Deflection in Masonry Columns |
  
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Deflection in Masonry Columns |
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Last revised: Tuesday, March 17, 2026 at 02:38 PM
Short answer: TMS 402-22 does not explicitly require using cracked-section properties for deflection of reinforced masonry columns; it is largely silent on a detailed cracked vs. gross stiffness model for column deflection. In practice, the code framework implies elastic (uncracked / effective) stiffness unless second-order analysis or rational methods justify otherwise, with additional guidance coming from commentary and general masonry design practice rather than a prescriptive clause.
TMS 402 is written as a minimum design code covering strength and serviceability, but it intentionally avoids prescribing detailed analysis models for stiffness in many cases (Accuris Standards Store).
For columns specifically:
•The code addresses axial load, flexure, and slenderness (P–Δ effects).
•It requires accounting for second-order effects when slenderness is significant.
•It relies on modulus of elasticity (Em)–based stiffness in analysis.
However:
•There is no explicit clause stating “use cracked section properties” for deflection of masonry columns.
•Nor is there a direct requirement to use gross section properties.
From how the code is structured:
•Masonry analysis in TMS 402 is fundamentally elastic-based (Em·I) for service-level behavior.
•Section properties used for stiffness are typically gross or effective (uncracked) section properties unless a refined analysis is performed.
This aligns with general masonry guidance:
•Average (uncracked) section properties → used for elastic stiffness
•Cracked/effective properties → used only when explicitly modeling inelastic response or for refined deflection estimates (CMHA)
•For columns, deflection is primarily handled indirectly through:
omoment magnification or
osecond-order analysis
•These provisions are based on member stiffness (EI), but again the code does not redefine I as cracked.
The TMS 402-22 Commentary (non-mandatory) is where intent is clarified:
•Masonry is brittle in tension, so cracking can occur.
•However, for columns under dominant axial compression, flexural cracking is often limited.
•Therefore, gross or effective section properties are typically acceptable for column stiffness, especially for:
ocompression-controlled sections
omembers with low tension demand
Cracked-section modeling is generally:
•not required by code, and
•only used when performing advanced analysis or when flexural tension governs.
For reinforced concrete masonry columns under TMS 402-22:
•Default / code-consistent approach
oUse gross (or effective uncracked) section properties for stiffness (EI)
oApply slenderness / second-order provisions as required
•When cracked properties may be used (engineering judgment)
oSignificant bending with tensile cracking
oDetailed deflection predictions (serviceability-critical elements)
oNonlinear or refined analysis
•What the code does NOT do
oIt does not mandate cracked inertia (Icr) like ACI 318 does for RC beams/columns in deflection checks.
TMS 402-22 does not explicitly require cracked section properties for deflection of reinforced masonry columns.
The code framework implies use of gross (elastic) section stiffness, with cracked-section analysis being optional and based on engineering judgment rather than a prescriptive requirement.
