Strap beams, also known as strap footings or cantilever footings, are critical structural elements, particularly in situations where a column must be placed on the boundary line of a property 1. The (a specific type of reinforced concrete beam used in foundation engineering) connects an eccentric exterior footing to an interior footing to balance the overturning moment 1.
: Comprehensive navigation and tool definitions are available in the STRAP User Manual .
A "cold joint"—where concrete was poured at different times without proper bonding—is a weak spot that can crack.
BeamD enforces global international design parameters (including ). Under the Serviceability Limit State, the module calculates the theoretical crack width ( ) using the equation: atir strap and beamd with crack
In addition to structural cracking, concrete elements undergo long-term deformations due to creep and shrinkage. Inside STRAP's concrete post-processor, engineers can input precise creep coefficients ( , often defaulting to
: Lower stiffness in a cracked beam transfers bending moments to uncracked structural elements. Deflection Control : Relying on the gross area ( Igcap I sub g
Lack of top reinforcement in the strap beam, which is critical for handling the high bending moments, can lead to cracking 3. Geotechnical and Settlement Issues Strap beams, also known as strap footings or
Below is a technical write-up on managing cracked beams using these programs: Modeling Cracked Sections in ATIR STRAP
Standard linear elastic analysis often underestimates structural movement because it assumes a gross (uncracked) cross-section. The ATIR suite allows for more realistic simulations:
: Define the geometry and apply "cracked" reduction factors to member properties to get realistic deflections. A "cold joint"—where concrete was poured at different
A licensed structural engineer will perform a (applying a known force and measuring deflection) and stamp a repair drawing. The cost ($500–$1,200 for the assessment) is trivial compared to a collapsed roof.
) to a value somewhere between the gross uncracked inertia ( Igcap I sub g ) and the fully cracked inertia ( Icrcap I sub c r end-sub
Once the analysis is complete, you would enter the concrete design module. Here, you define key parameters that are critical for crack control, such as concrete strength (e.g., 30 MPa or 4,000 psi) and steel yield strength (e.g., 420 MPa or 60 ksi). Most importantly, you specify the limiting crack width for the project in accordance with the chosen design code (e.g., EC2, ACI 318, or BS8007).