Stress computation methods for hybrid inorganic phosphate cement-concrete cross-section

After more than 10 years of study, researchers at the Vrije Universiteit Brussel have developed a new non-alkaline mineral polymer named inorganic phosphate cement (IPC). This ceramic is reinforced by glass fibres in order to increase the toughness, the tensile strength and the stiffness of the resulting composite material. This new material is combined with a traditional material such as concrete to result in a new concept of bridge cross-section. The deck is made of concrete and the box girder is made of IPC sandwich panels. This paper presents two stress calculation models regarding the mechanical behaviour of hybrid IPC-concrete elements. The first considers the bilinear tensile behaviour of the IPC material. The second constitutive model simplifies the bilinear behaviour of the material by an equivalent linear behaviour. Comparison of the two calculation models shows that approximation of the complex behaviour of the IPC composite by an equivalent linear behaviour induces limited errors on the maximal normal stresses and deflection values. Therefore, the equivalent linear method is an easy way to determine the parameters necessary for the first global design at the ultimate limit state and serviceability limit state of the structure. Moreover, this method is safe, and therefore is appropriate for determining the dimensions of a hybrid IPC-concrete structure in the preliminary design stage.