Could you please verify whether MIDAS is checking for the phi*fr? If not, the reinforcement design will be too conservative in some cases. As per AASHTO 8th edition LRFD 6.10.1.1.1d, "For calculating flexural stresses in the concrete deck due to all permanent load and transient loads, the short-term modular ratio, n shall be used". Is MIDAS using short-term n for the concrete flexure stresses in this case?

For the LRFD minimum negative flexure concrete deck reinforcement for composite steel beam design, it looks like MIDAS doesn't check for phi*fr as specified in LRFD 6.10.1.7. Per MIDAS manual,  "Under negative moment" reinforcement is checked against Ars greater or equal to 0.01Adeck. But per AASHTO LRFD 6.10.1.7, this is only required for whenever the concrete tensile stress under SERVICE II exceeds phi*fr rather than for every section that has negative moment (this section remained unchanged between LRFD 2012 & LRFD 2018). Please see attached for LRFD section 6.10.1.7 & MIDAS manual. Could you please verify whether MIDAS is checking for the phi*fr? If not, the reinforcement design will be too conservative in some cases. 

Another question is per AASHTO 8th edition LRFD 6.10.1.1.1d, "For calculating flexural stresses in the concrete deck due to all permanent load and transient loads, the short-term modular ratio, n shall be used". Is MIDAS using short-tem n for the concrete flexure stresses in this case?

There're two more questions regarding this issue:

Q1. From the screen shot of your report, under 6.10.4.2 it looks like a factor of "2" is missing. The AASHTO limits is 2*fr instead of fr. I checked the report from my own model, and it looks like my MIDAS CIVIL 2018 version has fixed the problem. Please see attached image "MIDAS 6.10.4.2 CHECK".

Q2. Back to the first question in my original message of AASHTO 6.10.1.7. In 6.10.1.7 the minimum negative reinforcement should be greater than 1% of deck area only when the concrete stress under SERVICE II exceed fr. In MIDAS report this checking is under strength limit, and it is not comparing the concrete stress against fr. Please see attached image "MIDAS 6.10.1.7" for more details. Please verify that whether MIDAS is checking the SERVICE II conc stress for the minimum negative reinforcement criteria, and if so, how is that reflect in the report?

Ans. The code says to check this for factored construction loads and service loads.