سال:1386 | دوره: | شماره: |تعداد مقالات:9

Construction planners often face the challenge of optimum resource utilization to compromise between different and usually conflicting aspects of projects. Time, cost and quality of project delivery are among the crucial aspects of each project. Emergence of new contracts that place an increasing pressure on maximizing the quality of projects while minimizing its time and cost, requires the development of models considering quality in addition to time and cost which has modeled extensively. In this paper, a new metaheuristic multi-colony ant algorithm is developed for the optimization of three objectives time-costquality as a trade-off problem. An example is analyzed to illustrate the capabilities of the present method in generating optimal/near optimal solutions. The model is also applied to two objective time-cost trade-off problem, and the results are compared to those of the existing approaches.

The aim of the present paper is to reviews a novel modular constructional element for the building and construction industries that was patented by Coventry University. Modular elements have been used in the past in the construction of structures in order to speed construction and cut on time and cost. The modular element, the subject of this study, comprises hexagonal elements made of steel or other appropriate material, assembled together to form a constructional assembly of honeycomb form secured by fixings that clamp together the sides of adjacent elements. Concrete, or other appropriate material, is disposed within the elements providing a composite type of action. Reinforcement is also present in the form of bars or tubes, providing extra strength to the assembled element. The novel type of modular construction has potential applications in the building, construction, substructure and highways sectors. It could be used as a permanent or temporary structure for roofs and walls. It may also be used for concrete pavements, tunneling, and retaining wall structures.

Design sensitivity analysis is a necessary task for optimization of structures. Methods of sensitivity analysis for linear systems have been developed and well documented in the literature; however there are a few such research works for nonlinear systems. Nonlinear sensitivity analysis of structures under seismic loading is very complicated. This paper presents an analytical sensitivity technique for Reinforcement Concrete Moment Resisting Frames (RCMRF) that accounts for both material and geometric nonlinearity under pushover analysis. The results of proposed method are compared with the results of finite difference method. A three-story, two bays moment frame example is used to illustrate the efficiency of the method. This technique can be very useful and efficient for optimal performance-based design of RC buildings.

This paper presents output of an experimental research program to relate various properties of cement sand mixes with its compressive strength. Since a designer always knows the target compressive strength, the findings of this paper immediately provide him with a realistic estimate of the remaining important properties of cement sand mixes.This investigation includes cement sand mortars and micro-concretes, each of two different varieties. Cement sand mortars were made of four different proportions whereas micro-concretes were of two different proportions. Three water cement ratios with varying dosage of super plasticizers were also used for each of the six mixes. The proportion of 1:6 cement sand mortar was studied in further detail by adding water proofing compound (WPC i.e. Impermo) and silica fume in different proportions. The relationships between cylindrical compressive strength, split tensile strength and water permeability have been established.

This paper presents improved analytical method for predicting deflection of reinforced concrete beams. This approach considers stiffness of steel and concrete separately. A number of diverse analytical models have been proposed by various researchers aimed at accurately predicting deflection of reinforced concrete bent elements. In this paper energy model is formed and varied. Deflection is determined from the potential energy model. To establish the validity of the proposed model correlation of analytical solution of existing models are conducted. Variation model solutions generally show very good agreement with results obtained other analytical methods.

In this paper, a numerical model for wave induced vibrations in buildings is developed based on a substructure method by using original Matlab software developed by the authors. A dynamic analysis of the structure subjected to an incident wave field, is performed using the subdomain formulation. The structure is analysed with a finite element method and the unbounded soil domain is computed with a boundary element method using the Green's functions of a layered halfspace.The problem of eigenfrequencies for embedded foundations in the frequency range of interest for seismic wave induced vibrations is addressed. A weakly singular boundary integral equation in elastodynamics for heterogeneous domains is presented, which combines the boundary integral equations in terms of the displacement and its normal derivatives. Based on an extensive parametric study, general conclusions are drawn for practical range of dimensionless parameters.Insight in the effect of soil-structure interaction and the determining factors for seismic wave induced vibrations is obtained from the results of parametric study. The influence of the type of foundation (rigid or flexible, surface or embedded, slab strip or box foundation) is specially emphasized.

This paper presents a detailed experimental study on sulphate ion attack on ordinary, standard and higher grade concretes at early ages i.e. 7 days and 28 days. The main variable investigated in this study is percentage variation of fly ash. The cement is replaced by fly ash up to 40% at a regular interval of 10%. The compressive strength and weight loss were studied. Test results indicate that use of fly ash in concrete has improved performance against sulphate attack in all the three grades of concrete. A simple empirical equation has been proposed to study the behavior of concrete under acid attack using best fit method.

It is known that large inelastic deformation limits of individual members allow entire structures to endorse severe ground motion while dissipating significant levels of seismic energy. Plastic hinge formations associated with lateral displacement excursions is favored in beams and girders rather than in columns to ensure that the overall structural integrity is not compromised. Plastic hinges can occur in columns, however, particularly at the base of multistory frames and bridges where incurred, damage acts to dampen seismic forces considerably. Ductile behaviour is hence essential at these crucial sites to prevent complete structural collapse under sustained loading. The structural response during earthquakes have indicated that the majority of the column failures was caused by high shear stresses, insufficient transverse reinforcement rendering those members ineffective at dissipating seismic energy and inadequate ductility rapidly leading to failure. Typical procedures to compensate for the deficiencies involve external retrofitting of these columns. Recent research works 1,2) have indicated that ferrocement jacketing may be used as an alternative technique to strengthen RC columns with inadequate shear strength. The present objective is to complement the earlier work of the authors 3,4,5), on the use of ferrocement jackets for seismic retrofit of non-ductile reinforced concrete columns with inadequate shear strength. The response of R.C and ferrocement retrofitted columns to seismic loading was examined under three different axial load ratios.

Iran is situated in a highly seismic part of the world and has been frequently struck by catastrophic earthquakes during her recorded history. Any study of earthquakes and earthquake engineering is based on accurate knowledge of the motions of the ground during important earthquakes. To obtain such data and information a network of strong motion accelerographs is maintained by the BHRC from 1973. The network consists of more than 1100 accelerographs. In the second half of the year 2006, 130 accelerograms (with PGA greater than of 0.01g) were recorded by 90 accelerographs, which were triggered by 99 earthquakes with different magnitude. In this period the Nov, 5th koloor earthquake at Ardebil province was the strongest event which triggered 6 accelerographs with PGA greater than 200 cm/s/s at koloor station. In this article the most important earthquakes and those with more than three or more accelerograms in the studied time period are discussed in brief and the detailed information is presented in Table 1.