Architecture, engineering, and construction (AEC) teams need more efficient and effective decisio... more Architecture, engineering, and construction (AEC) teams need more efficient and effective decision-making methods, particularly in the pre-construction phase when decisions have the most significant impact on building performance. This paper discusses the selection and application of decision-making methods for the preconstruction phase of a lean corporate campus project. Findings are based on the project team's review of several value-based decision methods and final selection of the Choosing By Advantages (CBA) approach. CBA was implemented first using group preferences, then with simple additive weighting of individual preferences. In general, decision makers found that CBA enabled multi-disciplinary stakeholder participation and added value to decision-making for simple decision problems. However, decision makers also believed that CBA was inefficient and ineffective for more complex decision problems and did not adequately clarify decision rationale. Switching to individua...
Biopolymer-bound Soil Composites (BSC), are a novel bio-based construction material class, produc... more Biopolymer-bound Soil Composites (BSC), are a novel bio-based construction material class, produced through the mixture and desiccation of biopolymers with inorganic aggregates with applications in soil stabilization, brick creation and in situ construction on Earth and space. This paper introduces a mixture design methodology to produce maximum strength for a given soil-biopolymer combination. Twenty protein and sand mix designs were investigated, with varying amounts of biopolymer solution and compaction regimes during manufacture. The ultimate compressive strength, density, and shrinkage of BSC samples are reported. It is observed that the compressive strength of BSC materials increases proportional to tighter particle packing (soil dry bulk density) and binder content. A theory to explain this peak compressive strength phenomenon is presented.
Proceedings of International Structural Engineering and Construction
Given the development of Additive Manufacturing (AM), popularly known as 3D Printing, the coexist... more Given the development of Additive Manufacturing (AM), popularly known as 3D Printing, the coexistence of AM and conventional manufacturing (CM) in AEC will be a reality for the foreseeable future. Case studies on two AM metallic building components demonstrated that AM for building components is technologically feasible but cost-prohibitive today, and, in some cases, has lower environmental impacts than CM. Firstly, a feasibility study was conducted to assess the applicability, time to manufacture, and manufacturing cost of AM vs. CM of specific metallic building components. Secondly, Life Cycle Assessment (LCA) was used to assess environmental impacts of AM and CM for those two cases. The case studies were the first well-documented comparative analyses of AM vs. CM for building components, and they contribute to the emerging "AM-in-AEC" knowledge base with their assessment approach, findings and documented baseline efforts for the analyses. The studies also revealed that ...
Proceedings of the 9th International Conference on Fracture Mechanics of Concrete and Concrete Structures
In this paper, corrosion-induced damage is investigated by means of numerical simulations utilizi... more In this paper, corrosion-induced damage is investigated by means of numerical simulations utilizing a coupled lattice and finite element method (FEM) modelling approach. While the reinforcement and corrosion product domain are discretized by the FEM, a lattice approach is used for the discretization of the concrete domain. To model the expansive nature of solid corrosion products, a thermal analogy is used. The modelling approach further accounts for the penetration of solid corrosion products into the available pore space of the surrounding cementitious materials and non-uniform distribution of corrosion products along the circumference of the reinforcement. Finally, results of numerical simulations in terms of corrosion-induced deformations and cracking are compared to experimental data obtained by digital image correlation and published in the literature.
Proceedings of the 9th International Conference on Fracture Mechanics of Concrete and Concrete Structures, 2016
High performance fiber-reinforced cement composites (HPFRCCs) have been designed to exhibit high ... more High performance fiber-reinforced cement composites (HPFRCCs) have been designed to exhibit high tensile strength and ductility compared to traditional concrete. HPFRCCs have also shown improved damage tolerance in compression. When reinforced with steel, HPFRCC components have been proposed for enhanced seismic resistance in structural applications. Because of the uncertainty associated with ground motions, determining an appropriate cyclic deformation history for seismic testing of structural components is a challenge. Different cyclic deformation histories have resulted in different cracking patterns in previous HPFRCC component tests. Several different cyclic loading protocols have been used in previous studies, but the deformation history itself has rarely been treated as a test variable. Two reinforced HPFRCC beams and two reference specimens made of reinforced concrete were tested under two different cyclic loading protocols. Cracking patterns, strain in the steel reinforcement, and hysteresis behavior were monitored through failure. The reinforced HPFRCC beams responded differently to different deformation histories than the reinforced concrete beams in terms of ductility and the amount of energy dissipated. Results from this study will contribute to a better understanding of reinforced HPFRCC component behavior under various cyclic deformation histories. 1 INTRODUCTION 1.1 HPFRCCs High performance fiber-reinforced cement composites (HPFRCCs) are a class of cement based materials that has been developed and studied for over three decades. HPFRCCs have many similar constituents to traditional concrete, but also contain short, randomly distributed fibers. The definitive characteristic of HPFRCC material behavior that sets it apart from
Natural fiber composites are of increasing interest in research because of their potential to pro... more Natural fiber composites are of increasing interest in research because of their potential to provide a low environmental impact material for applications, such as in the construction industry. In this analysis, fully bio-based composites with varying natural fiber reinforcement in a biosynthesized polymer matrix were assessed. The biopolymer was analyzed with two different carbon feedstock sources: simple carbohydrates and biogas. While both carbon feedstock sources result in the ability to cultivate rapidly renewable polymers, biogas as a feedstock source allows for use of a waste greenhouse gas emissions flow to produce a commodity. The bio-based composites were compared both on constant volume and for a decking application relative to a type of natural fiber filled petrochemical based polymer composite. When material properties and end-of-life considerations were incorporated, the biogas carbon feedstock biopolymer composites showed the potential to have a net beneficial global warming potential as well as favorable fossil fuel consumption and acidification relative to the conventional decking material, depending on natural fiber reinforcement selected. In terms of eutrophication impact, however, if byproducts from simple carbohydrate processing are considered, the simple carbohydrate feedstock biopolymer composites had the most beneficial impacts, suggesting consideration of the most critical environmental impact for the regions of production and use may be drivers for processing and selection of the bio-based composite constituents.
Natural fiber composites are of increasing interest in research because of their potential to pro... more Natural fiber composites are of increasing interest in research because of their potential to provide a low environmental impact material for applications, such as in the construction industry. In this analysis, fully bio-based composites with varying natural fiber reinforcement in a biosynthesized polymer matrix were assessed. The biopolymer was analyzed with two different carbon feedstock sources: simple car- bohydrates and biogas. While both carbon feedstock sources result in the ability to cultivate rapidly renewable polymers, biogas as a feedstock source allows for use of a waste greenhouse gas emissions flow to produce a commodity. The bio-based composites were compared both on constant volume and for a decking application relative to a type of natural fiber filled petrochemical based polymer composite. When material properties and end-of-life considerations were incorporated, the biogas carbon feedstock biopolymer composites showed the potential to have a net beneficial globa...
Deterioration of reinforced concrete infrastructure such as bridges, tunnels, and buildings repre... more Deterioration of reinforced concrete infrastructure such as bridges, tunnels, and buildings represents one of the major challenges currently facing developed countries. While engineering tools and methods for structural modelling and design of new reinforced concrete infrastructure are mature, methods and tools for modelling decades-long deterioration and maintenance are much less developed. In this paper, a multi-physics and multi-scale modelling approach for structural deterioration of reinforced concrete components due to reinforcement corrosion is presented. The multi-disciplinary modelling approach includes physical, chemical, electrochemical, and fracture mechanical processes at the material and meso-scale, which are further coupled with mechanical deterioration processes at the structural scale.
This paper presents a probabilistic-based framework for the design of civil infrastructure repair... more This paper presents a probabilistic-based framework for the design of civil infrastructure repair and rehabilitation to achieve targeted improvements in sustainability indicators. The framework consists of two types of models: (i) service life prediction models combining one or several deterioration mechanisms with a suite of limit states and (ii) life cycle assessment (LCA) models for measuring the impact of a given repair, rehabilitation, or strengthening. The first type of model estimates the time to the first repair (from the time of initial construction) and-given the structural condition after a repair-the time to any subsequent repair. The second type of model estimates the impact of the chosen repair or rehabilitation based on a process-based LCA of individual repair activities. Both models (service life or LCA) are formulated stochastically so that the time to repair and total impact are described by a probability density function. This leads to a fully probabilistic calculation of accrued cumulative impacts (which can be annualized) throughout the service life of a structure from initial construction up to the time of functional obsolescence (end of life). These are then compared to design targets taken from policy goals such as the Intergovernmental Panel on Climate Change's 4 th Assessment Report (IPCC AR4).
Deterioration of reinforced concrete infrastructure such as bridges, tunnels, and buildings repre... more Deterioration of reinforced concrete infrastructure such as bridges, tunnels, and buildings represents one of the major challenges currently facing developed countries. This deterioration leads to economic costs for maintenance and replacement, environmental impacts such as increased global warming potential as a result of cement production and traffic emissions, and social costs related to traffic congestion and human health concerns. While engineering tools and methods for structural modelling and design of new reinforced concrete infrastructure are mature, the methods and tools for modelling decades-long deterioration and maintenance are much less developed. An approach for modelling structural deterioration of reinforced concrete components due to reinforcement corrosion is presented and a procedure is introduced to estimate the time-dependent structural response, described using timedependent seismic fragility curves. The approach is part of a multi-disciplinary framework which...
Building stakeholders cannot easily quantify the sustainability impacts of constructed facilities... more Building stakeholders cannot easily quantify the sustainability impacts of constructed facilities. They lack information to perform effective analysis, management, and decision-making. In part, this is due to inadequate tools and methods to assess building life cycle impacts from design through construction. Currently available methods lack interoperability between design, analysis, and management software and life cycle inventory datasets that enable full life cycle assessment (LCA). To methodically manage the reduction of life cycle environmental impacts of buildings during construction, it is necessary to link environmental targets with modern construction management methods. This work develops a construction activity-based computational framework to enable stakeholders to reliably and efficiently construct dynamic life cycle models. Methods have been developed for time dependent impact budgets to provide construction managers and building owners a basis for process control. Spec...
An integrated finite element based modelling approach is presented, which allows for fully couple... more An integrated finite element based modelling approach is presented, which allows for fully coupled simulation of reinforcement corrosion and corrosion-induced concrete damage. While a finite element method (FEM) based corrosion model was used to describe electrochemical processes at the reinforcement surface, a FEM based mechanical model was used to simulate corrosion-induced concrete damage. Both FEM models were fully coupled, i.e. information, such as corrosion current density, damage state of concrete cover, etc., were constantly exchanged between the models. To demonstrate the potential use of the modelling approach, a numerical example is presented which illustrates full coupling of formation of corrosion cells, propagation of corrosion, and subsequent development of corrosion-induced concrete damage.
Architecture, engineering, and construction (AEC) teams need more efficient and effective decisio... more Architecture, engineering, and construction (AEC) teams need more efficient and effective decision-making methods, particularly in the pre-construction phase when decisions have the most significant impact on building performance. This paper discusses the selection and application of decision-making methods for the preconstruction phase of a lean corporate campus project. Findings are based on the project team's review of several value-based decision methods and final selection of the Choosing By Advantages (CBA) approach. CBA was implemented first using group preferences, then with simple additive weighting of individual preferences. In general, decision makers found that CBA enabled multi-disciplinary stakeholder participation and added value to decision-making for simple decision problems. However, decision makers also believed that CBA was inefficient and ineffective for more complex decision problems and did not adequately clarify decision rationale. Switching to individua...
Biopolymer-bound Soil Composites (BSC), are a novel bio-based construction material class, produc... more Biopolymer-bound Soil Composites (BSC), are a novel bio-based construction material class, produced through the mixture and desiccation of biopolymers with inorganic aggregates with applications in soil stabilization, brick creation and in situ construction on Earth and space. This paper introduces a mixture design methodology to produce maximum strength for a given soil-biopolymer combination. Twenty protein and sand mix designs were investigated, with varying amounts of biopolymer solution and compaction regimes during manufacture. The ultimate compressive strength, density, and shrinkage of BSC samples are reported. It is observed that the compressive strength of BSC materials increases proportional to tighter particle packing (soil dry bulk density) and binder content. A theory to explain this peak compressive strength phenomenon is presented.
Proceedings of International Structural Engineering and Construction
Given the development of Additive Manufacturing (AM), popularly known as 3D Printing, the coexist... more Given the development of Additive Manufacturing (AM), popularly known as 3D Printing, the coexistence of AM and conventional manufacturing (CM) in AEC will be a reality for the foreseeable future. Case studies on two AM metallic building components demonstrated that AM for building components is technologically feasible but cost-prohibitive today, and, in some cases, has lower environmental impacts than CM. Firstly, a feasibility study was conducted to assess the applicability, time to manufacture, and manufacturing cost of AM vs. CM of specific metallic building components. Secondly, Life Cycle Assessment (LCA) was used to assess environmental impacts of AM and CM for those two cases. The case studies were the first well-documented comparative analyses of AM vs. CM for building components, and they contribute to the emerging "AM-in-AEC" knowledge base with their assessment approach, findings and documented baseline efforts for the analyses. The studies also revealed that ...
Proceedings of the 9th International Conference on Fracture Mechanics of Concrete and Concrete Structures
In this paper, corrosion-induced damage is investigated by means of numerical simulations utilizi... more In this paper, corrosion-induced damage is investigated by means of numerical simulations utilizing a coupled lattice and finite element method (FEM) modelling approach. While the reinforcement and corrosion product domain are discretized by the FEM, a lattice approach is used for the discretization of the concrete domain. To model the expansive nature of solid corrosion products, a thermal analogy is used. The modelling approach further accounts for the penetration of solid corrosion products into the available pore space of the surrounding cementitious materials and non-uniform distribution of corrosion products along the circumference of the reinforcement. Finally, results of numerical simulations in terms of corrosion-induced deformations and cracking are compared to experimental data obtained by digital image correlation and published in the literature.
Proceedings of the 9th International Conference on Fracture Mechanics of Concrete and Concrete Structures, 2016
High performance fiber-reinforced cement composites (HPFRCCs) have been designed to exhibit high ... more High performance fiber-reinforced cement composites (HPFRCCs) have been designed to exhibit high tensile strength and ductility compared to traditional concrete. HPFRCCs have also shown improved damage tolerance in compression. When reinforced with steel, HPFRCC components have been proposed for enhanced seismic resistance in structural applications. Because of the uncertainty associated with ground motions, determining an appropriate cyclic deformation history for seismic testing of structural components is a challenge. Different cyclic deformation histories have resulted in different cracking patterns in previous HPFRCC component tests. Several different cyclic loading protocols have been used in previous studies, but the deformation history itself has rarely been treated as a test variable. Two reinforced HPFRCC beams and two reference specimens made of reinforced concrete were tested under two different cyclic loading protocols. Cracking patterns, strain in the steel reinforcement, and hysteresis behavior were monitored through failure. The reinforced HPFRCC beams responded differently to different deformation histories than the reinforced concrete beams in terms of ductility and the amount of energy dissipated. Results from this study will contribute to a better understanding of reinforced HPFRCC component behavior under various cyclic deformation histories. 1 INTRODUCTION 1.1 HPFRCCs High performance fiber-reinforced cement composites (HPFRCCs) are a class of cement based materials that has been developed and studied for over three decades. HPFRCCs have many similar constituents to traditional concrete, but also contain short, randomly distributed fibers. The definitive characteristic of HPFRCC material behavior that sets it apart from
Natural fiber composites are of increasing interest in research because of their potential to pro... more Natural fiber composites are of increasing interest in research because of their potential to provide a low environmental impact material for applications, such as in the construction industry. In this analysis, fully bio-based composites with varying natural fiber reinforcement in a biosynthesized polymer matrix were assessed. The biopolymer was analyzed with two different carbon feedstock sources: simple carbohydrates and biogas. While both carbon feedstock sources result in the ability to cultivate rapidly renewable polymers, biogas as a feedstock source allows for use of a waste greenhouse gas emissions flow to produce a commodity. The bio-based composites were compared both on constant volume and for a decking application relative to a type of natural fiber filled petrochemical based polymer composite. When material properties and end-of-life considerations were incorporated, the biogas carbon feedstock biopolymer composites showed the potential to have a net beneficial global warming potential as well as favorable fossil fuel consumption and acidification relative to the conventional decking material, depending on natural fiber reinforcement selected. In terms of eutrophication impact, however, if byproducts from simple carbohydrate processing are considered, the simple carbohydrate feedstock biopolymer composites had the most beneficial impacts, suggesting consideration of the most critical environmental impact for the regions of production and use may be drivers for processing and selection of the bio-based composite constituents.
Natural fiber composites are of increasing interest in research because of their potential to pro... more Natural fiber composites are of increasing interest in research because of their potential to provide a low environmental impact material for applications, such as in the construction industry. In this analysis, fully bio-based composites with varying natural fiber reinforcement in a biosynthesized polymer matrix were assessed. The biopolymer was analyzed with two different carbon feedstock sources: simple car- bohydrates and biogas. While both carbon feedstock sources result in the ability to cultivate rapidly renewable polymers, biogas as a feedstock source allows for use of a waste greenhouse gas emissions flow to produce a commodity. The bio-based composites were compared both on constant volume and for a decking application relative to a type of natural fiber filled petrochemical based polymer composite. When material properties and end-of-life considerations were incorporated, the biogas carbon feedstock biopolymer composites showed the potential to have a net beneficial globa...
Deterioration of reinforced concrete infrastructure such as bridges, tunnels, and buildings repre... more Deterioration of reinforced concrete infrastructure such as bridges, tunnels, and buildings represents one of the major challenges currently facing developed countries. While engineering tools and methods for structural modelling and design of new reinforced concrete infrastructure are mature, methods and tools for modelling decades-long deterioration and maintenance are much less developed. In this paper, a multi-physics and multi-scale modelling approach for structural deterioration of reinforced concrete components due to reinforcement corrosion is presented. The multi-disciplinary modelling approach includes physical, chemical, electrochemical, and fracture mechanical processes at the material and meso-scale, which are further coupled with mechanical deterioration processes at the structural scale.
This paper presents a probabilistic-based framework for the design of civil infrastructure repair... more This paper presents a probabilistic-based framework for the design of civil infrastructure repair and rehabilitation to achieve targeted improvements in sustainability indicators. The framework consists of two types of models: (i) service life prediction models combining one or several deterioration mechanisms with a suite of limit states and (ii) life cycle assessment (LCA) models for measuring the impact of a given repair, rehabilitation, or strengthening. The first type of model estimates the time to the first repair (from the time of initial construction) and-given the structural condition after a repair-the time to any subsequent repair. The second type of model estimates the impact of the chosen repair or rehabilitation based on a process-based LCA of individual repair activities. Both models (service life or LCA) are formulated stochastically so that the time to repair and total impact are described by a probability density function. This leads to a fully probabilistic calculation of accrued cumulative impacts (which can be annualized) throughout the service life of a structure from initial construction up to the time of functional obsolescence (end of life). These are then compared to design targets taken from policy goals such as the Intergovernmental Panel on Climate Change's 4 th Assessment Report (IPCC AR4).
Deterioration of reinforced concrete infrastructure such as bridges, tunnels, and buildings repre... more Deterioration of reinforced concrete infrastructure such as bridges, tunnels, and buildings represents one of the major challenges currently facing developed countries. This deterioration leads to economic costs for maintenance and replacement, environmental impacts such as increased global warming potential as a result of cement production and traffic emissions, and social costs related to traffic congestion and human health concerns. While engineering tools and methods for structural modelling and design of new reinforced concrete infrastructure are mature, the methods and tools for modelling decades-long deterioration and maintenance are much less developed. An approach for modelling structural deterioration of reinforced concrete components due to reinforcement corrosion is presented and a procedure is introduced to estimate the time-dependent structural response, described using timedependent seismic fragility curves. The approach is part of a multi-disciplinary framework which...
Building stakeholders cannot easily quantify the sustainability impacts of constructed facilities... more Building stakeholders cannot easily quantify the sustainability impacts of constructed facilities. They lack information to perform effective analysis, management, and decision-making. In part, this is due to inadequate tools and methods to assess building life cycle impacts from design through construction. Currently available methods lack interoperability between design, analysis, and management software and life cycle inventory datasets that enable full life cycle assessment (LCA). To methodically manage the reduction of life cycle environmental impacts of buildings during construction, it is necessary to link environmental targets with modern construction management methods. This work develops a construction activity-based computational framework to enable stakeholders to reliably and efficiently construct dynamic life cycle models. Methods have been developed for time dependent impact budgets to provide construction managers and building owners a basis for process control. Spec...
An integrated finite element based modelling approach is presented, which allows for fully couple... more An integrated finite element based modelling approach is presented, which allows for fully coupled simulation of reinforcement corrosion and corrosion-induced concrete damage. While a finite element method (FEM) based corrosion model was used to describe electrochemical processes at the reinforcement surface, a FEM based mechanical model was used to simulate corrosion-induced concrete damage. Both FEM models were fully coupled, i.e. information, such as corrosion current density, damage state of concrete cover, etc., were constantly exchanged between the models. To demonstrate the potential use of the modelling approach, a numerical example is presented which illustrates full coupling of formation of corrosion cells, propagation of corrosion, and subsequent development of corrosion-induced concrete damage.
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Papers by Michael Lepech