Proceedings of the Institution of Civil Engineers Structures & Buildings 160 January 2004 Issue SB1 Pages 1–9 Paper 13259 Received ??? Accepted ??? Keywords: building structure & design/ composite structures/slabs & plates L. M. Bozzo Polytechnic School, University of Girona L. Torres Polytechnic School, University of Girona PROOFS A proposed semi-prefabricated prestressed composite steel–concrete slab L. M. Bozzo and L. Torres This paper presents a semi-prefabricated prestressed composite slab, including experimental testing and appropriate numerical simulation tools, additioanlly design guidelines and a parametric study of the main variables. The system was applied for the first time in Spain during the construction of the library of the ‘University of Lleida’ covering 12 3 12 m spans with only 300 mm (L/40) total depth. This system considerably reduces the in situ work compared with other methods, allowing for large spans and two-way action. It is made up of three elements: (a) semi-prefabricated prestressed composite flat beams; (b) precast prestressed planks (namely preslabs); and (c) in situ reinforcement (transversal and negative) and topping concrete. Characterisation of element (a) using destructive experimental testing, as well as simple analytical and more precise numerical tools, using a layer model that includes constitutive equations for each material is included. A global analysis can be performed using a mixed finite element formulation including orthotropy. This last effect is important in this system, due to the different positions of the longitudinal and transversal reinforcement. INTRODUCTION Construction of composite steel–concrete structures in Spain started with the Tordera’s bridge project by E. Torroja in the 1930. The structural logic of such composite solutions is clear, which is why they are widely-used and have undergone constant redevelopment. Analytical solutions for this type of beam have been available for many years. Nevertheless, in spite of their potential advantages there are very few composite steel–concrete slab structures, as well as very few precast two-way slabs. When compared to linear systems the advantages of a two-way action include: greater flexibility in column distribution; and potential reduction of total depth and construction speed. Conventional slabs suffer from such disadvantages as the considerable high self-weight and a lower resistance to seismic action. This last disadvantage arises not only from the weight increase but also from the increased propensity to column fragile punching failure. As a consequence, it is widely accepted that in zones of high seismicity systems based on waffle slabs should not be recommended and often even permitted. It is for these reasons that over the passed 30 years in Peur composite steel–concrete reticulated slabs (tridilosas) have been actively developed allowing for the coverage of 20–30 m spans with live loads of 5 kN/m 2 at 500 mm of total depth and 1 . 5 kN/m 2 of self-weight (Fig. 1). 2 At present, this system is only economically suitable in countries, such as those of Latin America, where labour is relatively inexpensive. Based on the work of Eng. M. Ollila in Finland, a prestressed semi-prefabricated composite steel–concrete slab has recently been constructed in Spain that potentially requires less in situ work in comparison to the tridilosa. A noteworthy example of a structure constructed with this novel system is the library of the University of Lleida, designed by the architects Gullichsen and Vormala. In this building, spans range from modules of 12 3 8 to 12 3 12 m, with total depths of only 300 mm. This paper describes the system, the experimental testing designed to characterise it, a numerical prediction of its long-term behaviour and examples of the influence of several parameters. The paper also contributes to ongoing development by proposing a finite element analysis method, based on the Reissner functional, which is able to simulate precisely orthotropic slab behaviour. SYSTEM DESCRIPTION The system is based on a framework of partially prefabricated (namely semi-prefabricated) prestressed composite steel– Article number = 13259 Fig. 1. Composite steel–concrete reticulated slab, Peru Structures & Buildings 160 Issue SB1 Bozzo • Torres 1 Prestressed composite steel–concrete slab