A two-step method composed of wavelet transform and model updating method for multiple damage diagnosis in beams

In the present study, a two-step approach comprised of wavelet transform and model updating method for multiple structural damage localization and quantification in beams is proposed. The first step is commenced with applying wavelet transform to axial components of mode shapes so as to predict where the damages are located. During this step, wavelet transform might mistakenly detect a number of elements as impaired due to both sampling interval and middle support effect. In the next step, by defining a damage sensitive objective function consisting of natural frequencies and mode shapes, damage intensities at predicted locations will be computed via model updating method employing ECBO (Enhanced Colliding Bodies Optimization) algorithm. The problem with mistakenly predicted damaged locations will be addressed by reported damage intensities during the second step. The present study also indicates that this two-step method greatly assists in reducing the number of variables during model updating process leading to more precise results. Three numerical examples with multiple damages and noisy modal data are studied in order to guarantee the efficacy of the method. Moreover, one numerical example is solved with a number of other Meta-Heuristic algorithms including GA (Genetic Algorithm), CSS (Charged System Search), Pattern Search and Cuckoo algorithm whose results are compared to ECBO algorithm with the intention of ensuring the veracity of ECBO results. The results vividly demonstrate that this method is highly efficient even in the presence of noise

Preparation of Enteric Coated Pellets Containing Lansoprazole Using Extrusion/Spheronization Technique

Lansoprazole degrades rapidly in an aqueous solution at low pH values. Degradation rate increases at pH values below 4 .The aim of this study was development of enteric coated pellets containing Lansoprazole by an extrusion/ spheronization technique. Eight different formulations based on lactose and six different formulations based on mannitol, consisting of different portions of other excipients including sucrose, hydroxy propyl methyl cellulose, magnesium carbonate, and sodium lauryl sulfate have been prepared. Feret diameter, shape factor, and amount of drug released were determined for each formulation. Among different formulations, F14, which consists of mannitol, sucrose, HPMC, talc, magnesium carbonate, and lansoprazole, is considered to be the best formulation. Six other different formulations for the preparation of enteric coatings based on Eudragit S100, Eudragit L100, triethyl citrate, and talc were prepared and coating procedure on pellets (F14) was performed using coating pan. In vitro drug release tests in acidic media (pH=1.2) and buffer media (pH=6.8) were performed for pellets, coated with each coating formulation and dissolution profile for each formulation was prepared. The pellets coated by formulation F.C 4, consisting of Eudragit L 100, triethylcitrate, and talc, showed a proper in vitro drug release profile. Accelerated stability tests were performed on coated pellets according to USP, and data suggested that pellets will be stable for 2 year

The therapeutic potential of Melissa officinalis L. hydroalcoholic extract and rosmarinic acid in a rat asthmatic model: A study on anti-inflammatory and antioxidant effects

Objective: The article studies how Melissa officinalis L. extract and rosmarinic acid (RA) affect lung inflammation, pathology, and oxidative stress in rats with ovalbumin-induced asthma.Materials and Methods: Asthma was induced in rats using ovalbumin injection and inhalation. The study assessed lung inflammation, pathological changes, and oxidative stress in control, untreated asthmatic rats and three treatment groups. These groups received M. officinalis extract (50, 100, 200 mg/kg), RA (0.5, 1, 2 mg/kg), or dexamethasone (Dex) 1 mg/kg.Results: In the sensitized group, white blood cell counts, malondialdehyde, and nitrite levels increased significantly, while thiol levels and the activity of superoxide dismutase and catalase decreased (p<0.001). However, all treatment groups with the extract, RA, and Dex showed a significant reduction in total white blood cells, eosinophils, monocytes, malondialdehyde, and nitrite levels compared to the asthma group (p<0.001 in all groups). Thiol levels and catalase and superoxide dismutase activity were significantly higher in all treated groups with RA and high extract doses (p<0.001). Lung pathological changes were also significantly less severe in the treated groups with dexamethasone, plant extract, and RA compared to the asthma group (p<0.05 to p<0.001).Conclusion: This study showed that M. officinalis and RA have antioxidant and anti-inflammatory effects in an animal asthma model, suggesting their potential for treating asthma symptoms

The Effect of Melissa officinalis L. Extract on Ovalbumin- Induced Lung Inflammation in Rats

Background and objectives: Asthma is an inflammatory chronic disease that has become prevalent internationally. Melissa officinalis L. as a medicinal plant has long been used in the European and the Iranian traditional medicine for the treatment of several diseases. The biological activities, such as antioxidant, anti-tumour, antiviral, antimicrobial, and anti-inflammatory effects of M. officinalis has been reported. Therefore, the effect of Melissa officinalis L. extract on tracheal smooth muscle responsiveness, white blood cell (WBC) counts, and lung pathological changes of ovalbumin (OVA) induced asthma model rat was examined in the current study. Methods: The hydroalcoholic extract of M. officinalis was prepared using 300 g of powdered leaves. Tracheal smooth muscle responsiveness, lung pathology, and WBC counts were evaluated in control, sensitized to OVA, and sensitized rats treated with dexamethasone and three doses of M. officinalis extract (50, 150 and 200 mg/kg). Results: Tracheal smooth muscle responsiveness to methacholine hydrochloride in all sensitized groups was greater than that of the control group (p<0.001). The treatment of asthma-induced rats with dexamethasone and M. officinalis extracts (50, 100 and 200 mg/kg) remarkably reduced pathological alterations, including; inflammation, muscle hypertrophy and mucus plaques in the lung compared to the sensitized group (p<0.05 to p<0.001). Additionally, M. officinalis extract significantly improved total and differential WBC counts in broncho-alveolar lavage fluid (BALF) (p<0.001 for all groups). Conclusion: Results of the current study showed a preventive effect of M. officinalis extracts on the responsiveness of tracheal smooth muscle and lung inflammation in OVA-sensitized rats

The effect of degradation on seismic damage of RC buildings

The severity of seismic damage of reinforced concrete buildings depends on the tectonic characteristics of area, seismic features of ground motion, quality and quantity of buildings. One of the most important factor\u27s, affecting the seismic damage, is the degrading rate of building. Degradation of stiffness and strength are the parameters, which their effect on the seismic damage of buildings are investigated, using an inelastic dynamic analysis. The buildings which are studied are moment resisting RC frames. In order to study the inelastic dynamic behavior of these buildings, IDARC software is used. Based on the obtained results, 40% degradation of strength or 50% degradation of stiffness will cause severe structural damage in the buildings

Corresponding Author The effect of degradation on seismic damage of RC buildings The effect of degradation on seismic damage of RC buildings

ABSTRACT The severity of seismic damage of reinforced concrete buildings depends on the tectonic characteristics of area, seismic features of ground motion, quality and quantity of buildings. One of the most important factor&apos;s, affecting the seismic damage, is the degrading rate of building. Degradation of stiffness and strength are the parameters, which their effect on the seismic damage of buildings are investigated, using an inelastic dynamic analysis. The buildings which are studied are moment resisting RC frames. In order to study the inelastic dynamic behavior of these buildings, IDARC software is used. Based on the obtained results, 40% degradation of strength or 50% degradation of stiffness will cause severe structural damage in the buildings

A Comparative Study on Sensitivity-Based Damage Detection Methods in Bridges

This paper provides a comparative study on four different sensitivity-based damage detection methods for bridges. The methods investigated in this study are approximation approach, semianalytical discrete approach, and analytical discrete approach, which includes direct differential and adjoint variable methods. These sensitivity-based methods utilize finite element model updating procedure and allow a wide choice of physically meaningful parameters leading to vast range of applications in damage detection. The most important difficulty in these methods is calculation of sensitivity matrix. Calculation of this massive matrix is repeated in each iteration and has a significant effect on the efficiency of method. In this study, the acceleration measurements are simulated from the solution to the forward problem using finite element method under moving load with various speeds, along with the addition of artificially produced measurement noise. Various damaged structures with different damage patterns including single, multiple, and random damage are considered and efficiency of four sensitivity methods is compared. Moreover, various possible sources of error such as the effects of measurement noise as well as initial assumption error in stability of the methods are also discussed

Damage Detection of Bridges Using Vibration Data by Adjoint Variable Method

This research entails a theoretical and numerical study on a new damage detection method for bridges, using response sensitivity in time domain. This method, referred to as “adjoint variable method,” is a finite element model updating sensitivity based method. Governing equation of the bridge-vehicle system is established based on finite element formulation. In the inverse analysis, the new approach is presented to identify elemental flexural rigidity of the structure from acceleration responses of several measurement points. The computational cost of sensitivity matrix is the main concern associated with damage detection by these methods. The main advantage of the proposed method is the inclusion of an analytical method to augment the accuracy and speed of the solution. The reliable performance of the method to precisely identify the location and intensity of all types of predetermined single, multiple, and random damages over the whole domain of moving vehicle speed is shown. A comparison study is also carried out to demonstrate the relative effectiveness and upgraded performance of the proposed method in comparison to the similar ordinary sensitivity analysis methods. Moreover, various sources of errors including the effects of noise and primary errors on the numerical stability of the proposed method are discussed

Assessment of axial force effect on improved damage index of confined RC beam-column members

In recent years, different damage indexes have been introduced in engineering literature. The most prominent one among other counterparts is the 1985 Park and Ang's damage index (DIPA), which demonstrates well calibration against experimental results. Hence, it has traditionally had broad application in the field of structural engineering. Commonly, in DIPA relevant parameters are assessed based on plastic-hinge approach, which is not well suited to consider the coupled response between stress resultants (axial force and flexural moment) especially in grossly nonlinear domain. The reason is that named approach is utilized constant shape plastic moment-curvature curve, which is not capable of varying the shape throughout loading history. Another drawback of plastic-hinge method is the difficulty of representing precisely partial yielding of the cross-section. To remedy the situation, the fiber discretization technique is used in this paper. Based on the fiber discretization strategy, not only have the stiffness and strength degradation been characterized more accurately, but also the distribution of plasticity along the plastic zone has been considered. Besides, the multi-directional effect of axial force and flexural moment is considered to assess DI parameters. Additionally, this strategy directly incorporates the effect of transverse confinement into cross sectional constitutive behaviour

Numerical study of RC beams under various loading rates with LS-DYNA

Having an accurate understanding of concrete behavior under effects of high strain rate loading with the aim of reducing incurred damages is of great importance. Due to complexities and high costs of experimental research, numerical studies can be an appropriate alternative for experimental methods. Therefore, in this research capability of the finite element method for predicting concrete behavior at various loading conditions is evaluated by LS-DYNA software. First, the proposed method is presented and then is validated in three stages under different conditions. Results of load–midspan displacement showed good agreement between experimental and finite element results. Capability of finite element method in analyses of beams under various rates of loading was also validated by low error of the results. In addition, the proposed method has reasonable ability to evaluate reinforced concrete beams under various loading rates and different conditions