Are you operating under an "existing" building code, like IEBC? IEBC permits a 5% stress increase in existing structural elements before strengthening is required. Are you using ASD or LRFD? Depending on the live-to-dead load ratio, use of one (or the other) might result in a 4% capacity increase.
Using the equations in the Guide, I ran the numbers for an L5x3-1/2x1/4 and L6x4x3/8 and got negative values for βw. In an absolute value sense, the computed βw values for the L5x3-1/2x1/4 and L6x4x3/8 cases are 2.46" and 3.15", respectively. These compare closely to the values published in...
Equations are provided in Figure 11.7 of Guide to Stability Design Criteria for Metal Structures, sixth edition. It is Figure 11.5 in the fifth edition of the same text.
Is encasing some length of the existing HSS8x8 steel column in concrete (a cylindrical cross-section) an option? The length and diameter of the encasement would be determined from a stepped-column analysis. How many columns are we talking about? Have you investigated filling the extended HSS...
With a free-standing (or cantilever) exterior wall, the proportions of the continuous wall footing must be sized to keep the maximum bearing pressure within the allowable limit and provide an adequate factor of safety against overturning and sliding. With wind load on the wall, you will have a...
If it is information you can share, I would be very interested to know how this situation came about. Is this a design issue? If so, what was the root cause? How was it discovered? I would think there are multiple 'lessons learned' here for the Engineer of Record and his/her employer.
Do your manual computation of WA, WB, WC, ZA, ZB, and ZC agree with the values in the AISC Shapes Database? Those values are based are measured from the major and minor principal axes to the tip of each leg (centerline of tip) and to the corner of the heel. If the manual computations for IW and...
msquared48: do the VH-series joists have their own SJI specification in the 1979 Vulcraft manual or are they covered by the H-series (or some other) specification? This is the first I have ever heard of VH-series open-web steel joists. They are not included in the 60-year SJI manual, unless they...
Is the existing slab experiencing any visible distress? Are you increasing the total design load on the slab? Are other trades cutting holes or otherwise adding penetrations to the existing slab? Is the 10mmm cover taken from original construction drawings or an in situ measurement? If the...
Are the beams in question composite? Using 50% of the tabulated UDL can be unconservative for composite beams. I have seen engineers specify 60% of UDL for the shear connection at each end of composite beams.
Since the member in question is a closed tube (round HSS or pipe) and therefore the applied torsion will generate only shear stresses, I would say 0.5Fy does not provide a factor of safety equal to 2.0. The shear yield for most structural steel material is Fy/√3, or 0.577Fy, which most...
AISC 360-16 Section B4.1b.(d) specifies that for local buckling of HSS members, 'b' and 'h' shall be taken as the outside dimension minus 3t, if the corner radius is not known. That implies an outside corner radius equal to 1.5t, where 't' is the design wall thickness.
There is an error in the elastic shear flow equation provided in the July 2014 Steel Interchange response. The equation should have a 'd/2' term in the numerator. The omission has been confirmed by AISC. The other terms in the equation are correct. The shear flow assuming a plastic bending...
If you are practicing in the United States and we are talking about a building application, ASTM A500 Grade C is the most common material for hollow, round steel members. Every once in a while I get a request from a contractor to substitute ASTM A53 Grade B and will gladly evaluate it on a...
If the load is continuous (along the length of the beam) and supported only by the flange, the approach suggested by JoelTXCive is reasonable. If the load is continuous across the flange width, the typical assumption is that the load goes directly into the web of the beam since that is much...
The "R" factor in Blodgett is equivalent to the torsional constant ("J") in AISC. The polar moment of inertia being equal to Ix + Iy is covered in most Mechanics of Materials textbooks. It can also be seen in AISC 360-16 Eq. (E4-2) where the denominator of the (1/Ix + Iy) term is the polar...
This appears to be a typo in the graphic portion of Figure 27.3-7. To the best of my knowledge, the ASCE 7 approach is to consider 'B' to be perpendicular to the direction of wind and 'L' to be parallel to the direction of wind. I believe the written definition of 'L' is correct.
Yes. The likely controlling load combination is 0.9D+1.0W (LRFD) or 0.6D+0.6W (ASD). You may need to include ice loads, depending on the location of the sign. The load combinations get modified a bit, per Chapter 2, if you include atmospheric ice.
I am not aware that ASCE 7-10 (or any other edition of ASCE 7) requires the concurrent application of wind loads in orthogonal directions when the element in question is a MWFRS element in one direction and a C&C element in the other. ASCE 7-10 does require the concurrent application of wind...
