Reinforced Concrete

Final Exam and Project Schedule

2011-12-09T17:34:00.000-08:00

...

WSU ARCH 463/563 ...

... your final exam will be emailed shortly (next hour or so). It is `required', and `take-home' format. It is due by 5 pm Thursday, 12/15 to my Faculty Mailbox on 5th Floor Carpenter Hall.

The Graduate Projects (Deck Construction Documents) are also due at that time.

I STRONGLY recommend you keep personal copies of both.

UI ARCH 462 ...

Concrete Beam Test Reports are due 5 pm, Tuesday, 12/13, to my Faculty Mailbox in the Architecture Faculty Office/Mailroom (Sandi's office).

BOTH CLASSES: I will be somewhat available by appointment in Moscow during the week if you have any last minute questions, struggles, etc.

Example Experimental Beam Calcs - PREDICTED PERFORMANCE

2011-11-22T19:15:00.000-08:00

...

Yeah, a couple are blurred. Get over it.

Pretty Retaining Wall ...

2011-11-17T22:23:00.000-08:00

Gosh this is a pretty wall ...

... looks like it has some batter. Gravel backfill, probably reinforced backfill zone. Gravel provides some surface stability, a `path' if needed, to above, and is a better backfill material overall (less lateral pressure, better drainage).

The blocks also accommodate the changing longitudinal grade. The pavement at toe helps keep the wall from sliding.

Sweet.

Assn 3 Problem 1 Page 1 ... FIXED

2011-11-10T00:16:00.000-08:00

... so, yeah, I started with the wrong `d' ... but all it gave me was a wrong rho, and slightly wrong [ ]. Note that I took the easy way out and still calculated strength even though the reinforcement ratio was less than min. But the first guess was to see how we were coming in strength-wise anyway.

Assignment 3 prob 2 (WSU 463/563)

2011-11-07T15:16:00.000-08:00

... here is the solution to # 2 of assignment 3.

Note that the 18 in. max spacing governs over the 0.0033 min. reinf ratio, and the 0.0033 ratio governs over strength.

... hmmmm ... we could have just started with # 5 at 18 in. o.c. and found that it was both strong enuf and met the min. rho.

UPDATE: WHOA! ... we need to check c) ...

From Table 9.5(a) ... the min. depth of the member needs to be L/20 ...

So, L/20 = 10 x 12 in. / 20 = 6 in.

Since our slab is 6 in. thick. ... YAY! ... we are deemed good without having to do detailed deflection calcs.

Doc

Assn 3 Prob 1 (WSU 463 / 563) - FIXED???!!!

2011-11-07T14:54:00.000-08:00

... here!

SOME STUFF DELETED, SOME REPEATED (FROM THE DELETED!

LOAD …

sigma top = 0 x 100 = 0 psf

sigma bot = 8 x 100 = 800 psf

sigma ave = 400 psf

Whole force `W’ on wall = 400 psf x 8 ft tall x 1 ft of wall width = 3200 lb.

Moment resulting from W (triangular load) = 0.1283 W L = 3285 lb-ft … (from reference materials, triangular distributed load, etc., blah, blah)

Mu = 1.6 M = 1.6 x 3285 lb-ft = 5255 lb-ft

STRENGTH

… try # 3 @ 4 in. o.c.

Doc

Assignment 3, posted with some more comments (notes) ...

2011-11-05T09:56:00.001-07:00

here: http://www.woodengineering.com/edu/wsu/463-563/463-563-assn-3.html

doc

Example and Help for Assignment 3 ... Problem 1 ... BENDING!

2011-11-03T22:24:00.000-07:00

Okay ... here is an example calc of the first problem ... except that I have only tried one rebar size, and the rebar is centered in the wall (d = 3 in.) instead of d = 4 in.

... though this sounds a bit `mean' ... I do want you to labor through these calcs. The likelihood that you (as Architects and/or CMs) will actually grind these calcs out in real life practice is slim (unless you become engineers) ... but the exercise will help you come to grips with the effects of rebar size, spacing, effective depth d, and so on. The relatively high backfill pressure is commensurate of at-rest pressure for clay-ish soils.

The wall in question is actually a very common design problem, particularly with ICF forms for 6-in. thickness (basement) walls.

Baby!!!

solution to # 5 ... basement wall reinf.

2011-10-19T18:12:00.000-07:00

numero quatro

2011-10-19T18:08:00.001-07:00

(see class notes for area loads and tributary widths)

Assignment 2 (WSU 463/563) Problema Tres!

2011-10-19T18:06:00.000-07:00

(See class notes for the line loads ...)

Lesson 6 - Assignment - Prob 2 SOLUTION ...

2011-10-19T17:59:00.000-07:00

Problem Statement: interior footing supporting 3 stories of conventional light frame construction ... ground snow load 25 psf, frost depth 24 in., foundation material gravel.

Lesson 6 - Assignment - Prob 1 SOLUTION

2011-10-19T17:58:00.000-07:00

HERE ...

i want one of these!

2011-10-18T22:10:00.000-07:00

hey - here is one nice thing about a concrete house - they are `2x4 proof' ...

wind cannon

doc

first hollow core?

2011-10-18T11:06:00.000-07:00

ha! ... this must be the first hollow core in the western united states, maybe the world! :) hollow core roof on the Sandpiper Bar in Moscow currently undergoing remodel (or ???). This building has been here as long as I can remember (over 30 years?). (And by other names, obviously, Mark IV? Restaurant, etc.) Also, the walls are no doubt pre-cast!

This is right across the street from the vet clinic in the earlier post (also across from Rosauers).

...

ICF in Moscow

2011-10-18T10:50:00.000-07:00

... as mentioned in class (WSU 463/563) there are a number of concrete houses (and businesses) in M and P, but you wouldn't know it as they look like `wood' (or other) construction. Here is a Vet Clinic / Residence in Moscow (across from Rosauers) that is ICF Main story walls and wood frame roof and attic.

The Village Center (?) Cinemas in Pullman have ICF walls for sound barriers between the indiv. theaters.

And the walls are tall!

...

landon's BWLs

2011-10-10T09:59:00.000-07:00

here's Landon's snap of the foundation sketch from the (UI) lecture on `where do we need continuous foundations' ...

(thanks Landon!)

...

Student Question on Rx Foundation ...

2011-10-07T12:22:00.000-07:00

NOTE: this is in reference to Arch 463/563 at WSU ... I have not handed out this assignment to UI 462 (yet).

... from an email:

Mr. Filler,

After reviewing problem number one at the end of chapter 6, it occurred to

me that there is no mention of how much weight each exterior footing has to

support because there is no mention of how wide the building section that we

are calculating is. If you would like to send the class an arbitrary

building width so that we could do the calculations that would be greatly

appreciated.

Thank You,

D ... snip

Great question ... that's the thing about Rx foundation design - you "don't have to know the building dimension, or the weight it has to carry" ...

Actually, you will know the building dimension, but all you need to know for Rx design is that it doesn't exceed the dimension limit(s) of the code.

And regarding the load ... you just need to know that you don't exceed the load limits ... 40 psf LL, 15 psf DL, etc.

The context of the problem is that the building `fits' Rx limits, so all you need to know is number of stories, etc.

Doc

Foundation Worksheet

2011-10-05T09:36:00.000-07:00

... here is a printout from an excel worksheet for dealing with these foundation calcs: (below).

I provide a link to the .xlsx file also (below).

http://www.woodengineering.com/edu/wsu/463-563/foundationworksheet.xlsx

Note a couple-three things: 1) with the worksheet it is easy to guess a footing size and then the spreadsheet calcs the weight and adds it in ... all you need to do is guess footing sizes until the f_p drops equal to or below the F_p (in our example 2000 psf); 2) on the board we had out MFDL wrong ... here it is fixed (above)!; 3) on the board we just straight added the DL, SL, and LL (the italicized D + S + L = ... 2851). We'll talk about the `Combinations ... ASD' later.

Doc

Batter

2011-10-03T10:44:00.000-07:00

Desmarais sent me these pics of a job he was at this past summer. Block wall(s). SERIOUS batter ... ughhhh ... looks like TOO MUCH batter. It wud be cool to know the story behind. Plus why some sections don't appear to have batter. Anyway - here are the pics - posted without permission.

On Foundations ...

2011-10-03T09:59:00.000-07:00

Baby!

Deck Framing

2011-09-30T17:12:00.000-07:00

So, check this out … a deck! These pics show what we have been talking about with the outboard framing for our `Sorority House’ deck.

Note the following:

1. The timber beams for this deck are NOT continuous over the supports.

2. The connection hardware shown is CCO type, meaning CC for `Column Cap’ and the O means that the straps that normally come with the hardware are `omitted’. Normally this type of hardware connects timber beams to timber columns and thus there are metal straps which bolt to the timber columns. Where the columns are steel, in this case probably steel pipe or round steel tubing, the hardware is welded to the tops of the columns.

Note that the support for gravity load is provided by end bearing of the beams on the `base’ part of the hardware.

Note that each beam is also anchored with two bolts (each end).

3. Note the joists framing OVER the support beams so as to be able to overhang past the beam (support line). These joists, however, overhang much farther than our Sorority House deck example.

4. And note the solid BLOCKING between the joists. We talked about this a little in class (I think). Such blocking is generally always required at supports to keep the joists from `rolling’ (rotating). This is a framing requirement that should always be followed unless specifically not required by a manufactured joist system or Engineer of Record.

Solid blocking between joists may also serve as `shear blocking’ in some applications, for use in lateral load path, though I don’t think this was the intent with this deck.

5. Notice the JOIST HANGERS connecting the joists to the ledger, in back. The joist hangers transfer gravity load and prevent the ends of the joists from rotating. They are also deemed to provide adequate anchorage (resistance to incidental lateral loads or movements.)

6. If you look real close you will see that the joist hangers are UPSIDE DOWN. What?!!! Yes! If you look at the way the deck is framed the overhang span is about the same as the main (interior) span. Thus the load controlling the joist hanger is probably the overhang span loaded and the interior span unloaded (or serious wind uplift on both spans). I much prefer overhangs that are short compared to the main spans. Perhaps in this application they wanted the beams-column line way in to keep them away from vehicle traffic below.

7. Note the ledger ANCHOR BOLTS … they are in two horizontal rows, staggered: one high and one low, like we talked about.

8. And finally, note the outboard rim joist. Overhanging joists (or beams) have tension on top and compression on the bottom face. Thus, the compression zone of the members are stabilized laterally. To reduce the unbraced length of the bottoms of the joists they are connected to the rim which prevents lateral translation and rotation at the ends. Imagine without the rim the joists would be more susceptible to twist under load (and maybe look weird).

doc

... and ...

2011-09-26T15:28:00.000-07:00

The coming exam is pretty easy. Really. There are two pages of fill in and one page of calcs. Do NOT make the calcs part harder than it is. And there are no trick questions (that I know of).

Typically the intent of my exams is to reinforce what you know, not find out what you don't.

Doc

... first EXAM ... hints and help

2011-09-26T15:22:00.000-07:00

here ...

... and don't forget to bring a copy of NDS Table 11E.

(Filler) Text Lesson 2 Answers

2011-09-26T09:58:00.000-07:00

are here:

(Problem 8 refers, of course, to Problem 7, not 6.)

Block wall in Pullman ...

2011-09-25T11:22:00.000-07:00

here are some pics I took of a block wall in Pullman this morning:

(the wall is directly east of the Pullman Wal*Mart)
(see conversation below)

The blocks are about 2 ft tall by 2 ft deep by 4 ft long ... so they are the same gross dimensions as the so called `ecology blocks (see earlier blog posts; 2' x 2' x 4' more plain looking blocks) ...

but they are formed on the exposed face to be made to look like they are perhaps made of smaller stacked blocks (and prettier)
note that they are partially hollow! ... this decreases cost and shipping weight ... but you will also need to get from the manufacturer (or calculate) the block and wall weights - as a function of what the hollow portions are filled with (gravel, grout, or nothing???) and the weight of concrete used.

note that there is an incline (slope) parallel to the wall ... so the wall is stepped and the tops of blocks horizontal. Every now and then I see a wall with the blocks parallel to the incline, and they don't look nearly as nice

also note the railing! railings are a `code issue' which you (architects and const managers) will have to deal with, but I generally don't deal with, or deal with only generically (identify only) as an engineer.

the funny thing is that the wall is out in the `middle of nowhere' ... so the railing is for???

well, the cemetery is behind and to the right.

hospital is out of the pics to the left.

which brings up something I have always found a bit funny: why did both Wal*Mart and the Regional Hospital conveniently locate with the cemetery right out the back door???!!!

rebar on top and bottom, positive and negative moments

2011-09-22T17:41:00.000-07:00

here is a post I did for my Structures I class (WSU) ... it's a decent review on V and M diagrams ... AND WHY !!!

http://a351.blogspot.com/2011/09/75.html

Outer Deck Piers and Footings ...

2011-09-21T19:15:00.000-07:00

here is the solution for Assn 2 Prob 1 for UI 462

(which is similar to the second problem for Assn 1 Arch 463/563 WSU) ...

Note the use of a 12 in. diameter pier. (That's the way the UI folks wanted to do it.)

Block Ret Wall Problem ... BABY! THIS IS HOT!!!

2011-09-17T11:18:00.000-07:00

lateral ties ...

2011-09-15T10:23:00.000-07:00

Here is a web page on the HDQ8 lateral tie I passed around class yesterday. (BTW - where did it go? Did one of you put it in your pocket and sneak it out of the room? LOL)

http://www.strongtie.com/products/connectors/HDQ-HHDQ.asp

Toward the bottom of the page it shows the holdown being used as a lateral tie to concrete.

They can also be used to tie girders together across a beam ... probably shown elsewhere in the Simpson literature.

And a common use is as a holdown at the end of a shear wall (shown).

I am thinking the `H' and the `D' stand for `holdown' (or maybe `heavy duty'). And I am thinking the `8' stands for an allowable load of about 8000 lb. Note: we can get over 9000 lb if we install it into a 4-1/2 thick member (say 3 ply 2 x ...).

We only need 1000-ish for our example. The HDQ8 would be way overkill.

And I think the `Q' stands for the self-tapping screws it comes with, as opposed to thru bolts. I'll bring examples of the screws.

...

Retaining Wall Nomenclature

2011-09-13T11:44:00.001-07:00

here ...

Retaining Wall Equations

2011-09-13T11:33:00.000-07:00

by request, here are our equations for the External Stability calcs for a (block) retaining wall ...

interior support reactions

2011-09-06T22:51:00.000-07:00

... so, here is the `interior support reactions' thing I spoke about in 463/563 (wsu):

for `simple beams' of span L and loaded uniformly with `line load' w, the `Whole' load W is wL and it divides out equally (equal halves) to each end reaction ... wL/2 ... or W/2.

... for two simple spans the interior support gets two ends' ... so 2 x wL/2 = wL.

... for a beam spanning continuously over the interior support, equal spans, uniform load on both, the reaction at the interior support is MORE than if two simples ... 25% more ... R = 1.25 wL = 1.25 W.

... for a beam with 3 continuous equal spans (spanning continuously over 2 interior supports), same uniform load on all spans, blah, blah, ... the interior supports carry 1.10 wL ... 10% more (than if 3 simples).

... for a beam with 4 continuous spans, blah, blah ... at the very middle the reaction is 0.928 wL ... a little less than wL ... and at the quarter points 1.14 wL.

...

I generally boil it down to theses cases:

1. Simple span ... wL/2 each end.

2. Two span continuous ... 1.25 wL in middle (25% increase).

3. Three or more span continuous: 1.15 wL for interior supports (15% increase).

4. Two span continuous OR 2 simples: 1.25 ... giving contractor option ...

5. Three or more spans continuous OR (all) simple ... 1.15 ...

and ...

I use wL/2 for the ends, all cases.

...

... and remember!

2011-08-31T09:25:00.000-07:00

my intent in this is that you understand physically what is going on. Once you understand physically - it is a lot easier to put numbers and `equations' to it.

Combined pressures ...

2011-08-31T09:24:00.000-07:00

... that was a HOT! lecture (today, 8/31, Struct III, WSU). Be sure you have a handle on this soil pressure thing. I will blog some examples once I get more `caught up', LOL. Your Structures I, II text talks about this a little ... look on pages 133-135 of the Ambrose-Tripeny 10th edition text, or pages 142-144 of the 11th edition. The texts also talk about combined axial and bending (flexure) stress (beams and columns) - but probably covers it differently. Basic Mechanics of Materials textbooks will also cover the topic.

Column Bases

2011-04-26T21:12:00.000-07:00

Sadly, I see this a lot! The column and the pier/pedestal somehow :) not aligning. The result is that the pedestal is not loaded in the middle FOURTH (of the diameter -as we discuss in class). Also, it is unlikely that the embedded portion of the base hardware has sufficient concrete cover. Something also appears a bit out of plumb.

Couple other things: 1) it's nice to have the wood standing off the concrete a ways - to avoid moisture-decay problems, and 2) the forming for the pier-pedestal must be removed if the pier is to resist any significant lateral force.

The column in back appears to be better centered.

Demolition Engineering ...

2011-01-26T10:37:00.000-08:00

...
On several occasions I have been called upon to provide Demolition Engineering. (It's not as exciting as it sounds!) I should probably say - `Shoring Engineering for Demolition'. It is exciting in the sense that it is intense - and it requires one to think outside the box - as there really isn't a textbook on the subject. (At least I couldn't find one when I needed one.) No, we didn't explode buildings. My role was to engineer the shoring required so that the building(s) could be taken apart, and rebuilt, without collapse. Where `structure' was taken away - temporary shoring had to be provided. In some cases it was necessary to support rather heavy `demolition robots' (big remote-controlled robots that destroy stuff - kind of like in a sci-fi movie - Transformers or something).

Pictured is the University Classroom Center at the University of Idaho being (majorly) remodeled into the now Teaching and Learning Center (TLC). Large openings were cut in the north wall. Shoring is provided by metal bracing. The bracing was attached using Simpson Strong-Tie concrete lag screws. These screws are removable - perfect for temporary use.

One thing I like about Demolition Engineering - is that once the remodel is complete - there is no more liability ... NO RESIDUAL LIABILITY! ... unlike most of the other projects an engineer takes on.
...

Spring 2011!

2011-01-06T16:32:00.000-08:00

Go Cougs!

... hey, my attention will go from this blog to http://woodengineering.blogspot.com/ as I travel to Malaysia to teach them about Glulam ... and teach wood and steel engineering at WSU upon return.

...

Bond and Bar Size ...

2010-12-10T15:15:00.001-08:00

So, in regard to bond (grip between the concrete and steel), size (of rebar) does matter: smaller is better. Other things equal, smaller bars are more efficient in receiving the stress from the surrounding concrete; it’s a function of the bar-concrete contact area and bar cross-sectional area. How this plays out is that for smaller bars we generally have shorter embedments and shorter splice lengths. But, more of them (more bars, for any given load). If we have too small of size of bars, however, we get congestion and increased labor costs. Where possible - I lean toward smaller size bars - with plenty of concrete surrounding to provide protection and bond - and not spaced so far that there are large volumes of concrete without reinforcement.

Floor to Wall Connections ...

2010-12-06T15:47:00.000-08:00

... from the Lesson Outline sent ...

6. Conclusion

So, we have several things going on: the wall-to-floor attachment taking lateral earth pressure loads from the high-backfill wall up into the floor; the floor-to-wall attachment of the adjacent walls taking lateral loads from the floor (back down) into the (adjacent) walls; we have the floor-to-wall attachments taking gravity (Occupancy and Dead) loads from the floors to the walls; and we have floor joists parallel to some walls and perpendicular to others. Of course any one connection may serve several purposes. As a designer you will need to make sure all conditions are satisfied … using a reasonable amount of detailing.

...

ICF Floor to Wall Connections ...

2010-12-04T16:55:00.000-08:00

... here are some ICF floor-to-wall connection details. This is the LOGIX system ... (here).

Sometimes I have `these people' come present to the class. They are formerly the ARXX people, formerly Blue Max ? ...

(They are busy people as this stuff is really catching on.)

I really like the ARXX system, and this LOGIX seems to be the predecessor, or at least an offspring.

Doc

Design ...

2010-12-03T16:46:00.000-08:00

Simpson ICF Connectors

2010-12-03T16:40:00.000-08:00

Here is the current Simpson Strong-Tie ICF Connectors Catalog.

Good stuff ... (here).

Hip Roofs and Openings ...

2010-12-03T16:24:00.000-08:00

Here is a sketch of how a hip roof might be framed (manufactured roof trusses).

The main part of the roof will have `regular' trusses (with ridge in middle, etc.). Then, generally down the hips a ways, there will be Girder Trusses (GTs). These generally carry MORE load ... contributed from the ridge trusses and jack trusses or rafters framing the ends of the hips. This is important to our present conversation in that: 1) the GTs deliver relatively heavy concentrated loads, and 2) the hip framing makes the ends walls load bearing.

With regard to the concentrated loads ... we need to make sure they don't come down over openings. This can be accomplished by:

1. demanding the truss manufacturer to consider the opening locations and design their truss layout accordingly, or, ...

2. we the designer make sure we don't have openings where the truss manufacturer puts GTs ...

OR ...

3. we allow GTs to fall over openings ... and thus design the opening (lintel) accordingly (hire an engineer).

...

Some stuff from the Presentation ...

2010-12-01T13:50:00.000-08:00

Gosh, you (prev post) look so attentive! Ryan gave us a bunch of good stuff ...

There is a LOT of work, money, time, etc. that goes into providing you with these anchors. Simpson publishes oodles of good stuff, and they are only a phone call away if you need something more.

I liked how Ryan pointed out the Coordination Between Trades issue ... where the concrete contractor may be placing anchors to the complete frustration of (or disregard to) the framing (contractor). Post-installation anchors are a remedy.

The Titen HD anchors are also sweet in demolition and temporary construction applications.

Proper mixing, etc. of the adhesive with the epoxy and acrylic anchors is important. I have been astonished with how, with a little lack of care, these anchors can get messed up, ... and thus the Code, and/or Building Official, may require Special Inspection ... to make sure installation doesn't get messed up.

I caution you architects - be CAREFUL you don't get caught inspecting or approving installation unless that is SQUARELY your role (responsibility). Inspection is ultimately the responsibility (though not necessarily role) of the Owner. You need to appraise/educate/advise the Owner with regard to inspection issues ... but it is unlikely you will actually do (structural) inspections.

Recall also where Ryan showed us the photos of the expansion anchors where they caused the concrete walls to spall out. With expansion anchors it is very important that the edge distances are observed ... or use another anchor. Fixing a wall that has been broken out like those shown is ... ughhhhhh.

Doc

Ryan Edwards, Simpson Strong-Tie

2010-12-01T11:47:00.001-08:00

Area Rep for Simpson Strong-Tie, Ryan Edwards, giving a presentation today in Arch 463/563.

THANK YOU RYAN.

Ryan's Contact info:

Ryan Edwards, Territory Representative

Direct: 209-944-1064

Mobile: 208-755-9513

redwardsATstrongtie.com
http://www.strongtie.com/

Roof and Ground Snow in Pullman

2010-11-23T10:14:00.000-08:00

Snow here ... depending on where you live - a foot or so on the ground. But LOOK! - on roofs and other elevated surfaces - 8 inches or so ... I love it ( ... the snow).

In general, roofs and upper surfaces tend to collect less snowfall ... due mostly, IMO, in the present case, to some wind along with.
Doc

Check it out: http://www.associatedcontent.com/article/1236532/snow_loads_on_roofs_and_decks.html?cat=6

Wood Frame Floor - Concrete House

2010-11-22T15:54:00.000-08:00

... hey, here is the Trus-Joist Specifier's Guide. Note the spans we can get with their various series joists on page 4.

http://www.ilevel.com/literature/TJ-4000.pdf

A common joist spacing is 16 in. o.c. ... so we could use the 9-1/2 or 11-7/8 in. depth joists if we have a bearing wall down the middle ... or a 16 in. joist to go clear across, ext. wall to ext. wall.

THE OTHER REAL COOL THING ABOUT PAGE 4 ... LOOK OVER ON THE RIGHT HAND SIDE ... IT HAS WEIGHTS OF VARIOUS BUILDING MATERIALS.

...

Assignment 11 - SOLUTION

2010-11-16T14:05:00.000-08:00

Here is the problem statement: ... here.

And the solution: ...

...

Short STABLE Wall ...

2010-11-16T09:37:00.000-08:00

...

So, here is a short wall that IS stable ... 18 in tall and 16 in deep (thick!).

Posted via mobile device ...

Index Page ...

2010-11-15T22:33:00.001-08:00

Don't forget to check the Index Page from time to time ... lately I have been linking homework solutions and other good stuff off it.

http://woodengineering.com/edu/wsu/463-563/

...

Exam coming up ... HINTS

2010-11-15T21:20:00.000-08:00

The Exam has a lot of fill ins ... pretty much straight from lecture, etc. There is one question, however, that's from a blurb posted on my office door. Here - I'll scan it and post it below - to minimize the traffic in our serene hallway.

You should do Assignment 11 before the exam (hint, hint), even though it's not `due' until the 19th. Just do the dang thing and turn it in on the exam day, then you don't have to worry about it. Plus it will be good studying.

I'm not planning on posting the solution to 11 before the exam, but it doesn't hurt to check back just in case I change my mind.

There are no trick questions, or mis-spellings, or typos, that I know if of. There is one problem that will require a tiny bit of common sense to get started.

Make sure you have a table of the Unified Soil Classification symbols, meanings, etc. with you ... and look at (digest) it before hand (hint, hint).

Yes, bring your calculators.

Doc

Bracing ...

2010-11-15T12:29:00.000-08:00

Hey, check this out ... in the November issue of the Simpson Strong-Tie NEWS ...

Bracing Calculator: http://www.strongtie.com/products/strongwall/wallbracing/intro.asp?newsletter=Nov10

...

Calculated Footing Width … for a BASEMENT Wall

2010-11-12T12:53:00.000-08:00

...

EXAMPLE

So, here (See Figure 1) is an example where we might need to calculate a footing width for a structure that might otherwise be able to be determined `prescriptively’. The example has three conditions that might `knock it out’ prescriptively(a).

These conditions are:

1. A heavy design roof Snow load (in this case 60 psf)

2. A concrete topping on the wood framed floor (will exceed conventional wood framing Dead load), and

3. A relatively thick concrete basement wall(b).

Notes:

(a) Many jurisdictions have Code provisions to accommodate conditions that are outside the limits of, say, the IRC and/or the IBC, but are common to their particular locale.

(b) Some codes accommodate 8 in. thick `concrete’ walls in prescriptive footing designs.

Any one of these conditions may necessitate calculations; here we will tackle all three.

The `steps’ in footing design, recall, are:

Step 1 – we will make the footing wide enough to not fail the soil.

Step 2 – we will make it thick enough to not shear (the concrete).

Step 3 – we will add reinforcement as needed (so it doesn’t break).

STEP 1 – FOOTING WIDTH

First we need the LOADS on the footing.

The trusses span from exterior wall to exterior wall.

The upper floor spans from exterior wall to interior wall (to exterior wall).

One way to get the weight of the added (lightweight) concrete floor is …

First calculate the `area’ weight of the lightweight concrete per inch of thickness … it will be the weight per cubic foot divided by 12 (12 in. per foot).

So, lightweight concrete weight per inch of thickness is … 100 pcf / 12 in. (per foot) = …

… 8.3 psf (per inch).

For 3 inches of lightweight concrete, then, we have …

… 8.3 psf per inch x 3 inch. = 25 psf. We need to add this to the presumed weight of the wood framing supporting it.

The presumed framing weights are:

15 psf for Manuf Truss Roof

15 psf for Manuf Wood Floor Supporting the 3 in. of lightweight concrete

5 psf for wood furring of basement wall

10 psf for exterior wood framed wall.

And, Occupancy Live load … use 40 psf (Residential).

So,

Using w = line load = area load x trib width …

Roof SL = 60 psf x (18/12 ft + ½ of 30 ft) = 990 plf SL

Roof DL = 15 x (18/12 + ½ of 30) = 248 plf DL

Upper Wall DL = 10 psf x 9 ft height = 90 plf DL

Upper Floor LL = 40 psf x ½ of ½ of 30 ft = 300 plf LL

Upper Floor DL = (15 psf wood + 25 psf conc.) x ½ of ½ of 30 ft = 300 plf DL

Basement Wall DL = (10/12 ft)(10 ft)(150 pcf) for the concrete and 5 psf x 10 ft furring = 1300 plf DL

Guess Footing DL = … 500 plf

Adding up SL, DL, and LL separately …

SL = 990 plf

LL = 300 plf

DL = 2438 plf

We can add these straight together to get a footing weight, but it is unnecessarily conservative to combine the full Snow and Live loads simultaneously. For Allowable Stress Design (ASD), which is what we will use with the allowable soil pressure, the loads combine as follows:

D

D + S

D + L

D + 0.75 (S + L)

For which we must examine the `worst case’ (greatest load).

For our example,

D = 2438 plf (obviously won’t govern)

D + S = 3428 plf

D + L = 2738 plf

D + 0.75 (S + L) = 3405 plf.

The D + S governs at 3428 plf.

The required footing width, using the Allowable Soil Pressure of 2000 psf is …

... width required = 3428 plf / 2000 psf = 1.71 ft

… or … 20.6 in.

Before we make any `final’ decisions let’s check the estimated weight of the footing.

If it is, say, 21 in. x 10 in. thick, this would give us a weight of …

… (21/12)(10/12)(150) = 219 plf.

Our estimate of the footing weight was … well, overkill.

Re-doing the calcs … maybe we can get into a footing width of 20 in.

Using a 20 x 10 footing …

… footing weight = (20/12)(10/12)(150) = 208 plf

D = 2146 plf (using 208 instead of 500)

D + S = 3136 plf

D + L = 2446 plf

D + 0.75 (S + L) = 3113 plf.

The D + S governs (again) at 3136 plf.

Check soil pressure:

… f = line load / width = 3136 plf / (20/12 ft) = 1882 psf … which is less than 2000 psf … GOOD.

We could possibly go even smaller, but let’s settle at 20 in. width.

STEP 2 – FOOTING THICKNESS

One (easy) way to make sure that it doesn’t shear is to make it at least as thick as the footing projects out past the wall.

This projection is … x = (20 – 10)/2 = 5 in.

Whoa, that’s pretty thin … well, it’s partly because we have a thick wall.

Let’s use the 10 in. thickness we have already chosen … though we could possibly get away with 8 in.

So, … 20 in. x 10 in. footing …

STEP 3 – REINFORCEMENT

For the longitudinal steel …

A_s = 0.0018 (20 x 10) = 0.36 sq. in. … let’s use 2 - # 4 bars ( … 2 x 0.20 = 0.40 ≥ 0.36, good), where 0.0018 is the amount for resisting temp-shrinkage effects (for Gr. 60 steel).

For transverse steel … for a footing this wide, and particular since we have left it pretty thick, let’s use no lateral reinforcement.

If the Building Official requires lateral reinforcement … we can determine it at the 0.0018 ratio, or by doing flexural calcs … or …

If the Building Official requires calculations for our not using lateral reinforcement … we can do calculations showing it isn’t necessary (see REFERENCES).

ANSWER: FOOTING: 20 in. x 10 in. with 2 - # 4 longitudinal steel evenly spaced and placed 3 in. clear above bottom of footing.

REFERENCES

On tributary width calculations (general) … here.

Other examples and information on footing size calculations based on superstructure loads:

     Lesson 7 and Appendix 2 of Filler (Draft) Text … (here).

     Calculated Footing Design with Added Weight of Concrete Floor (Article) … here.

Calculations for Footings without Transverse Reinforcement:

     Using Strength Design … here.

     Using Allowable Stress Design … Filler Text Appendix 3.

Calculating the weight of concrete (beams, floors, etc.) … Filler Text Appendix 1 or here.

Load Combinations in Allowable Stress Design … here.

...

Assignment 11 ... 6 in. thick basement wall ... do it!

2010-11-10T21:06:00.000-08:00

Here it is ... Assignment 11 (here) ... do it while it is fresh. Maybe I'll do it with # 5 rebar - but don't wait for me.

Doc.

Assignment 8 ... Solutions

2010-11-10T13:32:00.000-08:00

...

Problem 2 …

… note that if we use the Ambrose Table 16.1 … we go back to using the unfactored loads … 1500 plf and 2500 plf … = 4000 plf total applied load (to top of footing).

Note: Ambrose gives (for our Prob 2) … #3 @ 11 in. o.c. for short-direction (transverse) reinforcement. Eleven is kind of odd … I might round it down to 10. Today in class we substituted # 4 for # 5 bars (with closer spacing) in a wall calculation … as the footnotes in the Table in Code allowed us so. In general we can substitute smaller bars, with smaller spacing … but, in general, we cannot substitute larger bars with larger spacing, unless we deal with additional issues (such as development length … and overall max spacing regardless of bar size*).

We could, however, substitute larger bars at the same spacing. The only reason one might do that would be an on-site decision if the larger bars were sitting around (available) … and the contractor chose to use them instead of `making another trip to the store’.

So, on Problem 2, using the Ambrose solution, without too much fuss, I’d probably say …

“ … # 3 or # 4 @ 10 in. o.c. lateral steel.”

My solutions are up … via the index page.

_____________
*Remember, we use reinforcement (rebar) to control cracking … so if the bars are too big, and too far apart, there end up regions of concrete that `practically’ aren’t controlled by the rebar.

... for Betsy

2010-11-09T08:45:00.000-08:00

... this may help you in drawing up your deck plans ... it's for a concrete house, but you can kind of see what is going on as you draw up your page of conditions, specifications, construction requirements, etc. ... here.

One Way Basement Walls ...

2010-11-08T20:38:00.000-08:00

Today we started our conversation about one-way basement walls. By one-way I mean spanning (structurally) one direction, that is, vertically, from floor to floor. And this is one way of doing basement walls ... but it requires floor attachment top and bottom (that we also talked about). In this Course we will `do' them prescriptively. We could also design them by calculation (as I also said in class). And here is an example: here. It is more than most of you would want to embrace - though you have the tools now to do so. Any engineers looking on my want to take a look (it's a popular article).

I mentioned in class the two-way walls, and the prescriptive solution in the (Filler) text that provides maximum lengths of walls for various wall heights, thickness, backfill type and height, and so on. Or you can read about them ... here.

I want to be clear on a thing. In some calculations ... like the reinforcement for a footing, or a wall, based on, say, temp/shrinkage steel minimum, or some value like 0.0012 or 0.0020 mentioned in class ... these are per the full (slab or wall) thickness. But when we start doing flexure calcs, the reinforcement ratio is then based on the effective depth. So, for example, if we have a 10-in. thick wall, and determine the required reinforcement using 0.0020 ... for, say, #5 bars, we would get ...

... s = a_s / (b h) = 0.31 / (0.0020 x 10) = 15.5 in. ... round down to 15 in.

... and then if the steel is in the center (d = 5, from either face, depending on the direction of flexure), and we start doing flexure calcs with it ...

... our ratio is a_s / ( s d ) = 0.31 / (15 x 5) = 0.0041.

The reinforcement ratio is double! ... (since we are basing it on a depth that is half!)

So, be clear on your reinforcement ratios.

Doc

Also: here is an article on rebar spacing (this is also an Appendix in your text): here.

...

Eco Blocks

2010-11-08T12:59:00.001-08:00

The Eco-Block ... Used here as a barrier. Oft used in ret walls. They are 2' x 2' x 4'. From our conversation on ret walls you should be able to tell me how high we can stack them to retain earth and be externally stable. (Yeah, 2 high.) Note male/female features for resisting shear (sliding one relative to another) when stacked ... and the steel loop for placement by crane. (A bit heavy to place by hand.)

These have pretty `plain' faces. They can also be cast to have a brick texture, or whatever. Often they are made of waste concrete coming back on trucks with leftover concrete.

( ... now, you should be able to tell me about how much one of these weighs ... made of normal weight concrete.)

Placing by hand ...

2010-11-04T15:10:00.000-07:00

... whoa ... apparently ACI 332 (Residential Concrete Construction) allows placing footing reinforcement by hand (holding it in place while concrete is poured around it ... that thing I X'd out in class on the board) ... I certainly don't recommend it. (And the Building Official might not like it either.)

CMU CONSTRUCTION

2010-11-04T14:48:00.000-07:00

CMU (Concrete Masonry Unit) Construction is cool stuff. There are a couple CMU buildings going up in Moscow presently ... take a look next time over there - on the main drag going into town.

CMU construction is basically `concrete' construction ... the end products of CMU and CIP concrete being in many ways a lot similar, but coming about completely different.

CMU blocks are cast at a manufacturing plant, and are mortared into place on site.

CIP, of course, is concrete cast on site.

CMU may be plain, or reinforced, like CIP ...

Both foundation and above grade walls may be CMU, and be plain or reinforced, like CIP.

And the reinforcement for CMU is, like CIP, typically deformed bars (rebar) ...

A big difference with CMU vs. CIP is that the CMU blocks have cavities, and thus the finished product often has cavities.

Where reinforcement is required ... the cavities are filled with (concrete) grout around the rebar! And so in the end a rectangular CMU column might look a lot like a rectangular CIP column.

CMU = concrete blocks, mortar (between the blocks), and grout (in the cavities) ... and rebar, if reinforced.

CIP ... concrete paste (or `mud') ... sometimes called grout ... and rebar, if reinforced.

CMU has some other stuff that we haven't talked about - but we haven't (yet) talked about everything in CIP concrete.

A CMU column in a wall is typically called a `pilaster' ... so there are some name differences.

AND THE BUILDING CODES (INCL. DESIGN) FOR THE TWO (CMU VS. CIP) ... ARE VERY DIFFERENT.

I have been intrigued over the years with CMU construction and design - but there just isn't / wasn't enough CMU around here ... to motivate becoming an expert at it.

...

CMU in Moscow ...

2010-11-02T14:08:00.001-07:00

CMU in Moscow ... we may or may not discuss CMU (Concrete Masonry Units) in class - but it's COOL STUFF.

I have a lot of respect for these guys. I have placed CMU block - and it is not easy. I have also done some CMU design work - but not enough to talk a lot about it.

Doc

Assn 8 Prob 1 ...

2010-11-01T15:47:00.001-07:00

Assn 8 Prob 1 ... I come up with NOT having to cut the slab. I'll let you produce the numbers. Had it come out otherwise, but close, we could have explored using a bigger base.

In punching shear problems increasing the base size gives us a lot of mileage ... since it increases the `periphery' (4 x) ...

(sent by mobile device) ...

...

Columns ... cont.

2010-11-01T12:19:00.000-07:00

... so, obviously, what I meant to say was that: we can have round columns with either (round) spirals or rectangular ties (and some excess concrete to get the round shape, if needed). And, we can have rectangular columns with rectangular ties, or with spirals (and excess concrete to make the `round' shape).

I suspect that spirals are more expensive to buy... while ties are more expensive to `tie' (install).

Columns with spirals have a higher phi (0.70) than those with ties (0.65) ... thus, columns with spirals could either be smaller, or achieve needed strength with less reinforcement (than those with ties).

And finally (and I did not mention this in class ... at least not today) ... in column design it is more affordable to use higher strength concrete ... since they are `compression' members ... and typically all the concrete in the section is acting (dissimilar to beams).

...

Problem 3 ... and ... Spacing of rebar ...

2010-10-29T14:40:00.000-07:00

I changed the numbers of Problem 3 (of Assignment 8) ... they should now read:

1200 plf DL
2500 plf LL
3000 plf SL

The problem works out better with these numbers.

Note: if you end up calculating rebar spacing ... here is the equation ... I don't remember if I have given it to you yet, but if not, it's in Appendix 4 of the Filler text - along with some other good stuff.

s = a_s / (rho x h) ...

where,

a_s is the area of a single bar,

rho is the reinforcement ratio used,

and

h is the footing thickness (or wall thickness, if calculating spacing in a wall).

Cool.

... more examples ...

2010-10-29T10:04:00.000-07:00

Appendices 2 and 3 of the `Filler' text have (additional) examples of footing width, thickness, and reinforcement calculations. In Appendix 3 I go through an example showing that transverse reinforcement is not required ... using `allowable stresses' in concrete. For wider and more heavily loaded footings - reinforcement will be required in both directions.

Larger Footings ...

2010-10-29T09:49:00.000-07:00

FOOTINGS …

STRIP (FOR WALLS) OR SQUARE (FOR COLUMNS)

Once we get footings about 30 in. wide or wider, whether they are strip (wall) footings, or square (column) footings … our process of `making them thicker than they project past the wall or column’ … begin making them pretty thick. It (our method) was `easy’, convenient, but a bit lazy, as we didn’t even have to calculate a shear load on the footing. (Due to the diagonal tension crack there is NO effective shear on the footing.) We can make the footings less thick, but we need to make sure that the resulting shear load doesn’t exceed the shear strength. It’s quite doable (the calculation) – but I spare you from it and we’ll go a different direction.

Look at Table 16.1 in the Ambrose text. The Table gives various footing details (width, thickness, and reinforcement) for various line loads and allowable soil pressures. Note that the smallest width is 36 in. … and also that for the 36 in. wide footings he `gets away with’ 10 in. thick footings.

But also note that it comes at a cost … the Table details reinforcement in both directions. For our smaller footings we generally detail reinforcement going in the long direction only (not across). For the footings in the Table there are also short pieces going across, or `transverse’ in the footing.

So, here is my rule of thumb for you …

For footings 30 in. or so wider, up to 36 in. wide, use a thickness of 12 in., and put reinforcement in both directions at a ratio of 0.0018.

(Note: the Table assumes wider walls than we might be working with using wood framing … that’s why I say use 12 in. thickness.)

For 36 in. and wider … use the Ambrose Table.

For COLUMNS …

Essentially the same thing … for square footings of say 30 to 36 in. width … go with 12 in. thickness and reinforcement at 0.0018 each way, placed 3 in. clear from the bottom.

For footings 36 in. x 36 in. and larger … use Table 16.4.

Or hire an engineer.

Doc

... from Today's lecture ...

2010-10-29T09:13:00.000-07:00

I looked, and the CB5-6 (Simpson Strong-Tie Connectors Catalog) has a stirrup that embeds D = 8 in. into the concrete. Since our footing is 13 in. thick, we have enough room (13 in. minus 3 in. clear from bottom gives 10 ... and so 8 is good).

Note ... if we wanted to use the existing slab - we would need to look through the Catalog and find a hardware that would accommodate the 5-1/8 x 6 column and have (or allow us to weld on) a stud or rebar or something that we could epoxy into the slab. The stirrup for the CB5-6 is for casting-in-place ... wouldn't work for attachment to existing concrete.

Also, we came up with 4 - #4 rebar each way ... we could also have come up with 3 - # 5 each way ( ... 3 x .31 = .93 sq.in.). In fact, we could give the Contractor BOTH options in our detail ...

" ... 3 - #5 or 4 - #4 each way, evenly spaced, placed 3 in. clear from bottom ..."
...

Shear Strength Equations for Slabs ...

2010-10-27T19:44:00.000-07:00

... here are the equations from today ... the ones for reinforced concrete are from the Code and also appear in the Ambrose text. The ones for plain concrete I provide from the Code.

We'll deal with this bo thing in class ... if you want a head start ... peek at Ambrose p. 490 ... the `perimeter' of the equivalent shearing surface at distance d/2 from the faces of the column is the bo above.

...

Investigation of Existing Slabs - Today's Lecture!

2010-10-27T19:41:00.000-07:00

On holding rebar in place ...

... the movie I referred to in class today is The Hurt Locker ... where the bomb expert is asked, "Soldier, what is the best way to disarm a bomb?" He answers, "The way you want to."

Let an expert solve a problem the way he wants to - and you will see magic, talent! ( ... kind of like watching the Univ of Oregon football team do their thing on the field). Let an idiot solve a problem the way he wants to ... disaster.

So, hopefully you will have good construction people placing your rebar - but in case not - you will have inspectors! Don't tell them how to create your work of art - let them figure it out - but your Construction Documents need to be clear on what the work of art is to be. Be very careful as Architects (Owners' Reps) getting caught in an inspection position ... okay-ing something you shouldn't. Good supervisors (Const Managers?) and inspectors will (hopefully) catch poor construction practice as it is happening.

"Owners (and sometimes Architects) get talked into the most amazing things." ... and once talked into something - it may be too late to back out!

... here is a beam with some rebar chairs (near bottom of pic and up toward end of beam, hard to see as they are narrow and dark plastic) and with a piece of concrete ... that all hold the rebar at the proper depth. Also, if you look near the bottom of the pic ... there is some wire that goes through the form, around the bar, and out the other form ... holding the bar in place side-to-side.

On the example we were working on ... class was ending when we discussed rebar for the 6 x 12 (strip) footing. We could probably prove that no rebar is needed at all - but many building officials will want to see some longitudinal rebar (rebar going the length ... long direction of the footing) ... SO ...

... using rho = 0.0018 ... we get As = 0.0018 x 6 x 12 = 0.13 sq. in. of steel ... let's use 2 - # 3 placed mid-depth, evenly spaced, and call it longitudinal steel.

Doc

...

SECOND EXAM - SOLUTION ...

2010-10-25T19:30:00.000-07:00

Here is my solution to the Second Exam ...

NOTES:

1. The term `sheer' is not one normally appearing in construction documents ... though I have seen architects use it when they meant to say `shear'. If you somehow found a way to use it on the exam - consider it a small price to pay learning NOT to use it professionally.

2. On Prob 13 ... if the beam is exposed to weather, etc. ... then the required cover is 2.0 in. for # 6 and larger. For beams not exposed ... it's 1.5 in. So, if you assumed 2.0 ... that's fine ... but, strictly speaking, it's from the outside of the # 10 ... and since there is a 0.5 in. diameter tie around all the # 10s ... it's the same as saying 1.5 in. from the tie (whether exposed to weather or not).

Anyway ... HERE ...

Investigation of Existing Slabs

2010-10-25T19:06:00.000-07:00

... here is an outline for investigating the use of existing slabs for (new) concentrated and line loads ...

http://woodengineering.com/edu/wsu/463-563/investig-of-existing-slabs.pdf

...

other things equal ...

2010-10-23T18:33:00.000-07:00

...

Studying for the EXAM ...

2010-10-22T14:26:00.000-07:00

Remember, I generally make the exam straight from what we do in lecture ... so study the notes, and the calcs we did in class.

Make sure you have handy any tables I talked about and we used ... Ambrose Table 13.10, the factors on p. 377, the cover and spacing pages, etc.

And study the homework - and my posted solutions.

The calcs we do in class, and most of the hw problems are cast in terms of long, knock-down-drag-out `design' problems.

On the test, realistically, I will not give you a whole, long problem, but you should be able to tackle any part ...

So, for example, if I give you a beam that is 6 in. wide and 7 in. deep and the rebar is centered 2.5 in. from the bottom, and if the concrete strength is 4000 psi ... you should be able to give me the beam shear strength, Vc.

If I give you a beam that is 13 in. wide, and I am trying to fit 4 - # 10 bars in one layer, plus #4 ties around the layer ... will it all fit and still accommodate the Code requirements for concrete cover and bar spacing?

And could you calculate, for example, the Mult = Mn of the 6 x 7 beam above ... if the rebar is 1-#6 Gr. 60 ...

And could you tell me if this is a `legal' amount of rebar (not less than min. and not more than max)???

And that you understand the concepts in class ... for example, what is behind the Load factors, Strength Reduction factors, ASD and LRFD / SD approaches.

DON'T PANIC - IT REDUCES YOUR BRAIN'S ABILITY TO THINK PRODUCTIVELY.
Get to the exam a bit early ...

GO FOR IT!

... final calc for REVIEW ...

2010-10-22T14:16:00.000-07:00

... we ended class with needing to check the [       ] term. Remember in our method we `estimated' it to be 0.9 ...

So, on the attached scan I show how we then actually check it. It turns out it's LESS than 0.9 ... being 0.87 or something.  So our moment would be less, and so on. But what saves us in this case is that we had to round up to a whole number bars ... giving us more steel, and it more than compensates for the smaller d* (remember d* = d [            ] ). (Yay!)

Had the [         ] knocked us too far down in strength ... we would have to add more rebar, or crowd the rebar down in the beam a bit.

Enjoy!

...

Assignment 7 - SOLUTION ....

2010-10-22T13:34:00.000-07:00

... here are strategies for a couple methods to solve the problem, with Method 2 hammered out ...

http://woodengineering.com/edu/wsu/463-563/assn-7-sol-method-2.pdf

BABY!!!

Assn 7 - Solution!!! - METHOD 1 ...

2010-10-22T13:27:00.000-07:00

Okay ... here is the solution by fancy algebra ...

...

assignment 7 ... approach

2010-10-21T16:17:00.000-07:00

... here is an approach to Assn 7 I worked up ... actually containing 2 ways to attack the problem (link below). Note that many of the required `numbers' we already did in class ... for example, we already calculated Mcr, Vc, Mult, ... you may simply refer to those numbers from class notes (and include a copy of your notes as an appendix, or simply re-calculate ... Vc = 2 b d sqrt f'c ... and so on.).

http://woodengineering.com/edu/wsu/463-563/assn-7-approach.pdf

Doc

Simpson StrongTie ... DECKS

2010-10-20T10:42:00.000-07:00

Hey - I peeled this off the Simpson StrongTie newsletter ... to add to our conversation about decks ...

http://www.safestronghome.com/resources/video-bssd.asp?newsletter=Oct10

I was an expert witness once on a deck failure (upper level deck) ... the party instantly went from fun walking around with beers to scary to some injuries ... gladly, however, there were no deaths (that I recall). (I reserved further details as to not invade privacy - since it was here in lil' old Pullman.) The deck failed as a result of nails loaded in withdrawal in end grain ... CODE VIOLATION!!! (NDS 11.2.3.2) ... (They pulled out!)

Doc

Slump Test ...

2010-10-18T17:09:00.000-07:00

Here is a slump test we did in the Spring over at UI. On this test the cone was turned over, but it need not be. The concrete was REALLY stiff ... didn't `slump' hardly at all.

This concrete was actually TOO stiff ... causing consolidation problems ... which are evident in the `carmel-corn' look of the concrete where it didn't even consolidate along the sides of the slump cone.

"0-inch Slump" ... actually, maybe it was 1/8th in. or so ...

Solutions ... here they are (for 6)

2010-10-15T17:10:00.000-07:00

My solutions for Assignment 6 ...

Problem 1 ... http://woodengineering.com/edu/wsu/463-563/assn6-prob1.pdf

Problem 2 ... http://woodengineering.com/edu/wsu/463-563/assn6-prob2.pdf

Problem 3 ... http://woodengineering.com/edu/wsu/463-563/assn6-prob3.pdf

Enjoy!

Doc

ANSWERS ...

2010-10-15T16:56:00.000-07:00

Assignment 6 ... this is what I am getting for `answers':

Problem 1

Part 1) ... f = M/S ... S for an uncracked section ... 65 psi due to it's own weight.

Part 2) ... using fr = 7.5 sqrt fc' ... I get 720 lb = Pcr = the concentrated load mid-span (added to the self weight) that will crack open this 9 x 5 beam.

Part 3) ... again using fr = 7.5 sqrt fc' ... I get that it can span a maximum of 15 ft before it cracks open (breaks) under its own weight.

Problem 2 ... this 9 x 5 beam laid flat ... using 0.196 in.^2 for a single #4, and twice that for two ... (all Grade 60 steel)

Mult for 1-#4 and 3000 psi concrete ... is 2700 lb-ft
Mult for 2-#4 and 3000 psi concrete ... is 4900 lb-ft
Mult for 1-#4 and 4000 psi concrete ... is 2800 lb-ft
Mult for 2-#4 and 4000 psi concrete ... is 5100 lb-ft.

So, by doubling the amount of rebar we nearly double the ultimate strength (but not quite).

Increasing the concrete strength doesn't have a strong effect on Mult.

Now for the reinforcing ratios ...

For Gr. 60 and 3000 the max reinforcement (old Code) is 0.0160 ...

and for 60 and 4000 is 0.0210 (old Code). I didn't give you the 4000 value in class, but here it is. Note that it's a bit higher than for 3000 ... which makes sense. It's a bit confusing because it happens to be the balanced amount for 3000 and Gr. 60. Yikes! I didn't plan it that way. The max reinforcement is based on steel yielding before concrete crushes ... so if the concrete is stronger ... we'll allow a bit more steel with higher concrete strength.

Anway ... for the four combinations above I get the following ...

rho for 1-#4 and 3000 psi concrete ... is 0.0073 ... good, good (with regard to greater than min and less than max)
rho for 2-#4 and 3000 psi concrete ... is 0.0145 ... good, good
rho for 1-#4 and 4000 psi concrete ... is 0.0073 again ... good, good
rho for 2-#4 and 4000 psi concrete ... is 0.0145 ... good, good.

Problem 3 ... using the 6 ft span, 1-#4, Concentrated load in center, Strength Design approach with the factors on Ambrose Text p. 377 ... P safe (flexure) is about 900 lb (3 linebackers from the football team).

Perhaps I'll post the blow-by-blow solution ... or perhaps not.

Safe Load based on SHEAR ...

2010-10-15T10:38:00.000-07:00

Students, this is wild! Below is a scan of the calculation of the Safe load P based on Shear for this beam we have been `examining' in class. Note that even though, theoretically, the beam will fail (completely) in flexure, before it (ever) shears, the calculated Safe load P based on shear is LESS than the Safe load based on flexure. Why?!!! ... the `phi' values! There is more UNCERTAINTY in shear failure than in steel in flexural tension. Enjoy! Wrestle with it until it makes sense.

...

LTB ... Better Pic

2010-10-15T09:52:00.000-07:00

Here is a better pic of the (laterally unsupported) beam beginning to fail ... the video in the earlier post shows the `catastrophic' conclusion.

The load is downward from the `blue thing' (the load cell) but the failure is sideways.

LTB Beam Starting to Buckle ...

2010-10-13T16:58:00.000-07:00

I couldn't find the still pic for the lateral movement of the beam - so here we can see it in a video.

...

Concrete Beam in LTB ...

2010-10-13T12:43:00.000-07:00

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Here is a concrete beam failing in LTB (lateral torsional buckling). The beam had a lot of reinforcement (maybe too much), plus there were consolidation problems (voids in the compression zone concrete thus overloading the remaining concrete), plus the rebar was reportedly off center. The result was that the compression zone on top became too heavily loaded and unstable - and buckled lateral-torsional-ly (the top buckling sideways and twisting) ... and ended up on the floor. It's hard to see in the video but the beam is loaded vertically but starting to bend horizontally (laterally) ... (away from the camera). At a certain point the overloaded concrete crushes - can carry no more load - the nearby concrete trying to carry the load - but cannot - CRASH!

The Code makes sure this doesn't happen by putting UPPER limits on the tension reinforcement.

By placing upper limits on tension reinforcement the Code makes beam be not as strong - but way safer!

(I love the girl-student laugh in the video.)

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Reinforced Concrete Beam in Flexure

2010-10-13T12:34:00.001-07:00

Here is a pic of a reinforced concrete beam in flexure. The steel has yielded and the beam is deforming significantly. The blue thing is a load cell device that applies the concentrated load mid-span.

Properly Proportioned Reinforced Beam

2010-10-13T12:31:00.000-07:00

... here is probably a properly proportioned reinforced beam ... the steel has yielded but the concrete is not yet crushing. This is the intent of the Code - to yield the steel at failure without crushing concrete. The beam will simply become more and more bent (deformed).

Beam in Service Condition

2010-10-13T12:28:00.000-07:00

Here is a side view of a beam - like the ones we have been describing in class. If you look close - right in the center - there is a vertical hairline crack. The crack is tight - meaning the steel has not yielded. This is probably in or near in the `safe service load' range for the beam. In other words - we expect (hairline) cracks in our beams in service. But when the cracks start to open up - the steel has yielded - the loads are excessive - the beam is failing - we best leave the building.

Plain Concrete Beam - BROKEN

2010-10-13T12:23:00.000-07:00

... here is a beam, broken. It was made of plain concrete. We loaded it like we have been talking about in class. Without warning - BANG! ... two pieces on the floor.

Maybe I’ll find a video of a plain concrete beam breaking – most of the time, however, the failure is so `without warning’ – and at such low load level - that no one gets it (the failure) on camera.

Concrete TERMINOLOGY

2010-10-12T15:18:00.000-07:00

Here is a list of terms using concrete construction ... every term you ever imagined, and them some: ...

http://www.concrete.org/Technical/CCT/FlashHelp/ACI_Concrete_Terminology.pdf

And this list might not even be complete. I bookmarked it - instead of printing it out.

Doc

Concrete I Beams in Bridge

2010-10-11T17:01:00.000-07:00

Hey - at lunch I snapped some pics of the Concrete I-beam girders in the bridge down the hill. My guess is that they are pre-cast and likely pre-stressed. We'll talk a bit about them in lecture in the next day or two - and I am having a rep from a prestress/precast company come down and talk to us in November.

Also notice the diagonal (transverse) stiffeners - that appear to be cast into the girders once they were `dropped' in place.

Fiber Reinforced Concrete

2010-10-06T16:21:00.000-07:00

... today I mentioned concrete reinforced with `fibers'. Generally these are small (very small, even hair-like) fibers, say of some synthetic. We have also talked about reinforcing `bars' ... a.k.a. steel reinforcing bars. Generally fibers are NOT used for tension reinforcement - say, in the tension zone of a beam. Instead, they find common use in slabs, for example, to help control shrinkage and other cracking. Bars (rebar) are used for both tension reinforcement and shrinkage and cracking control. We have talked already about using rebar for temperature and shrinkage control ... the rho = 0.0018 thing. We'll talk more about rebar used as tension reinforcement in the next several lectures.

Continuous Framing ... Continued.

2010-10-06T14:37:00.000-07:00

7. Now look at p. 113 in Ambrose ... note that the max moments are about 0.10wL^2 ... a bit less than the two span case.

8. And now look below ... I re-sketch the 3-span case on p. 113 but add the deflection ... max delf = 0.0069 wL^4 / EI ... (or 0.0069 WL^3 / EI where W = wL).

For the most part you will have your engineers actually crunching the numbers. What I want you to see is that for continuous framing the deflections will be way less - and long spans are generally controlled by deflections ... AND ... the moments will be in the range of wL^2/10 and the deflections in the range of wL^4/(160 or so)EI.

Continuous Framing ... Beam Diagrams

2010-10-06T14:22:00.000-07:00

Okay - I really want to make sure of two things: first, that you all have beam diagrams for the case of `two-span continous'. I can't seem to ever find it your previous course text, so here it is:

And, second, I want you to observe-wrestle with some things ... as you compare/contrast this with two simple beams (Ambrose Case 2 p. 94):

1. Note that the maximum moment in each case is wL^2/8 ... but for the two-span case it is `tension on top' over the support. That is what motivates the `balanced' layup for glulam beams and the `rebar on top' for concrete beams - that we talked about in class.

2. Note that the center support reaction is 10/8 wL ... instead of 2 x 1/2 wL from the adjacent spans. The center support takes on MORE reaction in the continuous case ... 25% more. So, the continuous beam will make a difference for the foundation design; the end piers will carry a bit less ... and the center a bit more.

3. The deflection is way different for the continuous framing ... 5/384 vs 1/185. In terms of numbers ... 5/384 = 0.013 ... and 1/185 = 0.005 ... that means that even though the moment is the same (two simples vs two-span cont.) ... the deflection of the simple case is more than ~~three~~ two times more than the continuous framing case.

4. Continuous framing is nice because it `ties' everything together better (wind, seismic).

5. If you choose to use two simple beams butted to one another at the center support - make sure your connection hardware handles it. The hardware may assume the beam passes continuously through.

6. Make sure you are clear on the diagrams which `load' is being used. On Ambrose p. 94 the right hand cases use the whole load W. In my diagram (above) I use the distributed load w. On p. 113 Ambrose uses w.

(To be continued.)

Braced Wall Panels, etc.

2010-10-04T18:35:00.000-07:00

In class we have now talked about Braced Wall Panels (BWPs) and Shear Walls. Recall in class that BWPs must be 48 in. in length, min. There is a thing called an Alternate Braced Wall Panel, that I didn't talk about, that may be as short as 2'-8". (But, remember, I covered myself by saying there were `exceptions' to what I was telling you.) ANYWAY, I often, and so will you, run into situations where there just isn't 48 available ... (and maybe not 2-8). Presenting the Simpson StrongTie Strong Wall. These are pre-manufactured CODE APPROVED `braced wall panels' or shear walls. With regard to Rx (prescriptive) construction they may be used in place of BWPs ... the nice thing being that there are `shorter' ones ... we can use them in spaces narrower than 48 in.

Here is some literature ... http://www.strongtie.com/products/strongwall/steel-strongwall/index.asp

Here is the Code Report ... http://www.icc-es.org/reports/pdf_files/ICC-ES/esr-1679.pdf

Doc

4. BEAMS ... and ... 5. COLUMNS

2010-09-30T15:35:00.001-07:00

4. BEAM(S) …

Let’s use the American Institute of Timber Construction stuff: www.aitc-glulam.org … TECHNICAL INFORMATION TAB, Douglas Fir – Larch, Roof Beams Snow Load … we get a table that gives us uniform line load capacities for various size beams for various spans. For our deck we have two spans of 12 ft each.

From before  we found our `line load’ on the outer rim to be 1020 plf.

From the AITC Table DF-26 we find that the 3-1/8 x 13.5 will work … and also the 5-1/8 x 10.5. Since we have joists that are 12 in. (nominal) deep (11.25 in. actual) it would look strange to use a beam that is not as deep as the joists, so let’s use the … 5-1/8 x 10.5. The 3-1/8 x 13.5 would work structurally, but since we are going to use 6 x 6 posts, let’s get a beam to match post thickness, or close thereto.

Note that is says the beam weighs 14.9 plf. We could add this to 1020 to get 1035 plf … and we’re still good. We could incorporate this into our pier footing design, though at the time I assumed the deck weight included the beam weight. Even if we now decide to include (deliberately add) the weight of the beam, I’ll bet the footing sizes don’t change – since we rounded to even inch footing sizes anyway.

5. COLUMNS …

We could go to the website indicated in the Assignment, but since we’re here at the AITC site … let’s go on over to the Column Capacity Tables, Douglas Fir – Larch, Column Table, Duration of Load 1.15 (Snow) ...

Earlier we said the heights of the columns may be as much as 6 ft.

Go with a 5-1/8 x 6, 6 ft; we get a capacity of 30,610 lb. From before, our loads were about 6 k at the corners and 12 k at the interior column … so, since 6 k and 12 k ≤ 30.6 k … WAY GOOD!

6. HARDWARE … Code Approved Column Cap and Column or Post Base hardware appropriate for the conditions installed in accordance with Manufacturer recommendations and requirements, blah, blah … we already talked about.

7. PIERS AND FOOTINGS … we already talked about … and if you go back through the Blog I think you’ll find that we’ll need 12 in. diameter piers to accommodate the requirements of the connection hardware.

3. DECK JOISTS …

2010-09-30T13:38:00.000-07:00

FOR THE JOISTS FOR THE DECK ...

… wood design is pretty complicated with all of the Adjustment factors, so …

Going to the link provided in the `Assignment’ …

http://www.awc.org/calculators/span/calc/timbercalcstyle.asp

Species: DF-L (Douglas Fir – Larch) … because that’s what’s commonly used in the area.

Size: try 2 x 12

Grade: try No. 2

Member Type: use Roof Joists (Rafters) … so we can apply `snow’ (you’ll see)

Deflection Limit: use L/180 … we’re not worried about cracking any sheetrock or windows

Spacing: try 12 in. o.c.

Wet Service: I am going to put in `no’ … since when all that snow is on there – it will be very cold and dry; you can argue differently if you wish.

Incised Lumber: no! … I am not going to use Pres. Treated lumber, so it will not be incised.

Snow load: I will use an average of 240 at one end and 120 at the other end giving me 180 psf and treat it as a uniform load. (And I will try and defend this in an appendix or something.)

Dead load: use 10 psf

Then I hit the Calculate Maximum Horizontal Span button and … it shows: 11 ft 6 in.

If my deck is 12’-0” from concrete wall to outside of far end support beam, assuming a nominal 6 in. wide support beam … the span will be about 11’-6” … so we could probably barely make this work. But I think I’ll knock it up a Grade to No. 1 … this gives me 12 ft 1 in. YAY! Let’s go with it! That gives me a little wiggle room if my uniform load assumption was non-conservative.

So,

Joists … 2 x 12 DF-L No. 1 @ 12 in. o.c.

(See printout)

Standard Hook ...

2010-09-27T21:09:00.000-07:00

Okay, the sketch I sent out of the standard (rebar) hook is essentially the same as that on Ambrose p. 430 ... but the context is totally different!!!

So far our use of the standard hook has been as a `dowel' ... basically keeping the pier from sliding relative to the footing. We will see the same thing in a typical foundation wall situation ... rebar used as dowels keeping wall from sliding across footing surface. In the `olden days' concrete keys were cast ... kind of a locking mechanism ... ughhh ... difficult construction.

I labor this because it is the practice of many contractors to simply `stab' straight dowels into the footing, let the concrete set and begin to cure, and then form a wall (or pier) above it, and cast the concrete around the dowels sticking out of the footing. But it is the trend of Building Inspectors to require this dowel to be hooked (not straight) ... and if they consider it a `Standard Hooked Bar' ... then it needs to be in there at least 6 in. ... more for bigger bars.

So, you need to find out what the Building Official is looking for in these dowel situations ... I generally require a hooked bar whether or not the Building Official requires it.

The context of p. 430 is where the hook is used `within' the cast member to develop tension stresses in the steel. When we use it as a dowel - we are only using it in shear across the two (cast - separately) elements.

Doc

Yes, Review on Mon and Exam on Wed ...

2010-09-24T15:28:00.000-07:00

... - yes we will review on Monday 9/27 and Exam on Wed 9/29.

Doc