Effect of Shear Stresses on Failure of Fibrous Composite Materials Accounting for Nonlinear Material Behavior

Variation of shear stresses  xy on failure behavior of different composite materials was investigated for two types of composites; Boron-Epoxy Narmco 5505 and Carbon-Epoxy AS4 (3501-6). The effect of material nonlinearity on failure behavior of unidirectional fibrous composite laminates was considered for several fiber-orientation angles; ϴ=15, 30, 45, 60 and 75 degrees. An energy-based nonlinear material model was adopted to predict the mechanical properties of a unidirectional composite lamina. A compatible failure criterion for nonlinear composite materials was utilized which incorporates the material model into the failure criterion. The resulting failure envelopes were compared for all the cases

Coupled Field Equations for Saturated Soils and Its Application to Piezocone Penetration and Shield Tunneling.

An elasto-plastic coupled system of equations are formulated here in order to describe the time-dependent deformation of saturated cohesive soils. Formulation of these equations is based on the principle of virtual work and the theory of mixtures for inelastic porous media as proposed by Prevost (1980) and Kiousis and Voyiadjis (1988). The saturated soil is considered as a mixture consisting of two deformable media, the solid grains and the water. Each medium is regarded as a continuum and follows its own motion. The coupled equations are developed for large deformations with finite strains in an updated Lagrangian reference frame. The coupled behavior of the two phase material is implemented into the finite element program GAP/CTM (Geotechnical Analysis Program based on the Coupled Theory of Mixtures), which is developed by the author. This formulation is applied in the analysis of two geotechnical problems. The piezocone penetration and the shield tunneling in cohesive soils. The piezocone penetration in cohesive soils is numerically simulated and implemented into the finite element program (GAP/CTM). The continuous penetration of the cone is simulated by applying an incremental vertical movement of the cone tip boundary. The numerical simulation is done for two cases. In the first case, the interface friction between the soil and the piezocone penetrometer is neglected. In the second case, interface friction is assumed between the soil and the piezocone. Results obtained from the simulation using the proposed model are compared with those obtained from the miniature piezocone penetration tests (PCPT) for cohesive soil specimens conducted at the LSU calibration chamber. The resulting excess pore pressure distribution and its dissipation using the numerical model are compared with some available predicting methods. A two-dimensional computational model is developed in order to simulate the continuous advance of the Earth Pressure Balance (EPB) Shield during the tunneling process in cohesive soils. This model is implemented into the finite element program (GAP/CTM). The computational model is based on the plane strain transverse-longitudinal sections that can incorporate the three-dimensional deformation of the soil around and ahead of the shield face. The continuous shield advance is modeled using the remeshing technique. This model has been used to analyze the N-2 tunnel project constructed in 1981 in San Francisco, California

Experimental and Numerical Studies of Square Footing on Weak Clay Stabilized with Geosynthetics-Reinforced Granular Replacement

This paper presents experimentally and numerically the bearing capacity and settlementcharacteristics of shallow footings rested on geogrid reinforced crushed limestone over weakclay soil. The effects of thickness of the crushed limestone, the depth and types of geogrid onbearing capacity and settlement characteristics of reinforced soil foundation (RSF) areinvestigated in laboratory, whereas numerical simulations are used to study the reinforcementfoundationinteraction. Test results indicate that the footing performance could be appreciablyimproved by the inclusion of layer of geogrid leading to an economic design of the footing.However, the efficiency of RSF system is dependent on reinforcement parameters. A closeagreement between the experimental and numerical trend lines is observed. Based on thenumerical and experimental results, critical values of geogrid parameters for maximumreinforcing effect are established

Effect of Welding on Lateral-Torsional Buckling Resistance of I-Shaped Built-up Steel

An experimental investigation was made of the inelastic lateral-torsional buckling of built-up steel I-beams. All beams were carefully fabricated with controlled levels of initial crookedness. Nineteen beams were tested in five groups under same loading conditions with two points load applied at the top flange. The results confirmed that built-up beams of intermediate slenderness with fillet welds on one side of the web are sometimes stronger than their counterpart beams with fillet welds on both sides of the web. It was found that design loads predicted by the Australian Standard provided good lower bounds estimates to failure loads of the tested beams

Evaluating the Performance of Geosynthetic Reinforced Soil-Integrated Bridge System (GRS-IBS) under Working Stress Condition

This paper evaluates the performance of geosynthetic reinforced soil-Integrated Bridge System (GRS-IBS) in terms of lateral facing deformation and strain distribution along geosynthetics. Simulations were conducted using 2D PLAXIS program. The hardening model proposed by Schanz et al. [1] was used to simulate the behavior of backfill material; the backfill-reinforcement interface was simulated using Mohr-Coulomb model, and the reinforcement and facing block were simulated using linear elastic models. The numerical model was verified using the results of a case study conducted at Maree Michel GRS-IBS, Louisiana. Parametric study was carried out to investigate the effects of span length, reinforcement spacing, and reinforcement stiffness on the performance of GRS-IBS. The results indicate that span length have significant impact on strain distribution along geosynthetics and lateral facing deformation. The reinforcement stiffness has significant impact on the GRS-IBS behavior up to a certain point, beyond which the effect tends to decrease contradictory to reinforcement spacing that has a consistent relationship between the GRS-IBS behavior and reinforcement spacing. The results also indicate that reinforcement spacing has higher influence on the lateral facing deformation than the reinforcement stiffness for the same reinforcement strength/spacing ratio (Tf/Sv) due to the composite behavior of closely reinforcement spacing

Update the Pile Design by CPT Software to Incorporate Newly Developed Pile-CPT Methods and Other Design Features

Code LTRC Project Number: 17-2GT SIO Number: DOTLT1000165This study presents the performance evaluation of 21 direct pile-CPT methods for estimating the ultimate load carrying capacity of square precast prestressed concrete (PPC) piles driven into Louisiana soils utilizing the cone penetration test (CPT) data. The investigated methods are: Schmertmann, De Ruiter and Beringen, Bustamante and Gianeselli (LCPC), Philipponnat, Price and Wardle, Zhou, Tumay and Fakhroo, UF (2007), probabilistic, Aoki and De Alencar, Penpile, NGI, ICP, UWA, CPT2000, Fugro, Purdue, German, Eurocode7, ERTC3, and Togliani direct pile-CPT methods. A search was conducted in the DOTD files to identify pile load test reports with CPT soundings adjacent to test piles. A database of 80 pile load tests that were loaded to failure, were identified, collected, and used in analysis. The measured ultimate load carrying capacity for each pile was interpreted from the pile load test using the Davisson and modified Davisson interpretation methods. The ultimate pile capacities estimated from the pile-CPT methods were compared with the measured ultimate pile capacities. In this study, three approaches were adopted to evaluate the performance of pile-CPT methods. In the first approach, three statistical criteria were used: the best fit line of predicted (Qp) versus measured (Qm) capacity, arithmetic mean and standard deviation of Qp\u2044Qm, and the cumulative probability of Qp\u2044Qm. The results of this evaluation showed the following best-performed pile-CPT methods in order: LCPC, ERTC3, Probabilistic, UF, Philipponnat, De Ruiter and Beringen, CPT2000, UWA, and Schmertmann methods. The second approach used to evaluate the 21 pile-CPT methods is the MultiDimensional Unfolding (MDU), which showed similar ranking of top-performed pile-CPT methods. The third approach used for evaluating the pile-CPT methods was based on LRFD reliability analysis in terms of resistance factor and efficiency, and the results of evaluation are consistent with the previous two criteria

Regressive approach for predicting bearing capacity of bored piles from cone penetration test data

© 2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. In this study, the least square support vector machine (LSSVM) algorithm was applied to predicting the bearing capacity of bored piles embedded in sand and mixed soils. Pile geometry and cone penetration test (CPT) results were used as input variables for prediction of pile bearing capacity. The data used were collected from the existing literature and consisted of 50 case records. The application of LSSVM was carried out by dividing the data into three sets: a training set for learning the problem and obtaining a relationship between input variables and pile bearing capacity, and testing and validation sets for evaluation of the predictive and generalization ability of the obtained relationship. The predictions of pile bearing capacity by LSSVM were evaluated by comparing with experimental data and with those by traditional CPT-based methods and the gene expression programming (GEP) model. It was found that the LSSVM performs well with coefficient of determination, mean, and standard deviation equivalent to 0.99, 1.03, and 0.08, respectively, for the testing set, and 1, 1.04, and 0.11, respectively, for the validation set. The low values of the calculated mean squared error and mean absolute error indicated that the LSSVM was accurate in predicting the pile bearing capacity. The results of comparison also showed that the proposed algorithm predicted the pile bearing capacity more accurately than the traditional methods including the GEP model

Relation of gallbladder function and Helicobacter pylori infection to gastric mucosa inflammation in patients with symptomatic cholecystolithiasis

Background. Inflammatory alterations of the gastric mucosa are commonly caused by Helicobacter pylori (Hp) infection in patients with symptomatic gallstone disease. However, the additional pathogenetic role of an impaired gallbladder function leading to an increased alkaline duodenogastric reflux is controversially discussed. Aim:To investigate the relation of gallbladder function and Hp infection to gastric mucosa inflammation in patients with symptomatic gallstones prior to cholecystectomy. Patients: Seventy-three patients with symptomatic gallstones were studied by endoscopy and Hp testing. Methods: Gastritis classification was performed according to the updated Sydney System and gallbladder function was determined by total lipid concentration of gallbladder bile collected during mainly laparoscopic cholecystectomy. Results: Fifteen patients revealed no, 39 patients mild, and 19 moderate to marked gastritis. No significant differences for bile salts, phospholipids, cholesterol, or total lipids in gallbladder bile were found between these three groups of patients. However, while only 1 out of 54 (< 2%) patients with mild or no gastritis was found histologically positive for Hp, this infection could be detected in 14 (74%) out of 19 patients with moderate to marked gastritis. Conclusion: Moderate to marked gastric mucosa inflammation in gallstone patients is mainly caused by Hp infection, whereas gallbladder function is not related to the degree of gastritis. Thus, an increased alkaline duodenogastric reflux in gallstone patients seems to be of limited pathophysiological relevance. Copyright (c) 2006 S. Karger AG, Basel

Gallbladder adenocarcinoma with human chorionic gonadotropin: a case report and review of literature

<p>Abstract</p> <p>Background</p> <p>The case of adenocarcinoma with human chorionic gonadtropin (HCG), primary in the male gallbladder, is extremely rare. A Medline search has shown only a few similar cases reported.</p> <p>Methods</p> <p>We herein describe a case of primary gallbladder adenocarcinoma associated by ectopic HCG positive tumor cells in a 79-year-old male.</p> <p>Results</p> <p>Pathological examination showed a mixture of moderately and poorly differentiated adenocarcinoma with ectopic HCG and placental alkaline phosphatase (PlAP) in tumor cells, though the increase of serum or urinary HCG secretion was not confirmed. The literatures were also reviewed.</p> <p>Conclusions</p> <p>A case of gallbladder cancer with ectopic HCG production is quite rare in the literature, though many similar cases in other site, especially in GI tract, are reported. Embryological consideration suggests the increased frequency of similar cases more than being thought now.</p