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The concrete type may also be designated as normal, sand-lightweight, or all-lightweight. LRFD defines lightweight concrete as concrete containing lightweight aggregate and having an air-dry unit weight not exceeding 0.120 kcf. However, if a unit weight is specified as being less than 0.120 kcf and it is desired that the concrete be treated as lightweight for design purposes, the concrete type must be explicitly changed by the user. Note that under starting with the LRFD 7th Edition, you can no longer select the concrete type, rather it is selected for you based on the unit weight, and will either be Normal Weight (>135 pcf) or Lightweight (< 135 pcf).
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These factors are the gamma factors present in the new Mcr equation introduced in the 6th Edition (LRFD Eq. 5.7.3.3.2-1/5.6.3.3-1). Currently Eriksson Culvert only uses the first and third gamma factors. CHBDC uses neither of these factors.
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Here the user can change any of the multiplication factors used in calculating the modulus of rupture (Fr). The first factor is the generic normal weight concrete factor used in both the 5th and 6th Editions of LRFD, along with STND. The second factor is only used in the 5th Edition for the minimum steel cracking moment. The lightweight concrete factors are used in all editions of LRFD prior to the 7th Edition, along with STND and AREMA. The 7th Edition (and later) only uses the first factor, and uses this factor for both normal and lightweight concrete. CHBDC uses none of these factors.
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