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This paper presents an iterative sandwich beam theory (ISBT) and a simplified version suitable for the design termed simplified sandwich beam theory (SSBT) used to predict the elastic mechanics of partially composite insulated concrete sandwich wall panels (SWPs) under flexural, axial, and thermal loads. These solution methods expand upon closed-form solutions to create a more general analysis technique. Design and analysis of SWPs are handled largely outside of codified documents and are almost exclusively designed such that they will remain within the elastic range. The presented ISBT and SSBT methods have been used in the United States precast industry since 2017 and are implemented in widely available software, LECWall, as of 2020, for predicting elastic deflections and stresses. In this paper, the ISBT and SSBT solution methods are validated with experimental data from the literature and using finite-element analysis. For the ISBT cracking moment and deflection, the measured-to-predicted ratio were 0.99 and 1.0 with coefficients of variation (COVs) of 0.10 and 0.11, respectively. For the SSBT cracking moment and deflection, the measured-to-predicted ratio was 0.99 and 0.99 with COVs of 0.21 and 0.19, respectively. For thermal loading, the ISBT and SSBT deflection m easured-to-predicted ratios were 0.95 and 0.90, respectively. The model was then used to investigate the behavior of sandwich wall panels under varying load combinations and with various section and material properties to demonstrate the robustness of the presented methods. [ABSTRACT FROM AUTHOR]

Highlights • Relatively linear response with intermediate anisotropy levels within elastic region. • Insignificant creep for both vertically- and horizontally-drilled specimens. • High failure strength at both unconfined and in-situ stress levels. • Significant anisotropy effects for seismic velocities, particularly during isotropic compression stages. • Substantial change in the dominant frequency of the transmitted seismic waves with confining stress. Abstract Geothermal energy is the heat contained in rock and fluid in the earth's crust. In some areas the geothermal resource can be exploited by drilling wells to extract the heated fluids and piping the fluids to a power plant to generate renewable electricity. Geomechanical characterization of the rocks in geothermal reservoirs is necessary to (i) optimize a well stimulation program, (ii) reduce production decline, and (iii) build more accurate predictive models at reservoir scale. In this study, we present the results of a suite of experiments on mechanical characterization of phyllite rock specimens retrieved from DB-2 well (depth of 1260 m) at the Blue Mountain geothermal field in Nevada, United States. In order to investigate the effects of anisotropy on mechanical response of rock, one vertically-drilled and one horizontally-drilled sub-cores were extracted from the phyllite core. Multi-stage elastic, cyclic, creep, and multi-stage failure tests were performed to characterize the elastic, plastic, time-dependent, and failure properties as well as effects of anisotropy on the behavior of the phyllite specimens. The pressure-dependent static and dynamic moduli revealed that within the elastic region, the Young's modulus increased with the increment of differential stress during the loading stage. While, 10% to 50% difference between the elastic moduli of the two specimens confirmed the anisotropic nature of the material. Negligible creep response was observed in both specimens, with a more pronounced change in P- and S-waves velocities during hydrostatic stage for vertically-drilled sub-core. The failure envelope, developed using the multi-stage failure test on the vertically-drilled specimen, indicated good agreement with both Linearized Mohr-Coulomb and Hoek-Brown failure criteria. On the other hand, significant changes were observed in the time-frequency maps of the transmitted seismic waves during multi-stage elastic test (i.e. change in confining level), however, slight changes in the time-frequency map were observed during creep test (i.e. application of differential stress for a relatively long period). [ABSTRACT FROM AUTHOR]