horizontal pre-eng truss reaction?

[jgeng]

In reading my truss drawings i have a "RL" reaction which I am assuming is the horizontal (lateral) load in plane with the truss in this case from wind loading since the thrust would be taken up by the horizontal bottom chord. what do i need to consider for this load? i have generally thought you design the truss connection for uplift & diaphragm to shearwall horizontal load in plane with shearwall (unless your using blocking to transfer the load).

 

[woodman88]

You design the connections for the loads you calculate for the building. Connect the trusses for your loads not for the loads someone else does. You only need to check that the truss design load cases meets or exceeds the required building load cases.

Garth Dreger PE
AZ Phoenix area

 

[abusementpark]

I'm not sure if I understand... you are designing the truss to structure connection after the truss supplier has designed the trusses?

 

[woodman88]

The truss designer did not and will not design the building. The building designer designs the building and the connections for the building. The truss designs must meet or exceed the requirements of the building. If the truss design exceeds the building requirements, you do not have to upgrade the connections to what the truss design shows.

Garth Dreger PE
AZ Phoenix area

 

[rscassar]

Wouldn't any horizontal thrust be resisted by the diaphragm and shear walls?

 

[woodman88]

The typical truss does not have a horizontal reaction at the bearing. It has a horizontal reaction from the wind load on the bearing wall to the truss which is transferred to the roof sheathing. The horizontal reation on the truss design is from an assumed pin bearing, which the truss does not have. The horizontal reaction that is shown on the truss design is actually resisted by the roof sheathing not the assumed pin bearing. The shear walls would have to be designed up to the roof sheathing or have a drag truss that is designed from lateral loads given to the truss designer by the building designer.


Garth Dreger PE
AZ Phoenix area

 

[gobsmacked]

jgeng hasn't explained whether the truss is in the vertical or the horizontal plane, or some inclined plane. In my experience RL means the left hand reaction, but it is unwise to make assumptions. Why not ask the person who did the drawing what they meant?