Publication:
Equivalent diagonal strut coupled with hybrid plasticity approach for seismic response macro-modelling of clay brick wall infilled frames

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Date
2020-11-01
Authors
Van, Tze Che
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Research Projects
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Interaction between reinforced concrete frames and masonry infills under seismic load in Malaysia is often being overlooked by engineers and experts due to the low occurrence and magnitude of earthquake and scarcity of established research studies in the related area. Moreover, no guidance is given by Eurocode 6 and Eurocode 8 on macro-modelling approach of the seismic response of infilled frame. This study aims to provide an in-depth understanding on the seismic behaviour of masonry infilled reinforced concrete frames in Malaysia and to propose macro-modelling for masonry infilled frame through equivalent diagonal strut coupled with hybrid plasticity approach. Under the experimental testing, six half scale single-storey single-bay reinforced concrete frames with and without unreinforced clay brick infills were subjected to lateral monotonic and cyclic loadings. The seismic behaviour of the frame system improved in terms of strength, initial stiffness, energy dissipation and also delay in cracks formation in frame due to the presence of infill. However, the adopted masonry wall system is considered strong, thus induces shear failure in columns. It is discovered that effect of aspect ratio of infilled frame is significant in energy dissipation. Macro-Modelling of masonry infilled reinforced concrete frames using equivalent diagonal strut coupled with hybrid plasticity approach and an improved constitutive backbone law shows good correspondence with experimental result. Under the investigation of reliability of seven equivalent diagonal strut width models using the improved constitutive backbone law, it is discovered that models with similar strut width trends over aspect ratio produce similar responses. All the strut models are able to produce response with reasonable accuracy except Mainstone (1974) model. Seismic performance of a five-storey non-ductile masonry infilled reinforced concrete frames typically found in Malaysia was assessed using incremental dynamic analysis (IDA) with ten ground motion records. The collapse capacity at 16%, 50% and 84% fractiles of IDA curves are 1.0, 1.53 and 2.03, respectively. The maximum drift ratio where dynamic instability is reached ranges between 0.1% to 0.26%. This study has provided a practical elucidation of the interaction between infill and frame for the development of more realistic seismic-resistant design for Malaysia.
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