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:
- For further details of the checks that have been implemented, see: General requirements (beams seismic: ACI 318), Flexural reinforcement (beams seismic: ACI 318), Transverse reinforcement (beams seismic: ACI 318) or consult the respective clause reference in the code.
- Most of the requirements will be fulfilled through automatic design. In some cases specific design options will need to be set by the user.
- Additional requirements may apply to members that are not part of the SFRS when in SDC’s D, E or F
- Confinement regions: - support regions; - Probable flexural yield regions; - Lap splice regions.