GeoStructures: UCLA / Caltrans

Case study: SOFO System

Full-size Pile Monitoring
Seismic Evaluation
Soil-pile Interaction

Project Description

Summary: Full-scale, large diameter cast-in-drilled-hole (CIDH) shafts / columns under large displacement cyclic lateral loading

Clients: UCLA

Place: Los Angeles, California (USA)

Period: 1999 - N/A

Installation: UCLA

Structure's short description: The CIDH shaft-column was designed according to standard Caltrans? Bridge Design Specifications (1995) using the Seismic Design Criteria (1999). The test specimen was comprised of a 1.8 m (6 ft) diameter column extending 12.2 m (40 ft) and a 2 m (6.5 ft) diameter shaft extending 14.6 m (48 ft) below ground line, as shown in Fig. 3. Steel reinforcement was comprised of 36-#14 longitudinal bars with average yield and ultimate tensile strengths of 490MPa (71 ksi) and 703 MPa (102 ksi), respectively; and shop-welded #8 hoops at 152 mm (6 inch) spacing with average yield and ultimate tensile strength of 496 MPa (72 ksi) and 738 MPa (107 ksi), respectively. The longitudinal and transverse steel ratios are roughly 2 per cent and 0.7 per cent, respectively. Normal-weight ready-mix concrete was used in the specimen, with an average tested cylinder compressive strength of 42 MPa (6.1 ksi).

Aim of monitoring: The test shaft was extensively instrumented to enable high-precision section curvature measurements in addition to measurements of contact pressure at the soil-shaft interface around the shaft perimeter. Among the principal objectives of the testing was to characterize the soil-shaft interaction across a wide displacement range in order to gain insight into the adequacy of existing design guidelines (which are based principally on the testing of small diameter piles) for the large diameter shafts commonly used to support highway bridges. The component stresses of resistance and the effects of nonlinear soil resistance to relative displacements between the soil and shaft were investigated

Number of sensor: 32

Main Results: The observed behavior suggests that large diameter shafts could have added capacity from side friction, which the current design models do no incorporate.

Sensor Installation

Pile Failure

Bibliography:

Growing Market Acceptance for Fiber-Optic Solutions in Civil Structures , T. Graver, D. Inaudi, J. Doornink, Optics East Philadelphia, USA, October 27, 2004

Combined Static and dynamic monitoring of civil structures with long-gauge fiber optic sensors , D. Inaudi, D. Posenato, B. Glisic, J. Miller, T. Graver, 23rd International Modal Analysis Conference (IMAC XXIII), Orlando, Florida, USA, 31 January-3 February, 2005

Growing Market Acceptance for Fiber-Optic Solutions in Civil Structures , Th. Graver, D. Inaudi, Optics East Conference,Boston, USA, October 23-26, 2005

Interface stresses between soil and large diameter drilled shaft under lateral loading , K. Janoyan, M. Whelan, ASCE Geotechnical Special Publication No. 124, ?Drilled Shafts, Micropiling, Deep Mixing, Remedial Methods, and Specialty Foundation Systems?, 2004