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D10.A.5 Beam Design

Beams are designed for flexure, shear and torsion. For all these forces, all active beam loadings are prescanned to locate the possible critical sections. The total number of sections considered is 12 (twelve) unless this number is redefined with an NSECTION parameter. All of these equally spaced sections are scanned to determine moment and shear envelopes.

D10.A.5.1 Design for Flexure

Reinforcement for positive and negative moments are calculated on the basis of the section properties provided by the user. If the section dimensions are inadequate to carry the applied load, that is if the required reinforcement is greater than the maximum allowable for the cross section, the program reports that beam fails in maximum reinforcement. Rectangular sections are also designed with compression reinforcement.

Effective depth is chosen as Total depth - (Clear cover + diameter of stirrup + half the dia. of main reinforcement), and a trial value is obtained by adopting proper bar sizes for the stirrups and main reinforcements. The relevant clauses in Sections 1.5, 1.6, 2.1.1-2-5, 3.10 and 5.2.2 of NTC Concrete are utilized to obtain the actual amount of steel required as well as the maximum allowable and minimum required steel. These values are reported as ROW, ROWMX and ROWMN in the output and can be printed using the parameter TRACK 1.0 (see D10.A.4 Design Parameters). In addition, the maximum, minimum and actual bar spacing are also printed.

It is important to note that beams are designed for flexural moment MZ only. The moment MY is not considered in the flexural design.

D10.A.5.2 Design for Shear

Shear reinforcement is calculated to resist both shear forces and torsional moments. Shear forces are calculated at a distance (d+SFACE) and (d+EFACE) away from the end nodes of the beam. SFACE and EFACE have default values of zero unless provided under parameters (see D10.A.4 Design Parameters). Note that the value of the effective depth "d" used for this purpose is the update value and accounts for the actual c.g. of the main reinforcement calculated under flexural design. Clauses 2.1.5-6 and 5.2.4 of NTC Concrete are used to calculate the reinforcement for shear forces and torsional moments. Based on the total stirrup reinforcement required, the size of bars, the spacing, the number of bars and the distance over which they are provided are calculated. Stirrups due to geometric conditions are assumed to be 2-legged, due to design conditions could be 2 or 4-legged.

D10.A.5.3 Design for Anchorage

In the output for flexural design, the anchorage details are also provided. At any particular level, the START and END coordinates of the layout of the main reinforcement is described along with the information whether anchorage in the form of a hook or continuation is required or not at these START and END points. Note that the coordinates of these START and END points are obtained after taking into account the anchorage requirements. Anchorage length is calculated on the basis of the Clauses described in Section 3.1 of NTC concrete. In case the program selects 2 different diameters for the main or compression reinforcement, only the anchorage for the largest diameter is analyzed.

D10.A.5.4 Output

Serial number of bar level which may contain one or more bar group
Height of bar level from the bottom of the beam
Bar Info
Reinforcement bar information specifying number of bars and bar size
Distance from the start of the beam to the start of the reinforcement bar
Distance from the start of the beam to the end of the reinforcement bar
Anchor (STA/END)
States whether anchorage, either hook or continuation, is needed at the start (STA) or at the end (END).
Actually required flexural reinforcement (As/bd) where b = width of cross section (ZD for a rectangular or square section) and d = effective depth of cross section (YD minus the distance from extreme tension fiber to the centroid of main reinforcement).
Minimum required flexural reinforcement (Amin/bd)
Maximum required flexural reinforcement (Amax/bd)
Distance between centers of adjacent bars of main reinforcement
Factored shear force at section
Nominal shear strength provided by concrete
Nominal shear strength provided by shear reinforcement
Factored torsional moment at section
Nominal torsional moment strength provided by concrete
Nominal torsional moment strength provided by torsion reinforcement

D10.A.5.5 Example Output for Beam Design




   LEN -  6000.00(mm)  FY -   412.  FC -   20.  SIZE -  253.75 X  253.75(mm)

   LEVEL    HEIGHT     BAR INFO       FROM          TO           ANCHOR
             (mm)                     (mm)         (mm)         STA  END

     1         42.     5 - 2.MM      2468.         6000.        NO   YES
     2        212.     5 - 2.MM         0.         2782.        YES  NO

          B E A M  N O.     2 D E S I G N  R E S U L T S - SHEAR

    AT START SUPPORT - Vu=    5.63 KN  Vc=    0.00 KN  Vs=    0.00 KN
  Tu=      0.09 Kn Me  Tc=      0.00 Kn Me  Ts=      0.00 Kn Me  LOAD     1
                       STIRRUPS ARE NOT REQUIRED.
    AT END   SUPPORT - Vu=    5.63 KN  Vc=    0.00 KN  Vs=    0.00 KN
  Tu=      0.09 Kn Me  Tc=      0.00 Kn Me  Ts=      0.00 Kn Me  LOAD     1
                       STIRRUPS ARE NOT REQUIRED.