% of lead, 38% ± 0.8% of copper, 28% ± 1%of zinc, and 11% ± 1% of nickel.

关键词： Water Wastewater Heavy metals Ion exchange Polymeric submicron resin Natural organic matter (NOM)

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Estimation of drag forces caused by natural woody vegetation of different scales

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Journal of Hydrodynamics 2014年第4期26卷 608-623页

作者： JALONEN Johanna JRVEL Juha department of Civil and environmental engineering Aalto University

To reliably estimate water levels and velocities in vegetated rivers and floodplains, flow resistance models based on physical plant properties are advantageous. The purpose of this study is （1） to assess the suitable parameterization of woody riparian vegetation in estimating the drag forces, （2） to address the effect of plant scale on the drag estimates and reconfiguration, and （3） to evaluate the applicability of three recently developed flow resistance models. Experiments on four tree species in a towing tank together with detailed characterization of tree properties were carried out to establish a novel dataset. Despite the variability in the tree height （0.9 m-3.4 m）, the stem, leaf and total areas proved to be suitable characteristic dimensions for estimating the flow resistance at different scales. Evaluations with independent data revealed that the tested models produced reasonable results. The performance of the models was controlled by the parameter values used rather than the model structure or the plant scale.

关键词： drag force flow resistance woody vegetation modelling

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Selection of noise parameters for Kalman filter

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Earthquake engineering and engineering Vibration 2007年第1期6卷 49-56页

作者：阮家荣许嘉贤莫启明 department of Civil and environmental engineering University of Macao

The Bayesian probabilistic approach is proposed to estimate the process noise and measurement noise parameters for a Kalman filter. With state vectors and covariance matrices estimated by the Kalman filter, the likehood of the measurements can be constructed as a function of the process noise and measurement noise parameters. By maximizing the likelihood function with respect to these noise parameters, the optimal values can be obtained. Furthermore, the Bayesian probabilistic approach allows the associated uncertainty to be quantified. Examples using a single-degree-of-freedom system and a ten-story building illustrate the proposed method. The effect on the performance of the Kalman filter due to the selection of the process noise and measurement noise parameters was demonstrated. The optimal values of the noise parameters were found to be close to the actual values in the sense that the actual parameters were in the region with significant probability density. Through these examples, the Bayesian approach was shown to have the capability to provide accurate estimates of the noise parameters of the Kalman filter, and hence for state estimation.

关键词： Bayesian inference Kalman filter measurement noise process noise state estimation

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Performance and mechanism of Prussian blue (PB) modified carbon felt electrode

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中国有色金属学会会刊：英文版 2009年第S3期19卷 594-599页

作者：薛方勤张鸿涛吴春旭宁涛徐璇 department of environmental Science and engineering Tsinghua University

Prussian blue (PB) modified carbon felt electrodes were prepared. The electrochemical behavior was investigated by cyclic voltammetry, electrochemical impedance spectroscopy and charge-discharge experiments. In order to distinguish the mechanism of the PB modified carbon felt electrode, the electrochemical quartz crystal microbalance (EQCM) was employed. The results of cyclic voltammetry show that the modification can improve the reversibility and the suitable PB deposition is the amount of 10 circles deposition. PB modified carbon felt electrode can effectively decrease the charge transfer resistance. The voltage efficiency of VRB employing PB modified carbon felt electrode can be increased by 12%. The mass change of the PB modified Pt crystal electrode in the process of the potential scan is obvious. The reaction of substitution of VO2+ for high-spin Fe ion in PB is probable to happen and the possible reaction equation is given. The preliminary exploration shows that PB modified carbon felt is electrochemically promising for redox flow battery.

关键词： porous electrode carbon felt redox flow battery (RFB) Prussian blue electrochemical quartz crystal microbalance

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Distribution and mode of occurrence of uranium in bottom ash derived from high-germanium coals

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Journal of environmental Sciences 2016年第5期28卷 91-98页

作者： Yinglong Sun Guangxia Qi Xuefei Lei Hui Xu Lei Li Chao Yuan Yi Wang department of environmental engineering School of Environment Tsinghua University department of environmental Science and engineering School of Food and Chemical EngineeringBeijing Technology and Business University

The radioactivity of uranium in radioactive coal bottom ash（CBA） may be a potential danger to the ambient environment and human health. Concerning the limited research on the distribution and mode of occurrence of uranium in CBA, we herein report our investigations into this topic using a number of techniques including a five-step Tessier sequential extraction, hydrogen fluoride（HF） leaching, Siroquant（Rietveld） quantification, magnetic separation, and electron probe microanalysis（EPMA）. The Tessier sequential extraction showed that the uranium in the residual and Fe–Mn oxide fractions was dominant（59.1%and 34.9%, respectively）. The former was mainly incorporated into aluminosilicates,retained with glass and cristobalite, whereas the latter was especially enriched in the magnetic fraction, of which about 50% was present with magnetite（Fe_3O_4） and the rest in other iron oxides. In addition, the uranium in the magnetic fraction was 2.6 times that in the non-magnetic fraction. The experimental findings in this work may be important for establishing an effective strategy to reduce radioactivity from CBA for the protection of our local environment.

关键词： Coal bottom ash Uranium Radioactivity Tessier sequential extraction Magnetic separation

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Effects of structural characterizations on fragility functions of bridges subject to seismic shaking and lateral spreading

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Earthquake engineering and engineering Vibration 2008年第4期7卷 369-382页

作者： Scott J.Brandenberg Pirooz Kashighandi department of Civil and environmental engineering University of California

This paper evaluates the seismic vulnerability of different classes of typical bridges in California when subjected to seismic shaking or liquefaction-induced lateral spreading. The detailed structural configurations in terms of superstructure type, connection, continuity at support and foundation type, etc. render different damage resistant capability. Six classes of bridges are established based on their anticipated failure mechanisms under earthquake shaking. The numerical models that are capable of simulating the complex soil-structure interaction effects, nonlinear behavior of columns and connections are developed for each bridge class. The dynamic responses are obtained using nonlinear time history analyses for a suite of 250 earthquake motions with increasing intensity. An equivalent static analysis procedure is also implemented to evaluate the vulnerability of the bridges when subjected to liquefaction-induced lateral spreading. Fragility functions for each bridge class are derived and compared for both seismic shaking （based on nonlinear dynamic analyses） and lateral spreading （based on equivalent static analyses） for different performance states. The study finds that the fragility functions due to either ground shaking or lateral spreading show significant correlation with the structural characterizations, but differences emerge for ground shaking and lateral spreading conditions. Structural properties that will mostly affect the bridges＇ damage resistant capacity are also identified.

关键词： fragility functions bridge seismic response liquefaction lateral spreading structural characterization

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Effect of Na^+ impregnated activated carbon on the adsorption of NH_4^+-N from aqueous solution

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Journal of environmental Sciences 2013年第8期25卷 1501-1510页

作者： Mo Shi Zhengfang Wang Zheng Zheng environmental Science and engineering department Fudan University

Two kinds of activated carbons modified by Na＋ impregnation after pre-treatments involving oxidation by nitric acid or acidification by hydrochloric acid （denoted as AC/N-Na and AC/HCl-Na, respectively）, were used as adsorbents to remove NH4＋-N. The surface features of samples were investigated by BET, SEM, XRD and FT-IR. The adsorption experiments were conducted in equilibrium and kinetic conditions. Influencing factors such as initial solution pH and initial concentration were investigated. A possible mechanism was proposed. Results showed that optimal NH4＋-N removal efficiency was achieved at a neutral pH condition for the modified ACs. The Langmuir isotherm adsorption equation provided a better fit than other models for the equilibrium study. The adsorption kinetics followed both the pseudo second-order kinetics model and intra-particle kinetic model. Chemical surface analysis indicated that Na＋ ions form ionic bonds with available surface functional groups created by pre-treatment, especially oxidation by nitric acid, thus increasing the removal efficiency of the modified ACs for NH4＋-N. Na＋-impregnated ACs had a higher removal capability in removing NH4＋-N than unmodified AC, possibly resulting from higher numbers of surface functional groups and better intra-particle diffusion. The good fit of Langmuir isotherm adsorption to the data indicated the presence of monolayer NH4＋-N adsorption on the active homogenous sites within the adsorbents. The applicability of pseudo second-order and intra-particle kinetic models revealed the complex nature of the adsorption mechanism. The intra-particle diffusion model revealed that the adsorption process consisted not only of surface adsorption but also intra-particle diffusion.

关键词： NH4+-N adsorption Na+-impregnated activated carbon isotherm kinetics mechanism

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Model tests and numerical analyses on horizontal impedance functions of inclined single piles embedded in cohesionless soil

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Earthquake engineering and engineering Vibration 2013年第1期12卷 143-154页

作者： Chandra Shekhar Goit Masato Saitoh department of Civil and environmental engineering Saitama University

Horizontal impedance functions of inclined single piles are measured experimentally for model soil-pile systems with both the effects of local soil nonlinearity and resonant *** practical pile inclinations of 5掳 and 10掳 in addition to a vertical pile embedded in cohesionless soil and subjected to lateral harmonic pile head loadings for a wide range of frequencies are *** obtained with low-to-high amplitude of lateral loadings on model soil-pile systems encased in a laminar shear box show that the local nonlinearities have a profound impact on the horizontal impedance functions of *** impedance functions of inclined piles are found to be smaller than the vertical pile and the values decrease as the angle of pile inclination *** values of horizontal impedance functions are obtained for the ＇positive＇ and ＇negative＇ cycles of harmonic loadings,leading to asymmetric force-displacement relationships for the inclined *** of these experimental results is carried out through three-dimensional nonlinear finite element analyses,and the results from the numerical models are in good agreement with the experimental *** analyses conducted on the numerical models suggest that the consideration of local nonlinearity at the vicinity of the soil-pile interface influence the response of the soil-pile systems.

关键词： inclined single piles harmonic loads horizontal impedance functions local nonlinearity finite element model

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Investigation on the Effects and Mechanisms of PTFE Surface Modification by Low Pressure Plasma

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Plasma Science and Technology 2012年第8期14卷 728-734页

作者：刘红霞刘云 department of environmental engineering Xi'an Jiaotong University

Using argon as the work gas, the effects and mechanisms of poly（tetrafluoroethylene）（PTFE） film surface modification were investigated in a low pressure plasma reactor. Results show that higher hydrophilicity with little degradation, in terms of the scanning electron microscopy （SEM）, was obtained after treatment, especially when the sample was placed in the post-discharge area. More polar functional groups and higher surface free energy, especially the polar component, formed on the PTFE surface were responsible for the modification. For the relatively high purity radicals and rare discharge particles in the post-discharge area, the etching was restrained and the introducing reactions were enhanced, and thus, a better modification occurred there.

关键词： low pressure plasma poly(tetrafiuoroethylene) surface modification

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