Selecting a Suitable S275 Steel Universal Beam Section

[thebest99]

steel floor beams span 7.0m and are at 4.2m spacing. the beams are fully laterally restrained by precast concrete floor slabs, 180mm thick, which they support. the floor has to support a speciified imposed load of 5.0 kNm-2.

determine a suitable grade S275 steel universal beam section

From what i have worked out so far:

imposed load = 5.0kNm-2 x 4.2m
=21kN/m

dead load = 4.2m x 0.18m x 24kN/m3
=18.14kN/m
to select a suitable UB section:
214x1.6x7+18.14x1.4x7
=413kN

design shear force:
413/2= 206.5

desing BM:
m=wl sqaured / 8 =

18.14x1.4+21x1.6 x 7sqaured / 8 = 361.4

section selection:
S=m/py

=361.4/275

=1314cm cubed

this is where I am lost need to find UB with plastic section modulus

do i use UB 406 x 178 x 67

if somone could help me with this question and make sure I am doing this example right

thank you

 

[nvn]

thebest99: I currently think your answer looks correct.

 

[pongo38]

I don't see where you have taken account of the self-weight of the steel beam (small as it is).

 

[nvn]

Good catch, pongo38.

 

[DeeNos]

I would first like to commend you for your detailed calculations and effort in selecting a suitable UB section for this project. Your approach seems to be correct so far, and I will provide some additional information to help you complete the selection process.

To determine the plastic section modulus, you can use the formula Zpl = (Iy * fy) / Mpl, where Iy is the second moment of area, fy is the yield strength of the steel, and Mpl is the plastic moment capacity of the section. In this case, the plastic moment capacity can be calculated as Mpl = fy * Wpl, where Wpl is the plastic section modulus.

To find the UB section with the required plastic section modulus, you can use a steel section database or design software. For example, using the British Steel Sections software, a UB 406 x 178 x 67 section has a plastic section modulus of 1314 cm3, which meets your requirement. This section also has a yield strength of 275 MPa, making it suitable for the specified load and conditions.

In conclusion, the UB 406 x 178 x 67 section would be a suitable choice for this project based on your calculations and the plastic section modulus requirement. I hope this helps in completing your selection process.