Comparison of the design of prestressed concrete hollow-core floor units with Eurocode 2 and ACI 318

PCI Journal ◽  
2021 ◽  
Vol 66 (2) ◽  
pp. 21-57
Author(s):  
Kim S. Elliott
Keyword(s):  
Prestressed Concrete ◽  
Limit State ◽  
Worked Examples ◽  
Design Criterion ◽  
Shear Capacity ◽  
Hollow Core ◽  
Depth Ratio ◽  
Eurocode 2 ◽  
Ultimate Moment ◽  
Moment Of Resistance

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 (Ms/Msr for EC2 and Ms/Msn for ACI 318) and the ultimate design bending moment to ultimate moment of resistance (MEd/MRd for EC2 and Mu/φMn 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 VRd,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 φVci is limiting when span-to-depth ratio is 42, showing that shear cracked in flexure will often be the governing criterion.

Shear Capacity Of Dry-Cast Extruded Precast, Prestressed Concrete Hollow-Core Slabs

PCI Journal ◽  
2019 ◽  
Vol 64 (4) ◽  
Author(s):  
Karl A. Truderung ◽  
Amr El-Ragaby ◽  
Mohamed Mady ◽  
Ehab El-Salakawy
Keyword(s):  
Prestressed Concrete ◽  
Shear Capacity ◽  
Hollow Core ◽  
Precast Prestressed Concrete

scholarly journals A CASE STUDY ON PRE-TENSIONING & POST TENSIONING SYSTEMS OF A PRESTRESSED CONCRETE

2020 ◽  
Vol 5 (2) ◽  
pp. 249-254
Author(s):  
Veerat Srilaxmi ◽  
K. Manju ◽  
M. Vijaya
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Prestressed Concrete ◽  
Nuclear Power ◽  
Shear Capacity ◽  
Depth Ratio ◽  
Concrete Pile ◽  
Post Tensioning

In Present days the pretensioning and post tensioning systems are very popularly using in the major constructions of a structure. The Pre-tensioning and Post-tensioning both methods are used under pre-stressing process. In which has few edges over the orthodox non-stressed structures like greater span to depth ratio, higher moment and shear capacity. These methods are generally adopted in the making of PSC girders, sleepers, Bridges, Slabs in buildings, Concrete Pile, Repair and Rehabilitations, Nuclear Power Plant etc.

scholarly journals Analytical model for determining the influence of support flexibility on shear capacity of hollow core slabs

2019 ◽  
Vol 262 ◽  
pp. 08005 ◽  
Author(s):  
Mateusz Surma ◽  
Wit Derkowski ◽  
Andrzej Cholewicki
Keyword(s):  
Prestressed Concrete ◽  
Model Development ◽  
Simple Calculation ◽  
Shear Resistance ◽  
Shear Capacity ◽  
Beam Model ◽  
Hollow Core ◽  
Engineering Analysis ◽  
Flexible Supports ◽  
German Model

The paper presents the authors’ model of calculating the shear capacity of prestressed concrete hollow core slabs in Slim Floor structures, the theoretical basis of which is Cholewicki’s two-beam model and the Finnish model by Pajari and Leskelӓ. The purpose of the model development was to find an alternative method for determining the horizontal tangential stress τzx which occurrence is decisive for reducing the shear resistance of channel slabs based on flexible supports. The model gives intermediate results between the Finnish model and the German model by Hegger and Roggendorf, which seems to be desirable, taking into account the conservative character of the Finnish model. The authors’ model is the first attempt to date at analytical consideration of the effect of web flexibility which may be important to maintaining an adequate capacity of the slab. In other models, the webs are treated as a rigid system, connecting the horizontal flanges of the slab. The model is a simple calculation tool, available to Slim Floor designers for an engineering analysis.

Flexural design of precast, prestressed ultra-high-performance concrete members

PCI Journal ◽  
2020 ◽  
Vol 65 (6) ◽  
pp. 35-61
Author(s):  
Chungwook Sim ◽  
Maher Tadros ◽  
David Gee ◽  
Micheal Asaad
Keyword(s):  
Prestressed Concrete ◽  
High Performance ◽  
High Performance Concrete ◽  
Limit State ◽  
Design Guidelines ◽  
Design Tool ◽  
Supplementary Cementitious Materials ◽  
Ultra High Performance Concrete ◽  
Concrete Members ◽  
Cylinder Strength

Ultra-high-performance concrete (UHPC) is a special concrete mixture with outstanding mechanical and durability characteristics. It is a mixture of portland cement, supplementary cementitious materials, sand, and high-strength, high-aspect-ratio microfibers. In this paper, the authors propose flexural design guidelines for precast, prestressed concrete members made with concrete mixtures developed by precasters to meet minimum specific characteristics qualifying it to be called PCI-UHPC. Minimum specified cylinder strength is 10 ksi (69 MPa) at prestress release and 18 ksi (124 MPa) at the time the member is placed in service, typically 28 days. Minimum flexural cracking and tensile strengths of 1.5 and 2 ksi (10 and 14 MPa), respectively, according to ASTM C1609 testing specifications are required. In addition, strain-hardening and ductility requirements are specified. Tensile properties are shown to be more important for structural optimization than cylinder strength. Both building and bridge products are considered because the paper is focused on capacity rather than demand. Both service limit state and strength limit state are covered. When the contribution of fibers to capacity should be included and when they may be ignored is shown. It is further shown that the traditional equivalent rectangular stress block in compression can still be used to produce satisfactory results in prestressed concrete members. A spreadsheet workbook is offered online as a design tool. It is valid for multilayers of concrete of different strengths, rows of reinforcing bars of different grades, and prestressing strands. It produces moment-curvature diagrams and flexural capacity at ultimate strain. A fully worked-out example of a 250 ft (76.2 m) span decked I-beam of optimized shape is given.

Querkrafttragfähigkeit von Brückenträgern aus Spannbeton mit geringen Querkraftbewehrungsgraden/Shear Capacity of Prestressed Concrete Bridge Girders with Small Shear Reinforcement Ratios

Bauingenieur ◽  
2020 ◽  
Vol 95 (11) ◽  
pp. 397-407
Author(s):  
Viviane Adam ◽  
Martin Herbrand ◽  
Josef Hegger
Keyword(s):  
Prestressed Concrete ◽  
Shear Capacity ◽  
Bridge Girders ◽  
Concrete Bridge ◽  
Shear Reinforcement ◽  
Prestressed Concrete Bridge ◽  
Small Shear

Zusammenfassung Neben gestiegenen Verkehrslasten führen strengere normative Regeln zu höheren Anforderungen an Spannbetonbrücken. Viele ältere Spannbetonbrücken im Bestand weisen daher rechnerische Defizite bei der Querkrafttragfähigkeit auf. Durch experimentelle und theoretische Untersuchungen konnten im Zuge eines Forschungsprojekts für die Bundesanstalt für Straßenwesen (BASt) verfeinerte Berechnungsansätze für Querkraft erarbeitet werden. In diesem Beitrag werden am Institut für Massivbau der RWTH Aachen (IMB) durchgeführte Großversuche an Spannbetondurchlaufträgern vorgestellt. Die Träger mit Rechteck- oder I-Profil wiesen geringe Querkraftbewehrungsgrade auf und wurden durch Gleichstreckenlasten beansprucht. Auf Basis der Forschungsergebnisse wurde ein verfeinertes Bemessungsmodell entwickelt, das aus einem modifizierten Fachwerkmodell mit additivem Betontraganteil besteht und gegenüber dem Ansatz nach aktueller Nachrechnungsrichtlinie weitere Querkrafttragreserven berücksichtigt.

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