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  1. dengebre

    Concrete Cover for Residential Driveway Slab

    I have a residential project that includes a concrete driveway. The minimum thickness for a slab-on-grade according to the Florida Building Code is 3.50” and most residential slabs are 4” thick. Welded wire fabric (e.g., 6x6-W2.9xW2.9) is often used for crack control. According to ACI 318...
  2. dengebre

    Load Sharing of Multi-Ply Wood Plates

    In order for multi-ply wood plates (oriented flat-wise) to behave as a single unit, they must be sufficiently fastened in order to transfer the stress across the shear plane (a shear flow calculation). However, sometimes the amount of fasteners required can be problematic. Is it acceptable to...
  3. dengebre

    Continuity of Wall Segments in Wood Shear Walls

    I have a wood-framed apartment project where the framer wants to construct the shear walls in segments, and sheath them on the ground before lifting them in place. This introduces vertical seams into the shear wall. I understand that each wall segment will require an end stud and that the...
  4. dengebre

    Stagger Panel Edges at Wood Shear Walls?

    For wood shear walls sheathed with wood panels, does it matter which direction the panels span over the wall studs, or if adjoining edges are staggered? The SDPWS differentiates between different cases for wood diaphragms, but I cannot find anything for shear walls.
  5. dengebre

    Tendon Bend Radius in Vertical Plane

    I am looking for the minimum bend radius in the VERTICAL plane of a 1/2" diameter unbonded tendon using a parabolic profile. The available literature discusses the minimum radius of sweeps in the horizontal plane, but I cannot find anything for the vertical plane. The following is what I have...
  6. dengebre

    A Question for Miami-Dade Engineers

    This question is specifically for structural engineers in Miami-Dade County, Florida: I have always put the following wind load information on my structural drawings: Design Wind Speed, Risk Category, Exposure Category, the C&C Design Pressures (positive and negative pressures for Zones 1-5)...
  7. dengebre

    Expansion Joints in Big Box Buildings

    We have a single-story “big box” project in Florida that is 480’ x 160’. It was originally an all-steel building, with steel stud exterior walls, and using the Thermal Program (steeltools.org) it shows that an expansion joint is not required (Delta-T = 55 degrees). The project has changed to...
  8. dengebre

    Design of Heavy Loaded SOG

    We have been asked to design a large shipping container warehouse where the floor live load is 2,500 psf (specified by the user client). The SOG will be supported on soil that will be improved by stone columns (subgrade modulus = 100 pci after improvement). That design load is off the charts of...
  9. dengebre

    Do Double Wood Top Plates Work?

    For multi-story wood buildings, I have very often seen the wall studs spaced at 16” o.c. and the trusses spaced at 24” o.c. The trusses bear on a double top plate across the top of the wall studs. This typical configuration will result in every other truss bearing at midspan between the wall...
  10. dengebre

    Does CMU Wall Brace Concrete Tie Column?

    I have a project with numerous concrete columns that are cast within the plane of concrete masonry walls (a/k/a concrete “tie columns”). The walls and columns are supported only at the floors above and below. The column and walls are 7-5/8” thick and the column widths range from 16”-32”. Does...
  11. dengebre

    Stress Limits for PT Transfer Girders

    We are designing a concrete high-rise building that includes post-tensioned transfer girders supporting multiple levels. Our standard is to design PT beams with a maximum precompression of 350 psi and as Class U (ft <= 7.5sqrt[f'c]). Is this too conservative for a transfer girder? In particular...
  12. dengebre

    Hollowcore vs. CMU Arching Action

    This question pertains to the design of lintels in CMU loadbearing walls that support precast hollowcore panels in multi-story buildings (i.e., “block & plank” buildings). It is common knowledge that lintels can be designed for only the loads within the triangular area below the apex so long as...
  13. dengebre

    Fire Truck Surcharge on Cantilevered Retaining Walls

    We are designing several tall cantilevered retaining walls that range from 8’-0” to 16’-0” of retained soil. The walls are subject to a traffic surcharge load as there is a parking lot within several feet of the walls. In the past we used a surcharge of 250 psf and believed this adequately...
  14. dengebre

    Wood Roof Diaphragm to Bond Beam Connection

    Walls constructed of CMU supporting wood-framed roofs is common. The roofs are often sloped, have an overhang, and the roof diaphragms can be large for buildings such as assisted living facilities. SDPWS states that “diaphragm boundary elements shall be provided [and]… diaphragm chords and...
  15. dengebre

    PT Tendon Bundles in Transfer Girders

    We are currently designing some long span transfer girders that require a significant amount of 1/2" unbonded tendons. We typically use rectangular tendon bundles that are six tendons wide, and this results in a large number of bundles. Is there a maximum number of tendons per bundle? Is there a...
  16. dengebre

    Pile Cap Design Software

    I am looking for a good pilecap design program and was wondering if anyone had any recommendations. I would prefer a program that uses a FEM solution to determine the pile cap forces, pile reactions, design the reinforcement, etc. Thank you in advance for your advice.
  17. dengebre

    Seismic Overstrength Factor for Foundation Design?

    Should the seismic overstrength factor (Omega) be used when determining the foundation design loads? I am specifically referring to the loads as they pertain to the soil-foundation interface, and not the design of the foundation itself.
  18. dengebre

    Seismic Overstrength Factor for Foundations?

    Should the seismic overstrength factor (Omega) be used when determining the foundation design loads? I am specifically referring to the loads as they pertain to the soil-foundation interface, and not the design of the foundation itself.
  19. dengebre

    Cracked MOI for PT Slabs

    ACI 318-05 [10.11.1] allows the use of the reduction factor 0.25Ig for estimating the cracked MOI for concrete flat plates. However, that is not for prestressed flat plates. Assuming a minimum precompression of 125 psi, would not the cracked MOI be something higher than 0.25Ig? If so, what would...
  20. dengebre

    Reinforcement of CMU Wall (after the fact)

    We have a renovation project where we need to reinforce an excisting 8" CMU wall in order to bring it up to Code. The existing wall has minimal vertical reinforcement (if any) and a 1-2 course bond beam across the top. This will be an obvious constructability issue. Has anyone run into this...

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