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Currently, there are different options to increase the ultimate resistance of plate girders subjected to patch loading. Some of these alternatives include the use of closely spaced transverse stiffeners and the use of longitudinal stiffeners. Nevertheless, recent investigations have demonstrated that the resistance is also improved by using delta stiffeners, which are obtained by welding two plates between the web plate and the loaded flange. This paper aims at studying the elastic buckling behavior of slender plate girders designed following AASHTO norms with delta stiffeners subjected to patch loading. The research is carried out by means of eigenvalue analysis using the finite element method. A parametric study is performed to evaluate the influence of various geometrical parameters on the buckling coefficient of the girder. Finally, design recommendations are suggested based on the obtained results., En la actualidad existen diferentes opciones para incrementar la resistencia última de vigas esbeltas sujetas a cargas concentradas. Algunas de estas alternativas incluyen el uso de rigidizadores transversales cercanamente espaciados y la utilización de rigidizadores longitudinales. Sin embargo, estudios recientes han demostrado que la resistencia también mejora mediante el uso de rigidizadores tipo delta, los cuales consisten en dos láminas soldadas entre alma de la viga y la aleta cargada. Este trabajo se enfoca en el estudio del comportamiento de pandeo elástico de vigas esbeltas diseñadas con normas AASHTO con rigidizadores tipo delta sometidas a carga concentrada. El estudio se realiza a través del análisis de autovalores usando el método de elementos finitos. Se realiza un análisis paramétrico para determinar la influencia de diferentes variables geométricas sobre el coeficiente de pandeo de la viga. Finalmente, a partir de los resultados obtenidos se sugieren algunas recomendaciones de diseño.

The increasing use of stainless steel in construction has led to the need of developing resistance models for structural elements made of this material. Unlike carbon steels, stainless steel alloys exhibit stress-strain curves with a pronounced strain hardening capacity and reasonable ductility that should be considered in the design. This difference in behavior makes the formulations used for carbon steel conservative when designing with stainless steel. Therefore, this paper presents a comparative analysis of resistance models for slender austenitic stainless-steel beams subject to concentrated loads. First, the failure mechanisms of stainless-steel beams are presented using a nonlinear finite element model. From this validated numerical model, a database obtained from a parametric analysis that covers a wide range of geometries is presented. Subsequently, this database is used to perform a comparison between various resistance models available in the literature. These models correspond to both international design codes and models obtained through machine learning. Finally, the numerical results show considerable improvement in the predicted ultimate resistances for slender stainless steel plate girders subjected to patch loading., El creciente uso de acero inoxidable en la construcción ha creado la necesidad de desarrollar modelos de resistencia para elementos estructurales fabricados con este material. A diferencia de los aceros de carbono, las aleaciones de acero inoxidable exhiben curvas esfuerzo-deformación con una pronunciada capacidad de endurecimiento por deformación y ductilidad razonable que deben ser consideradas en el diseño. Esta diferencia en el comportamiento hace que las formulaciones utilizadas para acero al carbono sean conservadoras al momento de diseñar con acero inoxidable. Por lo tanto, este trabajo presenta un análisis comparativo de modelos de resistencia para vigas esbeltas de acero inoxidable sometidas a cargas concentradas. En primer lugar, se presentan los mecanismos de falla de vigas de acero inoxidable utilizando un modelo no lineal por elementos finitos. A partir de este modelo numérico validado se presenta una base de datos obtenida a partir de un análisis paramétrico que cubre un amplio rango de geometrías. Posteriormente, esta base de datos se utiliza para realizar una comparación entre varios modelos de resistencia disponibles en la literatura. Estos modelos corresponden tanto a códigos de diseño internacionales como a modelos obtenidos a través de aprendizaje de máquina (machine learning). Finalmente, los resultados muestran una mejora considerable en la predicción de la resistencia última de las vigas esbeltas de acero inoxidable sometidas a cargas concentradas.

Currently, one of the most used steel bridge assembly methods is the Incremental Launching Method (ILM). Its practical application consists in passing the bridge assembly through a launching shoe as well as over each support pile. For steel plate girders, a concentrate vertical reaction also known as patch loading is generated over one the flanges when ILM is employed, and depending on the geometrical and material properties of the girder, buckling failure in the web panel may occur. To overcome this type of failure, plate girders are reinforced with longitudinal stiffeners. Therefore, this paper aims at investigating the effect of the bearing length on the elastic buckling behavior of longitudinally stiffened girder webs subjected to patch loading. Buckling coefficients of longitudinally stiffened girder webs are calculated by means of linear finite element analysis. Furthermore, a parametric analysis is performed to study the influence of other geometric parameters such as the panel aspect ratio and the geometrical properties of the longitudinal stiffener on the buckling coefficient. The results show that for longitudinally stiffened girder webs the buckling coefficient increases with the loading length. However, this conclusion is considerably affected by other factors such as the position of the stiffener, and panel aspect ratios., Peer Reviewed, Postprint (published version)

Currently, the AISC Specification provides guidance for the calculation of the ultimate strength of unstiffened plate girder webs subjected to concentric edge loads. Specifications consider three categories: local web yielding, web crippling, and sideway web buckling. Based on previous studies, the presence of longitudinal stiffeners in the web has not been considered in the calculation procedures. Longitudinal stiffeners in steel plate girders are primarily used to increase bending. In the last two decades, a number of projects regarding the positive effect of longitudinal stiffening on the strength of plate girder webs to concentrated load have been conducted around the world. The results have shown that this type of stiffening enhances ultimate strength for web crippling, depending on the position of the stiffener that modifies the slenderness of the directly loaded panel and flexural and torsional rigidities of the stiffener. This paper presents a methodology for the consideration of longitudinal stiffening on the ultimate strength of plate girders webs subjected to concentrated loads. The methodology is based on the plastic collapse mechanism observed experimentally, in which plastic hinges are formed in the loaded flange and yield lines result in the portion of the web limited by the loaded flange and stiffener. Then, a closed-form solution accounting for the influence of the stiffener is developed following the current expression available in the AISC Specification. Theoretical predictions are compared with available test results, showing that the predicted ultimate loads are in good agreement with experimental results., Peer Reviewed, Postprint (author's final draft)

Incremental launching is one of the common steel bridge assembly methods used nowadays, its practical application consists in passing the bridge assembly through the launching shoes as well as over each support pile. In some cases, when plate girders are used, it is usual to find longitudinal stiffeners reinforcement in order to prevent web local buckling produced by the vertical reaction acting in the support pile. A considerable number of studies have focused on evaluating the impact of a single stiffener on the resistance of plate girder subjected to patch loading. However, the effect of multiple longitudinal stiffened plate girders subjected to lengthy compressive load has received little attention. Therefore, this paper aims at studying the influence of load bearing length on the ultimate strength of multiple longitudinally stiffened webs subjected to compressive loads. Patch loading resistance is numerically calculated using a previously validated nonlinear finite element analysis. Subsequently, a parametrical study is conducted to investigate the effect of the aforementioned load length and the relative position and size of the stiffeners on the ultimate strength, Peer Reviewed, Postprint (published version)

Currently, the AISC code provides guidance for the calculation of the ultimate strength of unstiffened plate girder webs subjected to concentric edge loads. Specifications consider three categories: local web yielding, web crippling, and sideway web buckling. Based on previous studies, the presence of longitudinal stiffeners in the web has not been considered in the calculation procedures. Longitudinal stiffeners in steel plate girders are primarily used to increase bending and shear strength. In the last two decades, a number of projects regarding the positive effect of longitudinal stiffening on the strength of plate girder webs to concentrated load have been conducted around the world. The results have shown that this type of stiffening enhances ultimate strength for web crippling depending on the position of the stiffener that modifies the slenderness of the directly loaded panel; and flexural and torsional rigidities of the stiffener. This paper presents a methodology for the consideration of longitudinal stiffening on the ultimate strength of plate girders webs subjected to concentrated loads. The methodology is based on the plastic collapse mechanism observed experimentally, in which plastic hinges are formed in the loaded flange and yield lines result in the portion of the web limited by the loaded flange and stiffener. Then, a closed-form solution accounting for the influence of the stiffener is developed following the current expression available in the AISC specifications. Theoretical predictions are compared with available test results, showing that the predicted ultimate loads are in good agreement with experimental results., Postprint (published version)

In the construction of traditional composite bridges whose structure consists of plate girders, the concrete slabs of the decks are often casted before launching. These thin-walled webs are occasionally reinforced with longitudinal stiffeners to increase bending and shear strengths, and for bridges erected by incremental launching, these stiffeners also provide an enhancement for patch loading resistance. Experimental works have shown that ultimate resistance to patch loading is highly dependent on the size, relative position and shape of the longitudinal stiffener. Nonetheless, a comparison between those three factors should be carried out in order to establish the optimum configuration of longitudinal stiffening for webs under compressive forces. Hence, this study attempts to compare the increase of ultimate strength of a slender I-girder subjected to concentrated load using open and closed section types of stiffeners, evaluating three different stiffeners configurations: i) a single open section stiffener, ii) multiple open section stiffeners, and iii) a single closed section stiffener. The nonlinear computations were performed using a finite element analysis parametric model, where the relative position and size of the stiffeners are varied to cover a wide range of geometries., Peer Reviewed, Postprint (published version)

En la construcción tradicional de puentes mixtos acero-concreto cuya estructura consiste en vigas tipo placa, las losas de hormigón de las cubiertas son a menudo vaciadas antes del ensamblaje. Siendo estas estructuras de espesor delgado reforzadas con rigidizadores longitudinales para incrementar la resistencia a corte y pandeo, y soportar las fuerzas presentes durante la erección del puente. Estos rigidizadores también proveen una mejora a la resistencia de carga concentrada. En la literatura, en muchos estudios se ha investigado el comportamiento del pandeo lineal de vigas esbeltas simplemente apoyadas sometidas a carga concentrada, demostrando que la resistencia a carga crítica aumenta con el uso de rigidizadores longitudinales. Por otra parte, también se ha demostrado que un rigidizador colocado a una quinta parte de la altura de la viga aumenta considerablemente la resistencia a carga crítica de una viga sometida a carga concentrada. Sin embargo, en estos estudios la carga concentrada solamente es aplicada usando un rango limitado de valores. Por lo tanto, el objetivo de este trabajo es investigar la influencia de la longitud de carga sobre el coeficiente de pandeo, en vigas esbeltas con un rigidizador longitudinal sujetas a carga concentrada. Los coeficientes de pandeo serán calculados numéricamente por medio de un análisis lineal en elementos finitos, la carga concentrada se variará con el propósito de estudiar diferentes casos de gran longitud. Los resultados muestran que el coeficiente de pandeo incrementa con la longitud de carga para diferentes relaciones de aspecto de la viga., Postprint (published version)

Durante la erección de puentes de acero usando el método de empujes sucesivos, el ensamble de la cubierta se mueve a través de las zapatas de desplazamiento y también sobre cada pila de soporte. Como resultado de esto se genera una reacción vertical que actúa sobre la aleta de la viga, transmitiendo esta fuerza al alma de la viga lo que puede inducir un pandeo localizado. Para evitar este problema de inestabilidad, una alternativa es el uso de rigidizadores longitudinales. En la práctica las vigas esbeltas hacen uso de múltiples rigidizadores para incrementar su resistencia a corte y flexión. En la literatura la influencia de un solo rigidizador sobre la resistencia a cargas concentradas en vigas esbeltas ha sido ampliamente investigada, sin embargo el impacto de múltiples rigidizadores longitudinales y grandes cargas concentradas ha recibido poca atención. Por lo tanto el objetivo de este trabajo se enfoca en estudiar la influencia de rigidez a flexión y posición relativa de los rigidizadores sobre la carga critica de pandeo de una viga con rigidización múltiple. La carga crítica es calculada por medio de un análisis por Elementos Finitos. Igualmente, se realizará un análisis paramétrico para determinar la influencia de los parámetros geométricos así como de la longitud de carga y varias relaciones de aspecto., Postprint (published version)

A pollution management system comprises an array of one or more inlets and at least one outlet. The one or more inlets are arranged to collect polluted air and supply said polluted air to a polluted air treatment element. The one or more inlets each comprise a respective inlet sensor for measuring a level of pollution at the inlet, and the at least one outlet comprises an outlet sensor for measuring a level of pollution at the outlet. The inlet sensors and the outlet sensor are arranged to provide feedback to the polluted air treatment element.