سال:1392 | دوره: | شماره: |تعداد مقالات:11

The increasing number of reinforced concrete structures affected by corrosion makes the study of their protection an import parameter. Usage of different types of surface coatings on rebars for the corrosion protection has not proved to be a reliable system on account of many reasons like reduction in bond stress between the concrete & rebar and so on. The standard procedure of rehabilitation of corrosion affected structural elements. viz., chipping the cover concrete, exposing the rebar, cleaning rebars, applying corrosion protection coating to the rebar, providing formwork, pumping of micro concrete, etc becomes labour intensive and uneconomical in addition to a lot of disturbance caused to the occupants. Hence, sacrificial anodes are being increasingly used during the rehabilitation of corrosion affected Reinforced Concrete (RC) structures. The self regulating anodes comprise of zinc metal covered with porous matrix, which sacrifices itself and protects the corrosion of rebar. The paper presents the results of the study carried out on the performance of sacrificial galvanic anodes installed in RC structural elements with and without preconditioning methods.

In this paper, a new hybrid Particle Swarm Optimization (PSO) and Harmony Search (HS) algorithm, denoted by PSOHS is presented. This hybrid algorithm is designed to improve the efficiency of the PSO and remove some of the disadvantages which reduce the capability of the PSO. The main problem of the PSO is the lack of balance between exploration and exploitation of the algorithm. Another problem is how to handle the violating particles from feasible search space without reduction in the performance of the algorithm. The problem of unbalanced exploration and exploitation is solved using linear varying inertia weight. The second problem is solved in some other algorithms via reproduction of the violating particles using the HS algorithm. In this paper, these two approaches are combined to achieve a more efficient algorithm for engineering design problems. To show the higher capability of this approach compared to other works, several benchmark engineering examples, which have been considered previously and solved utilizing a variety of optimization algorithms, is solved by the present hybrid algorithm. Results illustrate a desirable performance of the PSOHS in both obtaining lower weight and having a higher convergence rate.

The deterioration rate of plain geopolymer concrete specimens when exposed to aggressive environment was low and the specimens were stable when compared to plain ordinary Portland cement concrete. Attention was paid upon the durability and flexural behaviour of reinforced geopolymer concrete beams, manufactured using low calcium class F Indian fly ash, exposed to 10% concentration of sulfuric acid attack and chloride attack for a period of 180 days.100mm100mm cross-section and 500mm long beams with 1% tensile reinforcement were cast. Concentration of sodium hydroxide was taken as 8M for a cube compressive strength of 30N/mm2. Test results showed very little surface erosion, 3.26% and 1% weight loss, 10.64% and 4.47% decrease in ultimate moment for specimens exposed to chloride and acid attacks, respectively. This has revealed better performance of reinforced geopolymer concrete beams subjected to aggressive situation and is in line with earlier studies on plain geopolymer concretes. The erosion of surface of specimens had not led to corrosion of steel bars which underlines the geopolymer concreteas an impermeable one. X-ray diffraction (XRD), EDAX and scanning electron microscopy (SEM) analyseswere done to compare results of reinforced geopolymer concrete beams, before and after immersion in aggressive liquids.

The investigation of the self-feeding forces impact on the structural displacements in turbulent wind is presented. This impact is dealt with as a ratio of the displacement variances with and without the self-feeding forces, and a formula is proposed for this ratio on a 2DOF section-model. The paper also presents a method to determine the softness of the flutter that affects significantly the impact of the self-feeding forces over the buffeting forces. This method highlights the influence of the flutter derivatives on how the structural parameters affect the softness.

Appropriate modeling of connections behavior is needed for seismic evaluation of structures. However, large dispersion is observed in welded steel moment frame connections performance during recent earthquakes and experimental tests. In this study, the effect of dispersion in pre-Northridge connections characteristics is investigated. Two mid-rise steel moment frames are designated. Various types of fractures in beam-column connections with various configurations are modeled. Sensitivity study is carried out on parameters affecting the structural response for two probability levels by implementation of nonlinear dynamic analysis. Results show that variation in connection characteristics moderately affects the displacement demands of structures.

An investigation on the performance of reinforced concrete beam column joints under cyclic loading is reported. Joints have been cast with adequate and deficient shear capacity and bond of reinforcements at the beam column joint. Fiber Reinforced Cementitious Composites (HPFRCCs) like Slurry Infiltrated Mat CONcrete (SIMCON) have been applied on the joints in different volume fraction and aspect ratios. The column subjected to an axial force while the beams are subjected to cyclic load with controlled displacement. The displacement is increased monotonically using a hydraulic push and pull jack. The hysteretic curves of the specimen have been plotted. The energy dissipation capacity of retrofitted beam column joints with various SIMCON configurations has been compared. In addition, comparisons were made between experimental and analytical results of control specimen and SIMCON retrofitted specimen. The results show that the strengthened beam column joint exhibit increased strength, stiffness, energy dissipation and composite action until failure.

An effective method for the damage diagnosis of structures under seismic excitation via discrete wavelet transform is proposed in this paper. The proposed method is based on the detection of abrupt changes in seismic vibration responses by the analysis of displacement or velocity responses using wavelet analysis. Also, a wavelet-based method is presented for denoising of displacement and velocity responses for the damage detection problem. The performance of the proposed method for de-noising and damage detection has been investigated using a benchmark problem provided by the IASC-ASCE Task Group on Structural Health Monitoring and a simulated shear wall model. The obtained results indicate that the proposed method can be provided useful information for the damage occurrence using the seismic response of structures.

This work aims to study the effect of connector interaction in behaviour and ultimate strength of intermediate length CFS open sections under axial compression. A stiffened channel section is considered for the study it included a total of 6 structural tests. Finite element models were developed using ANSYS including geometric and material non linearities. The numerical results were validated on the basis of the test results and both has good agreement with each other. An extensive parametric study on the influence of depth and spacing of connectors was carried out using this finite element procedure. The strength predicted by the finite element model and tested specimens of open sections were compared with the design strength calculated using the DSM–AISI 100: 2007, AS/NZS: 4600-2005 and IS: 801-1975. Recommendations concerning the design of the section with connectors are given based on the results.

This paper introduces a number of simple findings that lead to the efficient design of system based earthquake resisting moment frames. A system based design is defined as one that leads to minimum drift and minimum weight solutions, for code recognized seismic frameworks, without resorting to complicated numerical analysis. These findings are used to form an algorithm, which in turn leads to closed form solutions for system-specific performance-based design of earthquake resisting moment frames. The results of some of these findings may be summarized as follows;- the efficient design of a representative closed loop sub-frame is one involving beams and columns of equal strength and stiffness,- a design may be said to be efficient when the demand/capacity ratios of all of its members are as close to unity as possible,- the magnitude of a mid-span concentrated load may be considered small if it is less than half its plastic collapse value acting alone on the same beam.

Large amount of natural lands have been converted to urban due to rapid population growth and rural to urban migration. Prior land use pattern also getting changed in their activities. Finding out the ways and means for protection of land using environmental quality is the need of the hour. Sustainable land management is a critical challenge of earth system and resources on the land. Protection of productive agriculture land has become a major priority in many regions of the world. Impact can be defined as any change in the physical, chemical, cultural (or) socio-economic, environmental system as a result of activities related to that of land use. In particular the changes of Land Use and Land Cover modify the physical parameter of earth surface thus affecting material and energy interchanges between land and atmosphere. LULC - change directly impacts bio diversity, modifying the composition, and structure of ecosystem. Agricultural land used as an urban area have significant (-ve) effects on the environmental quality as they generate environmental problems such as impact of the water cycle, impact on the ground (or) surface water, emission of water pollutants, air pollutant, soil degradation etc. This research is mainly concentrates on LULC - change by using Quantum GIS Software (QGIS). The range of land use conversions is identified and the ways & means for the various impacts are analysed based on LULC. This research paper has identified the ranges in variations of land use and degradation of the environmental quality.

Pounding between adjacent buildings is a detrimental issue for buildings in cities because they are closely located while vibrating out of phase due to different dynamic properties (mainly different mass and/or height) during earthquake excitation. This paper presents a numerical study on the pounding between the adjacent buildings with different masses during earthquake excitation. The buildings modeled via lumped mass procedure are connected by linear vico-elastic contact force model during pounding. Seismic responses of the buildings due to earthquake acceleration are obtained for different building configurations and the results are discussed and compared. Pounding effect is amplified for the lighter building while pounding effect is negligible for the heavier building.