Diaphragms are important components of reinforced concrete ribbed beam bridges. Thus, diaphragm fatigue damage can seriously threaten the safety of in-service reinforced concrete ribbed beam bridges. In order to explore the fatigue performance of reinforced concrete beams and determine the internal relations between diaphragm fatigue life and fatigue load stress level, an entity analysis model of reinforced concrete simply supported T-beams was presented in this study. The spatial entity model was established by using the finite element software Midas/FEA. The correlation was analyzed on the basis of fatigue stress level, spacing-span ratio, width-height ratio, and fatigue performance of the beam diaphragms. The reliability of the calculation results was verified by using the traditional fatigue analytical methods of S-N curve and Miner linear cumulative damage theory and the methods for Goodman and Gerber correction. Results demonstrate that the fatigue life of the model beam increases and the damage degree decreases when the spacing-span ratio decreases and the width-height ratio increases. The model is economically reasonable when the diaphragm spacingspan ratio and the width-height ratio are 3.58 and 0.17, respectively. The study can provide references for further improving the anti-fatigue design of reinforced concrete diaphragm beams.

The carriageway plate, which is a bridge structure, directly bears the traffic load and can cause fatigue rupture easily by repeated loading. This study put forward an analysis model of reinforced concrete T-shaped girder carriageway plate girders to reveal the law of the influences of internal factors, such as length-width and thickness-width ratios of two-and one-way slabs, on the fatigue performance of carriageway plates. The physical girder space model was established using the Midas/FEA finite element software. The correlation between the fatigue stress level, length-width ratio, and thickness-width ratio of carriageway plates and the fatigue performance of carriageway plates of ribbed-girder bridges was analyzed using traditional fatigue analysis methods based on the S-N curve and Miner linear cumulative damage theory. The fatigue life and rupture areas were determined. The change rules of fatigue life and damage degrees of structure girders under different influencing factors were determined. Results show that a significant negative correlation exists between the length-width ratio and fatigue life of carriageway plate when the length-width ratio of one-way slabs ranges from 4.0 to 6.0. The fatigue life decreases linearly with the increase in the length-width ratio when the lengthwidth ratio of two-way slabs ranges from 1.0 to 1.9. The anti-fatigue performance of two-way slabs is stronger than that of one-way slabs. In addition, setting the thickness-width ratio of a carriageway plate between 0.07 and 0.08 is economically reasonable. This study provides a certain reference value for the further perfection of the anti-fatigue design of carriageway plates of reinforced concrete ribbed-girder bridges.