Iranian Journal of Science and Technology Transactions of Civil Engineering
Volume:38 Issue: 2, 2014

Monotonic triaxial compression, triaxial extension and torsional shear tests were carried out on geotextile reinforced sand and reinforced clay, mainly to investigate the effects of rotation of principal stresses on the mechanical behavior of the reinforced soil materials.The tests were carried out on unreinforced and reinforced specimens with 2, 3 and 4 geotextile layers under three different confining pressures. Investigation of the monotonic behavior of the reinforced materials under different stress paths, i.e. triaxial compression, triaxial extension, and torsional shear shows that direction of principal stresses can have profound effects on the stress strain curve, shear strength, and slope and intercept of failure envelope. Test results reveal that geotextiles improve the mechanical properties of the sand and clay, since both strain at failure and undrained shear strength increase with the number of geotextile layers in sand and clay. In addition, test results indicate that geotextile inclusion enhances the mechanical properties of geotextile reinforced sand and clay, however, geotextiles seems to be more effective when used to reinforce sands.

This paper summarizes the test data obtained from an experimental investigation of einforced concrete (RC) wide beams reinforced with lattice girders, which can also be escribed s one-way slabs, under low-rate (static) concentrated loading applied at their mid-span. ests ere conducted on lattice girder reinforced and traditionally reinforced beam-type pecimens to nvestigate the effect of lattice girder on load carrying capacity. Key aspects of structural esponse uch as the load–deflection behavior, crack patterns, strength and failure modes of the ested eams were recorded and given in this paper. A total of 6 beams with two different einforcement rrangements were tested. Tested beams were simply supported at a span of 2250 mm. ll specimens were tested under static loading and midspan deflections were recorded using a displacement transducer. Similar stiffness was displayed by the lattice girder reinforced and traditionally reinforced beams, but higher resistant capacity was shown by the lattice girder reinforced beams.

In reinforced concrete structures, beam-column joints are one of the most critical regions in the areas with moderate and severe seismic prone areas. Proper reinforcement anchorage is essential to enhance the performance of beam-column joints. Congestion of reinforcement and construction difficulty is one of the critical problems while using conventional reinforcement detailing in beam-column joints of concrete structures. An effort has been made to study and evaluate the performance of beam-column joints. The joints are detailed for higher seismic prone areas as per ACI-352 (Mechanical Anchorage), ACI-318 (Conventional Hooks Bent) and IS-456 (Full Anchorage Hooks Bent) along with confinement as per IS-13920 and proposed X-cross plus hair clip bar joint reinforcement. Apart from finding the solution to these problems, significant improvements in seismic performance, ductility and strength were observed while using mechanical anchorage in combination with X-cross plus hair clip bars. To assess the performances of anchorages and joint details, the specimens were assembled into two groups of three specimens each. The specimens were tested under reversal loading and test results were evaluated and presented in this paper.

In a Seismic Force Resisting System (SFRS), beam-column joints are crucial structural elements. Failure of these elements may lead to total collapse of a structure. Recent earthquakes have demonstrated that structural systems designed based on current codes of practice are vulnerable to sever damages, mostly due to undesirable performance of joints. In general, design codes do not consider the effects of joint characteristics on the behavior of the structure and treat joints as members which remain elastic during an earthquake. To thoroughly understand the effects of different design parameters on the behavior of beam-column connections in RC structures and consequently on the overall performance of SFRS, a wide range of experiments must be carried out. But prior to a successful setup and conducting any experiments, a theoretical study and numerical simulation is essential. Therefore, having some reliable F.E. models at our disposal plays a significant role in the field of experimental and theoretical research. This paper first explains, in detail, the process for developing a F.E. model for RC beamcolumn connections in the simulation environment provided by ANSYS. Next an attempt is made to study the behavior of RC beam-column joints subjected to seismic forces using the developed model. Finally, the effects of main joint characteristics including ductility, moment capacity ratio, type of loading, ultimate loads, over-strength factors and joint transverse reinforcement are investigated.

In this paper, free vibration of axially moving symmetrically laminated plates subjected to in-plan forces is analyzed using the element-free Galerkin method. This category includes symmetric cross-ply and angle-ply laminates and anisotropic plates. The governing differential equation for a moving plate is numerically solved using the Galerkin method. The shape functions are constructed using the moving least squares (MLS) approximation and the essential boundary conditions are introduced into the formulation through the use of the Lagrange multiplier method and the orthogonal transformation techniques. The effect of skew roller and intermediate supports on the natural frequency of plate are examined.

HPFRCC materials are a class of cement composites with fine aggregates that exhibit strain hardening behavior under tensile loading. This strain hardening response occurs after the first cracking of the material. In this paper, experimental and theoretical studies were conducted to assess the influence of using HPFRCC material instead of normal concrete in RC beams. The theoretical results for simply supported beams with different values of compressive strengths are presented and compared with the available experimental data. Results indicate that using HPFRCC material instead of normal concrete in RC beams concludes to more ultimate load, deflection and ductility compared to normal reinforced concrete beams. Moreover, new theoretical equations are proposed for estimating the flexural characteristics of reinforced composite and reinforced HPFRCC beams. Results show that the flexural capacity of reinforced HPFRCC beams is about 6.4% higher than that of RC beams. Moreover, flexural capacity of experimental reinforced HPFRCC beams is about 11.2% higher than that of theoretical values.

Quantitative assessment and statistical analysis of medical waste generation at provincial scale in Isfahan was conducted. Results indicated that 59% of the total wastes produced were non-hazardous (general) wastes and the rest were hazardous medical wastes. More than 98% of centers implemented source separation of the wastes at source. Also, more than 91% had a storage room, but only 48% of storage rooms were operated under standard conditions, i.e. storage with appropriate ventilation and temperature control. Only about 21% of medical centers had designated collection vehicles. For the remaining 79% of facilities, the medical wastes were collected (comingled) and transported together with the general or non-medical wastes. As for the treatment of medical wastes, only 7% of centers were equipped with autoclave. Although 22% of centers had incinerators, the majority of them were not functional. Collected wastes from 29% of facilities were disposed together and mixed with the municipal wastes at the same landfill trenches. Wastes from the remaining 71% of centers were landfilled in separate trenches. The waste generation rates for total waste and general (non-hazardous) waste were 3.03 and 1.84 kg/active beds/day, and 1.03 and 0.65 kg/employees/day, respectively. Using multivariate regression analysis of data an empirical equation (Y = 0.55 * NEM + 1.44 * NAB) was established to predict the total amount of waste generated at each facility (Y) as a function of number of active beds (NAB) and number of employees (NEM) of the facility. Strong correlation (R2 = 0.97) between the observed and predicted values was observed.

Precise estimates of reference evapotranspiration (ET0) are necessary for the application of irrigation design and scheduling. Numerous empirical methods for predicting ET0 are available, but their accuracy under different environmental conditions is uncertain. Greater uncertainty exists under greenhouse conditions because these methods were designed to apply to field situations, and greenhouses have an effect on the temperature, humidity and wind, etc. In this study, the results of 13 different common daily ET0 estimation methods, namely FAO56 Penman – Monteith, Hargreaves-Samanι, FAO-24 Blaney-Criddle, FAO-24 Radiation, Priestley-Taylor, Makkink, Turc, Linacre, Jensen-Haise, Copais, Pan Evaporation, Rn-radiation and Rs radiation are compared with lysimetric measurements in an area of Fars (Badjgah) in a plastic greenhouse to provide helpful information for selecting the appropriate ET0 equation to use. In addition to daily values, smoothed daily and mean 10-day ET0s were estimated to study the effect of daily weather data fluctuations on the precision of predictions. Performances of ET0 methods are evaluated by four statistical criteria along with regression indices. The results indicate that FAO Penman Monteith and Linacre are the most and the least appropriate methods for estimating daily ET0 in greenhouse conditions, respectively. For outdoor conditions the best and worst results were obtained from FAO24- Radiation and Copias methods, respectively. Smoothing weather data, gave better regression fits for FAO Penman-Monteith and FAO24-Radiation methods for both greenhouse and field conditions than those for daily weather data. Better predictions were obtained for field than greenhouse conditions. The total ET0 values in greenhouse were about 0.85 of those measured in outdoor lysimeters.

This paper focuses on the design point and the failure probability of problems with continuous random variables. The charged system search (CSS) algorithm is utilized as the optimization tool to achieve minimum reliability index under limit state function. In order to acquire the optimal solution, random variables such as elastic modulus, loads, and geometric parameters are selected as decision variables of the problem which are optimized by means of the CSS algorithm. This algorithm is inspired by the Coulomb and Gauss’s laws of electrostatics from physics. In order to evaluate the accuracy and efficiency of this algorithm, several numerical examples are studied and the results are compared to those of the existing methods. The proposed method is capable of finding a design point over the failure surface and calculates the reliability index with a reasonable accurately. As the proposed framework enforces low computational time and holds a satisfactory convergence rate, it is a competent methodology to calculate different types of reliability problems.

Sluice and radial radial gates are common devices used for flow control in hydraulic structures. This paper demonstrates the variation of the contraction coefficient of sluice gates and three types of radial gates (namely, Hard-Rubber, Sharp and Music Note gates) by using Energy and Momentum Equations (EMEs). This paper presents a novel method for estimating the acting force behind these gates under free and submerged flow conditions. A minimum value of the contraction coefficient for sluice gates was obtained under a certain value of relative gate opening. Under a specific condition, Hard-Rubber gates have a larger contraction than Sharp gates, while Music Note gates have the least contraction. It is recognized that the contraction coefficient decreases as the gate lip angle and the gate opening increase. Under submerged flow conditions, the contraction coefficient of sluice and radial gates would be either increased or decreased depending on the level of flow submergence. It is concluded that using the proposed contraction coefficient in estimating the discharge coefficient demonstrates an acceptable accuracy.

Seismic coefficient values coupled with minimum pseudo-static safety factors are still used for analysis where selection of seismic coefficients relies on expertise and judgment. However, safety factor approach does not give any idea about the deformations and displacements that are expected to occur during earthquake loading. Displacements are mostly evaluated by equations based on yield acceleration of the slope and maximum acceleration of sliding mass. The method based on rigid block gives co-seismic permanent slope deformation when its factor of safety equals 1.0, hence, there is a need to link slope displacements, seismic coefficients and pseudo-static safety factors. This will enable the designers to predict slope displacements based on selected seismic coefficients. In the present paper, slope displacements obtained for different peak ground accelerations and safety factors are used to propose charts linking co-seismic slope displacements (D), seismic coefficients (􀝇􀯛) and pseudo-static safety factors (FS), which are important parameters in pseudo-static approach. This enables the 􀝇􀯛 values to be chosen based on allowable displacements instead of using judgment and expertise. Results show that 􀝇􀯛 values for any allowable displacement should be based on anticipated PGA and FS values. Subsequently, slope displacements are utilized in developing a novel displacement-based methodology to select the seismic coefficient which will be used to calculate the pseudo-static safety factor.

This study extends the theory of three-dimensional consolidation to unsaturated soils and formulates the theory for finite element analysis by treating the pore water and pore air as a mixed pore fluid. This formulation considers variations in the permeability and compressibility of the mixed pore fluid with changes in the void ratio and degree of saturation. The compressibility of the mixed pore fluid is derived using Boyle’s Law. An example of the settlement of a vertical drain is investigated and discussed; this example demonstrates that the numerical analysis theory is applicable and reliable. The results indicate that the rate of consolidation of unsaturated soils is clearly slower than that of saturated soils, the rate of dissipation of the pore fluid pressure is considerably slower, and the permeability of the mixed pore fluid decrease during consolidation. This theory is applicable to unsaturated soils with high degrees of saturation and can be used to obtain more reliable predictions of unsaturated soil consolidation.

For a symmetric structure the degrees of freedom (DOFs) in two sides of the axis of symmetry can be either symmetric or anti-symmetric. If there is no active DOF on the axis of symmetry, then we will have the Form II symmetry for the structural matrices, and alternatively if we have some active DOFs on the axis, we will have Form III symmetry. These forms are already developed and employed in structural dynamics and stability analysis of frame structures. However, for the structures having both symmetric DOFs and anti-symmetric DOFs, simultaneously, we will have different canonical forms, defined in this paper as the Form A and Form B symmetry. Thus the main objective is to develop these forms and explore the governing relationships. The presented method is then applied to the analysis of symmetric structures.