Evaluation of bridge component design and construction techniques: A look at integral abutment bridge precast approach slabs and post grouted drilled shafts

The bump at the end of the bridge and the high cost of deep embedded drilled shafts have long been recognized by many bridge owners. This research aims to mediate the bump at the end of the bridge and to validate the use of post grouting to increase drilled shaft capacity. Performance monitoring and full scale test programs were used to evaluate these technical issues. The bump at the end of the bridge is typically due to settlement of the approach soils and cracking of the approach pavements. The settlement and cracking in integral abutment bridges are typically dealt with by connecting the approach slab to the integral abutment bridge. Two integral abutment bridges with integrally connected precast approach slabs were evaluated using long-term monitoring systems to study their structural performance and determine the range of forces that should be considered when designing such approach slabs. This study has identified design and construction considerations for integrally connected precast approach slabs. The approach slab study revealed the source and magnitude of forces to be considered in the design and construction of approach slabs integrally connected to integral abutment bridges. Consideration of these forces in the design and construction of such approach slabs could potentially lead to reduced maintenance costs associated with the bump at the end of the bridge. The required deep embedment length of drilled shafts is due to the inability to fully mobilize the end bearing resistance of the shaft before reaching service displacement criteria. Post grouting of drilled shafts can be used to effectively increase the end bearing capacity within service displacement limits, often times allowing the drilled shaft to be shortened without sacrificing capacity. Through a load test program and long-term performance monitoring of production shafts, the increase in capacity and performance of post grouted drilled shafts were investigated. This study has identified design and construction considerations for post grouted drilled shafts. The post grouted drilled shaft study verified the use of post grouting as a technique for increasing the end bearing resistance of drilled shafts and also identified design and construction considerations for post grouted drilled shafts. Increasing the end bearing resistance of drilled shafts through the use of post grouting can effectively allow the shafts to be shortened without losing capacity or exceeding service displacement criteria; potentially leading to reduced costs for bridge projects

A project approach using integration and collaboration to study ancient civilizatons in sixth grade

The purpose of this article is to describe a 6th grade project intended to build responsibility in students for their own learning and develop an integration of curriculum areas through the study of Ancient Civilizations. Within this project, 6th grade students were involved in a research project with the final production of an ancient civilizations museum where they shared their knowledge and taught other students about their chosen civilization

Utilizing the SAFE-T Model and Anti-racist Counseling Principles for Suicide Assessment and Teaching Counselors in Training

Training on suicide assessment and intervention in college counseling centers is crucial. The SAFE-T model is effective when teaching counselors in training (CITs) in training clinics on college campuses as students learn how to assess clients’ suicide risk level. We share how the SAFE-T model, in tandem with anti-racist counselor education practices, can enhance training in programs with training clinics based on our clinic at The Pennsylvania State University, followed by a case study to exemplify how to synthesize both practices for robust clinical outcomes

The superhydrophobicity of polymer surfaces: Recent developments

Superhydrophobicity is the extreme water repellence of highly textured surfaces. The field of superhydrophobicity research has reached a stage where huge numbers of candidate treatments have been proposed and jumps have been made in theoretically describing them. There now seems to be a move to more practical concerns and to considering the demands of individual applications instead of more general cases. With these developments, polymeric surfaces with their huge variety of properties have come to the fore and are fast becoming the material of choice for designing, developing, and producing superhydrophobic surfaces. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1203–1217, 201

Heterogenes Kontaktmodell zur Mischreibungssimulation an Radialgleitlagern aus kurzfaserverstärkten Polymeren

Polymere Komposite finden zunehmend Anwendung in tribologischen Systemen. Durch die spezifische Zugabe von Füll- und Verstärkungsstoffen lassen sich maßgeschneiderte Eigenschaften für ein tribologisches System erzielen. Dabei stellt die virtuelle Auslegung solcher Systeme durch die Inhomogenitäten der Materialeigenschaften auf der Mikroskala eine besondere Herausforderung dar. In der vorliegenden Arbeit wird eine Mischreibungssimulation, welche auf einem isotropen, homogenen, linear-elastischen und temperaturunabhängigen Materialverhalten für metallische Werkstoffe basiert, für polymere Komposite erweitert. In der Simulation erfolgt eine Skalentrennung. Auf der Mikroskala wird auf Rauheitsebene die Kontakt- und Fluidsimulationen durchgeführt. Deren Ergebnisse werden als effektive Eigenschaften auf der Makroskala verwendet. Auf der Makroskala erfolgt eine Mischreibungsberechnung basierend auf einer thermo-elasto-hydrodynamischen Simulation. Als Analyseobjekt dient ein Radialgleitlager mit Stahlwelle und PEEKCF30-Lagerbuchse (Hochtemperaturthermoplast mit 30 Gew.-% Kohlenstoffkurzfaserverstärkung). Auf der Mikroskala wird eine heterogene FEM-Kontaktsimulation mit rauen Oberflächen entwickelt, welche die reale Faserverteilung mit gemessenen Rauheiten überlagert. Durch die heterogene Kontaktsimulation werden signifikant geringere Kontaktsteifigkeiten gegenüber der homogenen Kontaktsimulation basierend auf PEEKCF30-Zugversuchen erreicht, da auf der Mikroskala die Matrixeigenschaften die Kontaktsteifigkeit dominieren. Es stellt sich heraus, dass durch variierende Rauheiten und Faseranteile in der Oberfläche a priori keine generische, effektive, homogene Steifigkeit für die Kontaktsimulation eines heterogenen Materials auf der Mikroskala möglich ist. Das entwickelte Kontaktmodell liefert hierfür einen Lösungsansatz. Die Makroskala wird um thermische Effekte erweitert. Temperaturabhängige Kontaktsteifigkeiten führen bei erhöhten Temperaturen auf der Makroskala zu geringeren Reibungszahlen. Die Berücksichtigung der Temperaturdehnung auf der Makroskala führt zusätzlich zu geringeren Reibungszahlen durch eine Verengung des Schmierspaltes und zu einem qualitativ unterschiedlichen Tragverhalten. Zusätzlich wird auf der Makroskala eine Verschleißsimulation nach einem energetischen Verschleißmodell entwickelt. Die Validierung der Modellerweiterungen am Gleitlagerprüfstand zeigt signifikante Verbesserungen in der Reibungsvorhersage für polymere Werkstoffe. Genauso zeigen die simulierten Verschleißgeometrien eine sehr gute Übereinstimmung mit den gemessenen Geometrien, was auf der realitätsnahen Beschreibung der Kontaktverhältnisse in der Mischreibungssimulation basiert. Schlagwörter: PEEK, Polymer, Gleitlager, Mischreibung, Verschleiß, TEHD-SimulationPolymeric composites gain increasing importance in tribological systems. By the addition of particles or fibers to a polymeric matrix, specific properties for a tribological system can be achieved. Hence, the virtual design of such materials especially on the micro scale is particularly challenging. In this work, a mixed lubrication simulation based on isotropic, homogeneous, linear elastic and temperature independent material behavior is extended for polymeric composites. The simulation holds a separation of two length scales. On the micro scale, fluid and contact simulations with real rough surfaces are performed. The results are used as effective properties on the macro scale. On the macro scale, friction is calculated based on a thermal elastohydrodynamic lubrication simulation. As a component of interest a journal bearing with a steel shaft and a PEEKCF30 bushing (high temperature thermoplastic with 30 mass-% short carbon fiber) is used. On the micro scale, a heterogeneous FEM-based contact simulation with rough surfaces is developed, in which the real fiber distribution is merged with the real roughness. This novel heterogeneous contact simulation leads to significantly less contact stiffness compared to a homogeneous contact simulation based on tensile tests of PEEKCF30. The results show that there is no generic, homogeneous stiffness for the contact simulation of heterogeneous materials due to the varying roughnesses and fiber distributions, which are not known a priori. The developed FEM contact model offers an approach to solve this problem. On the macro scale, the simulation is enhanced by additional thermal effects. The temperature dependent contact stiffness leads to decreasing friction for elevated temperatures. The consideration of thermal expansion results also in lower friction due to a global decrease of the fluid gap. Additionally the thermal expansion leads to a qualitatively different contact distribution. Furthermore, a wear simulation based on the mixed lubrication simulation and an energetic wear model is developed. The validation of the mixed lubrication simulation by a journal bearing test rig shows significant improvements for the friction prediction of polymeric composites. The simulated and measured worn geometry show a very good match because of the realistic modeling of the contact behavior by the mixed lubrication simulation. Keywords: PEEK, polymer, journal bearing, mixed lubrication, wear, TEHL simulatio

Evaluation of bridge component design and construction techniques: A look at integral abutment bridge precast approach slabs and post grouted drilled shafts

The bump at the end of the bridge and the high cost of deep embedded drilled shafts have long been recognized by many bridge owners. This research aims to mediate the bump at the end of the bridge and to validate the use of post grouting to increase drilled shaft capacity. Performance monitoring and full scale test programs were used to evaluate these technical issues. The bump at the end of the bridge is typically due to settlement of the approach soils and cracking of the approach pavements. The settlement and cracking in integral abutment bridges are typically dealt with by connecting the approach slab to the integral abutment bridge. Two integral abutment bridges with integrally connected precast approach slabs were evaluated using long-term monitoring systems to study their structural performance and determine the range of forces that should be considered when designing such approach slabs. This study has identified design and construction considerations for integrally connected precast approach slabs. The approach slab study revealed the source and magnitude of forces to be considered in the design and construction of approach slabs integrally connected to integral abutment bridges. Consideration of these forces in the design and construction of such approach slabs could potentially lead to reduced maintenance costs associated with the bump at the end of the bridge. The required deep embedment length of drilled shafts is due to the inability to fully mobilize the end bearing resistance of the shaft before reaching service displacement criteria. Post grouting of drilled shafts can be used to effectively increase the end bearing capacity within service displacement limits, often times allowing the drilled shaft to be shortened without sacrificing capacity. Through a load test program and long-term performance monitoring of production shafts, the increase in capacity and performance of post grouted drilled shafts were investigated. This study has identified design and construction considerations for post grouted drilled shafts. The post grouted drilled shaft study verified the use of post grouting as a technique for increasing the end bearing resistance of drilled shafts and also identified design and construction considerations for post grouted drilled shafts. Increasing the end bearing resistance of drilled shafts through the use of post grouting can effectively allow the shafts to be shortened without losing capacity or exceeding service displacement criteria; potentially leading to reduced costs for bridge projects.</p

Controllable Adhesion In A Bio-Inspired Film-Terminated Fibrillar Surface

In this dissertation we present work on the development, characterization, and analysis of an easy-to-fabricate, reusable bioinspired switchable adhesive that consists of a film-terminated fibrillar layer atop a substrate. We use a dynamic rod model and stability analysis to define and analyze the buckling of a fibril subjected to a prescribed shear displacement and a constant normal compressive force. Following this analysis, we present work on the switchable adhesive: a film-terminated fibrillar interface with two metastable states. In the first state, a thin film spanning the fibrillar surface results in strongly enhanced adhesion due to crack-trapping. In the second state, the thin film collapses onto the substrate between fibrils and resembles a rough surface. We perform indentation experiments (pull-off and adhesion hysteresis), which demonstrate differences in the adhesive response of the two states. We show that the adhesive state has a pull-off load up to 70 times higher than the non-adhesive state and has up to 20 times larger adhesion hysteresis. Friction experiments show that in the collapsed state there is no static friction peak and that even in sliding friction, which is not enhanced for the adhesive state over the control samples (flat, unstructured PDMS), the collapsed state exhibits much lower sliding friction forces. We determine the pressure-to-collapse the thin film to switch from the adhesive to the non-adhesive state using hydrostatic pressure experiments. Finally, we perform both linear plate and von Kärman plate analyses on the thin film as it deforms under an applied pressure to gain insight into both bistability and the pressure required to collapse the thin film and in doing so, turn off the adhesion. We find that the von Kärman plate theory more accurately captures the pressure required to initiate collapse of the thin film onto the substrate, most likely because of the large deflections taking place during collapse. To account for pressurization that occurs in our sealed samples during hydrostatic pressure experiments, we model the rate dependence in the hydrostatic pressure experiments. Pressurization and diffusion of gas through the thin film reduces the dependence on interfibrillar spacing

Hortensia

scripsis H. L. Naderman

Am Grabe meines Erlösers

von Hermann Ludwig Naderman

Opfer vor Gott in Gesängen und Gebeten : für Katholiken

Hermann Ludwig Naderman