Developing repair materials for stress urinary incontinence to withstand dynamic distension

Polypropylene mesh used as a mid-urethral sling is associated with severe clinical complications in a significant minority of patients. Current in vitro mechanical testing shows that polypropylene responds inadequately to mechanical distension and is also poor at supporting cell proliferation.Our objective therefore is to produce materials with more appropriate mechanical properties for use as a sling material but which can also support cell integration.Scaffolds of two polyurethanes (PU), poly-L-lactic acid (PLA) and co-polymers of the two were produced by electrospinning. Mechanical properties of materials were assessed and compared to polypropylene. The interaction of adipose derived stem cells (ADSC) with the scaffolds was also assessed. Uniaxial tensiometry of scaffolds was performed before and after seven days of cyclical distension. Cell penetration (using DAPI and a fluorescent red cell tracker dye), viability (AlamarBlue assay) and total collagen production (Sirius red assay) were measured for ADSC cultured on scaffolds.Polypropylene was stronger than polyurethanes and PLA. However, polypropylene mesh deformed plastically after 7 days of sustained cyclical distention, while polyurethanes maintained their elasticity. Scaffolds of PU containing PLA were weaker and stiffer than PU or polypropylene but were significantly better than PU scaffolds alone at supporting ADSC.Therefore, prolonged mechanical distension in vitro causes polypropylene to fail. Materials with more appropriate mechanical properties for use as sling materials can be produced using PU. Combining PLA with PU greatly improves interaction of cells with this material

Integrale Brücken und derer Zuverlässigkeitsaspekte unter Einbeziehung von Monitoring

Bei Integrale Brücken handelt es sich um zumeist in Form von Rahmentragwerken ausgeführte lager- und fugenlose Brücken, welche sich durch hochgradige statische Unbestimmtheit auszeichnen. Obwohl dieser Bauwerkstyp in letzter Zeit auf ständig wachsendes Interesse seitens der Bauwerkseigner stößt, welche mit signifikanten Einsparungen in der Bauwerkserhaltung aufgrund des Fehlens der stark gefährdeten Brückenausrüstung (Lager und Fahrbahnübergänge) rechnen, ist deren Akzeptanz unter Planern und Bauherrn nach wie vor eingeschränkt. Gründe hierfür sind die zahlreichen Unsicherheiten im Entwurf, die durch die Entwicklung der Materialfestigkeit mit der Zeit, Kriech- und Schwindvorgänge im Beton sowie geeignete Modellierungsmöglichkeiten begründet sind. Aus diesem Grund werden gegenwärtig in mehreren Forschungsprojekten durch Monitoring des Strukturverhaltens von neugebauten integralen Brücken, deren Interaktion mit dem Untergrund und numerischen Untersuchungen die notwendigen Grundlagen für eine österreichische Richtlinie zur Bemessung Integraler Brücken und die Verifikation beziehungsweise Verbesserung der Entwurfskriterien erarbeitet. Integral abutment and joint-less bridges are structures without bearings and expansion joints. These types of structures do gain much popularity among bridge owners, since they expect reduced costs in maintenance due to the missing of significantly endangered details like bearings and joints. Nevertheless, the acceptance by designers is not that high since there are a lot of uncertainties with regard to material strength development,creep, shrinkage and availability of suitable numerical models. These topics are currently being addressed by several research projects with the aim to work out an Austrian guideline for the design of jointless bridges and to verify or improve current design criteria. Work includes monitoring of the actual structural response of newly built jointless bridges, their interaction with the underground and numerical simulations

Inspection of bridges in Austria : practice and outlook

During the last decades many structures-buildings and bridges-have been erected, many of which have already reached their initial design life demanding high efforts in inspection and maintenance. Due its geographical characteristics the Austrian railroad and street network consists of a high number of bridges, further complicating the task at hand. In course of a research project called AIFIT demands by operators and engineers were listed and future possibilities for more efficient inspection in accordance with current codes were derived

Nonlinear design and monitoring aspects of jointless structures

Jointless bridges are characterized by integral abutments and their lack of bearings and expansion joints. Recently this construction type has gained much popularity among bridge owners, since reduced costs in maintenance and rehabilitation are to be expected caused by the lack of significantly endangered details like joints and bearings. However, due to uncertainties regarding numerical modeling, material strength development and interaction with the soil the acceptance by designers is not that high. Currently those topics are being addressed by a number of research projects aiming at (a) the verification of current design criteria for jointless bridges, (b) the improvement of those, and (c) the derivation of an Austrian guideline regarding the design of this construction type. By monitoring the real structural response using suitable sensor-systems and performing advanced finite-element calculations to study the influence of creep, shrinkage and loading, current design concepts are being evaluated. Finally based on those models the most relevant design criteria can be optimized even taking into account the non-linearities in material laws and geometrical properties. This paper presents a suitable concept for non-linear design which allows for the activation of reserves in bearing capacity and thus more efficient design. Modeling uncertainties as well as sensitivities between material properties, loading and design parameters are covered by the second paper “Probabilistic Design Aspects of Jointless Structures associated with Monitoring Information”

Risk based safety analysis and reliability assessment of chloride deteriorated prestressed concrete structures : part II

degradation due to the in-service effects of traffic and environmental actions is commonly an expensive, and sometimes problematic, task. Chloride ion ingress is an important factor influencing both durability design and maintenance issues, especially in regions where winter de-icing salt application for traffic safety reasons is common, e.g. for highway structures. The presented example introduces a feasible approach for the analysis of potential chloride induced corrosion and associated deterioration in the context of an actual highway bridge application. The degradation due to de-icing salt application is threated in Part I of this contribution. In addition to numerical and experimental investigations of chloride ingress and the corrosion processes, a performance assessment is made for the serviceability and ultimate limit states on the basis of code derived criteria; with the ultimate limit state analysis being performed for various times during the envisaged service life. This allowed circumstances to be identified which would result in the structure reaching the end of its effective service life. These outcomes can be used to inform decisions on the future management of the structure

Risked based design aspects for concrete structures

The design of concrete structures is mostly based on more or less numerically intensive methods. Especially the design of bridges according to the new Euro Code Format requires numerous verification procedures on the Service Ability and Ultimate Level State. In contrast to code-based design an integral-design (ID) allows a more realistic description of the structure, since the necessary reliability level and environmental conditions can be included directly by means of detailed numerical models and in-depth monitoring. In addition, a risk based design in combination with the previously mentioned ID enables an effective design procedure. Hence, the objective of this article is the discussion of risk based design concepts associated with Euro Code format