Riyadh Al-Ameri

A micromechanical biosensor with interdigitated capacitor readout

The growing demands of high-throughput, accurate and fast response biological or chemical sensors are driving the development of new detection technologies. This paper presents a micromechanical biosensor with capacitive read-out method. The proposed biosensor design consists of a fixed-fixed beam attached to an interdigitated capacitor. Implementation of the interdigitated capacitor design improves the sensitivity of the biosensor. The effects of the electrode thickness, length and the number of electrode fingers on the change of capacitance are investigated. The results show that the percentage change of capacitance is proportional to the number of the electrode fingers. Similarly, the increase in the length of the electrodes results in an increase in the percentage change of the capacitance. However, as the thickness of the electrode increases, the percentage change of the capacitance decreases.

EVALUATION OF FRP CONCRETE COMPRESSION MEMBER UNDER REPEATED LOAD AND HARSH ENVIRONMENT

Strengthening and rehabilitation have been increasingly applied in many structures to improve their capacity and serviceability. Fiber Reinforced Polymer (FRP) materials are universally known for their ability to improve the load capacity of damaged structural elements because of their high linear-elastic behavior. However, enhancing the capacity of structural elements that are exposed to repeated load coupled with harsh environment is an area that requires further investigation. This research focused on experimental analysis of the behavior and response of confined and unconfined concrete compression members (300mm x 150mm) under repeated load while exposed to 1440 cycles of seawater splash zone in United Arab Emirates (UAE). Confining concrete compression members with Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP) sheets have increased the load capacity compared to the control sample at room temperature by 110% and 84%, respectively. Results showed that the average value of compressive strength for the confined concrete exposed to sea water splash zone conditions for CFRP and GFRP specimens has decreased by 33% and 23%, respectively, compared to the confined concrete in the room temperature. However, GFRP specimens showed higher performance in compressive strength under sea water splash zone than those of the CFRP specimens. Different mode of failures such as delamination, de- bonding and combination of such modes were observed and related to various exposure factors and mechanical properties.

Mechanistic behavior of open and dense graded unbound granular materials under traffic loads

The absence of abundant amount of natural unbound granular materials (UGMs) necessitates investigating alternatives such as processed crushed rock. Extensive use of crushed rock in pavement design requires proper modification of characterization, design and construction practices. Many specifications and standards require adopting of dense gradation of base materials. Although dense gradation has a high dry density, it also has low permeability or voids. This low permeability results in a decrease in material strength when the pavement is exposed to moisture. This research examines the effects of fines content on mechanistic behaviors of UGMs, particularly resilient modulus (Mr) and permanent deformation (PD) using repeated load triaxial test (RLTT). Class 2 crushed rock is used in two gradationsdense gradation and open gradation. Results from RLTT show that open graded Class 2 has an acceptable PD resistance under repeated loads for test’s Stages 1, 2 and 3 followed by a significant collapse at Stage 4 as per Australian pavement design guide. This investigation has found that open graded Class 2 has higher Mr than dense graded Class 2. This paper suggests that open graded Class 2 could be used as a porous base material for roads with low traffic volumes.

Evaluation of the mechanical performance of short concrete column confined with CFRP and GFRP

Concrete has been successfully used to build strong and economic structures. However severe environmental exposures slowly deteriorate concrete strength until complete failure reducing its designed service life. Fiber Reinforced Polymer “FRP” has been recently introduced in the construction industry to strengthen and retrofitting several structural elements including columns. In this research two types of FRP have been used to wrap concrete column in order to increase its capacity; these are Carbon Fiber Reinforced Polymer “CFRP” and Glass Fiber Reinforced Polymer “GFRP”. Twelve short concrete columns have been wrapped with one and two FRP layers including CFRP and GFRP to evaluate their mechanical performance. Mechanical testing has shown that, in general, concrete columns wrapped with FRP produced higher modulus of elasticity compared to the control sample. Results showed that one layer of CFRP have 85.8% increases where as one layer of GFRP showed an increase of 64.5%. Furthermore, two layers of CFRP and GFRP showed 112.5% and 77.2% increase respectively.