Modeling of aging effects on concrete creep / shrinkage behavior : a lattice discrete particle modeling approach

The currently aging and deteriorating infrastructures both in the US and all around the world have been a major cause to extend the current design provisions for concrete structures to 100 years of design lifetime. During such a long period, concrete exhibits a well-known time dependent behavior that is a function of multiple factors including both rheological aspects of the concrete mix as well as the effect of environmental conditions, which contribute to its time dependent aging. While initial conditions (e.g. concrete mix design parameters) can be well controlled, much less knowledge is available on the type and extent of the environmental conditions that will affect the structure

Towards a conceptual framework to manage BIM/COBie asset data using a standard project management methodology

Purpose: The purpose of this paper is to investigate a systematic methodology to manage asset data flow between building stakeholders throughout building life cycle using the Construction Operation Building Information Exchange (COBie) standard. / Design/methodology/approach: A literature review of the relevant building information modelling (BIM) for facilities management (FM) studies including the gaps and challenges of producing COBie data is analysed. Then a standard project management methodology by Project Management Institute (PMI) is introduced as a theoretical framework to map the different areas of managing COBie data as a project in coordination with Royal Institute of British Architects (RIBA) Plan of work. This theoretical background is coupled with an inductive approach through the placement within a construction company (Bouygues, UK) in the UCLH construction project to produce the conceptual framework that is aligned with industry needs. / Findings: The lack of well-structured approach to manage COBie data throughout building life cycle causes many problems and confusions about the roles and responsibilities of different stakeholders in creating and managing asset data. This confusion in turn results in incomplete and low-quality COBie data at the handover phase which hinders the ability of facility managers to use these data effectively in the operations phase. The proposed conceptual framework provides a standard project management process to systemise the data flow among all stakeholders. / Practical implications: The proposed framework is developed in liaison with a large construction company, so it is well aligned with an actual industry approach to managing COBie data. Furthermore, it provides a systematic step-by-step approach to managing COBie as a project that could be easily implemented in actual construction projects. / Originality/value: The paper introduced a novel approach to manage COBie data using a standard project management methodology based on an actual live construction project perspective coupled with project management theory

A polishing the harmful effects of Broad Bean Mottle Virus infecting broad bean plants by enhancing the immunity using different potassium concentrations

Broad bean mottle virus (BBMV) infects a wide range of hosts, resulting in significant production reductions. The lack of adequate and effective control methods involves implementing novel BBMV control strategies. Herein, we demonstrate the effect of different potassium concentrations (20, 40, and 60 mM) against BBMV in broad bean plants. Potassium could control BBMV infection in broad bean by inhibiting the virus. In addition, infection with BBMV caused a significant decrease in morphological criteria, SPDA, photosynthetic characteristics, phytohormones, and mineral content in broad bean leaves compared to control plants. The levels of reactive oxygen species (ROS) (hydrogen peroxide, hydroxyl radical, and oxygen anion) and ROS scavenging enzymes (catalase, superoxide dismutase, peroxidase, phenylaniline ammonia-lyase, chitinase, and 1,3 - glucanase) increased significantly in plants inoculated with BBMV alone or in the presence of K+. In addition, proline and phenolic compounds increased significantly after being infected with BBMV. In conclusion, treatment with a high potassium concentration (60 mM) alleviates the adverse effect of BBMV on broad bean plants by boosting secondary metabolites, phytohormones, and enzymatic antioxidants

Enforcing IPR Through Informal Institutions: The Possible Role of Religion in Fighting Software Piracy

The existence of formal IPR laws can be considered a prerequisite for having efficient law enforcement but does not imply efficient enforcement in itself. A simple model is constructed to explain the interplay between the IPR law and human behavior within counterfeiting countries. It shows how a politically monitored IPR enforcement strategy is able to alter formal IPR laws or institutions but might not affect informal institutions, or human morals and behavior, to the same extent, hence barely affecting piracy situation. The model shows the essential role of informal institutions and its sanction mechanisms in the enforcement process. The main obstacle of IPR enforcement is that people are still not convinced that IPR violations are unethical. Religion can be considered an informal institution that might support or hinder formal laws issued with regards to IPR and hence influence de facto enforcement of laws, especially in countries with high piracy rate if a high adherence to religion is found. As the Religion-Loyalty Index (RLI) developed by this study shows, Muslim countries have the highest religiosity level among different religions. Consequently, an investigation of how Islamic jurisprudence views IPR piracy is conducted. As Islam generally prohibits IPR piracy, a set of policy recommendations based on new institutional perspective is presented that can effectively help in minimizing IPR piracy in developing countries in general and Muslim ones in specific

Coupled multi-physics simulation of chloride diffusion in saturated and unsaturated concrete

Chloride-induced corrosion of steel reinforcement is one of the major long-term deterioration mechanisms for reinforced concrete infrastructures. Chloride transport through cement-based materials is a complex chemo-physical process involving ionic diffusion in concentrated solution, pore structure, chemistry, membrane permeability of the matrix, cracking, and the variation of the internal and external environmental conditions. Although in the literature there are plenty of both simplistic phenomenological models and sophisticated models, in this study, a new model is developed taking aim at capturing the fundamental physics and, at the same time, having a formulation as simple as possible that it can be effectively calibrated and validated using available limited experimental data. The model couples the ionic diffusion process with the concrete micro-structure evolution due to continued hydration accounting for hygro-thermal variations and their effects on both the diffusion and hydration processes. The formulation is implemented in a semi-discrete conduit transport network that mimics the internal heterogeneity of the cementitious material by connecting the matrix space between coarse aggregate pieces. This allows the model to replicate naturally the meso-scale tortuosity effect which is an important feature towards representing realistically the heterogeneity-induced variations of chloride concentration within the concrete. The limited model parameters are carefully calibrated and the formulation is validated by simulating multiple experiments ranging from diffusion through pastes to large concrete cylinders. The results of numerical simulations show the ability of the model to describe spatial and temporal evolution of the chloride concentration within the samples under varying chloride concentrations and temperature boundary conditions within both saturated and unsaturated concrete

"The role of technology as an enabler for agile workplace strategy: A case study of implementing agile working in the headquarters of a construction company in Central London"

The ever-increasing global competition in today’s business world has made it critical for organisations to rethink their business practices and value proposition to maintain their competitive advantage. Organisations look for agile strategies to strike an adequate balance between employee satisfaction, wellbeing and productivity in one side and the efficiency and effectiveness of utilising the space on the other side. The fast pace of technology development is considered an enabler for agile working. However, there are very few studies done on analysing the interconnected relationship between the social and technical/technological aspects of agile working. This case study was undertaken on three floors of the headquarter building of a construction and property development company in Central London. The study involved introducing agile working concept in the workplace, including adding social spaces, flexible open plan workstations monitored by Internet of things (IoT) technology i.e. occupancy sensors, implementing a new system of monitoring and managing meeting spaces to maximise the efficiency of space utilisation, and introducing a new Information technology and cybersecurity strategy to allow for this change. The study will analyse the factors that influenced this workplace change such as limitations of space, technology development, and the need for maximising the efficiency of the workplace. It will also analyse the lessons learned from implementing the agile working concept, regarding the role of technology, the social aspects, the business value of this implementation and the relationship between these factors

Lattice discrete particle modeling of alkali-silica-reaction effects to concrete structures

A large number of structures especially in high humidity environments are endangered by Alkali-Silica Reaction (ASR). ASR is characterized by two processes: the first is gel formation resulting from contact between alkali and reactive silica in aggregate particles; the second is water imbibition into the formed basic gel which leads to progressive swelling behavior. In turn, swelling causes deterioration of concrete internal structure inducing strength and stiffness loss. Many research efforts were directed towards the evaluation, modeling and treatment of these phenomena but a comprehensive computational model is still lacking. In this paper, the ASR effect is implemented within the framework of a mesoscale formulation, such as the one of the Lattice Discrete Particle Model (LDPM), which simulates concrete heterogeneous character. The proposed formulation allows a precise and unique modeling of ASR effect including non-uniform expansions, expansion transfer and heterogeneous cracking. The model can replicate ASR cracking behavior even in free expansion tests. This is a capability that cannot be obtained within classical homogeneous and isotropic continuum based models. In addition, it reproduces reactive aggregate size and distribution effects on the ASR expansion considering temperature and stress state effects. The present model was validated based on the simulation of experiments for free and laterally passively restrained specimens under free expansion. The results showed good agreement with the experimental data

A DISCRETE MODEL FOR ALKALI-SILICA-REACTION IN CONCRETE

The safety and durability of a large number of structures, especially in high humidity environments, are endangered by Alkali-Silica Reaction (ASR). ASR is characterized by two processes: the first is the formation of gel which happens when water transmitted alkali come in contact with reactive silica in aggregates; the second is the imbibition of water into this formed basic gel and the consequent swelling, which, in turn, causes deterioration of concrete internal structure by a diffuse cracking. In this paper, the ASR effect on concrete deterioration is implemented within the framework of a mesoscale formulation, the Lattice Discrete Particle Model (LDPM), that simulates the heterogeneity of the concrete internal structure as well as the thermo-chemo-mechanical characteristics of the ASR reaction. The proposed formulation allows a precise and unique modeling of ASR effect including non-uniform expansions, expansion transfer and heterogeneous cracking. The model can replicate ASR cracking behavior in free and confined expansion tests. This paper presents calibration and validation of the present model on the basis of experiments for unrestrained specimens under various axial loadings undergoing ASR expansion. The results show good agreement with the experimental data

Reliability of concrete multi-decade creep-shrinkage prediction using rate type discrete modeling

This presentation discusses the explicit implementation of the solidificationmicroprestress (SM) theory within the Lattice Discrete Particle Model (LDPM). Aging effect is obtained using a global reaction degree of concrete obtained by a multi-physics model evolving temperature, humidity and cement degree of reaction in full coupling over time and space. Then explicit rate-type visco-elastic and viscous creep eigenstrains are implementation within the LDPM framework. Finally, extensive calibration and validation of the model is pursued by numerical simulations of experimental data from literature. Then, multi-decade deformation simulations are presented along with the effects of creep model parameter uncertainty to show its robustness

Lattice Discrete Particle Modeling (LDPM) of Alkali Silica Reaction (ASR) deterioration of concrete structures

A large number of structures especially in high humidity environments are endangered by Alkali–Silica Reaction (ASR). ASR leads to the formation of an expansive gel that imbibes water over time. The gel expansion causes cracking and consequent deterioration of concrete mechanical behavior in the form of strength and stiffness reduction. In the recent past, many research efforts were directed towards evaluation, modeling and treatment of ASR effects on structures but a comprehensive computational model is still lacking. In this paper, the ASR effect is implemented within the framework of the Lattice Discrete Particle Model (LDPM), which simulates concrete heterogeneous character at the scale of coarse aggregate pieces. The proposed formulation, entitled ASR-LDPM, allows precise and unique modeling of volumetric expansion; expansion anisotropy under applied load; non-uniform cracking distribution; concrete strength and stiffness degradation; alkali ion concentration effect; and temperature effects of concrete subjected to ASR. In addition, a unique advantage of this formulation is its ability to distinguish between the expansion directly related to ASR gel expansion and the one associated with cracking. Simulation of experimental data gathered from the literature demonstrates the ability of ASR-LDPM to predict accurately ASR-induced concrete deterioration