Page 291 - Bridge and Highway Structure Rehabilitation and Repair

266 SECTION 2 STRENGTHENING AND REPAIR WORK

Table 6.9 Sample spreadsheet for check bolts for strength I, III, and V load combinations (continued).
Strength I / III Axial Force Diagonal Horizontal SMSQ Resultant
Sec. 6.5.4.2 ()) () )
s
()) R n 1 7.722
If R /R t > 1 OK 2.5700
n
Service II Condition
Service II Axial Force Horiz.Comp. Vert.Comp. SMSQ Resultant
LOCATION 1

2 0.5
2
R = (H + V ) 100.9 22.7 10696.1 103.422
LOCATION 2 10 15 325 18.0278
LOCATION 3 15 10 325 18.0278
NO. OF BOLTS 9

Force/Bolt = R/N 26.7 25.6 56 11.4913

Service II Slip Resistance Slip-Critical
R = R/N, ()) = 1 11.4913
t
AASHTO LRFD K h K s N s P t R n

Sec. 6.13.2.8 Eq.1

R = K K N P t 0.6 0.33 2 39 15.444
h
s
s
n
Tables 6.13.2.8 Table 2 Table 3 Table 1
/R >1 OK 1.344
If R n t
6.8 DESIGN OF A DECK SLAB
6.8.1 Design and Rating of a Reinforced Concrete Slab or a Slab Bridge

Of all bridge components, the deck is the most vulnerable to wear and tear and may be
replaced after every 10 years when subjected to heavy daily traffic and deicing salts.

Slab bridges: Both in the U.S. and worldwide there are many existing bridges which are
beamless or “slab bridges.” In the following solved examples, only small and medium spans are
considered for design and rating.
According to LRFD 5.14.4.1, concrete slabs and slab bridges designed in conformance with
AASHTO specifications are considered satisfactory for shear. Also, as per LRFD 6.5.9, shear

need not be checked for design load and legal load ratings of concrete members.
No service limit states apply to reinforced concrete bridge members. Only strength I for
HL-93 or legal live load or strength II for permit loads will be considered.
Comparison between design and rating: Design requires balancing the external dead and live
load moments with moment of resistance, using load factors and resistance factors. Design is
done before rating. Rating requires evaluating the reserve strength or moment capacity available
for live loads after deducting the dead load moments. Rating is expressed as a ratio of available
live load moment capacity to peak external live load moment from HL-93 legal or permit loads
and needs to be greater than one.