Negative Value for Lack of Fit Forces

Question:

At present we are doing forward construction stage analysis of a cable stayed bridge.
I have modeled all the construction stages.
The construction stages proposes to stress the stay cables in two stages (75% during erection & remaining 25% after placing of superimposed dead loads).
The Stay cable forces are provided by other consultant who has carried out the service stage design of this bridge.
The problem is when I check the Lack-of-Fit forces, the value of Lack-of-Fit forces is negative.

I am forwarding herewith the MIDAS model for your kind review. Please find the attachment for the same.

Thanks & Regards,

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Answer:
Dear User,

For the lack of fit forces computation greatly depends on the activation sequence.
The activation of structure group in the construction stage should be such that, first the segment erected in one stage and the cable to be activated in the next stage.










Also LOF is not applicable for multistage prestressing. LOF force only at the time of activation of the cable could be computed.




Regards,
Sindhu Bharathi
Technical Support Engineer, MIDAS
MIDAS Information Technology Co., Ltd.