فهرست مطالب

Scientia Iranica - Volume:24 Issue: 3, 2017
  • Volume:24 Issue: 3, 2017
  • Transactions on Civil Engineering
  • تاریخ انتشار: 1396/03/28
  • تعداد عناوین: 14
  • Nawab Ali Lakho, Muhammad Auchar Zardari Page 1
    Clay is a low cost and environment friendly material of construction. On firing, it becomes hard and attains the compressive strength as high as normal concrete. This paper presents the flexural behaviour of singly reinforced baked clay beams under long term sustained loads. The loads applied at mid span of these beams were 30%, 40% and 50% of their short term failure load for a period of 360 days. The results show that the rate of deflection, formation of cracks and their stabilization was completed in a certain period of time depending upon the intensity of long term sustained loads. In the first and second loading conditions, this period of opening and stabilization of cracks was 100 and 77 days, respectively. Then the deflection increased with decreasing rate. While in case of 50% of loading condition, the period of formation and stabilization of cracks was reduced to only 50 days and then these cracks became dormant and no new crack was developed with respect to time. After that negligible mid span deflection was observed with respect to time. In addition to this, the deflection in these beams was more compared to the estimated long term deflection according to ACI code.
    Keywords: baked clay beams, sustained loads, ultimate loading capacity, deflection, cracks
  • Hamid Beiraghi, Ali Kheyroddin, Mohammad Ali Kafi Page 2
    In this paper, two distinct record scaling methods, spectrum-matching (SM) and amplitude scaling (AS) method, was used to study the seismic behavior of reinforced concrete core-wall buildings subjected to near-fault (NF) and far-fault (FF) strong ground motion. First, the core-walls were designed based on seismic codes. Next, nonlinear fiber element models of the core-walls were prepared using the extended plastic hinge approach and the single plastic hinge approach. The SM and AS methods were used to obtain appropriate records for use in nonlinear time history analysis. Amplitude scaling procedure led to larger curvature ductility demand at the upper levels of the buildings and this issue was more critical for the near-fault ground motions. While, SM procedure led to larger curvature ductility demand at the lower levels and less curvature ductility demand at the upper levels. The reason for this difference was the changes in the ground motion characteristics due to SM procedure. The changes in the ground motion characteristic were more severe for near-fault ground motions. For NF records, mean period of the SM records was 0.67 times that for the AS records and shows that the frequency content of the SM-NF events was affected by SMprocess.
    Keywords: Reinforced concrete, Core, wall, Near, fault, Far, fault, Record scaling
  • M. Mohammadi Page 3
    For in ll panels, the expected strength is very close to the cracking strength; however, experimental values of the cracking strength are very scattered, and there is no formula to estimate it accurately. That is why some new codes have been assumed to focus on determining the expected strengths of In ll panels by their maximum strengths. In this paper, an extensive statistical analysis is conducted on experimental data to achieve a formula for the maximum (mostly referred as ultimate) strength of solid masonry in lled frames. For the ultimate strength, reliability of the existing empirical relations (9 formulas) is investigated, based on the available experimental data, categorized in accordance with their con ning frames. The obtained results of 51 experimental specimens show that the formula, recommended by Maintone et al., is the best one; however, it mostly underestimates the ultimate strength and is more accurate for the in lls in concrete frames. The formula is also improved to have a better correlation with the experimental data.
    Keywords: Strength, Masonry, In ll panel, Seismic design, Ultimate strength, Equivalent strut
  • Saman Yaghmaei-Sabegh, Samaneh Karami, Mazdak Hosseini-Moghadam Page 4
    This paper presents a new searching framework for optimal scaling of earthquake ground motion records as inputs for dynamics analysis. Two hybrid coded genetic algorithm (GA) named real-permutation and binary-permutation GA has been effectively used to solve an applicable optimization problem in earthquake engineering. Methodologies are outlined to choose a set of ground motions- with a good level of fit to the design spectrum- and corresponding scales simultaneously during a hybrid coded process. The effects of different parameters used in design of algorithms have been investigated through the sensitively analysis to suggest a set of proper input values. Analysis showed that the sensitivity of the binary-permutation GA results to input parameters variations are less than real-permutation GA. The paper also concludes that binary-permutation GA is slightly more reliable thanreal-permutation GA, accordingly it is recommended as a suitable algorithm for selecting and scaling of spectrum-compatible ground motion records.
    Keywords: Ground motion scaling, time history analysis, design spectrum, genetic algorithm, hybrid coded genetic algorithm
  • Jose Orosa, Angel Costa, Gholamreza Roshan, Garc, Iacute, A. Bustelo Page 5
    Planet Global Heating was analysed in recent studies for Galician climate showing a rise in the average temperature in each season and a slight decrement in summer wind frequency. In consequence, the effect of the climate change can involve an error in wind turbine selection andits behaviour once it was put in. Furthermore, being the technical lifetime for a turbine twenty years onshore and twenty-five years offshore it is theright time to consider new development pathways such as lower moist air density and low speed wind turbines. In this paper twenty-four wind turbines were analysed in a typical year to get a model that relates weather to power conversion. Once done that, theeffect of the climate change was evaluated in Galician wind farms showing a 10% fall during spring and summer season. Therefore, future works about new technologies that workout well under those conditions like low wind turbines must be done.
    Keywords: Wind energy, climate change, moist air, power, wind farm
  • Seyyed Mehdi Kia, Mehdi Banazadeh Page 6
    The Probabilistic Seismic Hazard Analysis (PSHA), by considering uncertainties in the input parameters (e.g. magnitude, location, wave path way…), aims to compute annual rate of exceeding various ground motions at a site or a map of sites given all anticipated earthquakes. Uncertainties may be originated due to inherent randomness of the phenomena or variability in the mean values of different models parameters which is mainly due to use of finite-sample size of observations. The first, in literatures, is commonly named aleatory uncertainty but the second is known as epistemic uncertainty. The total probability numerical integration, generally employed to calculate PSHA, only considers aleatory uncertainties, and variability in the models parameters is neglected to simplify calculation. In this paper, as an alternate of the total probability numerical integration, matured and standard reliability methods tailor to effortlessly consider both type of uncertainties are put-forward to compute site-specific PSHA. Then, as an application study, thepeak ground acceleration hazard curve for the site at which a historical bridge is located is developed and compare with those obtained from total probability numerical integration.
    Keywords: Seismic hazard analysis, Reliability methods, Probabilistic model, Epistemic, aleatory uncertainties
  • M.A. Hadianfard, H. Marzouk, C. Shafieyan Page 7
    In this research, Non-Destructive Test (NDT) wave tomography techniques are used to estimate the strength and elastic moduli and to assess the health condition of the piers of an existing concrete bridge. There are various empirical relationships to evaluate concrete characteristics based on NDT techniques. However, it is not clear which empirical relationship matches the desired concrete better. Therefore, using only one empirical model can lead to inaccurate results. In the current investigation, the mean value of several appropriate relationships is considered as the desired value. Also, the use of only one NDT technique causes some errors. In order to accurately estimate the concrete characteristics, the combination of two or more nondestructive methods is very ecient. In this research, data of Ultrasonic Pulse Velocity (UPV) and shear wave velocity tests are used simultaneously. The results show that the combination of the two criteria of strength and elasticity and using an average value of several empirical models give a relatively accurate scale for assessment of the concrete condition. The results show the ability and eciency of the combination of two di erent NDT methods to estimate the strength, elastic moduli, and health condition of the concrete structure.
    Keywords: Ultrasonic pulse velocity, Shear wave velocity, Compressive strength, Dynamic modulus of elasticity, Nondestructive test, Mira, 3D
  • Ramtin Moeini Page 8
    In this paper, Arc Based Ant Colony Optimization Algorithm (ABACOA) is used to solve sewer network design optimization problem proposing two different formulations. In the both proposed formulations, named UABAC and CABAC,the cover depths of sewer network nodes are taken as decision variables of the problem. The constrained version of ABACOA (CABAC) is also proposed in the second formulation to optimally determine the cover depths of the sewer network nodes. The constrained version of ABACOA is proposed here to satisfy slope constraint explicitly leading to reduction of search space of the problem and compared to that by the unconstrained arc based ACOA (UABAC). The ABACOA has two significant advantages of efficient implementation of the exploration and exploitation features and also an easy and straightforward definition of the heuristic information for the ants over the alternative usual point based formulation. Two benchmark test examples are solved here using proposed formulations and the results are presented and compared with those obtained with alternative point based formulation and other existing methods. The results show the superiority of the proposed ABACOA formulation and especially the constrained version of it to optimally solve the sewer network design optimization.
    Keywords: Arc based Ant Colony Optimization Algorithm, sewer network, exploration exploitation, heuristic information, optimal design
  • Yaser Zafari, Mehdi Shahmohamadi, Ali Khojasteh, Mohammad Rahimian Page 9
    With the aid of Hankel transform and using a potential function, an analytical formulation is presented for the study of an exponentially graded transversely isotropic tri-material under applied axisymmetric point-load and patch-load. The given formulation is shown to be reducible to the special cases of inhomogeneous finite layer on the rigid base, exponentially graded bi-material or half-space under applied buried loads and homogeneous tri-material or bi-material solid. By means of a fast and accurate numerical method, several numerical solutions are given for the explanation of inhomogeneity effect on the stress transfer process in a inhomogeneous tri-material solid.
    Keywords: Functionally Graded Material, Exponentially Graded, Transversely Isotropic, Displacement Potential, Tri, material, Axisymmetric Green's Function
  • Hossein Tahghighi, Mehdi Rabiee Page 10
    Recent studies show that the effects of soil–structure interaction (SSI) may be detrimental to the seismic response of structure and neglecting SSI in analysis may lead to un-conservative design. The objective of this study is to simulate the performance of multi-story building-foundation systems through a Winkler-based approach. Four typical steel moment resisting frame (MRF) buildings on three soil types with shear wave velocities less than 600m/s subjected to actual ground motion records of varied hazard levels are modeled with and without SSI. It is observed that the performance level of models supported by flexible foundation, particularly in an intense earthquake event,may alter significantly in comparison to fixed-base structures.Moreover, for MRFs on soft soil, the nonlinear foundation is found to have a significant effect on the force and displacement demands. This is indicating the necessity for consideration of flexible foundation behavior in the modern design codes in order to accomplish a more economic yet safe structural design.
    Keywords: seismic response, soil–structure interaction, moment resisting frame, nonlinear analysis, design code
  • G. Ceribasi|E. Dogan, U. Akkaya, U.E. Kocamaz Page 11
    Various arti cial intelligence techniques are used in order to make prospective estimations with available data. The most common and applied method among these artifi cial intelligence techniques is Arti cial Neural Networks (ANN). On the other hand, another method which is used in order to make prospective estimations with available data is Trend Analysis. When the relation of these two methods is analyzed, Artfii cial Neural Networks method can present the prospective estimation numerically, while there is no such a case in Trend Analysis. Trend Analysis method presents result of prospective estimation as a decrease or increase in data. Therefore, it is quite important to make a comparison between these methods which brings about prospective estimation with the available data, because these two methods are used in most of these studies. In this study, annual average stream flow and suspended load measured in Sakarya River along withaverage annual rainfall trend were analyzed with trend analysis method. Daily, weekly, and monthly average stream ows and suspended loads measured in Sakarya River and average daily, weekly, and monthly rainfall data of Sakarya were all analyzed by ANN Model. Results of trend analysis method and ANN model were compared.
    Keywords: Trend analysis, Arti cial neural networks, Sakarya river, Rainfall, Stream ow, Suspended load
  • Isa Ebtehaj, Hossein Bonakdari, Fatemeh Khoshbin, Charles Hin Joo Bong, Aminuddin Ab. Ghani Page 12
    Sediment transport is a commonly occurring vital process in fluvial and coastal environments, and “incipient motion” is an issue inseparably bound to this topic. In this study, the existing equations were first examined by use of three different sources of experimental data through statistical indexes. The powerful method of Group Method of Data Handling (GMDH) was used for estimating the densimetric Froude number (Fr) and the Singular Value Decomposition (SVD) method was used to compute the leaner coefficient vectors. A novel equation is proposed, devolved through utilizing a combination of coding methods including GMDH and genetic algorithms. The studies conducted indicate that the presented equation is fairly accurate (RMSE= 0.19 & MAPE= 7%) in predicting incipient motion.
    Keywords: Group Method of Data Handling (GMDH), rigid rectangular channel, incipient motion, sediment transport, storm water
  • Alireza Badkoubeh, Ali Massumi Page 13
    A simple expression is proposed to estimate the fundamental period of vibration for concrete shear wall buildings. Most seismic codes specify empirical period formulas for seismic design. In this study, fundamental period data for concrete shear wall buildings recorded during California earthquakes between 1971 and 1994 were compared with current US code formulas. It is shown that these formulas are inadequate for estimation of the fundamental period of concrete shear wall buildings. A closed-form period solution based on Rayleigh''s method, using shear wall displacement as a parameter, is proposed to estimate the fundamental period of concrete shear wall buildings in low-, moderate-, and high-seismicity regions. The accuracy of the closed-form solution is verified using recorded periods and confirms that the proposed expression provides reasonable estimates of the lower bound of a period. The results show that the fundamental period of concrete shear wall buildings depends significantly on the displacement and mechanical properties of the shear walls.
    Keywords: Fundamental Period, Concrete Shear Wall Buildings, Code Periods, Closed, form Solution, Lower bound period
  • Davood Mostofinejad, Samad Noorpour, Mojtaba Noorpour, Reza Karbati Asl, Vahid Sadeghi Balkanlou, Ali Karbati Asl Page 14
    Abstract Petrochemical industries generate petrochemical wastes incinerator ash that its stream will end in landfill. This research was performed for waste management of ash and its possible large-scale utilization in making concrete. An experimental investigation carried out to evaluate the mechanical properties of concrete mixtures in which Portland cement type II was partially replaced with petrochemical complex incinerator ash powder (PCIAP). The cement was replaced with various amounts of PCIAP, i.e. 5%, 10%, 15%, 20%, and 25%. Tests were performed on the properties of fresh concrete as well as hardened concrete. Compressive, splitting tensile and flexural strengths, and modulus of elasticity were determined at 7, 28, and 90 days. Test results indicated that with using PCIAP as partial replacement of cement was carried out stabilization, solidification and neutralization treatment processes for the industrial wastes management and the test results of the mixture M-2 (5% PCIAP) indicated that it can be used in making concrete which is lighter than normal concrete and heavier than structural lightweight aggregate concrete.
    Keywords: Concrete, incinerator ash, compressive strength, splitting, tensile strength, flexural strengths, elastic modulus