نشریه مهندسی عمران و محیط زیست دانشگاه تبریز
سال چهل و یکم شماره 1 (پیاپی 64، تابستان 1390)

The diffraction of seismic waves by topographic irregularities can dramatically amplify free field ground motion. This phenomenon was experienced and observed in figure of local damage concentration, landslides and rock failures during different past earthquakes. It is common for topographic effects such as canyons to be analyzed using 2-D models that assume the canyons to be prismatic (i.e., have uniform cross sections). The present paper investigates the effect of a non-prismatic 3-D canyon on the diffraction of seismic waves. The analysis uses 3-D boundary element method. A comparison of results for prismatic and non-prismatic canyons shows that the non-prismatic canyon can increase or decrease the amplification and the variation of ground motion across the canyon. The significance of these effects depends on the pattern of cross-section variation along the canyon length, as well as the incident wave direction and frequency. For the most common cases in practice (the non-prismatic canyon widening toward the ends) this effect amplifies the topographic amplification strongly. Thus it is concluded that for non-prismatic canyons a 3-D solution is essential in order to get an accurate perspective of the phenomena of topography.

Selfcompacting concrete (SCC) is a type of concrete with high plasticity and strength against segregation. It does not need vibration because it is able to flow under its own weight, completely filling the formwork and achieving full compaction. In this paper, efforts have been made to present a certain design mixture for making SCC including microsilis, and also to improve its physical and mechanical properties against fire by adding polypropylene fibers (PPF) and magnesia. The effect of two different amounts of PPF and four different amountsof magnesia on compressive strength, tensile strength and modulus of elasticity at the ages of 7, 11, 28, 42 and 90 days is studied. 15 primary design mixtures with variation in aggregates, filler and super plasticizer have been made, and experimental tests consisting of slump, J loop, U box, L box and V hooper have been conducted. A suitable design mixture has been chosen on the basis of compressive strength for further laboratory tests. 150 cubic and 34 cylindrical samples have been prepared and tested for evaluating compressive strength, tensile strength and modulus of elasticity. Results indicate that polypropylene fibers can increase tensile strength and fire resistance, and magnesia with 100 μm segregation can increase compressive strength of SCC.

In this paper a new friction damper, which can be installed in X-shape bracing, is introduced. This device is in the group of displacement-dependent devices and consists of several steel plate and friction pads. These frictional pads are bonded between steel plates at the predefined special regions. In order to apply normal clamping force on the device, 9 high strength bolts are used. The applied clamping force can be adjusted by tightening of these bolts. In order to keep the clamping forces constant, several spring disc washers are used.This damper was manufactured at Earthquake Engineering Laboratory of Urmia University and installed inside a model SDOF steel frame. The frame was put over the shaking table and its responses under several earthquake excitations were recorded. For checking the effectiveness of the device in mitigation of the responses of a four storey frame, several nonlinear time history analyses were conducted. The results of the experimental tests and the analytical calculations show that this modified friction damper not only provides an added structural stiffness, but also has good seismic energy dissipation capability.

Shape memory alloys (SMAs) are novel materials that found more applications in many fields of science and engineering. Recently, SMAs have been used in structural engineering due to their re-centering, high damping capacity, durability and fatigue resistance. Aforementioned characteristics of SMAs rely on two unique properties: Shape Memory Effect (SME) and super elasticity. One of the applications of this material in structural engineering is to use SMAs as bracing elements. The results of investigations that carried out on SMAbraced frames represent the functionality and viable performance of this bracing system. In this paper, SMA wire braces were installed diagonally in the frame structures as seismic resisting members. Several SMA-braced frame models were designed to investigate the behavior factor (R) of these types of frames. The behavior factor and its components including ductility reduction factor and over strength factor were evaluated by performing pushover analysis of the models.

Genetic programming (GP) is an application of genetic algorithm for upgrading previously coded programs to solve problem. The main strategy of search in GP is based on genetic algorithm. Genetic programming is different in basic concepts from genetic algorithm. The difference is that genetic programming acts especially on the parse tree while genetic algorithm acts in another way, it means bit strings. These two definitions are basically different in solution methods. One of the basic applications of genetic programming is symbolic regression that is known as a route for automotive simulation. One of the main disadvantages of genetic programming is excessive growth of program without any useful effect on program itself. This phenomenon is called bloating. There are different methods for controlling of excessive growth in genetic programming. In this research the different techniques for control of bloating in symbolic regression problems were compared.Rainfall-Runoff modeling is one of the most important issues in symbolic regression of water resource ngineering, and this investigation could be effective for results improvement in Rainfall-Runoff.

Accurate estimation of the sediment outflow is one of the most important factors in water development projects. Estimation of sediment yield is required in a wide spectrum of problems such as: design of reservoirs and dams, transport and deposition of sediment in channel networks and water pollution. It is difficult to appoint governing equations of suspended sediment because of different parameters effects, and comparative mathematical models usually dont have enough accuracy. In this study, chaos theory was applied to model suspended sediment of Lighvan river watershed. The application of chaos theory in hydrology has been gaining considerable interest in recent times. An attempt is made in this study to characterize and predict daily suspended sediment load series using ideas gained from chaos theory during 30 years from the Lighvan River. To reconstruct phase space, the delay time and embedding dimension are needed and for this purpose,autocorrelation function and algorithm of false nearest neighbors are used. Correlation dimension method is applied for probe chaotic behavior of daily sediment load and obtained low correlation dimension chaos express chaotic behavior in the time series under investigation. Local prediction algorithm is used for prediction time series that results illustrate good and acceptable accuracy of chaos theory to predict daily suspended sediment load.

The uses of traditional concretes always require vibration in construction of structures with high percentageof reinforcement has been faced with problem. Nowadays, the modern technology offers self-compacting concrete construction with high flow ability.
To reduce the progress of hair cracks in concrete, the
use of fibers in concrete mixtures is recommended.
Also, according to the complexity operation of concrete against elevated temperature, the behavior of concrete under elevated temperature especially fiber reinforcement concrete will be necessary. In this study, the experimental study on self-compacting concrete and self-compacting concrete containing nylon fiber have been carried out based on compressive strength, splitting tensile strength, elastic modulus and shrinkage. Also, for predicting the behavior of concrete against elevated temperature, between 200 to 900 °C, compressive strength, splitting tensile strength and flexural behavior of reinforced concrete beams,
for both self-compacting concretes have been investigated. The specimens were kept in the wet and dry conditions and they were tested in ages from 7 to 90 days. The results showed that an optimum nylon fiber content of 0.4 Kg/m3 based on the fresh properties of concrete and EFNARC limitation can improve the mechanical properties of self-compacting concrete.
In the case of heated samples, a reduction on compressive and tensile strengths of two mentioned self compacted concretes was resulted from 400 °C. At temperatures above 600 °C, the strength of self-compacting concrete with nylon fiber was lower than ordinary self-compacting oncrete.Also, the increased temperature will accelerate the yielding of steel and rupture process in self-compactingconcrete with nylon fiber in compared to ordinary self-compacting concrete.

In concrete construction, self-weight represents a very large proportion of the total load on the structure.Lightweight concrete (LWC) have many advantage such as less dead load consequently smaller cross section and better durability was needed. Confinement of concrete is effective in increasing its strength and deformation capacity with compare to the unconfined concrete. An efficiency of CFRP on behavior of confined lightweight concrete element is one of the areas that needed to research. In this paper, the behavior of confined and unconfined lightweight concrete specimens under uniaxial loading was studied. 48 specimens with dimension of 150×150×300mm cubic specimens were used. For confinement of specimens two type of CFRP, fully wrap and strap, were used. In order to prevent the fiber from folding and also to decrease the concentration of stress, the section corners were chamfered to a radius of 5 to 25mm. The axial & lateral strain of specimens was compared.The result has shown with increasing of corner's radius, not only the ultimate strength and strain, but also the stiffness of confinement specimens, are increasing. At the end the paper, formulation of confined lightweight concrete which depends on concrete compressive strength, number and thickness of CFRP layers, dimension of cross section, corner radius and type of confinement (fully or strap) was given.

Response modification factor is one of the important parameters in calculating the effective loads on structures, during the severe earthquakes. This factor includes particular complexity and depends on many cases.The aim of this paper is to present useful information about response modification factors from primarily step that mea ns definition up to determine for different type of structures. For this purpose, different aspects of response modification factor have been identified and sort based on the simple to complex topics. Issues that are mentioned in this article include: definition of the response modification factor, response modification factor’s history, application of response modification factor, factors affecting on response modification factor, response modification factor’s calculating methods and the calculated values of response modification factor for concentrically braced steel frames and reinforced concrete moment frames. The presented information will help engineers have better understanding how to use this factors in the structural design and scrutinize the structures response modification factor values.

Considering the health effects of exposure to heavy metals and also huge number of SCIs in Iran and alsoabsence of published data about heavy metals presence in solid wastes of Stone Cutting Industries (SCIs), at present study presence of heavy metals in the effluent and sludge of Tabriz SCIs was studied. For determination of heavy metal (Cr, Cd, Pb and Cu) presence in effluent and sludge of SCIs, samples of effluent containing suspended solids, was gathered from effluent of cutting stage of 5 factories and were analyzed by Atomic Absorption Spectroscopy (AAS) for determination of heavy metal concentration. In the effluent of all studied industries, heavy metals were observed but in concentration less than national discharge limits to the surface waters. All of sludge samples were containing of lead. In comparison with average concentration of the earth crust, observed amounts were 1.5 times and maximum 4.5 times. For copper maximum concentration was 4 times higher than earth crust average. In the case of chromium, the content was less than earth crust level in all samples. For cadmium, measured concentrations were extremely high in comparison with the earth crust (23times higher than earth crust average). Considering world standard of biosolids application to land, observed concentration of present study were lower than ceiling concentrations so presence of heavy metals in the sludge of SCIs could not be considered as an environmental and health challenge in short term.