Foreword
The United States Society on Dams recognizes that with
an aging infrastructure, new demands (not perceived at the time of
construction) are being placed on owners of dams to ensure safe and reliable
operation and maintenance. One unique aspect of dam safety that has recently
received increased attention is the gated spillway. Spillway gates have not
always been attributed due respect with regard to periodic test-operation and
maintenance because reliability of the gate structure and operating machinery
was either considered inherent with the design or was simply neglected
altogether. Dam safety was not necessarily identified with the inability to
operate a spillway gate. Recent gate incidents, identified herein, illustrate
that problems with spillway gates and gate operating equipment do exist, are
all too often repetitive, and have the potential to affect overall dam safety.
The USSD Hydraulics Committee commissioned its
Subcommittee on Gates and Valves to develop this report as a source of
practical experience and information to achieve long-term reliability of spillway
gate operation.
Experience has shown that improving spillway gate
reliability is a combination of proper component selection, good design
details, appropriate operation and maintenance procedures, and the application
of proven inspection and evaluation techniques. This report is a compendium of
demonstrated engineering, design, operation, and inspection procedures based on
the experiences of various dam owners and operating agencies in the United
States. Whether selecting, designing, operating, and/or maintaining spillway
gates, the reader will benefit from the collective experience of the authors
involved with the development of this report. The information provided is
comprehensive, applicable to new construction, major renovation or
rehabilitation of existing projects, and operation and maintenance of existing
gated spillways.
Improving spillway gate reliability requires a
concerted effort among owners, operation and maintenance personnel, and
designers. This report was developed with the intention to benefit anyone
associated with gated spillway structures - whether it is ownership, operation,
maintenance, design and/or regulatory responsibility.
Owners and operating personnel will learn about
recommended maintenance and test- operation procedures; designers will benefit
from information and references regarding design criteria, methods, and
procedures; and regulators will get a better understanding of the role that
gated spillways have in dam safety. The reader will be introduced to the more
common types of spillway gates and gate operating equipment. Recommendations
are provided regarding important features that should be considered in
selecting and designing new spillway gates or rehabilitating existing spillway
gates to improve performance and reliability. Also, information concerning
operation, maintenance, inspection, and evaluation of gates and gate operating
systems is presented. Various types of spillway gates (past and present) are
described with respect to function, operation, limitations, and weaknesses. The
anatomy of a spillway gate is explained, and contrasted with potential modes of
failure.
Each project is unique. Design details, manufactured
components, procedures used to operate or maintain a project, etc. vary from
owner to owner and even from project to project within an organization. This
report does not attempt to address all possible design and operating conditions
that an agency or project may experience. However, many of the situations,
recommendations, and procedures provided herein are general in nature, with a
logical methodology that when followed will improve the longevity and
reliability of spillway gate operation.
The focus of the report is on structural, mechanical
and electrical considerations of spillway gate operation. Hydraulic design and
hydrological engineering needed to determine size of spillway and/or number and
size of spillway gates is not discussed. Also, it is not intended to be a design
manual, but reference is made to many design documents that provide information
on the latest design methods and procedures.
Regardless of the level of experience, the depth and
breadth of the topics covered in this report can provide assistance to anyone
involved with engineering and operation of gated spillway systems. Ultimately,
the public will benefit from the knowledge provided by this report through
improved design and safe operation of water resource projects in their
community.
Report Contributors
B.T.A. Sagar
Bernard J. Peter
Henry W. Stewart
Edward A. Serfozo
Alfred M. Waddell
Daniel J. Casapulla
D. Craig Evans
Chander K. Sehgal
Table of Contents
CHAPTER 1 - INTRODUCTION
1-1. Background
CHAPTER 2 - GATE TYPES AND APPLICATIONS
2-1. Introduction
2-2. General Arrangement
2-3. Radial Gate
a. General
b. Operation
c. Selection
2-4. Vertical-Lift Gate
a. General
b. Fixed-Wheel and Roller-Mounted Gates
2-5. Drum Gate
a. General
b. Arrangement
c. Anchorage
d. Operation
2-6. Hinged Crest Gate
a. General
b. Leaf
c. Anchorage
2-7. Inflatable Gates
a. General
b. Rubber Dam
c. Obermeyer Gate
2-8. Flashboards
a. General
b. Spillway Flashboards
c. Gate Flashboards
2-9. Fuse Gates
2-10. Maintenance Gates
a. General
b. Bulkhead Gates
c. Floating Bulkheads
d. Stoplogs
e. Needles
2-11. Gate Operating Systems
a. General
b. Wire Rope Hoists
c. Chain Hoists
d. Hydraulic Hoists
2-12. Recommendations
CHAPTER 3 - DESIGN PRACTICES
3-1. Introduction
3-2. Design Criteria
a. General
b. Working Stress
c. Factor of Safety
3-3. Loads and Allowable Stress
3-4. Structural Analysis of Radial Gate
a. Member Definitions
b. Material Properties
c. Loads
d. Gate Load Cases
e. Verification of Models
f. Allowable Stresses
g. Results
3-5. Analysis of Other Gates & Features
a. General
b. Gate Anchorage
c. Contacting Solids
3-6. Materials
a. General
b. Standards
c. Materials
d. Severe Exposure
e. Applications
3-7. Fabrication
a. Introduction
b. Shop Fabrication vs. Field Fabrication
c. Designer's Role in Fabrication
d. Welding vs. Castings vs. Forgings
e. Heat Treatment of Steel
f. Bolts
g. Galvanizing
3-8. Seal Systems
a. General
b. Rubber Sealing Systems
c. Radial Gate
d. Hinged Crest Gate
e. Vertical-Lift Gate
3-9. Overtopping Flow
a. General
b. Overtopping Design
3-10. Rehabilitation
a. Bolted Connections
b. Welding
3-11. Design Considerations
3-12. Hoist Selection and Design
a. General
b. Design Criteria
c. Improving Reliability
CHAPTER 4 - INVESTIGATION AND EVALUATION
4-1. Introduction
4-2. Failure Scenarios
4-3. Gate Components
4-4. Safety Evaluation
a. Introduction
b. Design Review
c. Radial Gates
d. Vertical-Lift Gates
e. Hinged Crest Gates
f. Inflatable Gates
g. Fuse Gates
4-5. Gate Operating Systems
a. System Evaluation
b. Wire Rope Hoists
c. Chain Hoists
d. Hydraulic Hoists
e. Other Systems
4-6. Field Inspection
a. General
b. Gate Structure
c. Trunnions
d. Anchorage
e. Seals
f. Operation
4-7. Gate Vibration
a. Introduction
b. Seismic Activity
c. Flow Variations
d. Stick/Slip Motion
4-8. Ice Difficulties
a. Gate Problems
b. Operating Problems
CHAPTER 5 - AUTOMATION
5-1. Background
a. Introduction
b. Mechanically Float-Operated Gates
c. Electrically Operated Gates
d. Computer Operated Gates
5-2. Spillway Gate Control
a. General
b. Local-Manual Control
c. Remote-Manual Control
d. Local-Automatic Control
e. Remote-Automatic Control
f. Local Semi-Automatic Control
5-3. Spillway Gate Automation
a. General
b. Operational Risks
c. Operational Benefits
d. Constant Reservoir Water Level
e. Dam Safety
5-4. Automation Design Requirements
a. General
b. Operational Strategy
c. Simulation and Analysis
d. Control Algorithm Development
5-5. Automation Equipment Requirements
a. General
b. Gate Hoists
c. Hoist Motors
d. Electrical Controls
e. Instrumentation
f. Data Acquisition
g. Weather Stations
5-6. Automation Equipment Selection
a. General
b. Gate Hoists
c. Measurement Wells
d. Power Supply
e. Communication System
f. PLC and RTU Equipment
5-7. Conclusion
APPENDIX A - REFERENCES
APPENDIX B - EXAMPLES OF GATE INCIDENTS
APPENDIX C - TRUNNION LUBRICATION
APPENDIX D - TEST OPERATION OF SPILLWAY GATES
APPENDIX E - BALANCING CRITERIA
APPENDIX F - DESIGN EXAMPLES
APPENDIX G - MAINTENANCE AND INSPECTION GUIDELINES
APPENDIX H - FIGURES
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