Strength and stiffness of 3-ply industrial bamboo matting

There is a pressing need to develop engineering standards for timber- and other wood-based mats suitable for supporting construction vehicles, etc. In 2018, a group of mat producers and users began discussing a potential grading standard specific to mats. There are large gaps in the literature regarding the performance of the available raw materials as well as bolt-laminated mat systems. This study addresses the issue of determining the strength and stiffness values of a commercially sourced industrial bamboo mat. A total of seven 8 ft × 14 ft (2.44 m × 4.27 m) commercial bamboo mats were cut into 28 billets that were 21.5 in (54.6 cm) in width. The bamboo mat billets were evaluated for bending stiffness (modulus of elasticity [MOE]) and strength (modulus of rupture [MOR]) using a three-point static bending test. The 5th percentile non-parametric tolerance limit (5% NTL) and design value for fiber stress in bending (Fb) were calculated. The mechanical property values measured for the 3-ply bamboo mat were at least 25% less than values reported for mixed hardwood timber mats. This type of structural performance information is helpful and useful in the development of matting standards, as it describes the minimum performance characteristics for this type of composite matting.

Regional Left Ventricular Fiber Stress Analysis for Cardiac Resynchronization Therapy Response.

Cardiac resynchronization therapy (CRT) is an effective treatment for a subgroup of heart failure patients, but more than 30 % of those selected do not respond. Inadequate criteria for patient selection and optimization are the main causes of the high non-response rate. Mechanical parameters, such as work done during the isovolumetric phase, are promising, but are complicated and require invasive measurements. In this study, we use a computational modeling framework to calculate the regional stress of the left ventricular wall of seven CRT patients and seven healthy controls. The standard deviation of the regional wall stress at the time of mitral valve closure (SD_MVC) was used to quantify dyssynchrony and was compared between patients and controls and among the patients. The results show that SD_MVC is significantly lower in controls compared to patients and correlated with the degree of long-term response among the patients based on end-diastolic volume reduction. The patients with lower SD_MVC responded best to therapy. The patient with the highest SD_MVC was the only non-responder in the cohort. The distribution of fiber stress at the beginning of the isovolumetric phase seems to correlate with the degree of response and this parameter could potentially improve patient selection and optimization of CRT. Further studies with a larger cohort are needed to validate these results.

Cyclic strengthening of lake ice

Further to systematic experiments on the flexural strength of laboratory-grown, fresh water ice loaded cyclically, this paper describes results from new experiments of the same kind on lake ice harvested in Svalbard. The experiments were conducted at −12 °C, 0.1 Hz frequency and outer-fiber stress in the range from ~ 0.1 to ~ 0.7 MPa. The results suggest that the flexural strength increases linearly with stress amplitude, similar to the behavior of laboratory-grown ice.

Strength and stiffness of 8-inch deep mixed hardwood composite timber mats

There is a current and pressing need to develop engineering standards for timber- and other wood-based mats. In 2018 a group of mat producers and users began discussing a potential grading specification standard specific to mats. There are large gaps in the literature regarding the performance of the available raw materials as well as bolt-laminated mat systems. This work represents a novel attempt to begin to assess the mechanical properties of timber mats. Eight-inch deep mixed hardwood timbers were graded according to an experimental specification standard. Then, they were drilled and bolt laminated into 28 three-timber composite mats that were 24 inches (60.96 cm) in width. The bending stiffness (modulus of elasticity [MOE]) and strength (modulus of rupture [MOR]) performance were evaluated with a static bending test. The 5th percentile nonparametric tolerance limit (5% NTL) and design value for fiber stress in bending (Fb) were calculated. The nonparametric design value compared favorably with that of graded timbers, as described in the 2018 National Design Specification (NDS) for wood.

Glass Fiber Stress-Corrosion Setup: Selection of a Polymeric Coating Material for the Pushing Rod

Various polymers were tested for leaching of ions via High Resolution Induced Coupled Plasma Mass Spectrometry (HR-ICP-MS) in order to determine which coating materials for the pushing rod are compatible with the glass fiber stress-corrosion setup. The biggest concern is the leaching of Si ions, and is compared among various commercially available polymers - four different polyurethanes, polyvinylchloride, poly(methylmethacrylate) and silicone. Significant amounts of other elements leached were also noted and reported.

Glass Fiber Stress-Corrosion Setup: Selection of a Polymeric Coating Material for the Pushing Rod

Various polymers were tested for leaching of ions via High Resolution Induced Coupled Plasma Mass Spectrometry (HR-ICP-MS) in order to determine which coating materials for the pushing rod are compatible with the glass fiber stress-corrosion setup. The biggest concern is the leaching of Si ions, and is compared among various commercially available polymers - four different polyurethanes, polyvinylchloride, poly(methylmethacrylate) and silicone. Significant amounts of other elements leached were also noted and reported.

Mapping Thyroarytenoid and Cricothyroid Activations to Postural and Acoustic Features in a Fiber-Gel Model of the Vocal Folds

Any specific vowel sound that humans produce can be represented in terms of four perceptual features in addition to the vowel category. They are pitch, loudness, brightness, and roughness. Corresponding acoustic features chosen here are fundamental frequency (fo), sound pressure level (SPL), normalized spectral centroid (NSC), and approximate entropy (ApEn). In this study, thyroarytenoid (TA) and cricothyroid (CT) activations were varied computationally to study their relationship with these four specific acoustic features. Additionally, postural and material property variables such as vocal fold length (L) and fiber stress (σ) in the three vocal fold tissue layers were also calculated. A fiber-gel finite element model developed at National Center for Voice and Speech was used for this purpose. Muscle activation plots were generated to obtain the dependency of postural and acoustic features on TA and CT muscle activations. These relationships were compared against data obtained from previous in vivo human larynx studies and from canine laryngeal studies. General trends are that fo and SPL increase with CT activation, while NSC decreases when CT activation is raised above 20%. With TA activation, acoustic features have no uniform trends, except SPL increases uniformly with TA if there is a co-variation with CT activation. Trends for postural variables and material properties are also discussed in terms of activation levels.

Cardiac remodeling in aortic and mitral valve disease: a simulation study with clinical validation

Remodeling is an important long-term determinant of cardiac function throughout the progression of heart disease. Numerous biomolecular pathways for mechanosensing and transduction are involved. However, we hypothesize that biomechanical factors alone can explain changes in myocardial volume and chamber size in valve disease. A validated model of the human vasculature and the four cardiac chambers was used to simulate aortic stenosis, mitral regurgitation, and aortic regurgitation. Remodeling was simulated with adaptive feedback preserving myocardial fiber stress and wall shear stress in all four cardiac chambers. Briefly, the model used myocardial fiber stress to determine wall thickness and cardiac chamber wall shear stress to determine chamber volume. Aortic stenosis resulted in the development of concentric left ventricular hypertrophy. Aortic and mitral regurgitation resulted in eccentric remodeling and eccentric hypertrophy, with more pronounced hypertrophy for aortic regurgitation. Comparisons with published clinical data showed the same direction and similar magnitudes of changes in end-diastolic volume index and left ventricular diameters. Changes in myocardial wall volume and wall thickness were within a realistic range in both stenotic and regurgitant valvular disease. Simulations of remodeling in left-sided valvular disease support, in both a qualitative and quantitative manner, that left ventricular chamber size and hypertrophy are primarily determined by preservation of wall shear stress and myocardial fiber stress. NEW & NOTEWORTHY Cardiovascular simulations with adaptive feedback that normalizes wall shear stress and fiber stress in the cardiac chambers could predict, in a quantitative and qualitative manner, remodeling patterns seen in patients with left-sided valvular disease. This highlights how mechanical stress remains a fundamental aspect of cardiac remodeling. This in silico study validated with clinical data paves the way for future patient-specific predictions of remodeling in valvular disease.

EFFECT OF EARTHQUAKE LOAD ON THE STRUCTURE OF THE HIGHWAY BRIDGE WITH I-GIRDER PRESTRESSED CONCRETE IN THE EVENT OF INACCURACIES IN PRESTRESSING LOSS PREDICTIONS

In planning a highway bridge girder using prestressed concrete, it must pay attention to two design categories, namely strength and service. Problems have arisen since the existence of earthquake resistance regulations for road bridges, so planners must calculate the amount of deflection and stress that occurs in the upper structure due to earthquake loads, which must be smaller than the deflection and voltage permits required by regulations. All of that was also greatly influenced by the accuracy of the predicted loss losses for prestressed concrete girders. The purpose of this study was to conduct a study which could be a solution for how to actually treat a good design, for the I-Girder design of prestressed concrete used as a highway bridge girder in the event of inaccurate prediction of loss of pressure during an earthquake, resulting in two design categories strength and service ability can be considered all well. The methodology of this study is to make as a starting point the prestressed concrete I girder whose dimensions are capable of being a highway bridge girder with a span of 30 m to 40 meters with standard loading for loading BM 100. For span bridges that have 100% prediction accuracy, use as a basic benchmark of deflection and stress values that occur for the type of combination of loads that have earthquake loads, then with the same span, varied values of inaccurate predictions lose pre-stress and analyzed deflection and stress values that occur for types of load combinations that have earthquake loads varied earthquake regions 1,2, 3 and 4, for medium soil types. The results of the study show that the greater the percentage of inaccurate prediction of loss of pressure, the greater the deviation ratio of deviations both deflection, upper fiber stress and lower fiber stress occur in the field. Which, if the prediction of losing pre-pressures is smaller than the actual one, then the level of the deviation ratio of the allowable deviation increases as well as vice versa. Also, predicting pre-suppression voltage loss that is located on the side greater than the actual loss of pressure that occurs will be on the part of the party that is harmful to the ability of service and the permissible power, when an earthquake occurs.