Nima Khorsandnia

Experimental Investigations of Deconstructable Timber–Concrete Composite Beams

AbstractIn conventional timber–concrete composite (TCC) beams, timber joists and concrete slabs are connected permanently; however, the permanent timber–concrete connections can hinder repairing and reusing of structural components and accordingly it reduces the sustainability of construction. This paper deals with development and structural performance of a few novel deconstructable TCC connections that can facilitate recycling and reusing of construction materials. The structural performance of 16 different sets of novel deconstructable TCC connections under shear loads is investigated by push-out tests followed by bending tests on nine TCC beams under service and ultimate loads. The behavior of connections and beams are characterized and the TCC connections with the highest strength and stiffness and feasibility for construction and dismantling are identified.

Structural Response of Timber-Concrete Composite Beams Predicted by Finite Element Models and Manual Calculations

This paper presents the structural response of timber-concrete composite (TCC) beams predicted by finite element models (i.e. continuum-based and 1D frame) and manual calculations. Details of constitutive laws adopted for modelling timber and concrete are provided and application of the Hashin damage model in conjunction with continuum-based FE for capturing failure of timber under bi-axial stress state is discussed. A simplified strategy for modelling the TCC connection is proposed in which the connection is modelled by a nonlinear spring and the full load-slip behaviour of each TCC connection is expressed with a formula that can be directly implemented in the general purpose FE codes and used for nonlinear analysis of TCC beams. The developed FE models are verified by examples taken from the literature. Furthermore, the load-displacement response and ultimate loading capacity of the TCC beams are determined according to Eurocode 5 method and compared with FE model predictions.

Numerical modelling of timber/timber–concrete composite frames with ductile jointed connection

Due to the scarcity of experimental data, this article focuses on the application of detailed finite element models for evaluating structural behaviour of timber–concrete composite frames with post-tensioned beam-to-column joints. In the developed finite element models, nonlinear behaviour and failure mode of timber and concrete under biaxial stress state are captured by hypo-elastic constitutive laws based on the equivalent uniaxial strain concept. In addition to material nonlinearities, the effect of geometrical nonlinearities and nonlinearity of contacts at the concrete slab-to-beam, beam-to-column and slab-to-column interfaces are considered in the finite element models. The accuracy of developed finite element models is verified against available experimental data on post-tensioned timber frames, and the validated analytical tool is used to undertake a parametric study. It is shown that elastic modulus of timber and the details of concrete slab-to-column connection can significantly affect the drift response and failure mode, whereas the compressive strength of timber and stiffness of timber–concrete composite connection have only a minor influence on the drift and failure mode of the timber/timber–concrete composite frames with ductile jointed connections.

Application of quasi-brittle material model for analysis of timber members

Abstract Over the last two decades many constitutive models with different degrees of accuracy have been developed for analysis of sawn timber and engineered wood products. However, most of the existing models for analysis of timber members are not particularly practical to implement, owing to the large number of material properties (and associated testing) required for calibration of the constitutive law. In order to overcome this limitation, this paper presents details of 1D, 2D and 3D non-linear finite element (FE) models that take advantage of a quasi-brittle material model, requiring a minimum number of material properties to capture the load-deflection response and failure load of timber beams under 4-point bending. In order to validate the model, four tapered timber piles with circular cross-section (two plains and two retrofitted with steel jacket) were tested and analysed with the proposed 3D FE modelling technique; and a good correlation between experimentally observed and numerically captured ultimate load was observed. Consequently, it was concluded that the developed FE models used in conjunction with the quasi-brittle constitutive law were able to adequately capture the failure load and load-deflection response of the flexural timber elements.

Nonlinear Long-Term Analysis of Timber-Concrete Composite Structures with Finite Element-Finite Difference Scheme

Long-term analysis of timber-concrete composite (TCC) structures is a challenging task owing to the time-dependent behaviour of timber, concrete and connections which are highly nonlinear under variable environmental conditions (i.e. temperature, humidity). In this paper an efficient numerical method that takes advantage of a finite element-finite difference (FE-FD) scheme is presented. The differential equations governing the long-term behaviour of TCC section under variable humidity are solved using the FD scheme and the differential equations governing the mechanical behaviour of the composite beam are solved by a FE formulation recast in the framework of force-interpolation concept. The comparison between experimental data and numerical results shows the sufficient accuracy of the proposed FE-FD model for capturing long-term behaviour of TCC members.