Lap splices between post-installed and cast-in-place reinforcements
Design and experiments
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Beschreibung
Post-installed (PI) lap splices provide a reliable solution for connecting concrete elements that are cast at different times by overlapping cast-in-place (CI) reinforcing bars (rebars) with PI rebars. Although PI rebars embedded in high-performance mortars can provide improved bond-splitting behavior compared to CI rebars, their design is still restricted by guidelines originally developed for lap splices that exclusively involve CI rebars (CI lap splices).
This thesis investigates the bond behavior of PI lap splices to explore efficient design alternatives. It focuses on high-performance epoxy-based and hybrid mortars under static or quasi-static tensile loading. The research is structured into three main fields: i) an evaluation of single CI and PI rebar anchorages to understand the fundamental bond behavior, ii) experimental studies on PI lap splices in ordinary and steel fiber-reinforced concrete (SFRC) to identify the key parameters affecting bond strength and force transfer, and iii) structural testing of conventional one-to-one CI and PI lap splices, as well as novel non-contact PI lap splice designs featuring (n)-to-(n-1) and two-to-one configurations, in which the PI rebars are centrally positioned between the CI rebars.
The findings indicate that PI single anchorages, particularly those using epoxy-based mortars, can achieve up to three times higher bond strength than CI rebars under confined conditions. However, when PI rebars are spliced with CI rebars to form PI lap splices, the bond strength is constrained by the anchorage resistance of the weaker CI rebar and by splitting failure of the surrounding concrete. Despite these limitations, experimental investigations show that PI lap splices exhibit bond strength and crack control performance comparable to, or even exceeding, that of CI lap splices. Furthermore, the evaluation of PI lap splices in SFRC demonstrates enhanced bond capacity and ductility, primarily due to improved confinement and crack resistance.
At the structural level, the investigation confirms that (n)-to-(n-1) and two-to-one non-contact PI lap splices achieve steel yielding with very short lap lengths, making them suitable for demanding applications. Additionally, they exhibit a load-bearing capacity, stiffness, and ductility comparable to those of reference slabs reinforced with continuous rebars and conventional one-to-one PI lap splices. These novel designs offer significant advantages over conventional approaches. They benefit from the superior bond-splitting behavior of mortars, minimize material use, and simplify installation. Based on these findings, this thesis provides recommendations for incorporating this design concept into the next-generation Eurocode 2.
Autor*in
José Ignacio Croppi
Themen in »Lap splices between post-installed and cast-in-place reinforcements«
reinforced concrete bond lap splice post-installed rebar fiber-optic sensor direct tension test pullout test bond stress distribution steel fiber reinforced concrete splitting failure