سال:1387 | دوره: | شماره: |تعداد مقالات:7

This paper presents a particle swarm ant colony optimization for design of truss structures. The algorithm is based on the particle swarm optimizer with passive congregation and ant colony optimization. The particle swarm ant colony optimization applies the particle swarm optimizer with passive congregation for global optimization and ant colony approach is employed to update positions of particles to attain rapidly the feasible solution space. Ant colony optimization works as a local search, wherein, ants apply pheromone-guided mechanism to update the positions found by the particles in the earlier stage. A new relation is defined for the inertia weight, and the terminating criterion is changed in the way that after decreasing the movements of particles, the search process stops. With these changes, the number of iterations does not increase. The proposed method is tested on several benchmark trusses from literature. The result comparisons with particle swarm optimizer, particle swarm optimizer with passive congregation and other optimization algorithms demonstrate the effectiveness of the presented method.

This paper presents analytical investigation carried out to study the feasibility of implementing water tank as passive TMD using ANSYS. Two multi-storey concrete structures, three and five storey were taken for the study. The water tank was placed at the roof. The mass and frequency of the tank including its water, walls, roof, beams and columns were tuned to the optimized values. The behavior of the tank subjected to four earthquake data, namely, El-centro, Hachinohe, Kobe and Northridge was studied under five conditions, namely tank empty, 1/4th water, 1/2th water, 3/4th water and full tank. The results show if the tank is tuned properly it can reduce the peak response of structures subjected to seismic forces.

The Diss (Ampelodesmos mauritanicus, family of Poaceae) is a very luxuriant plant growing in wild state around the Mediterranean North Africa and dry areas of Greece and Spain. It grows in France, mainly, in the departments of the Alpes-Maritimes, the Var, the South of Corsica and Herault. In the past, it was used as building material because of its mechanical and hydrous qualities. The purpose of this research is to determine the effects of treated and untreated of the vegetables fibres. The use of such a fibrous plant in a cementitious matrix leads to lightweight materials with very attractive tensile behavior that can be used as advantageous infill in structures subjected to seismic effects. The basic vegetable material, very fibrous and siliceous, presents indeed an absorption of about 90% that would be corrected by using optimum water/cement ratio. Moreover, we noted a considerable retardation of setting and very low resistances during the composite tests with natural crushed diss, despite the fact that the fibres have considerable tensile strength about 100 MPa. To improve the fibres contribution in cementitious composites, we have carried out a treatment by boiling the fibres of diss to extract the substances responsible for the bad connection between fibres and the cement paste. The Diss fibres were also prewetted before introduction into the mixer. This treatment will eliminate a loss in workability due rapid absorption, and improve mechanical properties. Thus diss fibres reinforcements in cimentitious composites having encouraging mechanical properties, which may expand the applicability of these composites as masonry units in constructions.

The environment prevalent in ocean necessitates the piles supporting offshore structures to be designed against lateral cyclic loading initiated by wave action. Such quasi-static load reversal induces deterioration in the strength and stiffness of the soil-pile system introducing progressive reduction in the bearing capacity associated with increased settlement of the pile foundation. To understand the effect of lateral cyclic load on axial response of single pile in soft clay, a numerical model has been developed. The theoretical results are compared with the available experimental results so as to validate the theory. This paper presents a brief description of the methodology developed, analysis and interpretations of the theoretical results obtained and the relevant conclusions drawn there from.

An artificial neural network-based model is developed to predict the loss in capacity of reinforced concrete columns subjected to elevated temperature. A series of RC column models have been tested. The process of increasing the temperature is performed while the model columns carrying the service loads, thus simulating the actual condition taking place during real fire event. Different column sections; and aggregate, plaster and admixture types are used. To study the effect of these factors on the residual strength. Results of experimental model tests are then analyzed, clustered and used to train a specially designed artificial neural network (ANN) to be capable of predicting reduced concrete strength. ANN estimations, when compared to model test results, showed very good agreement. Such observation indicates that ANN could be effectively used to accurately predict strength reduction due to exposed to elevated temperature.

Jacketing with composites on the outer periphery is one of an effective way to enhance the torsional capacity of distressed reinforced concrete structures and to change the mode of failure from brittle to ductile. Ferro cement due to its better crack arresting capacity and better strain distribution across the section make it one of the suitable composite materials in the field of strengthening reinforced concrete members. An experimental programme consisting of casting and testing of beams with "U" wraps (more commonly used strengthening technique) was conducted in the laboratory to study the effect of aspect ratio (ratio of depth to breadth), constituent materials of Ferro cement (viz., number of mesh layers, yield strength of mesh layers and compressive strength of mortar) and concrete strength on ultimate torsional strength and twist. This experimental results briefly recounts that wrapping on three sides enhance the ultimate torque and twist. This strengthening scheme is more effective for higher aspect ratios with high strength jacketing material. An analytical model proposed in this paper for prediction of torque and twist response of jacketed beams is in good agreement with experimental results.

The increase of the pozzolanic admixture (slag) added as a replacement for cement causes a disadvantage of a longer initial setting time and a slower strength development in cold time. The aim of the present experimental work is to evaluate the influence of mineral activator (hydrated lime) of slag cement (latent hydraulicity) on the physico-chemical properties of slag cement (C.E.M II) and the mechanical behavior (Flexural and compressive strengths) for the mortar. The activation method by hydrated lime of slag cement activates the hydration process, influenced the size of particles and leads to the formation of ettringite and CSH (tobermorite) at the early ages of hydration. In this experimental study, the setting agent Ca(OH)2 used for activation slag cement is used in the proportions of 0%, 2%, 4%, 6%, 8% and 10% by various methods (substitution and addition by mass of slag cement). The physical properties of cements (C.E.M II) activated by the calcium hydroxide at anhydrous state and the state hydrated (specific weight, fineness, consistency of the cement pastes and setting times) thus the characteristics of the mortars made at their bases, such as, the mechanical behavior (Flexural and compressive strengths for the mortar) after 7, 28 and 90 days were studied.