Model updating of a bridge structure using vibration test data based on GMPSO and BPNN: case study     

Xia Zhiyuan  Li Aiqun  Shi Huiyuan  Li Jianhui 《地震工程与工程振动(英文版)》2021,20(1)

Model updating issues with high-dimensional and strong-nonlinear optimization processes are still unsolved by most optimization methods.In this study,a hybrid methodology that combines the Gaussian-white-noise-mutation particle swarm optimization(GMPSO),back-propagation neural network(BPNN)and Latin hypercube sampling(LHS)technique is proposed.In this approach,as a meta-heuristic algorithm with the least modification to the standard PSO,GMPSO simultaneously offers convenient programming and good performance in optimization.The BPNN with LHS establishes the meta-models for FEM to accelerate efficiency during the updating process.A case study of the model updating of an actual bridge with no distribution but bounded parameters was carried out using this methodology with two different objective functions.One considers only the frequencies of the main girder and the other considers both the frequencies and vertical displacements of typical points.The updating results show that the methodology is a sound approach to solve an actual complex bridge structure and offers good agreement in the frequencies and mode shapes of the updated model and test data.Based on the shape comparison of the main girder at the finished state with different objective functions,it is emphasized that both the dynamic and static responses should be taken into consideration during the model updating process.  相似文献   

Parameter Uncertainty Propagation in a Rainfall–Runoff Model; Case Study: Karoon-III River Basin     

Homa Razmkhah 《Water Resources》2018,45(1):34-49

Conceptual hydrological models are popular tools for simulating land phase of hydrological cycle. Uncertainty arises from a variety of sources such as input error, calibration and parameters. Hydrologic modeling researches indicate that parametric uncertainty has been considered as one of the most important source. The objective of this study was to evaluate parameter uncertainty and its propagation in rainfall-runoff modeling. This study tried to model daily flows and calculate uncertainty bounds for Karoon-III basin, Southwest of Iran, using HEC-HMS (SMA). The parameters were represented by probability distribution functions (PDF), and the effect on simulated runoff was investigated using Latin Hypercube Sampling (LHS) on Monte Carlo (MC). Three chosen parameters, based on sensitivity analysis, were saturated-hydraulic-conductivity (Ks), Clark storage coefficient (R) and time of concentration (t _c ). Uncertainty associated with parameters were accounted for, by representing each with a probability distribution. Uncertainty bounds was calculated, using parameter sets captured from LHS on parameters PDF of sub-basins and propagating to the model. Results showed that maximum reliability (11%) resulted from Ks propagating. For three parameters, underestimation was more than overestimation. Maximum sharpness and standard deviation (STD) was resulted from propagating Ks. Cumulative Distribution Function (CDF) of flow and uncertainty bounds showed that as flow increased, the width of uncertainty bounds increased for all parameters.  相似文献   

Understanding single-station ground motion variability and uncertainty (sigma): lessons learnt from EUROSEISTEST     

Olga-Joan Ktenidou  Zafeiria Roumelioti  Norman Abrahamson  Fabrice Cotton  Kyriazis Pitilakis  Fabrice Hollender 《Bulletin of Earthquake Engineering》2018,16(6):2311-2336

Accelerometric data from the well-studied valley EUROSEISTEST are used to investigate ground motion uncertainty and variability. We define a simple local ground motion prediction equation (GMPE) and investigate changes in standard deviation (σ) and its components, the between-event variability (τ) and within-event variability (φ). Improving seismological metadata significantly reduces τ (30–50%), which in turn reduces the total σ. Improving site information reduces the systematic site-to-site variability, φ _S2S (20–30%), in turn reducing φ, and ultimately, σ. Our values of standard deviations are lower than global values from literature, and closer to path-specific than site-specific values. However, our data have insufficient azimuthal coverage for single-path analysis. Certain stations have higher ground-motion variability, possibly due to topography, basin edge or downgoing wave effects. Sensitivity checks show that 3 recordings per event is a sufficient data selection criterion, however, one of the dataset’s advantages is the large number of recordings per station (9–90) that yields good site term estimates. We examine uncertainty components binning our data with magnitude from 0.01 to 2 s; at smaller magnitudes, τ decreases and φ _SS increases, possibly due to κ and source-site trade-offs Finally, we investigate the alternative approach of computing φ _SS using existing GMPEs instead of creating an ad hoc local GMPE. This is important where data are insufficient to create one, or when site-specific PSHA is performed. We show that global GMPEs may still capture φ _SS , provided that: (1) the magnitude scaling errors are accommodated by the event terms; (2) there are no distance scaling errors (use of a regionally applicable model). Site terms (φ _S2S ) computed by different global GMPEs (using different site-proxies) vary significantly, especially for hard-rock sites. This indicates that GMPEs may be poorly constrained where they are sometimes most needed, i.e., for hard rock.  相似文献   

An Elitist Multiobjective Tabu Search for Optimal Design of Groundwater Remediation Systems          下载免费PDF全文

Yun Yang  Jianfeng Wu  Jinguo Wang  Zhifang Zhou 《Ground water》2017,55(6):811-826

This study presents a new multiobjective evolutionary algorithm (MOEA), the elitist multiobjective tabu search (EMOTS), and incorporates it with MODFLOW/MT3DMS to develop a groundwater simulation‐optimization (SO) framework based on modular design for optimal design of groundwater remediation systems using pump‐and‐treat (PAT) technique. The most notable improvement of EMOTS over the original multiple objective tabu search (MOTS) lies in the elitist strategy, selection strategy, and neighborhood move rule. The elitist strategy is to maintain all nondominated solutions within later search process for better converging to the true Pareto front. The elitism‐based selection operator is modified to choose two most remote solutions from current candidate list as seed solutions to increase the diversity of searching space. Moreover, neighborhood solutions are uniformly generated using the Latin hypercube sampling (LHS) in the bounded neighborhood space around each seed solution. To demonstrate the performance of the EMOTS, we consider a synthetic groundwater remediation example. Problem formulations consist of two objective functions with continuous decision variables of pumping rates while meeting water quality requirements. Especially, sensitivity analysis is evaluated through the synthetic case for determination of optimal combination of the heuristic parameters. Furthermore, the EMOTS is successfully applied to evaluate remediation options at the field site of the Massachusetts Military Reservation (MMR) in Cape Cod, Massachusetts. With both the hypothetical and the large‐scale field remediation sites, the EMOTS‐based SO framework is demonstrated to outperform the original MOTS in achieving the performance metrics of optimality and diversity of nondominated frontiers with desirable stability and robustness.  相似文献   

Hydrodynamics of coupled flow above and below a sediment–water interface with triangular bedforms     

M. Bayani Cardenas  J.L. Wilson 《Advances in water resources》2007

The hydrodynamics of a system where there is a coupled flow above and below a sediment–water interface (SWI) are not completely understood. We numerically simulate mean two-dimensional, unidirectional, steady, viscous flow in these systems using a sequentially coupled formulation. Simulations were conducted to determine fundamental relationships between bedform geometry, Reynolds number for the water-column flow (Re), interfacial exchange zone depth (d_z) in the sediments, and flux through the SWI (q_int); the latter two parameters play a significant role in biogeochemical and aquatic-life processes across the SWI. d_z and Re are functionally related through an asymptotic growth-curve model while q_int and Re follow a power function. These relationships are dynamically explained by the manner in which pressure gradients along the SWI develop due to current–bedform interactions at different Res and by Darcy’s Law. We found that the coupling between water column and exchange zone flow is controlled by the behavior of the water-column eddy. The eddy detaches at or near the point of minimum pressure along the interface, and reattaches near the point of maximum pressure. These two critical points determine the pressure gradient along the bed surface that controls the exchange zone flow field. Moreover, the reattachment point corresponds to flow divides within the sediments. Lastly, pore-water velocities drop with depth below the SWI, and are larger below the bedform crests than below the troughs.  相似文献   

Impact of Poroelastic Response of Sandstones on Geothermal Power Production     

Guido Blöcher  Günter Zimmermann  Harald Milsch 《Pure and Applied Geophysics》2009,166(5-7):1107-1123

During geothermal power production using a borehole doublet consisting of a production and injection well, the reservoir conditions such as permeability k, porosity φ and Skempton coefficient B at the geothermal research site Gross Schoenebeck/Germany will change. Besides a temperature decrease at the injection well and a change of the chemical equilibrium, also the pore pressure p _p will vary in a range of approximately 44 MPa ± 10 MPa in our reservoir at ?3850 to ?4258 m depth. This leads to a poroelastic response of the reservoir rocks depending on effective pressure p _eff (difference between mean stress and pore pressure), resulting in a change in permeability k, porosity φ and the poroelastic parameter Skempton coefficient B. Hence, we investigated the effective pressure dependency of Flechtinger sandstone, an outcropping equivalent of the reservoir rock via laboratory experiments. The permeability decreased by 21% at an effective pressure range from 3 to 30 MPa, the porosity decreased by 11% (p _eff = 6 to 65 MPa) and the Skempton coefficient decreased by 24% (p _eff = 4 to 25 MPa). We will show which mechanisms lead to the change of the mentioned hydraulic and poroelastic parameters and the influence of these changes on the productivity of the reservoir. The most significant changes occur at low effective pressures until 15 to 20 MPa. For our in situ reservoir conditions p _eff = 43 MPa a change of 10 MPa effective pressure will result in a change in matrix permeability of less than 4% and in matrix porosity of less than 2%. Besides natural fracture systems, fault zones and induced hydraulic fractures, the rock matrix its only one part of geothermal systems. All components can be influenced by pressure, temperature and chemical reactions. Therefore, the determined small poroelastic response of rock matrix does not significantly influence the sustainability of the geothermal reservoir.  相似文献   

三峡水库典型支流库湾沉积物CH₄产生和氧化规律          下载免费PDF全文

孟江槐  康满春  纪道斌  刘佳  肖尚斌  胡杰茗  韩燕星 《湖泊科学》2023,35(5):1670-1681

以三峡水库香溪河库湾为研究对象,采用原位加密采样(2021年5月)和室内培养方法,结合沉积物特性与水环境因子分析,探讨了香溪河库湾沉积物甲烷(CH₄)释放潜力、沉积物-水界面CH₄产生和氧化通量空间分布规律及其影响因素。结果表明:三峡水库泄水期间,香溪河库湾沉积物CH₄释放潜力的变化范围是6.35-2029.37 mg/(kg·d),沉积物-水界面CH₄产生通量和氧化通量的变化范围分别为0.04～0.73、0.03～0.62 mmol/(m²·d);空间上,沉积物CH₄释放潜力、沉积物-水界面CH₄产生及氧化通量在香溪河库湾和各典型横切面(XX02、XX05和XX06)间表现出空间差异性,主要受水深、TOC和温度的影响。垂向上,CH₄产生速率随沉积物深度的增加而减小,表层20 cm沉积物CH₄释放潜力占整柱沉积物的70%,可以用于估算库湾沉积物CH₄释放潜力。此外,沉积...  相似文献   

Elasticity of aluminate,titanate, stannate and germanate compounds with the perovskite structure     

Robert C Liebermann  Leonie E.A Jones  A.E Ringwood 《Physics of the Earth and Planetary Interiors》1977,14(2):165-178

Ultrasonic data for the velocities of a large number of perovskite-structure compounds have been determined as a a function of pressure to 6 kbar at room temperature for polycrystalline specimens hot-pressed at pressures up to 100 kbar in solid-media devices: ScAlO₃, GdAlO₃, SmAlO₃, EuAlO₃, YAlO₃, CdTiO₃, CdSnO₃, CaSnO₃ and CaGeO₃. The elasticity data for these orthorhombic and cubic perovskites define systematic patterns on bulk modulus (K_S)-volume (V_O) and bulk sound velocity (υ_φ—mean atomic weight (M) diagrams which are insensitiv to the details of cation chemistry and crystallographic structure. These isostructural trends are used to estimate K_S = 2.5 ± 0.3 Mbar and υ_φ = 7.9 ± 0.4 km/s for the perovskite polymorph of MgSiO₃. On a Birch diagram of veloc vs. density, the perovskite data define linear trends which lead to erroneous estimates of velocity for MgSiO₃ unless specific account is taken of ionic radius effects in isomorphic substitutions.  相似文献   

Elasticity of ilmenites     

Robert C. Liebermann 《Physics of the Earth and Planetary Interiors》1976,12(1):P5-P10

Ultrasonic data for the velocities of the ilmenites MgTiO₃ and CoTiO₃ have been determined as a function of pressure to 7.5 kbar at room temperature for polycrystalline specimens hot-pressed in a piston-cylinder apparatus at pressures up to 30 kbar. Titanate and germanate ilmenites define divergent isostructural trends on a Birch diagram of bulk sound velocity (υ_φ) vs. density (ρ). On a υ_φ vs. mean atomic weight ($\text{M}$) diagram, however, all of the ilmenite consistent with a single $\text{υ}{}_{\mathrm{\phi }}\text{M}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{=}\text{constant trend}$. Elasticity systematics for isostructural sequences are used to e the bulk modulus (2.09 Mbar) and bulk sound velocity (7.4 km/sec) of MgSiO₃-elmenite.  相似文献   

Estimation of co-conditional moments of transmissivity,hydraulic head,and velocity fields     

《Advances in water resources》1998,22(1):87-95

An iterative co-conditional Monte Carlo simulation (IMCS) approach is developed. This approach derives co-conditional means and variances of transmissivity (T), head (φ), and Darcy's velocity (q), based on sparse measurements of T and φ in heterogeneous, confined aquifers under steady-state conditions. It employs the classical co-conditional Monte Carlo simulation technique (MCS) and a successive linear estimator that takes advantage of our prior knowledge of the covariances of T and φ and their cross-covariance. In each co-conditional simulation, a linear estimate of T is improved by solving the governing steady-state flow equation, and by updating residual covariance functions iteratively. These residual covariance functions consist of the covariance of T and φ and the cross-covariance function between T and φ. As a result, the non-linear relationship between T and φ is incorporated in the co-conditional realizations of T and φ. Once the T and φ fields are generated, a corresponding velocity field is also calculated. The average of the co-conditioned realizations of T, φ, and q yields the co-conditional mean fields. In turn, the co-conditional variances of T, φ, and q, which measure the reduction in uncertainty due to measurements of T and φ, are derived. Results of our numerical experiments show that the co-conditional means from IMCS for T and φ fields have smaller mean square errors (MSE) than those from a non-iterative Monte Carlo simulation (NIMCS). Finally, the co-conditional mean fields from IMCS are compared with the co-conditional effective fields from a direct approach developed by Yeh et al. [Water Resources Research, 32(1), 85–92, 1996].  相似文献   

Timescales of seawater intrusion and retreat     

《Advances in water resources》2013

Quantifying the timescales associated with moving freshwater–seawater interfaces is critical for effective management of coastal groundwater resources. In this study, timescales of interface movement in response to both inland and coastal water level variations are investigated. We first assume that seawater intrusion (SWI) and retreat (SWR) are driven by an instantaneous freshwater-level variation at the inland boundary. Numerical modelling results reveal that logarithmic timescales of SWI (lnT_i) and SWR (lnT_r) can be described respectively by various simple linear equations. For example, SWI timescales are described by lnT_i = a + blnh′_f–s, where a and b are linear regression coefficients and h′_f–s is the boundary head difference after an instantaneous drop of inland freshwater head. For SWR cases with the same initial conditions, but with different increases in freshwater head, lnT_r = c + dΔX_T, where c and d are regression coefficients and ΔX_T is the distance of toe response that can be estimated by a steady-state, sharp-interface analytical solution. For SWR cases with the same freshwater head increase, but with different initial conditions, in contrast, lnT_r = e + flnΔX_T, where e and f are regression coefficients. The timescale of toe response caused by an instantaneous variation of sea level is almost equivalent to that induced by an instantaneous inland head variation with the same magnitude of water level change, but opposite in direction. Accordingly, the empirical equations of this study are also applicable for sea-level variations in head-controlled systems or for simultaneous variations of both inland and coastal water levels. Despite the idealised conceptual models adopted in this study, the results imply that for a particular coastal aquifer, SWI timescales are controlled by the boundary water levels after variations, whereas SWR timescales are dominated by the distance of toe response.  相似文献   

Gas exsolution and flow during supersaturated water injection in porous media: II. Column experiments and continuum modeling     

R. EnouyM. Li  M.A. Ioannidis  A.J.A. Unger 《Advances in water resources》2011,34(1):15-25

Degassing and in situ development of a mobile gas phase takes place when an aqueous phase equilibrated with a gas at a pressure higher than the subsurface pressure is injected in water-saturated porous media. This process, which has been termed supersaturated water injection (SWI), is a novel and hitherto unexplored means of introducing a gas phase in the subsurface. We give herein a first macroscopic account of the SWI process on the basis of continuum scale simulations and column experiments with CO₂ as the dissolved gas. A published empirical mass transfer correlation [Nambi IM, Powers SE. Mass transfer correlations for nonaqueous phase liquid dissolution from regions with high initial saturations. Water Resour Res 2003;39(2):1030. doi:10.1029/2001WR000667] is found to adequately describe non-equilibrium transfer of CO₂ between the aqueous and gas phases. Remarkably, the dynamics of gas-water two-phase flow, observed in a series of SWI experiments in homogeneous columns packed with silica sand or glass beads, are accurately predicted by traditional two-phase flow theory and the corresponding gas relative permeability is determined. A key consequence of this finding, namely that the displacement of the aqueous phase by gas is compact at the macroscopic scale, is consistent with pore scale simulations of repeated mobilization, fragmentation and coalescence of large gas clusters (i.e., large ganglion dynamics) driven entirely by mass transfer. The significance of this finding for the efficient delivery of a gas phase below the water table is discussed in connection to the alternative process of in situ air sparging, and potential advantages of SWI are highlighted.  相似文献   

Distribution of the surface partial pressure of CO2 in the southern Yellow Sea and its controls     

Longjun Zhang  Liang Xue  Meiqin Song  Chunbo Jiang 《Continental Shelf Research》2010,30(3-4):293-304

Surface partial pressure of CO₂ (pCO₂), dissolved inorganic carbon (DIC), temperature, salinity and chlorophyll a (Chl a) at grid stations were measured in the southern Yellow Sea (SYS; 32–37°N to 120–125°E) during four cruises conducted in March 2005 (winter), April 2006 (spring), May 2005 (late spring), and July 2001 (summer). Factors influencing pCO₂ spatial and seasonal variations are explored.Surface seawater pCO₂ during winter was oversaturated with respect to the atmosphere in the entire study area (380–606 μatm), primarily due to the complete mixing of the water column in winter which brought CO₂-enriched bottom water to the surface. However, during spring, surface pCO₂ in the central SYS was undersaturated relative to the atmosphere with a low range between 274 and 408 μatm. The net CO₂ sink in the central SYS was mainly due to the consumption of CO₂ by the strong phytoplankton activity and to the weak water stratification, whereas surface pCO₂ in the nearshore area was oversaturated for the atmosphere owing to vertical mixing and terrestrial inputs. During summer, surface pCO₂ varied between 125 and 599 μatm over the entire sampling area. In the Changjiang (Yangtze River) Diluted Water (CDW) area, surface pCO₂ was undersaturated because of the nutrient inputs via the Changjiang, triggering strong phytoplankton activity, whereas surface pCO₂ was oversaturated in other areas. We conclude that the nearshore area behaves as a source of atmospheric CO₂ during the entire investigated periods owing to vertical mixing and terrestrial inputs as well as upwelling, whereas the central region generally shifts from a source of CO₂ in March to a sink in the remaining time of the investigation.  相似文献   

Ion microprobe studies of water in silicate melts. Concentration-dependent water diffusion in obsidian     

J.R. Delaney  J.L. Karsten 《Earth and Planetary Science Letters》1981,52(1):191-202

The ion microprobe at Johnson Space Center has been calibrated for in situ water determinations on a 10-μm scale over the range 0.2 wt.% H₂O to 1.8, 6.8, and 3.7 wt.%, for basaltic, albitic, and rhyolitic glasses, respectively. The basalt glass calibration curve differs substantially from those of albite and rhyolite glasses, indicating a need to carefully match composition and/or melt structure between H₂O standards and unknowns.A value for the diffusivity of water as a function of concentration and time has been calculated from water diffusion profiles measured in rhyolite glasses prepared at 850°C and 700 barsP_t(H₂O) [1]. Transient diffusion into a semi-infinite medium is described by the equation:?(φ/2)?¸/?φ=?(D_w?¸/?φ)/?φ #x003B8;=1, φ=0, θ→ 0, θ→∞, wherex =distance from the cylinder edge,t =time,C₀ =initial concentration,C_s =concentration at the edge,C =concentration at x,θ = C ? C₀/C_s ? C₀,φ = x/t^1/2, andD_w =diffusivity of water. An iterative technique has been used to calculate solutions to the diffusion equation as a function ofD_w [2]. Comparison of these solutions with the ion probe data indicate that, for0.2wt.% ≤ C ≤ 3.7wt.%H₂O,D_w can be described by an exponential function of θ, of the formD_w = D₀exp(bθ), withD₀ (i.e.,D_w at 0.2%) = (0.8?2.2) × 10^?8 cm²/s and2 ≤ b ≤ 4.  相似文献   

Observations of neutral hydrogen in the corona     

I. S. Kim  V. V. Popov  D. V. Lisin  A. P. Osokin 《Geomagnetism and Aeronomy》2013,53(7):901-903

Measurements of the linear polarization degree (p) of the emission in the inner corona (<1.5 R _⊙) in the green and red continuum ranges are discussed. “Excess p” (Δp = pgreen — pred), which reaches its maximum at 1.2–1.3 R _⊙ (<5%) in the polar regions and 20% within large-scale streamers, is present everywhere in the corona. It has been mentioned that excess p can be explained by the presence of neutral hydrogen in the corona.  相似文献   

Amplitude-dependent effects of longitudinal seismic wave propagation in the interhole space     

E. I. Mashinskii 《Izvestiya Physics of the Solid Earth》2007,43(8):683-690

Field investigations of the amplitude dependence of the P wave velocity in dry and water-saturated rocks are carried out in the space between two shallow boreholes. The seismic wave velocity nonlinearly varies with the strain amplitude in the range ～(4–50) × 10^?8. The pattern of the velocity variation with amplitude depends on the pulse propagation direction. In dry and partially water-saturated rocks, the wave velocity decreases by 1.5% with the amplitude increasing within the range mentioned above and increases by 0.4% in completely water-saturated rocks (with an accuracy of up to 0.1%). Amplitude variations within a closed cycle (A _min … → A _max … → A _min) lead to hysteresis in the V _p (A _min-max-min) dependence (i.e., the ascending and descending branches of the curve do not coincide). If the hysteretic loop is not closed, the residual velocity component ΔV _p (A) is present. This effect is observed in dry and weakly saturated rocks. In a completely saturated rock, hysteresis of the velocity dependence is absent; the ascending and descending amplitude branches coincide. It is suggested that the amplitude characteristics and their hysteresis can be used in the future as an additional criterion for the differentiation of rocks by their fluid saturation.  相似文献