The objective of this research was to determine if differential camber of prestressed concrete girders could be reduced by accurate prediction of initial camber at release of prestress. Maturity at prestress transfer was used to calculate modulus of elasticity for predicting camber at release. The research consists of a literature review of maturity methods, testing of a standard concrete mix to determine strength and modulus functions and measurement of girder camber and maturity. Both the Nurse-Saul and the Arrhenius maturity models were evaluated. Maturity relationships were developed for concrete mixes containing Type II and Type III cements. A relationship of modulus as a function of maturity was developed. Seven girders were tested. Camber predictions within 0 to ¼ in. of actual camber were obtained using modulus of elasticity calculated from a maturity based function. Comparison was made between maturity based modulus and standard strength based modulus models. Camber predictions based on modulus calculated based on field cured cylinder strengths were within 0 to ½ in. / Master of Science

The fact that many of the giant hydrocarbon reservoirs, such as the Ghawar field in Saudi Arabia and the Grosmont formation in Alberta, are formed from carbonates make these rocks important research topics. Compressional and shear wave velocities (at 1 MHz) and the quasi-static strains of thirty seven carbonate rock samples were measured as functions of saturating fluid and confining pressure. Furthermore, P- and S-wave velocities of the saturated samples were measured at constant differential pressure of 15 MPa. The quasi-static strains of the samples under jacketed and unjacketed conditions were also simultaneously acquired. The lithology, mineralogy, porosity and pore type and size distribution of each sample were obtained using a combination of thinsection and scanning electron microscopy, helium porosimetry and mercury intrusion porosimetry. Due to the lack of closing microcracks and compliant pores in low porosity samples, the travel times show slight changes with the confining pressure. Whereas the high porosity samples show remarkable reduction of travel time with the increase of confining pressure in both P- and S-wave. The samples show no changes in travel time with increasing confining pressure under constant differential pressure, and this behavior is taken to be representative of full saturation of the sample and hence used as a measure of quality control. The comparisons of Biot, Gassmann, squirt-Biot and squirt-Gassmann model predictions with the measured water saturated velocities show that the squirt mechanism is not active on all the studied samples. Biot mechanism is likely to be the principle dispersion mechanism in these samples. For S-wave velocities, Gassmanns model consistently over-predict the saturated at low pressure and closely fit the measured velocities at high pressure, whereas, Biot model over-predicts the saturated velocities in most of the studied samples. The strains over the horizontal axis are higher than the vertical axis suggesting that the majority of the compliant pores and crack-like pores are oriented almost in direction parallel to the length of the sample. The static bulk modulus is always lower than dynamic one for all measured samples. The measured grain bulk modulus is reasonably close to the bulk modulus of the constituent mineral. / Geophysics

No description available.

Rotator cuff (RC) muscle insertion was previously thought to consist of singular, individual tendons inserting onto predefined areas on the greater and lesser tuberosities. However, more recent publications describe the RC muscle tendons as forming a singular insertion across the tuberosities, consisting of both tendinous and capsular portions. Orthopaedic surgeons are now considering these two layers in their surgical approach and treatment plans; therefore this study aimed to test and compare the elastic modulus and maximum load to failure for both tendinous and capsular layers taken from supraspinatus (SS), infraspinatus (IS) and subscapularis (SC). Fourteen (n = 14) fresh/frozen arms were used in this study. Each RC muscle was reverse dissected and trimmed to a 2 x 2cm strip, which was separated into its two layers, still attached to the humerus. An Instron 1342 with a 1kN load cell was used to place the samples under tensile testing till failure (Newtons/N). Accompanying Integrated Design Tools (IDT) NX8-S2 cameras captured images for full-field strain measurements with the Image Systems TEMA software package through digital image correlation (DIC). SS, IS, and SC tendinous layers yielded higher average elastic moduli readings (72.34 MPa, 67.04 MPa, and 59.61 MPa respectively) compared to their capsular components (27.38 MPa, 32.45 MPa, and 41.49 MPa respectively). Likewise, the tendinous layers for SS, IS and SC all showed higher average loads to failure (252.74 N, 356.27 N and 385.94 N, respectively) when compared to the capsular layers (211.21 N, 168.54 N and 281.74 N, respectively). These biomechanical differences need to be taken into account during surgical repair owing to the fact that, should these layers be repaired as one singular structure, it may place the weaker less elastic, capsular layer under more strain, possibly leading to either re-tear complications or reduced postoperative healing and functionality. Thus, based on the results, it is recommended that surgeons consider and repair each layer independently for better postoperative biomechanical integrity. / Dissertation (MSc)--University of Pretoria, 2019. / Anatomy / MSc / Unrestricted

No description available.

No description available.

Over the last 50 years significant advancements have been made in the southern yellow pine (SYP) forests in the U.S. south. Due to silvicultural changes and large scale reforestation efforts the US south has seen significant increases in standing volume (more than 120% over the period). Landowners that grow SYP plantations largely manage for trees that are harvested to produce dimensional lumber. With the changes in growth patterns it is of interest if there have been any changes in structural properties of the lumber that is produced from timber grown today. Landowners desire confirmation that what they are doing in terms of management is maintaining the quality and strength of lumber that the market demands. This information is critical because timberland owners’ plant and manage trees that will ultimately be brought to market at lumber 25-40 years into the future. In an effort to provide clarity to this topic this dissertation investigates: 1) The extent to which the specific gravity (SG), bending strength (modulus of rupture, MOR), and bending stiffness (modulus of elasticity, MOE) of small clear specimens of SYP have changed, particularly with respect to reduction(s), during the interval from approximately 1965 to 2015. 2) The extent to which the compression parallel to grain and perpendicular to grain strength of small clear specimens of SYP have changed, particularly with respect to reduction(s), during the interval from approximately 1965 to 2015. Use statistical analysis of variance to investigate potential differences among data from a historical 1966 data set, a 2014 in-grade data set, and a 2018 staircase material data set. 3) The nature of the relationship between and among SG, MOE, and MOR of small clear specimens of SYP and how these relationships may have changed, during the interval from approximately 1965 to 2015. Use statistical regression analysis to explore changes to the interrelationships of SG, MOE, and MOR among the three samples, with particular interest toward how these may impact or influence non-destructive evaluation. This work consists of 3 independent chapters using varying appropriate statistical methods and is accompanied by an introduction and conclusion.

This investigation focuses on the production, strength properties, and marketability of a new ultra stiff wood composite. The basis of the examination is to compare strength properties such as, Modulus of Rupture, Modulus of Elasticity, Work to Max Load, and Density with currently available products. The final analysis of the ultra stiff product suggested that this product would compete favorably in today’s market due to the strength properties of the product. Although the current hot-pressing method is not economical for mass production, other ways of pressing can be utilized. It is noted in this research that the wood moisture content can influence MOE, MOR, and density properties. By manipulating and controlling the press cycle and the moisture content, a competitive product was produced.

Advances in the field of medicine have extended the average human life expectancy worldwide. As a result an increasing number of people will suffer from problems associated with their mineralized tissues and will require orthopedic and dental implants to restore their quality of life. Ideally, implants should have mechanical and structural properties compatible with the original mineralized tissue, and should also promote faster and stronger implant fixation. An improved understanding of the properties of mineralized tissues can help with the improvements of implants. This thesis focuses on improving the understanding of two aspects related to mineralized tissues and implant systems: the mechanical properties of peri-implant bone, and the mechanical, composition and structural properties of dentin and jawbone. Studies have shown that local delivery of alendronate, an anti-osteoporosis drug, enhances new bone formation; however, the effects of the drug on the elastic modulus of new formed bone are unknown. In this study, nanoindentation was used to evaluate and compare the elastic modulus of peri-implant bone with and without the presence of alendronate. To better understand the properties of dentin and jawbone, nanoindentation and qualitative backscattered electron imaging were used to measure their elastic modulus, mineral content and volume fraction, and regression analyses were used to establish correlation between the properties. In this thesis, mineralized tissue samples were collected from an animal study. To study the effects of alendronate on the elastic modulus of peri-implant bone, porous tantalum implants with three different coating treatments were used: non-coated (Ta), calcium phosphate coated (Ta-CaP), alendronate-immobilized-calcium-phosphate coated (Ta-CaP-ALN). The calcium phosphate coatings, with or without alendronate, increased the elastic modulus of peri-implant Ingrown Bone by approximately 22% (3GPa). The addition of alendronate did not significantly increase the elastic modulus of peri-implant. For the study of dentin and jawbone, regression analyses showed that the elastic modulus of dentin is strongly dependent on the porosity and to a lesser extent on the calcium content. The elastic modulus of jawbone and dentin were compared and the elasticmodulus of jawbone was generally higher than that of dentin while the mineral content was lower.

Laminated glass is comprised of multiple glass plates coupled together in a sandwich construction through the use of a polymorphous interlayer that acts as a bonding agent between the glass plates. Laminated glass offers several advantages over monolithic glass including the ability to resist post fracture collapse, improved sound insulation, lower ultraviolent light trans-mission, and improved thermal insulation. Because the stiffness of the interlayer is often many orders of magnitude less than that of the glass, plane sections prior to loading do not remain plane throughout the laminate?s thickness after load is applied. The behavior of laminated glass is controlled by the stiffness of the interlayer. This behavior rules out the use of classical theoretical formulations for thin plates. In such cases, it is necessary to use specially formulated equations or finite element analyses to evaluate the performance of laminated glass. Previous attempts have been made to develop procedures to quantify the interlayer stiffness for use in laminated glass design. However, there is no widely accepted technique that can be referenced for use. It is known that the interlayer stiffness is a function of both temperature and load duration. The primary objective of this thesis is to formalize a standard procedure to estimate the in situ interlayer shear modulus through the use of nondestructive testing. Physical experiments were carried out on simply supported laminated glass beams subject to three point loading in a temperature controlled environmental testing chamber. Strains and temperatures were recorded as a function of time. These data were used in combination with results from finite element analyses to quantify the variation of the interlayer stiffness as a function of temperature and load duration for a given laminated glass beam. This procedure was applied to three common types of interlayer materials: freshly man-factured polyvinyl butyral (PVB), over a decade old PVB, and freshly manufactured SentryGlas Plus (SGP). Results from these efforts provide specific design guidance for laminated glass that incorporates these interlayer materials. Further, the procedure was applied to various data presented in open literature by previous researchers. In addition, a standardized procedure to estimate interlayer stiffness is provided for the development of additional interlayer properties as required.