Study into Cracking of Deck Slab and Girders of Flyovers at Dholpuron Nh3 and Development of Strengthening Scheme

PI: Prof. Durgesh C. Rai

The two flyover structures of Dholpur-Morena section of NH-3 located at Dholpur developed inclined shear cracking in their prestressed girders at both ends in addition to deck slab cracking. These structures, except at the obligatory spans over the railway tracks or highway, are composed of three-span modules of simple span precast prestressed I-girders made continuous. After detailed study of the structure and analysis using CSiBridge program, several design and construction discrepancies were identified, namely, too slender girders, inadequate shear reinforcement in girders, increased negative continuity moments due to change in construction sequence (continuity diaphragms were cast before the deck slab) and inadequate quantity and anchorage length of negative continuity reinforcement in the deck slab. Two stages of strengthening is proposed which involves thickening of girder webs with additional shear reinforcement and new deck slab overlay with  required negative continuity reinforcement along with use of carbon fiber wraps and laminates to further increase flexure and shear strength of pre-tensioned girders.