Creep in Precast-Concrete Sandwich Panels Made with Diagonal-Bar Shear Connectors

Abstract

This paper aims to investigate and explain the influence of creep of concrete, insulation, and diagonal bars on the behavior of precast-concrete sandwich panels. A theoretical model is developed based on a layered structural modeling of the panel. Each reinforced concrete layer is modeled as an Euler-Bernoulli beam, and the insulation layer is modeled as two-dimensional linear viscoelastic continuum. For the analysis, the panel is divided into a number of regions through its length, and the diagonal bars are introduced via continuity requirements between different regions. Each region along the panel is divided into a number of layers in order to account for cracking, tension-stiffening, and different creep responses of each material point. Creep is accounted for using a convolution integral based on the modified principle of superposition that accounts for the material nonlinearity in tension. From the expansion of the relaxation moduli into a Prony series, an incremental exponential law is obtained, and a step-by-step time analysis was conducted. The results provide insight into the main parameters that control the creep response of composite concrete sandwich panels and provide a basis for the design and analysis of their time-dependent response.