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.

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 Influence of concrete topping on behaviour of prestressed Hollow Core floor slabs on flexible supports

2013 ◽  
Vol 12 (1) ◽  
pp. 107-114 ◽  
Author(s):  
Wit Derkowski ◽  
Mateusz Surma
Keyword(s):  
Shear Capacity ◽  
Bottom Surface ◽  
Shear Stresses ◽  
Hollow Core ◽  
Floor Slabs ◽  
Flexible Supports ◽  
Slender Beams ◽  
Beam Height ◽  
Longitudinal Cracks ◽  
Normal And Shear Stresses

Slim Floors (SF) are the structures made of the Hollow Core (HC) slabs supported on the slender beams, where the beam height is usually slightly greater than the height of precast slab element. With the increase of the supports' deflection, the deformation of the HC slab occurs, and in consequence, additional transverse normal and shear stresses appear in the precast element, which can cause a diagonal cracking and destruction of external webs of this element. It may also result in longitudinal cracks on bottom surface of the slab. Despite the frequent implementation of this type of structures, the existing standard EN 1168 gave only a brief record of the need to take the reduction in design shear capacity into account, but is not given any calculation procedure. It is widely believed that reduction of unfavourable effects of shear stress in the HC slab’s web can be achieved by filling the cores with concrete or arrangement of the monolithic layer or concrete topping. The fib guidelines are practically the only one document which allows to determine the shear capacity of SF slabs, including the influence of concrete topping or core filling – brief description of this design model is presented in the paper. In order to determine the effect of concrete topping on the behaviour of prestressed HC slabs on the flexible supports, a number of calculation analyzes were performed, which take into account the effects of thickness of the concrete topping, the value of the friction coefficient between the concrete topping and the precast element, the sequence of concreting of vertical joints and topping layer and the amount of supplementary reinforcement in the topping. The results of the calculations, and the conclusions derived from them, are presented in the article.

PREDICTION OF PUNCHING SHEAR RESISTANCE OF PRESTRESSED CONCRETE FLAT SLABS

2011 ◽  
Vol 14 (1) ◽  
pp. 180-196
Author(s):  
A M Elshihy ◽  
H A ShehabEldeen ◽  
O Shaalan ◽  
R S Mahmoud
Keyword(s):  
Prestressed Concrete ◽  
Shear Resistance ◽  
Punching Shear ◽  
Flat Slabs

Flexural Vibration of Prestressed Concrete Bridges with Corrugated Steel Webs

2017 ◽  
Vol 17 (02) ◽  
pp. 1750023 ◽  
Author(s):  
Xia-Chun Chen ◽  
Zhen-Hu Li ◽  
Francis T. K. Au ◽  
Rui-Juan Jiang
Keyword(s):  
Finite Element ◽  
Shear Deformation ◽  
Prestressed Concrete ◽  
Natural Frequencies ◽  
Sandwich Beam ◽  
Flexural Vibration ◽  
Concrete Bridges ◽  
Mode Shapes ◽  
Beam Model ◽  
Prestressed Concrete Bridges

Prestressed concrete bridges with corrugated steel webs have emerged as a new form of steel-concrete composite bridges with remarkable advantages compared with the traditional ones. However, the assumption that plane sections remain plane may no longer be valid for such bridges due to the different behavior of the constituents. The sandwich beam theory is extended to predict the flexural vibration behavior of this type of bridges considering the presence of diaphragms, external prestressing tendons and interaction between the web shear deformation and flange local bending. To this end, a [Formula: see text] beam finite element is formulated. The proposed theory and finite element model are verified both numerically and experimentally. A comparison between the analyses based on the sandwich beam model and on the classical Euler–Bernoulli and Timoshenko models reveals the following findings. First of all, the extended sandwich beam model is applicable to the flexural vibration analysis of the bridges considered. By letting [Formula: see text] denote the square root of the ratio of equivalent shear rigidity to the flange local flexural rigidity, and L the span length, the combined parameter [Formula: see text] appears to be more suitable for considering the diaphragm effect and the interaction between the shear deformation and flange local bending. The diaphragms have significant effect on the flexural natural frequencies and mode shapes only when the [Formula: see text] value of the bridge falls below a certain limit. For a bridge with an [Formula: see text] value over a certain limit, the flexural natural frequencies and mode shapes obtained from the sandwich beam model and the classical Euler–Bernoulli and Timoshenko models tend to be the same. In such cases, either of the classical beam theories may be used.

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.

scholarly journals Effect of Prestress on Shear Capacity of Prestressed Concrete Beams.

2001 ◽  
pp. 149-159
Author(s):  
Yasuhiro MIKATA ◽  
Susumu INOUE ◽  
Kazuo KOBAYASHI ◽  
Tamotsu NIEDA
Keyword(s):  
Prestressed Concrete ◽  
Concrete Beams ◽  
Shear Capacity
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