An upright cylindrical tank is a highly efficient structure for storing liquids such as drinking water, sprinkler water, crude oil, LNG, wines and juices. During earthquakes, a complicated pattern of stress is generated in the tank. Poorly designed tanks have leaked, buckled or even collapsed during earthquakes. Common modes of failure are wall buckling, sloshing damage to roof, inlet/outlet pipe breaks and implosion caused by rapid loss of contents. In recent years, significant advances have occurred in linear and nonlinear dynamic analyses of tank-liquid-foundation systems. Significant advances have also occurred in site-specific estimates of ground motion parameters. Modern seismic analyses are based on probabilistic response spectrum rather than deterministic peak ground acceleration. This seminar will present a step-by-step discussion of advances in ground motion estimates and dynamic response analyses.

• Common modes of tank failure due to earthquakes
• Models for dynamic analyses 
  -  Ground-supported tanks 
  -  Elevated tanks
• Site-specific response spectra of horizontal and vertical motions
• Moments, base shear, axial and hoop stresses in tank wall
• Sloshing at free-surface 
  -  Freeboard requirement 
  -  Roof loads in tanks with insufficient freeboard
• Soil-structure interaction
• Nonlinear static (pushover) analysis of tanks
• Techniques for mitigating earthquake loads 
  -  Base isolation 
  -  Seismic energy dissipation
• AWWA, API and ACI seismic design standards

Upon completion of this seminar, you will be able to:

• Understand the two main modes of vibration of liquid in a tank
• Recognize the main types of seismic damage in a tank
• Understand why the response spectrum is needed to calculate the seismic response of a tank
• Identify the effects of insufficient freeboard in a tank
• Understand the limitations of code-based seismic design of tanks
• Understand how a risk-based seismic design is performed
• Identify different ways of improving the seismic performance of tanks

Achievement of the learning outcomes will be assessed through class participation.

Who Should Attend?

Structural and geotechnical engineers, planners, risk managers and manufacturers interested in design and performance assessment of tanks and foundations.

Summary Outline

Time:  8:00 a.m. - 5:00 p.m.

Introduction

• Past earthquake performance of tanks
• Model of tank-liquid system
• Impulsive, convective and breathing modes of vibration
• Ground-supported and elevated tanks

Design Response Spectrum

• Definition of response spectrum
• Response spectrum from ASCE 7-05
• Spectrum from site-specific analysis
• Displacement-sensitive region of response spectrum
• Spectrum of vertical motion
• Damping-adjustment of response spectrum

Seismic Response of Tanks

• Moments, base shear, axial and hoop stresses in tank wall
• Sloshing at free-surface
• Freeboard requirement
• Roof loads in tanks with insufficient freeboard
• Hoop stresses due to vertical motion

Special Topics

• Soil-structure interaction analysis
• Nonlinear static (pushover) analysis of tanks
• Base isolation
• Energy dissipating anchors