JoSEM (2017) 1-8 © STM Journals 2017. All Rights Reserved Page 1 Journal of Structural Engineering and Management ISSN: 2393-8773 (Online) Volume 4, Issue 1 www.stmjournals.com Effect of Partial Fixity on Negative Bending Moments in RCC Frames Amit Kumar Gorai*, Lalit Kumar Sharma, P. Pal, P.K. Mehta Department of Civil Engineering, Motilal Nehru National Institute of Technology, Allahabad, Uttar Pradesh, India Abstract This paper presents the variation of bending moments in the RCC frames structure for different ratios of moment of inertia of the column and the beam (I C /I B ). In this study, three different cases of frames structure are considered e.g. the first case is single bay single storey to single bay five storied frames structure, the second case is two bays single storey to two bays five storied frames structure and the third case is three bays single storey to three bays five storied frames structure. The investigation is mainly focused on the variation of negative moments at the beam ends at the first floor of i th storey frame structure with the variations of I C /I B ratio, number of stories and number of bays in the frames structure. STAAD Pro software is used to model and analyse the considered frames structure. The obtained results are presented in tabular form to observe the effects of I C /I B ratios at the joints in each floor of five storied frames structure. Results are also compared with the analytical one and found to be satisfactory. Few interesting results observed in the analysis of three different cases of frames structure are presented herein. Investigated results on RCC frames structure may be useful to the engineers and designers. Keywords: Frames structure, stiffness method, rotation contribution method, negative bending moments, inertia ratio *Author for Correspondence E-mail: amit.gorai.50@gmail.com INTRODUCTION Portal frames used in several civil engineering structures like buildings, factories, bridges have the primary purpose of transferring the loads applied at their tops to their foundations. Structural requirements usually necessitate the use of statically indeterminate layout for portal frames, and approximate solutions are often used in their analyses. The most pressing point for future research on the subject of slab, beam and columns has undoubtedly raised the question of the degree of imperfection in practical fixed ends; in short, what value of K (fixity percentage) should be assumed for such ends. A complete answer to this question is difficult, but at present the designer has no real data whatsoever regarding practical end conditions. While a satisfactory answer to the above question remains the challenge. Design conventions have emerged which are usually conservative and which can be applied with confidence to orthodox types of attachment. For example, Zienkiewicz and Cheung extended the finite element study to the problem of bending of slab [1]. Bhaskar described a study on experimental and finite element modelling of composite deck slabs with and without embossments [2]. In the composite slabs, mechanical interlocking in the form of embossments or shear connectors, were used to transfer shear between the outer skin of the plate and the concrete core. Deaton developed a procedure to design reinforced concrete flat plate systems based on the results of finite element analysis [3]. Sharma and Kwatra presented their work by developing the model for skew bridges with any degree of skew angle and aspect ratio [4]. Barbosa and Ribeiro considered the practical application of nonlinear models in the analysis of reinforced concrete structures and the results of some analyses were performed using the reinforced concrete model considering general purpose finite element code [5]. César and Barros studied the non-linear P-∆ behaviour of three- dimensional frames with plan and elevation asymmetries using a parametric variation of