Applies To
	Product(s):	STAAD Advanced Concrete Design
	Version(s):	Connect Edition
	Environment:
	Area:	Concrete Design
	Subarea:	Footing Design
	Original Author:	Bentley Technical Support Group

Question: 

Footing design shows all columns are failing. However, there is no information on the cause of failure. Please advise why the footings are failing in auto design.  

 

Solution:

Load combination 602 and 604 are causing the issue in footing sizing design. Load combination 602 is created using load cases 10,11 and 13, Load combination 604 is created using load cases 10,11 and 15. refer to snap below: 

Load case 10 and 11 are defined as dead load in RCDC as shown in the snap below:

Load combinations 602 and 604 are assigned with -ve dead load and -ve Wind load. As per our understanding gravity load (at-least self-weight of the structure) must be part of all load combinations used for design of any kind of structure and it should always be +ve i.e. (Gravity). 

if there is at-least one dead load case with +ve sign (which is there in other load combinations), RCDC will read those combinations and design the footings.  for load combinations 602 and 604, there is a single dead load assigned and it is assigned with -ve sign. it is always expected by the program that there will be at-least one dead load case present with +ve sign in all load combinations. Due to -ve sing to dead load case and that is the only dead load present in load combinations, RCDC unable to design the footing and showing footing size failure case. 

Footing size failure reason can be viewed at following path. 

We would suggest you add dead load to these combinations and design the structure in RCDC. 

 OR 

 Assign the load case 10 and 11 as other type and make sure that each load combinations consist of one dead load with +ve sign.