Modelling of Compressive Membrane Action for Fully-laterally Restrained Two-way R.C Slabs

Current design codes do not account for the effect of compressive membrane action (CMA) in reinforced concrete slabs, which can increase their capacities, and hence yields more economical design. This paper studies the influence of CMA for laterally restrained two-way slabs. The main aim is to develop a simple model to reasonably predict the enhancement in load-carrying capacity due to CMA for laterally restraint two-way RC slabs under uniformly distributed loading. In order to meet this aim, a numerical technique was used. The developed model had been validated against relevant experimental studies from literature. The parameters influencing the CMA were identified. These included the reinforcement ratio and span-thickness ratio. It was shown that the CMA decreases by increasing the percentage of reinforcement and span-to-thickness ratio. After that, a numerical model for evaluating the CMA for laterally restrained two-way slabs has been proposed. The model was examined against 43 slab specimens from literature. The correlation achieved was satisfactory, despite the wide range of variables involved in tests. The mean ratio of the experimental to the predicted ultimate load was 1.00, and the coefficient of variance (COV) equal to 25%.

Capacity of prestressed concrete bridge decks under fatigue loading

<p>In The Netherlands, existing slab-between-girder bridges with prestressed girders and thin transversely prestressed concrete decks require assessment. The punching capacity was studied in a previous series of experiments, showing a higher capacity thanks to compressive membrane action in the deck. Then, concerns were raised with regard to fatigue loading. To address this, two series of large-scale experiments were carried out, varying the number of loads (single wheel print versus double wheel print), the loading sequence (constant amplitude versus variable amplitude, and different loading sequences for variable amplitude), and the distance between the prestressing ducts. An S-N curve is developed for the assessment of slab-between-girder bridges. The experiments showed that compressive membrane actions enhances the capacity of thin transversely prestressed decks subjected to fatigue loading.</p>

Fatigue Assessment of Prestressed Concrete Slab-Between-Girder Bridges

In the Netherlands, the assessment of existing prestressed concrete slab-between-girder bridges has revealed that the thin, transversely prestressed slabs may be critical for static and fatigue punching when evaluated using the recently introduced Eurocodes. On the other hand, compressive membrane action increases the capacity of these slabs, and it changes the failure mode from bending to punching shear. To improve the assessment of the existing prestressed slab-between-girder bridges in the Netherlands, two 1:2 scale models of an existing bridge, i.e., the Van Brienenoord Bridge, were built in the laboratory and tested monotonically, as well as under cycles of loading. The result of these experiments revealed: (1) the static strength of the decks, which showed that compressive membrane action significantly enhanced the punching capacity, and (2) the Wöhler curve of the decks, showed that the compressive membrane action remains under fatigue loading. The experimental results could then be used in the assessment of the most critical existing slab-between-girder bridges. The outcome was that the bridge had sufficient punching capacity for static and fatigue loads and, therefore, the existing slab-between-girder bridges in the Netherlands fulfilled the code requirements for static and fatigue punching.

Fatigue Assessment of Prestressed Concrete Slab-between-Girder Bridges

In the Netherlands, the assessment of existing prestressed concrete slab-between-girder bridges showed that the thin, transversely prestressed slabs may be critical for static and fatigue punching when evaluated using the recently introduced Eurocodes. On the other hand, compressive membrane action increases the capacity of these slabs and changes the failure mode from bending to punching shear. To improve the assessment of the existing prestressed slab-between-girder bridges in the Netherlands, two 1:2 scale models of an existing bridge, the Van Brienenoord Bridge, were built in the laboratory and tested monotonically as well as under cycles of loading. The result of these experiments is: 1) the static strength of the decks, showing that compressive membrane action significantly enhances the punching capacity, and 2) the W&ouml;hler curve of the decks, showing that compressive membrane action remains under fatigue loading. The experimental results can then be used for the assessment of the most critical existing slab-between-girder bridge. The outcome is that the bridge has sufficient punching capacity for static and fatigue loads, and thus that the existing slab-between-girder bridges in the Netherlands fulfil the code requirements for static and fatigue punching.

NONLINEAR FINITE ELEMENT ANALYSIS OF TRANSVERSELY PRESTRESSED CONCRETE DECK SLABS

This paper describes the modeling and analysis procedure of a 3D, solid, nonlinear finite element (FE) model of a bridge developed in the finite element analysis software package TNO DIANA to study the structural behavior in punching shear of transversely prestressed concrete deck slabs cast between flanges of long, pretensioned girders, and compressive membrane action. The numerical research was part of a broad project involving laboratory experiments carried out on a 1:2 scale model of such a bridge in Delft University of Technology. Both the experimental and numerical results showed much higher capacities than expected and this was attributed to the development of compressive membrane action in the plane of the slab. The numerical results were then compared with the experimentally found ultimate loads of eight basic test cases and it was discovered that the nonlinear FE models can predict the load carrying capacity quite accurately with a coefficient of variation of only 11%. It was concluded that punching shear failures can be reasonably modeled with non-linear finite element analysis of 3D solid models. Furthermore, using composed elements can lead to the determination of compressive membrane forces developed in a laterally restrained slab, which was previously difficult to determine using analytical techniques.