Superdead ??? Reduced Live Loads 1

[JIGSAWU]

What's the use of these two specific loads?Can anyone give an example for each case?Thanks in advance...

 

[chiefchester]

I'm not a pro but I think I can take a stab at answering your question.

Superimposed dead load is different from dead load in that it is not attached to the building, it is not structural dead load. DL would be the beam and column weights and the architectural facade weight and SDL would be partition weight and ceiling weight. ETABS breaks the two load cases apart because you may want to apply them separately.

I believe the difference between LL and RLL is that load placed in the RLL will be reduced (that seems obvious). If you have LL that you do not reduced, put it in the LL case. I am assuming that you know what it means to reduce live load, if not ASCE 7 should discuss that topic somewhere. RLL is also discuss in this forum, I remember reading about it.

Experts, feel free to correct me if I am in error. Good Luck.

 

[slickdeals]

Be sure to choose reduced live load under the options for load type. If not, then the program will not reduce these live loads.

 

[JIGSAWU]

First of all i'd like to thank you for your answers.

Super dead load is used to express all the dead loads except from self weight?It can describe the dead load of concete slabs for example? I m not quite sure i understood the meaning,can you give an example?

As for the reduced live load,I'm going to search the forum but an example would be useful too.

Thanks

 

[slickdeals]

Dead loads are typically loads which the program can calculate by itself based on geometry (length, width, thickness) and material properties specified (density). Steel framing member weights are automatically calculated by the program.

Any dead load which cannot be calculated by the program need to be input as a SUPERDEAD. Examples of this could be slab finishes (marble, tile), masonry loads etc.

Live load reduction is typically permitted for columns supporting multiple floors, as recommended by ASCE 7. The reduction of live load is based on probabilities. Assume that you have a 25 story building, with a column supporting a tributary area of 30'x30' on each floor. The chances that each one of these floors has a live load at the same time is unlikely and the code allows you to reduce the load based on its "Influence Area". Greater the influence area, the more reduction you are allowed to take, but no more than a 60% reduction on live loads. Minimum Lo = 0.4 L. Some restrictions apply, check Chapter 4 of ASCE 7

 

[JIGSAWU]

I would like to thank all of you and especially slickdeals for your valuable help.Now i know the meaning of these 2 loads and where i can use them.