Grading Outcomes of Chinese Fir Laminas Under JAS 1152 and EN 338: Effects of Specimen Size Condition and Grade Alignment

Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) has considerable potential for structural use in China, but wider application is constrained by the lack of standard-linked grading approaches. This study examined the effects of specimen size condition and the two standards, JAS 1152 and EN 338, on the grading outcomes of Chinese fir laminas. Two specimen types were considered: multi-size and single-size specimens were graded under JAS 1152, and the latter were further graded under EN 338. Under JAS 1152, the single-size specimens could be classified into seven grades from L50 to L110, with 30.4% assigned to L80 and above, showing a clearly higher-grade yield than the previously studied multi-size specimens. For the same single-size specimens, JAS 1152 was governed by bending modulus of elasticity (MOE), whereas EN 338 was controlled mainly by density, yielding markedly different grade distributions. The stronger density constraint in EN 338 led to a high Reject ratio (35.3%), whereas no Reject occurred under JAS 1152, suggesting that JAS 1152 may be more favorable for the efficient and fuller utilization of Chinese fir laminas. The two systems remained statistically linked at the bending-MOE level, despite the absence of strict one-to-one correspondence. Specifically, in the JAS 1152-to-EN 338 direction, grades from L50 to L110 corresponded progressively to grades from Reject to C30, whereas in the reverse direction, grades from C14 to C16, from C18 to C22, and from C24 to C30 corresponded to L60, L70, and L80, respectively. These results provide a basis for refined grading of Chinese fir laminas and for cross-standard interpretation of their structural utilization.