Stochastic strength prediction of masonry structures: a methodological approach or a way forward?

Today, there are several computational models to predict the mechanical behaviour of masonry structures subjected to external loading. Such models require the input of material parameters to describe the mechanical behaviour and strength of masonry constructions. Although such masonry material parameters are characterised by stochastic-probabilistic nature, engineers are assigning the same material properties throughout the structure to be analysed. The aim of this paper is to propose a methodology which considers material spatial variability and stochastic strength prediction for masonry structures. The methodology is illustrated on a case study covering the in-plane behaviour of a low bond strength masonry wall panel containing an opening. A 2D non-linear computational model based on the Discrete Element Method (DEM) is used. The computational results are compared against those obtained from the experimental findings in terms of failure mode and structural capacity. It is shown that computational models which consider the spatial variability of masonry material properties better predict the load carrying capacity, stiffness and failure mode of the masonry structures. These observations provide new insights into structural behaviour of masonry constructions and lead to suggestions for improving assessment techniques for masonry structures

On the mechanical behavior of masonry

In this chapter, a review on the mechanical behaviour of masonry is presented. The aim is to establish a base of knowledge and understanding of masonry that will underpin its mechanical characteristics and will inform the decisions towards the selection of the computational tool used which are going to be described in the following chapters. Initially, a brief description of the factors that influence the mechanical response of masonry and the variation of the material properties are discussed. The review then considers the possible causes of cracking in masonry and the different failure modes that may occur during loading. Principal findings from the review are summarised at the end of the chapter

Numerical Analysis of the Dynamic Responses of Multistory Structures Equipped with Tuned Liquid Dampers Considering Fluid-Structure Interactions

Aims: The paper analyzes the effectiveness of tuned liquid damper in controlling the vibration of high rise building. The new contribution is considering the fluid-structure interaction of a water tank as a Tuned Liquid Dampers (TLD). Background: Currently, buildings are being built higher and higher, which requires TLDs to be larger as well. Therefore, the fluid pressure acting on the tank wall is more significant. In previous studies of liquid sloshing in TLDs, researchers simply ignored the effect of liquid pressure acting on the tank walls by making the assumption that the tanks are rigid. Currently, the failure of a tank because of FSI occurs regularly, so this phenomenon cannot be ignored when designing the tanks in general and TLDs in particular. Objective: To investigate the thickness of the tank wall affect to the TLD mechanism. Method: Numerical method was used for this research. Results: A TLD could be easy to design; however one could not bypass the fluid-structure interaction by assuming the tank wall is rigid. Conclusion: This kind of damper is very good to mitigate the dynamic response of structrure

Comparison of experimental and analytically predicted out-of-plane behavior of framed-masonry walls containing openings

During an earthquake, structures are loaded in both in-plane and out-of-plane direction. This paper investigates the behaviour of load-bearing frames with infill walls that contain openings. As when they are subjected to out-of-plane, inertial loads. In the experimental campaigns of like structures, it was found that even with openings, the beneficial arching-action was able to develop. However, its effectiveness was limited. Namely, the deformation capabilities in all cases were significantly lowered. Same can not be stated for the load-bearing capacities, as some researches found no reduction while others did. Additionally, this paper analyses the existing equations that can calculate the load-bearing capacity of such structures. Low correlations were found between the experimental and analytical capacities. Hence, further research endeavours should be addressed in order to gain a reliable analytical model

Image2DEM: A geometrical digital twin generator for the detailed structural analysis of existing masonry infrastructure stock

Assessing the structural performance of ageing masonry infrastructure is a complex task. Geometric characteristics and the presence of damage in masonry structures may influence greatly their rate of degradation and in-service mechanical response. Therefore, identifying approaches to assess the actual structural condition of these assets is vital. In the last ten years, advances in laser scanning and photogrammetry have started to drastically change the building industry since such techniques are able to capture rapidly and remotely digital records of objects and features in points cloud and image format. However, the direct and automatic exploitation of images for use as geometry in high fidelity models for structural analysis is limited. In this framework, the aim of this paper is to present the development of a software able to fully automate the “scan to structural modelling” procedure for the efficient and accurate structural assessment of ageing masonry infrastructure. “Image2DEM” is based on Python libraries with graphical interface. The images can be captured from DSLR (Digital Single-Lens Reflex) cameras, smartphones, or drones. The image selected is then imported to the programme to detect and extract the masonry micro-geometry. The algorithm provides reliable detection using Artificial Intelligence. Convolutional Neural Networks (CNN) are used to identify the location of masonry units and cracks, with ∼96% and ∼80% accuracy, respectively. The geometry is extracted in the form of simplified lines to improve efficiency and reduce computational effort. The output is provided in DXF format for compatibility between different programmes. Finally, the geometry extracted is converted to a numerical model for structural analysis. The proposed software has the potential to revolutionize the way we assess existing masonry infrastructure in the future

The behaviour of single span stone masonry skew arches

The work reported in this paper summarises the development and results obtained from a 3D computational model, using the distinct element software 3DEC, that was used to investigate the effect of the angle of skew on the load carrying capacity of sixteen different single span stone masonry arches. The variables investigated in the research were the arch span, the span : rise ratio and the skew angle. In order to gain an understanding of the behaviour of the arches, no attempts were made to model the effects of fill, spandrel walls or any other construction details. For each model, a full width vertical line load was applied incrementally to the extrados at quarter span until collapse. At each load increment the predicted crack development and vertical deflection profile was recorded. The results are compared with similar “square” (or regular) arches in order to identify the influence of skew on the behaviour of the arches

Non-Linear Dynamic Joint Selection Strategy for Hinge Controlled Masonry Arches

Masonry arches are vulnerable to seismic actions. Over the last few years, extensive research has developed strengthening strategies and methods to resist these seismic actions. However, from such studies, it is evident that the application of reinforcement to a masonry arch is done such that its failure limit is transformed from stability to a strength. This direct transformation overlooks the intermittent stages that exist, and thus provides an incomplete picture to the potential behaviors of the system. These intermittent stages can be established through subjecting the arch to hinge control and have shown the potential to increase capacity and control failure, but the computational costs for assessing the nonlinear dynamic behavior of all potential mechanisms is high. This work presents a hinge-joint selection strategy from magnitude variations of short span non-linear dynamic loading through the two-dimensional Discrete Element Method (DEM) based software UDEC. Each voussoir of the arch was represented by a distinct block within the DEM. Mortar joints were modelled as zero thickness interfaces which can open and close. Twenty-five unique configurations of an arch with controlled hinges were developed and each was subjected to short duration seismic velocity profile with varying magnitudes. From this analysis an optimal hinge set with is identified

Irrecoverable collapse time for a fixed-hinge dry-stack arch under constant horizontal acceleration

The collapse of dry-stack masonry arches results from the transformation of a static system to a mechanical state through the development of mechanical joints. The traditional failure condition is this mechanization through the formation of four-hinges in a kinematically admissible configuration. The first-order analysis of an arche’s seismic capacity is obtained through limit analysis (LA) approaches. One approach is the equilibrium assessment of the kinematic theorem through the use of a kinematic collapse load calculator (KCLC). Utilizing a custom KCLC developed and validated from an experimental arch, with the added control of the single degree-of-freedom rotations, an analytic solution is developed between the applied acceleration and the minimum time duration required for collapse. The collapse multiplier and arch centroid data is recorded for all the admissible conditions that exist in the spatial deformation propagation. From this information, the work required to collapse the arch under kinematic equilibrium is established and utilized to decompose the static and kinematic energy contributions. The time-displacement domain is then defined from the resulting kinematic energy of the overloaded arch and used to evaluate the time where the kinematic energy exceeds the remaining work required for the loss of the kinematically admissible condition. This results in a simple analytical function linking excess static acceleration with a time limit of recovery

Numerical Investigations for Assessing the Seismic Performance of Multi-Tiered Nepalese Temples

In this study, the seismic performance of old multi-tiered temples in Nepal has been addressed using three different computational approaches, including a) linear elastic; b) nonlinear static; and c) nonlinear dynamic analyses. Also, a sensitivity study was undertaken to understand the influence of wall thickness and height of Nepalese temples on their seismic behavior. Vertical oscillating modes using the elastic response spectrum of the Nepalese Building Code were obtained using linear analysis. Nonlinear static analysis (NLSA) were implemented to obtain the load carrying capacities of different in geometry temples e.g. different thickness of central core walls and number of tiers. Additionally, nonlinear dynamic analysis (NLDA) using the Finite Element Method (FEM) were performed to evaluate the characteristic tensile damage patterns. The results comparatively indicate the weakest zones depending on wall thickness, central core slenderness, opening distribution, box-like confinement, vertical misalignment of walls and so forth. Also, the results of the NLDA affirm high vulnerability of the multi-tiered temples showing extensive cracks at relatively low peak ground accelerations. It is anticipated that outcomes of this study can help practicing engineers to understand how these structures behave when subjected to seismic loads and provide insights towards their strengthening and retrofitting