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  1. dbnerds

    Slab-On-Grade - Parallel-to-Cut Cracks

    appreciate the feedback everyone. Seems the favored verdict is that the cutting happened too late. That would makes sense. However, there is an curveball to that theory. The majority of these cracks occured parallel to the long axis of the plate. These cracks are adjacent to the FIRST...
  2. dbnerds

    Slab-On-Grade - Parallel-to-Cut Cracks

    answers to some questions posed: -w/c = 0.45 -environment was idea: low breeze, 60's -base was ideal: subgrade had been conditioned with a lime mix, and the concrete was pumped in (hence trucks never touched the subbase) -when did curing start? meaning? -was the pour complete? meaning had all...
  3. dbnerds

    Slab-On-Grade - Parallel-to-Cut Cracks

    I should add, saw cut depth was approx 2" deep.
  4. dbnerds

    Slab-On-Grade - Parallel-to-Cut Cracks

    I have an incident of a slab-on-grade that has been placed that is exhibiting cracks in a pattern that I have not witnessed before and was hoping I could get some feedback/ideas from all here. Below is the conditions: -6" slab on grade, 4000 mix, reinforced with WWR 6x6-W2.9xW2.9 -two "plates"...
  5. dbnerds

    MBS Foundation - Large thrusts without tie-beams or hairpins

    @AELLC - At this proposal stage, I don't have any info on passive pressure, only bearing (which I can quasi-translate to coefficient of friction, using reco's from IBC). I've read that you shouldn't try to utilize friction and passive at the same time. @hokie66 - Bored piles sounds...
  6. dbnerds

    MBS Foundation - Large thrusts without tie-beams or hairpins

    I'm currently designing a proposal for a client. Its a MBS with a (3)100'span (300' wide building) and frames are at 40'oc. As you can imagine the loads are considerable. The client GA drawings require us to avoiding tie-beams or hairpins. In addition no slab will be installed until the...
  7. dbnerds

    Impact (Dancing) Loading on Timber Design

    Woodman, you may misunderstand my 1.5 factor. Its a mix of two concepts: -it utilizes the 2.0 Cd (for impact) -then lowers it a bit to take into the unliklihood of one structural element getting full on impact its entire length (similar to Live Load reduction) or you can also look at it like...
  8. dbnerds

    Impact (Dancing) Loading on Timber Design

    WikiEngineer is new to me, thanks Woodman. I've suggested a factor of 1.5 to the owner. The dancing load (at least each little impact) is to seismic and wind in duration, but I'm also trying to factor in the low chances that adjacent people's impacts (i.e. all parishioner's dancing along one...
  9. dbnerds

    Impact (Dancing) Loading on Timber Design

    shobroco is in line with my thoughts on the situation. if you follow his math, with 60 ppl in that room -- they each have 5sf to occupy. it won't happen. i think most ppl here are getting caught up on the words "church" and "dancing". this scenario is similar words/terms to those only...
  10. dbnerds

    Impact (Dancing) Loading on Timber Design

    I appreciate all the feedback everyone. FYI, secondary = timber 2x12, 16"oc, spanning 17' primary = hot rolled W10x30, multiple/cont spans of 15' congregation max = 20 ppl As you can see, this is a small group of people worshiping, in a private (not public) setting. Its hard to call this a...
  11. dbnerds

    Impact (Dancing) Loading on Timber Design

    BAretired: Is your information your purely personal opinion, or do you have some information you're quoting?
  12. dbnerds

    Impact (Dancing) Loading on Timber Design

    I have a liturgical client who occupies a large house of timber construction. He is requesting an analysis of the live load floor capacity. He shared that his congregation may occasionally dance and/or jump a bit. I should add that this congregation is small - occupying a room approx. 15'x20'...
  13. dbnerds

    Existing CECO Joists?

    I am currently working on analyzing an existing roof structure for a possible new fall protection system. I was able to pull off one of the existing joist tags, and it read the following: 54 256 J15 The CECO Corp. I have been unable to find anything on the inter-webs, about CECO or this...
  14. dbnerds

    A307 vs. F1554-36 -- AISC vs. ACI

    Was reading my AISC incorrectly, results should be: ACI -- 13.7kips AISC -- 15.9kips still a bit of a difference.
  15. dbnerds

    A307 vs. F1554-36 -- AISC vs. ACI

    A co-worker used Apendix D to figure the shear of an F1554-36 1"diam. anchor rod (13.7kips) . I used the single shear value of an A307 in the AISC tables (9.42kips). I realize that these anchors aren't technically the same, but for this shear/structural discussion should we be getting the...
  16. dbnerds

    Contribution of Roof Ballast to Effective Seismic Weight

    Sometimes (way too often) the code doesn't cover some subject matter and you have to use engineering judgement (theoretical as you said). If the snow was discounted for "statistical probability" purposes we should be looking at load combinations, not the discount of the load itself, depending...
  17. dbnerds

    Contribution of Roof Ballast to Effective Seismic Weight

    @JAE good question about how much do you discount. Lets look at definition of Effective Seismic Weight inclusions -- like the snow one. (I'm quoting AISC) ..if snow load > 30 psf, then 20% of that load can be considered part of the effective snow load. I would argue that the reasoning of that...
  18. dbnerds

    Contribution of Roof Ballast to Effective Seismic Weight

    Friendly debate in our structural design group: Do you consider roof ballast as part of the Effective Seismic Weight? -some say yes, since it IS a dead load and their are no caveats/exclusions for it per code. -some say "maybe not" since it may act like ball bearings (i.e. not stay put in their...
  19. dbnerds

    ASCE 7-10, MWFRS Wall Loads on OPEN building?

    Great feedback guys. Mark, your method/model makes sense. However, I feel the thin/planar sign may not develop the same leeward forces as the depth of a full building. ajh1, I like your method too. I like that its at least mentioned within the body of a section where this formula should be...
  20. dbnerds

    ASCE 7-10, MWFRS Wall Loads on OPEN building?

    This may seem like an oxymoron (wall wind loads on an open building), but sometimes this can occur. I would like to understand which equations to use for elements and system using for MWFRS? (btw, I'm using Directional - Part 1) Section 27.4.3 "Open Buildings with ..." sounds like the right...

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