fib Bulletin 35. Retrofitting of concrete structures by externally bonded FRPs with emphasis on seismic applications (original) (raw)
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Рассмотрено развитие алгоритмов и методов расчета напряженного состояния и прочности толсто-стенных сферических оболочек из бетона, находящихся под воздействием равномерного внешнего дав-ления. Получены аналитическое и численное решения задачи по определению предельного внешнего давления с использованием основных положений теории пластичности, принятых в форме критерия прочности Друкера-Прагера, и программного комплекса ANSYS Workbench. Ключевые слова: бетонная сферическая оболочка, распределенная нагрузка, сферическая конструк-ция, прочность бетона, трехосное сжатие, критерий прочности. The article discusses the development of algorithms and methods for calculating the stress state and strength of thick-walled spherical concrete shells under the influence of uniform external pressure. There have been obtained analytical and numerical solutions of the problem of determining the limiting external pressure using the main principles of the theory of plasticity taken in the form of the Drucker-Prager strength criterion and the ANSYS Workbench software package.
Cement and Concrete Composites, 2020
Проведен сравнительный анализ таксации запасов лекарственных растений на примере лесничеств, расположенных в районе хвойно-широколиственных (смешанных) лесов европейской части Российской Федерации и южно-таежном районе европейской части Российской Федерации. С помощью методов закладки круговых пробных площадей в преобладающем типе леса изучены характерные лекарственные растения-Fragaria vesca L., Aegopodium podagraria L., Urtica dioica L., Oxalis acetosella L., Asarum europaeum L. и Equisetum silvaticum L. Установлен биологический, промысловый, хозяйственный запас лекарственных растений. Рассчитан объем возможных ежегодных заготовок в Вавожском и Увинском лесничествах Удмуртской Республики. Даны рекомендации по вырубке и хозяйственному использованию леса, о необходимости учета воздействия на сохранность и возобновление объемов лекарственных трав при их проведении. Ключевые слова: лекарственные растения, таксация запасов, тип леса, группа возраста, полнота, запас и объем возможных ежегодных заготовок Ссылка для цитирования: Абсалямова С.Л., Абсалямов Р.Р., Поздеев Д.А. Таксация запасов лекарственных растений в лесничествах Удмуртской Республики // Лесной вестник / Forestry Bulletin, 2020. Т. 24. № 3. С. 5-10.
Experimental analysis of mechanical characteristics of FRP materials
2015
Increasing interest about composite materials and their use in the field of civil engineering offer possibility for development of new innovative materials, which could be used as constructive elements. The concept of the composite materials itself, offers possibility of effective exploitation of mechanical characteristics of the separate components till their limit. Mechanical characteristics of each composite material depend on its components. In this paper experiments of different series composite materials, which are different according to used reinforcement and matrix, are presented. Мechanical characteristics of different types of composite materials are discussed in dependence on their components.
The fracture performance of a high-strength concrete reinforced with steel fibers was studied. Tests of notched beams subjected to fracture in the three-point bend configuration were conducted in accordance with RILEM recommendations TC 162-TDF. The R-curve concepts based on load–CMOD responses and the RILEM criteria were used for the performance evaluation of concrete beams reinforced with steel fiber mixtures and loaded up to fracture. Steel fibers of different types (regular and microfibers), in different proportions were employed as the reinforcement. The hybrid-fiber-reinforced concrete demonstrated a superior performance regarding their resistance and toughness properties as a result of interaction between the fibers. Ключевые слова: материалы композитные, бетон армированный волокнами стальными, композиты гибридные, сопротивление разрушению, композиты цементные Изучены характеристики разрушения высокопрочного бетона, армированного стальными волокнами. Испытания балок с над-резами на трехточечный изгиб до разрушения проведены в соот-ветствии с рекомендациями TC 162-TDF международного союза RILEM. Для оценки характеристик бетонных балок, армированных
Modern problems of science and education, 2017
In the scientific article the results of experimental and theoretical studies of the behavior of reinforcement cages – trigonal in the environment of heavy and lightweight concrete with the definition of rational applications and develop recommendations for their use. Performed work study of metal frames of a new type outside the concrete for future comparison with concrete construction products with similar frames. Presents the results of the test frames for various loading schemes. The obtained experimental data allowed to determine the strength and deformability of scaffolds. Identify the causes of the lowering of the rigidity of frameworks for the comparison with the theoretical estimate. The results of the test frameworks allow you to develop a pilot design of precast-monolithic slabs «Yunilit» with the use of heavy and light concrete and to conduct analysis of reinforcement cages with a triangular lattice in such constructions.
Effectiveness of Seismic Base Isolation in Reinforced Concrete Multi-Storey Buildings
2020
The dynamic reaction of a building to earthquake ground motion is the most critical reason for earthquake actuated damage to structures. The basic concept in seismic isolation is to protect the structure from the damaging effects of an earthquake by introducing a flexible support isolating the building from the shaking ground. Seismic isolation consists of essentially the installation of mechanisms such as isolators which decouple the structure from base. In the present study, the seismic response of the reinforced concrete building, base isolated by lead rubber bearings (LRBs) is compared with the seismic response of the same structure which does not have base isolation system. The main objective is to check effectiveness of base isolation system and to find story displacement, story drift and base shear. A time history analysis is carried out for the 10 storey buildings for El Centro earthquake by using SAP2000 software
Корпус высокого давления ядерного реактора разрабатываемого и исследуемого конструктивного решения представляет собой достаточно сложное многокомпонентное сооружение, включающее сило-вые стенки из тяжелого армоцемента и торцовые элементы типа пробок, смещение которых исключено наличием специальных шпонок. Рассматривается расчет толстых конических осесимметричных торцо-вых плит, опертых на коническую поверхность (свободно лежащих на опорах из шпонок) и предназна-ченных для восприятия достаточно высоких уровней воздействий в виде равномерно распределенной нагрузки. Такие толстые плиты могут быть использованы в концевых участках корпусов высокого дав-ления ядерных реакторов, аккумуляторов тепла, автоклавах и т. п. При решении аналитической задачи, основанной на классической теории пластичности, использован программный комплекс Mathcad 15. Ключевые слова: корпус высокого давления, железобетонный торцовый элемент, осесимметричная толстая плита, главные напряжения, внутреннее давление, равномерно распределенная нагрузка, шпон-ка, прочность. The high-pressure housing of the nuclear reactor of the developed and investigated design solution is a rather complex multi-component structure, including the power walls of heavy armored cement and abutting members of the plug type, the displacement of which is excluded by the presence of special dowels. The article discusses the design of axisymmetric reinforced concrete thick plates supported on a conical surface (freely lying on supports made of dowels) and intended for receiving sufficiently high levels of effects in the form of a uniformly distributed load. Such thick plates can be used in the end sections of high-pressure nuclear reactor shells, heat accumulators, autoclaves, etc. In solving the analytical problem based on the classical theory of plasticity, the software package Mathcad 15 was used.
Compósitos de CFRP unidireccionais no reforço de vigas de madeira lamelada-colada
2006
Neste trabalho apresenta-se a campanha de ensaios realizada para avaliar a eficiência da aplicação de dois sistemas compósitos de CFRP no reforço à flexão de vigas de madeira lamelada-colada: o curado "in situ" (manta) e o pré-fabricado (laminado). Cada um dos sistemas de CFRP foi aplicado quer em reforço externo (colagem na face traccionada da viga) quer em reforço interno (colagem na face inferior da penúltima lamela). No caso do reforço interno foi, ainda, avaliada a influência da colagem do CFRP numa cavidade previamente executada na face da lamela a reforçar. Numa fase precedente, avaliou-se a aderência madeira-CFRP por intermédio de ensaios de "pull-off", tendo-se analisado as seguintes variáveis: o tipo de cola, a utilização de primário e o tratamento da superfície.
This article provides an example of the calculation of eccentrically compressed rein- forced concrete elements exposed to dynamic loads and fire effects. The dynamic factor for the concrete under regular conditions is available, and it exceeds one in any case. However, in case of a fire exposure, the value of this factor varies from 0,4 to 0,8, de- pending on the loading rate and temperature. The value of the dynamic factor was identi- fied in the course of an experiment; thereafter, the pattern of influence of the dynamic effect caused by the progressive collapse of buildings and produced onto the bearing capacity and fire resistance of compressed elements of the pylon and the column was identified. ANSYS 12.1 software package was employed to perform the fire resistance analysis of the pylon on the 1st floor of a 59-storey building. The problem was modeled in the 3D formulation. It represented a pylon exposed to static loading and standard fire conditions. For comparison purposes, bearing capacity values were calculated for differ- ent values of the thermal load. The calculation of temperature fields was based on the resolution of boundary value problems of transient heat conduction in capillary-porous bodies. The solution to the problem of the four-sided fire exposure at standard fire tempera- ture values was obtained in characteristic points of the support structure to assess the change in its load-bearing capacity. It is proven that dynamic effects of a fire reduce the bearing capacity of columns by 40 %. Therefore, the analysis of the bearing capacity of structures in terms of their fire resistance should take account of the possibility of progressive collapse of buildings.