Effectiveness of RCC Crown Hinge Reinforcement Detailing for a Three-Hinged Arch

Internal hinge is easier to implement in steel construction but difficult in the case of Reinforced Cement Concrete (RCC) structure. Arches provide economical designs compared to beams for large spans and three-hinged arches are preferred over two-hinged arches in certain situations. In this work, the goodness of reinforcement detailing for the hinge provided at the crown for a three-hinged arch given in Indian code, SP 34(S&T) (1987) is put to test. The crown detail with the main reinforcement crossing each other, cross-section notched, and the resulting gap filled with different resilient material (lead, bituminous felt, PVC, ABS, neoprene, and EPDM) is studied. The dimensional proportions of the notch and equation of the parabolic arch was obtained by tracing in AutoCAD. The structural design of the cross-section of the arch was performed based on IS 456 (2000) using design philosophies of limit state design and working stress method (programmed in spreadsheet). The stability check (for buckling) was performed approximately using Boussinesq equation assuming the arch to be of a circular shape. The designed cross-section of the three-hinged arch for a concentrated load of 100 kN at the crown and a span of 15 m following the geometric proportions obtained from SP 34(S&T) (1987) is modelled in ABAQUS. A detailed finite element analysis is carried out for the model. The flexural stresses developed at the crown and longitudinal strain developed in crossing bars for different resilient material is presented. Based on the results, the deviance of the RCC hinge from an ideal internal hinge is obtained based on bending moment developed at the crown, and the best resilient material to fill the gap at the crown of the arch is suggested.