PSI - Issue 5

Ivan Baláž et al. / Procedia Structural Integrity 5 (2017) 1057 – 1064 Ivan Baláž / Structural Integrity Procedia 00 (2017) 000 – 000

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longitudinal stiffeners and 14 measurements of negative imperfections of longitudinal stiffeners. Both measurements consisted of 12 sets differing in: a) thickness of bottom flange plate 12, 14, 16, b) kind of stresses in plate panel: compression or tension stresses, c) positive or negative imperfections. Negative means on the stiffener side of plate. The gauge length was spacing of the transverse stiffeners a = 3000 mm. The obtained values were compared with the value a / 500 = 6 mm in the case of positive imperfections and with the value a / 750 = 4 mm in the case of negative imperfections. The value 6 mm valid for positive longitudinal stiffeners imperfections was exceeded in the sets with 95 % fractiles in T12 (18 measurements, a / 388 = 7.738 mm), in T14 (14 measurements, a / 395 = 7.589 mm), C14 (13 measurements, a / 390 = 7.694 mm), in T (47 measurements, a / 417 = 7.199 mm), in 12 (34 measurements, a / 427 = 7.033 mm|, in 14 (27 measurements, a / 395 = 7.586 mm), in all 92 measurements ( a / 432 = 6.938 mm). More details may be found in (Chladný, Baláž, 1993). In 1989 and 1993 the first author took part in the inspections of SNP Bridge led by Professor Chladný (Chladný, Tesár et al., 1989; Chladný, Dutko et al., 1993). The management of all highway bridges in Czechoslovakia was controlled by two codes: (i) ON 73 6220 Register of Bridges on Motorways, (ii) ON 73 6221 Maintenance of Bridges on Motorways, Highways and Urban Roads. According to these codes the physical condition of the bridge is classified in seven rating levels: perfect, very good, satisfactory, bad, very bad and poor. The principal inspections of the SNP bridge were carried out by the Department of Metal and Timber Structures in 1983, 1989 and 1993.The results of the principal inspection was performed in 1989 visually and with device for corrosion measurement. The main results of this inspection are presented in (Chladný, Baláž, 1993). Maintenance of the bridge structure during the period 1983 1989 was to be better than during previous maintenance period. Recommendations for maintenance and repairs were as follows: a) suitable expansion joints are needed, b) Special measures must be taken to protect the structure of the box girder, tower and anchor chamber against the corrosion due to rain water leakage, c) many parts of the bridge structure need cleaning and protection paint, d) general repainting inside the box girder is also needed. The classification of states of all Slovak bridges related to the year 2011 divided in seven grade groups may be found in the Table 17.3 on page 762 in (Baláž, 2014 ). 4. Inspection In the Czechoslovak standards there were specifications for three types of variable actions for the determination of load-carrying capacities: (i) the normal action V n : six two-axle vehicles in two lanes or three in one lane for narrow bridges with legal weights of vehicle for classes A / B bridges 320 kN / 220 kN, (ii) the exclusive action V r : one four axle vehicle 800 kN / 400 kN, (iii) the exceptional action V e : special set for heavy loads with two three-axle tractors (840 kN) and one 14-axle trailer (1960 kN). Rating factors values were calculated from the formula (2). In calculation of the rating factor values the following values were considered: (i) normal load: j = 1 – uniformly distributed carriageway loading 2.5 kN / m 2 , j = 2 – uniformly distributed sidewalk loading 4 kN / m 2 along the length 100 m and 2.5 kN / m 2 on the remaining part of length if it was longer than 100 m, j = 3 – wind loading was neglected ( m = 2), γ L,R = γ L,1 = γ L,2 = 1.4, δ R = δ 1 = 1.1, δ 2 = 1.0; (ii) exclusive load: m = j = 1 – the sidewalk loading as for (i); (iii) exceptional load: m = 0, γ L,R = 1.1, δ R = 1.05, ψ c = 1.0. The loading with of the carriageway is 2 x 8.5 m = 17 m and of the two footpaths 2 x 3 m = 6 m. 5. Load-carrying capacity evaluation

n

m

c       D i i , D 

R

L







L j j j ,

i

j

1

1

R F

. .



(2)

c L R R R    , L

Detailed calculation was done in (Chladný, Dutko, 1989). It was found that the critical section (Fig. 3) of the box girder governs in computing rating factors values. The very low effective breadth ratio and missing middle web of the box girder cross-section in the critical section are responsible for this controlling condition. The obtained rating factors