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STATNAMIC ACCURACY, RELIABILITY AND RECOGNITION

Statnamic load testing has been used extensively all over the world on bridges, high rise condominium structures, office towers, military facilities, Corps of Engineers flood control structures, water and wastewater facilities and various other commercial structures. Statnamic Load Testing is a recognized test method by the American Society for Testing and Materials designation number ASTM D7383-08 and is routinely used as an alternate to ASTM D1143 and ASTM D 1194.

Innovations in Statnamic analysis have paved the way for new, more accurate, methods of evaluating axial Statnamic load test results. A modification of the UPM, the Segmental Unloading Point Method (SUP) allows acceleration distribution throughout the foundation to be better quantified, therefore, refining the ability to determine the static response of the foundation. As a result, determining the capacity of foundations previously considered troublesome or insolvable using the standard method is now routinely evaluated. The powerful SUP method has sound theoretical background and proven correlation with static load tests. The SUP method used in conjunction with rate of loading factors documented in several independent University studies show that Statnamic load testing has great statistical reliability when compared with conventional static load test results. Please contact AFT for information on these studies.

The NCHRP and FDOT/University of Florida research focuses on the comprehensive study of data collected from 34 deep foundations load test sites where both Static (SLT) and Statnamic (STN) testing was conducted. The main bearing soil strata of each pile was divided broadly into four subgroups: rock, sand, silt, and clay. As the nature of Statnamic testing induces loading rate

effects, the affect in various soil introduced to unify the reliability

types was therein considered. A and statistical probability of failure

rate effect

factor was

as outlined

by FHWA

(1998) for Load and Resistance Factor Design. Based on standard deviation of the data set, a resistance factor was tested foundations. The results of this study are summarized

the ratio of SLT to STN and the determined for Statnamically load in Table 1 below. Included in this

table are the bias soil subgroup, as

factors

(λ),

well as

the

standard deviations, and entire study (All Soils).

calculated resistance factors (φ) for each This summary shows a good correlation

between the to 1.0 and a

STN and SLT capacities for Rock and Sand standard deviation less than 9%. The results

indicated by a bias factor nearly equal also show a relatively good correlation

between standard capacity standard

the STN and SLT capacities for Silt and deviations less than 12%. The combined analysis method performs very well with deviation of less than 10%.

Clay with bias factors larger than 1.0 and values of all soil types show that the STN a bias factor slightly larger than 1.0 and a

Table 1 Results Summary

Rock

Sand

Silt

Clay

All Soils

Bias Factor, λ

0.999

0.994

1.041

1.035

1.017

Standard Deviation

0.068

0.083

0.116

0.119

0.097

Resistance Factor, φ

0.739

0.726

0.737

0.730

0.734

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