Current Issue : October - December Volume : 2015 Issue Number : 4 Articles : 5 Articles
A two-stage method is proposed to properly identify the location and the extent of damage in shear frames. In the first stage, a story\ndisplacement index (SDI) is presented to precisely locate the damage in the shear frame which is calculated using the modal analysis\ninformation of the damaged structure. In the second stage, by defining a new objective function, the extent of the actual damage is\ndetermined via an imperialist competitive algorithm. The performance of the proposed method is demonstrated by implementing\nthe technique to three examples containing five-, ten-, and twenty-five-story shear frames with noises and without them in modal\ndata.Moreover, the performance of the proposed method has been verified through using a benchmark problem.Numerical results\nshow the high efficiency of the proposed method for accurately identifying the location and the extent of structural damage in shear\nframes....
This paper investigates the effect of improper posttensioning of a 2-way spanning concrete slab subject to a central point load. Due\nto plate slippage alone, the support conditions only offered a 1-way spanning action which could have led to premature failure\nwith dangerous consequences. Posttensioning can strengthen a flat slab against punching shear by controlling deflections and\ncracking under service loads compared with traditional punching shear reinforcing methods leading to more slender structures\nand economic solutions for longer spans. However, if the method is not properly applied, these thinner floor plates can fail in a\nbrittle and sudden manner by punching at ultimate limit state and excessive deflection in serviceability. Concrete slabs containing\ntraditional shear reinforcement performed adequately and demonstrated that the critical punching shear perimeter, defined as twice\nthe depth of the slab, was confirmed from measured deflections and crack pattern analysis....
An approach is suggested to reduce the peak and average control forces of actively controlled structures. In this method, responses\nof an actively controlled building should be much smaller than the responses of the same building controlled by the similar passive\ncontrol mechanism. This approach leads to a time varying gain matrix, which is not restricted by external excitation but it is related\nto the selection of a scalar function. Extensive numerical analyses by using various scalar functions show that the proposed strategy\neffectively can reduce the need of the required control force consumptions....
Reinforcement of structures aims to control the input energy of unnatural and natural forces. In the past four decades, steel\nshear walls are utilized in huge constructions in some seismic countries such as Japan, United States, and Canada to lessen the\nrisk of destructive forces. The steel shear walls are divided into two types: unstiffened and stiffened. In the former, a series of\nplates (sinusoidal and trapezoidal corrugated) with light thickness are used that have the postbuckling field property under overall\nbuckling. In the latter, steel profile belt series are employed as stiffeners with different arrangement: horizontal, vertical, or diagonal\nin one side or both sides of wall. In the unstiffened walls, increasing the thickness causes an increase in the wall capacity under\nlarge forces in tall structures. In the stiffened walls, joining the stiffeners to the wall is costly and time consuming. The ANSYS\nsoftware was used to analyze the different models of unstiffened one-story steel walls with sinusoidal and trapezoidal corrugated\nplates under lateral load.The obtained results demonstrated that, in the walls with the same dimensions, the trapezoidal corrugated\nplates showed higher ductility and ultimate bearing compared to the sinusoidal corrugated plates....
Fatigue life of tubular joints in offshore structures is significantly influenced by the degree of bending (DoB). The DoB exhibits\nconsiderable scatter calling for greater emphasis in accurate determination of its governing probability distribution which is a key\ninput for the fatigue reliability analysis of a tubular joint. Although the tubular X-joints are commonly found in offshore jacket\nstructures, as far as the authors are aware, no comprehensive research has been carried out on the probability distribution of the\nDoB in tubular X-joints. In the present paper, results of parametric equations available for the calculation of the DoB have been used\nto develop probability distribution models for the DoB in the chord member of tubular X-joints subjected to four types of bending\nloads. Based on a parametric study, a set of samples was prepared and density histograms were generated for these samples using\nFreedman-Diaconis method. Twelve different probability density functions (PDFs) were fitted to these histograms. In each case,\nKolmogorov-Smirnov test was used to evaluate the goodness of fit. Finally, after substituting the values of estimated parameters for\neach distribution, a set of fully defined PDFs have been proposed for the DoB in tubular X-joints subjected to bending loads....
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