Numerical study of the use of Non-destructive Impact Test methods for the exam of integrity of concrete piles

This research includes a numerical study using Finite Element Method aims to evaluate the ability and accuracy of using Non-destructive Impact Response Method in the assessment of length and cross-sections of intact concrete pile (not deformed) in both time and frequency domains. Therefore, an appropriate numerical model depends on the modeling of both impact force (impulsive load) and distributing medium (pile + soil) and insert them in computing software ABAQUS was carried out. The numerical model was verified corresponding to field measures obtained from literature review and the results showed good agreement between measures and numerical results. Furthermore, the model was applied on a typical example in order to study vibration distribution in the pile due to impulsive load applied on pile top. Mechanical response curve of intact pile was obtained. Then, both of length and cross-section area of the pile were determined. Finally, parametrical study of most important factors (stiffness of soil surrounding the pile and length of pile embedded in the soil) effect on vibration distribution resulted from impulsive load applied on pile top. The parametrical study was carried out in two domains; first one was time domain depending on the direct analysis of particle displacement and velocity and the second was frequency domain depending on analysis of pile mechanical response curve. The results of this research enables to use the proposed numerical model to numerically obtain the time history of particle displacement and velocity in addition to the curve of mechanical response computed in the pile top and forms reference diagrams which is used later to compare with similar diagrams resulted from field test of executed piles. As a result, pile integrity test and detecting of defects in the piles if any. In addition, the limits of the use of both analysis methods adapted in research and choose the best between them according to the case study.

Effect of FRC Posts Surface Treatment on The Retention of A Composite Resin (In vitro study)

Background and Aim : Retention between composite and fiber post is still below the acceptable level when compared with the retention between composite and dental structure. This study aimed to evaluate the effect of H2O2 as a chemical solution to improve the mechanical connection between fiber post and composite core. Materials and Methods:45 glass fiber posts and 45 quartz fiber posts were prepared. The specimens were randomly distributed into 3 subgroups, including application of silane (S) , etching with H2O2 10% for 20 minutes(H1) , etching with H2O2 20% for 10 minutes (H2). composite core was placed. Shear bond strength values of posts and composite resin cores were measured using a mechanical test machine (Instron). data were analyzed Statistically . Results :There were significant differences between the shear bond strength for (H1,H2) And (S) in quartz groups only (P<0.05). There was no significant difference between glass and quartz groups (P>0.05). Conclusions:The surface treatment of quartz fiber posts with H2O2 significantly enhanced the shear bond strength of the composite core. Application of H2O2 to the Glass fiber post surfaces was not effective.

Using Numerical Modeling in a Parametric Study of Pile Load Tests

A parametric study of pile load test requires a numerical modeling of this test and a study of the effect of each parameter of the material model used on pile load settlement curve shape and on the extrapolated value of pile ultimate bearing capacity. Some real pile load tests are numerically modeled and calibrated using two types of material models: Mohr-coulomb MC and Hardening soil HS. The obtained results from HS are better than those obtained from MC, so material model HS is adopted to generate pile load settlement curves. It is shown that the relation between the extrapolated value of pile ultimate bearing capacity and each parameter of the material model used is linear, and there is only one value for each parameter of HS in which the calculated value of bearing capacity identifies with the normal value in DIN-Code. The main economic benefit obtained from this research is the ability of generating pile load settlement curves in addition to doing a parametric study using a numerical modeling method without any need to do pile load field tests. The practical scientific aim is to accumulate and collect information that can be used as a database for static pile load tests.

Analytical comparative study of load tests on driven piles in sandy soils

This research represents a trial to establish a primary database of load tests applied on concrete driven piles embedded in sandy soils. This research depended on analyzing and evaluating a large number of available load test curves of driven piles. The variation of pile ultimate bearing capacity value is studied according to several parameters such as (relative density of sand, embedded length of pile and pile diameter). Depending on the obtained results a primary approximate relationship is suggested to calculate the ultimate bearing capacity of driven piles in sand. Then, a comparison is made between the suggested method and the other analytical calculation methods and also, with the obtained results from an available international codes of practice in America, Russia and Germany. The approximate relationship introduces a simple and easy method to calculate the bearing capacity of concrete driven piles in sands. Also, This suggested method may be considered as an introduction to developing the researches to include different kinds of soils.