Wildland Urban Interface (WUI) Emissions: Laboratory Measurement of Aerosol and Trace Gas from Combustion of Manufactured Building Materials Katherine. B. Benedict, James E. Lee, Nitin Kumar, Prakash S. Badal, Michele Barbato, Manvendra K. Dubey, Allison C. Aiken ACS Es T Air, 2024 Wildfires are increasing in intensity and more often threatening the wildland urban interface (WUI) where buildings and homes coexist with the natural environment. WUI emissions have not been as well-studied as emissions from vegetation. Thus, there is a need to quantify the emissions of building materials used in home construction under flaming and smoldering conditions to study their impacts to human health, visibility, air quality, and climate. Here, in a controlled laboratory setting, we quantify emissions of aerosols and trace gases including formaldehyde, particulate matter, and black carbon. We focus on the combustion of traditional single-source wood-based construction fuels. Our results indicate that, similar to natural fuels, the aerosol optical properties were more related to combustion conditions than the fuel type. Overall, we observed significant variability in the gas and particle emissions. Consistent trends include high formaldehyde (HCHO) and carbon monoxide (CO) emissions for smoldering conditions and higher carbon dioxide (CO 2 ), nitrogen oxides (NO x ), and black carbon for flaming conditions. These observations highlight the need to better characterize emissions for materials in the built environment to assess large-scale climate and human health impacts of fires at the WUI.
Homogeneity and Isotropy of Compressed and Stabilized Earth Block Material: Mechanical Characterization and Statistical Analysis Erika L. Rengifo-López, Nitin Kumar, Fabio Matta, Michele Barbato Journal of Materials in Civil Engineering, 2024 Compressed and stabilized earth block (CSEB) masonry is a locally appropriate alternative for low-rise dwellings that offers attractive affordability, sustainability, and durability features. From a designer’s perspective, the availability of standards for material characterization and design codes is essential for CSEB masonry to be accepted and adopted. However, current standards and codes are limited—this is certainly the case in North America—and largely rely on empirical and prescriptive provisions that are adapted from those for conventional masonry (e.g., fired-clay or cinder-block). Advancing standardization and codification calls for advances in the fundamental understanding of material and structural behavior as a function of constituents and manufacturing methods. For CSEBs that are customarily compacted using metallic molds and hydraulic presses, a fundamental gap lies in the understanding of whether the heterogeneity of stabilized soil mixtures, together with their manufacturing process, result in block materials that can be approximated as homogeneous and isotropic at the scale of specimens used for physicomechanical characterization. This paper reports on an investigation of a CSEB material whose constituent properties and manufacturing process are representative of those frequently encountered in North America. Homogeneity and isotropy are established based on empirical evidence from microscopic and chemical analysis, and on the statistical analysis of uniaxial compressive strength and stiffness data obtained from samples that were extracted from different areas of different source blocks, and then tested by applying loads parallel or perpendicular to the compaction direction.
Finite Element Detailed Micromodeling of Unreinforced Earth Block Masonry Nitin Kumar, Michele Barbato, Erika L. Rengifo-López, Fabio Matta Journal of Structural Engineering United States, 2023 The structural response of earth block masonry is characterized by cracking patterns and inelastic behavior distributed across masonry units, mortar joints, and unit-mortar interfaces. This behavior is different from that exhibited by masonry built with fired clay bricks, concrete blocks, or regularly shaped stones, which are commonly characterized by cracking patterns and inelastic behavior within the mortar joints and unit-mortar interfaces and are typically analyzed using finite element (FE) simplified micro-models (SMMs). This paper presents a new detailed micromodel (DMM) specifically tailored for earth block masonry systems. The proposed DMM enables the accurate simulation of the experimentally-measured mechanical response of earth block wallettes subject to combined shear-compression diagonal loads, whereas the SMMs produce inaccurate results. Through a series of FE simulations of representative masonry elements, this study shows that the proposed DMM and different types of SMMs provide consistent predictions of mechanical behavior only under specific conditions, depending on the relative strength of masonry units and mortar as well as the loading conditions. The outcomes of this research provide a new tool for accurate prediction and simulation in instances where the compressive strength of the masonry units is similar to or lower than that of the mortar.
Capabilities and limitations of existing finite element simplified micro-modeling techniques for unreinforced masonry Nitin Kumar, , Michele Barbato, Erika L. Rengifo-López, Fabio Matta, , , and Research on Engineering Structures and Materials, 2022 Received 26 Feb 2022 Revised 13 May 2022 Accepted 17 May 2022 Finite element (FE) simplified micro-modeling techniques are commonly used to investigate and predict the mechanical behavior of masonry structures because they provide a good compromise between accuracy and computational cost. These FE techniques generally discretize masonry structural elements into expanded masonry units and zero-thickness interface joints of assumed known locations. These joints correspond to actual masonry joints and to preferential cracking surfaces, which are often placed vertically in the middle of the expanded masonry units to simulate the cracking mechanisms that are typically observed in masonry bricks and blocks. Three different versions of simplified micromodels (SMMs) are widely used in the literature to model the response of masonry walls and assemblies: SMMs with rigid, elastic, and elasto-plastic constitutive models for the expanded masonry units. All SMMs are based on the hypothesis that the masonry inelastic behavior and cracking are concentrated along the pre-defined zero-thickness interface joints. The hypothesis is often satisfied for ordinary masonry, in which masonry units are generally stronger than the masonry joints, i.e., mortar and unit-mortar interface. However, this hypothesis is not always satisfied for historical masonry with units of irregular shapes or for earth block masonry, in which masonry units and masonry joint can have similar mechanical properties. This paper highlights the capabilities and limitations of SMM techniques by comparing the experimentally-measured and numerically-simulated response of ordinary and earth block masonry walls, for which well-documented experimental results are available in the literature. It is found that SMMs can properly reproduce the mechanical behavior of masonry when the masonry units are significantly stronger than the masonry joints; however, SMMs produce poor estimates of the mechanical response when this hypothesis is not satisfied. This finding highlights the need to develop more general FE models to investigate the mechanical behavior of different masonry materials and construction techniques, as well as to identify the parameters controlling the cracking patterns and the conditions under which SMM techniques can be accurately use.
Effects of sugarcane bagasse fibers on the properties of compressed and stabilized earth blocks Nitin Kumar, Michele Barbato Construction and Building Materials, 2022 This paper investigates the effects of sugarcane bagasse fibers (SCBFs) on the mechanical strength and durability properties of compressed and stabilized earth blocks (CSEBs). CSEBs were fabricated using natural soil and SCBFs, collected from Lakeland, LA, with a manually operated compression machine. Nine different soil mix compositions containing different amounts of SCBFs (0%, 0.5%, and 1.0% by weight) and Type II Portland cement (0%, 6%, and 12% by weight) were considered. The flexural, dry compressive, and wet compressive strengths of the different CSEBs were evaluated experimentally. Durability was also examined by measuring mass loss, dry density, water absorption, and wet compressive strength after 12 wetting/drying cycles. The morphology and chemical composition of the CSEBs were investigated via scanning electron microscopy and energy-dispersive X-ray spectroscopy, whereas the mineralogical characteristics were evaluated using X-ray crystallography. The results show that including 0.5% to 1.0% by weight of SCBFs in CSEBs stabilized with 12% by weight of cement can significantly improve the CSEB mechanical properties without compromising their durability properties.
New Constitutive Model for Interface Elements in Finite-Element Modeling of Masonry Nitin Kumar, Michele Barbato Journal of Engineering Mechanics, 2019 A new interface element constitutive model is proposed in this study for analyzing masonry using the simplified micromodeling (SMM) approach, in which mortar and two unit–mortar interfaces ...
Feasibility Study of Affordable Earth Masonry Housing in the U.S. Gulf Coast Region Nitin Kumar, Michele Barbato, Robert Holton Journal of Architectural Engineering, 2018 Compressed and stabilized earth block (CSEB) structural systems represent a sustainable low-cost alternative to other construction systems that are common in industrialized countries. The wide availability of suitable soils makes these structural systems attractive for building affordable housing worldwide. Currently, CSEB construction in the USA is mainly used in dry and arid regions and has rarely been used in humid climates. In this work, a structural, architectural, and economic feasibility study for CSEB structural systems in the U.S. Gulf Coast region is presented. The structural feasibility study presented in this paper included the identification of locally available soils for CSEB fabrication; experimental investigation of mechanical properties of CSEB and mortar as function of their composition; durability study for a CSEB wall with and without protective plastering; and calculation of wind resistance for a representative CSEB house. The architectural feasibility study investigated the use of CSEB systems in vernacular housing typologies of Southern Louisiana. Finally, the economic feasibility study compared the cost of a reference house built using CSEBs and other more common construction materials. The results obtained in this study suggest that CSEB systems have the potential to provide a modern, cost-effective, sustainable, hurricane-resistant housing construction system as an alternative to more common constructions systems in the U.S. Gulf Coast region.
Can compressed and stabilized earth block materials be regarded as homogeneous and isotropic? Proceedings of the International Masonry Society Conferences, 2018
Masonry failure analysis using a composite interface model Journal of Structural Engineering India, 2013
RECENT SCHOLAR PUBLICATIONS
PATH ANALYSIS SHOWING THE EFFECTS OF THE PROFILE OF THE SUGARCANE GROWERS WITH THEIR CRISIS MANAGEMENT BEHAVIOUR S VC, S MONDAL, PK PAL, N KUMAR, R HR INTERNATIONAL JOURNAL 7 (8), 411-414 , 2024 2024
Capabilities and limitations of existing finite element simplified micro-modeling techniques for unreinforced masonry N Kumar, M Barbato, EL Rengifo-López, F Matta Research on Engineering Structures and Materials , 2022 2022 Citations: 15
Effects of sugarcane bagasse fibers on the properties of compressed and stabilized earth blocks N Kumar, M Barbato Construction and Building Materials 315, 125552 , 2022 2022 Citations: 72
New Constitutive Model for Interface Elements in Finite-Element Modeling of Masonry N Kumar, M Barbato Journal of Engineering Mechanics 145 (5) , 2019 2019 Citations: 44
Feasibility study of affordable earth masonry housing in the US Gulf Coast region N Kumar, M Barbato, R Holton Journal of Architectural Engineering 24 (2), 04018009 , 2018 2018 Citations: 27
Effects of larval rearing media and adult diets of rice moth, Corcyra cephalonica (Stainton) on longevity of moths and fecundity of female M Malik, N Kumar, Ombir Journal of Entomology and Zoology Studies 6 (6), 1192-1195 , 2018 2018 Citations: 7
Spinal cord stimulation reduces freezing of gait and improves gait in advanced Parkinson's disease Samotus,., N Kumar, S Memar, M Jog MOVEMENT DISORDERS 32 , 2017 2017
Optimization of lip length and aspect ratio of thin channel sections under minor axes bending N Kumar, DR Sahoo Thin-Walled Structures 100, 158-169 , 2016 2016 Citations: 40
Homogenization of periodic masonry using self-consistent scheme and finite element method N Kumar, H Lambadi, M Pandey, A Rajagopal International Journal for Computational Methods in Engineering Science and … , 2016 2016 Citations: 8
Limiting values of slenderness ratio for circular braces of concentrically braced frames PCA Kumar, DR Sahoo, N Kumar Journal of Constructional Steel Research 115, 223-235 , 2015 2015 Citations: 36
A rate independent cohesive zone model for modeling failure in quasi-brittle materials N Kumar, A Rajagopal, M Pandey Mechanics of Advanced Materials and Structures 22 (8), 681-696 , 2015 2015 Citations: 20
Monotonic behavior of large-scale SFRC beams without stirrups DR Sahoo, N Kumar Engineering Structures 92, 46-54 , 2015 2015 Citations: 52
Limiting slenderness ratio for hollow square braces in special concentrically braced frames PCA Kumar, DR Sahoo, N Kumar The Tenth Pacific Conference on Earthquake Engineering , 2015 2015 Citations: 1
Evaluation of energy parameters of short length buckling-restrained braces MS Pandikkadavath, N Kumar, DR Sahoo Proc. 15th Symposium on Earthquake Engineering , 2014 2014 Citations: 1
Plasticity based approach for failure modelling of unreinforced masonry N Kumar, R Amirtham, M Pandey Engineering structures 80, 40-52 , 2014 2014 Citations: 58
Optimum Range of Slenderness Ratio for Braces in Special Concentric Braced Frames N Kumar, PCA Kumar, DR Sahoo The 5th Asia Conference on Earthquake Engineering , 2014 2014
Evaluation of Limits of Slenderness Ratio of Braces Used in Special Concentrically Braced Frames PCA Kumar, N Kumar, DR Sahoo EUROSTEEL 2014 , 2014 2014
Computational Homogenization and Failure Modelling of Masonry N Kumar Indian Institute of Technology Hyderabad , 2013 2013
Masonry Failure Analysis Using a Composite Interface Model N Kumar, A Rajagopal 2013
MOST CITED SCHOLAR PUBLICATIONS
Effects of sugarcane bagasse fibers on the properties of compressed and stabilized earth blocks N Kumar, M Barbato Construction and Building Materials 315, 125552 , 2022 2022 Citations: 72
Plasticity based approach for failure modelling of unreinforced masonry N Kumar, R Amirtham, M Pandey Engineering structures 80, 40-52 , 2014 2014 Citations: 58
Monotonic behavior of large-scale SFRC beams without stirrups DR Sahoo, N Kumar Engineering Structures 92, 46-54 , 2015 2015 Citations: 52
New Constitutive Model for Interface Elements in Finite-Element Modeling of Masonry N Kumar, M Barbato Journal of Engineering Mechanics 145 (5) , 2019 2019 Citations: 44
Optimization of lip length and aspect ratio of thin channel sections under minor axes bending N Kumar, DR Sahoo Thin-Walled Structures 100, 158-169 , 2016 2016 Citations: 40
Limiting values of slenderness ratio for circular braces of concentrically braced frames PCA Kumar, DR Sahoo, N Kumar Journal of Constructional Steel Research 115, 223-235 , 2015 2015 Citations: 36
Feasibility study of affordable earth masonry housing in the US Gulf Coast region N Kumar, M Barbato, R Holton Journal of Architectural Engineering 24 (2), 04018009 , 2018 2018 Citations: 27
A rate independent cohesive zone model for modeling failure in quasi-brittle materials N Kumar, A Rajagopal, M Pandey Mechanics of Advanced Materials and Structures 22 (8), 681-696 , 2015 2015 Citations: 20
Capabilities and limitations of existing finite element simplified micro-modeling techniques for unreinforced masonry N Kumar, M Barbato, EL Rengifo-López, F Matta Research on Engineering Structures and Materials , 2022 2022 Citations: 15
Homogenization of periodic masonry using self-consistent scheme and finite element method N Kumar, H Lambadi, M Pandey, A Rajagopal International Journal for Computational Methods in Engineering Science and … , 2016 2016 Citations: 8
Effects of larval rearing media and adult diets of rice moth, Corcyra cephalonica (Stainton) on longevity of moths and fecundity of female M Malik, N Kumar, Ombir Journal of Entomology and Zoology Studies 6 (6), 1192-1195 , 2018 2018 Citations: 7
Limiting slenderness ratio for hollow square braces in special concentrically braced frames PCA Kumar, DR Sahoo, N Kumar The Tenth Pacific Conference on Earthquake Engineering , 2015 2015 Citations: 1
Evaluation of energy parameters of short length buckling-restrained braces MS Pandikkadavath, N Kumar, DR Sahoo Proc. 15th Symposium on Earthquake Engineering , 2014 2014 Citations: 1
PATH ANALYSIS SHOWING THE EFFECTS OF THE PROFILE OF THE SUGARCANE GROWERS WITH THEIR CRISIS MANAGEMENT BEHAVIOUR S VC, S MONDAL, PK PAL, N KUMAR, R HR INTERNATIONAL JOURNAL 7 (8), 411-414 , 2024 2024
Spinal cord stimulation reduces freezing of gait and improves gait in advanced Parkinson's disease Samotus,., N Kumar, S Memar, M Jog MOVEMENT DISORDERS 32 , 2017 2017
Optimum Range of Slenderness Ratio for Braces in Special Concentric Braced Frames N Kumar, PCA Kumar, DR Sahoo The 5th Asia Conference on Earthquake Engineering , 2014 2014
Evaluation of Limits of Slenderness Ratio of Braces Used in Special Concentrically Braced Frames PCA Kumar, N Kumar, DR Sahoo EUROSTEEL 2014 , 2014 2014
Computational Homogenization and Failure Modelling of Masonry N Kumar Indian Institute of Technology Hyderabad , 2013 2013
Masonry Failure Analysis Using a Composite Interface Model N Kumar, A Rajagopal 2013
