Home About us Contact
|
Home About us Contact | ||
|
|
||
Load Bearing Capacity (load + bearing_capacity)
Selected AbstractsDirect assessment of structural resistance against pressurized fractureINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 5 2003G. Bolzon Abstract The determination of the load bearing capacity of hydraulic structures such as dams, reservoirs and retaining walls requires the consideration of mixed-mode fracture, possibly driven by the fluid pressure, in correspondence to artificial and natural joints (or cracks, in the latter case). A friction-cohesive softening interface model with coupled degradation of normal and tangential strength is introduced here to account for the essential features of the joint behaviour; its predictive capability is assessed through extensive calculations. Alternative numerical techniques resting on the discrete-crack approach are considered, focusing on simplified approaches for the direct appraisal of the structural resistance. Comparison is made with the results of evolutionary analyses, based on a priori piecewise linearization of the interface model and on ,exact integration'. Copyright © 2003 John Wiley & Sons, Ltd. [source] Zum Einfluß der Temperatur auf die Bemessung von Kühlturmschalen aus StahlbetonBAUTECHNIK, Issue 11 2005Michél Bender Dipl.-Ing. Zwangsmomente aus Temperaturgradienten haben erheblichen Einfluß auf die Bewehrungsmengen in Kühlturmschalen aus Stahlbeton. Dabei spielen nicht nur charakteristische Temperaturrandwerte und deren Kombination mit weiteren Einwirkungen eine Rolle, sondern auch die bei linearen Schnittgrößenberechnungen angenommenen Steifigkeitsreduktionen zur pauschalen Berücksichtung zwangsabbauender Rißbildung. Im Rahmen einer Sensitivitätsanalyse wird der Einfluß von Temperatureinwirkungen auf die Bemessung der Kühlturmschale vorgestellt. Basis der Parametervariation sind die spezifischen Berechnungsvorschriften der Bautechnischen Richtlinie BTR für Kühltürme (2005). Die maßgebenden rechnerischen Bemessungsszenarien werden anschließend in materiell und geometrisch nichtlinearen Analysen der Schale nachvollzogen, um die zwangsabbauende Rißbildung, den Einfluß der Temperatur auf Grenzzustände sowie Stahl- und Betonspannungswerte realistisch abzuschätzen und rechnerischen Werten gegenüberzustellen. Temperature effects on the design of cooling tower shells. Bending moments caused by temperature constraints substantially influence required reinforcement quantities in cooling tower shells. Important parameters in linear structural analyses are the extents of characteristic thermal actions and their combinations as well as global reduction factors that account for the loss of stiffness by cracking. The sensitivity to variations in temperature scenarios is presented using numerical simulations of a representative cooling tower shell and the design specifications of "BTR-Kühltürme (2005)". The characteristic design-scenarios are simulated in geometrically and materially nonlinear computations to realistically estimate the loss of stiffness by cracking, the influence of temperature effects on the ultimate load bearing capacity as well as actual extents of steel and concrete stresses. [source] Tragverhalten von Verbundbauteilen aus bewehrtem UHFB und StahlbetonBETON- UND STAHLBETONBAU, Issue 8 2009Cornelius Oesterlee Dipl.-Ing. Baustoffe; Bauwerkserhaltung/Sanierung; Bauausführung; Versuche Abstract Ultra-Hochleistungs-Faserbetone (UHFB) eignen sich aufgrund ihrer hohen Festigkeiten, des hohen Verformungsvermögens und der geringen Permeabilität zur Verbesserung und Instandsetzung bestehender Betonbauten. Mit dünnen Schichten von bewehrtem UHFB, die auf bestehende Stahlbetonbauteile aufgetragen werden, können der Tragwiderstand und die Gebrauchstauglichkeit deutlich gesteigert werden. In einer umfangreichen Versuchsreihe wurden die Eigenschaften von mit zusätzlich zu den Fasern auch mit Stabstahl bewehrtem UHFB untersucht. Die Bewehrung des UHFB mit Stabstählen ist vorteilhaft, um den Verfestigungsbereich des UHFB zu erweitern, seinen Tragwiderstand zu erhöhen und die Streuung seiner mechanischen Eigenschaften zu reduzieren. Zur Bewehrung können hoch- oder niederfeste Stähle mit unterschiedlichen Oberflächenstrukturen zum Einsatz kommen. Abschließend werden zwei Anwendungen vorgestellt. Structural Behaviour of Composite Elements Combining Reinforced Ultra-High Performance Fibre-Reinforced Concrete (UHPFRC) and Reinforced Concrete Due to their high strengths, high deformability and low permeability Ultra-High Performance Fibre-Reinforced Concretes (UHPFRC) are suitable for the improvement and rehabilitation of existing concrete structures. Thin layers of reinforced UHPFRC that are applied to existing concrete members, increase both the load bearing capacity and the serviceability. By comprehensive experimental studies the behaviour of UHPFRC with additional bar reinforcement was investigated. The reinforcement of UHPFRC is advantageous in order to increase the strain hardening capacity of UHPFRC, its load bearing capacity and to reduce the scatter of its mechanical properties. Low or high strength steel grades with various surface characteristics can be used as reinforcement of UHPFRC. Finally two on site applications are presented. [source] Kurze Verankerungslängen mit RechteckankernBETON- UND STAHLBETONBAU, Issue 1 2004Josef Hegger Prof. Dr.-Ing. Abstract In der Zulassung Z-15.6-204 [1] des Deutschen Instituts für Bautechnik werden Halfen HDB-E-Anker mit rechteckigen Köpfen als Endverankerung in Rahmenknoten und Konsolen für die Anwendung gemäß DIN 1045-1 und DIN 1045 geregelt. Durch die schlupfarme Verankerung der Zuggurtbewehrung ergeben sich Vorteile hinsichtlich der konstruktiven Durchbildung, der Tragfähigkeit und der Bauausführung. In diesem Beitrag werden die Zulassungsregelungen erläutert. Rectangular Anchors with short Anchorage Length The technical approval Z-15.6-204 [1] of the Deutsches Institut für Bautechnik gives design rules for the use of Halfen HDB-E-headed studs in exterior-beam-column-joints and corbels. The anchorage with headed studs is characterized by a negligible slippage of the reinforcement and is advantageous regarding the load bearing capacity, the detailing and the handling on site. This paper describes the design rules, devided from comprehensive experimental and numerical investigations [2]. [source] A study of the bone healing kinetics of plateau versus screw root design titanium dental implantsCLINICAL ORAL IMPLANTS RESEARCH, Issue 3 2009Gary Leonard Abstract Objective: This study was designed to compare the bone healing process around plateau root from (PRF) and screw root from (SRF) titanium dental implants over the immediate 12 week healing period post implant placement. Material and methods: 32PRF and 32SRF implants were placed in 8 beagle dogs at 12, 8, 5 and 3 weeks prior to enthanisation using a bilaterally balanced distribution. Undecalcified ground sections were prepared from the biopsies taken and histometric measurements of bone implant contact (BIC) and bone area fraction occupancy (BAFO) were made on the middle 5 mm portion of each 8 mm implant root length. Results: The analysis showed that although measurements of bone to implant contact (BIC) and bone area fraction occupancy (BAFO) tended to be greater for the SRF implants at all four time points, the differences in measurements between implant types did not reach statistical significance (P=0.07, P=0.06). The effect of time on BIC and BAFO was found to be strongly significant for both implant types thus indicating a statistically significant increase in BIC and BAFO overall with time (P=0.004, P=0.002). Furthermore, both PRF and SRF implants behaved similarly over time with measurements of BIC and BAFO progressing in parallel. Histomorphologic analysis of these sections demonstrated the prominent role of woven bone (callus) in the bone healing process around PRF implants. Conclusion: The results can be interpreted to indicate a comparable development of secondary stability for both PRF and SRF implant designs. However, as these parameters reflect the structural connection between implant and bone and not the functional properties of the bone to implant interface, they cannot be regarded as comprehensive measures of osseointegration. This particularly relevant given the reduced load bearing capacity of woven bone. [source] | ||||||||||