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1.
A framework for the generation of bridge-specific fragility curves utilizing the capabilities of machine learning and stripe-based approach is presented in this paper. The proposed methodology using random forests helps to generate or update fragility curves for a new set of input parameters with less computational effort and expensive resimulation. The methodology does not place any assumptions on the demand model of various components and helps to identify the relative importance of each uncertain variable in their seismic demand model. The methodology is demonstrated through the case study of a multispan concrete bridge class in California. Geometric, material, and structural uncertainties are accounted for in the generation of bridge numerical models and their fragility curves. It is also noted that the traditional lognormality assumption on the demand model leads to unrealistic fragility estimates. Fragility results obtained by the proposed methodology can be deployed in a risk assessment platform such as HAZUS for regional loss estimation. 相似文献
2.
Periodical algal blooms result in deposition and release of phosphorus (P) from the sediment into the water. Therefore, during seasonal changes when algal particles begin to settle to the bottom, understanding the behavior and distribution characteristics of the P in sediment is the most important key to manage the water quality of the Saemangeum Reservoir. In this study, the variation of water quality and sediment composition including chlorophyll-a (Chl-a) and P was investigated to determine the interaction between water and sediment. The study focused primarily on algal particle sedimentation that affects the P release and mineralization of sediment. The Chl-a concentration in water showed a sharp decline in October when the algae began to die in the fall, and afterward the concentration of chemical oxygen demand (COD) and total P (TP) in the sediment increased due to the sedimentation of decaying algal particles in November. During the same period of time, the readily bio-available P (RAP) in the sediment showed a drastic increase in the upper region where the Chl-a concentration of water was high. In sequence, the high RAP zone shifted from the upper region to the lower region in the early winter. The RAP shift was considered to be derived from the physical flow of the overlying water from which the decomposing algae settled on the surface of the sediment. The Saemangeum Reservoir was constructed recently; therefore, all the types of inorganic P fractions except soluble reactive phosphorus (SRP) that exist on the bottom surface of the lake and the marsh's sediment layer were not sufficient to significantly influence the overlying water. On the other hand, the released P from the algae was distinct and sensitive to the seasonal change. In conclusion, the algal particle sedimentation was important to control eutrophication rather than P release from the mineralized inorganic P of the sediment surface layer in the Seamangeum Reservoir. 相似文献
3.
Statistical models for shear strength of RC beam‐column joints using machine‐learning techniques 
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下载免费PDF全文 This paper proposes a new set of probabilistic joint shear strength models using the conventional multiple linear regression method, and advanced machine‐learning methods of multivariate adaptive regression splines (MARS) and symbolic regression (SR). In order to achieve high‐fidelity regression models with reduced model errors and bias, this study constructs extensive experimental databases for reinforced and unreinforced concrete joints by collecting existing beam‐column joint subassemblage tests from multiple sources. Various influential parameters that affect joint shear strength such as material properties, design parameters, and joint configuration are investigated through tests of statistical significance. After performing a set of regression analyses, the comparison of simulation results indicates that MARS approach is the best estimation method. Moreover, the accuracy of analytical predictions of the derived MARS model is compared with that of existing joint shear strength relationships. The comparison results show that the proposed model is more accurate compared to existing relationships. This joint shear strength prediction model can be readily implemented into joint response models for evaluation of earthquake performance and inelastic responses of building frames. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
4.
This study investigates total petroleum hydrocarbon (TPH) removal from residual clayey soil, after a washing procedure, using an electrokinetic process. Eight electrokinetic experiments were carried out to investigate the characteristics of TPH removal. When 0.1 M MgSO4 or 0.1 M NaOH was used as an electrolyte, the electric current rapidly increased within the first 100 or 200 h, respectively. A negatively charged soil surface resulted in a more negative zeta potential and greater electroosmotic flow toward the cathode. Therefore, the accumulated electroosmotic flow (EOF) when using 0.1 M NaOH as the anolyte‐purging solution was higher than when using 0.1 M MgSO4. Although the energy consumption for the two purging solutions was similar, the efficiencies of TPH removal when 0.1 M MgSO4 and 0.1 M NaOH with surfactant were used were 0 and 39%, respectively, because the electroosmotic flow rate increased with TPH removal efficiency. When 5% isopropyl alcohol (IPA) was used as a circulation solution, the electric current increased but the TPH removal was similar to that using water. In terms of energy consumption, the use of a surfactant‐enhanced electrokinetic process with NaOH as electrolyte was effective in removing TPHs from low‐permeability soil. 相似文献
5.
Effects of biochar, cow bone, and eggshell on Pb availability to maize in contaminated soil irrigated with saline water 总被引：2，自引：0，他引：2
Yaser A. Almaroai Adel R. A. Usman Mahtab Ahmad Deok Hyun Moon Ju-Sik Cho Young Kyoo Joo Choong Jeon Sang Soo Lee Yong Sik Ok 《Environmental Earth Sciences》2014,71(3):1289-1296
Toxicity of heavy metals adversely affects environment and human health. Organic materials derived from natural matters or wastes have been applied to soils to reduce the mobility of contaminants such as heavy metals. However, the application of cow bone powder (CB), biochar (BC), and eggshell powder (ES) is rarely investigated for the reduction of Pb bioavailability in soils irrigated with saline water. The objective of this study was to assess the effectiveness of CB, BC, and ES additions as immobilizing substances on Pb bioavailability in shooting range soil irrigated with deionized and saline water. Each additive of CB, BC, and ES at 5 % (w/w) was mixed with soils and then the deionized and saline water were irrigated for 21 days. With deionized water irrigation, the soils treated with CB, BC, and ES exhibited higher pH when compared with saline water irrigation. With saline water irrigation, the electrical conductivity, water-soluble anions, and cations were significantly increased in soils treated with CB, BC, and ES. The water-soluble Pb in soils treated with CB, BC, and ES was significantly decreased with saline water irrigation. On the other hand, the water-soluble Pb in soil treated with CB was increased with deionized water irrigation. Only BC with saline water irrigation decreased the Pb concentration in maize shoots. 相似文献
6.
Chang?-Woong?ShinEmail author Cheolsoo?Kim Sang?-Kyung?Byun Dongchull?Jeon Sang?-Chull?Hwang 《Ocean Science Journal》2006,41(4):291-299
Hydrographic surveys were carried out four times in the western channel of the Korea Strait in March and August 2003 and in
June and November 2004. The bottom cold water, which was lower than 10°C, appeared in the channel trough except in March 2003.
It flowed southwestward along the shelf of Korean coasts in August 2003 and in November 2004. The width and the maximum speed
of the intrusion current were about 20 km and approximately 25 cm s-1, respectively, off Ulsan, Korea. The volume transport of the bottom cold water was estimated 0.019 Sv (Sv≡106 m3 s-1) in August 2003 and 0.026 Sv in November 2004. 相似文献
7.
This study investigates the mechanical characteristics of light-weighted soils (LWS) consisting of expanded polystyrene (EPS), dredged clays, and cement through both unconfined and triaxial compression tests. The mechanical characteristics of the compressive strength of LWS are analyzed with varying initial water contents of dredged clays, EPS ratio, cement ratio, and curing pressure. In the triaxial compression test, it is found that the compressive strength of LWS associated with EPS is independent on the effective confining pressure. When both EPS ratio is less than 2% and cement ratio is more than 2%, the compressive strength rapidly decreases after the ultimate value. This signifies that the compressive strength-strain behavior is quite similar to that of the cemented soil. The ground improved by LWS has the compressive strength of 200 kPa associated with the optimized EPS ratio of 3-4% and initial water content of 165-175%. The ultimate compressive strength under both triaxial and unconfined compression tests is almost constant for a cement ratio of up to 2%. 相似文献
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9.
Effects of natural and calcined poultry waste on Cd, Pb and As mobility in contaminated soil 总被引：1，自引：0，他引：1
Jung Eun Lim Mahtab Ahmad Adel R. A. Usman Sang Soo Lee Weon-Tai Jeon Sang-Eun Oh Jae E. Yang Yong Sik Ok 《Environmental Earth Sciences》2013,69(1):11-20
The reuse of waste materials as soil additives could be a welcome development in soil remediation. The mobility of Cd, Pb and As in a contaminated soil was investigated using natural and calcined poultry wastes (eggshell and chicken bone), CaCO3 and CaO at different application rates (0, 1, 3 and 5 %). The chemical composition accompanied with mineralogical composition indicated that CaCO3 and CaO were the major components in natural and calcined eggshells, respectively, while hydroxyapatite (HAP) dominated the natural and calcined chicken bones. The results showed that soil pH tended to increase in response to increasing application rates of all soil additives. The effectiveness of the additives in reducing Cd, Pb and As mobility was assessed by means of chemical extractions with 0.1 N HCl for Cd and Pb or 1 N HCl for As, according to Korean Standard Test (KST) method. Both calcined eggshell and chicken bone were equally effective with CaO or CaCO3 in reducing the concentration of 0.1 N HCl-extractable Cd from 6.17 mg kg?1 to below warning level of 1.5 mg kg?1, especially at the highest application rate. The application of calcined eggshell, CaO and CaCO3 also decreased the concentration of 0.1 N HCl-extractable Pb from 1,012 mg kg?1 to below warning level of 100 mg kg?1. The Pb concentration decreased significantly with an increasing application rate of chicken bone, but remained above warning level even at the highest application rate. On the contrary, natural and calcined chicken bones led to a significant increase in the mobility of As when compared with the control soil. These findings illustrate that calcined eggshell in particular is equally effective as pure chemical additives in stabilizing Cd and Pb in a contaminated agricultural soil. The presence of As in metal-contaminated soils should be taken into consideration when applying phosphate-containing materials as soil additives, because phosphate can compete with arsenate on adsorption sites and result in As mobilization. 相似文献
10.
A Numerical Study on the Screening of Blast-Induced Waves for Reducing Ground Vibration 总被引：1，自引：1，他引：0
Blasting is often a necessary part of mining and construction operations, and is the most cost-effective way to break rock,
but blasting generates both noise and ground vibration. In urban areas, noise and vibration have an environmental impact,
and cause structural damage to nearby structures. Various wave-screening methods have been used for many years to reduce blast-induced
ground vibration. However, these methods have not been quantitatively studied for their reduction effect of ground vibration.
The present study focused on the quantitative assessment of the effectiveness in vibration reduction of line-drilling as a
screening method using a numerical method. Two numerical methods were used to analyze the reduction effect toward ground vibration,
namely, the “distinct element method” and the “non-linear hydrocode.” The distinct element method, by particle flow code in
two dimensions (PFC 2D), was used for two-dimensional parametric analyses, and some cases of two-dimensional analyses were
analyzed three-dimensionally using AUTODYN 3D, the program of the non-linear hydrocode. To analyze the screening effectiveness
of line-drilling, parametric analyses were carried out under various conditions, with the spacing, diameter of drill holes,
distance between the blasthole and line-drilling, and the number of rows of drill holes, including their arrangement, used
as parameters. The screening effectiveness was assessed via a comparison of the vibration amplitude between cases both with
and without screening. Also, the frequency distribution of ground motion of the two cases was investigated through fast Fourier
transform (FFT), with the differences also examined. From our study, it was concluded that line-drilling as a screening method
of blast-induced waves was considerably effective under certain design conditions. The design details for field application
have also been proposed. 相似文献