Abstract
In structural timber tests, unintended failure mechanisms occur frequently in specimens and their results are called censored data. There are two censored data analysis: censored maximum likelihood estimation (CMLE) and Kaplan–Meier (KM) method. In this study, the precision of the censored data analysis was investigated to determine the characteristic value, 5th percentile value, of the structural timber. The results show that (1) the 5th percentile value was underestimated by ordinary data analysis methods; maximum likelihood estimation (MLE) and Order statistics. (2) CMLE with 30% lower tail censored data and KM method provided much more precise 5th percentile value. (3) The amount of under-measurement (5 MPa, 10 MPa, and 15 MPa in this simulation study) did not show significant effect on the 5th percentile determination in CMLE and KM method, but the proportion of censored data (percentage of unintended failure specimen; 10%, 20%, 30%, and 40%) affected the determination of 5th percentile value. (4) CMLE with 30% lower tail censored data and KM method showed good agreement in case that the data included unintended failure data up to 20%.
Highlights
During full-scale timber tests, we expect a failure mode intended
(2) censored maximum likelihood estimation (CMLE) with 30% lower tail censored data and Kaplan– Meier (KM) method provided much more precise 5th percentile value
Censored maximum likelihood estimation (CMLE): (1) with all censored data (2) with 30% lower tail censored data
Summary
During full-scale timber tests, we expect a failure mode intended. In tension tests of structural timber, grip failures (unintended failure) happened [1]. The tension grip can damage the timber during the test. The tension grip damage can lead to grip failure. In the case of a specimen that has knots around the grip, a failure in tension test often occurred around the grip. In this case, the measured strength may be lower than the actual strength which we need to get. The specimens of grip failure may lead to underestimation of the 5th percentile
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