Analysis, Design and Construction of Two Extremely Skewed and Slender Post-Tensioned Concrete Bridges (original) (raw)
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An Extremely Skewed and Slender Slab Along the New Italian High Speed Railway Line
The paper summarises the main design and construction issues of two highly skewed post tensioned concrete bridges built along the A4 motorway connecting Milan to Turin. The twin bridges cross over the main railway lines connecting Milan to Switzerland and to north-western Italy and France. The two structures are characterized by a very high skew (61°) and extreme slenderness. The bridges are 50m long (47m span), 20m wide each (4 lane carriageways) and 80cm thick so as to allow the required clearance for the underneath railway lines. In order to support the two slender postensioned slabs, lateral edge beams shaped in the form of crash barrier have been added on both sides. The structures are the largest and heaviest single span slabs ever built in Italy so far. The slabs were cast in situ and post-tensioned behind the abutments and subsequently push launched over the railway lines without intermediate supports so as to eliminate every possible interference with the railway operations...
Analysis and Design of Straight and Skewed Slab Bridges
Journal of Bridge Engineering, 2012
Results of an investigation aimed at determining bending moments and shear forces, required to design skewed concrete slab bridges using the equivalent-beam method are presented in this paper. Straight and skewed slab bridges were modeled using grillage and finite-element models to characterize their behavior under uniform and moving loads with the objective of determining the most appropriate modeling approach for design. A parametric study was carried out on 390 simply supported slabs with geometries covering one to four lane bridges of 3-to 20-m spans and with skew angles ranging from 0 to 60°. The analyses showed that nonorthogonal grillages satisfactorily predict the amplitude and the transverse distribution of longitudinal bending moments and shear forces, and can be used for the analysis of skewed slab bridges. Results of the parametric study indicated that shear forces and secondary bending moments increase with increasing skew angle while longitudinal bending moments diminish. Equations are proposed to include, as part of the equivalent-beam method for skew angles up to 60°, the increase of shear forces and the reduction of longitudinal bending moments. Equations are also given for computing secondary bending moments. A simplified approach aimed at determining the corner forces for straight and skewed bridges is proposed as an alternative to a more-refined analysis. The analyses indicated the presence of high vertical shear stresses in the vicinity of free edges that justifies suggesting to provide shear reinforcement along the slab free edges.
Shear assessment of solid slab bridges
The capacity of solid slab bridges in shear is assessed by comparing the design beam shear resistance to the design value of the applied shear force due to the permanent actions and traffic loads. The transverse distribution of loads which occurs in slabs is thus not taken into account. Experiments on slabs under concentrated loads are carried out at Delft University of Technology. The results of these experiments are the basis for recommendations for the assessment of solid slab bridges. A slab factor and a horizontal load spreading method to determine the effective width are proposed. Preliminary results from an additional series of experiments confirm the hypothesis of superposition.
Wheel Load Distribution in Straight and Skewed Concrete Slab Bridges Stiffened with Railings
International Journal of GEOMATE, 2020
This paper presents the parametric investigation of the influence of railings on the wheel load distribution in simply-supported, one-span, three-and four-lane straight and skewed reinforced concrete slab bridges using the finite element method. A total of 96 bridge cases were modeled using finite-element analysis (FEA) and bridge parameters such as span length, slab width, and skew angle are varied within practical ranges. Typical railings built integrally with the bridge were placed on both edges of the deck slabs. AASHTO HS20 truck loadings were positioned transversely and longitudinally to produce maximum longitudinal live load bending moments in the slabs. The FEA wheel load distribution and bending moments were compared with reference straight bridges without railings as well as to the AASHTO Standard Specifications for Highway Bridges and the AASHTO LRFD Bridge Design Specifications. AASHTO overestimates FEA moments for almost all bridge cases and this overestimation increases with the increase in the skew angle, and it is more significant in the presence of two railings. Also, it was found that the reduction in slab moment due to skewness and railings is cumulative. The presence of railings can be considered to be a possible method for strengthening and rehabilitating straight and skewed concrete slab bridges.
EXPLORING THE PERFORMANCE OF REINFORCED CONCRETE SKEW SLABS: A COMPREHENSIVE ANALYSIS
IAEME PUBLICATION, 2020
The proliferation of skew bridges and flyovers, particularly in urban and developing areas, underscores the importance of understanding the behavior of skewed slab structures. Driven by the challenges of space constraints and the need for efficient construction methods, skewed slab bridges have become increasingly prevalent in highway interchanges and grade separators. This paper delves into the behavior of typical skew slabs, focusing on key aspects such as lateral live load distribution, the influence of skew angles, and the application of finite element methods for stress analysis. By synthesizing existing literature, this study aims to comprehensively explore the advantages and limitations of skew slab bridges. Additionally, it aims to identify areas for further research and improvement in design practices to enhance the performance and reliability of these critical infrastructure elements
Recommendations for the Shear Assessment of Reinforced Concrete Slab Bridges from Experiments
Structural Engineering International, 2013
Upon assessment of existing reinforced concrete short-span solid slab bridges according to the recently implemented Eurocodes that include more conservative shear capacity provisions and heavier axle loads, a number of these structures were found to be shear-critical. The results from recent experimental research on the shear capacity of slabs indicate that slabs benefit from transverse load distribution. Recommendations for the assessment of solid slab bridges in shear are developed on the basis of these experiments. A load spreading method for the concentrated loads is proposed and the applicability of superposition of loading is studied. The resulting most unfavourable position for the design trucks is provided and implemented in the so-called Dutch "Quick Scan" method (QS-EC2). Cases of existing bridges are studied with the previously used QS-VBC as well as with the QS-EC2 that includes the recommendations. As a result of the assumed transverse load distribution, the shear stress to be considered at the support based on the recommendations becomes smaller.
The Journal of Engineering Research, 2016
Approach slabs are reinforced concrete slabs used to provide a smooth transition between the bridge deck and the adjacent paved roadway. Their function is to eliminate or minimize the effects of any differential settlement between the bridge abutment and the approach roadway fill. A two-dimensional nonlinear finite element parametric study was conducted to investigate the effects of several parameters on the behavior of bridge approach slabs. The parameters used have been identified from both a literature review and a survey of state transportation departments. The parameters are the length and thickness of the approach slab; type of connection between the approach slab and the abutment; and height and density of the embankment. The paper presents the results of the parametric study that relate the effects of these parameters on the stresses and settlements developed in the approach slabs. It also provides recommendations for minimum length and thickness of bridge approach slabs bas...
Parapet Stiffness Effect on Load Carrying Capacity of Multi-Lane Concrete Slab Bridges
Proceedings of International Structural Engineering and Construction, 2020
Bridge specifications do not consider the effect of parapet stiffness in the analysis and design of reinforced concrete slab bridges. This paper performs a parametric investigation using finite element analysis (FEA) to study the effects of parapet stiffness on live load-carrying capacity of two-span, three-and four-lane concrete slab bridges. This study analyzed 96 highway bridge cases with varied parameters such as span-length, bridge width, and parapet stiffness within practical ranges. Reinforced concrete parapets or railings, built integrally with the bridge deck, were placed on one and/or both sides of bridge deck. The longitudinal bending moments calculated using the FEA results were compared with reference bridge cases without parapets, as well as AASHTO Standard and LRFD specifications. The FEA results presented in this paper showed that the presence of concrete parapets reduces the negative bending moments by 15% to 60% and the positive bending moments by 10% to 45%. The r...