Civil Engineering Infrastructures Journal
Volume:44 Issue: 1, 2010

Leakage in water distribution networks causes waste of water and economical losses. In this paper a new method is presented to calculate nodal and pipes leakage in water distribution systems using capabilities of EPANET2.10 software. The method estimate the total water losses in the system based on IWA methodology using Minimum Night Flow (MNF) measurements. Recognising the pressure dependency of leakage the total water consumption is divided into two parts, one pressure dependent and the other independent of local pressure. The total leakage is then distributed in different nodes based on nodal pressures and then leakage at each pipe is calculated. Furthermore, the effects of leakage management are evaluated and leakage indices are determined. Based on the outputs of a case study in Ilam Province, the capabilities of the proposed methodology is evaluated. The results show that by combining the new method and hydraulic models the system can be simulated and nodal and pipe leakage are obtained using hydraulic parameters. It can also be observed that leakage performance indices have a great role in leakage management, prioritisation of loss reduction scenarios and budget consumption in water companies. Besides, these indices show the degree of success for leak reduction schemes. Finally, it was found that the infrastructure leakage index (ILI) is the most effective factor on the leakage and the best one to evaluate the leakage performance.

A linear elastic transversely isotropic full-space containing three different regions, which are an upper half-space, a lower half-space and a layer in between is considered in such a way, each region contains different material. The axes of symmetry of different regions are assumed to be normal to the interface of the regions and thus parallel. An arbitrary load in frequency domain is applied on an arbitrary patch located at the interface of the upper half-space and its underneath layer. Integral formulations are presented for the determination of the displacements and stresses in all regions. By means of the complete displacement potentials introduced by Eskandari-Ghadi (2005), Fourier series in circumferential direction and Hankel transform in radial direction, the displacements and stresses are determined in Fourier-Hankel space. Then, the displacements and stresses at any point are given in the line integral form. The solution is numerically evaluated for: (i) a half-space under an arbitrary surface load, (ii) a half-space under an arbitrary buried force, (iii) a half-space fixed at the top and under an arbitrary buried force, (iv) a half-space containing a layer bonded to the top of a half-space under an arbitrary force applied at the interface of two regions, (v) a full-space under an arbitrary load in it, (vi) a bi-material full-space under an arbitrary force applied at the interface of two half-space, and (vii) a layer of finite thickness fixed at the bottom and under an arbitrary surface load. To confirm the accuracy of the numerical evaluation of the integrals involved, some of the results are compared with existing solutions.

Hysteretic dampers as the most practical passive control methods have improved the seismic performance of steel structures through energy dissipation induced by large inelastic deformations. Among them in this paper, KBF (Knee Braced Frames), a special form of braced frames having a diagonal brace connected to a knee element instead of beam-column joint, is investigated. In such systems, the knee element designed to have inelastic behavior for dissipating seismic energy caused by strong earthquake. In this article, analytical investigation on cyclic performance of knee braced single span one-story frame specimens are described. Nonlinear finite element method have been used for analysis of KBFs. Results have shown good behavior of knee member before its failure and also indicated a number of important considerations for seismic design of KBFs. Moreover hysteretic behavior have shown no pinching effects. At last, a mathematical model has been derived to predict the bilinear behavior of the KBFs and compared with monotonic pushover analysis. Acceptable conformity between mathematical and numerical model proved the accuracy of the proposed model.

Creep compliance is one of the fundamental tests of Mechanistic- Empirical flexible pavement design procedure in the AASHTO 2002 design guide. In this research, a new Artificial Neural Network model for estimating the HMA creep compliance with the generalization ability of R=0.949 has been developed successfully using feed forward multi layer perceptron Artificial Neural Networks (ANNs) with Levenberg-Marquardt backpropagation training algorithm. The ANN model has 14 inputs including selected percent passings from aggregate gradation curve, asphalt content, asphalt penetration degrees at 77 and 125 Fahrenheit, asphalt penetration index and test temperature. The model has 8 outputs consist of creep compliances of Hot Mix Asphalt at 1, 2, 5, 10, 20, 50, 100 seconds and Poisson coefficient. All needed data has been extracted from LTPP database 2007 by developing many programs by SQL in Access 2000. As the result, 975 creep compliance tests data and 975 associated aggregate tests data series and 975 associated asphalt tests data series has been extracted successfully for ANNs training and evaluation.

Due to the development of urban areas, underground structures are increasingly needed. Therefore, not only it is likely to have two tunnels located close to each other, but also it happens frequently.Because of the complexity of realistic problems, closed form analytical solutions are not accessible for them. However, latest advances in computational techniques have made numerical approaches more practical for realistic problems. Boundary element method (BEM) is one of such approaches. This technique formulates the problem in terms of boundary values. The main advantage of BEM, especially in comparison with finite element and finite difference methods, is that the discretization is only applied to the boundary, thus reducing the volume of modeling and the number of unknown variables. Moreover, the radiation condition at infinity is exactly satisfied in this method which is very striking for wave propagation problems. First the formulation of boundary element method in the time domain is presented and then a parametric study on the dynamic response of unlined circular tunnels subjected to internal explosion is done. Depth of tunnels, vertical and horizontal distance between two tunnels, diameter of tunnels, and other parameters related to geometry are important factors which can affect displacements and stresses of tunnels under explosive loading. In the present study, effect of two parameters has been investigated: changing the depth of the tunnel that is subjected to internal explosion (case A) and changing the horizontal distance between two shallow tunnels subjected to explosion (case B). Radial displacements and circumferential stresses are the results obtained. Case A- Tunnel depth: The tunnel behavior in depth of H=50R is alike to behavior of same tunnel in infinite depth. Also, radial displacement in upper point of tunnel in depth of H=2R is about 2.7 times of the same tunnel in infinite depth. Circumferential stress in points placed on horizontal diameter of tunnel in depth of H=2R is about 1.8 times of the same tunnel in infinite depth. Case B- Tunnels distance: Two tunnels with horizontal distance of greater than L=50R don’t affect each other. When horizontal distance parameter of two tunnels is L=2.5R then the maximum normalized displacement of the side point of the loaded tunnel, is approximately 2.15 times of the same tunnels with distance of infinite. Also, when horizontal distance of two tunnels is L=2.5R, circumferential stress in lower point of the loaded tunnel, which is normalized with static stress, is approximately 1.2 times of the same tunnels with distance of infinite. Normalized results calculated here display the importance of the geometric parameters on the behavior of unlined tunnels subjected to internal explosion and provide suitable criteria for displacement design of shallow tunnels that are subjected to internal explosion. The accuracy of the present study for the computation of radial displacements and circumferential stresses is verified by solving several problems.

As a result of wide spread application of marine structures, especially in oil and gas industries, their safe design is of paramount importance. In this regard, explosion loading, which may result from accidents or military/ terrorist actions, should be considered, although they may not always be included in the final structural design. The impulsive nature of explosive loading, which comprises a high peak pressure followed by a relative fast decay, and complex phenomena of reflection of incident waves on flexible curved surfaces of a structure, leads to highly complicated analysis of underwater explosion. Detonation of a high explosive material under water produces two pressure pulses: a shock wave which has a very short duration (about several ten to several hundred micro seconds) and a bubble pulse associated with the expansion of the products of detonation. Roles of the underwater shock wave, flow and bubble in the damage process of structures are not as yet, clear. Only effects of the primary shock wave generated from an explosion on circular and rectangular plate specimens and empty submerged cylinders are studied in this research. Effects of bed and water surfaces are not taken into account. The structure and its surrounding water are modeled by solid finite elements. They are attached to each other to enforce for coupling analysis. The water is bounded by nonreflecting boundaries to avoid unwanted reflections from the finite boundaries of the domain. Results of the numerical simulations are compared to the experimental data and the results obtained from available empirical relations.

In this paper, river regime equations through developing of unit stream power equation and based on data of Sistan and Karaj Rivers were derived. At the first step, methods and out-comes of former researchers are classified. On the next step, based on dimensional analysis, unit stream power as a function of river flow parameters including suspended sediment load and specific gravity of particles is developed. Using the unit stream power equation and Sistan and Karaj River's data, regime equations are derived for these rivers. Finally, the results derived from regime equations are compared with the field data and regime equations of the other researchers. A good agreement was observed between field data and values resulted from developed regime equations in this research.

This paper deals with three-dimensional evaluation of the slopes on the basis of limit analysis. An upper-bound technique of limit analysis is used in this paper to determine either the bearing capacity of a shallow foundation near a slope or the safety factor of the slope. The theorems of limit analysis (upper and lower bound) provide a powerful tool for solving problems in which limit loads need to be found. According to the upper-bound theorem, for a kinematically admissible velocity field an upper bound of the collapse load can be obtained by equating the power dissipated internally in an increment of displacement to the power expended by the external loads. Such kinematically admissible velocity fields have to comply with the kinematical boundary conditions and compatibility conditions. A rotational mechanism consisting of three slip surfaces is used to determine the factor of safety for a slope or the ultimate limit load of a foundation with eccentric load near a slope. This mechanism includes two lateral surfaces and a surface at bottom. As the soil is assumed to obey the associated flow rule, the angle between the relative velocity vector and velocity discontinuity has to be equal everywhere with soil's friction angle (?). The geometries of lateral surfaces are represented by a nonlinear differential equation. A surface with log-spiral section is used for bottom surface of the mechanism. To obtain the minimum upper-bound, an algorithm is proposed to optimize the failure mechanism. Results from this algorithm for typical conditions are comparable to those of other existing methods. Dimensionless diagrams for various conditions are presented which can be used to predict the bearing capacity of a foundation with eccentric load located on a slope.

Different innovative controlling systems have been introduced into the literature in the last two decades varying from passive to active and smart control systems. Shape memory alloys (SMAs) are one of these systems with unique properties and behaviors which have made them and appealing material for use in dampers. SMAs exist in two crystallographic phases: the parent austenite phase and the product martensite phase. SMA materials are favorable for use in seismic applications, because of their recentering capability in austenite phase, high damping capacity in martensite phase and very high fatigue and corrosion resistance in both phases.I this paper, it is shown by analytical measures and by using proper constitutive relations for SMA materials that an ideal behavior can be obtained for a proposed Special SMA damper when using proper proportions of SMAs in austenite and martensite phases. The damper is devised so that produces maximum obtainable damping capacity while maintaining its recentering capability. By performing nonlinear dynamic time history analyses for selected structures enforced with buckling restrained steel braces and special SMA dampers, the permanent residual deformations remained on the structures after earthquakes are compared. The results show the effectiveness of implementation of SMA dampers while the main advantage is shown to be the drastic mitigation of the permanent deformations remained on the structure when using the proposed SMA dampers.

The direct way to access the petrophysical property of hydrocarbon reservoir is based on well data but due to its high cost, the seismic data has been used to obtain these parameters. For this purpose, many different methods are available and each has its own advantages and limitations. From these methods the seismic inversion is the best tool to study the reservoir characterization. The outcome of the seismic inversion is the transformation of seismic reflection data to pseudo-impedance logs at each CMP. It is therefore, the seismic inversion results facilitate better estimations of reservoir properties such as porosity. In this study the results of two different post-stack inversion methods on seismic data will compared. These are sparse-spike and model-based methods. These results were used for acoustic impedance construction based on 2D seismic data in the Saraje Gas Field. By using this model and creation of linear regression the estimated porosity model has been achieved.

During an earthquake, many stations record the ground motion, but only a few numbers of them could be corrected using conventional high-pass and low-pass filtering method and the others identified as highly contaminated by noise and as a result useless. There are two major problems associated to these noisy records. First, since signal to noise ratio (S/N) is low, it is not possible to discriminate between original signal and noise neither in frequency domain nor in time domain. The consequence is that it is not possible to cancel out the noise using conventional filtering methods. The second problem is about non-stationary characteristics of the noise. In other words, in many cases the characteristics of the noise are varying by time and in these situations, it is not possible to apply frequency domain correction schemes. For correction of acceleration signals contaminated with high-level non-stationary noise, there is an important question that is it possible to have estimation about the state of the noise in different bands of time and frequency? The wavelet multi-resolution analysis which decomposes a signal into different time-frequency components besides a suitable criterion for identification of the noise among each component provides the required mathematical tool for correction of highly noisy acceleration records. In this paper, the strong motion records of great earthquake events with Mw>5.5 in Iranian Plateau is corrected. For this purpose, first, signal to noise ratio is calculated for each record. If the value of this diagram is high enough, the signal is corrected with both methods and otherwise, the de-noising is applied using wavelet procedure. The effect of baseline correction of the final results is also investigated for each record. A comprehensive database containing the information of events, stations and correction parameters is also provided in this study.

The ambient vibration measurement is a kind of output data-only dynamic testing where the traffics and winds are used as agents responsible for natural or environmental excitation. Therefore an experimental modal analysis procedure for ambient vibration testing needs to base itself on output-only data. The modal analysis involving output-only measurements present a challenge that requires the use of special modal identification technique, which can deal with very small magnitude of ambient vibration contaminated by noise. Two complementary modal analysis methods are implemented. They are rather simple peak picking (PP) method in frequency domain and more advanced stochastic subspace identification (SSI) method in time domain. According to these methods Graphical User Interface (GUI) software developed in MATLAB. This program is called SIP and can be used in modal parameter identification of large civil structures such as bridges and towers. This paper presents the application of ambient vibration testing and experimental modal analysis on large civil engineering structures and also gives brief review of program. Also modal parameters of the Babolsar arch steel bridge are extracted using SIP and ambient vibration data from dynamic test carried out on this bridge.