Strengthening of continuous-span composite bridges using post-tensioning and superimposed trusses

Abstract

X iv 4.5. Recommendations for design 85 4.5.1. Selection of the strengthening scheme 85 4.5.2. Selection of the bracket locations. . 86 4.5.3. Design considerations for the post-tensioning tendons and superimposed trusses 88 4.6. Application of the design methodology to actual bridges 89 4.6.1. Strengthening system 1 91 4.6.2. Strengthening system 2 91 4.6.3. Comparison between the different strengthening systems 93 DESIGN EXAMPLE 96 5.1. Using the spreadsheet 97 5.1.1. Retrieving the spreadsheet into LOTUS 1-2-3 99 5.1.2. Getting acquainted with the spreadsheet 100 5.2. Computation of section properties: 101 5.2.1. Section properties of the exterior stringers 101 5.2.2. Section properties of the interior stringers 104 5.2.3. Section properties of the entire bridge cross-section 105 5.3. Computation of vertical loads on the bridge stringers 107 5.3.1. Dead loads 5.3.2. Long-term dead loads 5.3.3. Live loads 5.4. Computation of maximum moments due to vertical loads 5.5. Computation of stresses on the bridge stringers due to vertical loads 5.6. Input of bridge parameters and computation of force and moment fractions 5.7. Computation of overstresses to be removed by strengthening 5.7.1. Allowable stresses 5.7.2. Stresses due to vertical loads at the critical sections 5.7.3. Computation of overstresses at the critical sections V 5.8. Design of the required strengthening system 5.8.1. Choice of strengthening scheme ... 126 5.8.2. Computation of strengthening forces 130 5.8.3. Final design forces 5.9. Check of stresses 5.9.1. Stresses in the bottom flanges of the steel stringers 5.9.2. Stresses in the top flanges of the steel stringers 5.9.3. Stresses in the concrete deck .... 5.10. Accounting for post-tensioning losses and approximations in the design methodology. .