NONLINEAR FINITE ELEMENT CONTINUUM MACRO-MODELLING OF ADOBE MASONRY - CALIBRATION AND VALIDATION USING EXPERIMENTAL RESULTS

Abstract eng:
Adobe structures are encountered in almost every region of the world and constitute a significant feature of the international architectural heritage. Despite its broad historic use, experience has shown that unreinforced adobe masonry construction has rather poor response to dynamic loading and is prone to seismic damage. This implies that there is an imminent need for protecting existing earthen buildings from the destructive effects of earthquakes. Currently, the application of detailed/formal engineering procedures in the appraisal of mud-brick structures and the assessment of retrofitting measures is hindered, among others, by the absence of established computational methods that would account for the specific characteristics of unfired earth masonry. Although over the last few decades the numerical modeling of conventional masonry construction has been studied in considerable depth, adobe masonry has generally received much less attention. This is possibly due to its intrinsic complexity that derives from the natural inhomogeneity and randomness of earthen materials. Hence, the various constitutive models that have been developed for the numerical analysis of masonry have not been adequately studied and adjusted in the context of earthen construction. Furthermore, the applicability of the Finite Element (FE) method in the structural evaluation of adobe masonry has only recently started to be seriously investigated and very limited attempts have been made so far for calibrating and validating numerical models based on outcomes of laboratory tests and field observations. The current paper examines the use of nonlinear FE continuum macro-models for assessing the structural behavior of adobe masonry. Within this framework, experimental results obtained by testing two structural configurations at the Structures Laboratory of the University of Cyprus are used to calibrate and validate the developed nonlinear FE modelling approach of adobe masonry. The first configuration is a square running bond adobe wallette confined within a specially designed steel frame, which was subjected to diagonal compression, in order to examine the shear resistance of adobe masonry. The second configuration is a complete 3D 1:2 scaled model of an existing traditional adobe building, which was constructed at the laboratory and tested through the imposition of monotonously increasing lateral forces. Detailed FE models of the tested structures are hereby developed and used for performing nonlinear numerical analyses. For the formulation of the FE models, appropriate constitutive laws for the numerical simulation of load-bearing masonry behavior are adopted and calibrated. Experimental material data and matching of numerical-experimental results are used to determine the input parameters required (i.e. modulus of elasticity, compressive behavior, tensile behavior, etc.). The computational results derived are presented and compared against the outcomes of the corresponding laboratory tests. Useful conclusions regarding the ability of the proposed models to predict damage distribution, load-bearing ability and deformation capacity are thus deduced. Additionally, the factors critically affecting the FE simulation of earthen construction are identified.

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