Uniform Design Load (UDL) Please Explain 1

[FootNMouth]

I am reading "Connection: Art, Science, and Information in the Quest for Economy and Safety" by Dr. William Thornton and he keeps mentioning the UDL. He has an example comparing the total load reactions on the beam to the one-half UDL reaction. Can someone please explain to me how you go about determining the UDL on a beam.

Thanks

 

[BAretired]

UDL = b(D + L) + self weight of beam + superimposed uniform load acting on the beam such as wall or partition.

In the above, b is the width of floor supported, D and L are the dead and live load of the floor specified by code or based on project requirements.

BA

 

[BAretired]

And, by the way UDL stands for uniformly distributed load, not uniform design load. Concentrated loads or variable loads do not contribute to UDL.

BA

 

[sbisteel]

In connection design, the 50% UDL is referring to the end reaction from a uniform load that causes the maximum allowable midspan moment.

i.e. 50%UDL = Wmax * L / 2

Where Mn = Wmax L^2 / 8

 

[cliff234]

I think he is referring to Table 3-6 in the AISC Manual (13th or 14th editions). This table gives the maximum loads that non-composite beams of various spans can support. Many engineers specify that connections be designed to support a percentage of the Table 3-6 loads. A fully loaded (uniform load) non-composite beam would have a reaction at each end equal to half of the Table 3-6 total uniform load. Engineers often require that connections at the ends of composite beams be designed to support anywhere from 75% to 100% of the Table 3-6 loads. This increase (specifying a required connection strength greater than one-half of the uniform load capacity) accounts for the fact that composite beams will support more load than non-composite beams. Unfortunately specifying that connections be designed for a percentage of the Table 3-6 load is usually excessively conservative - but it can also sometimes result in dangerously understrength connections (such as for girders with heavy concentrated loads near one end). The best solution is for engineers to show the actual beam reactions on the framing plans. Showing the actual reactions will allow the fabricator's connection design engineer to design a connection for the exact reactions on the beam.

 

[FootNMouth]

Thanks for the responses. He was referring to Table 3-6 in the AISC Manual.
BAretired, I understand that UDL typically stands for uniformly distributed load however in his article Dr.Thornton specifically refer to UDL as the uniform design load, which is why I was wondering if it meant something else.