SHENG LIAN (Outline of Master Thesis, September 2020) Department of Civil Engineering, The University of Tokyo, Japan Shaking Table Tests on The Seismic Performance of Bridge Abutments with EPS And Soil Reinforcements in The Backfill . Geotechnical Engineering Laboratory, The University of Tokyo 2020 Introduction E xperimental models Results & Discussion Previous large earthquakes reported numerous damage cases on bridge abutments such as residual lateral displacements of abutment body and relative settlements at backfill-abutment wall interface. These damages disrupted normal traffic operation and hence posed a threat to post-earthquake rehabilitation and economic activities. In light of it, this study focuses on different soil reinforcement methods in the backfill in order to determine the optimal aseismic countermeasure layout that is both effective and practically applicable on site. Tohoku earthquake (2011) Kumamoto earthquake (2016) Previous research Expanded Polystyrene (EPS), geogrids and soil nails are three main types of soil reinforcement methods adopted in the field. Previous research focused on the combined use of these reinforcements for existing structures, but the effects of different geometries or material properties of reinforcements were not fully studied. This study hence investigated how EPS stiffness and nail length/diameter affect overall structure seismic performance. Specifically, EPS of lower stiffness and through-out soil nails penetrating from the top of abutment body to subsoil layer were adopted. EPS of lower stiffness Through-out type soil nails Loadcells Scale : 1:20; Material : Aluminum Weight : 48.7kg; Volume : 0.0194m 3 Unit weight : 25.1kN/m 3 à simulate comparable seismic responses as prototype Static load Girder Supporting frame Abutment Rollers Backfill Surcharge Soil foundation Shaking table Shaking direction Scale : 1:20 one end : attached to abutment top via hinges the other end : with rollers on a supporting frameàfacilitates girder sliding under seismic input. Lead ingots Rubber bands 0.39kPa 0 2 4 6 8 10 12 14 0 500 1000 Tilting angle (degrees) Base acceleration (gal) Through- out Through-out + softer EPS No countermeasures Shortened Through-out + ordinary EPS 1. Softer EPS , more suppressed tilting 2. Shortened nail not adequate 0 0.2 0.4 0.6 0.8 1.2 1.4 1.6 1.8 0 500 1000 Net seismic soil force (kN/m) Base acceleration (gal) Shortene d Through-out + softer EPS No countermeasures Through-out + ordinary EPS 1. Addition of EPS , profound reduction in soil force 2. Softer EPS, further attenuation & more gradual increase Through-out 0 20 40 60 80 100 120 140 160 180 0 500 1000 1500 Settlement (mm) Base acceleration (gal) Through-out Through-out + softer EPS Through-out + ordinary EPS 1. Through-out nail alone not enough in inhibiting settlement No countermeasures Shortened 3. Addition of EPS , improve settlement (EPS uplifting) 2. No further reduction despite softer EPS No reinforcement Through- out nail Shortened through-out nail Through-out + softer EPS Through-out + ordinary EPS E xperimental cases 5 out of the 12 cases were selected for parametric study purpose. Seismic performance of the abutment model was evaluated against parameters shown in the figure circled. C onclusions Merits : ✓ consistent and continuous tensile force (nail) ✓ better attenuation of seismic soil force (softer EPS) ✓ practical applicability (shallow excavation) Proposed Through-out + softer EPS ① To confirm benefit of through-out type nails ② To verify length effect ③ To investigate benefit of EPS backfill ④ To check stiffness effect of different EPS Tilting and lateral displacement ↓ - Inadequate if shortened / - Deep nail penetration needed - Relative settlement ↓ (uplift) - Soil force & overturning moment ↓ - Soil force & moment further↓ (if softer) - Settlement condition almost unchanged