Limitations and assumptions (beams seismic: ACI 318)

Tekla Structural Designer
Modified: 9 Nov 2022
2024
Tekla Structural Designer

Limitations and assumptions (beams seismic: ACI 318)

The following limitations and assumptions apply.

  • Seismic design is only performed for beams marked as part of a Seismic Force Resisting System and for seismic cantilevers.
  • Requirements for beams particularly in the case of members not part of any SFRS when in Seismic Design Categories D through F are not considered in the current release.
  • The design and detailing requirements of members part of Special Moment Frames is beyond scope (some checks are implemented but only due to their existence in lower toughness systems).
    Note: A full list of the code checks that have and have not been implemented is provided in the table below.
  • Seismic design checks are mostly based on capacity design obtained from the main reinforcement provided. This can lead to an over-design of structural members if the designer does not take steps to minimize excess capacity.
  • Beam seismic design and detailing in the current release is based on the beam rectangular section and takes under consideration the beam reinforcement only. In particular cases allowances for the slab presence and reinforcement might be required on top of the current design.
  • Seismic design and detailing requirements for structural diaphragms according to ACI318-11 sections 21.3.6 and 21.11 are not considered in the current release.

ACI 318 Seismic Code Checks for beams that have been implemented in Tekla Structural Designer

Code Ref. Requirement SFRS SDC A SDC B SDC C SDC D,E,F
21.1.4.2 Minimum required compressive strength of concrete SMF - - -
21.1.4.3 Maximum allowed compressive strength of light-weight concrete SMF - - -
21.1.5.2 Maximum allowed steel characteristic yield strength of longitudinal reinforcement SMF - - -
21.1.5.5 Maximum allowed longitudinal reinforcement yield strength used in the calculation of transverse reinforcement SMF - - -
21.1.6.2 Mechanical Splices within twice the member depth from column/beam face or yielding regions SMF - - -
21.1.6.2 Mechanical Splices outside twice the member depth from column/beam face or yielding regions SMF - - -
21.1.7.1 Welded Splices within twice the member depth from column/beam face or yielding regions SMF - - -
21.1.7.2 Welding of stirrups or other elements to longitudinal reinf. required by design SMF - - -
21.2.2 Minimum number of bars at top/bottom faces continuous throughout OMF - - -
21.2.2 Minimum number of bars at top/bottom faces continuous throughout IMF - - -
21.3.2 Maximum allowed factored axial force IMF - - -
21.3.3.1 Minimum Design shear force IMF - - -
21.3.4.1 Minimum +ve requirement (moment strength/steel) at a joint face IMF - - -
21.3.4.1 Minimum moment strength anywhere on a beam IMF - - -
21.3.4.2 Type of transverse reinforcement in confinement regions (hook/extension) IMF - - -
21.3.4.2 Length of support regions measured from the face of the joint IMF - - -
21.3.4.2 Maximum hoop spacing in support regions IMF - - -
21.3.4.2 Maximum distance between first hoop and joint face in support regions IMF - - -
21.3.4.3 Maximum hoop spacing outside confinement regions IMF - - -
21.5 Beams of Special Moment Frames will frame into columns of SMF SMF - - -
21.5.1.1 Maximum allowed factored axial force SMF - - -
21.5.1.2 Maximum allowed effective depth SMF - - -
21.5.1.3 Maximum allowed width SMF - - -
21.5.1.4 Maximum allowed width SMF - - -
21.5.2.1 Minimum number of bars at top/bottom faces continuous throughout SMF - - -
21.5.2.1 Minimum allowed area of reinforcement at top/bottom face throughout SMF - - -
21.5.2.1 Maximum allowed area of reinforcement: Max steel ratio at top/bottom/side face of the beam, ρmax SMF - - -
21.5.2.2 Minimum +ve requirement (moment strength / steel) at a joint face SMF - - -
21.5.2.2 Minimum moment strength anywhere on a beam SMF - - -
21.5.2.3 Lap splice location restrictions SMF - - -
21.5.2.3 Lap Splice transverse reinforcement type SMF - - -
21.5.2.3 Maximum allowed hoop spacing at lap splices SMF - - -
21.5.3.1 Length of support regions measured from the face of the joint SMF - - -
21.5.3.1 Non-reversing plastic hinges: Flexural Yield region size (centered) SMF - - -
21.5.3.2 Maximum hoop spacing in support regions SMF - - -
21.5.3.2 Maximum distance between first hoop and joint face in support regions SMF - - -
21.5.3.2 Non-reversing plastic hinges: Maximum horizontal center spacing SMF - - -
21.5.3.3 Maximum allowed spacing of flexural reinforcing bars SMF - - -
21.5.3.3 Maximum allowed lateral link leg spacing in confinement regions SMF - - -
21.5.3.4 Maximum hoop spacing outside confinement regions SMF - - -
21.5.3.6 Type of transverse reinforcement in confinement regions (hook/extension) SMF - - -
21.5.3.6 Type of transverse reinforcement in beam sections that extend laterally beyond the column core (hook/extension) SMF - - -
21.5.4.1 Minimum Design shear force SMF - - -
21.5.4.2 Unreinforced concrete shear resistance at confinement regions SMF - - -
21.7.2.1 Stress in the beam flexural tensile reinforcement at joints face for joint shear calculation SMF - - -
21.7.2.2 Tension anchorage length of beam long. Reinf. at external joints (beyond column inner face) SMF - - -
21.7.2.3 Maximum longitudinal reinforcement bar size SMF - - -
- Minimum beam depth at a joint where it contributes to joint shear SMF - - -
21.7.3.3 Spacing of confinement reinf. for longitudinal bars of beams outside the column core SMF - - -
21.7.3.3 Maximum distance between link legs in beam sections that extend laterally beyond the column core SMF - - -
21.7.5.1 Development length for beam longitudinal bars with a standard 90° hook SMF - - -
21.7.5.2 Development length for beam longitudinal straight bars SMF - - -
21.7.5.4 Development length for epoxy-coated or zinc and epoxy dual-coated beam longitudinal bars SMF - - -
21.8.2 Minimum distance from joint face for beam reinf. mechanical splices in ductile connections SMF - - -
21.8.2 Minimum nominal shear strength of ductile connections SMF - - -
21.8.3 Minimum nominal strength of the strong connection SMF - - -
ASCE 7/10 12.4.4 Extra design loads for horizontal cantilevers - - - -
Note:
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