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  • Users: DCBII
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  1. DCBII

    Contractor Cut Through Diaphragm Chord

    I have a 1-story Special Reinforced Masonry Shear Wall building where the electrical contractor cut through the diaphragm chord reinforcement multiple times to make openings for conduit. Looking for ideas on how to repair this. The chord steel also acts as horizontal reinforcement for the shear...
  2. DCBII

    Existing Corbel

    I've got a situation where I'm being asked to expand an existing structure. The existing structure was built with a corbel to plan for future expansion. The only problem is, the existing corbel is not detailed correctly. The anchor bar is not welded, and the ties do next extend 2/3*d down the...
  3. DCBII

    Gabled Roof Thrust

    I'm working on a steel gabled roof design (see attached layout). At the ridge line there are steel ridge beams supported by steel columns. I did that to eliminate/reduce the thrust applied by the roof beams to the exterior CMU walls. I have an attic that acts as a rigid diaphragm (concrete over...
  4. DCBII

    Soil Seismic Load Questions

    Consider a multistory structure with a basement. Assume the geotechnical engineer has given you a soil seismic load against the basement wall. That soil seismic load is resisted largely by the ground floor diaphragm at the top of the basement wall, which carries it out to the basement shear...
  5. DCBII

    Beam Over CMU Non-Bearing Wall

    I have a CMU partition wall with wide flange roof beams over it. The CMU is notched around the roof beams so they can pass over the wall without bearing on it. I need to seal off the spaces on each side of the wall from each other. How do I seal off the pockets around the beam? I can't use...
  6. DCBII

    MITC4 Plate Bending Elements

    I'm a full time engineer, but I've put together a sort of hobby computer program that does basic finite element analysis to help me learn how it works. I've been trying to add MITC4 elements for linear analysis (nothing too fancy) but I'm having some trouble. This is my first time creating...
  7. DCBII

    Post-Installed CMU Anchors

    I'm working on a project where we have some embed plates in a masonry wall used to tie back a 7.5 ton class C crane. The contractor did not install the embeds. I know there are some options for post-installed CMU anchors, but to my knowledge none of these are approved for use in cracked masonry...
  8. DCBII

    Concrete Joint Spacing

    There have been several discussions related to this, but they seem to be targeted to very specific situations. I want to have a more general discussion with other engineers on this. Thanks for your thoughts in advance. Q1: For conventionally reinforced slabs/mats (water-bearing - or not if...
  9. DCBII

    Slip-Critical Connections in Seismic Regions

    AISC 341 requires connections in the seismic force resisting system (SFRS) to be detailed as slip-critical if R>3. I've traditionally thought of a seismic force resisting system as a SMF, SCBF, BRBF, etc, including anything like collectors directly attached to the system. I've always used...
  10. DCBII

    Shear Friction Development (Rehashed)

    Thoughts I've been pondering: 1. Shear-friction reinforcement must be developed for fy on both sides of a shear plane. 2. Minimum bar cover in CMU is typically 2.25" (1.25" face shell + 1/2" grout space). 3. Minimum development lengths for Grade 60 bars in CMU are as follows (f'm = 2000 psi...
  11. DCBII

    CMU Gable Wall Diaphragm Shear Connection

    I need ideas for a detail to transfer diaphragm shear from a steel roof deck into a gable end CMU wall. The deck will sit on open web steel joists running parallel to the gable end wall, so it will be 4 to 8 inches higher than the top of the wall. I was thinking of something like this sketch...
  12. DCBII

    Masonry Shear Wall Flanges

    I'm doing low-rise masonry shear walls in seismic design category D. There are several piers in each line of resistance, and some of them have flanges due to intersecting walls. What's the industry doing out there to account for the flanges? Do you place joints to isolate intersecting walls from...
  13. DCBII

    CMU Wall Anchorage

    Our plans show embed plates on top of a CMU wall for steel joists to bear on. The contractor grossly mislocated the embeds. To make matters worse, I've gone through the original engineer's calculations, and they used an incorrect wall tributary weight to each embed, so they were slightly...
  14. DCBII

    Modifications to Existing Wall

    An important client has a 100' long wastewater retaining structure that isn't ready for an earthquake. The vertical bars are too small, the wall doesn't have enough shear strength, and the strip footing can't handle the overturning load. He can't afford to do any retrofits. It's not in the scope...
  15. DCBII

    Seismic Pile Cap Connection

    I'm reading the 2015 IBC Section 1810.3.11.2 which states: "For structures assigned to Seismic Design Category D, E or F, deep foundation element resistance to uplift forces or rotational restraint shall be provided by anchorage into the pile cap, designed considering the combined effect of...
  16. DCBII

    Continuous Cross-Ties in Gabled Roof

    I have a gabled roof diaphragm with a 30 deg slope and a ridge beam down the center. I've calculated my wall anchorage force, and I'm designing the roof joists as continuous cross-ties for the diaphragm. I'm looking at a free body diagram of the roof joist/cross-tie under the wall anchorage...
  17. DCBII

    Masonry Wall Anchorage

    I'm anchoring a masonry wall to a flexible diaphragm. I've calculated the anchorage force per ASCE 7-10 Section 12.11.2.1 as 0.4SDSIekaWp = 5.4 kip. If these were concrete anchors, ACI would require either: (1) a ductile failure mechanism, or (2) design for the amplified seismic load (a.k.a...
  18. DCBII

    Dovetail Slot for Masonry Veneer

    Our specs call for 18 ga. dovetail slots for anchoring a CMU veneer with dovetail anchors. The contractor wants to use 22 ga. dovetail slots because they are locally available. I don't see any problems with this. It seems like any tensile anchor loads applied to the slot will bear on the...
  19. DCBII

    Circular Tank Control Joints

    Our office has designed a 75' diameter circular concrete tank to ACI 350-06. In the mat foundation slab we have called for a circular control joint with a diameter of 32'. (8) radial control joints start at this circular joint and extend to the perimeter of the foundation. The contractor is...
  20. DCBII

    Rebar Lap Splice Locations

    I was told I should not splice rebar in a flexural member near the point of maximum moment. I can't seem to find anything to back that up in ACI 318 though. The closest thing I found is limitations with regard to splicing integrity reinforcement in perimeter beams. Thoughts?

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