System identification applied to long‐span cable‐supported bridges using seismic records

This paper presents the application of system identification (SI) to long‐span cable‐supported bridges using seismic records. The SI method is based on the System Realization using Information Matrix (SRIM) that utilizes correlations between base motions and bridge accelerations to identify coefficient matrices of a state‐space model. Numerical simulations using a benchmark cable‐stayed bridge demonstrate the advantages of this method in dealing with multiple‐input multiple‐output (MIMO) data from relatively short seismic records. Important issues related to the effects of sensor arrangement, measurement noise, input inclusion, and the types of input with respect to identification results are also investigated. The method is applied to identify modal parameters of the Yokohama Bay Bridge, Rainbow Bridge, and Tsurumi Fairway Bridge using the records from the 2004 Chuetsu‐Niigata earthquake. Comparison of modal parameters with the results of ambient vibration tests, forced vibration tests, and analytical models are presented together with discussions regarding the effects of earthquake excitation amplitude on global and local structural modes. Copyright © 2007 John Wiley & Sons, Ltd.     

Performance Evaluation of a Full‐Scale Extended Aeration System in Al‐Bireh City,Palestine

Major challenges attributed to dysfunctional wastewater treatment facilities in developing countries include lack of commitment and poor informed decision making by the higher municipal administration. This paper presents how process monitoring and control during full scale operation ensures sustainability of civic infrastructures like Al‐Bireh wastewater treatment plant (AWWTP). It is written from the perspective of practical process selection to evaluate the performance of AWWTP, a single‐sludge nitrification–denitrification process with aerobic sludge stabilization. Process monitoring data (July 2000–April 2007) from available monthly operating reports were analyzed and evaluated. Additional data on microbiological analysis and information about facility unit operations were gathered through review of published local literature and interviews with AWWTP personnel. Influent and effluent data evaluated were the chemical oxygen demand (COD), biological oxygen demand (BOD), total nitrogen (TN), and total phosphorus (TP). Despite annual and seasonal variations in AWWTP influent for COD, BOD, TN, and TP, the Palestinian wastewater reuse requirements for restricted irrigation were met. Process design and proper facility operation have direct impacts on effluent quality. The study concludes that regardless of the design capacity and process type, adequate administrative and operational management dictate the sustainability of AWWTP and reuse schemes.     

Non‐linear‐Maxwell‐element‐type hysteretic control force

A simple non‐linear control law is proposed for reducing structural responses against seismic excitations. This law defines control force dynamics by one differential equation involving a non‐linear term that restrains the control force amplitude. If non‐linearity is neglected, the control force becomes the force in a Maxwell element, so it is called the non‐linear‐Maxwell‐element‐type (NMW) control force. The NMW control force vs. deformation relation plots hysteretic curves. The basic performance of an SDOF model with the NMW control force is examined for various conditions by numerical analyses. Furthermore, the control law is extended to fit an MDOF structural model, and an application example is shown. The computational results show that the NMW control force efficiently reduces structural responses. Copyright © 2000 John Wiley & Sons, Ltd.     

Effects of a Dual‐Pump Crude‐Oil Recovery System,Bemidji, Minnesota,USA

A crude‐oil spill occurred in 1979 when a pipeline burst near Bemidji, MN. In 1998, the pipeline company installed a dual‐pump recovery system designed to remove crude oil remaining in the subsurface at the site. The remediation from 1999 to 2003 resulted in removal of about 115,000 L of crude oil, representing between 36% and 41% of the volume of oil (280,000 to 316,000 L) estimated to be present in 1998. Effects of the 1999 to 2003 remediation on the dissolved plume were evaluated using measurements of oil thicknesses in wells plus measurements of dissolved oxygen in groundwater. Although the recovery system decreased oil thicknesses in the immediate vicinity of the remediation wells, average oil thicknesses measured in wells were largely unaffected. Dissolved‐oxygen measurements indicate that a secondary plume was caused by disposal of the pumped water in an upgradient infiltration gallery; this plume expanded rapidly immediately following the start of the remediation in 1999. The result was expansion of the anoxic zone of groundwater upgradient and beneath the existing natural attenuation plume. Oil‐phase recovery at this site was shown to be challenging, and considerable volumes of mobile and entrapped oil remain in the subsurface despite remediation efforts.     

DyeLIF™: A New Direct‐Push Laser‐Induced Fluorescence Sensor System for Chlorinated Solvent DNAPL and Other Non‐Naturally Fluorescing NAPLs

DyeLIF? is a new version of laser‐induced fluorescence (LIF) for high‐resolution three‐dimensional subsurface mapping of nonaqueous phase liquids (NAPLs) in the subsurface. DyeLIF eliminates the requirement that the NAPL contains native fluorophores (such as those that occur in compounds like polynuclear aromatic hydrocarbons [PAHs]) and can therefore be used to detect chlorinated solvents and other nonfluorescing NAPLs that had previously been undetectable with conventional LIF tools. With DyeLIF, an aqueous solution of water and nontoxic hydrophobic dye is continuously injected ahead of the sapphire detection window while the LIF probe is being advanced in the subsurface. If soil containing NAPL is penetrated, the injected dye solvates into the NAPL within a few milliseconds, creating strong fluorescence that is transmitted via fiber‐optic filaments to aboveground optical sensors. A detailed field evaluation of the novel DyeLIF technology was performed at a contaminated industrial site in Lowell, Massachusetts, USA where chlorinated solvent dense nonaqueous phase liquid (DNAPL) persists below the water table in sandy sediments. Continuously cored boreholes were drilled adjacent to 5 of 30 DyeLIF probes that were advanced at that site. The cores were subsampled in high resolution to generate discrete‐depth soil samples as splits at the same depths where DNAPL was detected in the colocated DyeLIF probes. The cores were analyzed above ground using (1) colorimetric screening using hydrophobic dye tests, (2) laboratory extraction and quantitative chemical analysis, (3) “Benchtop” DyeLIF, and (4) volumetric moisture content. Correlation between DyeLIF and aboveground analyses of the soil cores was excellent: 98% agreement with positive DNAPL detections in samples where DNAPL pore saturations were >0.7% (based on quantitative soil analyses) and the ex situ tests. DyeLIF produced the equivalent of one aboveground colorimetric dye test every 0.2 inch (0.5 cm) of probing. With average daily probing of 395 linear feet (120.4 m), this was the equivalent of 12,039 discrete‐depth colorimetric dye tests/day. Because DyeLIF is an in situ measurement, there are no issues with soil core recovery like there would be for conventional ex situ colorimetric dye tests and 100% characterization of the probed intervals is achieved. Tracking the injection rate and pressure of the dye solution provides simultaneous data regarding relative soil permeability, similar to other direct push (DP) hydraulic profiling tools. Conventional LIF is considered the premier DP tool to identify and map NAPL containing PAHs in the subsurface or confirm its absence. While chlorinated solvent DNAPLs at some field sites contain impurities (e.g., solvated greases or oils) that make them detectable with conventional LIF techniques, at other sites, the DNAPL cannot be detected with conventional LIF. At such sites, the injection of a hydrophobic dye ahead of the sapphire window with the DyeLIF system now makes the LIF technology applicable to the many types of NAPLs that were previously invisible using conventional LIF techniques.     

Closed‐form aftershock reliability of damage‐cumulating elastic‐perfectly‐plastic systems

Major earthquakes (i.e., mainshocks) typically trigger a sequence of lower magnitude events clustered both in time and space. Recent advances of seismic hazard analysis stochastically model aftershock occurrence (given the main event) as a nonhomogeneous Poisson process with rate that decays in time as a negative power law. Risk management in the post‐event emergency phase has to deal with this short‐term seismicity. In fact, because the structural systems of interest might have suffered some damage in the mainshock, possibly worsened by damaging aftershocks, the failure risk may be large until the intensity of the sequence reduces or the structure is repaired. At the state‐of‐the‐art, the quantitative assessment of aftershock risk is aimed at building tagging, that is, to regulate occupancy. The study, on the basis of age‐dependent stochastic processes, derived closed‐form approximations for the aftershock reliability of simple nonevolutionary elastic‐perfectly‐plastic damage‐cumulating systems, conditional on different information about the structure. Results show that, in the case hypotheses apply, the developed models may represent a basis for handy tools enabling risk‐informed tagging by stakeholders and decision makers. Copyright © 2013 John Wiley & Sons, Ltd.     

Stratigraphy of the mid‐ to upper‐Cretaceous System in the Aridagawa area,Wakayama, Southwest Japan

The litho‐ and biostratigraphy of the mid‐ to upper‐Cretaceous System around the Yagumaike Pond in the Aridagawa area, Wakayama, Southwest Japan, were investigated. Many Middle to Late Albian megafossils were found in the strata of a block bounded by faults. It was also revealed that the Upper Cretaceous System of other blocks ranges from the Middle Turonian to Santonian. The Albian megafossil assemblage contains few benthic organisms, in contrast with the abundance of nektons found (e.g. cephalopods). Sedimentological observations of the mudstone profiles also indicate that scarcely or weakly bioturbated, well‐laminated mudstone is dominant among the Albian deposits. These results suggest deposition of the Albian mudstone under a dysaerobic to anoxic environment. It is comparable to the extended oceanic anoxia (OAEs) in mid‐Cretaceous time. Albian deposits with similar characteristics are also known to exist in Shikoku, Southwest Japan. A wide sedimentary basin that was directly affected by global environmental events, such as OAEs, seemed to be formed on the Chichibu Belt in the Albian. The Upper Cretaceous strata in the study area are extremely thin, similar to the coeval deposits on the Chichibu Belt in Shikoku. It is suggested that the sedimentation rate in the sedimentary basin on the Chichibu Belt was extremely low during early Late Cretaceous time.     

A Triggered Depth‐Dependent Sampling System to Overcome the Carry‐Over Effects of the Membrane Interface Probe

The membrane interface probe (MIP) is widely used for the in situ characterization of volatile organic compounds (VOCs) in the subsurface. A main problem using the MIP system is the carry‐over effect of VOCs during the transport from the point of measurement to the detector using a conventional transfer line. This effect results in compound specific retention times, which is shown in disproportionately high measuring signals after the actual penetration of contaminated zones. In consequence, the lower extent of contamination is not clearly identifiable and may be overestimated. The presented field study presents an evaluation of different methods to overcome the carry‐over effect, especially with regard to the required measurement times that are needed to wait for a complete disappearance of the detector signals before forwarding the probe. This was accomplished by comparing data collected with a MIP system with (1) unheated transfer line and (2) a system including a heated transfer line to data collected with a system using (3) a depth‐dependent triggered sampling behind the membrane including two transfer lines. A comparison with analytical results from soil samples gave a good correlation for all three methods. Furthermore, it could be shown that the use of a heated transfer line has a time improvement of 30% compared to an unheated transfer line while the depth dependent triggered sampling using two separate transfer lines yielded a time improvement of over 90%. These results confirm the benefit of the latter method, particularly for the use in highly contaminated sediments.     

Kinematic characteristics and the influence of reference velocities of phase‐shift‐plus‐interpolation and extended‐split‐step‐Fourier migration methods

The phase‐shift‐plus‐interpolation and extended‐split‐step‐Fourier methods are wavefield‐continuation algorithms for seismic migration imaging. These two methods can be applied to regions with complex geological structures. Based on their unified separable formulas, we show that these two methods have the same kinematic characteristics by using the theory of pseudodifferential operators. Numerical tests on a Marmousi model demonstrate this conclusion. Another important aspect of these two methods is the selection of reference velocities and we explore the influence of the selection of reference velocities by comparing the geometric progression method and the statistical method. We show that the geometric progression method is simple but does not take into account the velocity distribution while the statistical approach is relatively complex but reflects the velocity distribution.     

Post‐Synthesis of Ti‐SBA‐15 in Supercritical CO2‐Ethanol Solution

Ti‐SBA‐15 materials with Ti incorporated into the framework of SBA‐15 and controllable Ti contents were successfully prepared via a post‐treatment route in supercritical CO₂‐ethanol solution, followed by calcination. The resultant Ti‐SBA‐15 materials were characterized by means of different techniques including X‐ray diffraction, X‐ray photoelectron spectroscopy, transmission electron microscopy, IR analysis, and N₂ sorption analysis. It was demonstrated that the resultant materials retained a structure similar to that of the parent SBA‐15, and Ti was incorporated into the framework of SBA‐15. At high Ti content, i.e, Si/Ti = 5:1, a TiO₂ phase formed and was coated onto the inner surface of SBA‐15 in addition to the incorporation of the Ti in the framework. The BET surface areas of the Ti‐SBA‐15 samples decreased with increasing Ti content. The presence of small amounts of H₂O in the reaction medium may have resulted in some TiO₂ nanoparticles being uniformly distributed in the pores of the SBA‐15 accompanying the incorporation of Ti in the SBA‐15 framework.     

Visco‐acoustic prestack reverse‐time migration based on the time‐space domain adaptive high‐order finite‐difference method

It is important to include the viscous effect in seismic numerical modelling and seismic migration due to the ubiquitous viscosity in an actual subsurface medium. Prestack reverse‐time migration (RTM) is currently one of the most accurate methods for seismic imaging. One of the key steps of RTM is wavefield forward and backward extrapolation and how to solve the wave equation fast and accurately is the essence of this process. In this paper, we apply the time‐space domain dispersion‐relation‐based finite‐difference (FD) method for visco‐acoustic wave numerical modelling. Dispersion analysis and numerical modelling results demonstrate that the time‐space domain FD method has great accuracy and can effectively suppress numerical dispersion. Also, we use the time‐space domain FD method to solve the visco‐acoustic wave equation in wavefield extrapolation of RTM and apply the source‐normalized cross‐correlation imaging condition in migration. Improved imaging has been obtained in both synthetic and real data tests. The migration result of the visco‐acoustic wave RTM is clearer and more accurate than that of acoustic wave RTM. In addition, in the process of wavefield forward and backward extrapolation, we adopt adaptive variable‐length spatial operators to compute spatial derivatives to significantly decrease computing costs without reducing the accuracy of the numerical solution.     

Catchment area‐based evaluation of the AMC‐dependent SCS‐CN‐based rainfall–runoff models

Using a large set of rainfall–runoff data from 234 watersheds in the USA, a catchment area‐based evaluation of the modified version of the Mishra and Singh (2002a) model was performed. The model is based on the Soil Conservation Service Curve Number (SCS‐CN) methodology and incorporates the antecedent moisture in computation of direct surface runoff. Comparison with the existing SCS‐CN method showed that the modified version performed better than did the existing one on the data of all seven area‐based groups of watersheds ranging from 0·01 to 310·3 km². Copyright © 2005 John Wiley & Sons, Ltd.     

Shaking‐table tests of a full‐scale single‐story masonry veneer wood‐frame structure

This paper presents the findings of shaking‐table experiments conducted to examine the seismic performance of a full‐scale, one‐story, wood‐framed structure with masonry veneer. The structure was designed and constructed in accordance with current U.S. code provisions. The veneer was attached to the wood backing with two kinds of metal anchors, corrugated ties fastened with 8d nails and rigid ties fastened with #8 screws. The tests have shown that the use of nails to fasten veneer anchors to the wood studs is highly unreliable due to the high variation of the nail extraction capacity, which can be influenced by the moisture content of the wood. Other than this, both the wood frame and the masonry veneer performed well under severe ground motions far exceeding a design level earthquake for Seismic Design Category D. Good performance was observed for the rigid veneer ties, which were attached to the wood studs with screws. The results have shown that the veneer walls parallel to the direction of shaking helped to restrain the motion of the wood structure and therefore should not be simply treated as added mass. The detailing of wood roof diaphragms requires special attention in consideration of the out‐of‐plane inertia force of the veneer that can be transmitted through the top plate of the wood‐stud wall to the rim joist. Copyright © 2010 John Wiley & Sons, Ltd.     

A comparison of snowmelt‐derived streamflow from temperature‐index and modified‐temperature‐index snow models

Reliable estimation of the volume and timing of snowmelt runoff is vital for water supply and flood forecasting in snow‐dominated regions. Snowmelt is often simulated using temperature‐index (TI) models due to their applicability in data‐sparse environments. Previous research has shown that a modified‐TI model, which uses a radiation‐derived proxy temperature instead of air temperature as its surrogate for available energy, can produce more accurate snow‐covered area (SCA) maps than a traditional TI model. However, it is unclear whether the improved SCA maps are associated with improved snow water equivalent (SWE) estimation across the watershed or improved snowmelt‐derived streamflow simulation. This paper evaluates whether a modified‐TI model produces better streamflow estimates than a TI model when they are used within a fully distributed hydrologic model. It further evaluates the performance of the two models when they are calibrated using either point SWE measurements or SCA maps. The Senator Beck Basin in Colorado is used as the study site because its surface is largely bedrock, which reduces the role of infiltration and emphasizes the role of the SWE pattern on streamflow generation. Streamflow is simulated using both models for 6 years. The modified‐TI model produces more accurate streamflow estimates (including flow volume and peak flow rate) than the TI model, likely because the modified‐TI model better reproduces the SWE pattern across the watershed. Both models also produce better performance when calibrated with SCA maps instead of point SWE data, likely because the SCA maps better constrain the space‐time pattern of SWE.     

Least‐squares reverse‐time migration in a matrix‐based formulation

This paper describes least‐squares reverse‐time migration. The method provides the exact adjoint operator pair for solving the linear inverse problem, thereby enhancing the convergence of gradient‐based iterative linear inversion methods. In this formulation, modified source wavelets are used to correct the source signature imprint in the predicted data. Moreover, a roughness constraint is applied to stabilise the inversion and reduce high‐wavenumber artefacts. It is also shown that least‐squares migration implicitly applies a deconvolution imaging condition. Three numerical experiments illustrate that this method is able to produce seismic reflectivity images with higher resolution, more accurate amplitudes, and fewer artefacts than conventional reverse‐time migration. The methodology is currently feasible in 2‐D and can naturally be extended to 3‐D when computational resources become more powerful.     

Image‐domain wavefield tomography with extended common‐image‐point gathers

Waveform inversion is a velocity‐model‐building technique based on full waveforms as the input and seismic wavefields as the information carrier. Conventional waveform inversion is implemented in the data domain. However, similar techniques referred to as image‐domain wavefield tomography can be formulated in the image domain and use a seismic image as the input and seismic wavefields as the information carrier. The objective function for the image‐domain approach is designed to optimize the coherency of reflections in extended common‐image gathers. The function applies a penalty operator to the gathers, thus highlighting image inaccuracies arising from the velocity model error. Minimizing the objective function optimizes the model and improves the image quality. The gradient of the objective function is computed using the adjoint state method in a way similar to that in the analogous data‐domain implementation. We propose an image‐domain velocity‐model building method using extended common‐image‐point space‐ and time‐lag gathers constructed sparsely at reflections in the image. The gathers are effective in reconstructing the velocity model in complex geologic environments and can be used as an economical replacement for conventional common‐image gathers in wave‐equation tomography. A test on the Marmousi model illustrates successful updating of the velocity model using common‐image‐point gathers and resulting improved image quality.     

Evaluation of out‐of‐plane seismic performance of column‐to‐column precast concrete cladding panels in one‐storey industrial buildings

Recent earthquakes in Italy (L'Aquila 2009 and Emilia 2012) highlighted the vulnerability of precast cladding panels, typically associated with a connection system not designed to account for displacement and rotation compatibility between the panels and the supporting structure. Experimental investigations were performed in the past to investigate the in‐plane performance of cladding panels and design recommendations have been made accordingly; however, in the case of out‐of‐plane seismic loads, the load demand is commonly evaluated in the design practice by means of formulations for nonstructural components. This paper summarizes the results obtained from parametric analyses conducted to estimate the out‐of‐plane load demand in column‐to‐column cladding panels typical of one‐storey commercial and industrial buildings. Empirical equations suitable for both new and existing panels are proposed and compared with the design equations given in Eurocode 8 and ASCE 7. The paper also considers the effects of the development of plastic hinges at the column base and of the roof flexibility on the load demand in panel‐to‐column connections. The roof flexibility may generate the torsion of the panels; consequently, an analytical procedure to account for such effects is proposed. Finally, general design recommendations are made.     

A Low‐Cost,In Situ Resistivity and Temperature Monitoring System

We present a low‐cost, reliable method for long‐term in situ autonomous monitoring of subsurface resistivity and temperature in a shallow, moderately heterogeneous subsurface. Probes, to be left in situ, were constructed at relatively low cost with an electrode spacing of 5 cm. Once installed, these were wired to the CR‐1000 Campbell Scientific Inc. datalogger at the surface to electrically image infiltration fronts in the shallow subsurface. This system was constructed and installed in June 2005 to collect apparent resistivity and temperature data from 96 subsurface electrodes set to a pole‐pole resistivity array pattern and 14 thermistors at regular intervals of 30 cm through May of 2008. From these data, a temperature and resistivity relationship was determined within the vadose zone (to a depth of ~1 m) and within the saturated zone (at depths between 1 and 2 m). The high vertical resolution of the data with resistivity measurements on a scale of 5‐cm spacing coupled with surface precipitation measurements taken at 3‐min intervals for a period of roughly 3 years allowed unique observations of infiltration related to seasonal changes. Both the vertical resistivity instrument probes and the data logger system functioned well for the duration of the test period and demonstrated the capability of this low‐cost monitoring system.