Beitrag in einem Tagungsband
Tensile behavior of ultra high performance concrete (UHPC) reinforced with a combination of steel-fibers and rebars
Details zur Publikation
Autor(inn)en: | Fehling, E.; Leutbecher, T. |
Herausgeber: | Zingoni, A. |
Verlag: | Millpress |
Verlagsort / Veröffentlichungsort: | Rotterdam |
Publikationsjahr: | 2007 |
Seitenbereich: | 549-550 |
Buchtitel: | Recent Developments in Structural Engineering, Mechanics and Computation |
Zusammenfassung, Abstract
Ultra high performance concrete (UHPC) is a very dense structured, fine or coarse-aggregated concrete with a compressive strength of at least 150 N/mm². For ductility reasons fibers, mostly high strength fibers are added. To carry tensile loads beyond the tensile strength of fiber concrete in beams or tensile members, fibers can be combined with conventional bar reinforcement or prestressing steel. As experimental investigations show, a combination of fibers and bar reinforcement affects the structural and deformation behavior in both serviceability and ultimate limit state. Mechanical models, developed so far, mostly assume a superposition of stress-strain-relationships of fiber concrete and reinforcing bars or premise a strain hardening behavior of fiber reinforced UHPC. Sometimes the stress-strain-relationship of fibre concrete is derived empirically from results of flexural tests. Based on equilibrium and compatibility, the presented mechanical model enables to predict both the integral load-deformation-behavior of UHPC-tensile members reinforced with combined reinforcement and the width of discrete cracks. Also the influence of the high autogenous shrinkage of UHPC is considered. Fundamentals are the well-known mechanical principles for cracked reinforced concrete and the stress-crack-opening-relationship of fiber concrete. The application of the proposed model to an extensive test series with numerous varied parameters (fiber type and content, type of reinforcing steel, bar diameter, reinforcement ratio etc.) shows a very good agreement with the proposed model even for fiber-reinforced UHPC with strain softening behavior. Thereby contradictions inherent to existing models could be identified and resolved.
Ultra high performance concrete (UHPC) is a very dense structured, fine or coarse-aggregated concrete with a compressive strength of at least 150 N/mm². For ductility reasons fibers, mostly high strength fibers are added. To carry tensile loads beyond the tensile strength of fiber concrete in beams or tensile members, fibers can be combined with conventional bar reinforcement or prestressing steel. As experimental investigations show, a combination of fibers and bar reinforcement affects the structural and deformation behavior in both serviceability and ultimate limit state. Mechanical models, developed so far, mostly assume a superposition of stress-strain-relationships of fiber concrete and reinforcing bars or premise a strain hardening behavior of fiber reinforced UHPC. Sometimes the stress-strain-relationship of fibre concrete is derived empirically from results of flexural tests. Based on equilibrium and compatibility, the presented mechanical model enables to predict both the integral load-deformation-behavior of UHPC-tensile members reinforced with combined reinforcement and the width of discrete cracks. Also the influence of the high autogenous shrinkage of UHPC is considered. Fundamentals are the well-known mechanical principles for cracked reinforced concrete and the stress-crack-opening-relationship of fiber concrete. The application of the proposed model to an extensive test series with numerous varied parameters (fiber type and content, type of reinforcing steel, bar diameter, reinforcement ratio etc.) shows a very good agreement with the proposed model even for fiber-reinforced UHPC with strain softening behavior. Thereby contradictions inherent to existing models could be identified and resolved.
Schlagwörter
combined reinforcement, crack width, durability, economic mix design, tensile behavior, UHPC
