Strengthening and prestressing of bridge decks with ribbed iron-based shape memory alloy bars. (15th August 2021)

• Record Type: Journal Article
• Authors: Schranz, Bernhard; Michels, Julien; Czaderski, Christoph; Motavalli, Masoud; Vogel, Thomas; Shahverdi, Moslem
• Is Part Of: Engineering structures. Volume 241(2021)
• Publication Date: 2021-08-15
• Subjects: Memory-steel -- Near-surface-mounted -- Cover replacement -- Concrete structures -- Slab -- Crack monitoring -- Digital image correlation; CFRP Carbon fibre reinforced polymer -- CR Cover replacement -- DIC Digital image correlation -- EB Externally bonded -- Fe-SMA Iron-based shape memory alloy -- FRP Fiber-reinforced polymer -- LVDT Linear variable differential transformer -- NSM Near-surface-mounted -- RC Reinforced concrete -- SME Shape memory effect -- TRC Textile-reinforced concrete; Structural engineering -- Periodicals; Structural analysis (Engineering) -- Periodicals; Construction, Technique de la -- Périodiques; Génie parasismique -- Périodiques; Pression du vent -- Périodiques; Earthquake engineering; Structural engineering; Wind-pressure; Periodicals; 624.105
• DOI: 10.1016/j.engstruct.2021.112467
• Languages: English
• ISSNs: 0141-0296

Abstract

Highlights: RC slabs were strengthened and prestressed using ribbed Fe-SMA (memory-steel) bars. Near-surface-mounted and cover replacement methods were investigated. No damage in grouted anchorages (no metallic parts) during and after prestressing. Strengthening greatly improved the performance at service and ultimate load levels. Analytical procedures based on measurements enabled estimation of prestress. Abstract: Given the increasing age of our built environment, including concrete structures, stakeholders in the construction industry require innovative and effective strengthening methods. In several studies and onsite applications, iron-based shape memory alloy (Fe-SMA) reinforcements have proven to be competitive alternatives to well-established materials. The objective of this investigation was to study the effectiveness of two different prestressed strengthening methods for concrete members in flexure using recently available ribbed Fe-SMA ("memory-steel") bars. Reinforced concrete slabs similar to the cantilever extension of box-girder cross-sections were strengthened using only cementitious anchorages and subjected to quasi-static loading. The first strengthening method comprised the removal of the concrete cover and the installation of memory-steel bars with an additional mortar layer. The second strengthening method comprised the cutting of grooves in the concrete cover, followed by the installation of memory-steel bars with mortar (near-surface-mounted). The prestress was obtained via resistive heating of the memory-steel bars. The strengthened specimens exhibited highly improved cracking, yielding, and maintained ductility until ultimate concrete compression failure. Observations utilizing a digital image correlation system indicated a damage-free prestressing process and no premature failure of the strengthening reinforcement. Different analytical approaches were used to estimate the prestress.