Reliability-Based Modeling of Bridge Deterioration Hazards

This paper presents the results from a study on the deterioration patterns of highway bridges, using estimated sojourn times of bridge components in various deterioration states (condition). With emphasis on the age that the bridge leaves a specified threshold condition state, the uncertainties in the estimated times are best fitted as Weibull probability distribution functions. Using both complete observations’ data and the right-censored data from a 13-year span condition historical data for the bridges, the maximum likelihood estimates are obtained for parameters of the fitted distributions, and reliability analyses are conducted for the various categories of bridges, by the type of roadways carried (interstate, noninterstate, and local roads), and the material type, i.e., cast-in-place concrete decks; prestressed concrete superstructures; steel superstructures, etc. The survival and hazard functions are developed and interpreted, including a combination of the deterioration hazard functions with the hazard functions of the effects of hurricane winds. It was observed that all the bridge categories deteriorated faster with age (nonexponential times), and bridge components located on the interstate roadways are deteriorating faster than similar bridges on noninterstate roadways. Asset worth of bridges are indicated, based on the reliability estimates.     

Efficiency of fractionated γ-irradiation doses to eliminate vegetative cells and spores of Bacillus cereus from raw rice

Efficacy of fractionated γ-irradiation to eliminate vegetative and spore forms of Bacillus cereus from raw rice was studied. Viable bacteria and spores count performed after irradiation treatment revealed that vegetative cells and spores (7.9 and 7.7 log CFU/g) of B. cereus in raw rice tolerated γ-irradiation up to 10 and 20 kGy, respectively and were eliminated at 15 and 25 kGy respectively on single treatment. Exactly 2 times of 5 kGy irradiation treatment eliminated all vegetative B. cereus (7.9 log CFU/g). A treatment with fractionated doses of γ-irradiation effectively eliminated vegetative bacteria but not spores of B. cereus. Field emission SEM images revealed the damage by γ-irradiation to the spore exosporium. This study suggests new approach of using fractionated doses of γ-irradiation to eliminate foodborne pathogens in food which are affected by high doses of γ-irradiation.     

Multicriteria DSS with Historical Database for Attenuator Selection

A computerized information system has been developed for the management of field data on vehicle impacts with crash attenuators. The system has been developed for an intranet platform with a Java-based interface. A central Oracle database contains a variety of data describing site conditions, maintenance history, and accident characteristics. Several standard reports can be generated, summarizing attenuator usage, life-cycle costs, and accident outcomes under a variety of site or crash conditions. In addition, a multicriteria decision support system uses historical data to rank attenuators based on their past performance under specific site conditions. This application supports the design and selection of attenuators for new locations; it can also be used to analyze current placement recommendations for common scenarios. Use of the system will allow highway safety personnel to better understand the performance and applicability of various types of crash attenuators. Further, the research extends the concept of a decision hierarchy by: (1) using deterministic and heuristic importance functions to vary the weights to reflect changes in site conditions; and (2) using a possibilistic matching algorithm to include historical data that partially matches the user-input site characteristics in the performance evaluations.     

Behavior of Structural Composite Lumber T-Beam Bridge Girders after Fatigue Loading

Recent innovation in the engineered wood industry has produced structural composite lumber (SCL) that achieves excellent strength, stiffness, and efficient use of wood. Product variations of SCL, such as laminated veneer lumber (LVL) and parallel strand lumber (PSL), are currently being used in transportation to produce bridge girders and decks for rural and other low traffic volume roads. Although the elastic and shear properties of SCL are available, no attempt has been made to estimate the fatigue performance of bridge girders. This study tested 12 new and 2 old, weathered SCL T-beam bridge girders with material and preservative variations for AASHTO-specified flexural fatigue under a stress-controlled test setup simulating 60?years of service. Transverse posttension was applied to the girders simulating a real-life situation. Results from the study indicate that the girders are capable of withstanding the repetitive loads without much physical damage. A few of the LVL girders had severe delamination at the SCL-epoxy interface. The fatigued girders were loaded statically up to failure and compared with the ultimate flexural strength of fresh girders. The girders did not show any appreciable strength loss because of one million cycles of fatigue loading. There was no effect of SCL type and preservative treatment on fatigue strength.     

Production of Coturnix quail immunoglobulins Y (IgYs) against Vibrio parahaemolyticus and Vibrio vulnificus

Production of chicken immunoglobulins Y (IgYs) and their applications in prophylactic, therapeutic, detection of microbial contaminants and as a diagnostic tool has been widely studied with limited information from other avians. This study produced Coturnix quail (Coturnix coturnix japonica) egg yolk IgYs against Vibrio parahaemolyticus and Vibrio vulnificus. Formalin inactivated (FIVP, FIVV, mixed FI-VP/VV) and heat inactivated (HIVP, HIVV, mixed HI-VP/VV) Vibrio immunogens (10⁹ CFU/mL) were intramuscularly immunized into quail through thigh muscles. Egg yolk IgY was purified by water dilution-ammonium sulfate precipitation method and the activity was determined by enzyme-linked immunosorbent assay (ELISA). Formalin inactivated immunogens induced high humoral immune response for both V. parahaemolyticus and V. vulnificus over heat inactivated immunogens. However, IgYs resulted from HIVP and FIVV immunogens, showed high specificity to V. parahaemolyticus and V. vulnificus respectively. Detection limits of the indirect ELISA using the produced IgYs were 10⁵ CFU/mL for V. parahaemolyticus and 10⁶ CFU/mL for V. vulnificus. The developed antibodies showed high binding affinity to their corresponding immunogens, very little cross reactivity to Staphylococcus aureus and not other bacteria strains (p<0.05), a phenomenon which was also observed in Western blot.     

Resistance of Bacillus cereus and its enterotoxin genes in ready-to-eat foods to γ-irradiation

This study was investigated the resistance of Bacillus cereus ATCC 13752 and its enterotoxin coding genes in cereals, vegetables, and tryptic soy broth to γ-irradiation. Screening for enterotoxin coding genes, viability test, PCR analysis, measurement of DNA concentration, cellular constituents release, SEM, and antibiotic sensitivity tests were performed after irradiation at 0, 1.5, 3, 5, 7, 10, and 15 kGy. Thirty % of strains screened possessed all enterotoxins genes. At 10 kGy B. cereus viable cell count was reduced by 4 logCFU/mL. B. cereus in vegetables and broth demonstrated higher susceptibility than those in cereals. Enterotoxins coding genes could be identified in the γ-irradiated cells, antibiotic sensitivity profile was not affected. Concentration of DNA containing enterotoxin coding genes was reduced and release of cellular constituent was highest at 15 kGy. γ-Irradiation up to 10 kGy did not eliminate B. cereus neither affected their enterotoxins coding genes from ready-to-eat food.     

Sky temperature modelisation and applications in building simulation

The sky temperature is an important parameter for simulation codes in building studies. A preliminary campaign of validation of a simulation software CODYRUN has demonstrated the misinterpretation of the radiative exchanges of long waves between the building and its environment. A bibliographical research has then led to the use models using dry air temperature to estimate sky temperature. However, these models has not been completely satisfactory as far as night clear sky are concerned. In this case, sky temperature remains overestimated. A research of a non linear model has been undertaken, leading to the use of neural networks with satisfactory results. Sky temperature is then calculated and reinjected into the simulation code. Comparison between simulated temperature and measures has turned to be acceptable.     

Effect of Grouting Pressure in Posttensioned Bulbtee Girders

Out-of-plane stresses due to the wedging effect of the strands caused high stress concentration at the end of the transition zone of Florida bulbtee girders. Adding the hydrostatic stresses due to grout pressure in the posttensioning ducts severed the tensile stresses in the web section and caused some crack initiation between the ducts and on the surface of the girders. Other related factors were found to contribute to these stresses. Among these factors were the shape of the posttensioning ducts, and the type of the duct material. Two fully instrumented 22.9-m-long Florida bulbtee end girders were prepared and tested under typical field conditions. Testing results indicated that stress accumulation due to the grout pressure was more severe in ducts with oval cross sections than in the round ones. Although steel ducts were used in the full-scale field testing, a comparative study using 3D nonlinear finite-element analyses showed that cracking was even more severe when using high-density polyethylene ducts.     

Occurrence of patulin in various fruit juices from South Korea: An exposure assessment

To determine patulin in various fruit juices, high performance liquid chromatography (HPLC) method was optimized and validated. For validation of HPLC method, a linearity, accuracy, precision, detection limit, and quantification limit were determined. Linearity (R² = 0.99995), accuracy (96.1–115.7%), precision (3.31–9.52), detection limit (6 ng/mL), and quantification limit (8 ng/mL) were in agreement with performance criteria for patulin as set by the European Commission hence proved that HPLC can be used to detect patulin in fruit juices. After validation, the method was applied to estimate the prevalence of patulin in fruit juices (apple, grape, and orange juices). Nine samples (12.5%, 3 apple, 2 orange, and 4 grape juices) of 72 samples were positive for patulin in the range 2.8 to 30.9 ng/mL. According to the monitoring results, daily intake was estimated to be 0.17 ng/kg BW/day which was lower than the provisional maximum tolerable daily intake (0.4 μg/kg) established by Joint Expert Committee on Food Additives. These results indicate that the detection method coincides with the performance criteria and is appropriate for analysis of patulin, and continuous monitoring of patulin in various fruit juices from Korea is necessary.     

Applications of Mathematical Software Packages in Structural Engineering Education and Practice

The use of mathematical software packages provides a number of benefits to an engineering user. In general, the packages provide a platform that supports iterative design and parametric analysis through a flexible, transparent interface combined with extensive computing power. This enables an engineering user to develop design equations that are based on fundamental mechanics theories, rather than relying on the “black-box” approach of most commercial design packages. As an example, a closed-form solution for obtaining effective length factors for the design of stepped columns is presented. In the example a series of formula is used to demonstrate the transparency of Mathcad, including the ability of using real engineering units in the calculations, formulas as they may appear in textbooks or in codes, and ability to hide and password protect some areas. This facilitates easier automation of the design and design checking processes. Most commercial structural design packages can be classified as black-box packages. The analyst inputs data at one end only to receive results at the other without fully appreciating the process the input data have gone through. This phenomenon has the tendency of reducing the engineer to a technician, blindly implementing the ideas of the software designer. The Mathcad package discussed in this paper and similar mathematical packages returns the engineer to being in control of the design process.