Normal concrete and ultra-high-performance concrete shrinkage and creep models: Development and Application

Abstract

Because of the excellent tensile and compressive strength and durability of ultra-high-performance concrete (UHPC), a precast UHPC tube filled with normal concrete (NC) (abbreviated as NFUT) has been proposed to accelerate structure construction, reduce maintenance cost, and enhance the bearing capacity. However, the long-term deformation of the NFUT composite column has been rarely studied. To numerically analyze the long-term deformation of the new NFUT composite column due to concrete creep and shrinkage, the individual creep and shrinkage models for the NC column and the precast UHPC tube are needed. The objective of the present research was to conduct the shrinkage and creep tests and determine the creep and shrinkage models for the NFUT structure, fitting the existing models in different codes and standards with collected test data. Results showed that the B3 model effectively simulates the creep and shrinkage of the NC column, and the modified ACI209 model is suited for the creep of the precast UHPC tube. Moreover, a finite element model (FEM) of an actual bridge using the NFUT composite piers is established to verify the proposed models and highlight the structure’s advantages. Through the FEM result comparison between the full NC and NFUT composite piers, the maximal vertical deformation of the pier top is reduced by 56.6%, and the average NC stress at the pier bottom is reduced by 19.9% due to the 10-year shrinkage and creep in the composite piers. The NFUT piers significantly reduce the midspan vertical deformation and side-span rotations around the transverse direction, while its effect on the key cross-sectional normal stresses of the main girder is small.