Papers by Venkatesh Kodur
Journal of Building Engineering, 2021
Machine learning (ML) continues to rise as an effective and affordable method of tackling enginee... more Machine learning (ML) continues to rise as an effective and affordable method of tackling engineering problems. Unlike other disciplines, the integration of ML into structural and fire engineering domains remains deficient. This is due in part to the lack of benchmark databases to compare the effectiveness of ML models. In order to bridge this knowledge gap, this paper presents a benchmark examination of common supervised learning ML algorithms that can be easily deployed into structural and fire engineering problems. The selected algorithms include; Decision Trees (DT), Random Forest (RF), Extreme Gradient Boosted Trees (ExGBT), Light Gradient Boosted Trees (LGBT), TensorFlow Deep Learning (TFDL), and Keras Deep Residual Neural Network (KDP), and are used with their default values to establish a proper benchmark against six databases. The compiled datasets have been thoroughly tested and span two domains, structural engineering; 1) elemental response of concrete-filled steel tubular (CFST) circular columns at ambient conditions, 2) shear response of cold-formed steel (CFS) channels with slotted webs, 3) compressive strength of concrete, 4) fatigue life data, 5) shear strength of reinforced concrete (RC) beams and FRP-strengthened RC beams; and fire engineering, 6) fire behavior of RC concrete columns in terms of spalling occurrence and fire resistance. This study also investigates a variety of commonly used performance metrics that are applicable to regression and classification-based ML problems. We invite ML users to apply their models to the presented databases to establish a benchmark by mean of external validation and then extend their models to other problems and databases. Collectively, the presented work establishes the first step towards a unified framework that can be used to accelerate the adoption of ML into structural and fire engineering domains.
Engineering Fracture Mechanics, 2015
This paper presents cohesive zone model (CZM) fracture properties of spray-applied fire-resistive... more This paper presents cohesive zone model (CZM) fracture properties of spray-applied fire-resistive material (SFRM) for modeling delamination of fire insulation from steel structures. For characterizing cohesive zone properties, namely cohesive strength, cohesive fracture energy and cohesive displacement ductility, a set of experiments are conducted on three types of commercially available SFRM namely medium density Portland cement-based, medium density gypsum-based and mineral fiber-based. Data from experiments is utilized to develop a cohesive stress-displacement relationships in both mode-I and mode-II delamination. The recorded stress-displacement relationship indicates noticeable strain-softening zone verifying that SFRM is not a completely brittle material, rather, it is quasi-brittle.
International Journal of Impact Engineering, 2015
This paper presents an experimental-numerical approach for evaluating dynamic fracture and delami... more This paper presents an experimental-numerical approach for evaluating dynamic fracture and delamination of fire insulation from steel structures during impact loading. The experiments encompass drop mass impact tests on steel beams insulated with three types of sprayed applied fire resistive material (SFRM), namely Portland cement-based, gypsum-based and mineral fiber-based, commonly utilized in steel construction. The impact tests are conducted at two kinetic energy levels to evaluate the strain ratedependency of fracture energy and extent of delamination at steel-SFRM interface. Results from experiments show that the cracking and delamination of SFRM is mainly localized on the bottom flange with slight extension into lower part of web of beam at the mid span. Further, Portland cement-based SFRM can withstand the applied impact energy and no delamination or substantial cracking in SFRM occurs, whereas two other types of SFRM experienced significant fracture and delamination on the bottom flange. A fracture mechanics-based numerical approach is subsequently employed to simulate the conducted experiments using LS-DYNA finite element code. In the explicit numerical model, cohesive zone approach is adopted to model fracture process zone at the interface of steel and SFRM. By quantifying and calibrating the extent of delamination on the bottom flange, the dynamic increase factor of fracture energy and stress-displacement relationships, determined through previous static fracture tests, is estimated. According to numerical simulations, extent of delamination in mineral fiber-based SFRM is not dependent on strain rate, whereas in the case of gypsum-based and Portland cement-based SFRM extent of delamination is a function of strain rate.
Journal of Structural Engineering, 2015
AbstractThis article presents a numerical approach in which the implicit finite element method an... more AbstractThis article presents a numerical approach in which the implicit finite element method and fracture mechanics concepts are applied to simulate crack propagation at the interface of fire insulation and truss members in steel framed buildings. An intrinsic cohesive zone model (CZM) in conjunction with contact interaction analysis is applied to model the progression of fracture at the interface of fire insulation and slender steel truss members. Experimentally determined cohesive zone properties are utilized to simulate the progressive delamination in three types of commercially available spray-applied fire-resistive material (SFRM) applied on a truss chord. The numerical model, which is initially validated against the previously conducted fracture experiments, is employed to perform a sensitivity analysis with respect to CZM parameters, SFRM elastic modulus, and thickness of SFRM. Results obtained from a sensitivity study are subsequently utilized to define a delamination characteristic parameter (d...
Construction and Building Materials, 2015
h i g h l i g h t s Factors governing delamination of SFRM from steel structures are evaluated. C... more h i g h l i g h t s Factors governing delamination of SFRM from steel structures are evaluated. Cohesive zone model is applied to simulate delamination phenomenon. Delamination of fire insulation from steel truss is modeled. Delamination of fire insulation applied on a beam-column assembly is modeled. Effective properties of SFRM to mitigate delamination are quantified.
Journal of Engineering Mechanics, 2014
ABSTRACT This paper presents a numerical model for evaluating internal fracture and delamination ... more ABSTRACT This paper presents a numerical model for evaluating internal fracture and delamination at the interface of fire insulation and steel surface in structural members. A cohesive zone model in combination with contact condition is employed in a 3D finite-element model to simulate the fire-insulation damage throughout the loading range, from initial loading stage until failure through fracture. The numerical model is validated by comparing model predictions, namely internal fracture and interfacial delamination of insulation, against test data generated at both material and structural levels. The validated model was applied to quantify the effect of critical factors on the extent of delamination between steel and fire insulation. Results from the parametric studies indicate that critical fracture energy at steel-insulation interface, insulation thickness, modulus of elasticity, and internal cohesion of insulation material have significant influence on the spread of delamination at steel-insulation interface. Further, delamination of insulation from steel surface occurs mostly in the plastic hinge zone and specifically in the tensile flange.
Journal of Constructional Steel Research, 2016
Bridge fires are becoming an increasing concern, and for steel plate girder bridges in particular... more Bridge fires are becoming an increasing concern, and for steel plate girder bridges in particular, web shear buckling is one of the failure mechanisms that can make it necessary to replace the girder after the fire is extinguished. The objective of this study is to evaluate the web shear buckling response of two experimental plate girder specimens subject to fire conditions, and also to determine how complex computational models must be to accurately characterize the web shear buckling response of steel plate girders subjected to fire. Three parameters are evaluated: boundary conditions representing the flange, representation of thermal gradients, and composite action with the slab. To meet this objective, finite element models with varying parameters are compared to each other and to experimental results. Results show that the presence of a composite slab significantly increases the shear capacity of the plate girder. The presence of thermal gradients makes finite element modeling of the flange more sensitive to the results compared to a uniform temperature distribution. Modeling the girder with a uniform
Prestressed hollow core concrete slabs are utilized in parking structures due to their cost effec... more Prestressed hollow core concrete slabs are utilized in parking structures due to their cost effectiveness, superior quality, and inherent high fire resistance. Currently, fire resistance of these slabs is assessed based on prescriptive based approaches which are derived from standard fire tests on slabs. Vehicle fire scenarios in parking structures can be significantly different from standard or compartment fires, still there are limited guidelines to assess the fire resistance of hollow core slabs under the same. To overcome these drawbacks, a rational design approach is applied for evaluating fire resistance of hollow core slabs. A finite element based numerical model, built in ANSYS, is applied to evaluate fire performance of hollow core slabs under realistic fire loading scenarios as present in parking structures. Results from these numerical studies clearly indicate that hollow core slabs exhibit higher fire resistance under realistic fire and loading conditions.
Fly ash concrete is finding increasing applications in construction; however there is lack of dat... more Fly ash concrete is finding increasing applications in construction; however there is lack of data on fire performance of fly ash concrete structural members. This paper presents results from fire resistance tests on fly ash concrete columns. Data generated from tests on high strength fly ash concrete columns is compared with those of conventional high strength concrete (HSC) columns. The effect of concrete type, fire exposure scenario, fly ash, and fibers in concrete mix on fire performance of fly ash concrete columns is discussed. Results from fire resistance tests show that fly ash concrete columns exhibit almost similar fire resistance to that of conventional HSC columns. Further, the addition of polypropylene fibers mitigates fire induced spalling in high strength fly ash concrete columns.
High strength concrete (HSC) columns exhibit lower fire resistance, as compared to conventional n... more High strength concrete (HSC) columns exhibit lower fire resistance, as compared to conventional normal strength concrete columns, due to occurrence of fire induced spalling and faster degradation of strength and stiffness properties of concrete with temperature. Fire resistance tests on HSC columns have shown that fire performance of HSC columns can be enhanced through bending the ends of ties at 135° into the concrete core, instead of bending the ties at 90°. This paper presents an analytical approach to model the effect of tie configuration on fire resistance of reinforced concrete (RC) columns. The proposed approach is based on seismic design principles and involves calculation of force acting on ties by evaluating effective stresses resulting from pore pressure, mechanical strain and thermal expansion. The resulting force acting on ties is compared against temperature (time) dependent bond strength (at the tie-concrete interface) to evaluate the failure of ties. The proposed tie sub-model is built in to an existing macroscopic finite element based fire resistance analysis computer program that is capable of tracing the fire response of reinforced concrete (RC) columns in the entire range of behavior. The predictions from the model are compared against the full-scale fire resistance tests on RC columns to demonstrate the validity of the proposed approach in evaluating the beneficial effect of 135° tie configuration. The validated model is applied, through case studies, to quantify the effect of tie configuration on fire resistance of reinforced concrete columns. Results from numerical studies clearly show that HSC columns with 135° bent ties exhibit higher fire resistance than those HSC columns with 90° bent ties.
... EFFECT OF TEMPERATURE ON THERMAL AND MECHANICAI. ... means of a Thermogravimetric Analyzer (T... more ... EFFECT OF TEMPERATURE ON THERMAL AND MECHANICAI. ... means of a Thermogravimetric Analyzer (TGA) in the temperature range between room temperature and 1000 ... measured were the strength and deformation properties of the concretes at elevated temperatures (6 ...
... NRC Publications Archive. Enhancing the fire resistance of steel columns through composite co... more ... NRC Publications Archive. Enhancing the fire resistance of steel columns through composite construction. ... Link: Link: HTML Link: HTML Link: Export. | Get Link Enhancing the fire resistance of steel columns through composite construction NPArC # 5755292 ...
L'utilisation croissante du béton haute résistance dans les bâtiments et autres ouvrages... more L'utilisation croissante du béton haute résistance dans les bâtiments et autres ouvrages suscite des interrogations concernant sa tenue au feu, en particulier en raison du danger d'effritement (ou éclatement). Cet article expose les résultats des recherches menées à ce ...
This report presents the results of 2 full-scale fire resistance tests conducted on load-bearing ... more This report presents the results of 2 full-scale fire resistance tests conducted on load-bearing gypsum board protected, wood stud shear wall assemblies. The wall assembly had an asymmetrical installation (1x2) with a layer of gypsum board on both exposed and unexposed sides and a shear membrane as a base layer on the unexposed side of the wood stud frame. The gypsum board used was 12.7 mm thick Type X and the shear membranes used were of 12.7 mm and 8.5 mm thick plywood. The insulation used were of cellulose and glass fibre type.
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Papers by Venkatesh Kodur