UNIVERSITY OF PISA
FACULTY OF ENGINEERING
Department of Structural Engineering
Master’s Degree in Engineering of Civil Constructions
Master’s Degree thesis
“LAUNCHING PROJECT OF A COMPOSITE GIRDER BRIDGE”
Supervisors:
Prof. Ing. Pietro Croce
Dott. Ing. Daniele Lucchesi
Candidate:
Dianora Pietrini
Contents
Contents ... 1
INTRODUCTION ... 3
CHAP.1. State of the art in girder bridges erection ... 6
1.1. General techniques in girder bridges erection ... 6
1.1.1. Erection techniques of prestressed concrete girder bridges. ... 6
1.1.1.1. Erection techinque by means of movable shuttering systems ... 6
1.1.1.2. Erection techinque by means of precast concrete girders ... 10
1.1.1.3. Incremental launching ... 17
1.1.1.4. Balanced-cantilever erection ... 28
1.1.2. Erection techniques of steel girder bridges... 39
1.1.2.1. Incremental launching ... 39
1.1.2.2. Balanced-cantilever erection ... 48
1.2. Composite bridges erection ... 55
CHAP.2. Incremental launching technology ... 62
2.1. Introduction to incremental launching ... 62
2.1.1. Incremental launching of composite bridges ... 64
2.2. Structural system of the superstructure ... 65
2.3. Geometrical constraints ... 67
2.4. Launching techniques of light superstructures ... 68
2.5. Launching bearings and guide devices ... 77
2.6. Correction of launch stresses ... 77
2.6.1. Launching nose ... 81
2.6.2. Stayed front system ... 87
2.6.3. Temporary piers ... 89
2.7. Composite bridges ... 92
2.8. Launching of the steel girder ... 96
2.8.1. Launching bearings ... 97
2.8.2. Launching nose ... 99
2.9. Verifications of an incrementally launched bridge ... 101
CHAP.3. The study-case ... 103
3.1. General description of the bridge ... 103
3.2. Deck’s characteristics ... 104
3.3. Calculation of deck’s parameters ... 111
3.4. Steel tub gider bridges ... 114
3.4.1. Steel tub girder application issues ... 114
3.4.2. Depht, width and spacing of tub girders ... 116
3.4.3. Girder design ... 119
3.4.4. Diaphragms and bracing ... 122
3.5. Bridge construction ... 128
3.5.1. Workshop fabrication ... 129
3.5.2. Erection on site ... 130
4.1. Nose-deck interaction in launched bridges ... 138
4.1.1. General considerations ... 138
4.1.2. Theoretical model ... 139
4.1.3. Support reaction at the support 1 ... 142
4.1.4. Negative moment at the support section 2 ... 143
4.1.5. Negative moment at the support section 3 ... 147
4.1.6. Maximum positive moment in the first span ... 147
4.1.7. Maximum positive moment in the second span ... 150
4.1.8. Shear at the support section 2 ... 151
4.1.9. Final considerations and presizing of the launching nose ... 151
4.2. Solution of the continuos beam in launched bridges ... 153
4.2.1. Preface ... 153
4.2.2. Transfer matrix ... 153
4.2.3. Resolution method ... 156
4.2.4. Reduced transfer matrix ... 157
4.3. Calculation of deck stesses during launching ... 158
4.4. Launching nose project ... 166
4.5. Strenght and stability verifications of the superstructure during launching ... 168
4.5.1. Overturning verification (EQU) ... 168
4.5.2. Strenght and stability verifications (STR) ... 169
CHAP.5. Patch Loading ... 178
5.1. “Patch loading” problem in launched steel bridges ... 178
5.1.1. Stability behaviour due to basic load effects ... 179
5.1.2. EN 1993-1-5 proceedings ... 183
5.2. “Patch loading” verification of the superstructure during launching ... 184
CONCLUSIONS ... 191
Abstract
This thesis deals with the erection project of a composite girder bridge, by means of the incremental launching technique. After a detailed description of the main erection techniques regarding girder bridges (prestressed concrete, steel and composite bridges), the attention is focused on incremental launching, describing the most typical features and problems of this construction method, especially for composite bridges. Afterwards, a practical example is analysed, concerning a 310m-long steel tub girder bridge, with a varying depth concrete slab, incrementally launched from one abutment towards the opposite one (consisting in the construction of deck segments behind the abutment alternating with the launch of the whole deck section), using a steel trussed launching nose. The optimization of the nose-deck interaction is carried out, and the calculation of stresses in the superstructure during launching is performed by means of a special spreadsheet developed for this purpose, based on the reduced transfer matrix method. Finally, strength and stability verifications of the superstructure are accomplished, using a linear buckling FEM analysis, and the patch loading problem is described and discussed.
Key words: erection techniques, incremental launching, composite bridges, steel tub girder bridges,
