Current Issue : January - March Volume : 2012 Issue Number : 1 Articles : 6 Articles
Damage pattern recognition research represents one of the most challenging tasks in structural health monitoring (SHM). The vagueness in defining damage and the significant overlap between damage states contribute to the challenges associated with proper damage classification. Uncertainties in the damage features and how they propagate during the damage detection process also contribute to uncertainties in SHM. This paper introduces an integrated method for damage feature extraction and damage recognition. We describe a robust damage detection method that is based on using artificial neural network (ANN) to compute the wavelet energy of acceleration signals acquired from the structure. We suggest using the wavelet energy as a damage feature to classify damage states in structures. A case study is presented that shows the ability of the proposed method to detect and pattern damage using the American Society of Civil Engineers (ASCEs) benchmark structure. It is suggested that an optimal ANN architecture can detect damage occurrence with good accuracy and can provide damage quantification with reasonable accuracy to varying levels of damage....
This paper discusses an improvement of the strategy for Quality Signing and Verification Processes. Earlier studies demonstrate that the strategy relies on two processes: Quality Signing Process and Quality Verification Process, respectively. The Quality Signing Process is based on integration of black box (i.e. Combinatorial Interaction Testing) and white box (i.e. Mutation Testing) techniques in order to derive an optimum test suite for the Quality Verification Process. In this case, the generated test suite significantly improves the Quality Verification Process. Unlike the previous work, which deals only with combinatorial logic, an improvement of the strategy now addresses sequential logic, that is, by incorporating both the state of the system as well as the input parameter values as input in both processes. As a case study, this paper describes the step-by-step application of the strategy for testing a 12-bit Linear Feedback Shift Register in a hardware production line. The result demonstrates that the proposed strategy gives saving effort factor of 99.7%. Additionally, the result also demonstrates the need to consider Combinatorial Interaction Testing in both cumulative and normal mode of operation....
To propose an initial formulation for the passive control section of the Turkish Earthquake Code, the impact of base isolation and viscoelastic dampers on a four-storey reinforced concrete (RC) frame building was considered under various one-dimensional quake excitations. Both statically equivalent seismic load methods (comparing Turkish Earthquake code with Uniform Building Code) and linear time history analyses were applied to the RC building based on a portion of the 1999 Kocaeli Earthquake ground motion record (modified to possess predominant spectral periods of T1 = 0.13 sec and T2 = 1.43 sec representing hard and soft soil conditions, resp.). Effective peak ground acceleration was set to 0.40 g. Time history variations of upper column dis-placements and bending moments were compared, as well as storey drift ratios. Reductions of the fixed-base case column bending moments were obtained of up to 73% under base isolation, up to 25% with viscoelastic dampers, and up to 83% (with a unified response reduction factor) when both devices were both present....
In recent years, an emerging technology termed high-performance concrete (HPC) has become popular in construction industry. The constituent materials of HPC depend on the desired characteristics and the availability of suitable local economic alternatives. One of these alternatives is steel slag waste material. It is an industrial by-product waste particles resulted from reinforcing steel bars manufacture, its production is very huge; total quantity produced from all steel rebars manufacture factories in Egypt is nearly million tons/year. HPC made with steel slag aggregate (SSA) is considered as green concrete, using of steel-slag as a coarse aggregate increases the probability of consuming such large accumulations of slag (in HPC industry) which they represent as a waste and polluted material in environment. A total of eight under, balanced and over reinforced concrete beams were fabricated and tested. RC beams were made with HPC having compressive strength of 58.1 and 75.6?MPa and tensile reinforcement ratio in the range of 0.90 to 4.3%. Data presented concentrated on the chemical, physical, and mechanical properties of the used new material (SSA) and the flexural behavior of reinforced high-performance concrete beams made with steel slag coarse aggregate (RHPC-SSA) beams. It was observed that the RHPC-SSA beams can give satisfactory structural performance according to the American and Egyptian Building Codes....
Two numerical models are investigated to model random water waves (RWWs) transformation due to mild depth variation. Modelling of steady on-shore propagation of small-amplitude RWWs is based on superposition principle of waves of different heights and directions. Each component is simulated through either the parabolic model (PM) or the elliptic model (EM). PM simulates weak refraction, diffraction, shoaling, and wave breaking. EM simulates strong refraction, diffraction, and shoaling. Both models neglect wave reflection. Comparison between PM and EM, in test cases that are experimentally measured, proved that both models give good results for unidirectional and narrow-directional RWW. However, EM is more accurate in modelling broad-directional RWWs....
Seismic failure of major concrete dams can be disastrous due to sudden release of reservoir water. At the present study, 203?m DEZ arch dam was selected as case study, and two types of nonlinearity were incorporated in seismic analysis of dam, joint nonlinearity and material nonlinearity. The finite element model of the dam, soil, and water was excited using multicomponent maximum design earthquake record which was extracted from seismic hazard analysis of the dam site. Also seismic performance of the dam was evaluated based on linear analysis. The extension of overstressed areas, demand-capacity ratio, and cumulative inelastic duration were used to identify the necessity of nonlinear analysis. It was found that when contraction joints between dam blocks are modeled, the direction of the principal stresses and their distribution patterns are changed meaningfully. In addition, overstress surfaces on the dam body change in comparison with the model without contraction joints....
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