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  • Users: penpal97
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  1. penpal97

    response modification factor for concrete connection

    I am designing a bridge pier with columns and a cap at the top. The system works as a moment frame during an EQ. I perform an elastic seismic analysis based on the response spectrum to get axial, moment, and shear. Time to design the rebar... The column rebar will be governed by the moment at...
  2. penpal97

    Skewed Bridges

    I have seen a few things to worry about w/ highly skewed bridges (over 30 degrees). One is increased shear on some of the girders, and I can understand that since the load path can be kind of odd given the geometry of the loading relative to the abutment. The other is uplift at the bearings...
  3. penpal97

    Simple beam but large displacements

    I have a simply supported W27x281, 10ft long, 100kip/ft. Basic beam equations give a displacement of 0.065in. I model the beam in STAAD (single element), and get 0.065in. However, once I model the beam as ten 1ft long elements, I get a deflection of 0.109in. Anyone else have this sort of...
  4. penpal97

    Development length of stainless steel rebar

    There is guidance for development lengths of black bars and epoxy coated bars, but what about galvanized and solid stainless steel? Anyone have any thoughts? Is the stainless surface just as slick as the epoxy? or even more smooth?
  5. penpal97

    Simply supported beam/plate

    I have modeled a simply supported beam 10' long, 5kip point/line load at midspan. Midspan moment = 12.5k-ft. For a 1ft thick concrete slab (and assuming no cracking), there should be ~500psi compression on top, ~500psi tension on the bottom. I run the model and good results for principal...
  6. penpal97

    Simply supported beam/plate

    I have modeled a simply supported beam 10' long, 5kip point/line load at midspan. Midspan moment = 12.5k-ft. For a 1ft thick concrete slab (and assuming no cracking), there should be ~500psi compression on top, ~500psi tension on the bottom. I run the model and good results for principal...
  7. penpal97

    Overstrength factor and concrete

    I've read several of the topics on the overstrength factor, but they mostly refer to steel (brittle bolted connections vs ductile connections). How about if I am designing a concrete moment frame for gravity and seismic forces? Overall I divide my seismic forces by R. Given those forces, I...
  8. penpal97

    Intermediate Stiffener Welds

    I am reading "Structural Steel Design: LRFD 3rd Ed" by A. Williams. For design of Plate Girders, Ch 8.4 says intermediate stiffeners (when required, with or without tension field action) must be connected to webs to resist shear given by f_vs = 1.67h(Fy/340)^1.5 Could someone help tell me...
  9. penpal97

    Tack welding rods

    I'm detailing anchor bolts for column base plates. I've got a threaded rod embeded in the concrete footing. For anchorage of the rod, I do not want to bend or hook the rod. 2 questions for everyone... 1 - I've seen an embeded nut, a nut and washer, 2 nuts sandwiching a plate, and 2 nuts with...
  10. penpal97

    Seismic basement pressure

    I'm trying to design a fairly deep basement and I am not quite sure how to design for seismic soil pressure. People have told me Monoabe-Okabe does not apply and I should look at ASCE 4-98 Seismic Analysis of Safety-Related Nuclear Structures, where they use the Wood Elastic Method. The Wood...
  11. penpal97

    HSS Column weepholes

    I have an outdoor 30' tall canopy made of a HSS members, architecturally exposed steel. There is a welded cap plate on the columns, and the welded base plates are embedded in 2' of concrete (architectural curb). Do you usually put a vent hole in the column? I am afraid that the column will...
  12. penpal97

    Is this a moment frame?

    I am designing an ordinary moment frame as defined by AISC 341-05. All beams and braces are pin connections. Please see the attached. Frame A - just an example of a perfectly acceptable moment frame using knee braces. Frame B - Is this allowed to be qualified as an ordinary moment frame? I...
  13. penpal97

    Moment frames

    I am designing an ordinary moment frame as defined by AISC 341-05. All beams and braces are pin connections. Please see the attached. Frame A - just an example of a perfectly acceptable moment frame using knee braces. Frame B - Is this allowed to be qualified as an ordinary moment frame? I...
  14. penpal97

    Steel unbraced lengths

    2 different questions on same topic Lets say I have a typical 2 story building, 4 columns (1 at each corner). There are floor stringers from column to column, floor beams from floor stringer to floor stringer. 1) Is a typical shear connection w/ clip angles of the beam to the stringer enough...
  15. penpal97

    LRFD Foundation Design

    I am designing a bldg according to IBC 2006. I have designed everything up to the foundation using LRFD. Now I am at the foundation, and Section 1804 only allows ASD to check the soil capacity. Is this right? Any ideas how I can move forward besides doing a separate ASD analysis just for the...

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