The only limitations other than the limitations arising from conformity to AS 1720.1 (adequate capacity of bolted joint relative to expected loads etc) are environmental factors such as in-service moisture content. Where moisture content remains below 15% no modification factors apply. Where higher moisture contents are likely for prolonged periods AS 1720.1 provides modification factors, and preservative treatment may be warranted. On-line guides such as that published by Carter Holt Harvey for their HySpan product may be helpful.

Your table is a very interesting design but it's a little beyond the scope of our service to calculate the strength of the x-shaped legs. Our role is to provide data about timber properties for designers to use, rather than to do the design work itself. We feel you will need advice from a structural design consultant familiar with timber. We would be happy to provide information on the strength properties of Victorian ash to assist anyone you might engage to prepare a design.

We note that the domain for your email address is Brazil. That's not a problem, we field inquiries from all over but we are not familiar with Brazilian building practice. Even if you are based in Australia, your question is somewhat beyond the scope of our service. You need engineering advice that will take into account the type and structural grade of the timber you wish to recycle, and design your trusses accordingly.

If your spruce is seasoned spruce from Sweden (aka 'white Baltic') it can be visually stress-graded to Australian Standard 2858, Timber - Softwood - Visually stress-graded for structural purposes. Achievable grades for seasoned spruce (moisture content 15% or less) are F5, F7, F8 and F11, depending on quality, particularly with respect to knot sizes and slope of grain. AS 2858 gives limiting knot sizes for each grade and maximum allowable slope of grain.

It's very difficult to identify a wood species from a photo, particularly if it's a tropical species - there are many of them, with similar colours and grain patterns. If it's important to know the species a specialist in that area could probably identify it by examining the cell structure of a sample microscopically. This would involve cutting a small piece from a place where it won't be noticed.