Would someone please set me straight? I am getting very confused by couple terms that are being used here and elsewhere.

1. What is a princepost?

Neither the TFGuild Glossary nor Websters has a definition for a "princepost" yet it is referred to in "Kingpost Truss Engineering, An Addendum by Ed Levin. September 2004, Timber Framing No. 73." In his assessment of the truss found at Castleton

2. What is a Queenpost?

I was of the understanding according to the TFGuild Glossary that a Queenpost design utilized only two posts which are joined in the center with an anchorbeam. It does not indicate the presence of a Kingpost or that it can be merely a supplement to a kingpost truss. However, Steve Chappell's "A Timberframer's Workshop" 1998 ed. clearly shows on page 109 a king post truss and "Queen posts can be added to the lower third point of the rafters to the tie beam for additional stiffness on longer spans."
How do these differ from princeposts?
Is it a difference in function? (ie. tension rather than compression)
Is it the absence or presence of an additional strut?

3. Do queenposts act in tension or compression?

4. Am I being too picky about definitions and is it acceptable to use these terms interchangeably?

I have seen websites commponly refer to what is clearly a kingpost truss with stuts as a queenpost truss.

I'll help with prince post. It's usually added to a king post truss to provide extra support for the bottom chord (tie beam). It's a vertical member, in tension, hung from the connection between the top of the strut and the rafter. The other end connects to the bottom chord.

The main classroom buildings at North House Folk School, in Grand Marais, MN, use these trusses. They were built in the 30's as part of the WPA, I beleive, as USFS buildings. Sorry for the lousy photo, but it's all I could find on short notice:

Notice taht both the kings and princes are steel rods in this example - clearly that would only work if they were tension members.

I think the main reason they used them in this building was to use the attic for storage. The added weight on the tie beams that hold up the bottom chord required additional support.

I've seen the term queen post applied pretty loosely in a lot of different situations. I do so myself

I call this a queen post bent:

But it's clearly not a truss at all.

Did that help, or just make things worse? CB.

I'm thinking this is a queenpost truss, though the queens are not vertical... from the Carpenter's Fellowship gallery:

My feeling on this subject and I have no basis to base this on is that when a king post is present they are called prince posts, and when no king post is present they are called queen posts....

I've just reviewed the glossary of term in Cecil A. Hewett's "English Historic Carpentry" and he doesn't list prince post in the list of posts depicted in the book.

I've just reviewed the book "Timber Buildings in Britain" by R.W. Brunskill and he lists a princess post as a post between the queen post and the eave of a queen post truss....

Maybe it is this reasoning that makes me think a king post has a prince post as a queen post has a princess post.....

The posts that Mark shows could be called "canted" queen posts...

I Belive the members in Marks post are "canted" struts as they are perpendicular to the rafters.

Is that a truss?

without looking up definitions, I think of a truss as a frame that spans wall to wall and does not add roof thrust to the wall, only weight... so generally a truss has a continuous bottom chord.

I think of a truss as a frame that transmits loads axially among its members. The queenposts in theis truss simply transfer compression loads to the bottom chord and put it into bending. I might be wrong but I would call that a braced rafter.

Take away the queenposts and I'd have a tough time with my definition though, is it a tied rafter or a truss?

I like Diaku's insight as to the compression/tension function of the member. It makes sense to me that a Princepost paired with a Kingpost is acting in tension, supporting the tiebeam from the rafter rather than in compression supporting rafter from the tiebeam. In this way it is a sort of "Mini-Kingpost" when paired with struts.

The Queenpost still is vague as to definition although the definition for Princesses post would place it in compression mode. This would make logical sense and clearly define queen post from kingpost on a functionality basis.

I guess it also makes a difference whether it is a true "truss" configuration vs. merely a bent. Unless I am mistaken bending is not allowed by truss definition, all member must be in either compression or tension. We know this is only theoretical as "sag" can be seen an many historical truss examples. So both Mark and Don P. are right? Over time the compression load of a queenpost truss could cause bending in the lower chord (tiebeam) if severe enough this would result in thrust at the wall plates?

Quuenpost = compression
Kingpost = tension

Queenpost weight is born primarily by bottom chord (tie-beam)
Kingpost weight is born primarily by top chords (rafters)

prince and princess replicate parent of same sex? Is this good logic?

I think we better delete this thread before anyone finds out we don't have a clue what we are doing LOL

ha ha ha ha ha..... thump
(me laughing my head off)

Timber Framing Journal #71 (March 2004) has an article dedicated to historic queen post trusses. Here's a drawing from that article:



And the introductory paragraph:

Now thats an idea. I think I made up one a while back we really like to use.

I say I think I did just in case I didn't...."Man I love getting old"...

Anyway. We call the point at which the vertical wall becomes a diagonal roof pitch the "control point". We like it. nice friendly little name but everyone in the shop knows what it means.

If we accidentally hijacked this thread just delete us LOL
Sounds great in general conversation too.

And its a lot short than "the spot where the vertical wall becomes a roof pitch diagonal line. LOL

If I hijacked this thread just delete me. I won't remember next week anyway.

Where would you stop calling them princeposts, or would you?



Thanks for the post and photo Clark.

http://www.ruhr-uni-bochum.de/bauko/downloads/bauko_geneigte%20daecher.pdf

Check out the drawing on page twelve. Would that not be considered a type of queen post construction? If yes, then those queens are clearly under tension. So to simply say king equals tension and queen equals compression would not be correct.
I am not sure why it matters so much what the posts are called anyway. As long as the structure can support itself....

That is a critical point. In our shop, we call that the 'eave line'. Probably not technically correct either. Anyone else? CB.

"That corner, no, there."

That looks like good reading too EH. Anyone know if theres a way to get my computer to translate a pdf?

The straining beam is the key to whether the queenposts are in tension or compression. I've just seen both, in the same book, called a queenpost truss. It seems to me the main thing is whether the queen is holding her skirts up or sitting on her bottom. Is the bottom chord sized for bending without the straining beam or just a tension element with it.

I tend to point and call all the internal parts "webs". I've seen "rods & braces" used, that seemed pretty good, describing tension or compression.

If you can high lite and copy the text, I can give you a site where you can paste it in and get somewhat of a translation....

I could have sworn I made two post a while back in this thread listing two books I reviewed for definitions of prince post and princess post....
They seem to be missing....
Did anyone else see them or am I just dreaming.?...again....

DanG, I knew there was going to be a test.

4th post, page 1;
I've just reviewed the glossary of term in Cecil A. Hewett's "English Historic Carpentry" and he doesn't list prince post in the list of posts depicted in the book.

I've just reviewed the book "Timber Buildings in Britain" by R.W. Brunskill and he lists a princess post as a post between the queen post and the eave of a queen post truss....

The whole queenpost truss article is available here.
CB.

Thanks Don, somehow I just couldn't see that....
I must have been having a senior moment......
Thanks for that link to the article, Clark...

Has anyone got "engineering" approval for the kind of spans depicted in here
http://www.tfguild.org/publications/queenposttrussTF71.pdf

50 - 60 ft clear span...some over 200 yrs old and still standing.

There are a lot of "approved" engineered structures that are NOT still standing.....not to mention the thousands of old barns around the country that have long survived the stick built house on the same property.

I wonder how long exactly a building structure/system has to stand before it can be considered "SAFE" or "acceptable".....

Went back and read the whole Queenpost truss article. It is definitely incorrect logic to say queenpost= compression. According to article it would be more accurate to say Queenpost = Straining beam present. This, however, means that several prominent members of the TF community have publications which may contain glaring errors regarding kingpost or queenpost trusses.

I have difficulty with the "doesn't really matter what it's called as long as it works idea"

Isn't education the whole goal of the Guild?

Don't feel special Jim, I can't count the times she's reached around me to hand me the tool I'm looking for.

This is from the queenpost article;

"But trusses are not about bending. By definition, a truss is a framework that bears its burden via axial loading, in pure tension and compression. In this capacity, timber (and indeed all framing material) is many times stiffer than it is in bending. As a beam bridge, a 12-ft. 6x6 carries a midspan point load of 1000 lbs. with a half-inch of deflection. Stand the same stick up on end, load its top with half a ton and the newborn column will shorten a few thousands of an inch. Loaded axially the timber is a hundred times—two orders of magnitude stiffer than it is bending.
Conversely, consider the effect of an undersized truss member:
in bending (beam action) it can cause a local distortion of the
frame but, in buckling under axial load, it stands fair to bring
down the whole structure. As specified by the National Design
Specification for Wood Construction (NDS), the controlling design
value used to size a column or other timber loaded in compression
is compression parallel to grain (Fc) as modified by the column stability factor (Cp). Fc specifies maximum allowable axial compression stress by species and grade. To avoid the tendency of long thin members to buckle in compression, Cp lowers the working value of Fc via a complex calculation involving stiffness, slenderness ratio (effective length divided by least cross-section dimension), end conditions and other terms (Sect. 3.7.1, p. 22). Additional equations come into play if the timber in question in loaded in bending as well as compression."

That last sentence gets into section 15, if anyone can help me over a hump there I'd sure appreciate it.

Where my concern came from is the "Queenpost" earlier put the bottom chord in bending. A princepost wandering around on the bottom chord can put a kingpost truss bottom chord in bending. When an axially loaded member is handed too much bending, bad things can happen.

so does this mean not to put a curved piece in a truss? say an bowed down collar tie? because then it would flex and deflect for sure. very complicated equations. like as complicated as guessing.

Well, a wink is as good as a nod to a blind horse.

Do you plan on guessing at the member sizes in a 50 or 60 foot truss, do you really think "they" did? You may feel comfortable guessing, I sure don't.

I've seen a fair number of guesses and rarely seen people guess right, like I can remember one. I was seeing people use logic like, "I've seen a 2x12 span this far, so 2 2x's should span twice as far", guessing falls apart to the square of span. I put a beam calc up after I saw someone guess that a 6x8 would make a span that needed a 8x14.

Complicated enough that an engineer should review your design. I just like to understand what I'm doing. I consider that part of the craftsmanship equation. At the moment when a point load is delivered to the side of an axially loaded member, I'm the blind horse. I'm working on it. The curve, I've seen the math in the glulam guide... that might be next week

Just a doodle flipping the queen.


I think there is some wrong thinking here, engineering simply tries to figure out why the old stuff hasn't collapsed, quantify and understand that and use it when designing new. If your gut is that good, guess, some are, I aren't.

Uncomplicated? I'd try it like a simple beam.

goes from failure, poor, good, very good and excellent.

Some stuff from reading;

While it is recommended that all loads supported by a tension chord be located at a panel point, this may not always be possible,and bending moments may be introduced into the bottom chords. Such additional loads must be accounted for by designing and sizing the bottom chords as combined bending and axial tension members.

The compression chord usually carries most of the external loads, most often applied as uniformly distributed loads along the panel length. When the chord is continuous over several panels, it should first be evaluated as a continuous beam with the panel points assumed to be nonyielding supports. The reactions thus determined become the panel point loads used in the axial force analysis of the truss. The bending moments induced by the uniform loading are included in the combined stress analysis.

The combined axial and bending stresses at the center of the compression chord must also be evaluated. Consider first an initially straight laterally restrained chord, continuous over several panel points, with uniform transverse load and some axial force. Obviously the panels are in reality a series of interconnected beam columns supported at panel points and free to deflect in the plane of the truss.

At first glance the effective column length appears to be the distance between the points of contraflexure (the inflection points as the rafter curves over each strut then deflects down in span under the load). However, it can be shown that the effective length increases with increasing load, and of course, the stresses are nonlinear with load. The designer wishing to persue this complicated analysis can refer to section 15.4 of the NDS.

Normally, in sawn timber the complexities of the preceeding are avoided by assuming a conservative effective length. (it goes on, but the easy way is to multiply the point to point length x 1.5 to get the safe effective length, happy to see that).