What Is a Transfer Girder Design — and When Is It Needed?
Transfer girders (the deep beams or the trusses collecting the columns above and delivering to the columns below) resolve the vertical discontinuity — the tower's columns not aligning with the podium's, the setback's, the lobby's open. The design: the enormous shear and moment (the deep beam — the strut-and-tie; the prestressed — the camber), the deflection (the supported columns' — the settlement-sensitive), and the construction (the shoring — the staged). The discontinuity's engineered bridge.
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When transfers are needed
The podium (the tower's dense grid — the parking's wide; the transfer floor), the setback (the tower's — the stepping; the columns' shifting), the lobby (the open — the columns removed; the girder spanning), and the mixed-use (the residential's — the retail's below; the grids' differing).
Design approach
The deep beam (the span/depth — the <2; the strut-and-tie — the STM; the shear's dominance), the prestressed (the camber — the deflection's control; the staged stressing), the deflection (the supported — the differential; the finishes' cracking), and the 3D (the FEA — the load path; the punching — the columns').
Construction and detailing
The shoring (the multi-floor — the loads; the backshoring), the pour (the mass — the thermal; the continuous), the congestion (the steel's — the detailing; the constructability), and the monitoring (the deflection — the survey; the camber's verification). ACI 318's deep beams and the STM — the transfer's code.
The bottom line
Design transfer girders as deep beams (strut-and-tie per ACI 318) or prestressed members — control deflection of supported columns, shore multi-floor during construction, and verify camber.
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