Earthquake Engineering Research Needs for Hydraulic Structures

Transcription

1 Earthquake Engineering Research Needs for Hydraulic Structures Dr. Robert L. Hall Geotechnical and Structures Laboratory U.S. Army

2 Introduction ERDC LABORATORIES Cold Regions Research Engineering Laboratory Hanover, NH Construction Engineering Research Laboratory Champaign, IL Topographic Engineering Center Alexandria, VA Coastal and Hydraulics Laboratory Environmental Laboratory Geotechnical and Structures Laboratory Information Technology Laboratory Vicksburg, MS Waterways Experiment Station (WES)

3 Introduction GEOTECHNICAL AND STRUCTURES LABORATORY Airfields and pavements research. Concrete technology. Earthquake Engineering Research Program. Geotechnical engineering. Hydraulic and navigational structures. Military vehicle mobility. Structures response to weapons effects. Terrorist threat protection Centrifuge research Airfields Seismic safety evaluation

4 Introduction OUR CONCERN: HYDRAULIC STRUCTURES! Locks! Conventional and RCC gravity dams, arch dams! Intake towers! Earth retaining structures! Powerhouses

5 ERDC Research Activities MOTIVATION: POTENTIAL SAVINGS At least 72 large intake towers are located in seismically active areas, almost all are very lightly reinforced. The cost of retrofitting an existing tower has been estimated to be between $5 million and $100 million. Proper estimation of capacity has a large potential payoff.

6 ERDC Research Activities AN EXAMPLE: SEVEN OAKS INTAKE TOWER REDLANDS SANTA ANA RIVER TOP OF DAM EL SPILLWAY INTAKE TOWER

7 ERDC Research Activities SEVEN OAKS INTAKE TOWER (cont.)

8 ERDC Research Activities EXPERIMENTAL WORK AT ERDC Acceleration [g] Time [sec] Load (lb) ITS-3 Top Def. ITS-3 Duct Measured Top Deflection (in) Tower model on shake table Intake Tower Experiments: Cyclic and Dynamic Response Characteristics

9 ERDC Research Activities EXPERIMENTAL WORK AT ERDC Mode 1 Mode 2 Mode 3 Mode 4 Mode 5

10 ERDC Research Activities SOIL-STRUCTURE INTERACTION ISSUES Success Dam - Partially embedded control tower

11 ERDC Research Activities LARGE STRUCTURES, BIG PROBLEMS: CONCRETE DAMS The seismic performance of concrete dams is governed by a series of complex dynamic interactions between the structure, the water, and the foundation rock. This is complicated by nonlinear effects, such as those associated with the tensile behavior of the mass concrete and contraction and lift joints. Foundation Rock Arch Dam (b) Reservoir Water Dam-Water Interface (a) Half of Dam and Foundation

12 ERDC Research Activities UNBOUNDED DOMAINS: MODELING ENERGY ABSORPTION EFFECTS Standard time-domain FE programs do not consider energy absorption effects associated with sediments and foundation. Non-absorbing boundaries may lead to unrealistically large earthquake response of reservoir-dam-foundation system. Development of improved foundation models in collaboration with Prof. A. K. Chopra (UC-Berkeley).

13 Research Needs RESEARCH NEEDS Large scale validation of nonlinear models to represent dynamic behavior of mass concrete, contraction joints and dam-foundation interface.

14 Research Needs RESEARCH NEEDS Time-domain characterization of energy absorption effects associated with reservoir and foundation rock.

15 Research Needs RESEARCH NEEDS Practical procedures to account for spatial variability of seismic ground motions in seismic evaluation of massive concrete structures.

16 Research Needs RESEARCH NEEDS Validated methodology for performance evaluation of lightly reinforced structures accounting for soil-structure and waterstructure interaction effects Analytical Results Analytical Results Load (kip) Load (kip) Without Pullout ITS-2 Experiment With Pullout ITS-2 Experiment Deflection (in) Deflection (in) Steel model without pullout Predicts concrete cracking but shows no strength degradation, results in wider loops. Steel model with pullout Better agreement, except for initiation of cracks, shows strength degradation due to pullout.

17 Research Needs RESEARCH NEEDS Current nonlinear constitutive models still need validation (different from calibration). Validation should be performed through! Full scale testing (field).! Reduced scale testing (shake table tests).! Small scale testing (centrifuge experiments).

18 Research Needs RESEARCH NEEDS Improved performance indices for qualitative damage estimation based on the characteristics of the system and the input ground motions. Application to seismic assesment and rehabilitation prioritization of the large USACE dam inventory. Cumulative duration (CD) [sec] Zone 1 No damage is expected Zone 2 Some damage is expected Zone 3 Severe damage is likely Demand-capacity ratio (DCR)

19 Research Needs CONCLUSIONS Driving issues:! Massive structures.! Critical structures.! Large number of structures.! Aging infrastructure issues. Developing stronger partnerships:! Cooperative research with universities.! Collaboration with Prof. J. H. Prevost (Princeton Univ.)! Effective tech transfer to private sector (validated tools, consistent criteria documents, technical support).

20 ERDC Research Activities EARTHQUAKE ENGINEERING RESEARCH PROGRAM ERDC Civil Works Research Program. Location: Geotechnical and Structures Laboratory. Annual review process (USACE Districts). Two main areas: Geotechnical Aspects Structural Aspects