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原文传递 Comparison of the design of composite prestressed concrete hollow-core floor units between Eurocode 2 and ACI 318

题名：	Comparison of the design of composite prestressed concrete hollow-core floor units between Eurocode 2 and ACI 318
正文语种：	eng
作者：	Elliott, Kim S.
作者单位：	Precast Concrete Ind London England
关键词：	ACI 318;composite floor slab;deflection;Eurocode 2;floor unit;hollow-core;pretensioning;propped slab;service stress;shear capacity;structural topping;ultimate strength
摘要：	A typical 1200 mm (48 in.) wide x 200 mm (8 in.) deep prestressed concrete hollow-core floor unit is analyzed and designed as a composite slab with a 75 mm (3 in.) deep structural topping in order to make a comparison between Eurocode 2: Design of Concrete Structures (EC2-1-1) and the American Concrete Institute's Building Code Requirements for Structural Concrete (ACI 318-08) and Commentary (ACI 318R-08). This is the second of two papers. The first was published in PCI Journal in the March-April 2021 issue and designed a noncomposite hollow-core unit. The present comparison includes two-stage composite service and ultimate moments of resistance, ultimate composite shear capacities, camber and deflections, and interface shear between the hollow-core unit and cast-in-place concrete topping. Precast concrete cylinder strength was 40 N/mm(2) (5800 psi) and the cast-in-place concrete topping was 25 N/mm(2) (3625 psi). The hollow-core unit was pretensioned using 10 number seven-wire helical strands. Worked examples are presented in parallel formation for EC2 and ACI 318.The service and ultimate moments of resistance were respectively 3.2% and 5.1% greater when calculated based on ACI 318. The uncracked shear capacity was7.4% greater for the ACI 318 calculation, but the flexurally cracked capacity was 80% lower. This can often be the limiting criteria for ACI 318, but rarely for EC2. The effect of propping increased the service moments of resistance by about 11% in both codes.The ratio of the service moment to resistance M-s/M-sr,M-c for EC2 and M-s/M-sn,M-c for ACI was 5% greater than for the ratio of the ultimate design bending moment to the ultimate moment of resistance of the composite section M-Ed/M-Rd,M-c for EC2 and M-u/phi M-n,M-c for ACI 318. This means that the composite slab is just critical at the serviceability limit state. Regarding shear capacity V-Rd,V-c,V-c, was only limiting when the span to total depth ratio for the hollow-core plus topping was less than about 26, but for ACI 318, the flexurally cracked shear capacity of the composite section phi V-ci,V-c was limiting when the span to total depth ratio was 30, showing that shear cracking in flexure is often the governing criteria.For the interface shear between the hollow-core unit and cast-in-place concrete topping, there are no interface links to ACI 318 because hollow-core units have a roughened surface. A small number of interface links, which have a factory-produced surface, are required by EC2.
出版年：	2022
期刊名称：	PCI Journal
卷：	67
期：	4
页码：	25-57