ASIAN JOURNAL OF CIVIL ENGINEERING (BUILDING AND HOUSING)
Year:2015 | Volume:16 | Issue:3|Papers Count:10

One of the most important durability indices affecting the reinforced concrete structures is corrosion of steel reinforcement. Investigations show that the main mechanism of corrosion distorting the long-term performance of such structures is Chloride-induced corrosion.In order to challenge this problem, scientists offer utilizing supplementary cementitious materials. Silica fume is one of the most effective admixtures which control chloride diffusivity and initiation of steel corrosion.The present literature, reviews recent studies on the influence of silica fume on permeability, chloride diffusion, electrical resistivity and reinforcement corrosion.

The objective of this paper is to study the seismic behavior of circular CFT columns under long-term axial loading. Five series of 3-D nonlinear finite element models were developed to investigate the effects of axial load, concrete age, concrete compressive strength, steel tube yield stress and slenderness on one year axial and then cyclic loadings. For creep modeling, RFM method is used to forecast the creep coefficients. Then, the effects of cyclic loading on creeped CFT columns have been investigated. Based on the results, creep causes a reduction in sustainable shear force and ductility ratio and energy absorption capacity of specimens.

In this paper, finite element method is used for the analysis of sequential construction of embankment. The idealized study gives information on the behavior of a multi-stage construction of an embankment over a soft cohesive deposit. If the response is determined after the construction of entire structure, it is likely to be different from the results which are obtained by considering sequential construction procedure. The displacement and stresses have been calculated during each stage of sequential construction of embankment. The developed computer program shows bearing capacity failure at final lift where the algorithm fails to converge leading to failure.

Self compacting concrete (SCC) is a relatively new phenomenon in materials’ science. It is nearly two-decade-old. This type of concrete, with its special features, provides new possibilities that can be used to overcome problems resulted from the lack of proper density in concrete such as reduction of longevity and durability.In recent years in Iran, rise of concrete production costs, especially the cost of cement, has always been a concern of concrete producers and consumers. Using slag and industrial waste to replace part of cement in SCC can reduce its cost and also helps reducing environmental pollution. In this study, it is attempted to use the slag of Sarcheshmeh mineral copper complex as part of cement for producing SCC and also, investigating the chemical and physical properties of slag material and mechanical properties of SCC, including its compressive strength. Therefore, the physical and chemical analyses were performed on the slag and cement. Then by making 10 cm sample cubes with different percentages of waste namely: 20%, 25%, 30%, 35% and 40% of slag, the SCC pasty phase tests such as J-Ring and V-Funnel were performed on fresh SCC and finally, to achieve the optimum mix design (the most appropriate percentage of slag material share of total cementitious materials), compressive strength tests were done on cubic samples and their mechanical properties were studied. The optimum replacement of cement-like substance material was chosen based on the criteria of resistance compressive strength of 7, 14, 28 and 42 days ages of concrete. The results showed that compressive strength of concrete at 28 days age with a substantial percentage of the slag material was not significantly different from the SCC samples without slag. By studying other SCC characteristics such as durability, this material can be introduced as a suitable alternative for part of cementitious materials in SCC.

This paper presents the comparative study of pounding response of multi-degree-of- freedom (MDOF) system by using various impact simulation techniques. The prediction of impact response of three adjacent MDOF stick system is carried out by means of spring-dashpot contact element, which will be activated only when the masses of adjacent structures comes in contact. The stick model study is entirely being made on MATLAB programming tool. The few sets of obtained response of MATLAB programs are also been compared with the SAP results for the validation purpose. The entire investigation has been done by using nonlinear step by step time history method.The result indicates that the nonlinear contact spring impact simulation models give lesser magnitude pounding forces than that of linear contact spring impact simulation models, but as far as their numbers are concerned, they are marginally same in both the types. It was also noticed that in the exterior right flexible structure subjected to pounding for series of structures, the applied ground excitations offers unconventional pattern of absolute shear forces. That means the top storey of the exterior rigid structure during pounding may offer more values of shear forces than the immediately lower storeys.

The seismic response of 20-story benchmark building with semi-active variable friction dampers (SAVFD) is investigated under various earthquake ground motions. A recently proposed predictive control algorithm is employed. A parametric study is carried out to arrive at optimum value of gain multiplier so as to have maximum response reduction. The numerical study is carried out for the benchmark building installed with SAVFD and compared with passive and uncontrolled case. The effectiveness of dampers is studied in terms of the reduction in structural responses and performance criteria. To reduce the cost of dampers study is carried out with lesser number of dampers at appropriate locations. Results show that SAVFD reduces earthquake responses effectively with better performance in respect of acceleration response reduction as compared with passive dampers. In addition, it is observed that the lesser number of dampers at appropriate locations results similar response reduction which reduces cost of the dampers.

In this paper, optimal design of latticed columns is performed under static loads utilizing two new algorithms, Colliding Bodies Optimization (CBO) and Democratic Particles Swarm Optimization (DPSO) and also a comparison between two valid codes, AISC 360-10 and Eurocode 3, is investigated. This optimization is on the basis of cost function of materials used in latticed columns, according to each standard and their constructions. Three examples are optimized for each code and their convergence curves are compared. Finally a comparison between two codes is done and the most optimum standard is presented.

In the present investigation, static analysis of thin-walled shell-like structures based on isogeometric approach is presented. Since the higher order NURBS is well suited for describing the exact geometry and providing -continuity, so they are used as basis functions for bridging the gap between design and analysis. The IGA method has been shown that the properties of the NURBS basis functions lead in many cases to superior accuracy per degree of freedom with respect to finite element method. So several thin shell structures are investigated by two approaches of rotation free thin shell element based on Kirchhoff theory and three dimensional solid element by using higher order NURBS basis functions throughk -refinement strategy. It is observed that, 3D solid elements have no difficulties in dealing with curved edges and have good performance in modelling and analysis. For low order of NURBS basis functions, one can observe weak convergence rate, whereas for higher values of order of NURBS, the results are identical to those of shell element, which confirms that, only by applying the lengthwise of mesh refinement, the 3D solid element can have acceptable performance.

Whilst the use of impact damper for single-degree-of-freedom (SDOF) systems has received a significant amount of attention, investigations into their interaction with SDOF systems is rare. In this paper, results of a series of experimental analysis of a horizontal particle impact damper under earthquake and sinusoidally excited primary system are investigated. Specific impact damping is determined for a SDOF. The influence of some system parameters such as clearance, stiffness and specific intensity of excitation are investigated experimentally. Driven by the experimental observation, it has been shown that a value of damping capacity was reached with a particle impact damper. The obtained results proved the efficiency of this process for achieving high structural damping; the results in some instances did not correspond with those found for control of SDOF systems in particular.One of the main contributions of this investigation involves studying the sensitivity to stiffness. Increased stiffness of the vibration system did not necessarily lead to an increase in damping for all modes. Also, the effect of clearance is unpredictable. In short, the achievements gained in the paper have revealed dynamic characteristics, bringing important engineering application. The paper raises these and other issues which require consideration if impact dampers are to be used to control the dynamic response of SDOF systems.

An analytical technique is used to solve the radius of curvature beam equation called the variational iteration method (VIM). VIM leads to high exactness of the solutions with only one repetition. It has been found that VIM is very prolific, rapid, functional, and do not demand small perturbation and is also sufficiently accurate to both linear and nonlinear problems in engineering. The obtained consequences show that the approximate solution is uniformly legitimate on the whole solution field in comparison with the numerical solution. VIM could simply be enlarged to other powerfully nonlinear problems and it could be found widely feasible in engineering and science. The results of this method (VIM) are compared with the obtained results of numerical solution that shows the results of the present method are in excellent agreement with numerical solution.