•Combination of unreinforced masonry structural logic and 3D-concrete printing.•Form-finding loop with Thrust Network Analysis and Discrete Element Modelling method.•Application of Discrete Element ...Modelling and Finite Element Modelling to assess global and local structural behaviour.•3D-concrete-printed components as primary structural elements with layers oriented perpendicular to the compressive flow of forces.•Dry-assembled unreinforced concrete masonry structure with a clear separation of the different materials enhancing the circularity of the structural system.•Computational pipeline for the design of 3DCP unreinforced masonry structures.
This paper describes the structural design and engineering of “Striatus”, a 3D-concrete-printed unreinforced masonry pedestrian bridge built in Venice in 2021 as part of the Time Space Existence exhibition organised by the European Cultural Centre. The project combines the latest developments in 3D concrete printing with the structural principles of historic unreinforced masonry. Typically, the structural applications of 3D concrete printing are limited to elements such as columns and walls loaded vertically, perpendicularly to the horizontal printing layers, to formwork elements or secondary structural elements. Indeed, fabrication constraints, delamination issues and the low tensile strength of the concrete have been seen as limiting factors to 3D concrete printing for structural applications demanding resistance to bending or predominant loading directions not perpendicular to the printing layers. By using unreinforced-masonry structural principles, this paper shows that structural elements spanning space horizontally, such as a pedestrian bridge, can be built by using the 3D concrete printing components as the main structure, working only in compression, loaded perpendicularly to the printed layers. Furthermore, as a compression-only structure following masonry principles, Striatus enabled the use of unreinforced concrete without any mechanical or chemical connections between the elements and the separation of concrete and steel, only used for the supports and to equilibrate the horizontal thrust of the arch effect through the tension ties. This work shows how the application of unreinforced masonry principles to 3D concrete printing offers new opportunities in terms of structural design and represents a strategy to increase sustainability by reducing material consumption and allowing reusability and recyclability of the structure. Finally, this paper discusses the critical aspects related to the design of Striatus from an engineering and construction point of view.
Although mainland Portugal has been spared from large magnitude earthquakes in recent years, it faces a threat due to its position in relation to faults system. In such a framework, Portuguese ...masonry construction is believed to be the most vulnerable in the existing building stock. Given the lack of information on earthquake damage to this stock, the use of detailed numerical models is a viable strategy to comprehend its seismic behavior.
This paper provides an updated fragility characterization of Lisbon pre-code masonry buildings based on their mechanical seismic assessment, performed through the Applied Element Method. To limit the computational time, a promising pushover strategy, known as Incremental Ground Acceleration, was adopted. After the characterization of the current fragility, two retrofit layouts based on piers strengthening were modeled and assessed for the building stock whose seismic capacity does not meet expected demand. The aim of the paper is to derive updated fragility curves for the Lisbon region to support risk studies incorporating the latest hazard studies and to offer insights into potential retrofit interventions.
•Incremental Ground Accelerations to estimate the seismic capacity of representative pre-code buildings in Lisbon (Portugal)•Analytical-numerical seismic fragility curves for the Lisbon region incorporating the recent hazard studies•Integration of fragility curves with the retrofit to support risk studies
•This study proposes fragility surfaces for post-earthquake damage states identification of unreinforced masonry shear walls using visual features of cracking and crushing.•A new methodology entitled ...the Box-counting method is introduced to generate 3D fragility surfaces based on visual characteristics of surface damages.•The reconnaissance teams can use the proposed 3D fragility surface for the damage state identification and loss estimation using post-earthquake visual damage features.•The 3D damage surfaces are formulated using Decision Tree regression learners.
This paper introduces a novel methodology for identifying the post-earthquake damage states of unreinforced masonry walls using visual damage features. Current guidelines provide a qualitative description of surface cracking and crushing to determine the damage states. However, evaluating the damage states according to the qualitative damage description is highly affected by the experience and judgment of the inspector. Therefore, the present study quantifies the qualitative description of guidelines to measure the probability of reaching different damage states using 3D fragility surfaces. To this end, 333 images of 168 damaged unreinforced masonry walls at different drift ratios between 0.0 and 2.5 percent are collected, and the magnitude of cracking and crushing are measured. Three image processing filters are employed to measure various types of cracking and crushing areas, which are the main characteristics described by the guideline for damage state identification. Then, a new methodology for generating the 3D fragility surface, entitled the Box-counting method, is introduced to study the influence of cracking and crushing on the damage states. The fragility surfaces are developed using the information on crack pattern length and crushing areas that enable determining the damage states of the masonry walls just by looking at the surface damages. The Tree-based machine learning regression learners are also employed to formulate the 3D fragility surface. The proposed framework of this paper can be used for risk assessment of unreinforced masonry walls and is a reliable basis for generating multi-variable 3D fragility surfaces.
•The response of the façade’s models strongly vary depending on the applied settlement shape.•The damage of the facades’ models is assessed objectively using a purposely defined parameter that ...represents number, length and width of cracks in a single scalar value.•The Façades with an L/H smaller or equal than 1.00 or resting on reinforced concrete foundations are the least vulnerable.•The soil-foundation interaction was observed to influence the development of the damage and the ratio between applied settlements and the façade’s distortions.
This study aims to investigate the damage response of unreinforced masonry (URM) façades resting on strip foundations and subjected to ground settlements via numerical models. The models depict the non-linear constitutive behaviour of both the masonry, via smeared cracking, and of the soil-foundation interaction, via nonlinear interface elements. The influence of building features, such as the masonry material, the length over height (L/H) ratio of the geometry, the wall thickness, the number and size of openings and different types of strip foundations (i.e. reinforced concrete and unreinforced) is examined. A sensitivity study additionally investigates the influence of the interface stiffness and its constitutive model. A Gaussian curve is used to replicate the shape of the ground settlements; These simulate the loss of support underneath the foundation due to urban subsidence. Eight settlement shapes are applied in the FE models, including both symmetric and asymmetric profiles, while the angular distortion is used to measure their intensity. A new aspect is that the extent of the induced damage to the façade is assessed objectively using a damage parameter that represents the number, length and width of cracks in a single scalar value. The method distinguishes between the applied settlement profile at the bottom of the interface and the retrieved settlement profile measured on the façade. The analyses indicate that for a value of the angular distortion equal to 2 ‰ (or 1/500), computed from the resulting deformations of the façades, 60% of the models exhibit serviceability damage associated with cracks of about 5 mm width. Accordingly, the limit values available in the literature are observed to be too optimistic and not conservative in relation to the analyses presented in this study. A key outcome is that facades with an L/H smaller or equal to 1 do not exhibit cracks wider than 1 mm. Façades on reinforced concrete foundations were observed to be less susceptible to settlement damage, compared to unreinforced ones.
This paper introduces novel analysis procedures for the structural assessment of masonry earth retaining structures subjected to traffic loading. Given their substantial presence, particularly in ...transportation networks of historical cities, and the challenges posed by ageing, deterioration, and exposure to loads beyond their original design considerations, this research highlights the necessity of accounting for potential load redistribution mechanisms during their assessment. This can prevent overly conservative interventions that may not be necessary and also contravene sustainability and heritage preservation principles. Four distinct analysis procedures – 2D monotonic, 3D monotonic, 3D static moving load and 3D dynamic moving load – are developed, each progressively more refined than its predecessor in capturing potential load redistribution mechanisms in masonry earth retaining structures. These mechanisms may develop due to the dynamic loading conditions of the vehicular passage, the 3D structural configuration of retaining structures, and non-linear material behaviour. By comparing the structural capacity evaluated using the four procedures, contributions from different sources of load redistribution can be separately quantified, aiding in the reduction of conservatism inherent in less refined assessment procedures. The application of the developed procedures and consequent quantification of load redistribution is demonstrated through a case study of an existing masonry retaining structure in Amsterdam, the Netherlands.
•Analysis procedures for masonry earth retaining structures under traffic loading.•2D monotonic, 3D monotonic, 3D static and 3D dynamic moving load procedures.•Load redistribution is due to dynamic loading and 3D structural configuration.•Demonstrated application to a case study in Amsterdam, the Netherlands.
In this study, a novel computational modeling strategy is proposed to estimate the lateral load capacity and behavior of unreinforced masonry (URM) structures. All commonly noted failure mechanisms ...are captured via the proposed modeling strategy using the discrete element method (DEM) in three-dimensions (3D). Masonry walls are represented as a system of elastic discrete blocks, where the nodal velocities are evaluated by integrating the equations of motion using the central difference method. Then, the mechanical interactions among adjacent blocks are examined utilizing the relative contact displacements and employed in the contact stress calculation. Through this research, a new stress-displacement contact constitutive model is considered and implemented in the commercial software 3DEC, which includes softening stress-displacement behavior for tension, shear, and compression along with the fracture energy concept. The results of the discontinuum models are validated on small- and large-scale experimental studies available in the literature with good agreement. Furthermore, important inferences are made regarding the effect of block size, the number of contact points, and contact stiffness values for robust and accurate simulations of masonry walls.
A test programme consisting of four half-scale URM walls was conducted under quasi-static cyclic loading to evaluate the negative influence of openings. Test results showed that the masonry adjacent ...to the opening experienced significant damage, and the specimens with a door opening was found to have complete detachment of the masonry pier, resulting in a reduction in the capacity of more than 25%. Furthermore, a detailed parametric nonlinear finite element analysis was performed to assess the influence of parameters affecting the in-plane load capacity of the URM wall. Numerical results showed that depending upon the size and location of openings and the material and geometric properties of walls, the in-plane load capacity was reduced by 6–82%. Considering the results of available experimental studies and present numerical analyses, a simplified equation was proposed to estimate the reduction in the in-plane load capacity of the specimen with different types of openings. The analytical study demonstrated that the proposed equation effectively provided reliable and consistent predictions of the strength reduction factor for walls with different types of openings.
•Assess opening’s effect on lateral load capacity of masonry wall via cyclic test.•Effect of various parameters on in-plane strength reduction using FE simulations.•Size and position of opening in walls significantly affect in-plane load capacity.•Develop a simplified relation to estimate strength reduction for opening in walls.
•An experimental database including lots of unreinforced masonry wall test data is assembled.•A parameter calibration method that distinguishes in-cycle and cyclic deterioration behaviors is ...built.•The simplified model achieves reasonable estimation of failure behaviors under different loading patterns.
Unreinforced masonry, including non-confined unreinforced masonry (NCURM) and confined unreinforced masonry (CURM), constitutes a significant portion of low-rise buildings and is prone to collapse due to high seismic vulnerability. Seismic collapse performance prediction is an effective method to reduce structural collapse, and it requires the analytical model that can correctly simulate structural mechanical behaviors, especially for the deterioration behaviors from accumulation damage. Macro-scale structural models constructed based on hysteretic models of walls have small computational efforts compared to micro-scale finite element models, and are preferred for structural seismic collapse performance analysis. However, existing hysteretic models of NCURM wall and CURM wall lack accuracy in considering the deterioration behaviors due to incorrect model forms or lack of available model parameter values. In this study, an experimental database consisting of cyclic tests on 47 NCURM walls and 50 CURM walls is assembled based on the existing literature. The hysteretic models of NCURM wall and CURM wall are developed by the combined use of the assembled database and the Ibarra-Krawinkler (IK) model from Ibarra et al. The IK model has versatile consideration of the in-cycle and cyclic deterioration behaviors and is used for the modeling of walls. A calibration procedure that clearly distinguishes the in-cycle and cyclic deterioration behaviors is established, and the model parameters of test walls in the database are calibrated. By regression analyses of calibration results, a set of empirical equations are created for determining model parameters. To satisfy the seismic collapse performance analysis of regional masonry buildings, the multi-degree-of-freedom (MDOF) shear model of masonry structure is further given based on the wall hysteretic model, which is constructed by the structural inter-story mechanical behaviors and has very small computational efforts. Good accuracy of both wall hysteretic model and structural MDOF shear model is verified by the comparisons with experimental and numerical results.
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