Title: Comparison of the design of prestressed concrete hollow-core floor units with Eurocode 2 and ACI 318
Date Published: March - April 2021
Volume: 66
Issue: 2
Page Numbers: 21 - 57
Authors: Kim S. Elliott
https://doi.org/10.15554/pcij66.2-01

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Abstract

A typical 1200 mm (48 in.) wide × 200 mm (8 in.) deep prestressed concrete hollow-core unit is analyzed and designed in order to make a comparison between Eurocode 2 and ACI 318-08. This includes calculations for serviceability limit state of stress and moment of resistance, ultimate moment of resistance, ultimate shear capacities, flexural stiffness (that is, for deflection), and cover to pretensioning tendons for conditions of environmental exposure and fire resistance. Concrete cylinder strength is 40 MPa (5.8 ksi), and concrete cube strength is 50 MPa (7.3 ksi). The hollow-core unit is pretensioned using seven-wire helical strands. Worked examples are presented in parallel formation according to Eurocode 2 and ACI 318.

For uniformly distributed loads, the design criterion between the service moment to service moment of resistance (M_s/M_sr for EC2 and M_s/M_sn for ACI 318) and the ultimate design bending moment to ultimate moment of resistance (M_Ed/M_Rd for EC2 and M_u/φM_n for ACI 318) is well balanced for this example. Usually the service moment is critical unless the amount of prestress is small. For EC2-1-1, flexurally uncracked shear capacity V_Rd,c is only limiting when the span-to-depth ratio in this example is less than about 35. For ACI 318, flexurally cracked shear capacity φV_ci is limiting when span-to-depth ratio is 42, showing that shear cracked in flexure will often be the governing criterion.