Pavement Design

Saudia Aerospace Engineering Industries Aircraft Maintenance Hangars, Jeddah 7Information Document Revision 1 24 June 2011

3. PAVEMENT DESIGN

3.1 INTRODUCTION

Volume 2 Exhibit D Special Specifications Part DI Employers Requirementsdetails the following salient consideration for the airfield pavements:

1. The pavement design for the various airfield elements shall comply with theFederal Aviation Administration FAA standards and proposed practices.

2. For flexible pavement type - layered flexible pavement shall be consideredincluding the following exclusive succession of layers from top to bottom:bituminous concrete surface course, tack coat, bituminous base course,prime coat, unbound crushed aggregate base and/or aggregate sub-basecourses, compacted subgrade, and natural subgrade etc.

3. For rigid pavement - jointed plain concrete pavement (JPCP) shall beconsidered with adequately spaced contraction joints, while using dowelbars for load transfer across joints (it is assumed that dowelling is only inone direction). Jointed reinforced concrete pavement (JRCP) shall be usedonly when odd shaped slabs are encountered. For the rigid Jointed PlainConcrete Pavement, layered rigid pavement shall be considered includingthe following exclusive succession of layers from top to bottom: PortlandCement Concrete Slab, cement or asphalt treated base course, unboundcrushed aggregate base and/or aggregate subbase courses, compactedsub-grade, and natural sub-grade.

4. The properties of the subgrade soil shall be studied in order to determinethe corresponding subgrade soil design parameters (CBR, Modulus ofElasticity, Modulus of subgrade reaction, etc.).

5. The airfield fleet mix using KAIA shall be analyzed and generated for thedesign life, taking into account the annual growth in air traffic.

6. The distribution of the aircraft loading around the various zones of theairport and consequently the anticipated load on each airfield element shallbe determined separately.

7. The airfield pavement design shall be carried out using the latest state-of-the-art computer programs (software) that cater for the large body aircraftwheel configuration such as the A380, A340, B777, B747, AN225, etc. andthat can account for the wander effect in order to optimize the resultingpavement thicknesses. Fatigue equations shall conform to therequirements of the US Corps of Engineers for asphalt concrete andgranular materials and subgrade and to those of the Portland CementAssociation for cement concrete.

8. The pavement design of shoulder shall be checked to accommodateoccasional passages of critical aircrafts considered in pavement design andthe critical axle load of emergency or maintenance vehicles which maypass over the area, according to the International standards.


3.2 BASIS OF DESIGN

3.2.1 Overview

The pavement design for the aircraft pavements associated with the developmentof the Saudi Aerospace Engineering Industries Aircraft Maintenance Hangars,Jeddah - individual hangar pavements, external apron, Taxiway MA and TaxilaneLB, has considered a range of factors including:

The existing site conditions

Existing subsoil conditions

Proposed operating conditions

Current and proposed aircraft types

Aircraft wheel and body jacks

Aircraft tugs

Emergency service vehicles

Concrete strength

This report presents a summary of the key assumptions and input data used todevelop the designs for the individual hangar pavements, external apron,Taxiway MA and Taxilane LB in terms of:

Aircraft loads

Aircraft tug loads and operating frequency

Aircraft jacking operations

Frequency of operations

Subsoil strength

Concrete strength (for rigid) pavements

Emergency service vehicle loads and operating frequency

A number of design scenarios have been considered in developing the pavementthicknesses. These design scenarios were undertaken to test the sensitivity ofthe pavement thickness for both rigid and flexible pavements to variations in thedesign assumptions in terms of:

Frequency of aircraft operations

Frequency of jacking operations

Subsoil strength


The results of the individual analyses are summarized in this report, whilecomplete details are included in Appendices C and D.

3.2.2 Pavement Types

Flexible Pavements

Flexible pavements generally consist of a dense, hot mix asphalt surfacingplaced on an unbound crushed aggregate base and/or aggregate sub-basecourses), and the pavement is then supported by the subgrade. The design forSaudi Aerospace Engineering Industries Aircraft Maintenance Hangars is beingcarried out using the U.S. Department of Transportation Federal AviationAdministration (FAA) design program FAARFIELD, used in conjunction with theFAA Advisory Circular (AC) 150/5320-6E. This AC includes guidelinerequirements for the various materials for the pavement layers. Where the ACrequires engineering judgement regarding the material to be used this is detailedand justification for the choices made is given.

For flexible pavement design, FAARFIELD uses the maximum vertical strain atthe top of the subgrade and the maximum horizontal strain at the bottom of theasphalt surface layer as the predictors of pavement structural life. FAARFIELDprovides the required thickness for all individual layers of flexible pavement (inthis case surface, base and sub-base) needed to support a given aircraft trafficmix over a particular subgrade for the given design period.

Rigid Pavements

The basic composition of an airfield rigid pavement is a Portland cement concrete,PCC (which is often referred to as Pavement Quality Concrete PQC), on agranular or stabilised sub-base supported on the in-situ subgrade after suitablecompaction. The purpose of a base course under a rigid pavement is to provideuniform stable support for the pavement slabs, and support across the joints. Aminimum thickness of 100mm of base is required under all rigid pavements.According to FAA, stabilized materials are required for a base course under rigidpavements serving airplanes weighing 45,359kg or more to improve load transferacross joint lines and reduce pumping type erosion effects due to flexure of theslabs at the joint lines.

For rigid pavement design, FAARFIELD uses the maximum horizontal stress atthe bottom edge of the PQC slab as the predictor of pavement structural life. Themaximum horizontal stress for design is determined using an edge loadingcondition with approximately 30% load transfer to the adjacent slab.

Once load transfer exceeds 40% across a joint line the interior thickness of theslab then becomes the critical element. Localised thickened edges are requiredat transitions from concrete to asphaltic surfacing or at box outs for manholes,service pit, grated drains, etc. FAARFIELD provides the required thickness of therigid pavement slab needed to support a given aircraft traffic mix over a particularsubgrade/base course for the given design period. The life of the concretesurfacing is very sensitive to changes in slab thickness, and the stiffness of theimmediate supporting layer.


The required thickness of concrete pavement is related to the strength of theconcrete used for construction of the pavement. For airfield pavement design, thestrength of the concrete is characterized by the flexural strength (since theprimary action and failure mode of a concrete pavement is in flexure), rather thanthe more commonly used unconfined crushing strength tests (UCS) associatedwith building works.

The construction of rigid pavements will be done in slabs which are as square aspossible, and with joints spaced to minimize the warping stresses that occur dueto variations in temperature and moisture. These joints also act to minimizerandom cracking. Slab thickness relates to joint spacing with slabs typically beingjointed at between 4.5 and 5.0m (slab size is a ratio of typically 12-15 times theslab thickness).

In the direction of paving, joints will be saw-cut across the paving lane when theconcrete has reached sufficient strength (contraction joints). This will act toinduce cracking of the pavement at these locations. In the transverse direction,joints will be dowelled to ensure effective load transfer across the joints (dowelledconstruction joints).

Pavement Joints

Pavement joints and transitions are of particular importance in a successfulpavement design, especially for airports where maintenance access is oftendifficult. Areas adjacent to structures (e.g. drainage channels, pits, manholes, etc.)can be subject to differential settlement issues and these need to be designedout where possible. Transitions from rigid to flexible pavement are also acommon area of concern. Our design addresses such issues by presenting ourdetailed jointing and transition details.

3.2.3 Aircraft Types and Masses

The range of aircraft assumed to be accessing the aircraft maintenance facilityand individual hangars are summarised in Table 3.1. The aircraft mix assumed inthe initial pavement designs was based on the information contained in theTender Documents. Specifically, Drawings PD-APR-TR-005, PD-APR-TR-006,PD-GD-A-003 and PD-G-AD-100 to 103 indicated a range of aircraft types in theeach hangar.

Following a tender query, Notice to Tenderers No 11 provided the followingclarification in relation to aircraft types:

The intent is to service the combination of aircraft shown in each hangar. Thedesign is driven by limitations in adjustability of work docks between aircraft types.

1. Line maintenance hangars shall receive all types of aircrafts.

2. Wide body heavy maintenance hangars shall be designed to receive allwide body aircrafts except the A380.

3. Narrow body heavy maintenance hangars shall be designed to receive allnarrow body aircrafts.


4. A380 heavy maintenance hangars shall be designed to received A380aircrafts.

5. Wide body paint and wash hangars shall be designed to receive all wideand narrow body aircrafts except the A380.

6. A380 paint and wash hangars shall be designed to receive all types ofaircrafts.

The pavement thickness designs as presented in subsequent sections are basedon the aircraft indicated in Table 3.1.

The design criteria for the pavements associated with the aircraft maintenancefacility is based on the aircraft at operating empty weight (OEW) with provision forvarying amounts of fuel.

The internal pavements of the paint hangars, wash hangars and heavymaintenance hangars are based on operating empty weight (OEW) + 10%fuel.

The internal pavements of the line maintenance hangars are based onoperating empty weight (OEW) + 50% fuel.

The aircraft parking apron is based on the aircraft arriving at themaintenance facility at operating empty weight + 50% fuel, prior to beingde-fuelled and moved into the hangars.

Departing aircraft are assumed to be at operating empty weight + 50% fuelfollowing refuelling.

Table 3.2 provides a summary of a range of masses for individual aircraft.


3.2.4 Aircraft Jacking Operations and Movements

The initial pavement designs were based on a range of assumptions regardingthe frequency of aircraft jacking in each of the hangars.

Following a tender query, Notice to Tenderers No 11 provided the followingclarification in relation to aircraft jacking frequency:

Line maintenance is unscheduled. The hangar is likely to be in use 24 hours aday and for minor overnight repairs and for RON positions in poor weather. It is tosupport typical line maintenance activity.

Heavy maintenance hangars are expected to be fully occupies with aircraft in Cand D checks. As such, aircraft are likely to be in the narrow hangars for 20-40days and in the widebody hangars for 30-45 days. Assume a regular cycle ofaircraft in and out of each hangar bay on that schedule.

Aircraft will be in the paint hangar for approximately 6 days, and assume aregular cycle of aircraft in and out of that hangar on the schedule. The washhangar is less regularly scheduled, but assume it is used daily. The designers areassumed to know the normal operations of MRO facilities for the line and heavymaintenance.

Aircraft Wash Hangars

The previous pavement designs assumed two (2) aircraft per day througheach of the wash hangars Wash Hangar 1 (A380-800 only), WashHangar 2 (B747-400 only).

Based on the clarifications in Notice to Tenderers No 11, the pavementshave been designed for all aircraft types indicated in Table 3.1 at afrequency of two (2) aircraft per day through each of the wash hangars.

The number of annual movements are summarised in Table 3.3.

No body jacking is assumed in the wash hangars.

No wheel jacking is assumed in the wash hangars.

Aircraft Paint Hangars

The previous pavement designs assumed one (1) aircraft per monththrough each of the paint hangars Paint Hangar 1 (B747-400 only), PaintHangar 2 (A380-800 only).

Based on the clarifications in Notice to Tenderers No 11, the pavementshave been designed for all aircraft types indicated in Table 3.1 at afrequency of one (1) aircraft every six (6) days through each of the painthangars.


No body jacking is assumed in the paint hangars.


No wheel jacking is assumed in the paint hangars.

Heavy Maintenance Hangar No 1 (A380)

The previous pavement designs assumed two (2) aircraft per week werebeing jacked in the hangar.

Based on the clarifications in Notice to Tenderers No 11, the pavementshave been redesigned for all aircraft types indicated in Table 3.1 at thefollowing a frequencies:

- Body jacking operations are based on one (1) aircraft being jackedper month or 12 annual jacking operations.

- Wheel jacking operations are based on one (1) jacking operation perlanding gear assembly per month or 12 annual wheel jackingoperations.

Heavy Maintenance Hangar No 2 & 3 (Narrow Body including B757)



- Body jacking operations are based on one (1) aircraft being jackedever three (3) weeks or 18 annual jacking operations.

- Wheel jacking operations are based on one (1) jacking operation perlanding gear assembly every three (3) weeks or 18 annual wheeljacking operations.

Heavy Maintenance Hangar No 4, 5, 6 & 7 (Narrow Body excluding B757)



- Body jacking operations are based on one (1) aircraft being jackedever three (3) weeks or 18 annual jacking operations.

- Wheel jacking operations are based on one (1) jacking operation perlanding gear assembly every three (3) weeks or 18 annual wheeljacking operations.


Heavy Maintenance Hangar No 8, 9, 10,11 & 12 (Wide Body)



- Body jacking operations are based on one (1) aircraft being jackedper month or 12 annual jacking operations.

- Wheel jacking operations are based on one (1) jacking operation perlanding gear assembly per month or 12 annual wheel jackingoperations.

Line Maintenance Hangars

The previous pavement designs assumed four (4) aircraft per day througheach of the line maintenance hangar positions Line Maintenance hangar1 (A380-800/B747-400), Line Maintenance Hangar 2 (B747-400 only).

Based on the clarifications in Notice to Tenderers No 11, the pavementshave been redesigned for all aircraft types indicated in Table 3.1 at afrequency of four (4) aircraft per day through each of the maintenancehangar positions.


No body jacking is assumed in the line maintenance hangars.

Wheel jacking operations are based on one (1) jacking operation perlanding gear assembly per day or 365 annual wheel jacking operations.

Table 3.3 Aircraft Jacking Operations

Wash Hangar 1 - - 730

Wash Hangar 2 - - 730

Paint Hangar 1 - - 61

Paint Hangar 2 - - 61

Heavy Maintenance Hangar 1 12 12 12









Table 3.3 Aircraft Jacking Operations (cont.)





Line Maintenance Hangar 1 - 365 1,460

Line Maintenance Hangar 2 - 365 1,460

Note: One aircraft operating in and out of the hangar is equivalent to two movementsfor the purposes of pavement design.

3.2.5 Aircraft Jacks

Body Jacks

Two types of body jacks have been adopted, these being inner main wing jacksand remainder of fuselage and outer wing jacks. All jacks are assumed to bepneumatic tripod jacks with circular base plates. The following jack details havebeen assumed in the development of the pavement design for the hangars:

Main wing jacks assumed base plate diameter = 300mm

Forward fuselage jack - assumed base plate dimension = 300mm

Rear fuselage jack assumed base plate dimension = 300mm

Reminder of jack positions assumed base plate diameter = 300mm

Wheel Jacks

For all wide body aircraft, the wheel jacks have been assumed as 225mm x450mm for the main landing gear and nose landing gear.

For all narrow body aircraft, the wheel jacks have been assumed as 200mm x450mm for the main landing gear and 125mm x 300mm for the nose landing gear.

3.2.6 Aircraft Jacking Loads

The basis of the individual aircraft body and wheel jacking loads is based onadopting relevant information from aircraft facility manuals and other referencedocumentation where possible (Appendix A). For body jacking the maximumloads have been adopted. Body jacking loads are summarised in Table 3.4.


Table 3.4 Aircraft Body Jacking Loads

A318 6,800 6,000 33,400 n/a n/a

A319 6,800 2,000 33,400 n/a n/a

A320-100 6,800 2,000 33,400 n/a n/a

A320-200 6,800 2,000 33,400 n/a n/a

A321-100 6,800 2,000 33,400 n/a n/a

A321-200 6,800 2,000 33,400 n/a n/a

A330-200 11,135 4,500 73,446 n/a n/a

A330-300 11,135 4,500 73,446 n/a n/a

A340-200 12,300 4,500 80,982 n/a n/a

A340-300 12,300 4,500 81,084 n/a n/a

A340-500 18,000 9,000 96,000 n/a n/a

A340-600 18,000 9,000 96,000 n/a n/a

A350-800 no data no data no data n/a n/a



A380-800 51,000 12,000 190,000 n/a n/a

B737-600 7,900 9,900 31,700 n/a n/a

B737-700 7,900 9,900 31,700 n/a n/a

B737-800 7,900 9,900 31,700 n/a n/a

B737-900 7,900 9,900 31,700 n/a n/a

B737-900ER 7,900 9,900 31,700 n/a n/a

B747-300 17,900 43,900 90,700 13,600 11,300

B747-400 17,900 43,900 90,700 13,600 11,300

B757-200 12,200 1,800 49,200 n/a n/a

B757-300 12,200 1,800 49,200 n/a n/a

B767-200 12,700 30,400 68,000 9,500 n/a

B767-200ER 12,700 30,400 68,000 9,500 n/a

B767-300 12,700 30,400 68,000 9,500 n/a

B767-300ER 12,700 30,400 68,000 9,500 n/a

B767-400ER 12,700 30,400 68,000 9,500 n/a

B777-200 20,400 44,9900 94,300 10,000 7,800

B777-200ER 20,400 44,9900 94,300 10,000 7,800

B777-300 25,900 57,100 119,000 12,700 9,900


Table 3.4 Aircraft Body Jacking Loads (cont.)

B777-300ER 25,900 57,100 119,000 12,700 9,900

B787-9 20,000 37,200 77,600 8,200 5,400

MD-11F 27,800 n/a 109,100 n/a 3,600

The wheel jacking loads have been determined by adopting the proposed aircraftdesign loads, the percentage of the design aircraft mass on the landing gearsand the number of wheel jacking points on the undercarriages of the individualaircraft.

The distribution of the wheel jacking operations has been assumed as distributedas 80% on the main undercarriage (split 50/50 each side) and 20% on the nosewheel.

For aircraft with a centre main landing gear, the distribution of the wheel jackingoperations has been assumed as distributed as 30% on the each of the mainlanding gears, 25% on the centre landing gear and 15% on the nose wheel.

3.2.7 Aircraft Tug

The following tender query has been raised in relation to aircraft tugs, theclarification of which is pending.

In addition to the data on fire tenders and other emergency vehicles (RFI Register No28), additionally we require details of the aircraft tugs likely to be used by SaudiAerospace.

The following data related to the aircraft tug has been assumed for thedevelopment of the pavement design for the hangars pending clarification of thetender query:

Wide Body Aircraft

The assumed operating mass of the tug is 50,000kg.

The assumed operating tyre pressure is 520kPa.

Movements are based on four (4) movements (on average) in and around thehangar per aircraft.

Narrow Body Aircraft

The assumed operating mass of the tug is 30,000kg.

The assumed operating tyre pressure is 520kPa.

Movements are based on four (4) movements (on average) in and around thehangar per aircraft.


3.2.8 Emergency Service Vehicles

The following tender query has been raised in relation to emergency servicesvehicles, the clarification of which is pending.

Please provide details of the fire tenders and other emergency service vehicles currentlyoperating at KAIA.

The following data related to the emergency services vehicles has been assumedfor the development of the pavement design for the hangars pending clarificationof the tender query:

The emergency services vehicle is assumed to be a 6 wheel Panther orsimilar.

The assumed operating mass of the emergency service vehicle is 40,000kg.

The assumed operating tyre pressure is 1,000kPa.

3.2.9 Subgrade Strength

As discussed in Section 2, the pavement design is based on a CBR of 15%. Thesensitivity of pavement thickness to a reduction in the CBR has been assessedwith CBR 10%.

The rigid pavements are designed for a modulus of subgrade reaction, equivalentto CBR 15%. The modulus of subgrade reaction, or k value, can be calculatedapproximately from the CBR value using the equation:

k = (1500 x CBR/26)0.7788

This gives a value in pci (pounds per cubic inch). For the 15% CBR, the k value iscalculated as 194 pci, which converts to 52.4 MN/m3. Similarly, the modulus ofsubgrade reaction equivalent to a CBR of 10% is 38.4 MN/m3.

This report has been prepared on the basis of construction of the fill embankmentto provide a stable, uniform subgrade with an equivalent minimum CBR of 15%.Insitu testing will be required to confirm that such works have been completed asspecified prior to pavement works commencing.

3.2.10 Concrete Strength

The specification (Section 321313) issued with the Tender Documents nominatesa design flexural strength of 4.6 MPa at 28 days.

Load transfer will take place through the provision of dowel bars through thedoweled construction joints and sawn contraction joints.

3.2.11 Design Period

The design period for the pavements (both rigid and flexible) has been assumedas 30 years.


3.3 PAVEMENT DESIGNS

3.3.1 Taxiway MA

Taxiway Pavement

All aircraft entering or leaving the facility will access Taxiway MA, entering theapron initially. Aircraft are assumed to enter the taxiway at OEW + 50% fuel andpark on the apron. Aircraft are assumed to leave the apron (departing themaintenance facility) at OEW + 50% fuel.

The exception to this is the length of taxiway to the paint hangars and washhangars. The aircraft using this portion of the taxiway are assumed to be at OEW+ 10% fuel maximum.

To simplify the analysis at this stage, a uniform pavement thickness is proposedfor Taxiway MA along its length.

The total number of aircraft entering the facility on an annual basis is derivedfrom the annual usage of each of the maintenance hangars annually. Thesesame aircraft are assumed to leave the facility annually.

The previous pavement design proposed a pavement structure of 60mm PMB on60mm Binder Course on 200mm CABC on 250mm CASBC based on theassumptions made at the time.

Based on the clarifications in Notice to Tenderers No 11, the pavements havebeen redesigned. Table 3.5a provides the pavement thickness requirements forvarying subgrade strengths and operational scenarios.

Table 3.5a Taxiway MA Pavement Thickness

Base Case Double Aircraft

CBR 15%

60mm PMB on60mm Binder Course

200mm CABC305mm CASBC



CBR 10%





A pavement structure of 60mm PMB on 60mm Binder Course on 200mm CABCon 350mm CASBC is proposed for Taxiway MA at this time bearing in mind theassumptions being made. This pavement structure would seem to cover a rangeof potential operating scenarios. The proposed pavement extent is indicated onDrawing SK001.

Shoulder Pavement

The shoulder to Taxiway MA is to be designed for occasional aircraft traffic as perthe Employers Requirements, in addition to use by emergency service vehicles.Aircraft are assumed to operate on Taxiway MA at OEW + 50% fuel.

Pavement Design

Documents

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pavement design3

overviewthe pavement

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aircraft pavements

natural subgrade

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