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EQUIPMENT SITE DESCRIPTION

Current United States research in earthquake engineering is lacking the capability to conduct real time shake

table testing of full or large-scale structural systems including soil-foundation-structure interaction (SFSI) at large or

close to full-scale. Also, experimental capabilities are required to simulate near source ground motions with large

velocity and displacement pulses. Existing shake table systems in the United States are limited by payload capacity

(base shear and/or overturning moment), pumping capacity, stroke, and overhead room to construct and test tallstructural systems. UCSD is providing the earthquake engineering community with a Large High Performance

Outdoor Shake Table (LHPOST) within the George E. Brown, Jr. Network for Earthquake Engineering Simulation

(NEES) collaboratory. This LHPOST, built at the University of California, San Diego (UCSD) as part of the Charles

Lee Powell Structural Research Laboratories, incorporates performance characteristics that allow the accurate

reproduction of near source ground motions for the seismic testing of very large structural and SFSI systems.

The primary benefits to society consist of archived "landmark experiments" that are most sought after because of

scale, completeness, and realistic seismic input ("the best in the world"), the most powerful archived experiments for

"outreach at all levels" such as K-12, college, news media, policy makers, infrastructure owners, insurance, etc., and

the verification of actual designs (at full-scale) for construction. The primary scientific research objective of these

one-of-a-kind large-scale, system type experiments is in the validation and calibration of analytical simulation tools

to capture SFSI and/or systems response, which cannot be readily achieved from testing at smaller scale, or under

quasi-static or pseudo-dynamic test conditions. Tests on this facility are ideal to establish benchmark performance

for class A predictions, proof-of-concept data for clients such as Caltrans, FEMA, or DOE, as well as a conceptdevelopment platform for researchers and industry, both nationally and worldwide.

The shake table, acting in combination with equipment and facilities separately funded by the California

Department of Transportation (Caltrans), which include a large laminar soil shear box and a refillable soil pit, results

in a one-of-a-kind worldwide seismic testing facility. The LHPOST has been developed at Camp Elliott, a field

laboratory site located 15km away from the main UCSD campus, in concurrence with the development of the

Caltrans SFSI facility at the same site. UCSD is convinced that this innovative piece of NSF equipment in

conjunction with the field laboratory site adds unique testing capabilities to NEES and consolidates the leadership of

the NEES collaboratory as the predominant earthquake testing consortium in the world.

The LHPOST is a 7.6m wide by 12.2m long single degree of freedom (DOF) system with the capability of

upgrading to 6-DOF. The specifications for the first phase of the facility are a stroke of 0.75m, a peak horizontal

velocity of 1.8 m/s, a horizontal force capacity of 6.8MN, an overturning moment capacity of 50MN-m for a 400 ton

specimen, and a vertical payload capacity of 20MN. The testing frequency range is 0-20 Hz. Although this table isnot the largest of its kind in terms of size in the world, the velocity, frequency range, and stroke capabilities make it

the largest table outside Japan. The facility adds a significant new dimension and capabilities to existing United

States testing facilities.

The equipment will be operational by October 2004 and will be managed as a national shared-use NEES

equipment site, with tele-observation and limited tele-operation capabilities. This unique facility will enable next

generation seismic experiments to be conducted on very large structural and SFSI systems such as full-scale

buildings, single and multiple column bridge bents in a laminar soil box, utility/lifeline structures such as electrical

sub-stations, nuclear containment casks, and seismic isolation systems. Moreover, the proximity of a soil pit to the

LHPOST will allow hybrid shake table-soil pit experiments to be conducted. The LHPOST has been designed with

performance characteristics that will allow for the accurate reproduction of near source ground motions for the

seismic testing of very large or full-scale structural and SFSI systems.

The hardware requirements for the development of this LHPOST consist of servo controlled dynamic actuatorswith large servo-valves, a large power supply, a real-time multi-variable controller, a vertical load/overturning

moment bearing system, and a platen. The power supply and accumulator blow-down system, the large laminar soil

box and a soil pit are provided by UCSD to the NEES Field Test Laboratory at Camp Elliott as matching funds

through other research programs and funding sources.

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NEES EQUIPMENT DESCRIPTION

The facilities at Camp Elliott will be used to conduct large- and full-scale testing to investigate structural and

geotechnical performance issues related to the area of Critical Infrastructure Protection (CIP) that cannot readily be

extrapolated from testing at smaller scale, or under quasi-static or pseudo-dynamic conditions. Potential research

that could be carried out include (a) the effects of passive and semi-active energy dissipating systems on building

response, (b) large-scale testing of kinematic soil-foundation-structure interaction, (c) seismic response of nuclearwaste dry storage casks, including the soil-structure interaction and the kinematic interaction between casks, (d) loss

estimation of buildings, including the interaction between their components, (e) seismic response of full-scale wood-

frame construction including school buildings (f) response of building diaphragms, where the presence of a

distributed mass constrains the testing to be performed solely under dynamic conditions, (g) assessment of

liquefaction mitigation mechanisms, (g) optimization of shallow foundations to maximize kinematic soil-foundation

interaction, h) the study of the complex interaction between interconnected components of electrical substations,

such as high-voltage transformer-bushing systems, and i) response of structural members to blast loading. Such

experiments present unique opportunities to develop, calibrate, and validate computational tools.

DESCRIPTION OFPHYSICAL FACILITY

The UCSD LHPOST was developed at the Field Station at Camp Elliott, a site located 15km away from the

main UCSD campus (see Figure 1). The shake table, acting in combination with a Soil-Foundation-Structure

Interaction (SFSI) facility, funded by the California Department of Transportation (Caltrans) and an Explosive

Loading Laboratory (ELL), funded by the Technical Support Working Group (TSWG), will result in one-of-a-kind

worldwide real-time testing of structural components, assemblies, and systems such as nuclear casks, building

structures, bridge abutments, and embankments and foundations that will be subjected to real-time earthquake or

blast loading. The Field Station at Camp Elliott has ample room for the construction and instrumentation of multiple

test specimens simultaneously before placement on the shake table.

Figure 1: Field Station at Camp Elliott

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Camp Elliott is situated on the corner of Miramar/Pomerado Rd. and Interstate 15. It is on University property

that currently houses an animal facility for the UCSD School of Medicine and a storage facility for Scripps Institute

of Oceanography. Camp Elliott has restricted access and is a gated facility. The Structural Engineering field station

is currently located on a 2-acre site on the Northwest corner of the University property. Hotel and dining services are

within 1 mile of the site, which is discussed further in the shared use plan section.

Geotechnical Investigations

A consultant hired by UCSD (Geocon Incorporated) completed a geotechnical investigation of the NEES testing

facility at Camp Elliott Error! Reference source not found.. The primary purpose of the study was to observe and

sample the prevailing soil and geologic conditions at the site, compile pertinent information from previous

geotechnical investigations performed in the nearby area and, based on this information, provide recommendations

for the facility and associated improvements. The field investigation was performed on February 13-15, 2002 and

consisted of the excavation of four exploratory borings. Two were excavated to a depth of 18.2 m and 21.3 m and

two others to a depth of 1.5 m to 3.7 m. The stratigraphy consisted of Linda Vista Formation (firm lean clay to

dense clayey sand with cobbles) from zero depth to approximately 3.4 m that had a shear wave velocity of 300 m/s.

The second layer of soil from a depth of approximately 3.4 m to the bottom of the boring (21.3 m) was Stadium

Conglomerate (very dense silty sand with gravel, cobbles and boulders, occasionally cemented), which had a shear

wave velocity of 700 m/s. More detailed information about the results from this geotechnical study can be found inError! Reference source not found..

Forced vibration tests were conducted at the Field Station at Camp Elliott using a 20kN eccentric shaker under a

frequency range of 4-20 hertz. The objective of the tests was to investigate the attenuation of the soil up to 250m

from the vibration source in several directions. Accelerometers were placed at increasing distances from the

concrete block holding the shaker. The first accelerometer was 1.8m and the remaining accelerometers were spaced

approximately 60m from each other for a total distance of 233m. Results of the tests were used to determine the final

location of the soil pit and shake table to minimize the effect of wave propagations at the site. The results from the

forced vibration tests also showed that the soil was stiff and is characterized by very good attenuation. At 60m from

the vibration source, the acceleration was attenuated by a factor of 20. Therefore, little energy is expected to be

transmitted from the shake table to the soil pit and consequently isolation of the reaction mass was unnecessary.

Furthermore, several professors at UCSD (Joel Conte and Enrique Luco) conducted forced vibration tests at

Camp Elliott using the large shakers from the UCLA-NEES equipment site. The results will be used in thedevelopment of a future simulation tool that models the soil at the site, the reaction mass, the platen, the hydraulic

system, and the specimen. The goal will be to develop a tool that can simulate the overall response of a test

conducted on the LHPOST. A preliminary simplified linear elastic version of the tool will be made available to

researchers by October 2004 to assist in the evaluation of proposed test specimen on the LHPOST. This is discussed

further in the shared use plan section.

DESCRIPTION OFLHPOST COMPONENTS

Figure 2provides a schematic rendering showing the key components of the LHPOST facility. The design was

been a joint effort between the faculty and staff in the Department of Structural Engineering at UCSD and a group

from MTS Systems in Minneapolis. Component 1 in Figure 2 shows the steel platen, which was designed,

manufactured, and installed as a turnkey platen system by MTS Systems. The UCSD-NEES project team was

responsible for designing the reaction mass (component 2), which consists of an underground tunnel from the power

supply in the butler building to the stressing tunnels. The underground tunnel facilitates the placement of thehydraulic piping and provides reasonable access from the pump house to the major components of the shake table in

the pit. Holes for vertical tie-downs are also provided around the test pit. This reaction mass design minimizes the

amount of concrete by relying on the strong soil available at the site.

MTS Systems was primarily responsible for the design of the hydraulic and mechanical systems for the

LHPOST such as the horizontal actuators (component 3), vertical bearings (component 4), vertical tension struts for

the overturning moment restraint system (component 5, which was manufactured by Calbrandt Inc./Granite Fluid

Power), and the components required for yaw restraint to prevent the platen from undesirable out-of-plane motions

in the uniaxial configuration (component 6). MTS Systems was also responsible for the design of the hydraulic

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power supply, which is being housed in the butler building and consists of two pumps, a blow-down system,

accumulator banks, and surge tank (the latter two items manufactured by Calbrandt Inc./Granite Fluid Power). The

performance specifications for all of these components are described in detail in subsequent sections.

Figure 2: Schematic Rendering of LHPOST Showing Key Components

INFRASTRUCTUREDEVELOPED AT CAMPELLIOTT

UCSD has developed the infrastructure and provided utilities to the Camp Elliott site, as well as coordinated the

construction and installation of a sustained power supply blow down system (9,500 liter volume that can deliver 7.5

m of swept table displacement (2500 liters) at 21MPa) with 720 liter/min direct pumping capacity to operate the

LHPOST system. Since Camp Elliott is a brand new facility, all utilities have been brought in per code with room

for expansion and future upgrades. Specifically, the electrical power service size is 1000kVA. With respect to

telecommunication capabilities, 45Mbps networking capabilities are already available via the High Performance

Wireless Research and Education Network (HPWREN). The 1Gbps NEES requirement will be achieved using

GigaMAN, a fiber-based service that provides 1.25 Gbps seamless connectivity between the UCSD local area

network (and more specifically the San Diego Supercomputer Center (SDSC)) and the Camp Elliott site.

LHPOST SPECIFICATIONS

The design criteria and main specifications of the shake table system were dictated by consideration of a number

of target research application examples consisting of large or full-scale shake table experiments. Design criteria and

expected performance parameters of the shake table are summarized inTable 1. Performance parameters consist of

specifications for actuator stroke, velocity and force capacities, and frequency bandwidth of the earthquake

simulator.

In deciding on these parameters, far source (or ordinary) and near source earthquake ground motions to be

reproduced by the shake table were considered. Near source, fault normal ground motion records with forward

directivity effects (Doppler effects) are characterized by a large velocity pulse, while near source fault parallel

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ground motion records are characterized by a fling step (i.e., large step function in the ground displacement record).

Since for many sites, the seismic hazard of the built environment is controlled by near source ground motions at

long return period hazard (e.g., 2% probability of exceedence in 50 years), it was essential that the LHPOST be able

to accurately reproduce near-fault ground motion effects. For ordinary ground motions, a maximum horizontal

peak ground and peak table acceleration of 1g is required, corresponding to an upper bound to the vast majority of

recorded ground motion records. Consideration of a suite of desired large or full-scale specimens for shake table

experiments, together with the mass of the platen (assumed as 2.25 MN) and accounting for elastic and inelastic

dynamic amplification effects (for the base shear), the effective height of the specimen, as well as dynamic

similitude requirements, led to a maximum force of 6.8 MN to be imparted by the shake table actuators and a

maximum overturning moment of 50 MN-m to be accommodated by the platen and its support mechanism. The

reproduction capability of near source ground motions by the shake table is controlled by the peak table velocity

parameter. A peak table velocity of 1.8 m/s was selected by considering a set of representative (unscaled) near

source records, which are used extensively in numerical earthquake engineering research Error! Reference source

not found..It must also be recognized that 1.8 m/sec would be the peak table velocity. When the laminar shear box

is used, additional amplification would take place within the soil box and the peak velocity on the soil surface could

exceed 1.8 m/sec.

Table 1: NEES LHPOST Specifications

Size 7.6 m 12.2 m

Peak velocity 1.8 m/sStroke 0.75 m

Maximum gravity (vertical) payload 20 MN

Force capacity of actuators 6.8 MN

Maximum overturning moment (bare table, 400 ton specimen) 35 MN-m, 50 MN-m

Frequency bandwidth 0 - 20 Hz

The peak displacement or stroke specification for the shake table of 0.75 m represents a compromise between

the expected peak ground displacement for ordinary ground motions having a peak ground acceleration of 1g, and

the expected degradation of shake table performance with increasing actuator stroke. The significant frequency

content of actual earthquake horizontal ground acceleration records lies in the range between 0 and 15 Hz, while the

significant frequency components of horizontal ground velocity and ground displacement records lie in an

increasingly lower frequency range than that of the ground acceleration. A frequency bandwidth of 20 Hz for

accurate reproduction of actual ground acceleration records by the table was designed for, thus allowing for a time

compression of up to 33% for test specimens scaled down to 56% (assuming same material and same acceleration

similitude).

Specifications for the various components of the LHPOST in its uniaxial configuration are summarized in Table

2. These components include the horizontal actuators, the vertical bearings, hold-down struts, and the hydraulic

power supply.

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Table 2: Uniaxial LHPOST Component Specifications

Description Metric Units English Units

Table Table Foot Print 7.6 m x 12.2 m 25 ft x 40 ft

Table Weight 2.25 MN 253 ton

Specimen Payload 20 MN 2248 ton

Specimen CG 10 m 32.8 ft

Maximum Overturning Moment 50 MN-m 18440 ton-ft

Actuator Quantity 2

Stroke 0.75 m 29.53 in

Peak Velocity 1.8 m/s 5.9 ft/s

Acceleration 1 g 1 g

Force Capacity Tension/Compression 2.7 MN / 4.2 MN 301.7 ton / 471.3 ton

Rod Diameter 0.3048 m 12 in

Piston Diameter 0.508 m 20 in

Total Effective Piston Area 0.332 m^2 515.3 in^2

Tension Area 0.1297 m^2 201.1 in^2

Compression Area 0.2027 m^2 314.2 in^2

Hold-Down Strut Quantity 2

Nitrogen Pressure 20.7 Mpa 3000 psi

Stroke 2 m 78.7 in

Hold-down Force Capacity 3.1 MN 348 ton

Effective Area 0.152 m^2 235 in^2

Vertical Bearing Quantity 6

Effective Bearing Area 0.455 m^2 706 in^2

Vertical Force Capacity 9.4 MN 1060 ton

Stroke 0.013 m 0.5 in

Hyd Supply Accumulator Swept Volume 7.5 m 295.3 in

Accumulator Bank Pressure 35 MPa 5000 psi

System Pressure 20.7 MPa 3000 psi

Blowdown Flow Rate 38000 lpm 10000 gpm

HPU Flow Rate @ 5000 psi 431 lpm 114 gpm

HPU Flow Rate @ 3000 psi 718 lpm 190 gpm

Surge Tank Capacity 10000 liters 2642 gal