Deck slabs of skew girder bridges

1995 ◽  
Vol 22 (3) ◽  
pp. 514-523 ◽  
Author(s):  
Baidar Bakht ◽  
Akhilesh C. Agarwal
Keyword(s):  
Reinforced Concrete ◽  
Cross Section ◽  
Shear Failure ◽  
Highway Bridges ◽  
Steel Reinforcement ◽  
Fibre Reinforced Concrete ◽  
Girder Bridges ◽  
Deck Slabs ◽  
Concrete Deck ◽  
Deck Slab

Canadian codes allow the design of concrete deck slabs of slab-on-girder bridges by taking account of the internal arching action that develops in these slabs under concentrated wheel loads in particular. Provided that certain prescribed conditions are met, a deck slab is deemed to have met the design criteria if it is provided with a top and a bottom layer of steel reinforcement with each layer consisting of an orthogonal mesh of steel bars in which the area of cross section of the bars in each direction is at least 0.3% of the effective area of cross section of the deck slab. For deck slabs of bridges having skew angles greater than 20°, the codes require the minimum amount of reinforcement to be doubled in the end zones near the skew supports. Model testing has shown that need for such an increase can be eliminated by providing composite end diaphragms with high flexural rigidity in the horizontal plane. The proposed concept is tested on a model of fibre-reinforced concrete deck without steel reinforcement in which deficiencies in the confinement of the deck slab readily manifest themselves in form of a bending, rather than punching shear, failure. Key words: highway bridges, bridge decks, deck slabs, skew deck, skew bridges, fibre-reinforced concrete decks.

Experimental investigation of fibre-reinforced concrete deck slabs without internal steel reinforcement

1993 ◽  
Vol 20 (3) ◽  
pp. 398-406 ◽  
Author(s):  
Aftab A. Mufti ◽  
Leslie G. Jaeger ◽  
Baidar Bakht ◽  
Leon D. Wegner
Keyword(s):  
Reinforced Concrete ◽  
Concrete Slab ◽  
Steel Reinforcement ◽  
Punching Shear ◽  
Fibre Reinforced Concrete ◽  
Reinforced Concrete Slab ◽  
Shear Connectors ◽  
Deck Slabs ◽  
Concrete Deck ◽  
Deck Slab

It is now well established that concrete deck slabs of slab-on-girder bridges subjected to concentrated loads develop an internal arching system provided that certain conditions of confinement of the concrete are met. Because of this arching system, the deck slab, being predominantly in compression, fails in punching shear rather than in flexure. This aspect of deck slab behaviour, coupled with the corrosion problems associated with steel reinforcement in concrete, has prompted the authors to investigate the feasibility of fibre-reinforced concrete decks that are entirely devoid of steel. Through tests on a small number of half-scale models, it has been established that fibre-reinforced concrete slab with inexpensive non-ferrous fibres is indeed feasible, provided that the top flanges of the steel girders are connected just below the deck by transverse steel straps and the concrete deck is joined to the girders and diaphragms by shear connectors. The straps and shear connectors together provide the restraint necessary for development of the internal arching system in the slab, whilst the fibres control cracking due to the effects of shrinkage and temperature in the concrete. This paper describes the exploratory model tests and presents their results. Key words: deck slab, fibre-reinforced concrete, internal arching, punching shear, slab-on-girder bridge.

Experimental investigation of the role of reinforcement in the strength of concrete deck slabs

2000 ◽  
Vol 27 (3) ◽  
pp. 475-480 ◽  
Author(s):  
O Shervan Khanna ◽  
Aftab A Mufti ◽  
Baidar Bakht
Keyword(s):  
Steel Reinforcement ◽  
Scale Model ◽  
Transverse Reinforcement ◽  
Deck Slabs ◽  
Steel Bars ◽  
Failure Loads ◽  
Transverse Steel ◽  
Concrete Deck ◽  
Deck Slab

To study systematically the role of each layer of steel reinforcement in conventionally reinforced deck slabs of girder bridges, a full-scale model was built of a 175 mm thick concrete deck slab on two steel girders with a center-to-center spacing of 2.0 m. The 12 m long deck slab was conceptually divided into four 3 m long segments, identified as segments A, B, C, and D. Segment A contained isotropic steel reinforcement in two layers, conforming to the requirements of the Ontario Highway Bridge Design Code (OHBDC). Segment B contained only the bottom layer of steel reinforcement. Segment C contained only the bottom transverse steel bars. Segment D contained only bottom transverse glass fibre reinforced polymer (GFRP) bars having the same axial stiffness, but 8.6 times the axial tensile strength, as those of the steel bars in segment C. Each segment of the deck slab was tested to failure under a central concentrated load, simulating the dual tire footprint of 250 × 500 mm dimension of a typical commercial vehicle. All segments failed in the punching shear mode. The failure loads for the four segments were found to be 808, 792, 882, and 756 kN, respectively; these failure loads are similar in magnitude to that of a 175 mm thick steel-free deck slab with steel straps having nearly the same cross-sectional area per metre length of the slab as those of the bottom transverse steel bars in the first three segments. The tests on the four segments of the full-scale model have confirmed that (i) only the bottom transverse reinforcement influences the load carrying capacity of a reinforced concrete deck slab and (ii) the stiffness of the bottom transverse reinforcement, rather than its strength, is of paramount importance.Key words: arching, deck slab, FRP, shake down, slab-on-girder bridge.

Revisiting arching in deck slabs

1996 ◽  
Vol 23 (4) ◽  
pp. 973-981 ◽  
Author(s):  
Baidar Bakht
Keyword(s):  
Design Method ◽  
Field Tests ◽  
Scale Model ◽  
Girder Bridges ◽  
Transverse Arch ◽  
Deck Slabs ◽  
Arching Action ◽  
Girder Bridge ◽  
Concrete Deck ◽  
Deck Slab

The arching action in concrete deck slabs of girder bridges is generally recognized and is utilized by the Ontario Highway Bridge Design Code, and some other codes, to specify an empirical design method which leads to considerable savings in the amount of reinforcement. Despite this general recognition, there are some aspects of the arching action that are yet to be explored. To the knowledge of the author, all reported laboratory and field tests on deck slabs exploring its arching action under applied loads have been conducted by measuring strains in the bottom transverse reinforcement midway between the girders. Based on the results of tests on a full-scale model of a deck slab, it has been confirmed in this note that the transverse bottom reinforcement in the deck slab acts as a tie to the internal transverse arch in the slab. Because of embedment in concrete, the force in this reinforcement is the smallest midway between the girders, and not the largest as would be the case if the slab were in pure bending. Key words: arching in slabs, deck slabs, girder bridge, punching shear, steel-free deck slabs.

AASHTO’s Load and Resistance Factor Design Specifications for Transverse Braces: Adverse Effects on Integrity and Durability of Reinforced Concrete Deck Slabs

2000 ◽  
Vol 1740 (1) ◽  
pp. 118-125 ◽  
Author(s):  
Martin P. Burke ◽  
Joseph S. Seif
Keyword(s):  
Reinforced Concrete ◽  
Highway Bridges ◽  
Resistance Factor ◽  
Structural Systems ◽  
Steel Bridge ◽  
Design Specifications ◽  
Deck Slabs ◽  
Factor Design ◽  
Load And Resistance Factor ◽  
Concrete Deck

The transverse bracing provisions (diaphragms, cross-braces, crossframes, and so on) of the 1998 AASHTO load and resistance factor design (LRFD) bridge design specifications for the design of deck-type highway bridges are examined. This examination suggests that implementation of these provisions not only will have an adverse effect on the integrity and durability of reinforced concrete deck slabs, and consequently on life-cycle bridge costs; implementation of such provisions also has the potential to affect the desirability of steel bridge construction adversely. Instead of avoiding the use of midspan braces, as implied by LRFD provisions, it is urged that midspan braces be more generally recognized as primary elements of complex superstructure structural systems and thus be sized and spaced to function not only as transverse flange braces but also integrally with concrete deck slabs to distribute vehicular loads laterally. Such a practice not only will yield more efficient higher-quality structural systems capable of functioning effectively for 100 years or more, thus doubling their presently expected lives, but it will also help extend the service lives of the more vulnerable reinforced concrete deck slabs.

Finite element investigation of fibre-reinforced concrete deck slabs without internal steel reinforcement

1994 ◽  
Vol 21 (2) ◽  
pp. 231-236 ◽  
Author(s):  
Leon D. Wegner ◽  
Aftab A. Mufti
Keyword(s):  
Finite Element ◽  
Reinforced Concrete ◽  
Plain Concrete ◽  
Experimental Tests ◽  
Failure Criteria ◽  
Steel Reinforcement ◽  
Nonlinear Finite Element ◽  
Fibre Reinforced Concrete ◽  
Deck Slabs ◽  
Failure Loads

Experimental tests on half-scale models have demonstrated that polypropylene-fibre-reinforced concrete (PFRC) bridge deck slabs completely devoid of conventional steel reinforcement will fail by punching shear under concentrated loads considerably greater than those specified for design, provided the top flanges of the supporting girders are adequately restrained from moving laterally. Similar models were analyzed using nonlinear finite element techniques in order to reproduce experimentally observed load–deflection behaviours and failure loads. Commonly available concrete failure criteria for plain concrete was incorporated into the material model used for the PFRC deck slab. Results of the finite element analyses are presented. It is shown that while predicted load–deflection paths were less than satisfactory, accurate predictions of failure loads were achieved, but only after considerable tuning of various modelling parameters. Key words: nonlinear finite element method, bridge decks, fibre-reinforced concrete.

Fibre-reinforced polymer composite bars for the concrete deck slab of Wotton Bridge

2003 ◽  
Vol 30 (5) ◽  
pp. 861-870 ◽  
Author(s):  
Ehab El-Salakawy ◽  
Brahim Benmokrane ◽  
Gérard Desgagné
Keyword(s):  
Field Test ◽  
Remote Monitoring ◽  
Concrete Bridges ◽  
Fibre Optic ◽  
Reinforced Polymer ◽  
Deck Slabs ◽  
Fibre Reinforced Polymer ◽  
Concrete Deck ◽  
Frp Bars ◽  
Deck Slab

A new concrete bridge in the Municipality of Wotton, Quebec, Canada, was constructed using fibre-reinforced polymer (FRP) bars as reinforcement for the deck slab. The new bridge is a girder type with four main girders simply supported over a span of 30.60 m. One half of the concrete deck slab was reinforced with carbon and glass FRP bars, and the other half with conventional steel bars. The design of the reinforced concrete deck slab was made according to sections 8 and 16 of the new Canadian Highway Bridge Design Code. The bridge was well instrumented at critical locations for long-term internal temperature and strain data collection using fibre optic sensors. The construction of the bridge was completed and the bridge opened for traffic in October 2001. The bridge was then tested for service performance using standard truckloads. Design, construction details, and the results of the field test and 1 year of remote monitoring are discussed. Under the same real service and environmental conditions, very similar behaviour was obtained from the FRP (glass and carbon) and steel bars.Key words: concrete bridges, deck slabs, FRP bars, field test, fibre optic sensors, remote monitoring, serviceability.

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