Page 251 - Bridge and Highway Structure Rehabilitation and Repair

226 SECTION 2 STRENGTHENING AND REPAIR WORK

4. Non-compact section compression fl ange buckling:
• Strength limit states I to V
• Construction limit state and uncured slab
• Refer to Section 6.10.5.3.3c and LRFD Equation 6.10.5.3.3c.
5. Non-composite non-compact section lateral torsional buckling:
• Positive and negative fl exure
• Strength limit states I to V
• Construction limit state and uncured slab
• Refer to Sections 6.10.5.5 and 6.10.6.4.
– L : 1.76 r (E/F ) 1/2
b
1
yc
5.7.5 Transverse and Bearing Stiffeners
1. Strength limit states I to V.
2. Refer to Section 6.10.8.
3. Refer to Section 6.10.8.2.1 for bearing stiffener location.
4. Refer to Section 6.10.8.2.4 for bearing stiffener geometry.
5.7.6 Shear Connectors
1. Strength limit states I to V.
2. Refer to Section 6.10.7.4.

5.7.7 Evaluation of Wind Effects Mw During Construction
1. Strength limit states III and V only.
2. Construction limit state and uncured slab.
Refer to Sections 3.8.1, 4.6.7.2.1 and 6.10.5.7.
3. Construction limit state.
Refer to Sections 6.10.5.3.2 and 6.10.5.3.3.
4. Section 6.10.5.3.2b for non-compact web slenderness.

5.8 LRFD LOAD COMBINATIONS FOR STRENGTH,
SERVICEABILITY, AND EXTREME CONDITIONS

5.8.1 AASHTO Load Combinations
In addition to old non-composite bridges, both composite and hybrid bridges are now being
built as a replacement.
The behavior of hybrid bridges is not fully known. They comprise:
1. Precast post-tensioned beams and cast-in-place deck slabs
2. Precast post-tensioned beams and precast deck panels
3. Steel girders with precast deck panels.
4. Cast-in-place reinforced concrete T-beams
5. HPS 70W steel girders with HPC
6. Pedestrian bridges.
Applicable load factors for temperature, shrinkage and creep etc. will vary for each type.
Dead load (DC1) load factors may not be identical in all cases.
Fatigue behavior for HPS beams may require a refined analysis. Similarly defl ection trucks

need to be of different lengths for small and long spans.
For Extreme load conditions the bridges located in different Seismic performance category
need to be rated on a different scale. Scour categories also need to be identifi ed.

Future AASHTO Specifications for design and rating are expected to consider the varia-
tions in practice and are likely to come up with detailed load factors and resistance factors. The