Development of a Non-Gating Guardrail Terminal

Guardrail terminals have evolved to the point where they absorb energy while utilizing tension in the rail to countermand the compression. However, non-gating terminals have yet to be developed. In the present study, the possibility of a non-gating guardrail terminal was investigated. Specifically, the combination of lateral and longitudinal forces that produce non-gating performance were determined from computer simulation. Next, a prototype terminal was crash tested at the research team’s laboratory. A terminal head was designed to deform the guardrail, and its internal structure was adjustable to control the longitudinal force. Posts were designed to control lateral forces by modifying their section modulus. This controlled the force at which the posts buckled in response to a collision. A prototype was subjected to two 15° crash tests using an SUV and a small car. In both tests, the kinetic energy of the test vehicle was fully absorbed and the Manual for Assessing Safety Hardware (MASH) criteria would have been met. Neither vehicle passed beyond the terminal head, making these test results the first of their kind.

Modifying the Gut Microbiome Through Diet or Antibiotics Alters Bone Phenotypes in Older Mice

Objectives Gut microbiota have been shown to influence bone quality and quantity, both risk determinants for osteoporosis. Previous research in young mice showed oral antibiotic treatment during rapid bone gain impaired bone tissue quality. We sought to determine if modifying the gut microbiome of aged mice through diet or antibiotic treatment affects bone geometry and/or strength. Methods A high (HG) or low glycemic (LG) diet was fed in equal amounts to 12-mo. male mice. The diets differed only by starch composition, which was 100% rapidly digested amylopectin in the HG diet or 30% amylopectin/70% amylose in the LG diet. A third group received the LG diet containing antibiotics (ampicillin and neomycin; LGAbx). Feces were collected at baseline and after 10 months of treatment and 16s rRNA sequencing was performed followed by ecological diversity and differential abundance analysis. Femora were harvested after 12 months of treatment for analysis of bone geometry and strength via mechanical testing and imaging. Results Antibiotic treatment reduced alpha diversity, including an average 92% reduction in observed OTUs from baseline compared with 30% reduction in the other groups. Both diet and antibiotic treatment significantly altered taxonomic composition, including an expansion of Proteobacteria in response to antibiotics. Whole bone strength is determined by a combination of the section modulus (the measure of geometry most closely related to bending strength) and the mechanical properties of the bone tissue itself. In HG-fed mice the section modulus was greater than that of the other groups and the bone showed a correspondingly greater strength. However, in LGAbx-fed mice the whole bone strength was 22% lower than bones with similar section modulus in the LG and HG-fed groups, indicating impaired bone tissue material properties. Conclusions Altering diet resulted in significant changes to bone geometry and strength, while changes in the gut microbiota associated with antibiotic treatment resulted in a reduction to bone strength which could not be explained by bone geometry. Our study indicates that dietary or antibiotics treatments applied to mice later in life can alter bone properties, which suggests that interventions to improve bone strength may be effective in older adults. Funding Sources NIH/NIAMS, BrightFocus Foundation, Stanley N. Gershoff Scholarship.

Structural Analysis of a Barge Midship Section Considering the Still Water and Wave Load Effects

Structural failures in the barge midship sections can cause operational delay, sinking, cargo loss and environmental damage. These failures can be generated by the barge and cargo weights, and wave load effects on the midships sections. These load types must be considered in the design of the barge midship sections. Here, we present the structural analysis of a barge midship section that has decreased up to 36.4% of its deck thickness caused by corrosion. This analysis is developed using finite element method (FEM) models that include the barge and cargo weights, and wave load effects. The FEM models regarded three cargo tanks in the midship section, containing the main longitudinal and transverse structural elements. In addition, the hull girder section modulus and the required deck thickness of the barge were calculated using Lloyd’s Register rules. These rules were applied to estimate the permissible bending stresses at deck and bottom plates under sagging and hogging conditions, which agreed well with those of the FEM models. Based on FEM models, the maximum compressive normal stress and von Mises stress of the hull girder structure were 175.54 MPa and 215.53 MPa, respectively. These stress values do not overcome the yield strength (250 MPa) of the barge material, allowing a safe structural behavior of the barge. The structural modeling of the barge midship section can predict its structural behavior under different sagging and hogging conditions, considering the cargo, weight and wave loads.

Effect of 12 months of creatine supplementation and whole-body resistance training on measures of bone, muscle and strength in older males

Background: The combination of creatine supplementation and resistance training (10–12 weeks) has been shown to increase bone mineral content and reduce a urinary indicator of bone resorption in older males compared with placebo. However, the longer-term effects (12 months) of creatine and resistance training on bone mineral density and bone geometric properties in older males is unknown. Aim: To assess the effects of 12 months of creatine supplementation and supervised, whole-body resistance training on bone mineral density, bone geometric properties, muscle accretion, and strength in older males. Methods: Participants were randomized to supplement with creatine ( n = 18, 49–69 years, 0.1 g·kg-1·d-1) or placebo ( n = 20, 49–67 years, 0.1 g·kg-1·d-1) during 12 months of supervised, whole-body resistance training. Results: After 12 months of training, both groups experienced similar changes in bone mineral density and geometry, bone speed of sound, lean tissue and fat mass, muscle thickness, and muscle strength. There was a trend ( p = 0.061) for creatine to increase the section modulus of the narrow part of the femoral neck, an indicator of bone bending strength, compared with placebo. Adverse events did not differ between creatine and placebo. Conclusions: Twelve months of creatine supplementation and supervised, whole-body resistance training had no greater effect on measures of bone, muscle, or strength in older males compared with placebo.

Behavior of Steel Plate Girders with Deep Section under Dynamic Effect

Having a minimum mass, equal-sized flanges and no web stiffeners is the most economical plate girder to fabricate. As with rolled I-sections, for a given section modulus a section with a greater depth will have a lower mass than one with a smaller depth, except in some instances where a thicker web is required in the deeper section. A wider flange plate to resist the buckling tendency may be necessary to use, when the compression flange is laterally unrestrained, but this will add to the cost because of the more difficult assembly procedure. In order to arrive at a minimum-mass cross section as much as possible of the material should be located in the flanges and as little as possible in the web, consistent with shear requirements. There is usually an advantage, however, in using a somewhat thicker web in order to reduce welding distortion, or to avoid the use of or number of stiffeners. It can be shown that for a given web depth to thickness ratio the minimum-mass cross section is that in which the area of the two flanges combined equals that of the web, i.e. 2Af = Aw.An important consideration in cost reduction is the use of preferred plate widths and thicknesses for the flange and web elements.

OR32-05 Lower Oxytocin Levels Are Associated with Lower Bone Mineral Density and Less Favorable Hip Geometry in Hypopituitary Men

Introduction: Hypopituitary patients are at risk for bone loss. Oxytocin (OT) and vasopressin (VP) are hypothalamic-posterior pituitary hormones with opposing actions on bone (anabolic and catabolic, respectively). Whether OT and/or VP contribute to impaired bone homeostasis in hypopituitarism is unknown. Hypothesis: We hypothesized that lower plasma OT and higher VP levels would be associated with lower bone mineral density (BMD) and less favorable hip geometry and estimated strength in men with hypopituitarism. Design: We performed a cross-sectional study of 37 men with hypopituitarism ages 20–60 (mean±SEM 45.8±1.9) years: 20 with anterior pituitary deficiencies only (APD) and 17 with central diabetes insipidus (CDI; marker of posterior pituitary dysfunction), of similar age, body mass index and number of adenohypophyseal deficiencies, on stable hormone replacement. Main outcome measures were fasting plasma OT and VP levels, and dual X-ray absorptiometry-derived BMD (lumbar spine, total hip, femoral neck, distal radius and subtotal body) and hip structural analysis (HSA; cortical thickness, section modulus, and buckling ratio at narrow neck, intertrochanteric region and femoral shaft). All analyses were adjusted for multiple comparisons using Holm-Bonferroni correction. Results: Mean BMD Z-scores were lower at all sites and all HSA parameters at the intertrochanteric region as well as cortical thickness at the femoral shaft were less favorable in those participants who had fasting OT levels below the median than in those with higher levels (P≤0.022). There were no differences in any bone variables at any skeletal site in those with fasting VP levels below vs. above the median (P≥0.232). Lower fasting OT levels were positively associated with (1) lower BMD Z-scores at the lumbar spine, femoral neck, total hip and subtotal body (P≤0.02) and (2) less favorable hip geometry and strength variables (lower cortical thickness, lower section modulus and higher buckling ratio) at the intertrochanteric region in CDI (P≤0.018), but not APD participants (P≥0.458 and P≥0.429, respectively). The associations between OT and bone variables remained significant after adjusting for key determinants of BMD including lean body mass and IGF-1 levels. There were no relationships between plasma VP levels and bone variables in CDI or ADP groups (P≥0.173). Conclusions: OT, but not VP levels, are positively associated with BMD at multiple sites as well as favorable hip geometry and estimated strength in men with hypopituitarism and CDI. Future studies will be important to determine whether OT could be used therapeutically to optimize bone health in patients with hypopituitarism.

Studi Analitik Karakteristik Penampang Baja Profil-I

Paper ini menyajikan hasil studi analitik tentang besaran karakteristik penampang baja profil-I berupa modulus elastis (Sx) dan modulus plastis penampang (Zx). Faktor bentuk penampang, yang merupakan perbandingan nilai Zx terhadap Sx, merupakan besaran utama yang digunakan untuk menghitung kapasitas momen plastis penampang baja. Khusus untuk baja profil-I yang dibuat dengan metoda canai panas, pada bidang pertemuan antara bagian sayap dan bagian badan terdapat bagian penampang seperempat lingkaran cekung yang memberikan kontribusi untuk nilai total besaran karakteristik penampang. Dalam penelitian ini, besaran karakteristik penampang dihitung dan dianalisis dengan menggunakan besaran karakteristik penampang dasar persegi panjang dan lingkaran. Analisa hasil perhitungan menunjukkan bahwa bagian penampang seperempat lingkaran cekung tersebut memberikan kontribusi yang konsisten terhadap nilai luas, modulus elastis dan plastis penampang, yakni dalam rentang sebesar 1.0 – 4,7%. Dari hasil penelitian ini juga diperoleh bahwa faktor bentuk penampang untuk profil-I yang umum digunakan berada dalam rentang nilai 1,102 – 1,147. Perhitungan nilai faktor bentuk penampang dengan dan tanpa mengikutsertakan bagian penampang seperempat lingkaran cekung memberikan hasil yang hampir sama dengan selisih rata-rata sebesar 0,001. Modulus plastis penampang dapat dihitung dengan menggunakan formula sederhana yang diusulkan pada artikel ini dengan tingkat akurasi yang sangat baik dengan deviasi sebesar 1.2 %. Untuk semua jenis ukuran penampang profil-I, formula ini bisa digunakan untuk menghitung modulus plastis penampang secara lebih sederhana. This paper presents the results of an analytical study of the characteristics of the I-profile steel cross-section in the form of elastic modulus (Sx) and plastic section modulus (Zx). The shape factor of the section, which is defined as the ratio of the value of Zx to Sx, is the principal quantity used to calculate the plastic cross-section moment capacity. Specifically for I-profile steels made by the hot-rolled process, in the area of ​​the junction between the flange and the web, there is a concave cross-section that contributes to the total value of the section characteristic. In this study, the magnitude of the cross-sectional characteristics is calculated and analyzed using the magnitude of the basic cross-section characteristics of rectangles and circles. Analysis of the calculation results shows that the cross-section of the concave quarter circle provides a consistent contribution to the area, elastic and plastic section modulus, which is in the range of 1.0 - 4.7%. From the results of this study, it was also found that the shape factor for the I-profile commonly used is in the range of values ​​1.102 - 1.147. Calculation of the cross-section form factor values ​​with and without including the concave quarter circle gives results that are almost the same as the average difference of 0.001. The plastic modulus of the cross-section can be calculated using the simple formula proposed in this article with a very good degree of accuracy with a deviation of 1.2%. For all types of I-profile cross-section sizes, this formula can be used to calculate the plastic section modulus easily.

Bolt Strength in Sectional Body Construction of Valves

ASME B16.34-2017 Section 6.4.2 provides requirements for valves with bolted body joints and threaded body joints. The section states that valves with bodies of sectional construction such that bolted or threaded body joints are subject to piping mechanical loads in addition to the pressure rating for which the valve is designed, shall satisfy the following requirements. For bolted joints, the requirement is a simple formula where the product of pressure rating class designation and ratio of area bounded by the effective outside periphery of a gasket or O-ring or other seal-effective periphery and total effective bolt tensile stress area are less than a certain constant. For bolts of strength less than 137.9 MPa, the value of constant reduces as a multiple of 50.76 times the bolt tensile strength in MPa required or provided in a sectional construction. Section 6.4.3 cautions that the minimum requirements of ASME B16.34 may fall short in scenarios due to valve design, special gaskets, high temperature service, creep characteristics, etc. This paper reviews and studies this ASME B16.34 requirement, which was triggered by failure of a valve with section body construction in the field. Traditionally, valves have been considered as rigid bodies when analyzing a piping system for stresses, support loads, terminal point loads, and deflections. The rigid modeling assumes that the strength of the valve is much higher than an equivalent straight length of pipe. Some computer programs have a provision that permits modeling the valve as a multiple like three- or four-times pipe section modulus. This paper compares the strength of piping and valves based on inherent valve body thickness, body sectional bolting provided, and strength of the equivalent piping flanges. The paper provides conclusions for the user to be aware of so that pre-emptive actions can be taken when using valves with sectional body construction.