Модель сопротивления срезу бетонных элементов, армированных стержнями из полимерных композитов

V. V. Tur, A. P. Varabei. MODEL OF SHEAR RESISTANCE OF CONCRETE ELEMENTS REINFORCED WITH FRP BARSВведение. Проблема сопротивления срезу железобетонных элементов без поперечного армирования по-прежнему остаётся одной из наиболее дис-куссионных в теории конструкций из бетона. Новый интерес к проблеме возник в связи применением в конструкциях из бетона в качестве продольной арматуры стержней из полимерных композитов (FRP). Рассмотрены модели сопротивления срезу, внесенные в нормативные документы и сформулированные в виде предложений для элементов, армированных стальными стержнями и стержнями из FRP. Показано, что для формулирования модели сопротивления срезу элементов, армированных FRP в качестве основы, может быть принята теория критической наклонной трещины (CSCT). Однако её положения не могут быть применены напрямую без соответствующих корректировок, в частно-сти касающихся определения ширины раскрытия критической наклонной трещины. Материалы и методы. Для определения сопротивления срезу самонапряженных бетонных элементов, армированных стержнями из полимерных композитов, разработана модифицированная модель. Данная модель, использующая итерационную процедуру, позволяет определять отдельный вклад в полное сопротивление срезу каждой из основных его составляющих, с учетом формы потенциальной наклонной трещины, принятой в соот-ветствии с положениями теории критической трещины среза (CSCT), а также ширины раскрытия наклонной трещины на уровне продольного армирования, определенной по закону «сцепление-проскальзывание» для FRP-стержней. Результаты: Предложенная модифицированная модель сопротивления срезу верифицирована на фоне опытных данных, полученных как в собственных исследованиях, так и другими авторами (база данных включала 374 элемента). Основываясь на результатах параметрического исследования, предложен феноменологический критерий сопротивления срезу для гибких элементов, армированных стержнями из полимерных композитов, на основе которого разработана упрощенная расчетная модель, позволяющая определять сопротивление срезу бетонных элементов, армированных FRP-стержнями, без необходимости расчета всех составляющих перерезывающей силы. Выводы: Представленная модель сопротивления срезу гибких самонапряженных элементов, армированных стержнями из полимерных композитов, отражает физическую сущность явления среза, применима к различным случаям и схемам нагружения

Prediction of shear strength of deep beam using genetic programming

This research project consists of Genetic Programming (GP) to predict an empirical model for the convoluted non-straight relation between distinct parameters related with Reinforced Concrete (RC) deep beam and its ultimate shear capacity. It is a manifestation of artificial intelligence and thoughts, which is focused around the Darwinian hypothesis of evolution and genetics. The structural and size intricacy of the empirical model advances as a component of the prediction. Model evaluated by GP is developed specifically from experimental database accessible from prior literature. The legitimacy of the acquired model is analyzed by comparing the GP response and the shear capacity ascertained according to distinctive design codes. The created model produced is utilised for study of relationship between the shear strength of deep beam and its distinct influencing parameters

A Feasibility Study of BBP for predicting shear capacity of FRP reinforced concrete beams without stirrups.

yesShear failure of concrete elements reinforced with Fiber Reinforced Polymer (FRP) bars is generally brittle, requiring accurate predictions to avoid it. In the last decade, a variety of artificial intelligence based approaches have been successfully applied to predict the shear capacity of FRP Reinforced Concrete (FRP-RC). In this paper, a new approach, namely, biogeography-based programming (BBP) is introduced for predicting the shear capacity of FRP-RC beams based on test results available in the literature. The performance of the BBP model is compared with several shear design equations, two previously developed artificial intelligence models and experimental results. It was found that the proposed model provides the most accurate results in calculating the shear capacity of FRP-RC beams among the considered shear capacity models. The proposed BBP model can also correctly predict the trend of different influencing variables on the shear capacity of FRP-RC beams

Prediction of Compressive Strength using Genetic Programming Involving NDT Results

Compressive strength of concrete is major parameter to assess the overall quality of concrete as other mechanical prosperities are directly related to the compressive strength. It can be determined using the destructive (DT) and non-destructive testing (NDT) methods. The destructive testing method is carried out by crushing the specimen to failure while the non-destructive is carried out without destroying the concrete specimen. The destructive method is time taking process and required equipment’s and power. Whereas the NDT methods like the rebound (Schmitz) hammer and Ultrasonic Pulse velocity (UPV) are most popular because they are handy, quicker and easy to use. Though the NDT methods are much quicker; their values are more of an approximation than exact compressive strength values. They are also machine specific, hence a calibration curve is provided by supplier which may not be reliable. The Indian code recommends about 25% variation in results, which is very high. The newly developed soft computing techniques like ANN, Fuzzy logic, Genetic programming etc. may be used to prepare a better numerical model correlating DT and NDT results. Hence the aim of the present study is to propose a model correlating the compressive strength obtained from destructive and non-destructive methods by using Genetic Programming. The whole work involves casting of 100 cubes of 150mm size belonging to of different grades of concrete. They were tested under compression following DT and NDT methods. These data were used for modelling ie.(70% for training and 30% for testing ) in GP. The modelling is done two ways, first by using variables as weight and Rebound values and secondly by using weight, rebound values and UPV values. The models obtained were found to be in good agreement with actual values imparting 6.744 % and 7.4434% error respectively

A simple formulation for early-stage cost estimation of building construction projects

U okviru ovog istraživanja poboljšana je formula koja omogućuje jednostavnu, točnu i brzu procjenu troškova u ranim fazama građevinskih projekata (ESCE). Spomenutu formulu za procjenu ESCE-a razvili su autori na temelju umjetnih neuronskih mreža i evolucijskog programiranja gena. Kvantitativna analiza provedena je na stotinu građevinskih projekata, te je izrađen odgovarajući niz podataka. Taj niz podataka analiziran je pomoću većeg broja umjetnih neuronskih mreža kako bi se odredile varijable koje utječu na procjenu ESCE-a. Konfiguracija algoritma provedena je pomoću evolucijskog programiranja gena, te je na temelju te konfiguracije izrađena formula ESCE. Ta formula omogućuje dovoljno preciznu procjenu ESCE-a. Primjena predložene formule za određivanje troškova u ranoj fazi projekta omogućuje brže i jednostavnije izračunavanje troškova, ali isto tako sprječava pojavu bilo kakvih razlika do kojih bi moglo doći zbog individualnog pristupa proračunu.This study is aimed at improving a formula that enables easy, correct, and fast estimation of an Early-Stage Cost of Buildings (ESCE). This formula, enabling estimation of ESCE, was developed by the authors based on artificial neural networks and gene expression programming. A quantity survey was conducted for a hundred construction projects, and a data set was created. This data set was analysed with many Artificial Neural Networks to determine the variables that affect ESCE. An algorithm configuration was made with Gene Expression Programming, and the ESCE formula was created using this algorithm configuration. This formula estimates ESCE with satisfactory precision. The use of the proposed formula in the early-stage building cost calculations is important not only for faster and easier cost calculation but also to prevent any differences that may arise due to the individual making the calculations

Shear strength of concrete beams reinforced with glass fiber reinforced polymer bars without stirrups

The use of fiber reinforced polymer (FRP) bars as an alternative to steel bars for reinforced concrete (RC) structures is gaining acceptance among the structural engineers. The investigation of structure performance of FRP-RC members has become a critical issue. Extensive researches have been conducted to investigate the shear behavior of RC members with FRP bar. However, the shear strength design of FRPRC beams is similar to that of RC beams with steel bar except that the mechanical properties of FRP bars which affect the shear strength design shall be considered. The focus of this research is to investigate the shear behavior of FRP-RC beams. A total of 18 RC beams were constructed and tested up to failure, the test beams included 10 GFRP-RC beams and 8 steel-RC beams. In order to realize the occurrence of the shear failure, all tested beams were designed without stirrups. The test variables were the reinforcement ratio (ρ), shear span to depth ratio (a/d), depth of beam (d), and concrete compressive strength

Experimental investigation on the shear characteristics of GFRP reinforcement systems embedded in concrete.

To mitigate the deterioration of steel-reinforced concrete members, a fiber-reinforced polymers (FRPs) system has been introduced and has increasingly been used to replace the conventional steel reinforcing bar. However, questions remain about the performance of the Glass Fiber Reinforced Polymer (GFRP) reinforcing bar in concrete with varied stress orientation and shape. The GFRP reinforcement is an anisotropic material that possesses low strength for the transverse direction. This paper presents the results of the shear performance of GFRP reinforcement crossing varied crack angles. Fifteen push-off specimens were tested to investigate the shear characteristics of the GFRP and steel reinforcement. Tests were performed with three varied orientations of steel and GFRP reinforcement embedded in concrete: 90, 45, and 135-degrees with respect to the shear crack plane. In addition, the group-effect of GFRP reinforcement is also investigated with two reinforcing bars. Results indicate that the contributions of aggregate interlock and GFRP reinforcement are significantly varied depending on the bar orientation. Varied orientation of the GFRP bar across the crack plane allows for different failure modes of the reinforcement and absorbed energy capacities. Maximum shear capacity is obtained in specimen with 135-degree orientation accompanying with minimized crack width. This indicates that 135-degree orientation promoted higher aggregate interlock and sufficient development of strength in the reinforcement

Prediction of shear strength of FRP-reinforced concrete beams without stirrups based on genetic programming

WOS: 000292790000001The use of fibre reinforced polymer (FRP) bars to reinforce concrete structures has received a great deal of attention in recent years due to their excellent corrosion resistance, high tensile strength, and good non-magnetization properties. Due to the relatively low modulus of elasticity of FRP bars, concrete members reinforced longitudinally with FRP bars experience reduced shear strength compared to the shear strength of those reinforced with the same amounts of steel reinforcement. This paper presents a simple yet improved model to calculate the concrete shear strength of FRP-reinforced concrete slender beams (a/d > 2.5) without stirrups based on the gene expression programming (GEP) approach. The model produced by GEP is constructed directly from a set of experimental results available in the literature. The results of training, testing and validation sets of the model are compared with experimental results. All of the results show that GEP is a strong technique for the prediction of the shear capacity of FRP-reinforced concrete beams without stirrups. The performance of the GEP model is also compared to that of four commonly used shear design provisions for FRP-reinforced concrete beams. The proposed model produced by GEP provides the most accurate results in calculating the concrete shear strength of FRP-reinforced concrete beams among existing shear equations provided by current provisions. A parametric study is also carried out to evaluate the ability of the proposed GEP model and current shear design guidelines to quantitatively account for the effects of basic shear design parameters on the shear strength of FRP-reinforced concrete beams. (C) 2011 Elsevier Ltd. All rights reserved

NUMERICAL SIMULATION OF CONCRETE BEAMS WITH DISCONTINUITY REGIONS REINFORCED WITH NONMETALLIC REINFORCING BARS

Nonmetallic Glass Fiber-Reinforced Polymer (GFRP) reinforcing bars are considered a viable alternative to the conventional steel reinforcement because of their high strength-to-weight ratio and noncorrosive nature. This research aimed to investigate the nonlinear structural behavior of GFRP-reinforced concrete beams with discontinuity regions (D-regions) through numerical analysis. Three-dimensional (3D) numerical models were developed to simulate the nonlinear structural behavior of GFRP-reinforced deep beams with and without web openings. The models adopted realistic constitutive laws that accounted for the nonlinear behavior of the materials used. Predictions of the numerical models were validated against published experimental data. A parametric study was conducted to examine the effect of key variables on the structural behavior of GFRP-reinforced deep beams with and without web openings. The interaction between the concrete compressive strength (fc’), shear span-to-depth ratio (a/h), size and location of the web opening was elucidated. Simplified analytical formulas capable of predicting the shear capacity of GFRP-reinforced beams with D-regions were introduced based on an inverse analysis of results of the numerical simulation models. Predictions of the proposed analytical formulas were in good agreement with the results of the simulation models

Experimental and finite element analysis of the shear behaviour of UHPC beams

Master's Thesis Civil and Constructional Engineering BYG508 - University of Agder 2019The flexural behavior of reinforced concrete beams isobviously defined and can be managed with reasonableaccuracy.However, a solution has not been obtained for the shear capacity of beams, especially those without shear reinforcement, though numerous models have been established using different approaches. The reason is due to the complexity of shear behavior of reinforced concretebeams,where the load transfer through various componentsof concrete. In addition to this, there is also the effect of reinforcement and cross-section of the memberswhichis linked with dowel action and geometric parameters.All these aspects cause a challenge in quantifying the contribution of each parameter towards shear strength. The uncertainties of these parameters are the reason for not having a principal shear model inthe measurement of the shear capacity of reinforced or un-reinforced concrete beams.This master thesis hasthereforefocused on enhancing the shear resistance of reinforced concrete beams,among a suitable fibre dosage,and the use of UHPC. Experiments, as well as numerical analyses, have been conducted in this thesis. The experiments were divided into 3 parts: cubic and cylinder specimens at different ages to determine the compressive strength,as well as the modulus of elasticity, afour-point bending test on beams to investigate shear strength, and lastly, a three-point bending test on small-scale prismsto determinethe flexural tensile strength.In order to reach a deeper understanding of the shear behavior, finite element (FE) analyses were implemented utilizing the computer software ANSYS. Through ANSYS, several sets of analyses were completed on the simulation offour-point beam bending tests.The large-scale beams were all tested at the mechatronic laboratory at the University of Agder,usingthe four-point bending test. The midspan deflection was measured based on the available machines and a computer was used to register the values.The digital image correlation technique was used to extract the load-deflection curve of several points near to the diagonal shear crack. The experimental results confirm that using the fibrein UHPC beams,will increase the shear strength and the ductility. Replacing stirrups completely with fibres, leads to a reduction of beam depth as well as a decrease in stirrup assembly time.The results were compared with the estimations by Australian guideline, ACI 522, Sharma, Ashour et al., Narayana et al. and Imam et al. The results show that Ashour et al. and Narayana et al. formulas gave the most accurateprediction, while the formula proposed by Sharma wasthe the least accurate.Most of the Finite element modelingresultscorrelated well with ourexperimental results. Hence, using ANSYS may be therightsolution in the future to investigate UHPC beams and to develop design theories of UHPFRC