1. 5 april 2004 J.M. Zwarthoed Workshop on Cracking and Durability of Reinforced Concrete Concerning the Serviceability Limit State

2. 5 april 2004 J.M. Zwarthoed2 Starting points of structural analysis Analysis in ULS and SLS: - main concern  safety; - durability of minor concern. According to code VBB 1995: - dead weight  = 1,5; - traffic loading  = 1,5. According to code NAD ENV 1991-3: - dead weight  = 1,35; - traffic loading  = 1,42; - with the actual traffic lane subdivision; - with reduction of structure service life.

3. 5 april 2004 J.M. Zwarthoed3 Requirements SLS - NEN 6720 For all structures important  crack width! Maximum permissible crack width depends on environmental exposure conditions: - humid (outside): w max = 0,3 mm; - aggressive (outside&salt): w max = 0,2 mm; - in case of pre-stressing: w max = 0,1 mm.

4. 5 april 2004 J.M. Zwarthoed4 Possible locations with regard to exceeding maximum crack width (1) 1 3 2 4

5. 5 april 2004 J.M. Zwarthoed5 Possible locations with regard to exceeding maximum crack width (2) 5 6 7 8 9 10 11 12 13

6. 5 april 2004 J.M. Zwarthoed6 Analyses crack width calculations reinforced concrete slab five different calculation methods concrete slab: K300 (  C20/B25), CEM I rebars:  16-200 QR40 f s = 329 N/mm 2 (  FeB 400) hot rolled steel cracked section crack width during and after completion of crack development phase

7. 5 april 2004 J.M. Zwarthoed7 Comparison result calculations appr. region of steelstresses SLS

8. 5 april 2004 J.M. Zwarthoed8 Crack width calculation pre-stressed concrete slab concrete bridge deck: B37,5 (  C30/37) CEM I rebars:  12-250 FeB 400 hot rolled steek pre-stressing: 35·1182 mm 2 FeP 1860 M d /M u = 21988/23145= 0,95 [kNm/kNm] M rep = 14659 kNm

9. 5 april 2004 J.M. Zwarthoed9 Result calculations bridge deck meets all requirements ULS except fatigue, meets none with regard to SLS assumption: no imposed deformations during stage of development crack pattern w max = 0,4 mm in case of fully developed crack pattern w max = 0,32 mm

10. 5 april 2004 J.M. Zwarthoed10 Conclusions (1) The first main problem is: insufficient transversal rebar reinforcement in decks causing cracks according to model 1, 2, 5 and 13 with w max  0,2-0,4 mm.

11. 5 april 2004 J.M. Zwarthoed11 Conclusions (2) The second main problem is: insufficient longitudinal rebar reinforcement in combination with main pre-stressing reinforcement causing cracks according to model 6, and 7 with w max  0,5 mm; insufficient longitudinal rebar reinforcement causing cracks according to model 11 and 12 with w max  0,2-0,4 mm.

12. 5 april 2004 J.M. Zwarthoed12 Note! One has to keep in mind the following aspects: We assume the calculated crack width according to NEN 3880 as an upper limit. Calculations bases on the 28 th- day concrete strength. Did the actual SLS loading occur?