Browsing by Author "Mahadik, Vinay"

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Open Access
Bidirectional loading history for seismic testing of 3D frame joints
(2021) Mahadik, Vinay; Sharma, Akanshu
Beam-column-joints (BCJ) in reinforced concrete (RC) frames are known to be critical against seismic actions. Hence, several researchers have conducted related investigations. The loading history used in the experimental investigations must be a sufficiently accurate and conservative representation of seismic loading on the structure and should trigger all possible critical failure mechanisms in the subassembly. Presently, there is significant diversity in the loading histories used for seismic investigation of structural subassemblies. This paper intends to propose an optimum loading history for considering bidirectional (horizontal) seismic action on 3D-RC BCJ subassemblies. To this end, the available loading histories (unidirectional and bidirectional) for simulation of seismic loads on RC joint subassemblies are reviewed in the context of the demands they impose on the joints. Finite element modeling and analyses are used as a tool for investigating the response of 3D-BCJ subassembly under different bidirectional loading states.
Open Access
Influence of edge proximity on concrete breakout failure in post-installed RC columns foundation joints
(2023) Cattaneo, Sara; Mahadik, Vinay; Genesio, Giovacchino; Hofmann, Jan
This paper discusses findings from an experimental program aimed at investigation of concrete breakout failure within the rebar end anchorage zone of reinforced concrete column-to-foundation joints, with columns located in proximity of foundation edge/s. A total of four tests on full scale column foundation joints are presented. In all specimens the column main reinforcement is anchored in the foundation using post-installed rebar technology. All connections are designed with the objective to trigger concrete breakout failure mode within the rebar end anchorage zone. Finite element analyses were used as a tool to design the specimens. The paper presents discussion of the test results within the framework of expectations outlaid during design of the test specimens. The effects of bending compression from column on the concrete breakout capacity under influence of foundation edges is the specific focus of the present investigation. It is shown that the direction of application of load on the column largely determines the effect of bending compression from column on concrete breakout capacity. The test data presented in this paper offers the necessary benchmark data on concrete breakout behavior in the case of reinforced concrete column foundation joints under influence of foundation edges. This test data along with insights from finite element analyses is employed to explore and possibly identify necessary modifications to the current state-of-the-art consideration of concrete breakout capacity for reinforced concrete connections.
Open Access
Post installed rebar end anchorages in reinforced concrete structural connections
(2022) Mahadik, Vinay; Sharma, Akanshu (Prof. Dr.-Ing.)
This thesis is an attempt to integrate the different available perspectives for rebar end anchorage design in general and post installed rebar in particular, and work towards a general framework for design of end anchorage zones in reinforced concrete (RC) connection applicable irrespective of the detailing (straight or with bends) and type (cast-in or post installed) of the connection. It builds on comprehensive discussions of the current state-of-the-art consideration of anchorages in reinforced concrete construction. The discussions are aligned in a way to highlight the diversity of the different perspectives of assessment and design of rebar end anchorages and at the same time identify the context in which the perspectives could be integrated. The mechanical state of loading and the possible load resisting mechanisms are identified as pivotal for this purpose, and hence provide the rational background platform necessary for comparison of different approaches for assessment of rebar end anchorages. The differences in the assessment approaches are better understood in the light of the possible load resistance mechanisms and the potential of the models used for their realistic assessment. The system (or product) specific definition of bond resistance in fastenings technology in contrast to the general empirical definition of bond resistance in conventional RC practice is found to be one primary aspect responsible for the evident differences in the assessment approaches. The recent developments of system specific models for bond resistance coherent with RC practice (PO+SP model framework) that resulted from research projects conducted at IWB, University of Stuttgart, Germany are discussed. These models form an important input for the general assessment framework for rebar end anchorages based on failure hierarchy of all possible load resisting mechanisms (the Failure Hierarchy (FH) approach) developed in this thesis. The different mechanics in RC connections: column-foundation joints (CFJ), wall-foundation joints (WFJ) and beam-column joints (BCJ) strongly affects the behaviour rebar end anchorage zone. Hence a possibility of connection specific consideration in assessment of the rebar end anchorage zones is identified based on the discussion of the available response database in literature for the different joint types. This thesis develops an assessment framework (Failure Hierarchy Approach) for realistic evaluation of rebar end anchorage zones giving due consideration to (i) system specific characteristics of different types of anchorages (cast in and post installed) and (ii) different possible mechanical states of the connection (CFJ, WFJ, BCJ). A need for generating benchmark test data for observing the transition of different failure modes possible in rebar end anchorage zones is highlighted in these discussions. To this end, the design of test specimens is performed for obtaining response database specific to the range of parameters over which a transition of different possible failure modes in the rebar end anchorage zones can be observed. The test program on column-foundation joints provides the necessary database for overall validation of the FH approach. A comparison of different assessment approaches in the light of test results from this thesis and from the literature show the potential of the FH approach for realistic assessment of the behaviour of rebar end anchorage zones in RC connections. For highlighting the importance of connection specific consideration, experiments on wall-foundation joints and beam-column joints are conducted. The generated database provides useful insights towards harmonization of co-existing concrete failure theories. The thesis concludes with an overview of the extent to which the objective of development of general assessment framework for rebar end anchorage design could be reached. Contribution from this thesis towards design concepts for rebar end anchorage anchorages are discussed. The thesis closes with open questions that need further investigations and recommendation for the way forward based on insights it has developed.