Mihai Dicu, Andreea Matei and Constantin Dorinel Voiniţchi
The paper follows the potential practice of fiber reinforced concrete (FRC) as a solution for airport`s runway pavements, in order to increase the bearing strength, resulting in decreasing the height of the concrete layer that is currently used.
Experimentally, the study focuses on the properties of fiber reinforced Portland cement concrete using 3 different percentages (0.5%, 1% and 1.5% of the concrete volume) and 4 different types of fiber (for 1% percentage – hooked steel fiber 50 mm length, hooked steel fiber 30 mm length, crimped steel fiber 30 mm length and polypropylene fiber 50 mm lenght), using as reference a plain concrete with 5 MPa flexural strength.
More exactly, the study presents the change in compressive and flexural strength, shrinkage, thermal expansion factor, elastic modulus and Poisson`s ratio over fiber type and dosage.
For the highest performance concrete (7 MPa flexural strength), it has been made a study using two methods for rigid airport pavements design (general method and optimized method), and one method for evaluation of bearing strength (ACN – PCN method), which is compared to a plain 5 MPa concrete. Furthermore, the decrease in the slab`s thickness proportionally to the growth of the flexural strength is emphasized by evaluating the slab`s height for a high performance 9 MPa concrete using both design methods.
This paper aims to establish the interface conditions influence on the flexible pavement structures life. The methodology consists in using the interface constitutive model available in the Alizé calculation program to calculate the stresses and strains in the flexible pavement structures.
The design criteria related to limiting fatigue cracking of asphalt layers and permanent deformations at the subgrade level from the road bed are used to estimate the flexible pavement structures lifetime.
When calculating the critical stresses and strains, most mechanical design methods of the flexible pavement structures considers that the road layers at interfaces are perfect bonded or total unbonded.
Proper modeling of the interface binding condition is an important aspect in understanding the real behaviour of in-service flexible pavement structures.
Arch bridges were the first constructions with considerable spans built by man, due to the materials and technologies available at that time. Afterwards, these works of art have diversified and are now solutions used in countless situations, especially when crossing deep valleys.
Both their economic and architectonic aspects are hard to combat and have led to selecting this type of structure for more and more locations.
The paper will contain a brief presentation of some aspects regarding upper path concrete arch bridges composition and design methods. Also, it will have a case study regarding structural stresses over the different construction stages, and for several support hypotheses.
The case study will reflect the Crivadia viaduct, situated on DN 66, at km 150+672. The bridge has a main span of 59.20m and an overall height of 15.00m, serving a 7.80m wide carriageway and two 2.20m wide footways. It has a total length of 107.60m.
Based on the results of the case study, conclusions will be drawn regarding stress variation over the construction stages and under different support hypothesis, comparing these with the initial results.
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