1,721,021 research outputs found
The Influence of Geometry on the Frictional Sliding of ∧ and ∨ Shaped Interlocking Joints in Masonry Assemblages
No full textApplications of interlocking blocks improving the sliding resistance of masonry joints have recently been of significant interest to architects and structural engineers. In this framework, several works have studied the load capacity improvement of different joint shapes using various numerical and experimental analyses. However, applications of simplified and yet accurate analytical methods like limit analysis to interlocking blocks are rather unexplored and limited to a few interlocking joint shapes. To develop such a simplified analytical approach for interlocking assemblages with ∧ and ∨ shaped joints, this paper explores relationships between the shear capacities of flat and interlocking joints, allowing to abstract an assemblage of interlocking blocks to its equivalent assemblage with flat joints. This work specifically studies the interaction among friction, dilation, and inclination angles of the joints. To this aim, first the relationships between a flat and an interlocking joint of two stacked blocks are fully explored and then, the associative solution for an assemblage of two wedge blocks with flat faces is compared with the non-associative solution of the same assemblage with ∧ and ∨ shaped interlocking joints. Discrete element models using 3DEC are implemented to carry out the comparative analyses, in which the blocks are modelled as rigid units and the ultimate lateral load capacity of the assemblages is recorded
Interlocking joint shape optimization for structurally informed design of block assemblages
No full textThis paper presents a computer aided design tool that analyses the structural feasibility of interlocking assemblages with orthotropic sliding resistance and automatically adjusts the assemblage shape to remove the infeasibility. First, the static problem of limit analysis is extended to the corrugated interfaces. To model different bond patterns and openings, an assemblage is abstracted to different types of joints representing the dry joints between the blocks, joints inside the blocks, and the excluded joints where the openings are located. This problem is then reformulated to measure the structural infeasibility due to the sliding constraint violation. The so-called sliding infeasibility measure shows how far an infeasible model is to become feasible. This problem is used as the objective function of a shape optimization algorithm that minimizes the sliding infeasibility measure through automated change of the interlocking joints, by which the model becomes structurally feasible. The optimization is validated using the discrete element analysis
Discrete macro - models of nonlinear interlocking mechanisms in the out-of-plane failure of masonry walls
No full textHistorical unreinforced masonry (URM) constructions are generally vulnerable to out-of-plane (OOP) failures due to the absence of rigid floors and poor connections between orthogonal walls. That leads to the activation of rocking mechanisms of external walls, whose ultimate force and displacement are affected by complex nonlinear interactions with sidewalls. These interactions are often neglected in the engineering practice, potentially leading to significant approximations, as demonstrated by experimental and numerical studies available in the literature. As a novel contribution to the field, this paper presents an upgraded discrete macro-element model (DMEM) to predict the rocking capacity of OOP loaded URM walls interacting with sidewalls. Considering both the onset and the evolution of the rocking mechanism of the front wall, interlocking effects with the sidewalls are first simulated through frictional resistances using the macro-block model (MBM) and the nonlinear kinematic approach of limit analysis. Then, the upgraded DMEM is implemented on the basis of the equivalence between the continuous distribution of these forces, introduced as a further novelty of the paper, and the discrete distribution of lateral elastic-plastic links, accounting for mechanical and geometrical nonlinearities. The results of the two models are discussed in terms of both frictional resistance-displacement and pushover curves, referring to a case study of a front wall belonging to a two-storey URM building. The wall response is also compared with the results derived from the original source of the case study and analysed by changing the number of nonlinear links to define different levels of accuracy
Torsion–Shear Behaviour at Interlocking Joints: Calibration of Discrete Element-Deformable Models Using Experimental and Numerical Analyses
No full textAn interlocking block is a concave polyhedron with non-planar joints connecting the blocks together. The possibility of the fracture within a masonry interlocking block is a major challenge that has remained rather unexplored yet. Different fracture scenarios can be taken into account through considering the crack planes at which the block can be set apart. The plastic failure inside the block can also be represented through the continuum plastic deformation of the block composed of continuum finite elements. For an interlocking block with a cuboid projection above (lock), this paper intends to analyse the torsion–shear behaviour of the lock experimentally and numerically based on the discrete element method. Two strategies are developed to model a concave block: the lock and main body of an interlocking block are set to be rigid and connected with a cohesive contact in between; the concave interlocking polyhedron is set to be deformable with elasto-plastic behaviour. Given the same material properties, the torsion–shear capacities of the lock obtained by the two numerical models and the experimental test are compared to each other. A parametric analysis is then provided to calibrate the deformable model
Quantifiable feasibility check of masonry assemblages composed of interlocking blocks
No full textThis paper introduces a digital tool to quantify the structural feasibility of single layer assemblages of interlocking blocks. These have corrugated faces to keep the blocks together and prevent them from sliding through the frictional and shear resistances of the locks in two orthogonal directions. Calling the sliding constraint violation of an equilibrated model "sliding infeasibility", it is measured as a numerical value, named sliding infeasibility measure (SIM). The designer, instead of removing the infeasibility by trial and error, can adjust the assemblage geometric parameters to minimise the SIM. To this aim, first the structural soundness of an assemblage is investigated through the equilibrium analysis accounting for two sliding behaviours. This method is validated by comparing some thinnest feasible models with conventional blocks existing in the literature and the same models with interlocking blocks. Then, as the core of this paper, the equilibrium analysis is reformulated to develop an optimization problem aimed at quantifying and minimising the SIM. Rearranging the sliding constraints, the tool measures the tangential internal forces violating the sliding valid range as the SIM. Since more than one solution can exist for an equilibrated tensionless model with sliding infeasibility, this problem finds the solution for which the tangential forces are the closest to the valid sliding ranges. The method is validated by comparing the SIM to the structural soundness of assemblages with different interface geometric properties. Finally, the tool performance to design shells with arbitrary shapes is demonstrated through several examples
Discrete rotating links model for the nonlinear torsion-shear behaviour of masonry joints
No full textThe numerical modelling of the torsion behaviour of masonry block interfaces is a key aspect for the assessment of the out-of-plane response of masonry walls. Nevertheless, it still represents a challenging computational issue due to the high non-linear coupling between the torsion and other internal forces (shear, bending moment and axial load), which rigorously requires the adoption of complex 3D non-linear constitutive laws. Some limit analysis-based approaches, proposed in the specific literature, represent efficient and reliable numerical tools for predicting the ultimate states of brick masonry structures subjected to combined in-plane and out-of-plane actions, while involving complex torsion loads and combined actions. This paper originally introduces a simplified discrete inelastic interface able to simulate the non-linear torsion-shear behaviour of masonry contact joints, within the context of static incremental analysis. The more general mechanical behaviour of the interface is ruled by six degrees of freedom and is governed by four rotating links (RL), whose actual orientation is updated during the step by step analysis, by taking into account the current position of the twisting centre of the interface. The incremental torsion-shear capacity curve and the corresponding ultimate domains obtained by the proposed model are compared with the ultimate load limit analysis predictions and with some experimental data available in the literature. The results highlight the ability of the new discrete interface to effectively reproduce the full non-linear behaviour of masonry contact interface subjected to different loading combinations
Environmental and economic impact of retrofitting techniques to prevent out‐of‐plane failure modes of unreinforced masonry buildings
Full text linkThis paper presents an innovative methodology to assess the economic and environmental impact of integrated interventions, namely solutions that improve both structural and energy performance of existing masonry buildings, preventing out‐of‐plane modes and increasing their energy efficiency. The procedure allows the assessment of the environmental and the economic normalized costs of each integrated intervention, considering seismic and energy‐saving indicators. In addition, the work introduces in relative or absolute terms two original indicators, associated with seismic displacement and thermal transmittance. The iso‐cost curves so derived are thus a powerful tool to compare alternative solutions, aiming to identify the most advantageous one. In fact, iso‐cost curves can be used with a twofold objective: to determine the optimal integrated intervention associated with a given economic/environmental impact, or, as an alternative, to derive the pairs of seismic and energy performance indicators associated with a given budget. The analysis of a somehow relevant case study reveals that small energy savings could imply excessive environmental impacts, disproportionally increasing the carbon footprint characterizing each intervention. Iso‐cost curves in terms of absolute indicators are more suitable for assessing the effects of varying acceleration demands on a given building, while iso‐cost curves in terms of relative indicators are more readable to consider a plurality of cases, located in different sites. The promising results confirm the effec-tiveness of the proposed method, stimulating further studies
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