TABLE OF FIGURES

Seismic Evaluation of two Steel Silos in Ilva’s Plants 1

TABLE OF FIGURES

Figure 1-1:Aerial view of Tupras refinery after the Kocaeli earthquake ... 5

Figure 1-2:Explosion into the Fukushima nuclear plant after the earthquake. ... 6

Figure 1-3: Elevated Silos. ... 8

Figure 1-4: Failure Elevated Silos. ... 9

Figure 1-5:Ilva plant, Taranto. ... 12

Figure 2-1: Pictures of the Elevated Silos. ... 13

Figure 2-2: Section view at the first level. ... 14

Figure 2-3: Elevated view of whole structure... 15

Figure 2-4: Main supporting structure: six columns HEA 340, horizontal and vertical bracings. ... 16

Figure 2-5: Arrangement of beams on the first storey. ... 16

Figure 2-6: Elevated Silos with detail of supporting structure. ... 17

Figure 2-7: Horizontal bracing and X-bracing hinged to the plate,4 diagonals of X-bracing hinged to the plate. ... 17

Figure 2-8: Detail of connection between circular sheets of the silo. ... 18

Figure 2-9: Detail of bolted connection at the 1^st floor. ... 19

Figure 2-10: Detail of welded connection at the top floor. ... 19

Figure 2-11: Front and lateral Elevation of bucket elevator. ... 20

Figure 2-12: Detail of connection between silo and elevator. ... 21

Figure 2-13: Front and Lateral Elevation of staircase. ... 22

Figure 2-14: Detail of connection between stairs and silo. ... 23

Figure 2-15: Detail of connection between stairs and top floor of the silo. ... 23

Figure 2-16: Front and Lateral Elevation of Foundation. ... 24

Figure 2-17: Filling and discharge sequence. ... 25

Figure 3-1: local coordinate system of beam. ... 27

Figure 3-2: local coordinate system of shell. ... 28

Figure 3-3:Finite element model of elevated silos. ... 28

Figure 3-4: Cross-section shape according EN 1991-4-1.1.2. ... 30

Figure 3-5: Silos dimensions. ... 31

Figure 3-6: Filling pressures in the vertical-walled segment according to EN1991-4-5.2.1.1(1)... 35

Figure 3-7: Distribution of filling pressures in the vertical-walled segment according to EN1991-4-5.2.1.1(1). ... 37

Figure 3-8: Boundary between steep and shallow hopper. ... 39

Figure 3-9: Normal pressure pnf and frictional traction ptf on the wall of shallow hopper. ... 40

Figure 3-10: Distribution of filling pressures in the shallow hopper according to EN1991-4-6.4.2(2). ... 41

Figure 3-11: Distribution of filling pressures due to hydrated lime stored on silos. ... 42

Figure 3-12: Distribution of Mean wind velocity. ... 46

Figure 3-13: Distribution of Peak velocity pressure. ... 47

Figure 3-14: Wind loaded silo. ... 48

Figure 3-15: Wind pressure variation around half circumference of silo in group. ... 48

Figure 3-16: Distribution of Normal pressures ∆ ℎ, in the hopper for θ=0. ... 52

Figure 3-17: Distribution of Normal pressures ∆ ℎ, in the vertical walls for θ=0. ... 52

Figure 3-18: The Soil profile of the area. ... 56

Seismic Evaluation of two Steel Silos in Ilva’s Plants 2

Figure 3-19: Taranto elastic spectrum of ULS. ... 60

Figure 3-20:First global modal shapes including supporting structure response. ... 64

Figure 4-1:Flowchart showing steps followed to complete an analysis in ABAQUS. ... 68

Figure 4-2: Assembly of four main parts. ... 70

Figure 4-3: Line that represent the cross section of the silo body. ... 71

Figure 4-4: Modelling of connection of silos to the footpath. ... 71

Figure 4-5: Beam naming convention. ... 73

Figure 4-6:Assembly of silos and mesh of silo (shell elements) and supporting structure(beam elements). 74 Figure 4-7: Non-structural mass applied to silos. ... 75

Figure 4-8: First global modal shapes including supporting structure response ... 76

Figure 4-9: Material defining in Abaqus. ... 79

Figure 4-10: Stress-strain curve for S275. ... 79

Figure 4-11: Initial lateral imperfection in X-frame system. ... 82

Figure 4-12: Axial-Displacement of the X-brace system. ... 85

Figure 4-13: Viscous damping energy and the total strain energy of the model. ... 86

Figure 4-14: Monotonic analysis of X-frame system. ... 86

Figure 4-15: The P-Δ curve of a brace in compression. ... 87

Figure 4-16: The P-Δ curve of a brace in tension. ... 87

Figure 5.1: Base Shear- Displacement in X direction. ... 89

Figure 5.2: Base Shear- Displacement in X direction. ... 89

Figure 5.3: Failure in X-direction. ... 90

Figure 5.4: Failure in Y-direction. ... 91

Figure 5.5: Simplified model. ... 92

Figure 5.6: Base Shear- Displacement in both direction. ... 92

Figure 5.7: Single-storey CBF with braces meeting on one side of columns between floors. ... 93

Figure 5.8: Monotonic analysis of a continuous diagonal of the X-bracing system. ... 94

Figure 5.9: Force-Displacement continuous diagonal. ... 95

Figure 5.10: Base Shear- Displacement in both direction. ... 95

Figure 5.11: Pushover analyses with imperfection and nonlinear springs. ... 96

Figure 5.12: Pushover analyses for one silo and for both silos. ... 97

Figure 5.13: Taranto elastic acceleration and displacement spectrum for 5% damping normalized to 1g peak ground acceleration... 98

Figure 5.14: AD format. ... 98

Figure 5.15: Force displacement relation of the equivalent SDOF system. ... 101

Figure 5.16: Elastic and inelastic demand spectra versus capacity diagram. ... 102

Figure 5.17 Limit states on Push-over Y ... 104

Figure 5.18 Verification according N2 method in AD format, Y direction ... 105

Figure 5.19 Limit states on Push-over X ... 105

Figure 5.20 Verification according N2 method in AD format, X direction ... 106

Figure 6-1: Examples of dissimilar response behavior of IDA-curves (X-Axis: Damage Measure; Y-Axis: Intensity Measure. ... 108

Figure 6-2: The relation between damping ratio and the period. ... 110

Figure 6-3: Damping coefficient implemented on Abaqus... 110

Figure 6-4: IDA for Lazio, Friuli and Tabas. ... 112

Figure 6-5: Accelerogram in Y-direction, Friuli. ... 112

Seismic Evaluation of two Steel Silos in Ilva’s Plants 3

Figure 6-6: Content in frequency in Y-direction, Friuli. ... 113

Figure 6-7: Content in frequency in X-direction, Friuli. ... 113

Figure 6-8: Accelerogram in X-direction, Lazio. ... 113

Figure 6-9: Content in frequency in X-direction, Lazio. ... 114

Figure 6-10: Content in frequency in Y-direction, Lazio. ... 114

Figure 6-11: Behaviour factor Friuli IDA. ... 115

Figure 6-12: Behaviour factor Lazio IDA. ... 115

Figure 6-13: Behaviour factor Tabas IDA. ... 116

LIST OF TABLES

Table 3-2:Particulate solids properties according to EN 1991-4 Annex E2 ... 33

Table 3-3: Intermediate slenderness silos, according to EN1991-4-5.1(2). ... 34

Table 3-4: Geometric parameters used to calculate horizontal and vertical pressures. ... 36

Table 3-5: Geometric parameters used to calculate horizontal and vertical pressures. ... 37

Table 3-6: Hopper shapes. ... 38

Table 3-7:Geometric parameters used to calculate horizontal and tangential pressures. ... 41

Table 3-8: Geometric parameters used to calculate horizontal and vertical pressures. ... 41

Table 3-9: Maps of the areas that Italian territory is subdivided. ... 44

Table 3-10: Terrain categories and terrain parameters. ... 45

Table 3-11: Bucket elevator weight. ... 49

Table 3-12: Parameters used to calculate horizontal seismic actions due to the weight of silo and the particulate material for each silo. ... 50

Table 3-13: Parameters of , 0, ∗. ... 53

Table 3-14: Working life category. ... 54

Table 3-15: Important buildings class. ... 54

Table 3-16: The probability of exceedance, ,in function of each performance level. ... 55

Table 3-17: Reference return period associated to the corresponding limit state. ... 55

Table 3-18: Ground type coefficients. ... 58

Table 3-19: Topography type coefficient. ... 58

Table 3-20: values of parameter for vertical elastic response spectrum. ... 59

Table 3-21: values of factor obtained from Nation Annex EN 1991-1-1-1. ... 60

Table 3-22: values of and ξ factor obtained from EN 1991-4. ... 60

Table 3-23: values of and ξ factor obtained from EN 1991-4. ... 61

Table 3-24: Cross-section check, permanent and temporary situation . ... 62

Table 3-25: Buckling verification, combined axial compression and bending about both axes. ... 62

Table 3-26: Cross-section check, Lateral force method ... 63

Table 3-27: Buckling verification, combined axial compression and bending about both axes, Lateral force method. ... 64

Table 3-28: Modal dynamic properties of the silos. ... 65

Table 3-29: Cross-section check, Modal response spectrum. ... 67

Table 3-30: Buckling verification, combined axial compression and bending about both axes, Modal response spectrum. ... 67

Seismic Evaluation of two Steel Silos in Ilva’s Plants 4

Table 4-1:Eigen value output. ... 77

Table 4-2:Participation factor. ... 77

Table 4-3:Effective mass. ... 77

Table 4-4: Natural period comparison for the whole model and one silo. ... 77

Table 4-5: Buckling loads in-plane and out-of-plane of continuous diagonal. ... 83

Table 4-6: Buckling loads in-plane and out-of-plane of discontinuous diagonal. ... 83

Table 4-7: Design values of initial bow imperfection according to EN 1993-1-1 (2005). ... 84

Table 4-8:magnitude of bow imperfection. ... 84

Table 5-1 Axial deformation capacity of braces in tension ... 103

Table 6-1:Details of the selected ground motion records. ... 111

Table 6-2 : q factor. ... 116