I am performing concrete design for a beam per the ACI code and I encounter an error message : "LOCATION FOR DESIGN FOR SHEAR AT START OF MEMBER 2 IS BEYOND THE MIDPOINT OF MEMBER. DESIGN FOR SHEAR AND TORSION NOT PERFORMED." How can I get around this situation?
STAAD performs concrete design for shear and torsion at locations defined by
(d + SFACE) from the start of the member
(d+EFACE) from the end of the member
respectively. The basis for this assumption can be found in Section 22.214.171.124 of ACI 318-99.
If these locations are beyond the mid-point of the member, that triggers the error message you encountered. In case you are not familiar with the parameters SFACE and EFACE, you will see in Chapter 3 of the Technical Reference Manual in Table 3.1 that these are values which the user may specify to convey to STAAD how far the face of the member is from the nodal point of the member. The default value for SFACE and EFACE is 0.0. "d" is the effective depth of the member.
So, this is what you can do. You can set the values for SFACE and EFACE to be negative quantities equal in magnitude to "d". That will result in (d+SFACE) and (d+EFACE) becoming zero, which means that the design will be performed at the nodal points of the member, thereby avoiding the situation of the design point being beyond the mid-point of the member.
So, in your input file, under the START CONCRETE DESIGN command, specify these parameters along the following lines:
START CONCRETE DESIGNCODE ACISFACE -d MEMB 110EFACE -d MEMB 110DESIGN BEAM 110END CONCRETE DESIGN
where "d" is the effective depth of the member.
Please enter the numerical value for the effective depth. For example if the total depth of the beam is 36 inches and you have a 3 inches clear cover then approx. effective depth would be 36 - 3 -1/2 = 32.5 inches. Hence you should enter
SFACE -32.5 MEMB 110EFACE -32.5 MEMB 110