Experimental and Analytical Investigation of Live-Load Distribution Factors for Double Tee Bridges

Torsion-induced failure of a reinforced thermoplastic pipe used in a gas lift system

The efficiency of external strengthening using CFRP (Carbon Fiber Reinforced Polymer) sheets to rehabilitate corrosion-defected RC (Reinforced Concrete) beam–column members is experimentally studied. ALL specimens were tested under a combined axial force and transverse load until failure. The axial forces were applied with two levels either 25% or 50% of the ultimate design load of control specimen. The accelerated corrosion process was used to get steel reinforcement corrosion inside the concrete at three levels, 0% and approximately 5% and 20%, according to Faraday’s law. External strengthening with a CFRP sheet was used in this study to overcome the effect of deterioration in the mechanical properties of the corroded steel bars. A significant deterioration in the load carrying capacity, stiffness, and serviceability was recorded for corrosion-defected specimens. The increase of the axial force was recorded as a positive effect on the ultimate strength, stiffness, and serviceability of the testing specimens. This effect was clearly evident for the defected specimens, with an increasing corrosion level, by decreasing the adverse effects of corrosion. The external strengthening with a CFRP sheet restored the load-carrying capacity, stiffness, and serviceability to an undamaged state.

IntroductionDental caries is a chronic, infectious, and irreversible disease of the calcified tissues of teeth, which demineralises the inorganic portion and destroys the organic substance of the tooth, which often leads to cavitation. Epidemiological studies measuring the prevalence and severity of dental caries have used modified versions of Klein and colleagues’ decayed, missing, and filled (DMF) or Gruebbel’s decayed, extraction indicated, and filled (def) indexes; however, these indexes only capture cavitated lesions. Saliva plays a vital role in caries prevention; significant reduction or deterioration of salivary function can aggravate the development of dental caries. Saliva affects the incidence of dental caries in four ways: as a mechanical cleansing agent that results in less accumulation of plaque, by reducing enamel solubility using calcium, phosphate, and fluoride, by buffering and neutralising the acids produced by cariogenic organisms, or by introducing directly through diet and by antibacterial activity. The study aims to assess the prevalence of dental caries and salivary parameters such as salivary pH, flow, and buffering capacity in six to 12 years old children of a rural tehsil of Jaipur.Materials and methodsThe study was done on a population consisting of 400 school-going children in the age group of six to 12 years. Oral examination was undertaken by a single examiner, who is the study's principal investigator, to avoid inter-examiner variability. Testing of resting saliva was done for evaluation of visual inspection of the level of hydration, saliva consistency, pH measurement, saliva quantity, and buffering capacity.Statistical analysisThe data were analysed using the chi-square test, t-test, and statistical software SPSS version 17.00 (SPSS Inc., Chicago, IL). The chi-square test was used to compare and analyse qualitative data, whereas the unpaired t-test was used to analyse and compare quantitative data. Quantitative data were summarised as mean and standard deviation. A p-value of 0.001 or less was considered for standard significance.ResultsThere was no significant difference in resting salivary flow rate between children with decayed, missing, and filled teeth (DMFT) scores less than 5 and DMFT scores of 5. The mean buffering capacity of stimulated saliva was found to be significantly more among children with DMFT scores less than 5 than children with DMFT scores of 5 or more. The mean pH of resting saliva was found to be significantly higher among children with DMFT scores less than 5 than children with DMFT scores of 5 or more.ConclusionThe prevalence of caries based on age was maximum in mixed dentition and minimum in primary dentition. In contrast, the difference in severity based on age was maximum in permanent dentition. The prevalence of caries was higher in children whose parents were aware of dental health; the difference was more significant in children with primary and mixed dentition. This study showed that salivary parameters such as salivary flow rate, salivary pH, and salivary buffering capacity among school-going children correlated with the prevalence of caries.

Methods. Comparative effects of placebos and T3 were tested on four euthyroid fibromyalgia patients over a period of nine months. Each patient completed alternately two T3 phases and two placebo phases, the sequence depending on the medication with which each was randomly assigned to begin. The ABAB single subject crossover design enabled each patient to serve as her own control. Phase crossover was response-driven, based on changes in measures of mean tender point sensitivity by algometry, pain distribution by the percentage method, and mean symptom intensity by visual analog scales. Changes were evaluated by visual inspection of graphs and single subject statistical analyses. Traditional group comparison statistics were performed for changes on the Fibromyalgia Impact Questionnaire, the Zung's Depression Scale, and pain distribution according to the ACR criteria. Results. Quantitative analysis of trends of repeated measures across phases showed significant improvement in fibromyalgia status in T3 phases compared to baseline and placebo phases. Testing throughout the 9-month study and at 4-month follow-up showed no clinically significant adverse target tissue effects. No patient met the diagnostic criteria for fibromyalgia by the end of the study. Conclusion. Repeated administration and withdrawal of T3 corresponded to significant improvement and deterioration in fibromyalgia measures during this study. It is highly probable, then, that improvement in fibromyalgia status of our four patients was functionally related to their use of supraphysiologic dosages of T3 (effective range: 118.75-to-162.50 meg). These dosages were shown to be safe at 4-month follow-up. Further testing is necessary to establish long-term safety.

Effects of temperature and pH on the electrochemical behaviour of alloy 600 in simulated pressurized water reactor primary water

Deteriorating effects of lichen and microbial colonization of carbonate building rocks in the Romanesque churches of Segovia (Spain)

The high-temperature environment has a significant deterioration effect on the meso- and macro-physicomechanical properties of rocks. Black sandstone in Chuxiong Yunnan was chosen as the test sample to perform a high-temperature test, a nuclear magnetic resonance (NMR) test, and a uniaxial compressive test (UCT). After high-temperature heating (25°C–1,200°C), the thermally damaged samples were subjected to NMR tests in both saturated and centrifugal states. The transverse relaxation time T2 spectrum distribution and T2 spectrum area were subsequently obtained. The temperature effect of the mesopore structure was investigated by analyzing the changes in porosity. The T2 spectrum cutoff value was determined, and the temperature effect of the movable fluid migration law for rocks was evaluated. The thermal damage constitutive relationship with porosity as the damage variable was determined, and the evolution law of mesopore structure parameters and macroscopic mechanical parameters was discussed. UCT results showed that the mechanical characteristics of black sandstone were obviously degraded by high temperature, and especially the uniaxial compressive strength (UCS) decreased sharply after the temperature exceeded 900°C. NMR results identified 900°C as an inflection point for the mesostructure change. For temperatures lower than 900°C, the improvement of pore connectivity was not obvious. For temperatures exceeding 900°C, the porosity increased rapidly. The porosity had a great influence on UCS, and there was a clear exponential function relationship between the two. The larger the porosity, the smaller the UCS. It showed that it was an effective angle to study the mesopore characteristics and mechanical properties of high-temperature rocks based on the NMR technique.

Civil infrastructure assets' contribution to countries' economic growth is significantly increasing due to the rapid population growth and demands for public services. These civil infrastructures, including roads, bridges, railways, tunnels, dams, residential complexes, and commercial buildings, experience significant deterioration from the surrounding harsh environment. Traditional methods of visual inspection and non-destructive tests are generally undertaken to monitor and evaluate the structural health of the infrastructure. However, these methods lack reliability due to the need for instrumentation calibration and reliance on subjective visual judgments. Digital twin (DT) technology digitally replicates existing infrastructure, offering significant potential for real-time intelligent monitoring and assessment of structural health. This study reviews the existing applications of DTs across various sectors. It proposes an approach for developing DT applications in civil infrastructure, including using the Internet of Things, data acquisition, and modelling, together with the platform requirements and challenges that may be confronted during DT development. This comprehensive review is a state-of-the-art review of advancements and challenges in DT technology for intelligent monitoring and maintenance of civil infrastructure.

A sleeve-shaped fire shield that operates inside one of two burner trains in an oil and gas processing unit ruptured after 15 y of service. A detailed analysis was conducted to determine how and why the sleeve failed. The investigation included visual inspection, chemical and gas analysis, mechanical property testing, stereomicroscopy, and metallographic examination. The fire sleeves are fabricated from 3-mm thick plate made of Incoloy 800 rolled into 540-mm diam sections welded along the seam. Three such sections are joined together by circumferential welds to form a single 2.8 m sleeve. The findings from the investigation indicated that internal oxidation corrosion, driven by high temperatures, was the primary cause of failure. Prolonged exposure to temperatures up to 760 °C resulted in sensitization of the material, making it vulnerable to grain boundary attack. This led to significant deterioration of the grain boundaries, causing extensive grain loss (grain dropping) and the subsequent thinning of sleeve walls. Prior to failure, some portions of the sleeve were only 1.6 mm thick, nearly half their original thickness.