Mechanical performance of jointless retrofitted bridge with hollow-slabs

A multi-span bridge with hollow-slabs was retrofitted into a jointless bridge, in which the simple support slabs were converted into the continuous slabs with double row supports and the general abutments were converted into deck-extension abutments, thus, all movable deck joints of the bridge were eliminated.The static and dynamic load tests of jointless retrofitted bridge with multi-span hollow-slabs were carried out, and the mechanical performance of the bridge was studied.The finite element model was used to calculate the structural mechanical performance, bearing capacity and mechanical performance of approach slab, and to analyze the influence of single and double rows supports on the structural mechanical performance.Test result shows that after jointless retrofitting, the tested fundamental frequency of the bridge is8.60 Hz and larger than 5.37 Hz before jointless retrofitting.The maximum tested impact factor is 1.11 of four vehicle speeds and smaller than 1.36 that is the calculated value by the General Specifications for Design of Highway Bridges and Culverts (JTG D60—2004).The verification coefficients of the strain and deflection are less than 0.95.Obviously, the jointless retrofitting enhances the integrality of the bridge and improves the driving comfortability.The finite element analysis result shows that after jointless retrofitting, the fundamental frequency of the bridge is8.48 Hz, and the ratio is 1.01 between the tested fundamental frequency and calculated result, so the bridge is in good working condition.The positive bending moments of mid-span sections reduce significantly with a maximum value of 15.6% at the second span, while the negative bending moments appear at the inner-supports and the shear forces near the inner-supports increase with a maximum value of 18.2%.The mid-span deflections decrease obviously with a maximum value of 35.5% at the second and third spans, which indicates that the integral stiffness of the bridge improves significantly.The calculated maximum crack width is 0.15 mm and smaller than 0.20 mm that is the allowable value in the Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts (JTG D62—2004) (Bridge Code for short), and the checking results of bearing capacity, deflection and crack width meet the requirement of Bridge Code.The rows of supports have no significant effect on the inner forces of the superstructure, and the double row supports are feasible.The friction coefficient between the approach slab and its subgrade has significant influence on the axial forces of the approach slabs and the pavement, but has no significant effect on the bending moment.The maximum tensile stresses of the approach slab and pavement are 0.87 and 1.25 MPa, respectively, which meets the strength design requirement.