10 research outputs found
Corrosion effects on tension stiffening behavior of reinforced concrete
Get PDFThe investigation of corrosion effects on the tensile behavior of reinforced concrete (RC) members is very important in region prone to high corrosion conditions. In this article, an experimental study concerning corrosion effects on tensile behavior of RC members is presented. For this purpose, a comprehensive experimental program including 58 cylindrical reinforced concrete specimens under various levels of corrosion is conducted. Some of the specimens (44) are located in large tub containing water and salt (5% salt solution); an electrical supplier has been utilized for the accelerated corrosion program. Afterwards, the tensile behavior of the specimens was studied by means of the direct tension tests. For each specimen, the tension stiffening curve is plotted, and heir behavior at various load levels is investigated. Average crack spacing, loss of cross-section area due to corrosion, the concrete contribution to the tensile response for different strain levels, and maximum bond stress developed at each corrosion level are studied, and their appropriate relationships are proposed. The main parameters considered in this investigation are: degree concrete cover (c), ratio of of clear corrosion concrete (Cw), cover reinforcement to diameter (d), reinforcement ratio (ρ), rebar diameter (c/d), and ratio of rebar diameter clear to reinforcement percentage (d/ρ)
Investigation of Corrosion Effects on Bond-slip and Tensile Strength of Reinforced Concrete Members
Get PDFThe corrosion effect on tensile strength of RC members is very important to region with high corrosion conditions. In this article a study on finding bond behaviour, crack pattern, crack spacing, and tensile strength of RC members is presented. For this purpose a comprehensive experimental program including reinforced concrete cylanders with different concrete covers and reinforcement ratios under various corrosion rates is conducted. The specimens are located in large tub containing water and salt (5% salt solution) with a devich for accelerated corrosion production. For each specimen, the variation of total tensile strength versus its average strain is plotted and the member behaviour at various load levels is investigated. Average crack spacing, and maximum bond stress developed at each corrosion level are studied and their apporoperiate relationship are proposed. The main parameterrs considerd in this investigation are: corrosion rate (Cw), reinforcement diameter (d), reinforcement ratio (ρ), c/d and d/ρ
The characteristics of ultra-high performance concrete and cracking behavior of reinforced concrete tensile specimens
No full textThe tensile behavior of concrete depends on some factors such as member dimensions, reinforcement ratio, diameter of rebar, strength and elasticity modulus of material. In this research the experimental method is used to examine the characteristics and the behavior of ultra-high performance concrete on the tensile behavior of concrete members reinforced by steel rebar. The results show that increasing the rebar cover on diameter rebar ratio (C/d) increases the initial stiffening before the cracking stage in concrete. Also, by increasing of reinforcement ratio the cracking space decreased
THE EFFECT OF WASTE MARBLE POWDER AND SILICA FUME ON THE MECHANICAL, ENVIRONMENTAL AND ECONOMIC PERFORMANCE OF CONCRETE
No full textOne of the most widely used materials in the construction industry is concrete and one of its main constituent elements is cement. Cement production, in addition to consuming non-renewable natural resources, emits greenhouse gases and pollutes the environment. Waste marble powder (WMP) is an industrial by-product that the marble factory generates considerable amounts during stone processing. WMP mostly not used in the industry nor being recycled and causes serious environmental problems. Silica fume (SF), also known as micro silica, is an ultrafine powder collected as a by-product of the silicon and ferrosilicon alloy production. This paper presents the results of an experimental investigation of mechanical properties carried out on the concrete mixes containing WMP and SF as a partial replacement of Portland Cement (PC). In all concrete mixtures, a constant water/binder ratio was used and concrete mixtures with a target initial slump of 80±10 were prepared. All of the concrete mixtures were assessed in terms of environmental, economic and mechanical aspects. Global warming potential, fossil fuel depletion potential and acidification potential were considered as environmental indicators of concrete mixtures production.
Finally, it was observed that the mechanical properties of concrete containing WMP are improved for replacement ratios up to 10%. The use of SF improved the performance of all mixing designs and compensated for the shortcomings in the mechanical properties of concrete containing high percentages of WMP. Mechanically, the best percentages for simultaneous use of WMP and SF are 5% and 10%, respectively. From an environmental point of view, replacing 20% of WMP and 10% of SF with PC, not only leads to the production of concrete with suitable mechanical properties but also reduces the use of cement by 30% and the resulting environmental pollution. The combined index designed in this study showed that the optimal mix design in terms of mechanical, environmental and economic belongs to a mixture in which 5% WMP and 5% SF are used simultaneously
Damage detection by updating structural models based on linear objective functions
No full textThe objective of this article is to detect the location and severity of structural damage according to direct model updating of physical properties by a Moore-Penrose inverse problem. The proposed method is based on expanding the dynamic orthogonality conditions in a damaged structure for attaining the difference between physical properties of undamaged and damaged structures. Hence, a two-stage damage detection process consisting of localization and quantification of damage is established by using linear objective functions which are applied in the expanded orthogonality conditions. Thus, an error matrix which is characterized as damage index is determined to identify the location of damage. Subsequently, damage extent is quantified by applying a linear objective function in the extended eigenproblem of the damaged structure. Eventually, two numerical examples are utilized to validate the proposed damage detection approach. In these examples, the modal data are considered to be incomplete and the inverses of rectangular matrices are accomplished by the Moore-Penrose technique while no multipliers are used. Furthermore, in all damage investigations, the predicted damage is compared with the preset values of induced damage. It can be concluded that the damage localization approach proposed in this study can precisely identify the location of damage through updating process. Moreover, the obtained results confirm this technique as being appropriate to predict the severity of damage. © 2014 Springer-Verlag Berlin Heidelberg
On model-based damage detection by an enhanced sensitivity function of modal flexibility and LSMR-Tikhonov method under incomplete noisy modal data
No full textSensitivity-based methods by the model updating strategy are still influential and reliable for structural damage detection. The major issue is to utilize a well-established sensitivity function that should be directly relevant to damage. Under noisy modal data, it is well known that the sensitivity-based model updating strategy is an ill-posed problem. The main aim of this article is to locate and quantify damage using incomplete noisy modal parameters by improving a sensitivity function of modal flexibility and proposing a new iterative regularization method for solving an ill-posed problem. The main contribution of the enhanced sensitivity formulation is to develop the derivative of eigenvalue and establish a more relevant sensitivity function to damage. The new regularization method is a combination of an iterative approach called least squares minimal residual and the well-known Tikhonov regularization technique. The key novel element of the proposed solution method is to choose an optimal regularization parameter during the iterative process rather than being required a prior. Numerical simulations are used to validate the accuracy and efficiency of the improved and proposed methods. Results demonstrate that the enhanced sensitivity function of the modal flexibility is more sensitive to damage in comparison with the basic formulation. Moreover, one can observe the robustness of the proposed solution method to solve the ill-posed problem for damage localization and quantification under noise-free and noisy modal data
INVESTIGATION OF THE EFFECT OF STEEL FIBERS ON FAILURE EXTENSION OF RECYCLED AGGREGATE CONCRETE BEAMS WITH LAP-SPLICED BARS
No full textIn this research, the effect of adding 0\% and 2\% volumetric percents of steel
fibers in beams containing three patches (43 cm, 34 cm, and 26 cm in length)
and recycled aggregate 0 and 100\% on the cracking and expansion path. The
cracks were examined under static loading. The purpose of this study is to
reduce the minimum crack width for adding steel fibers to reinforced concrete
beams made of recycled aggregates and tensile reinforcement patches. Hence,
twelve specimens of the beam were made at 150, 200, 1500 mm lengths with a
length of different tensile adherence rates and different percentages of steel
and recycled aggregates. The experiments were performed as a quadrilateral
bend. In experiments, the load-displacement curve in the middle of the span of
the specimens, the trajectory expansion along the beam and at the maximum
flexural anchor, the width of cracking, and the effect of adding steel fibers
on the compression and elongation of the specimens were indirectly
investigated. In addition, the results were compared with those presented in
the ACI, CSA, NS, CEB FIP, and EuroCode2 regulations. The results of the experiments showed that the addition of steel fibers reduced the slip of the
tensile reinforcement in the patched area and decreased the crack-cracking
width. Also, with addition of steel fibers in beams made of 2\% recycled
aggregate, the patch length can be reduced by 40\%
School Desk and Chair Design Based on High School Female Students Anthropometry Qazvin, Iran 2007 to 2008
No full textBackground and ObjectivesAnthropometry data compiled from body dimensions of female high school students are used to optimize the design of desks and chairs for the classrooms of these students. It is necessary to design suitable desk/chair based on anthropometry data in order to reduce musculoskeletal, visual, circulatory problems, and bad posture during long hours of studying.The goal of this study is to design desks/chairs based on the standard BS 5873 using the body dimensions of 240 female high school students.Methods240 female students, between the ages of 15 to 17 years old were selected from six different high schools in district 2 of city of Qazvin in Iran. Data for this study were gathered using an interview method and anthropometry measurement devices. Results Eighteen body dimension parameters of 240 female high school students were obtained. The collected data were analyzed and compared to the standard using SPSS methods. The participant students were divided into 2 groups and customized desk/chair designs were built to fit their body dimensions. ConclusionThere is a significant difference between each customized desk and chair dimension, and standard dimensions used in the industry with an exception of the heights of these designs. We suggest that customized designs based on body dimensions promote correct posture, comfort and health.Keywords: Human Ergonomics; Anthropometry; Equipment Design
