Performance-Based Seismic Bridge Design (2013) / Chapter Skim
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37 CHAPTER SIX DAMAGE ANALYSIS Some general observations, taken from Cooper et al.
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38 program. Reconnaissance information can be found in the LFE Reconnaissance Archive (http://www.eeri.org/projects/ learning-from-earthquakes-lfe/lfe-reconnaissance-archive/)
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39 FIGURE 13 Typical bridge damage: (a) Cypress Viaduct collapse (Loma Prieta, 1989)
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40 TABLE 10 BRIDGE DAMAGE AND PERFORMANCE ASSESSMENT Damage Level Damage Classification Damage Description (Damage Measures) Performance Level I No • Onset of hairline cracks Fully operational II Minor • Crack widening • Theoretical first yield of longitudinal reinforcement Operational III Moderate • Initiation of inelastic deformation • Onset of cover concrete spalling • Development of diagonal cracks Limited damage IV Major • Formation of very wide cracks • Extended concrete spalling Life safety V Local failure/ collapse • Buckling of main reinforcement • Rupture of transverse reinforcement • Crushing of core concrete Collapse TABLE 11 BRIDGE PERFORMANCE/DESIGN PARAMETERS SRPH-1 (HOSE AND SEIBLE 1999)
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41 FIGURE 15 Bridge column damage at various damage levels SRPH-1 (Hose and Seible 1999)
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42 TABLE 12 REINFORCED CONCRETE AND STRUCTURAL STEEL MEMBER DAMAGE STATES Reinforced Concrete Damage States Structural Steel Damage States Concrete cracking First yield Cover concrete spalling Local buckling (e.g., flange or web) Core concrete crushing Lateral torsional buckling Yield of the longitudinal reinforcement Brace buckling Fracture of the transverse reinforcement Fatigue cracking Buckling of the longitudinal reinforcement Connection fracture (e.g., bolt or weld)
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43 (e.g., AASHTO SGS) or rotation (e.g., ASCE 41)
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44 FIGURE 17 Trends in nominal compressive strain at cover spalling, circular columns (Berry and Eberhard 2003)
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45 Although there has been considerable research investigating the effects of cumulative damage processes (Manson 1953; Coffin 1954; Manson and Hirshberg 1964; Mander et al.
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46 If the distribution of component strength is superimposed onto the nonlinear force-displacement response of a reinforced concrete column (as in the upper portion of Figure 20) , significant strength levels can be identified.
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47 The probabilistic treatment of damage can then be applied to PBSD in several different ways. First, the damage fragility functions can be used to generate deformation (strain, rotation, or drift)
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48 • Damage-resistant plastic hinges • Load path control. These concepts will be briefly discussed to show their applicability to increasing the seismic performance of bridge structures.
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49 cepts is illustrated in Figure 22, which shows acceleration and displacement elastic response spectra. In general (for smooth or design spectra, short-period range excluded)
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50 quake-induced damage and achieving heightened seismic performance levels. If the structural configuration and site conditions permit, seismic isolation can be an effective and elegant solution for controlling structural performance.
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51 developed by the building community for use in PBSD of buildings, as described earlier. Load Path Control The final method of damage reduction is to control the lateral load path.
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52 TABLE 13 BRIDGE GEOMETRIC CONSTRAINTS ON SERVICE LEVEL (MCEER/ATC, 2003) Permanent Displacement Type Possible Causes Mitigation Measures Immediate Significant Disruption Vertical Offset • Approach fill settlement • Bearing failure • Approach slabs • Approach fill stabilization • Bearing type selection 0.083 ft.
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53 that represents the consensus opinion of the workshop participants. Geometric constraints generally relate to the usability of the bridge by traffic passing on or under it.
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