Composite slabs micromechanics characterization of the steel-concrete interaction with finite element models

El objetivo del presente artículo es la mejora de la caracterización, mediante el uso de modelos avanzados de elementos finitos, del comportamiento de las losas mixtas con perfil de acero conformado y hormigón. El modelado de las geometrías tridimensionales de un perfil comercial de acero a escala real habilita el estudio de su micromecánica. La inclusión en el perfil de acero de las embuticiones, espesores, ángulos de inclinación y separación entre embuticiones elimina la necesidad de las simplificaciones en el complejo contacto que se produce entre ambos materiales. La gran correlación obtenida entre los modelos de elementos finitos y sus respectivos especímenes de laboratorio abre la puerta a una mejor comprensión de las complejas distribuciones de tensiones y a su caracterización. En particular, se introduce la novedosa representación de la tensión longitudinal rasante {\textstyle {\tau }_{u}} y de una nueva tensión vertical normal {\textstyle {\sigma }_{u}} entre el acero y el hormigón que frecuentemente determinan la capacidad resistente de la losa mixta. El estudio se complementa con una representación en los modelos de elementos finitos de resultados experimentales de tensiones y deformaciones obtenidos mediante galgas extensiométricas.This study focuses on the improvement of composite slabs characterization throughout the use of advanced finite elements models. The accurate three-dimensional modelling of a full scale commercial steel sheet and concrete slab geometries enables the analysis of the composite slab micromechanics. The inclusion of the embossments depth and slope, the steel sheet thickness, the tilting angle, the length and width and spacing of embossments, and the profiling angle of the rib shape removes the need of simplifications for the complex phenomenon at the steel – concrete interface. The accuracy observed at the finite element models once compared with the laboratory specimens enables a new approach to describe the complex stress distributions in composite slabs. In particular, this study introduces a novel representation of the longitudinal shear strength {\textstyle {\tau }_{u}} and a newly defined vertical normal stress {\textstyle {\sigma }_{u}} between the steel and concrete that frequently define the overall composite slab bearing capacity. Subsequently, this study compares detailed stress diagrams and deformations from the finite elements models with experimental data obtained through piezoelectric gauges at the laboratory specimens.Postprint (published version

Culinary and sensory traits diversity in the Spanish Core Collection of common beans (Phaseolus vulgaris L.)

The Spanish National Plant Genetic Resource Center's core collection of bean germplasm includes 202 accessions selected from more than 3000 accessions in function of passport data, seed phenotype, genetic background, and agronomic traits. To acquire more useful information about these accessions, we cultivated and characterized them for sensory and culinary traits. We found considerable variation for culinary and sensory traits of the cooked beans (mean coefficients of variation: 41% for the sensory traits and 40% for the culinary traits). The large dataset enabled us to study correlations between sensory and culinary traits and among these traits and geographic origin, seed color, and growth habit. Greater proportion of white in the seed coat correlated positively with brightness and negatively with mealiness (r=0.60, r=-0.60, p<0.001, respectively). Mealiness correlated negatively with seed-coat roughness and rate of water absorption (r=-0.60, r=-0.53, p<0.001, respectively). Materials of Andean origin had lower seed-coat brightness (p<0.01) and seed-coat roughness, and greater seed-coat perceptibility, mealiness, flavor, and aroma (p<0.001) than materials of Mesoamerican origin. Growth habit failed to correlate with culinary or sensory traits.Postprint (published version

Characterization of the longitudinal shear strength in composite slabs

The concrete-steel composite slabs show a complex structural characterization due to the different behaviours at the two materials. The materials are exposed to different deformations, large deflections and complex stresses with still a limited understanding of their micromechanics. Hence, current building codes rely on expensive and tedious laboratory tests that characterize the composite slab failure and the ultimate resistance. The Finite Element (FE) numerical simulations were introduced more than 25 years ago in composite slab studies as a mechanism to validate new design methods and also as an alternative to reduce laboratory tests requirements. However, the simulations historically observed a significant number of simplifications such as reduced scale models or simplified geometries. This dissertation introduces initially a novel modeling and simulation methodology that enables new insights in the steel deck and concrete slab response for bending. Distinct full-scale finite element models were generated for four commercial steel deck profiles to simulate the laboratory tests. An intense and systematic optimization process was carried out as the computational costs and the simulation files size associated with the initial FE models were significant. The three-dimensional composite models detailed embossment depth and slope, steel thickness, or tilting angle, among several others. Common limitations and simplifications related to steel-concrete contact, adhesion, and cohesion factors in previous research efforts were addressed. Newton-Raphson was the simulation method and enabled the consideration of geometrical and materials nonlinearities. The proposed methodology was validated by comparison of the results from the bending simulations with the actual maximum loads, midspan deflection and end slip values obtained from laboratory bending tests. Based on the robustness of the bending simulations, parametric and boundary conditions analyses were performed through pull-out simulations. Micromechanics phenomena that could not be observed during laboratory tests were investigated at the full-scale bending simulations. First, the neutral axes and vertical disconnection representations for the steel deck and concrete slab were characterized and subsequently they proved the existence of partial connection between the materials. Second, a new normal vertical tension parameter sshear was introduced to describe the vertical stresses at the steel deck and the concrete slab. Third, the longitudinal shear strength Zu was computed for different midspan deflections, loads and friction coefficients. The longitudinal shear failure is the most common failure phenomenon among open rib steel deck profiles and thus multiple studies were performed. The observation of a constant Zu value at the shear span of the bending test was novel and indicated that the Eurocode 4 Partial Connection Method was not capable to describe the complex longitudinal shear strength behaviour observed from the simulations. The dissertation concludes with the introduction of a new characterization parameter tu,mechanical to assess the composite slab design efficiency. The parameter is defined as the longitudinal shear strength tu computed from the simulations for a null friction coefficient. The new parameter proved to accurately characterize the performance of the different composite slabs studied in this dissertation when compared with the maximum loads from the laboratory tests. The combiation of the novel modeling and simulation methodology with the tu,mechanical computation enabled a new design process for steel deck profiles. The process developed an iterative computer-focused approach with the goal to reduce the reliance in the costly and tedious laboratory tests.Les lloses mixtes formades per acer i formigó presenten una caracterització estructural complexa degut al comportament diferent dels seus dos materials constituents. Aquests materials pateixen diferents nivells de deformacions, grans desplaçaments i distribucions d'esforços complexes, i avui en dia encara es desconeixen molts dels aspectes fonamentals de la seva micro-mecànica. En conseqüència, les normatives actuals requereixen la realització d'assajos de laboratori per a cada llosa mixta a través d'un procés costós i llarg. La utilització de les simulacions numèriques basades en elements finits per l'estudi de les lloses mixtes es va introduir fa més de 25 anys com a un mecanisme per validar nous processos de disseny i per reduir els exigents requeriments dels assajos normatius de laboratori. Malgrat això, històricament i fins a dia d'avui les simulacions numèriques han patit simplificacions importants, com la realització de models a escala reduïda o amb geometries simples. La recerca introdueix inicialment una nova metodologia de modelat i simulació en lloses mixtes que aporta noves dades en el comportament del perfil de xapa nervada i de la llosa de formigó. Es van desenvolupar diferents models d'elements finits per a quatre perfils de xapa comercials per replicar els assajos de laboratori de flexió. Inicialment, es va implementar un procés d'optimització sistemàtic en els models d'elements finits, ja que tant els costos computacionals com la mida de les simulacions eren elevats. Els models tridimensionals van incloure la profunditat i pendent de les emboticions, el gruix de la xapa d'acer i l'angle del nervi, entre molts altres paràmetres geomètrics. Es van millorar simplificacions i limitacions habituals observades en recerca publicada anteriorment sobre la interfície formigó-acer, el factor d'adhesió i els factors de cohesió. Es va implementar el mètode de simulació de Newton-Raphson, que va permetre la consideració de no-linealitats en geometries i materials. La metodologia proposada va ser validada comparant-la amb els resultats experimentals dels assajos de flexió. A partir de la solidesa observada en les simulacions de flexió, es van desenvolupar nous models d'elements finits de l'assaig de pull-out per realitzar un estudi paramètric i de condicions de contorn. A partir de les simulacions, es van analitzar multitud de fenòmens micro-mecànics que no s'havien pogut detectar directament en el laboratori. Primer, es van caracteritzar les representacions dels eixos neutres i la desconnexió vertical entre el formigó i l'acer, i posteriorment es va demostrar l'existència de connexió parcial entre ambdós materials. Segon, es va definir una nova tensió vertical normal σshear per descriure les tensions verticals observades entre la xapa d'acer i la llosa de formigó. Tercer, es va calcular l'esforç longitudinal a rasant tu per a tota la longitud del nervi i per a diferents càrregues. L'observació d'un segment amb valor constant va validar una de les hipòtesis del Mètode de la Connexió Parcial de l'Eurocodi 4. Així mateix, també va posar de manifest que el model mecànic d'aquest mètode no era capaç de capturar la complexitat observada en les simulacions per l'esforç "τu". La recerca conclou amb la introducció d'un nou paràmetre de caracterització de l'eficiència de la llosa mixta anomenat "τu,mechanical". Aquest paràmetre es defineix com l'esforç longitudinal a rasant tu obtingut de les simulacions amb fricció nul.la. El nou paràmetre va caracteritzar correctament els diferents perfils comercials modelats quan van ser comparats amb la seva resistència última obtinguda en els assajos de laboratori. La combinació de "τu,mechanical" i la nova metodologia de modelat i simulació genera un nou procés de disseny per lloses mixtes. A través d'un procés iteratiu centrat en simulacions que optimitzen "τu,mechanical", el procés genera una proposta de disseny final de la xapa d'acer, sense la necessitat de realitzar cap assaig al laboratori

3D non-linear realistic simulations of composite slabs bending test

The accurate modelling of composite slabs through finite elements (FE) can describe the complex phenomena occurring between the steel and concrete materials. Current semi-empirical design methods based on full scale test require an expensive process to characterize the composite slab performance and provide limited insights on the actual materials’ comportment. This paper presents early results on an accurate geometrical and physical 3D FE modelling of a full scale bending tests with the potential to describe both materials’ macro and micro behaviours. With a focus on the modelling of the concrete elements, this study leverages experimental tests to assess robustness of some variables at the FE models, recommending a novel approach for accurate modelling

3D non-linear realistic simulations of composite slabs bending test

The accurate modelling of composite slabs through finite elements (FE) can describe the complex phenomena occurring between the steel and concrete materials. Current semi-empirical design methods based on full scale test require an expensive process to characterize the composite slab performance and provide limited insights on the actual materials comportment. This paper presents early results on an accurate geometrical and physical 3D FE modelling of a full scale bending tests with the potential to describe both materials’ macro and micro behaviours. With a focus on the modelling of the concrete elements, this study leverages experimental tests to assess robustness of some variables at the FE models, recommending a novel approach for accurate modelling.Postprint (published version

3D non-linear realistic simulations of composite slabs bending test

The accurate modelling of composite slabs through finite elements (FE) can describe the complex phenomena occurring between the steel and concrete materials. Current semi-empirical design methods based on full scale test require an expensive process to characterize the composite slab performance and provide limited insights on the actual materials comportment. This paper presents early results on an accurate geometrical and physical 3D FE modelling of a full scale bending tests with the potential to describe both materials’ macro and micro behaviours. With a focus on the modelling of the concrete elements, this study leverages experimental tests to assess robustness of some variables at the FE models, recommending a novel approach for accurate modelling

3D non-linear realistic simulations of composite slabs bending test

The accurate modelling of composite slabs through finite elements (FE) can describe the complex phenomena occurring between the steel and concrete materials. Current semi-empirical design methods based on full scale test require an expensive process to characterize the composite slab performance and provide limited insights on the actual materials’ comportment. This paper presents early results on an accurate geometrical and physical 3D FE modelling of a full scale bending tests with the potential to describe both materials’ macro and micro behaviours. With a focus on the modelling of the concrete elements, this study leverages experimental tests to assess robustness of some variables at the FE models, recommending a novel approach for accurate modelling

3D non-linear realistic simulations of composite slabs bending test

The accurate modelling of composite slabs through finite elements (FE) can describe the complex phenomena occurring between the steel and concrete materials. Current semi-empirical design methods based on full scale test require an expensive process to characterize the composite slab performance and provide limited insights on the actual materials’ comportment. This paper presents early results on an accurate geometrical and physical 3D FE modelling of a full scale bending tests with the potential to describe both materials’ macro and micro behaviours. With a focus on the modelling of the concrete elements, this study leverages experimental tests to assess robustness of some variables at the FE models, recommending a novel approach for accurate modelling.Postprint (published version

Supporting Urban Search and Rescue with digital assessments of structures and requests of response resources

First responders, including structural engineers and firefighters, inspect buildings and identify the structural integrity of buildings within a disaster affected area. The performance of their inspection and dissemination of the assessment information are critical to Urban Search and Rescue (US&R) operations. This paper presents an innovative approach for structural assessment and resource requests through an application – Supporting Urban Preparedness and Emergency Response using Mobile Ad hoc Network (SUPER-MAN). The goal of this research is to address challenges encountered in the current practice for structural engineers and first responders to inspect and disseminate building damage assessments and resource requests more efficiently to support US&R. The SUPER-MAN system is equipped with Radio Frequency Identification (RFID) tags, as the storage device of assessment information on the disaster site, and a Mobile Ad hoc Network (MANET) with a Dynamic Source Routing (DSR) implementation for communication. SUPER-MAN strengthens responders’ situational awareness, reduces confusion of inconsistent assessment formats, and automates information dissemination and editing. As a result, lifesaving operations are adequately prioritized, risk of first responders are minimized, and requests of response resources are facilitated. Results obtained from field trials carried out at the Illinois Fire Service Institute with a simulated disaster scenario and computer simulations of the MANET are presented to highlight the benefits provided by SUPER-MAN

Culinary and sensory traits diversity in the Spanish Core Collection of common beans (Phaseolus vulgaris L.)

The Spanish National Plant Genetic Resource Center's core collection of bean germplasm includes 202 accessions selected from more than 3000 accessions in function of passport data, seed phenotype, genetic background, and agronomic traits. To acquire more useful information about these accessions, we cultivated and characterized them for sensory and culinary traits. We found considerable variation for culinary and sensory traits of the cooked beans (mean coefficients of variation: 41% for the sensory traits and 40% for the culinary traits). The large dataset enabled us to study correlations between sensory and culinary traits and among these traits and geographic origin, seed color, and growth habit. Greater proportion of white in the seed coat correlated positively with brightness and negatively with mealiness (r=0.60, r=-0.60, p<0.001, respectively). Mealiness correlated negatively with seed-coat roughness and rate of water absorption (r=-0.60, r=-0.53, p<0.001, respectively). Materials of Andean origin had lower seed-coat brightness (p<0.01) and seed-coat roughness, and greater seed-coat perceptibility, mealiness, flavor, and aroma (p<0.001) than materials of Mesoamerican origin. Growth habit failed to correlate with culinary or sensory traits