Structural Failures Cost Lives and Time

Transcription

1 Structural Failures Cost Lives and Time Recent failures of storage bins, silos and other structures highlight the need to increase awareness of hazards associated with these structures. Since 2010, one miner was killed when a storage bin collapsed; another miner was killed when the concrete silo he was standing on collapsed. These deaths and several near misses are alarming. Careful examination and prompt correction of hazards are essential to maintaining these structures. These occurrences can be greatly reduced by utilizing the following best practices. Examine structures for indications of damaged, weakened or displaced structural elements, bulging or deformed bin sides or tops, gapped joints, cracked or broken concrete, corroded or fatigue-cracked metal, bent or buckling columns, beams or braces, loose or missing connectors, cracked, broken or inadequate welds, etc. Inspect structural elements for reduced load-carrying capacity, thinned or missing sections of beam and column webs or flanges, corroded rusted or flaked metal surfaces, delaminated plywood or water-weakened wooden structures. Clean accumulations of material from around the base of structures and flanges of horizontal beams. Carefully inspect for damaged support columns, braces, anchor bolts and eroded foundations. Report all areas where indications of structural weakness are found. Protect lower level structural elements from collision damage by mobile equipment. Minimize spillage and eliminate the source promptly. New structures should be designed and certified as appropriate by a registered professional engineer in accordance with local building codes and in conformance with accepted engineering practices. Significant modifications to existing structures should be undertaken only after consultation with an engineer. Structures should be constructed according to plans and specifications by trained workers using good materials and employing generally accepted construction methods. Report Structural Damage or Deterioration To Your Supervisor

2 PowerPoint prepared by Terry Taylor, P.E., Senior Civil Engineer, PSHTC 1

3 Structural Condition Assessments 2

4 Structural Materials Steel Concrete (plain, reinforced, pre-stressed) Timber Other - Masonry, Aluminum, Fiber- Reinforced Polymer (FRP), etc. 3

5 Inspecting Structural Steel Corrosion (holes,delamination & loss of cross section) Cracking (overload & fatigue) Overloads (buckling & deflection) Member Impact Damage 4

6 Corrosion holes & delamination 5

7 Reinforced Concrete Concrete is strong in compression but weak in tension. Rebar is introduced so that steel, which is strong in tension, can carry the tensile load while concrete carries the compressive load. 6

8 Inspecting Concrete Structures Cracking Delamination (Internal Splitting - Silos) Spalling Rebar Corrosion Crushing Impact Damage 7

9 Spalling & Corrosion from Exposure to Chemicals 8

10 Inspecting Timber Structures Cracking Deflection / Sag Crushing Fungi - molds, rot, dry rot Wood Boring Insect Damage 9

11 Inspection Tools Cleaning chipping hammer, wire brush Inspection chipping hammer, screw driver or icepick, plumb bob, flashlight, binoculars Measuring tape, calipers, ultrasound, level Safety & Misc. - safety harness, dust mask, compass 10

12 MNM Surface MNM Underground Safe Access Safe means of access shall be provided and maintained to all working places. 11

13 MNM Surface MNM Underground Machinery & Equipment Safety Defects b) Defects on any equipment, machinery, and tools that affect safety shall be corrected in a timely manner to prevent the creation of a hazard to persons. 12

14 MNM Surface MNM Underground Machinery, Equipment, & Tools Machinery, equipment, and tools shall not be used beyond the design capacity intended by the manufacturer where such use may create a hazard to persons. 13

15 Inspection of Processing Plants 14

16 Beams - Bending & Shear Resistance Beams and girders are common members used to resist bending moments and shearing forces. Bending is resisted by flanges; shear is resisted by web. 15

17 Bending Moment 16

18 Shear Force Equal (magnitude) but opposite (direction) forces which tend to slide one section of a member past an adjacent section. 17

19 Corroded web of wide flange beam 18

20 Long corrosion hole at web to flange interface 19

21 This beam was still standing (?) 20

22 Corrosion hole in web of beam (hidden by piping) 21

23 Corrosion holes in web of beam 22

24 Corroded end of beam 23

25 Corrosion hole in web & buckled top flange 24

26 Heavy delamination of bottom flange 25

27 Buckled web 26

28 Buckled webs of corroded channels 27

29 Beam modifications need engineered! 28

30 Columns Buckled column web corrosion hole 29

31 Corrosion hole in web of column 30

32 Buckled flanges at bottom of corrosion hole 31

33 Repaired column base (appears good) 32

34 Bad Repair At Column Base 33

35 Another Bad Column Repair (base) 34

36 a few feet up from base 35

37 Rotted timber column 36

38 An equipment mishap these types of repairs can be evaluated by an engineer 37

39 Crooked Column (creation of moment) 38

40 Severe equipment damage 39

41 Replacement time! 40

42 Inspect the column foundations 41

43 Don t take the bracings out! 42

44 Corroded diagonal brace 43

45 Corroded diagonal and gusset plate 44

46 Corroded diagonal 45

47 Corroded channels/girts supporting the siding 46

48 Check equipment supports! Corrosion hole in channel post for a magnetic separator 47

49 Corroded channel post support for a magnetic separator 48

50 Crack in a support beam for a shaker screen 49

51 Fractured spring support for vibrating equipment 50

52 Deteriorated concrete flooring 51

53 Floor slab cracks - a potential source of rebar corrosion 52

54 Look at floor grating - supports 53

55 Corrosion at support edge of grating 54

56 55

57 Corroded stair channels 56

58 Corroded angle supporting stair tread 57

59 Don t forget to check the handrails! 58

60 Corrosion holes in handrail support post 59

61 Heavy Roof Loading 60

62 Roof Collapse Due to Clinker Buildup and Snow Load 61

63 Inside of Failed Structure 62

64 Collapsing Roof Support Purlins 63

65 Corrosion of bottom flange of roof support channel 64

66 Buckled Vertical Roof Truss Member 65

67 Bolted Connections Check tightness Look for missing bolts sheared bolts elongated bolts excessive corrosion 66

68 Inspect connections! Corroded bolt heads 67

69 Welded Connections cracked welds poor quality - irregular surface corrosion in connected parts Always use qualified welders 68

70 Fractured connection 69

71 Vibrating equipment - fracture & poor quality weld 70

72 Irregular weld surface w/porosity 71

73 Exposed rebar on the side of a concrete settling tank 72

74 Collapsed floor Avoid this! 73

75 Plant collapses can be costly. 74

76 Recap - Inspection of Processing Plants Check the beams, columns, diagonal braces Examine members for buckling, corrosion, damage, excessive sag, holes, local buckling, and cracking. Examine connections for corrosion, missing or cracked elements Examine floors, roofs, walls, & foundation Examine equipment supports, stairways, & handrails 75