الفهرس 
CHAPTER (1): INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Rigid pavements are constructed at taxiways, runways and aprons of many
airports around the world. Many computer response models that are based on the finite
element method have been developed for the analysis of rigid pavement slabs.
However, important considerations were overlooked.
This thesis investigates the performance of reinforced rigid pavement under
aircraft impact load by using experimental and numerical works. Analyses on computer
models of different rigid pavement airport surfaces were performed using the finite
element method (ABQUS). Experimental work is conducted in the laboratory of
resistance testing materials in Civil Engineering Department, Faculty of Engineering,
Menoufiya University.
Impact load is one of the most dangerous dynamic loads, which can affect rigid
pavements. Hence, there is an accelerating interest for researchers to understand the
behavior of different rigid pavements under impact loading in order to provide design
methods that can withstand this load condition. In this thesis, models simulating
weight of big aircraft (impact load) and dimensions of slabs for rigid pavement in
runways and aprons in Egyptian airports are made using suitable scales. The big
aircraft for Egyptian airports are B777-400ER, B747-800, A380-800 and An-
225Mriya. Impact load equal to 13.75 kg for the experimental program that represent
scale 1:36000 was used. For the experimental program, actual airfield slabs of
dimensions (1200*1200*50) mm were represented by scale 1:5. Three cases were
used in the experimental program:
1. Case I: R.C slabs resting on soil that represent base and sub base coarse. (Normal
case).
2. Case II: R.C slabs tested as simple supports without soil. (Worst case).
3. Case III: Testing the cracked R.C slabs of case II (worst case) after repair.
For each case, 15 R.C slabs are casted and tested with various meshes (Tensar,
Tenax, Gavazzi, Welded, and Expanded mesh). Hence, the experimental program
focuses on this type of slabs as well as the change in their behavior whenever reinforced
by welded, Tenax, Tensar, and expanded mesh. The effect of using these materials on
the structural performance of the proposed rigid pavement slabs are illustrated and
discussed in terms of deformation characteristics, cracks, and number of blows to begin
cracks of slab. Almost, all cracked slabs have the same part of failuare at the middle of
the slabs about (500*500*10) mm. The failure part of slabs with the same
reinforcement. The failure part of slabs repaired with Tensar mesh.
The current work shows a 3D finite element model developed by ABAQUS to
investigate dynamic behavior of rigid pavement slabs under impact load (aircraft
load).
The finite element program includes boundary elements and testing of Ferrocement
slabs. ABQUS is the finite element program used in this thesis. The present
thesis analyzes 30 R.C slabs under impact load using ABQUS program for case I and
II in addition to using a different parametric study for slabs in case II loaded maximum
energy. The dimensions of different parametric study slabs are (500*500*25) cm
under impact load as the popular and maximum weight type used for aircraft in Egypt
Air group (Boeing 737-800). The current dimensions for theoretical work (base, sub
base and subgrade) are 30cm, 50 cm and 200cm respectively.
Experimental and numerical results are compared and conclusions and results
are presented. Using Tenax and Tensar mesh enhance the behavior of rigid pavements
under aircraft loads.
Based on the experimental/ numerical results in the current study, various
conclusions may be drawn:
1. Tenax and tenser mesh enhance the performance of R.C slabs under impact load
of aircraft.2. Using slag as aggregate with various mesh types lead to a higher withstand to
failure.
3. The lowest displacement under the impact load of aircraft is achieved using
Tenax and tenser mesh.
4. The worst case of deflections and damaged area occurs when using slab without
reinforcement.
5. Finite element analysis used in ABAQUS software is able of development and
realistic estimations available to the possible damage modes of rigid pavement
slabs under impact loads of aircraft. Finite element model results predicted
good work with those previously published regarding shape of failure,
maximum deflection at mid-point of slab and reaction force.
Further studies are recommended to enhance the understanding of this vital
topic. The following studies could be suggested for future research:
1. An economic study on the proposed system of experimental work in this thesis.
2. Studying sustainability for experimental works in this thesis.
3. Studying several finite element programs and comparing their results.
4. Studying another factors as temperature, impact aircraft loads, …..etc on rigid
pavements performance.
5. Studying ferro-cement for flexible and composite pavement in airports.
General Future studies could be performed:
1. Additional work is needed to study the combined nonlinear thermal gradient and
different wheel loads configuration on those parameters. The effect of material nonlinearity
or contact-modeling technique would influence the model responses.
2. Under repeated cycles of loading and unloading due to repetitive traffic loading
or multiple thermal cycles were not considered.
3. Because of cycles of tension-compression, concrete slabs undergo cracks and
fatigue damage. In FAAFIELD and ICAO design method, the concept of cumulative damage factor replaces the design aircraft concept. The contribution
of each airplane in a given traffic mix to total damage is separately analyzed.
Additional work is required to investigate the response of airfield pavement
subjected to different wheel configurations combining thermal gradient cycles
and its effect on fatigue damage in rigid pavement slabs.
4. Further research is needed to identify a more realistic approximation for the
friction coefficient assumed at the sliding interface between the dowel bars and
the concrete slab and how it changes along the pavement life.
5. The properties of materials were chosen as not dependent on time and
temperature. Hence, early-age behavior cannot be simulated with this choice of
parameters; temperature-dependent data can require adjusting the outcomes of
the current analysis.
6. A sensitivity study is required to study different sub-grade modeling techniques
in term of accuracy and convergence time.