Implementation of a new strain split to model unilateral contact within the phase field method

in International Journal for Numerical Methods in Engineering (2020)

A new orthogonal decomposition of strain tensor into compressive/tensile parts is implemented in the phase eld model to maintain the physical crack propagation behavior. An e cient operator split scheme ... [more ▼]

A new orthogonal decomposition of strain tensor into compressive/tensile parts is implemented in the phase eld model to maintain the physical crack propagation behavior. An e cient operator split scheme with the introduction of projection tensors is proposed to facilitate the numerical implementation of the new spectral decomposition. Formulations of the present failure model accounting the unilateral contact condition are given analytically and explicitly, which implies an extremely robust computational model. In particular, compared to the existing models, the present framework is general, which can be applied to all possible elastic behavior, such as isotropic, orthotropic, and totally anisotropic elastic material. A detailed comparison of fracture response predicted by the present models with the literature approaches is then provided. It is shown that orthogonal decomposition is able to simulate various failure scenarios. Especially, this formulation shows a very remarkably prediction compared to experimental observation for the case of compression load. [less ▲]

BIM-Based End-of-Lifecycle Decision Making and Digital Deconstruction: Literature Review

in Sustainability (2020), 12(7), 2670

This article is the second part of a two-part study, which explored the extent to which Building Information Modelling (BIM) is used for End-of-Lifecycle (EoL) scenario selection to minimise the ... [more ▼]

This article is the second part of a two-part study, which explored the extent to which Building Information Modelling (BIM) is used for End-of-Lifecycle (EoL) scenario selection to minimise the Construction and Demolition Waste (CDW). The conventional literature review presented here is based on the conceptual landscape that was obtained from the bibliometric and scientometric analysis in the first part of the study. Seven main academic research directions concerning the BIM-based EoL domain were found, including social and cultural factors, BIM-based Design for Deconstruction (DfD), BIM-based deconstruction, BIM-based EoL within LCA, BIM-aided waste management, Material and Component Banks (M/C Banks), off-site construction, interoperability and Industry Foundation Classes (IFC). The analysis highlights research gaps in the path of raw materials to reusable materials, i.e., from the deconstruction to M/C banks to DfD-based designs and then again to deconstruction. BIM-based EoL is suffering from a lack of a global framework. The existing solutions are based on local waste management policies and case-specific sustainability criteria selection. Another drawback of these ad hoc but well-developed BIM-based EoL prototypes is their use of specific proprietary BIM tools to support their framework. This disconnection between BIM tools and EoL tools is reportedly hindering the BIM-based EoL, while no IFC classes support the EoL phase information exchange. [less ▲]

Impact of Pile Punching on Adjacent Piles: Insights from a 3D Coupled SPH-FEM Analysis

in Applied Mechanics (2020), 1(1), 47-58

Pile punching (or driving) affects the surrounding area where piles and adjacent piles can be displaced out of their original positions, due to horizontal loads, thereby leading to hazardous outcomes ... [more ▼]

Pile punching (or driving) affects the surrounding area where piles and adjacent piles can be displaced out of their original positions, due to horizontal loads, thereby leading to hazardous outcomes. This paper presents a three-dimensional (3D) coupled Smoothed Particle Hydrodynamics and Finite Element Method (SPH-FEM) model, which was established to investigate pile punching and its impact on adjacent piles subjected to lateral loads. This approach handles the large distortions by avoiding mesh tangling and remeshing, contributing greatly high computational efficiency. The SPH-FEM model was validated against field measurements. The results of this study indicated that the soil type in which piles were embedded affected the interaction between piles during the pile punching. A comprehensive parametric study was carried out to evaluate the impact of soil properties on the displacement of piles due to the punching of an adjacent pile. It was found that the interaction between piles was comparatively weak when the piles were driven in stiff clays; while the pile-soil interactions were much more significant in sandy soils and soft clays. [less ▲]

Recyclable Architecture: Prefabricated and Recyclable Typologies

in Sustainability (2020)

Buildings are being demolished without taking into the account the waste generated, and the housing shortage problem is getting more critical as cities are growing and the demand for built space and the ... [more ▼]

Buildings are being demolished without taking into the account the waste generated, and the housing shortage problem is getting more critical as cities are growing and the demand for built space and the use of resources are increasing. Architectural projects have been using prefabrication and modular systems to solve these problems. However, there is an absence of structures that can be disassembled and reused when the structure’s life ran its course. This paper presents three building prototypes of new recyclable architectural typologies: (i) a Slab prototype designed as a shelf structure where wooden housing modules can be plugged in and out, (ii) a Tower prototype allowing for an easy change of layout and use of different floors and (iii) a Demountable prototype characterized by the entire demountability of the building. These typologies combine modularity, flexibility, and disassembling to address the increasing demands for multi-use, re-usable and resource-efficient constructions. Design, drawings, plans, and 3D models are developed, tested and analyzed as a part of the research. The results show that the implementation of the recyclable architectural concept at the first design stage is feasible and realistic, and ensures the adaptation through time, increases life span, usability and the material reusability, while avoiding demolition, which in turn reduces the construction waste and, consequently, the CO2 emissions. [less ▲]

Impact of pile punching on adjacent piles: Insights 3 from a 3D coupled SPH-FEM analysis

in Applied Mechanics (2020)

Pile punching (or driving) affects the surrounding area where piles and the adjacent piles can be displaced out of their original positions due to horizontal loads, leading to hazardous outcomes. This ... [more ▼]

Pile punching (or driving) affects the surrounding area where piles and the adjacent piles can be displaced out of their original positions due to horizontal loads, leading to hazardous outcomes. This paper presents a 3D coupled Smoothed Particle Hydrodynamics and Finite. Element Method (SPH-FEM) model, which was established to investigate pile punching and its impact on adjacent piles subjected to lateral loads. This approach handles the large distortions by avoiding mesh tangling and remeshing, contributing greatly high computational efficiency. The SPH-FEM model was validated against field measurements. Results of this study indicated that the soil type in which piles were embedded affected the interaction between piles during the pile punching. A comprehensive parametric study was carried out to evaluate the impact of soil properties on the displacement of piles due to the punching of an adjacent pile. It was found that the interaction between piles was comparatively weak when the piles were driven in stiff clays; while the pile-soil interactions were much more significant in sandy soils and soft clays. [less ▲]

Overcome of bed-joint imperfections and improvement of actual contact in dry-stacked masonry

in Construction and Building Materials (2020)

Several researchers studied dry-stacked masonry walls (DSM) and inferred that the actual contact surface between the different block rows and the compressive strength in such walls are reduced by bed ... [more ▼]

Several researchers studied dry-stacked masonry walls (DSM) and inferred that the actual contact surface between the different block rows and the compressive strength in such walls are reduced by bed-joint imperfections as well as by height differences between different masonry blocks leading both to high stress concentration. This paper concentrates on the first type on imperfections. Through experimental tests, it analyses the influence of bed-joint roughness on the load bearing capacity and investigates a strategy to improve the load-bearing capacity of DSM by placing an additional horizontal layer on the top face of raw masonry blocks. First, different contact layers using conventional and auxetic materials were applied. Then 20 dry-stacked masonry prisms built with raw and improved masonry blocks were tested under axial compressive load until failure. Prescale Fujifilm strips were used to measure the actual contact in the bed-joints. Experimental tests show that the use of a contact layer with well-defined material properties enables firstly to increase the actual contact area in the bed-joints from 23% to 98% of the nominal contact area and secondly to increase the load-bearing capacity by 14 to 97%. In addition, the contact layer with an auxetic material shows a significant capacity in altering the lateral expansion in the block units. The outcomes show that although the bed joint roughness influences the stress distribution in a dry-stacked masonry block, a contact layer with well-defined material properties enables to overcome the roughness induced by the bed-joint imperfections. [less ▲]

A material and component bank to facilitate material recycling and component reuse for a sustainable construction: concept and preliminary study

in Clean Technologies and Environmental Policy (2019)

This paper concerns the reusable components and recycled materials from demounted structures 16 which may draw a large amount of waste in construction industry. By a series of literature review 17 and ... [more ▼]

This paper concerns the reusable components and recycled materials from demounted structures 16 which may draw a large amount of waste in construction industry. By a series of literature review 17 and analyses, a material and component bank was proposed to manage more effectively the 18 recycling of materials and direct reuse of components even of whole components obtained from 19 old structures to facilitate a more sustainable construction industry. The concept, main businesses 20 and work operation of the bank were illustrated in detail including its potential management 21 method and supply chain. The relationship between the bank and current building information 22 modelling, design for deconstruction, supply chain and life cycle assessment based on the bank 23 were then analysed in detail. It can be concluded that the bank could pave the way for effectively 24 performing a further and repaid reuse of components and perfecting current recycling of materials 25 to contribute a more sustainable built environment from the view of various terms mentioned in 26 this study. The bank also can link with current method of life cycle assessment or environmental 27 impact assessment well, which all can promote the construction sustainability indicating the bank 28 can be integrated into current construction industry easily for the future. [less ▲]

Potential of the Deformation Area Difference (DAD)-Method for Condition Assessment of Bridge Structures

Scientific Conference (2019, August 27)

The construction industry ranks in the back rows in terms of digitalization. The numerous existing bridge structures require considerable effort for inspection and reliable assessment of their condition ... [more ▼]

The construction industry ranks in the back rows in terms of digitalization. The numerous existing bridge structures require considerable effort for inspection and reliable assessment of their condition. However, the state-of-the-art for inspecting these structures still relies on the visual inspection realized by bridge inspectors. The current paper summarizes several research projects in the field of condition assessment of bridge structures at the University of Luxembourg by analysing the structural response due to dynamic excitation and static loading tests. The latest development aims at using the most modern measurement techniques by combining them to a new method, the Deformation Area Difference (DAD)-Method in order to simplify and automatize at most the inspection process. The proposed DAD-Method is based on conventional static load deflection tests. It allows the localization of stiffness-reducing damage by using a very precise measurement of the deflection line and by combining this outcome to the deflection line generated by a simplified finite element model of the bridge. In order to investigate the condition of a bridge by the DAD-Method modern measurement techniques such as photogrammetry and laser scanning are used. In the framework of the conducted research, these techniques are also compared to traditional measurement systems such as total station and inductive displacement sensors as well as to digital levelling sensors. By theoretical examples and experimental tests, it can be shown that the DAD-Method is able to detect and localize damage when the damage level is dominant on the measurement noise. This paper investigates also the application of the method on a real bridge structure in Luxembourg. All of the above-mentioned measurement techniques were used, whereby the photogrammetry is applied using both, stable tripods and an autonomous flying drone. This allows examining the accuracy of the different measurement systems when applied on a real-size structure. [less ▲]

Computational chemo-thermo-mechanical coupling phase-field model for complex fracture induced by early-age shrinkage and hydration heat in cement-based materials

in Computer Methods in Applied Mechanics and Engineering (2019), 348

In this paper, we present a new multi-physics computational framework that enables us to capture and investigate complex fracture behavior in cement-based materials at early-age. The present model ... [more ▼]

In this paper, we present a new multi-physics computational framework that enables us to capture and investigate complex fracture behavior in cement-based materials at early-age. The present model consists of coupling the most important chemo-thermo-mechanical processes to describe temperature evolution, variation of hydration degree, and mechanical behavior. The changes of material properties are expressed as a function of the hydration degree, to capture the age effects. Fracture analysis of these processes are then accommodated by a versatile phase field model in the framework of smeared crack models, addressing the influence of cracks on hydration and thermal transfer. We additionally describe a stable and robust numerical algorithm, which aims to solve coupled problems by using a staggered scheme. The developed approach is applied to study the fracture phenomena at both macroscopic and mesoscopic scales, in which all microstructural heterogeneities of sand and cement matrix are explicitly accounted. Nucleation, initiation, and propagation of complex crack network are simulated in an efficient way demonstrating the potential of the proposed approach to assess the early-age defects in concrete structures and materials. [less ▲]

Role of interfacial transition zone in phase field modeling of fracture in layered heterogeneous structures

in Journal of Computational Physics (2019), 386

Mechanical behavior of layered materials and structures greatly depends on the mechanical behavior of interfaces. In the past decades, the failure in such layered media has been studied by many ... [more ▼]

Mechanical behavior of layered materials and structures greatly depends on the mechanical behavior of interfaces. In the past decades, the failure in such layered media has been studied by many researchers due to their critical role in the mechanics and physics of solids. This study aims at investigating crack-interface interaction in two-dimensional (2-D) and three-dimensional (3-D) layered media by a phase field model. Our objectives are fourfold: (a) to better understand fracture behavior in layered heterogeneous systems under quasi-static load; (b) to introduce a new methodology for better describing interfaces by a regularized interfacial transition zone in the context of varia-tional phase field approach, exploring its important role; (c) to show the accuracy , performance and applicability of the present model in modeling material failure at the interfaces in both 2-D and 3-D bodies; and (d) to quantitatively validate computed crack path with respect to experimental data. Phase field models with both perfectly and cohesive bonded interfaces are thus derived. A regularized interfacial transition zone is introduced to capture characteristics of material mismatch at the interfaces. Numerical examples for 2-D and 3-D layered systems with experimental validation provide fundamentals of fracture behavior in layered structures. The obtained results shed light on the behavior of crack paths, which are drastically affected by the elastic modulus mismatch between two layers and interface types, and reveal the important role of the proposed interfacial transition zone in phase field modeling of crack interface interactions. [less ▲]