Many experimental studies have been conducted to understand the in-plane behaviour of reinforced concrete frames infilled with masonry walls (IM-RC). However, detailed analyses of those experimental studies have revealed that the in-plane behaviour of certain IM-RC frame configurations (e.g. different masonry strengths, wall aspect geometries, high strength masonry infills with ductile frames) are not well explored. Therefore, an attempt has been made to extend the understanding of the in-plane behaviour of IM-RC frames by analysing different IM-RC frame configurations using experimental and numerical data. Focus was given in this study to analyse the in-plane behaviour of single storey-single bay IM-RC frames. The numerical analyses were conducted on specific IM-RC frame cases, where experimental results are not available. For that purpose, a numerical modelling method employing fibre-element based RC frames with multi-diagonal struts for IM walls was used. The established numerical modelling method of IM-RC frames has been validated with different experimental datasets, thus proving its ability to accurately predict the in-plane behaviour of different IM-RC frames. Using the experimental and numerical datasets created, a set of seismic fragility functions have been developed. Four damage states incorporating evolution from IM to RC failures have been defined. The fragility functions are given in terms of compressive strengths of IMs (≤ 5MPa, > 5 & ≤15 MPa, and >15 MPa), and type of RC frame used (non-ductile and ductile). The derived fragility functions clearly show the importance of designing ductile frames for IM-RC building types; and the combinations of high strength IM walls with non-ductile RC frame configurations are shown to be more vulnerable than the other IM-RC frame configurations analysed.