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Showing 12 results for Energy

Bakhtiari Nejad F., Rahai A., Esfandiari A.,
Volume 2, Issue 2 (6-2004)
Abstract

In this paper a structural damage detection algorithm using static test data is presented. Damage is considered as a reduction in the structural stiffness (Axial and/or Flexural) parameters. Change in the static displacement of a structure is characterized as a set of non-linear undetermined simultaneous equations that relates the changes in static response of the structure to the location and severity of damage. An optimality criterion is introduced to solve these equations by minimizing the difference between the load vector of damaged and undamaged structures. The overall formulation leads to a non-linear optimization problem with non-linear equality and linear inequality constraints. A method based on stored strain energy in elements is presented to select the loading location. Measurement locations are selected based on Fisher Information Matrix. Numerical and experimental results of a 2D frame represent good ability of this method in detecting damages in a given structure with presence of noise in measurements.
H. Oucief, M.f. Habita, B. Redjel,
Volume 4, Issue 2 (6-2006)
Abstract

In most cases, fiber reinforced self-compacting concrete (FRSCC) contains only one type of fiber. The use of two or more types of fibers in a suitable combination may potentially not only improve the overal properties of self-compacting concrete, but may also result in performance synergie. The combining of fibers, often called hybridization, is investigated in this paper for a cimentetious matrix. Control, single, two fibers hybrid composites were cast using different fiber type steel and polypropylene with different sizes. Flexural toughness tests were performed and results were extensively analysed to identify synergy, if any, associated with various fiber combinations. Based on various analysis schemes, the paper identifies fiber combinations that demonstrate maximum synergy in terms of flexural toughness.
M. Khanzadi, G. Ghodrati Amiri, G. Abdollahzadeh Darzi,
Volume 5, Issue 1 (3-2007)
Abstract

According to performance-based seismic design method by using energy concept, in this paper it is tried to investigate the duration and damping effects on elastic input energy due to strong ground motions. Based on reliable Iranian earthquake records in four types of soils, structures were analyzed and equivalent velocity spectra were computed by using input energy. These spectra were normalized with respect to PGA and were drawn for different durations, damping ratios and soil types and then effects of these parameters were investigated on these spectra. Finally it was concluded that in average for different soil types when the duration of ground motions increases, the input energy to structure increases too. Also it was observed that input energy to structures in soft soils is larger than that for stiff soils and with increasing the stiffness of the earthquake record soil type, the input energy decreases. But damping effect on input energy is not very considerable and input energy to structure with damping ratio about 5% has the minimum value.
Mahmoud Hassanlourad, Hosein Salehzadeh, Habib Shahnazari,
Volume 6, Issue 2 (6-2008)
Abstract

In this paper shear behavior of two calcareous sands having different physical properties are

investigated using drained and undrained triaxial tests. The investigated sands are obtained from two different

zones located in Persian Gulf, Kish Island and Tonbak region. Analysis based on energy aspects show that

friction angle in these soils, having crushable particles, is formed of three components: substantial internal

friction angle, dilation and particle breakage angle. Dilation component is available in the two investigated

sand. Particle breakage component is a function of grains hardness, structure and geometry shape. Particles

breakage decreases the volume of sample during drained tests and creates positive pore water pressure during

undrained tests. Two investigated sands show different amount of dilation and particle breakage under similar

conditions. Simultaneous dilation and particles crushing and different amount of them result in different shear

behavior of the two studied sands. Energy aspects are used to determine the effect of particle crushing on the

shear strength. There is a suitable compatibility between relative breakage of grains and consumed energy

ratio for particle breakage.


Mohammad Reza Kavian Pour, H.r. Masoumi ,
Volume 6, Issue 3 (9-2008)
Abstract

Hydraulics of stepped spillway is a very complicated phenomenon, as it consists of a two phase flow passing through a set of designed steps. The steps increase the rate of energy dissipation taking place on the spillway face. Turbulence, flow aeration and energy dissipation are the main tasks in the design of such structures. This study consists of the experimental investigation to determine the energy dissipation over stepped spillways. Experiments conducted at Water Research Institute on two physical models of the Siyah Bisheh stepped spillways in Iran. To develop a more generalized expression, the results of previous investigations were also considered in our study. Therefore, a wide range of variables were taken into account to estimate the energy dissipation along the non-uniform flow regime. Assuming the energy dissipation along the uniform flow regime to be equal to the vertical displacement of the jet, the total energy lost was calculated. A comparison of the results with those of measurements showed a regression of 0.92 for the total energy dissipation, which is one of the features of the present method for estimating of the energy dissipation, compared with the previous investigation.
A.r. Rahai, M.m. Alinia, S.m.f Salehi,
Volume 7, Issue 1 (3-2009)
Abstract

Concentric bracing is one of the most common lateral load resistant systems in building frames, and are

applied to many structures due to their manufacturing simplicity and economics. An important deficiency in the

bracing members is their irregular hysteretic loops under cyclic loading. In order to overcome this problem, it is

advised to restrain braces against buckling under compression, since buckling restrained frames dissipate a large

amount of energy. One method to restrain braces against buckling is to cover them with concrete. A proper covering

can prevent the core from buckling and provide similar capacities whether in tension or compression which would

produce regular hysteric curves. In this study, the behavior of buckling restrained braces (BRB) has been investigated

by considering different types of surrounding covers. The steel core is encased in concrete with different coverings. The

covering types include steel tubes, PVC pipes, and FRP rolled sheets. Experimental and numerical analyses were

implemented. According to the results, PVC pipes and FRP sheets are suitable alternatives to steel pipes. Furthermore,

the behavior of several types of steel cores was assessed since, applying steel with high ductility promotes the energy

dissipation of the brace. Finally, the effect of the separating layer between the steel core and the concrete on the

performance of bracing was evaluated.


M.h. Sebt, A. Yousefzadeh, M. Tehranizadeh,
Volume 9, Issue 1 (3-2011)
Abstract

In this paper, the optimal location and characteristics of TADAS dampers in moment resisting steel structures, considering the application of minimum number of TADAS dampers in a building as an objective function and the restriction for destruction of main members is studied. Genetic algorithm in first generation randomly produces different chromosomes representing unique TADAS dampers distributions in structure and the structure corresponding to each chromosome is time history analyzed. Then the damage index for each member and the average weighted damage index for all members are determined. Genetic algorithm evaluates the fitness of each chromosome then selection and crossover as logical operators and mutation as random operator effect the current generationchr('39')s chromosomes according to their fitness and new chromosomes are generated. Accordingly, successive generations are reproduced in the same way until the convergence condition is fulfilled in final generation and four distributions are suggested as better options. Since these proposed distributions are selected under the one earthquake, therefore, it is better that the four new structures are cost-benefit analyzed in different earthquakes. Finally, the optimal placement for dampers is compared and selected based on a benefit to cost ratio, drift stories and the number of different TADAS types of such structures. The increase in amount of energy dissipated via dampers located in different floors as well as the status of plastic hinges in main members of the structure strengthened with optimum option are the proof of the optimal placement and suitable characteristics for dampers.


F. Tootoonchy, B. Asgarian, F. Danesh,
Volume 13, Issue 2 (6-2015)
Abstract

Despite the rapid growth of engineering science especially in the modern structural engineering and application of new materials in civil engineering, a significant percentage of world population in different countries are living in adobe buildings made from mud-bricks. In this paper, by performing experimental study on scaled mud-brick walls under monotonic load, in-plane behavior of the walls have been investigated for different levels of vertical load. After recognizing damage mechanisms from experiment, a simple retrofitting method has been presented to upgrade wall performance. Experimental behavior of retrofitted walls was also studied. The proposed retrofitting method consists of using polypropylene lace and tarpaulin belts. As a result, a better performance of the walls in terms of shear capacity, ductility and energy absorption are observed by using proposed retrofitting method. Meanwhile, Proposed retrofitting method has significant effect in rocking mechanism delay and prevention of wall sudden collapse.
S. Pagliara, T. Roshni, M. Palermo,
Volume 13, Issue 3 (9-2015)
Abstract

Rock chutes are natural river training structures and are efficient energy dissipaters too. From the hydraulic and environmental point of view, rock chutes have become important structures in the natural river morphology. A physical study was conducted and flow properties were measured over rough bed materials of a rock chute, which was assembled at the PITLAB center of the University of Pisa, Italy. Experiments were performed for slopes varying between 0.18≤ S ≤0.38, 0.03 < dc/H < 0.54 and for ramp lengths Lr between 1.17 m ≤Lr≤3.6 m. This paper presents the energy dissipation characteristics of the two-phase flows in the presence of two different base materials. In addition, the dissipative process was also analyzed in the presence of reinforcing boulders located on the base material. The findings showed that energy dissipation rate slightly increases with the boulder concentrations for the tested slopes and materials. The experiments were conducted for different rock chute lengths in order to understand its effect on the energy dissipation. An empirical expression is developed for determining the energy dissipation characteristics over different base materials in different ramp length conditions in twophase flows. Results have been compared with the results obtained for stepped chutes and found a similar decreasing trend of dissipation rate for dc/Lr ≤0.1.
V.v. Sakhare, S.p. Raut, S.a. Mandavgane, R.v. Ralegaonkar,
Volume 13, Issue 4 (12-2015)
Abstract

Energy conservation in buildings plays a vital role for sustainable development of societies and nations. Although, newer buildings in developing nations are being constructed using energy conservation approach, existing buildings have higher energy demand to meet the desired comfort. Excessive energy demand for cooling the built environment is a major problem over most of the arid climatic zones. The problem is predominant in all the top storied buildings which are directly under exposed roof condition. In order to reduce the overheating of the roof surface a composite combination of reflecting-cum-insulating (R-I) material was developed. The sustainable materials viz., expanded polystyrene (construction waste), saw dust (industrial waste), and the false ceiling panels prepared from industrial waste were used for the development of sustainable R-I material. The R-I material was retrofitted over the existing roof of a model room in an educational building over composite climate (Nagpur, India) and was analyzed experimentally for the period of a year. The thermal resistance of the overall roof assembly was increased from 0.28 to 0.55 m² K/W, which in turn helped to achieve 16% of the duration of the year under thermal comfort. The developed R-I material has also an advantage of low cost (INR 900 per sq. m.) of installation as well as light weight (50 kg/m²) retrofitting solution. The R-I product can further be applied on larger roof areas by the designers to reduce the cooling load of the built environment as well as increase the occupants comfort over the local climatic zone.


Hasan Dilbas, Özgür Çakır, Mesut Şimşek,
Volume 15, Issue 2 (3-2017)
Abstract

The determination of the parameters of concrete (i.e., elasticity modulus, tensile strength) is very crucial task in material engineering. For this purpose, in general, structural codes propose some empirical formulas to estimate the parameters of materials and is useful for designers rather than the experimental process. However, the estimated results usually vary for different standards. Hence, this research paper aims to compare the elasticity modulus formulas considering six standards (TS 500, ACI 318M-05, CSA A23.3-04, SP 52-101-2003, EN 1992-1-1 and AS-3600-2001) with experimental elasticity modulus test results. In the evaluation of the results, the TS 500 and EN-1992-1-1 overestimate the elasticity modulus and the SP-52-101-2003 estimates the values more close to experimental results. In addition, a new equation for modulus of elasticity including the compressive strength and the density is derived for RAC. Also, in this paper energy capacities of concretes (elastic energy capacity, plastic energy capacity and toughness) are evaluated considering compressive strength test data. As a result, according to energy capacities of concretes, the proportions 5% silica fume (SF) and 30% recycled aggregate are proposed as the optimum ratio.


Laemthong Laokhongthavorn, Chalida U-Tapao,
Volume 15, Issue 2 (3-2017)
Abstract

This paper has applied operation research to solid waste disposal by which two objective functions are optimized to minimize the expected operational costs (maximize revenues) and the expected net carbon dioxide equivalent (CDE) emissions. Types and uncertain amounts of solid wastes as well as costs of electricity were factored into the selection decision of solid waste disposal, i.e. landfill, incineration, composting and recycling. An optimization model was applied to the solid waste disposal of Bangkok, Thailand. In addition, a multi-objective optimization technique was proposed for a tradeoff decision-making between minimum operational costs and CDE emissions. Composting and landfill are effective alternatives for Bangkok’s solid waste disposal system. The operational costs and net CDE emissions are highly correlated with the quantity of solid waste. Policy-makers and plant operators could adopt the proposed optimization model under uncertainty in the selection of an optimal solid waste disposal.



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