Iranian Journal of science and Technology (B: Engineering)
Volume:34 Issue: 1, Feb 2010

In this paper a method for the vibration analysis of proportional asymmetric shear wall structures is presented. The whole structure is assumed as an equivalent bending-warping torsion beam in this method. The governing differential equations of equivalent bending-warping torsion beam are formulated using the continuum approach and are posed in the form of a simple storey transfer matrix. By using the storey transfer matrices and point transfer matrices, which take into account the inertial forces, the system transfer matrix is obtained. Natural frequencies can be calculated by applying the boundary conditions. The structural properties of the building may change in the proposed method. A numerical example has been solved and presented at the end of the study by means of a program written in MATLAB to verify the method that is being proposed. The results of this example display the agreement between the proposed method and the other valid method given in the literature.

The computational drawbacks of existing numerical methods have forced researchers to rely on heuristic algorithms. Heuristic methods are powerful in obtaining the solution of optimization problems. Although these methods are approximate methods (i.e. their solutions are good, but probably not optimal), they do not require the derivatives of the objective function and constraints. Also, the heuristics use probabilistic transition rules instead of deterministic rules. Here, an evolutionary algorithm based on the hybrid genetic algorithm (GA) and particle swarm optimization (PSO), denoted by HGAPSO, is developed in order to solve force method-based simultaneous analysis and design problems for frame structures. Suitability of the HGAPSO algorithm is compared to both GA and PSO for all the design examples, demonstrating its efficiency and superiority, especially for frames with a larger number of redundant forces.

Experimental investigation was conducted to study the pure torsional behaviour of high-strength concrete (HSC) beams strengthened with carbon-fibre-reinforced-polymers (CFRP) having minimum torsional reinforcement. A total of six beams were tested. Two beams without CFRP were assigned as control beams and the rest were strengthened using CFRP sheets. In this study, different wrap configurations, the effect of different numbers of CFRP plies, and the influence of anchors in U-wrapped test beams considered as variables were investigated. Investigation into ductility using two different concepts showed enhancement in the behaviour of strengthened beams with CFRP. The ductility of the beam strengthened with two complete CFRP layers was fifty percent higher than that of the control beams. The beam strengthened using this scheme showed a 75% increase in torsional capacity compared to the control beam, which was not strengthened. The experimental results were compared with the results from three analytical methods. The ultimate torsional strength resulting from one of the three methods, which was based upon synthesis of an analytical method and average CFRP strains obtained from experiments, was in good agreement with the experimental results.

The importance of ductility in absorbing energy and its improving the structural behaviour under earthquake loading is well-established. Some researchers have noted that the ductility ratio may also be an important parameter for designing structures against explosion-induced forces. However, their works were mainly qualitative and based on the ductility of the structural members. In this article, nine short steel frames with different spans and numbers of storeys, subjected to different blast loadings have been investigated. Nonlinear pushover blast force-displacement curves are evaluated for each frame and the ductility parameters are extracted. The results indicate the significant effects of ductility ratio on the structural response. Also, it is found that the ductility reduction factor under blast loading increases with increasing ductility ratio, irrespective of the period of vibration of the system

This paper presents a new approach for three-dimensional stability analysis of soils using the Zero Extension Line Method. The method assumes the intermediate principal stress-planes to be straight. The geometric considerations for obtaining the orientation of these planes in the plastic zone are described. The equilibrium-yield equations are integrated in these planes to give the total applicable load at the limiting equilibrium state. The method accounts for the nonasssociativity of soil behavior as well. It also considers the effect of partial mobilization of soil strength on the counter side of the slope, on its stability. Based on this method, a computer code, Slope3D8, has been written for three-dimensional stability analysis. Examples have been provided to show the capability of the model in analyzing three-dimensional stability of slopes under drained and undrained conditions. In-plan-curvature of slopes and the centrifugal force resulting from movement of vehicles in curved routes can also be modeled. The model predicts lower ultimate load as compared to the existing three dimensional limit analysis methods. Some of the difference in the results of these two models is due to the aggravating effect of counter side that is not considered by the developed three-dimensional limit analysis models. It has been concluded that the presented model provides a useful tool for three-dimensional stability analysis in soil engineering.

Hydrological forecasting is one the most important issues in water resources systems which helps in dealing with the real time operation, flood and drought warning, and irrigation scheduling. Recent studies have suggested that the use of data fusion approach instead of using a single forecast approach may improve the hydrological forecast skill. This paper presents a comparative assessment of five different methods of data fusions including simple and weighted averaging; relying on the user’s experience; artificial neural networks; and error analysis, by applying them in two real case studies. Multiple linear regression, non-parametric K-nearest neighbour regression, conventional multilayer perceptron, and an artificial neural network improved for extreme value forecasting are used as individual forecasting methods at each case study. Conventional data fusing methods as well as a new proposed statistical method based on the non-parametric K- nearest neighbor model are used for hydrological forecasting. Results of data fusion approach in two contrasting case studies are thoroughly analyzed and discussed. The results demonstrate that the use of data fusion could significantly improve forecasts in comparison with the use of singe models. As a result of this study, it is concluded that time-varying combining methods which benefit from the use of real-time predictors in their fusion procedure could be more promising than others. Also, data fusion by K-NN method outperforms conventional methods by improving forecasts through decreasing the bandwidth of ensemble forecast and error of point forecast in both case studies.

The challenges of water resources sustainable development are enormous. Around the globe, the increasing use of water coupled with environmental deterioration calls for sustainable development of the limited water resources. As a significant part of the world’s population still lacks access to safe water and adequate sanitation, and as global urbanization continues to increase, continuous, comprehensive, coordinated and cooperative water resources management is required for the sustainable future of urban areas. The objective of this study was to assess water resources sustainable development for selected urban areas around the world. Using centralized databases of international agencies for the period of 1993 to 1998, urban information pertinent to water resources were collected, analyzed and modeled. The study database consisted of information regarding urban water accessibility, consumption, price, wastewater treatment, and other pertinent social, environmental and economic indicators. After preliminary evaluation of more than 350 cities around the globe, due to data inaccessibility, incompleteness and missing, 107 cities were selected for detailed analysis. The statistical analyses for the selected cities showed interesting results and relations in connection with urban water resources sustainable development in different regions and countries. For the period of 1993 to 1998, elasticity of database variables were developed. Using elasticities, urban area rankings and addressing water resources sustainable development were suggested. The developed elasticity and rankings were used in taxonomy of the selected 107 cities, and reflected considerable variations in urban water demand and supply development. As each urban area is unique in many historical, geographical, cultural, social, political, environmental and economic aspects, any comparative appraisal needs due consideration of local factors and issues. Nevertheless, the applied comparative appraisal methodology is suggested as a compliment to any other type of appraisal to enhance urban policies in support of sustainable urban water resources development.

One of the most important issues of concern in landfill management is the treatment and management of leachate. In situ aerobic treatment of landfill leachate using leachate recirculation was investigated in this research at laboratory scale. A plastic container with dimensions of 0.5 x 0.5 x 1.0 m was used as a reactor. Two sets of aeration pipes were placed inside the reactor and connected to an air compressor in order to inject air into the waste mass. Leachate was collected in a container at the bottom and pumped to another container at the top, from which leachate was recirculated back into the waste mass. The output of the screen unit of Isfahan composting plant was used as waste material. The composition of the waste was modified by adding crushed glass and shredded paper, plastic and metal containers to obtain the same composition of the collected waste. Twenty eight liters of leachate was recirculated daily for 75 days. Samples of the leachate were collected and analyzed for COD, TDS, TSS, pH, heavy metals and temperature. Total COD removal efficiency of the system was 91%. Temperature increased initially and reached a maximum of 53 °C due to rapid biodegradation of the organic matter. As the biodegradation slowed down, less heat was generated and as a result the temperature inside the reactor dropped. Both TDS and TSS showed an initial rise due to recirculation of leachate. Then, biodegradation of organic matter over time resulted in a decrease in both TDS and TSS. The removal efficiencies of the system for TDS and TSS were 56% and 34%, respectively. Removal efficiencies of 93%, 90%, 43% and 76% for Mn, Fe, Pb and Zn were respectively observed.