Error: "structure has no weight above the base for ubc analysis"

Question

Hi! May I ask a question? And I hope someone would help me. 
 
 We have a project for our subject. And we are building a 5 storey dormiel (dormitory/hotel). And when we run the analysis it shows an error saying STRUCTURE HAS NO WEIGHT ABOVE THE BASE FOR UBC ANSLYSIS. What should i do?

Rajat · Answer

Although the error message has been reported in the context of analysis per UBC 1997, it is a generic message that pertains to all codes that are based on the ELFP (Equivalent Lateral Force Procedure) method. 
 
 In Section 12.8.3 of ASCE 7-05, we find that it contains equations that describe how the shear at the base of the structure has to be distributed among the various levels of the structure. Those equations contain the term h, which is the height of any given level above the base. 
 
 This implies that the ELFP described in IBC 2006 (which in turn refers to Section 12.8 of ASCE 7-05) is to be applied only on those structures whose geometry consists of various levels and floors. The supports of the structure must all be at the lowest level; h for any level would then be measured above the supports. 
 
 Typically, this message is displayed if your model has only one level which is just the foundation mat alone. So, all the entities&mdash;plates and nodes&mdash;are at just a single elevation; h is hence zero, and the lateral forces cannot be computed using Equations 12.8-11 and 12.8-12 of ASCE 7-05. Unless you include the columns and beams of at least one or more floors and make the model resemble a frame having distinct Y coordinates, seismic analysis per the IBC 2006 or UBC 1997 cannot be performed. 
 
 If this explanation does not match your structural conditions (you mentioned a 5-storey building), it perhaps means that you have not specified seismic weights such as selfweight, member weight, joint weights, floor weights, etc. for floors that are above the support. If that too is not a valid explanation, please upload your model.