GNDT-Monografie: Pinto, Monti

Vulnerability evaluation and strengthening criteria for R.C. bridges

P.E. Pinto e G. Monti (A cura di)

1	Introduction		4
2	Bridge systems		9
	2.1 Analytical seismic assessment of the bridges on a highway system		9
	2.2 Screening of the bridges to be examined		10
		2.2.1 Hazard analysis	11
		2.2.2 Natural seismic resistance	12
		2.2.3 Final selection of bridges	14
	2.3 Evaluation of the bridges		15
		2.3.1 Outline of the procedure	15
		2.3.2 The data bank SAMOA	16
		2.3.3 Simulated design of the piers	17
		2.3.4 Evaluation procedure	17
		2.3.5 Quantification of risk	19
		2.3.6 Selacted results	21
	2.4 Acceptance criterion		23
		2.4.1 Calculation of f P for g A* = 0.35g*	24
	2.5 Results and conclusions		26
	2.6 References		26
3	Important Phenomena affecting the bridge response		27
	3.1 Multi-support excitation		27
		3.1.1 Soil motion	28
		3.1.1.1 Spatial model for ground motion	28
		3.1.2 Convertional bridges	36
		3.1.2.1 Design of the bridges	37
		3.1.2.2 Elastic response	39
		3.1.2.3 Non linear response of bridges to multi-support excitation	44
		3.1.2.4 Bridges with non-synchronous design	44
		3.1.2.5 Bridges with synchronous design	47
		3.1.2.6 Conclusions regarding conventional bridges	49
		3.1.3 Isolated bridges	52
		3.1.3.1 Bridge model and equivalent stiffness and damping ratio of the isolator	52
		3.1.3.2 Equations of motion of the bridge	53
		3.1.3.3 Response of the isolators	54
		3.1.3.4 Treatment of damping	55
		3.1.3.5 Iterative procedure	56
		3.1.3.6 Design of the isolated bridge	57
		3.1.3.7 Results of the analyses	58
		3.1.4 References	65
	3.2 Soil-structure interaction		68
		3.2.1 Mechanical model and equation of motion	71
		3.2.1.1 Superstructure	71
		3.2.1.2 Foundation and foundation soil	72
		3.2.1.3 Effective damping of the soil-structure system	74
		3.2.1.4 Seismic input	75
		3.2.1.5 Equation of motion	75
		3.2.2 Cases examined	76
		3.2.3 Results	79
		3.2.4 Conclusions	86
		3.2.5 References	86
	3.3 Vertical oscillations		88
		3.3.1 The analyzed structures: geometry and dimensioning	89
		3.3.2 The numerical models for non-linear time-hystory analyses	93
		3.3.3 Results of non-linear analyses	95
		3.3.4 Simple mechanical model for axial vibrations	101
		3.3.5 Conclusions	105
		3.3.6 References	106
4	Upgrading of bridge piers with FRP		108
	4.1 Properties and behavior of FRP-confined concrete		108
		4.1.1 Basis model for unconfined concrete	108
		4.1.2 Concrete model with elastic confinement	110
		4.1.3 Some considerations on modeling concrete confined with steel or FRP	112
		4.1.4 Comparison with experimental results	116
		4.1.4.1 Tests by Picher et al. (1996)	117
		4.1.4.2 Tests by Kawashima et al. (1997)	118
		4.1.4.3 Tests by Mirmiran and Shahawy (1997)	119
		4.1.5 Predictive equations of FRP-confined concrete properties	121
		4.1.6 Agreement with experiments	122
	4.2 Response of FRP-wrapped sections		124
		4.2.1 Assessment of FRP-confined section model	128
		4.2.2 Parametric study on FRP-confined sections	130
	4.3 Design criteria for upgrading through FRP wrapping		134
		4.3.1 Upgrading index of FRP-wrapped pier sections	135
		4.3.2 Mechanical Model of the Upgrading Index	136
		4.3.3 Considerations over the error functions E	140
		4.3.4 Comparison between analytical and numerical indices	141
		4.3.5 Use of the upgrading index for design of FRP jackets	144
		4.3.6 Design Example	146
		4.3.7 Ductility upgrading of piers in seismic regions	146
	4.4 Conclusions		148
	4.5 References		149

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