bluuebunny/crossref_metadata_2025_split huggingface dataset:
STERDI: An Innovation to Accelerate Remedial Investigations and Engineering
Authors: Waslenchuk D , Man V 
Published: March 2009

The purpose of this paper is to introduce a procedure for remedial investigations and for beginning cleanup more quickly than by traditional approaches. Simultaneous Testing, Exploration, Remedial Design, and Installation (STERDI) speeds the early and mid-phases of the remediation process, eliminates some traditional repetitive steps, and thereby results in lower project costs. The procedure involves the installation of in-ground components of an appropriate remedial system during the same exploration program that delineates the contaminant distribution. The method is built upon two capabilities: (1) planning for the multiple possible contaminant distributions, and (2) conducting “real-time” quantitative chemical analyses of soils during explorations in the vicinity of a release.
To implement STERDI, one has to recognize the various contaminant distributions which may have resulted from the release, prior to conducting subsurface explorations. Several spill “conceptual models” are developed, based on knowledge of the contaminant's geochemical behavior and on local geological characteristics. For each model, a “presumptive remedial design” (involving borehole-installed equipment) is prepared. An exploration program, incorporating in-field chemical analysis, is planned with sequencing which would allow early identification of which set of modeled conditions actually occurs. Once actual conditions are identified, the exploratory boreholes are completed by immediately installing remediation system components, guided by the in-field chemical testing results, according to the presumptive design which was developed for that model prior to the fieldwork.
At a gasoline release, the contaminant distribution was discovered and the in-ground portions of a vapor extraction system, including monitoring wells, were installed, all in a single three-day field effort. At a tetrachloroethylene spill, contamination was found through the unsaturated zone, and within the upper 20 ft (6.1 m) of the 50-ft-deep (15 m) overburden aquifer; a bubbler was installed in an exploratory borehole for remediation, accurately placed just beneath the contaminated interval, all in a two-day effort.
Determination of Water Penetration Resistance of Geotextiles
Authors: Dierickx W 
Published: March 2009

Some woven and nonwoven geotextiles exhibit a resistance to water penetration at initial wetting. This phenomenon is known as ‘Water Head Support’. Tests have been carried out to investigate whether the wetting problem is only an initial problem and whether geotextiles behave in the same way in contact with soil. Therefore drain tubes were wrapped with geotextiles and installed in a sand model. Tests were carried out under various soil conditions (dry and wet) and geotextile conditions (dry and wet).
This resistance to water penetration influences the performance of the geotextile and is disadvantageous compared with geotextiles which do not possess this resistance.
The apparatus described to evaluate the initial resistance to water penetration applies a water head to the geotextile. Tests were carried out for a number of geotextiles. The results revealed that, for some geotextiles, substantially high water heads are reached before the water starts to flow through the geotextile.
Field Performance of Geosynthetic Highway Drainage Systems
Authors: Koerner GR , Koerner RM , Wilson-Fahmy RF 
Published: March 2009

This paper presents field results from a three year study focused on the performance of geosynthetic materials in transportation related drainage applications. The application areas of interest were mainly highway edge drains, although selected retaining wall drains and erosion control systems were also involved. Included in the study are geotextile filters, geocomposite edge drains, geocomposite sheet drains and, to a limited extent, plastic pipe. In many instances, the geotextile was observed to be the key element in the overall success or failure of the system. Thus the geotextile, serving in a primary function as a filter was the major focal point of the investigation.
The paper presents the results of exhuming ninety-one (91) field sites in seventeen (17) states throughout the United States. The results give a clear assessment of geosynthetic drainage systems from a long-term field perspective. Furthermore, it allows for specific recommendations to be made to avoid those situations where problems occurred. In a subsequent paper in these Proceedings the results will ultimately be used to challenge the necessary design formulas currently available for geotextile filters in highway drainage applications.
On the ΔKeff Concept: An Investigation by Means of a Discrete Dislocation Model
Authors: Riemelmoser FO , Pippan R 
Published: March 2009

Some results of discrete dislocation mechanics concerning fatigue crack growth are discussed in two parts. The first part deals with the plasticity-induced crack closure under plane strain conditions. The equations describing the deformation of crack flanks induced by edge dislocations are derived. These equations predict crack face contact for an edge dislocation in the wake of a sharp crack. The principle of superposition then immediately shows that the crack flanks even may contact at blunted cracks. This is visualized first by a suitable choice of the dislocation arrangement and afterwards also by the results of simulations of the dislocation motion at a growing fatigue crack.
In the second part these simulations are investigated more closely. During the initial period of a constant-amplitude test the crack growth increment per loading cycle and the closure stress intensity are monitored. By applying Elber's ΔKeff concept a conceptual crack growth rate is calculated and is compared with the real crack growth increment per loading cycle.
Measurability of Crack Closure
Authors: Pippan R , Riemelmoser FO , Bichler C 
Published: March 2009

Crack closure can be measured either with compliance techniques or by means of crack propagation methods.
Each of these methods has its own specific limitation. We have performed simulations to show that the results of the measurements with compliance technique near the tip depend strongly on the position of the displacement gages and that the compliance curves of the remote clip gages are often too insensitive to detect the near-crack-tip closure.
Apart from the sensitivity of the various methods for measuring near-tip closure there are also problems in determining the effective stress intensity ranges from the load-displacement curves. The different procedures proposed in the literature are discussed, too. It will be shown that the measured stress intensity where the crack physically opens is the parameter which determines the effective stress intensity range. Only in the case of a minute number of contacts with a width very small in relation to the distance to the crack tip does the stress intensity factor, where the contacts open, underestimate the real acting effective stress intensity range at the tip.
Determining Fatigue Crack Opening Loads from Near-Crack-Tip Displacement Measurements
Authors: Riddell WT , Piascik RS , Sutton MA , Zhao W , McNeill SR , Helm JD 
Published: March 2009

The aim of this research was to develop a near-crack-tip measurement method that quantifies crack closure levels in the near-threshold fatigue crack growth regime—a regime where crack closure is not well characterized by remote compliance methods. Further understanding of crack closure mechanics was gained by performing novel crack growth experiments in conjunction with numerical simulations of three-dimensional crack-front propagation. Steady-state (i.e., constant growth rate) fatigue crack growth rates were characterized by performing constant cyclic stress intensity range (ΔK) experiments over a wide range of stress ratios (R). Near-crack-tip (less than 0.3 mm behind) load-versus-displacement measurements were conducted on the specimen surface using a novel noncontact experimental technique (Digital Imaging Displacement System—DIDS).
The experiments and simulations revealed that the three-dimensional aspects of fatigue crack closure must be considered to determine correct opening load levels from near-crack-tip load-versus-displacement data. It was shown that near-crack-front opening levels are nearly constant along the interior portion (greater than 90%) of the crack front, but increase near the free surface. The interior opening load was found to collapse closure-affected data to intrinsic rates, and thus shown to relate to the true crack-front driving force parameter. Surface opening load DIDS measurements made at an optimal distance behind the crack tip were used to correlate da/dN with ΔKeff. Opening load determinations made less than the optimal distance behind the crack tip were shown to be too high to correlate fatigue crack growth rates.
A Unified Elastic-Plastic Model for Fatigue Crack Growth at Notches Including Crack Closure Effects
Authors: Dankert M , Greuling S , Seeger T 
Published: March 2009

The reasons for fatigue failure of many components and subassemblies are internal defects in the material or cracks and the subsequent propagation. Cracks normally originate in areas of stress concentration, e.g., at notches.
It is known that a major factor governing the service life of notched components under cyclic loading is fatigue crack growth in notches. A uniform elastic-plastic crack growth model, based on the J-integral, was developed which especially considers the crack opening and closure behavior for the determination of crack initiation and propagation lives for cracks at elliptical notches under constant or variable-amplitude loading.
For this model, an algorithm for the description of the crack opening and closure behavior and approximation formulas were developed for the determination of the stress intensity factor K and the J-integral for surface, corner and through-thickness cracks at elliptical internal and external notches. The crack growth model will be introduced and its individual modules, as well as the complete concept, were verified by experiments and two- and three-dimensional elastic and elastic-plastic finite-element analyses. Experiments, finite-element analyses, and calculations show excellent correspondence in all aspects.
Description of Crack Growth Using the Strip-Yield Model for Computation of Crack Opening Loads, Crack Tip Stretch, and Strain Rates
Authors: de Koning AU , ten Hoeve HJ , Henriksen TK 
Published: March 2009

Nowadays, application of the strip-yield model for computation of crack opening load levels is well known. In this paper the incremental formulation of a fatigue crack growth law is used to demonstrate the role of the crack opening load level in time-independent fatigue crack growth. Less known is the ability of the strip-yield model to define the strain rate at the crack tip. A threshold level εth of this strain rate is introduced and used to formulate a criterion for initiation of time-dependent accelerated fatigue crack growth. This process is called corrosion fatigue. To account for effects of environment and frequency on the crack growth rate a time-dependent part is added to the incremental fatigue crack growth law. The resulting incremental crack growth equation is integrated to obtain the crack growth rate for a load cycle.
The model discussed in this paper is a mechanical model. Physical aspects other than strain rate, loading frequency and load wave shape are not modeled in an explicit way. Hence, the model is valid for specific environment/base metal combinations. However, in consideration of the effects of small variations of environment, temperature, and other variables on the crack growth rates, it can be used as a reference solution.
The fatigue crack growth model has been implemented in the NASGRO (ESACRACK) software. The time-dependent part is still subject to further evaluation.
In Vitro Endocrine Disruptor Screening
Authors: Soto AM , Michaelson CL , Prechtl NV , Weill BC , Sonnenschein C 
Published: March 2009

Environmental contaminants have been found to produce estrogen-like and androgen-antagonistic effects. It has been hypothesized that environmental estrogens may be playing a role in the decrease of the quantity and quality of human semen, and in the increased incidence of cryptorchidism, and testicular and breast cancer in humans. This hypothesis will require the solution of a series of technical problems before it can be explored. In vitro assays are crucial to accomplish this objective.
The MCF7 cell proliferation assay (E-SCREEN) is the most widely used of the estrogen screens. It is the most sensitive, as it discriminates among agonists and antagonists, and so far, neither false positives nor false negatives have been found among the chemicals screened. Yeast assays do not discriminate among agonists and antagonists. In addition, false negatives have been reported.
The androgen screen (A-SCREEN) assay measures cell proliferation. Alternative assays based on the expression of stable transfected reporter genes are being developed. The only limitation of in vitro/in culture assays is that they cannot detect most prohormones. In order to overcome this limitation, an activation step needs to be developed.
Effect of Test Conditions on the Toxicity of Copper to Juvenile Unionid Mussels
Authors: Keller AE , Ruessler DS , Kernaghan NJ 
Published: March 2009

During the past twnety years, unionid mussels have declined in both abundance and diversity throughout the eastern United States. As a result, there has been an increased call to evaluate the toxicity of various pollutants to unionids in an attempt to separate habitat-caused losses from those precipitated by aquatic contaminants. Few toxicity data for unionids were available until recently because unionids are not easily cultured and no test method had been developed for these animals. Therefore, water quality criteria developed by the USEPA in the 1970s and 1980s were derived from data lacking any information on unionid mussel sensitivities.
The Tennessee Valley Authority (TVA) has advocated the use of a 9-day toxicity test method its scientists developed in the late 1980s. This method, which requires the use of silt, an algal mixture for food and daily changes of water, is not only more labor intensive, it also introduces sources of variation with the use of silt and algae, as well as being substantially different from the standard 96-h fathead minnow or Zooplankton tests. The evaluation of TVA's suggested test conditions (24 h darkness, 800 mg/L silt and algal food) indicated that the use of a 16L:8D light regime, with or without silt or algae did not result in a change in the toxicity of dissolved copper to juvenile Utterbackia imbecillis mussels compared to that recorded using TVA's test conditions.
Impact of Soil Heterogeneity on Measuring the Attainment of PCB Clean-Up Standards
Authors: Phillips IM , Ghirardi JK , Morin JO 
Published: March 2009

The sources of variance in the results of samples collected during a pilot-scale remediation treatability testing for PCBs were evaluated using basic statistical methods. The relative contributions of soil heterogeneity and chemical testing methods were estimated. The sources of variance were estimated using both inter- and intralaboratory testing and the determination of the total variance of each sample set.
It was found that 67 to 94 percent of the variance in the results was contributed by the sample heterogeneity which can not be readily controlled. The results of treated samples from the pilot-scale treatability testing showed a mean concentration of PCBs of 13.6 ppm with a standard deviation of 10.1. The range of the distribution of concentrations was 1.3 to 35 ppm.
Based on these findings, it is inappropriate to use an “absolute” clean-up standard to evaluate whether the clean-up has been achieved. The use of the mean is more appropriate as it takes into account the variance in the results caused by sample heterogeneity.
Staining Potential of Sealants In/On Exterior Wall Substrates
Authors: Chin IR , Gorrell TA , Scheffler MJ 
Published: March 2009

The investigation of dozens of exterior walls on buildings by the authors have revealed that certain sealants used to seal joints in exterior walls have caused the following conditions: 1. Local staining and discoloration of masonry wall substrates due to penetration of sealant into substrates. 2. Local change in absorption of masonry wall substrates due to penetration of sealant into the substrates which results in local discoloration of wall substrates after rains. 3. Surface discoloration of sealant due to dirt accumulation on sealant. 4. Stains in the form of streaks of dirt on masonry and on metal wall substrates due to transfer by rain water of some of the dirt on the sealant surface onto the adjacent surface of the substrate.
Laboratory and field testing of the major commercially available sealants by the authors to date have revealed that silicone sealants have the propensity to stain certain exterior wall substrates while polyurethane sealants do not; that silicone sealants in service discolor more significantly and faster due to dirt accumulation than polyurethane sealants; that sealant that has penetrated into masonry substrates cannot be entirely removed from the substrate by cleaning; and that preconstruction testing of sealants and proper material selection can help to avoid staining of sealant.
Laboratory Testing of Sealants with a Marble Substrate
Authors: Farmer MC , Cechner RA 
Published: March 2009

Polyurethane and silicone sealants are widely specified for installations with porous substrates such as some stones. However, when a sealant is used against such surfaces, there is a potential for a lack of adequate adhesion, or staining of the stone by misapplication or migration of the liquid components of the sealant system, such as primers or plasticizers in the formulation. Some varieties of marble in particular have been reported to be susceptible to staining and discoloration over time from sealants. Application of new sealant over existing sealants is also of great concern for remedial applications. Determining the level of substrate preparation necessary to achieve adequate bond is critical to the success of the remedial construction project.
This paper discusses the development and results of a test program conducted to determine the relative performance of sealants installed on a white marble substrate. The tests performed included wet adhesion tests, accelerated weathering studies, and staining due to plasticizer migration.
Performance-based Adhesion Testing of Structural Sealants
Authors: Cerra AP , Gutowski VS 
Published: March 2009

Existing accelerated laboratory procedures for the assessment of the adhesion of silicone sealants fail to consider the fact that the sealant/substrate interface in a building facade is continuously subjected to a combination of both mechanical and environmental stress. As a result of this, standardised test protocols lack the discrimination necessary to assess relative adhesive behaviour. A novel test procedure is offered which enables improved discrimination of the adhesive strength of the sealant/substrate system. The method is based on the simultaneous application of both mechanical and hydrothermal stress, in order to promote adhesive failure at loads below the cohesive strength of the bulk sealant.
A simpler version of the novel procedure allows for the screening of sealant/substrate combinations that represent potential long-term durability risks. This is achieved by the combination of hydrothermal and mechanical stress at a level close to the structural silicone design stress (0.138 MPa) applied through imposing a 12.5% strain (equal to the normal design strain in silicone sealants) together with immersion of the joint in hot water.
Structural Life Analysis Methods Used on the B-2 Bomber
Authors: Bunch JO , Trammell RT , Tanouye PA 
Published: March 2009

The methods used to predict crack initiation life (durability) and crack growth life (damage tolerance) of the United States Air Force/Northrop Grumman B-2 Bomber are discussed. The test matrix used to verify the methodologies is presented, followed by a discussion of each method and the results of the verification tests.
Durability analysis on the B-2 is based on a notch strain analysis method. The method uses the cyclic stress-strain properties of a material combined with the Neuber equation for strain concentration at a notch to predict crack initiation lifetimes. The method results in a design-allowable curve for durability.
Damage tolerance analyses must account for the effects of crack retardation due to overload cycles in a flight spectrum. The methods used for crack growth analysis rely on empirical parameters that are dependent on material; however, they are also often dependent on the type of spectrum. If the spectrum changes drastically, it is often necessary to recalibrate the crack growth model. A model based on phenomenon of crack closure has been developed that overcomes the need to recalibrate the model for each new spectrum. The model, referred to as the “constant closure model,” was used for crack growth life prediction of metallic components in the B-2. In the constant closure model, the closure factor (CF) is the only empirical parameter. The other parameters needed to use the constant closure model are obtained from the load spectrum.
Further Refinement of a Methodology for Fatigue Life Estimation in Resistance Spot Weld Connections
Authors: Sheppard SD 
Published: March 2009

The overall objective of this research is to develop a general model of fatigue crack propagation in resistance spot-welded joints. An important feature of this development is that the model and accompanying methodology should be accessible to designers evaluating fatigue response of structures containing multiple welds. This objective is achieved by examining the stress state around a resistance spot weld. A general expression for the structural stress around the weld is formulated that is dependent only on the loading immediately surrounding the weld; as such, it is specimen independent.
In previous work [1] it was found that structural stress could be successfully used to estimate life for crack initiation and growth to a length of 0.01 in. (0.254 mm) in resistance spot welds, and that this period represents less than 30% of the total life in as-welded joints. It is important to note that estimation of this period is highly dependent on fatigue-related material properties. In Ref 2 it was shown that structural stress can be related to crack propagation life through linear elastic fracture mechanics. Using the resulting relationship between structural stress and life, life estimations were made for a variety of HSLA steel specimens (e.g., tensile-shear, coach peel) in a number of conditions (e.g., as-welded, prestressed) and were compared with experimentally measured lives. Life estimations were within a factor of 3 of measured lives.
In the current work, the methodology developed in Ref 2 for estimating propagation life is extended by explicitly considering the effects of axial loading and of load ratio on life estimates. In addition, issues related to creating an appropriate finite element model are addressed, and a number of modeling guidelines are established. Total life estimations are made and compare favorably with experimentally measured lives of welds in mild steels in a variety of specimen configurations.