A comparative study of beam design curves against lateral torsional buckling using AISC, EC and SP

Introduction. Structural stability is an essential part of design process for steel structures and checking the overall stability is very important for the determination of the optimum steel beams section. Lateral torsional buckling (LTB) normally associated with beams subject to vertical loading, buckling out of the plane of the applied loads and it is a primary consideration in the design of steel structures, consequently it may reduce the load currying capacity. Methods. There are several national codes to verify the steel beam against LTB. All specifications have different approach for the treatment of LTB and this paper is concentrated on three different methods: America Institute of Steel Construction (AISC), Eurocode (EC) and Russian Code (SP). The attention is focused to the methods of developing LTB curves and their characteristics. Results. AISC specification identifies three regimes of buckling depending on the unbraced length of the member ( Lb ). However, EC and SP utilize a reduction factor (χ LT ) to treat lateral torsional buckling problem. In general, flexural capacities according to AISC are higher than those of EC and SP for non-compact sections

Effect of using 3D-printed shell structure for reinforcement of ultra-high-performance concrete

This study aims to investigate the effect of 3D-printed polymer shell reinforcemen ton ultra-high-performance concrete. The mechanical properties of ultra-high-performance polymer reinforced concrete have been investigated. At first, the 3D-printed shell reinforcements were designed using 3D Max and Rhino 6 software. Then, each was fabricated through the fused deposition modeling method and positioned into the cubic, cylindrical, and prismatic molds. In the next step, the prepared Ultra-High-Performance Concrete mixture was poured into the molds, and the samples were cured for 28 days. Finally, the compressive, tensile, and flexural strength tests were carried out on the samples. The results indicated that the compressive, tensile, and flexural strengths of reinforced samples were lower than that of the unreinforced ones, respectively. Although including 3D-printed reinforcement decreased the mechanical properties of the Ultra-High-Performance Concrete samples, it changed the fracture mechanism of concrete from brittle to ductile

Effect of gelatin powder, almond shell, and recycled aggregates on chemical and mechanical properties of conventional concrete

The objective of the research is to study the effect of different additives on the conventional concrete. In this term, three types of materials have been added to the concrete: gelatin powder as the binder, recycled aggregates, and almond shell as the fine and coarse aggregates. Several experiments have been made tо determine physical and mechanical properties, such as test for compressive and tensile strengths, for impact loading strength, durability test (water absorption) and deep penetration tests. Moreover, the microstructure results for the new type of concrete have been studied by means of scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDXS). The results show that when 70 kg of gelatin powder is added to 1 m3 of concrete, the concrete’s compressive strength and tensile strength are improved more than 22%; during impact loading the first and ultimate cracks are 11 and 129 by numbers, and the first and ultimate cracks’ strength is more than 223 and 2346 J respectively. The durability of sample from concrete with additional gelatin has been improved. SEM results illustrate that the weakness of almond shell concrete is related to cracks and voids between the cement matrix and almond shell. The voids of gelatin concrete are higher than that of conventional concrete. The conventional concrete has smooth crystals, and gelatin concrete has sharp and cubic crystals. EDXS results show that chemical content of these two types of concrete is different: conventional concrete contains silicon, while EDXS results show that chemical content of these two types of concrete is different: conventional concrete contains silicon, while gelatin concrete contains calcium and also C-S-H gel is generated in it

Экспериментальное и численное исследование тонкостенных балок двутаврового сечения при изгибе и кручении

The aim of the research - to investigate the behavior of thin-walled beam I-section loaded with bending and torsion using theoretical, numerical, and experimental approaches. In this paper, the main criteria for consideration of the different methods of analysis is the geometric characteristic of the section. The results obtained by the finite element method, the numerical method, as well as experimental data are compared. The analysis by finite element method by considering an additional degree of freedom at a node to include the restrained torsion and the dimension of the stiffness matrix is thus 14×14. The results of the calculation according to this theory are compared with the numerical solution obtained using finite element software, and with the results of the experiment. The I-beam section subject to bending with torsion is considered. The deformations, strain, and stress distributions of open thin-walled structures subjected to bending and torsion are presented using experimental methods. The comparative results for the angle of twisting, deformations, and normal stresses in the frame element subjected to combined loading are displayed graphically. To evaluate the results, a theoretical, numerical, and experimental investigation of I-beam behavior under bending and restrained torsion was carried out. As a result of the comparison, it was revealed that the results obtained according to the refined theory proposed by the authors have good convergence with experimental data and are also quite close to the values obtained using commercial software.Цель работы - исследовать поведение тонкостенной балки I сечения, нагруженной изгибом и кручением, используя теоретические, численные и экспериментальные подходы. В данной работе основным критерием для рассмотрения различных методов анализа является геометрическая характеристика сечения. Сравниваются результаты, полученные методом конечных элементов, численным методом, а также экспериментальные данные. При анализе методом конечных элементов учитывается дополнительная степень свободы в узле для включения повторно деформированного кручения, таким образом, размерность матрицы жесткости составляет 14×14. Результаты расчета по данной теории сравниваются с численным решением, полученным с помощью программы конечных элементов, и с результатами эксперимента. Рассматривается двутавровое сечение балки, подверженной изгибу с кручением. Представлены деформации, напряжения и распределения напряжений открытых тонкостенных конструкций, подверженных изгибу и кручению, с использованием экспериментальных методов. Сравнительные результаты для угла закручивания, деформаций и нормальных напряжений в элементе рамы, подвергнутом комбинированному нагружению, отображены графически. Для оценки полученных результатов проведено теоретико-калькуляционное, численное и экспериментальное исследование поведения двутавровой балки при изгибе и ограниченном кручении. Выявлено, что результаты, полученные в соответствии с предложенной авторами уточненной теорией, имеют хорошую сходимость с экспериментальными данными и достаточно близки к значениям, полученным с помощью коммерческого программного обеспечения

Влияние порошка желатина, миндальной скорлупы и вторичных заполнителей на химические и механические свойства обычного бетона

The objective of the research is to study the effect of different additives on the conventional concrete. In this term, three types of materials have been added to the concrete: gelatin powder as the binder, recycled aggregates, and almond shell as the fine and coarse aggregates. Several experiments have been made tо determine physical and mechanical properties, such as test for compressive and tensile strengths, for impact loading strength, durability test (water absorption) and deep penetration tests. Moreover, the microstructure results for the new type of concrete have been studied by means of scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDXS). The results show that when 70 kg of gelatin powder is added to 1 m3 of concrete, the concrete’s compressive strength and tensile strength are improved more than 22%; during impact loading the first and ultimate cracks are 11 and 129 by numbers, and the first and ultimate cracks’ strength is more than 223 and 2346 J respectively. The durability of sample from concrete with additional gelatin has been improved. SEM results illustrate that the weakness of almond shell concrete is related to cracks and voids between the cement matrix and almond shell. The voids of gelatin concrete are higher than that of conventional concrete. The conventional concrete has smooth crystals, and gelatin concrete has sharp and cubic crystals. EDXS results show that chemical content of these two types of concrete is different: conventional concrete contains silicon, while EDXS results show that chemical content of these two types of concrete is different: conventional concrete contains silicon, while gelatin concrete contains calcium and also C-S-H gel is generated in it.Цель исследования - определить влияние различных добавок на свойства обычного бетона. В бетонную смесь внесены три вида добавок: желатиновый порошок в качестве связующего, вторичные заполнители и миндальная скорлупа в качестве мелкого и крупного заполнителей. Проведено исследование по определению физико-механических свойств бетона с указанными добавками: прочности на сжатие и растяжение, испытания на ударную нагрузку, на долговечность (водопоглощение) и на глубину проникновения влаги в бетон. Микроструктура бетона изучена с помощью сканирующей электронной микроскопии (SEM) и энергодисперсионной рентгеновской спектроскопии (EDXS). Установлено, что при добавлении 70 кг желатинового порошка на 1 м3 бетона его прочность на сжатие и растяжение увеличилась более чем на 22 %; под действием ударной нагрузки начальное и предельное количество трещин составляет 11 и 129, а начальная и предельная прочность трещинообразования - более 223 и 2346 Дж соответственно. Кроме того, показатели долговечности лучше у бетона с добавлением желатина. Результаты, полученные при помощи SEM, демонстрируют, что пониженная прочность бетона с добавлением миндальной скорлупы связана с трещинами и пустотами между цементной матрицей и миндальной скорлупой. Пустоты в бетоне с желатином выше, чем в обычном бетоне. Структура обычного бетона имеет вид гладких кристаллов, а бетона с желатином - острые и кубические кристаллы. Результаты, полученные с помощью EDXS, показали различие в химическом составе: обычный бетон содержит кремний, тогда как бетон с добавкой желатина в вышеуказанных пропорциях содержит кальций и в нем образуется гель C-S-H