| Orthotropic steel decks(OSDs)have been widely employed in various long-span bridges owing to their excellent advantages,such as their lightweight,high bearing capacity,and short construction time.Rib-to-diaphragm connection(including diaphragm cutouts)is extremely vulnerable to fatigue cracking,which dominant failure mode,fatigue cracking mechanism,and fatigue performance enhancement have not been well-researched.At the same time,the novel rib-to-diaphragm connection provides a new solution to the problem of fatigue cracking of OSDs.Longitudinal and transverse cracks,rutting and local depressions in flexible pavements are the fundamental problems limiting the development of OSD.The rigid pavement has excellent properties such as impact resistance,crack resistance,and wear resistance.In this paper,the fatigue performance evaluation and structural optimization of orthotropic steel decks with flexible and rigid pavement were investigated through a combination of experimental,theoretical,and numerical simulations,and the main work completed is as follows:(1)The fatigue cracking mechanism of orthotropic steel decks with flexible pavement was investigated.Firstly,a full-scale fatigue test of OSD was carried out with the rib-to-diaphragm connection(including diaphragm cutouts)as the research object.During the fatigue testing,the crack propagation pattern was recorded to clarify the crack type and the dominant damage mode of the rib-todiaphragm connection.Then,a comparative analysis of the experiment results with the finite element results was carried out to verify the accuracy of the finite element simulation,and the wheel loading stress was analyzed to obtain the most unfavorable loading conditions.Finally,the sub-model technique was applied to the rib-to-diaphragm connection structure to clarify its fatigue stress distribution law.(2)The fatigue performance evaluation and structural optimization of the diaphragm cutouts and rib-to-diaphragm connection were investigated.Firstly,the fatigue performance of the diaphragm cutout was evaluated based on the hot spot stress method and the critical distance theory.Furthermore,the fatigue performances of the rib-to-diaphragm connection were evaluated based on the hot spot stress method and the equivalent structural stress method.The applicability and accuracy of the fatigue evaluation method for different welding hot spots were verified.Finally,the structural optimization of the new rib-todiaphragm connection was carried out to give the structural design parameters for optimal fatigue performance.(3)The fatigue performance evaluation and structural optimization of OSDs with rigid pavement were investigated.Firstly,finite element simulations were carried out of OSDs with bolted rigid pavement,and the fatigue performance enhancement effect of UHPC pavement parameters on rib-todiaphragm connection,curved cutouts,and studs was evaluated.Furthermore,the feasibility of epoxy binder as a rigid connection between UHPC pavement and the deck was verified,the degree of damage of the bonding interface between UHPC and the deck was evaluated,and the design value of epoxy binder strength was proposed.Finally,a novel bridge deck structure was formed by combining the novel Rib-to-diaphragm connection and OSDs with the epoxybonded rigid pavement. |
