2. 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

and

(d+EFACE) from the end of the member

respectively. The basis for this assumption can be found in

Section 11.1.3.1 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 DESIGN

CODE ACI

SFACE -d MEMB 110

EFACE -d MEMB 110

DESIGN BEAM 110

END CONCRETE DESIGN

where "d" is the effective depth of the member.

END.

9. A floor slab has been modeled using 4-noded plate elements. The

elements are subjected to pressure loading in the vertically

downward direction. A concrete design has been performed on the

elements. (See below for the reinforcement report for many of

those elements.)

Why is it that the moments as well as reinforcement are appearing

on the top and not on the bottom of the plates?

The reinforcement report for many of those elements looks like the

following:

ELEMENT LONG. REINF

(SQ.IN/FT)

MOM-X /LOAD

(K-FT/FT)

TRANS.

REINF

(SQ.IN/FT)

MOM-Y /LOAD

(K-FT/FT)

134 TOP : 5.944 1474.13 /

12 6.914

1679.58 /

12

BOTT: 1.296 0.00 / 0 1.296 0.00 / 0

Solution: In the above output, the word TOP and BOTTOM refer to

the "local" top and bottom surfaces of the individual elements,

and not in the global axis sense. The local top and bottom

surfaces depend on the way an element is defined in its incidence

statement.

TOP is defined as the surface which coincides with the positive

side of the local Z axis. BOTTOM is defined as the surface which

coincides with the negative side of the local Z axis.

Shown below are two examples in which the element incidence is

numbered in two contrasting ways.

In the first figure, the local Z axis of the element points in the

vertically upward direction. Consequently, the local top and

bottom surfaces have the same sense as the global top and bottom.

In the next figure, the local Z axis of the element points in the

vertically downward direction. Consequently, the local top and

bottom surfaces have the opposite sense as the global top and

bottom.

You can verify the direction of the local axes of the elements in

your model by doing the following. Click the right mouse button

and select Labels. Under the Plate category, switch on Plate

Orientation. The local axes will be displayed as shown in these

figures above.

END.

12. In concrete design per the ACI code, if the size of the

concrete beam

member which I am designing is limited and I need to have 2 rows

of reinforcement in the top or the bottom of the beam, how do I

input this request? Or Does Staad automatically output the data

with the second row? have been trying to find this in the Manuals.

I have seen LEVELS BUT IT DOES NOT SAY WHAT I NEED.

You do not have to input any special request. As long as the

section can be designed as a singly reinforced section

(reinforcement in the tension zone only), STAAD will try to fit

the bars in upto 2 layers. For each layer, the distance from the

bottom of the section is reported. The number of bars required for

each layer too is reported. It reports a failure only if more than

2 layers are required.

END.

13. In concrete design per the ACI code, what does the following

expression in the STAAD output file mean: BAR SIZE CAN NOT BE

MATCHED TO MEET ALL REQUIREMENTS

This means that though the program is able to come up with the

value of area of steel required, it is unable to comeup with a bar

arrangement which will satisfy the area requirement. Usually, this

is because either because the MINMAIN and MAXMAIN limits might be

too restrictive, or because the resulting bar spacing violates the

minimum spacing requirements of the code.

END.