Port Pavement Design Guide

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3780 Kilroy Airport Way, Suite 600, Long Beach, California 90806 (562) 426-9551

DISCLAIMER

This Design Guide was prepared for the sole purpose of providing general information on the

selected subject matters. However, this Design Guide is only intended to provide general

guidance related to container terminals and intermodal rail yard operational areas, and this

information, is not intended for use for any specific project. The use of this Guide for actual

projects should only be done in conjunction with the services of a qualified engineer or

consultant to assure that specific project circumstances are taken into consideration. While all

reasonable care has been taken in the preparation of this Design Guide, Moffatt & Nichol does

not guarantee the correctness of the data or information contained within, and disclaims any

responsibility or liability in connection with its use.

Photographs and drawings of equipment used in this publication are for illustration only and do

not imply preferential endorsement of any particular manufacturer by Moffatt & Nichol andtheir contributors.


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CONTAINERTERMINAL AND INTERMODAL RAIL YARD

OPERATIONAL AREA CONSIDERATION FORPAVEMENT DESIGN

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Executive Summary

Traffic disruptions and the cost associated with rehabilitating and maintaining distressed or failedpavements in container terminals signifies the importance of optimizing pavement design

procedures within these facilities. This pavement design guide aims at providing generalconcepts and instructions on the pavement design of the heavily loaded conditions encounteredin container terminals and intermodal rail facilities. The guide stresses the importance of the

coordination between the pavement designer and terminal planner; this is because the designguidelines are greatly dependent on the loading conditions associated with the different terminal

operation schemes.

The guide starts by giving an overview of typical container terminal areas focusing on the

different operational loading conditions and their significance on the pavement design. Thedifferent container terminal operational areas are: the wharf, the container storage yard, the

intermodal rail yard, the truck gate facility, and the buildings and automobile parking. With the

modernization of container terminals, several options became available to accomplish therequired tasks in each of these areas. The loading conditions in each sector vary with the type of

equipments used and the nature of commodities handled.

Section 2 of the guide describes the equipment configuration, motion, and usage in the terminal.It classifies the terminal operational options according to the different equipment used withineach area. For the container yard operations, three options are presented: the use of rubber tire

gantry (RTGs), front-end loaders (FELs), or straddle carriers. The usage conditions along withthe corresponding truck motion are discussed for each of these options. Similar analyses

portraying the operation scenarios for the RTGs and FELs in the intermodal yard are presented.Section 2 also describes the machinery loads involved in operating wheeled container yards and

gate areas. Having configured the terminal usage and operation schemes, the next step iscalculating the corresponding pavement loads.

Section 3 provides a guide for calculating the design loads and design load repetitions in acontainer terminal. The pavement is subject to both dynamic loading from container handlingequipment and static loading from corner castings on containers and either dolly wheels or sand

shoes on the chassis. Different equipment types, container load distributions, tire loads, axle andtire configurations, and repetition of loads are considered for different areas. Typical

specifications for different makers are provided for each equipment type. An analysis procedurefor determining the container weight distribution is presented. Depending on the containerterminal operational area and equipment used, typical load repetition calculations are derived.

Two approaches for computing load repetitions are discussed; the first requires converting thevarious loads and repetitions to equivalent single axle loads (ESAL), and the second

characterizes the loads directly by the number of axles, configuration, and weight. Equipmentweight distribution and wheel loads are stated as seen in the British Port Association 1982 HeavyDuty Pavement Manual. Accounting for the contact stress and wheel loads, damages to the

pavement are quantified using PAWLs (Port Area Wheel Load). Section 3 concludes bypresenting a comprehensive example to demonstrate the analysis schemes discussed in the

chapter.


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Section 4 of the manual details the process of site investigation. Proper site investigation is

essential for enabling an economic pavement design and safety and predictability during theconstruction operations. Typically, site investigation is carried out by geotechnical consultants,

and it aims at determining the properties of the soils within the influence zones below theunderside of the pavement. Different options and approaches for improving the ground soilconditions, in order to reduce the consequences of the problems experienced in port facilities, are

discussed in this section.

Section 5 discusses the influence of the subgrade on the pavement type, section and performancefor a particular type of operation. Failure to characterize the subgrade properties can result inhigh maintenance costs or premature pavement failure. This section sets out the material

characteristics that affect the pavement performance, and the test methods that can be used todetermine design values. It details the classification of soils as either fine or coarse grained,

granular or cohesive soils. The section also describes the soil mass volume relationships,

different classifications, and moisture density relationships. In-situ and lab testing procedures fordetermining these properties are also presented in this section.

Building on the acquired knowledge about the terminal operation and subgrade properties, it is

up to the designer to select a suitable pavement design. Three pavement designs are presented inthis guide: hot mixed asphalt (HMA), Portland cement concrete pavement (PCCP) and rollercompacted concrete pavement (RCCP). The design selection is based on the designers vision as

to how the pavement will perform. Generally, the site environmental conditions, the traffic loadsand speed, the pavement structure, and the design life/cost play a major role in determining the

performance of the pavement. Not all pavement options are suitable for all operational areas.HMA pavement is not usually considered in areas subject to heavy wheel loads. While PCCP

(jointed or continuously reinforced) are considered applicable for most operational areas, RCCPis best suited for large contiguous areas subject to heavy loading conditions.

Section 6stages the details of the design, construction, and quality assurance of HMA. The HMAdesign yields a flexible pavement that is both rut resistant and durable. Three major designprocedures for HMA mix design are discussed in this section: Marshall, Hveem, and Superpave.

All three procedures share common steps:

1) materials selection;2) selection of the design aggregate structure;3) determination of the optimal asphalt content;4) evaluation of moisture sensitivity.

The primary difference between the three approaches is the laboratory compaction method andthe effort used in the determination of the optimal asphalt content.

The layered elastic analysis theory, Section 7, is used for the analysis of the thickness of theHMA pavement. It is based on the fact that the stresses and strains, which develop in the

pavement and subgrade due to a wheel load application on a flexible pavement, are distributed


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according to the elastic properties of the various layers. A pavement design software, Kenlayer,

can be used to analyze the pavement sections and develop strains at critical points in thepavement. It analyzes elastic multilayer systems under circular loads and superimposes values

for multiple loads. It also has some iterative capabilities for the analysis of nonlinear viscoelasticlayers. The section concludes by presenting a design example for flexible pavements using themethods discussed in section 6.

Section 8 provides the design guidelines for PCCP, a system of subgrade soil, base course

material, and the surface course of Portland cement concrete. The concrete used for PCCP mustmeet the combined requirements of durability under repeated heavy loads, dimensional stabilityto minimize shrinkage and curling, and non-reactivity of its constituent material. Joints are

typically used in non-reinforced concrete pavements to limit warping and curling stresses whichare due to temperature and moisture gradients through the slab, prevent control cracking due to

volume changes, prevent damage to immovable structures, and facilitate construction. The

thickness of the designed pavement is based upon providing a sufficient structural capacity. Thekey structural design factors include:

1) slab thickness;2) slab concrete flexural strength;3) foundation support (from base and subgrade);4) wheel loads and repetition loads.

The PCCP thickness analysis, warping stress analysis, temperature reinforcement analysis, and

dowel bar analysis are demonstrated in two design examples at the end of section 8.

Section 9

provides the guidelines for the design of roller compacted concrete pavements.

RCC isa zero-slump concrete consisting of dense graded aggregates, cement and water. Because of itslow water content, it is usually placed using asphalt pavers and densified by compacting with

vibrating rollers. The design philosophy of RCC pavements is based on limiting the stresses inthe pavement to a level such that it can withstand repeated loadings of this stress magnitudewithout failing in fatigue. The critical stress is the maximum tensile stress at the bottom of the

concrete slab. Several methodologies for calculating this stress are well developed anddocumented in the literature. Knowing the expected traffic expressed in terms of wheel loads,

load configuration, and number of load applications expected over the design period, thedesigner varies the following parameters to optimize the flexural strength of the RCC pavement:

1) modulus of subgrade reaction;2) flexural strength of the concrete mix;3) thickness of concrete slab.

Design examples are provided at the end of the section to demonstrate the design methodology

discussed in this section.


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Section 10 of this guide introduces the Pavement Management System (PMS). PMS is a decision

making tool that assists the engineer, budget director, and management to make cost effective-decisions regarding maintenance and rehabilitation for a pavement network. Section 11 present

some of the PMS software packages currently used for pavement management.

The following flow chart is designed to enable the user to smoothly navigate through this design

manual.


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Determine Container

Terminal Operation:Terminal Planner

(Section 2)

Calculate Wheel Loadsand Load Repetitions

(Section 3)

Site Investigation &Subgrade Properties:

Geotechnical Engineer(Sections 4 & 5)

Pavement Design, Thickness Analysis

Hot MixedAsphalt, HMA

(Section 6)

Layered ElasticAnalysis

(Section 7)

Portland cementConcrete, PCC

(Section 8)

Roller CompactConcrete

(Section 9)

Pavement Management(Sections 10 & 11)


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1. Introduction.................................................. ........................................................ ................ 1-1

1.1 Description of the Pavement Design Guide ................................. .................................. 1-1

1.2 Container Terminal Operation Area............................................................ ................ 1-11.2.1 Wharf Area ........................................................................................................................................................1-31.2.2 Container Storage Yard .................................................................................................................................1-31.2.3 Intermodal Rail Yard .....................................................................................................................................1-41.2.4 Truck Gate Facility .........................................................................................................................................1-51.2.5 Buildings and Automobile Parking .............................................................................................................1-5


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1. Introduction1.1 Description of the Pavement Design GuidePavement is one of the most important facility in container terminals and occupies a significant amount ofthe costs for container terminal constructions and maintenance. This pavement design guide, prepared forthe Port of Los Angeles (POLA), provides general concepts and instructions on pavement design buttailored for the intensive loading conditions encountered in container terminals and intermodal railfacilities. Detailed design examples are also included to illustrate those concepts. Targeted at a UnitedStates audience, this guide is intended to provide a comprehensive reference of alternative design

procedures and material options available to the engineers undertaking the design of pavement for such afacility, both inside and outside the pavement community. After coving these pavement concepts, youshould, in general, be able to:

Describe the concept of container terminal and intermodal rail yard operations; Describe the pavement concept covered; Describe the typical equipment, methods and procedures used for pavement design; Implement typical pavement design analysis for container terminals; Develop a number of appropriate solutions for economic analysis; Apply these concepts and methods into practice;

In this pavement design guide, the following topics will be covered:

State of the art container terminal and intermodal rail pavement design; Container terminal and intermodal rail yard operational area; Container terminal operational options; Typical container handling equipment and the load repetition analysis;

Site investigation to determine characteristics of subgrade materials; Subgrade test and analysis to determine design values; Flexible pavement design; Layered elastic analysis and the Asphalt design example; Rigid Pavement Design and the Portland Cement Concrete (PCC) pavement analysis examples; Roller Compacted Concrete (RCC) pavement design; Pavement management and Pavement Management System (PMS) software;

The rest of this chapter describes typical container terminal operational areas and the importance ofidentifying these areas in the pavement design.

1.2 Container Terminal Operation AreaPavement designer has to consider dividing the container yard area into various operational areas basedon the anticipated variety of type of traffic and wheel loads. This will allow optimizing the pavement cost

by providing appropriate pavement thickness for each operational area. Identifying the limits of eachoperational area for current and future operation would require the pavement designer to work closelywith the container terminal planner.


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Container terminal complex includes wharf, container storage yard, intermodal rail yard, truck gatefacility, container handling equipment parking areas, buildings, and automobile parking areas. Theseoperational areas are identified on a typical container terminal layout in Figure 1-1.

Figure 1-1 - Typical Container Terminal Layout

Container facilities buildings include administration, maintenance buildings, and various service facilities.Intermodal rail facility includes area for working tracks (loading and unloading of containers), area forstorage tracks (storing loaded or empty cars), container storage area, and some times a separate truck gatefacility. The intermodal facility operational areas are shown on Figure 1-2.

Figure 1-2Intermodal Facility Operational Areas


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Pavement designers need to work closely with the container terminal and intermodal facility planners tounderstand the startup operational areas and future possible changes within the operational areas. Sincethe operational changes can be made by just changing yard striping, the pavement designer needs tounderstand the possible changes and provide an appropriate pavement section that would allow changes in

mode of operation in the future.

1.2.1 Wharf AreaWharf is where the transfer of containers from ship to shore and from shore to ship occurs. The mostcommon method employed in moving containers from ship to shore and shore to ship is using a containergantry crane that handles one or two 20-foot containers or a single 40 foot container. However, somecontainer terminals have started to deploy container cranes that can lift four 20 foot or two 40 footcontainers. These cranes are available with different capacities, different outreach and inreach, and legspread. Most of the current cranes have 100 ft. leg spread.

There are several methods of moving containers from the storage area to the wharf or from the wharf to

storage area. The most common methods are chassis with yard tractors and straddle carriers. In additionthree truck traffic lanes and hatch cover storage area are required on the land side of the crane rail. Hatchcovers range in sizes from 30 to 55 feet. Typical wharf area is presented on Figure 1-3.

Figure 1-3 - Typical Wharf Area

1.2.2 Container Storage YardContainer storage yard is where containers are stored for duration prior to leaving the terminal on ship,rail, or truck. Transporting within the container yard are used for chassis with yard or road tractors, and

straddle carrier. In smaller terminals and as a backup top loader type of equipment can be used totransport containers. In automated terminals containers are transported using automated guided vehicles(AGVs) or automated lifting vehicles (ALVs).

The major equipment used for storing containers in container yard are wheeled (container on chassis),rubber tire gantry (RTG), straddle carrie r, top loader or other similar equipments, and rail mounted gantry(RMG). Terminals may use combination of RTG and top picks to store containers.


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Most terminals have designated import, export, and empty container storage areas. In the US where thechassis are owned by the shipping industries the container terminals have designated chassis storage areasas well. Typical container terminal storage yard is presented on Figure 4.

Figure 1-4 - Typical Container Terminal Storage Yard

1.2.3 Intermodal Rail YardAn intermodal rail facility is used to stage, load and unload containers to and from the ports. Double stacktrains are loaded and unloaded by standard container handling equipment. A typical intermodal facilityconsists of working tracks, storage tracks, arrival and departure tracks, and a run around track. The

pavement designer needs to work with the terminal planner to identify the tracks that will be paved and allpossible affected operational modes such as: top picks, RMGs, RTGs, reach stacker. They will also needto identify areas designated for pre-staging inbound and outbound containers. Typical container storageyard is presented on Figure 1-5.

Figure 1-5 - Typical Container Storage Yard Intermodal Rail Yard


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1.2.4 Truck Gate FacilityContainer terminal and Intermodal rail gate facilities have very similar functions. They are used to obtain

information on the incoming and outgoing container trucks for operational and security purposes. Prior toimplementation of technologies, incoming trucks would be stopped by security, followed by a transaction

process via communication pedestals, and finally a physical inspection of container and chassis bymechanics. Some or all of the processes have been automated and/ or eliminated. However, even the mostautomated gates require trucks to stop for processing.

The Pavement designer should make assumptions that the gate will be operating 7 days a week with verylimited tolerance for maintenance during its operation. The stop and go nature of the gate operationshould also be considered in selecting the pavement material as well as the over all pavement thickness. Atypical Gate facility is presented on Figure 1-6.

Figure 1-6 Typical Gate Facility

Most of the container handling equipment is located near the maintenance and repair facility areas. Thecurrent and future types of equipments that would be stored in this area should be identified prior todesigning the pavement system.

1.2.5 Buildings and Automobile ParkingTypical container terminals and Intermodal rail require administration buildings, maintenance and repair

facilities and other operational buildings that have designated employee and visitors parking areas. Priorto development of pavement sections pavement designer should work closely with the terminal planner inidentifying current and possible future use of these areas.

The following chapters will discuss: operational options, pavement subgrade, flexible and ridgepavements, and pavement management.


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2. Container Terminal Operational Options................................................................................. 1

2.1 Grounded Container Yard Operations with RTGs .......................................................... 1

2.1.1 Equipment Motions ............................................................................................................................................1

2.1.2 Container Truck Motions .................................................................................................................................22.1.3 Usage.......................................................................................................................................................................3

2.2 Grounded Container Yard Operations with Front-End Loaders.................. ................... 42.2.1 Machine Configuration .....................................................................................................................................42.2.2 Equipment Motions ............................................................................................................................................62.2.3 Truck Motions .....................................................................................................................................................72.2.4 Usage.......................................................................................................................................................................8

2.3 Grounded Container Yard Operations with Straddle Carriers........................................ 92.3.1 Machine Configuration .....................................................................................................................................92.3.2 Equipment Motions ............................................................................................................................................92.3.3 Strad-Truck Interchange................................................................................................................................112.3.4 Usage.....................................................................................................................................................................12

2.4 Intermodal Yard Operations with RTGs or Travelifts...... ............................ ................. 132.4.1 Machine Configuration ...................................................................................................................................132.4.2 Equipment Motions ..........................................................................................................................................132.4.3 Truck Motions ...................................................................................................................................................142.4.4 Usage.....................................................................................................................................................................14

2.5 Intermodal Yard Operations with Front-End Loaders .................................................. 14

2.5.1 Machine Configuration ...................................................................................................................................142.5.2 Equipment Motions ..........................................................................................................................................152.5.3 Truck Motions ...................................................................................................................................................152.5.4 Usage.....................................................................................................................................................................16

2.6 Wheeled Container Yard Operations............................................................................. 16

2.6.1 Machine Configuration ...................................................................................................................................162.6.2 Truck Motions ...................................................................................................................................................18

2.6.3 Usage.....................................................................................................................................................................182.7 Gate Areas with Highway Tractors and Chassis............................................................ 19

2.7.1 Configuration .....................................................................................................................................................192.7.2 Usage.....................................................................................................................................................................19


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2. Container Terminal Operational Options

This section describes typical operational options in the modern container terminals.

2.1 Grounded Container Yard Operations with RTGs

Figure 2.1 shows a typical modern rubber-tired gantry crane in container yard operations.

Figure 2-1 Rubber-Tired Gantry Crane in Container Yard OperationsDeltaport, Vancouver, British Columbia

The typical modern RTG spans a space that includes six container stacks and a truck travel lane, and has agage of about 77 feet. Other widths are common. RTG height is expressed in terms of the maximumeffective stack height, plus the pass-over space. The machine in Figure 2-1 has a one-over-fourconfiguration. Other heights, up to one-over-six, are common.

The most common machine has eight wheels, such as that shown in Figure 2-1. Some older machineshave four wheels, one wheel on each leg. A few machines have sixteen wheels, in eight dual-wheel

trucks. Each truck can be rotated 90.

2.1.1 Equipment Motions

The following equipment motions are defined:

Hoist: Vertical motion with the main hoist drive.

Trolley: Horizontal motion perpendicular to the gantry runway, with the trolley drive.

Gantry: Horizontal motion parallel to the gantry runway, with the gantry drive.


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Virtually all container handling is done with only the hoist and trolley motions. Gantrying with acontainer is not generally done, because unequal weight distribution makes precise steering difficult.

Gantry motion perpendicular to the runways is possible in dedicated areas. There are three ways to

traverse an RTG perpendicular to its runway:Spin Trucks: Spin all trucks 90, traverse to a new position, and spin trucks back to their original

position.

Turn Around Truck: Spin all trucks but one, so that their rotation axes pass through the static truck. Turnthe entire RTG 90 about the static truck, spin the trucks back, traverse, and repeat.

Turn Around Center: Spin all trucks, so that their rotation axes pass through the RTG center-point. Turnthe entire RTG 90 about the center-point, spin the trucks back, traverse, and repeat.

All three of these motions generate high friction loads on the pavement, and are frequently done atembedded metal plates. The Spin Trucks method is the most common.

2.1.2 Container Truck Motions

Container trucks commonly traverse the entire length of the RTG block in a single lane, with a barechassis part of the way, and a loaded chassis the rest of the way. In many terminals, adjacent RTG blocksare laid out to create some weaving and bypass room for trucks, as shown in Figure 2-2 and Figure 2-3.

Runway

Runway

Runway

Runway

Stacks

Access Lane

Bypass Lane

RTG

Truck

Figure 2-2 Truck Access and Bypass Lanes for RTGsRTGs in Same Orientation


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Runway

Runway

Runway

Stacks

Access Lane

Access Lane

RTG

Truck Bypass Lane

Figure 2-3 Truck Access and Bypass Lanes for RTGs

RTGs in Opposing Orientation with Shared Bypass

Where weaving and bypass lanes are available, trucks will generally use them only if the access lane isobstructed downstream.

2.1.3 Usage

RTGs are used in conditions requiring high storage density and frequent container re-handling betweenadjacent stacks. The need to re-handle means that some empty slots will always be needed.

Figure 2-4 depicts the empty spaces required to accommodate re-handling containers. The container inthe white slot labeled T is the target for retrieval. The containers in the grey slots labeled 1, 2, etc.,need to be moved to the corresponding white slots, which need to be left empty. This reduces theeffective stacking height.


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RTG 6 Wide, 1+6 High5.2 Effective HeightRTG 6 Wide, 1+4 High3.5 Effective Height

T

5

4

3

2

1 5 4 3 2 1

T

3

2

1 3 2 1

Figure 2-4 Container Rehandling Space for RTGs

A typical work sequence for an RTG retrieval operation would be as follows:

Truck arrives adjacent to target storage location with a bare chassis.

RTG is assigned, and gantries to trucks location.

RTG re-handles obstructing containers to other stacks without gantrying.

RTG retrieves target container, and sets it on the truck chassis.

Truck departs with loaded chassis.

Export loads are typically arranged to mimic the ultimate ship stowage pattern. In many RTG terminals,a single set of adjacent export stacks would have a single common ship-stowage designation. Importloads are typically arranged in the order they are retrieved from the ship, since the order of delivery to thegate is unknowable. These patterns minimize the number of gantry moves required during shipoperations, but maximize the number of gantry moves required during gate operations.

The need to keep open slots for re-handling, along with the tendency to sort containers within RTGblocks, tends to limit overall RTG space utilization. When calculating annual truck trips through RTGoperating areas, this reduced utilization needs to be taken into account.

2.2 Grounded Container Yard Operations with Front-End Loaders

2.2.1 Machine Configuration

Front-end loader (FEL) is a generic term for a broad class of equipment. All types of FEL pick up acontainer in a position cantilevered outside and in front of the machines wheelbase. FELs come in threecommon configurations:


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Top-Pick (TP): The spreader is mounted on a vertical mast. The container is picked up by its four topcorner castings. The machine is used for both loads and empties. Top-picks frequently have a forkliftattachment that allows picking up loaded 20-foot containers by their bottom forklift slots.

Side-Pick (SP): The spreader is mounted on a vertical mast. The container is picked by the two top

corner castings closest to the FEL. The machine is used for empties only.

Reach-Stacker (RS): The spreader is mounted on a hydraulically-lifted, extensible boom. The containeris picked up by its four top corner castings. The machine is used for both loads and empties, and canhandle containers at some distance from the machine.

Figure 2-5 shows a typical top-pick. Figure 2-6 shows a typical side-pick. Figure 2-7 shows a typicalreach-stacker.

Figure 2-5 Typical Top-Pick FEL with Spreader at 20'


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Figure 2-6 Typical Side -Pick FEL Serving 7-High Stack

Figure 2-7 Typical Reach-Stacker FEL with Spreader at 20'


All FELs having rotating rear trucks and are fairly maneuverable. The following motions are defined:

Hoist: Vertical motion along the mast on TPs and SPs, or vertical motion of the boom on RSs


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Extend: Extension of the boom on RSs.

Travel: Straight-line motion of the FEL.

Turn: Spinning of the rear truck, and rotation about one of the front trucks.

Most container handling is done without turning, simply traveling forward and backward perpendicular toa storage stack.

TPs and SPs can only access the top-most container in the outer-most stack in any container block. If re-handling is required, the obstructing container must be moved to an adjacent block. This requires theFEL to do the following:

Load re-handled container

Back upTurnTraverse to the next blockTurnAlign to the blockSet the re-handled containerBack upTurnTraverse to the original blockTurnAlign to the block

Load target container

Reach stackers have some ability to re-handle containers into the stack second from the front, but re-handling is usually done the same as for TPs and SPs.

This sequence takes quite a bit of time, and so most FELs are restricted to operations involving simplefore-and-aft motions.

2.2.3 Truck Motions

Trucks commonly traverse the entire length of the FEL block in a single lane, with a bare chassis part ofthe way, and a loaded chassis the rest of the way. The gap between adjacent FEL storage blocks is fairlylarge, frequently 65 or more, so there is usually room for maneuvering. However, simultaneous accessof both adjacent FEL blocks can reduce this flexibility. Figure 2-8 shows a common FEL and trucktraffic configuration.


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Access Lane

Access Lane

FEL

FEL Tire Path

Truck

Figure 2-8 Truck Access for FELs Working Adjacent Blocks

Note the intersection of the FEL and truck tire paths in Figure 2-8. This area is subject to numerousrepetitions, since the FEL must retreat each time to clear the truck access lane, then advance all the way tothe face of the container stack.

In grounded CY operations, the stacks are in fixed locations, and so the FEL tire wear patch does not varyover time.

2.2.4 Usage

FELs are used in conditions requiring high storage density, in which container re-handling is expected tobe rare or non-existent. The long cycle time for re-handling between blocks makes re-handling veryexpensive and unproductive.A typical work sequence for an FEL retrieval operation is as follows:

Truck arrives, and stops short of the FEL travel path.

FEL arrives, aligns to the block, and advances across the truck access lane to the face of theblock.

FEL picks the container, and retreats to clear the truck access lane.

Truck advances, aligning to the FEL.

FEL advances, and sets the container on the truck.

FEL retreats or hoists to clear the truck.

Truck departs.

A typical work sequence for an FEL storage operation is as follows:

Truck arrives, and aligns to the stack.

FEL arrives, and aligns to the truck.

FEL advances, and picks the container from the truck.


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FEL retreats or hoists to clear the truck.

Truck departs.

FEL advances across the truck access lane to the face of the block.

FEL sets the container atop the stack. FEL retreats to clear the truck access lane.

TPs are commonly used to handle pre-sorted export loads. RSs are less-commonly used. SPs arecommonly used to handle empties. FELs are almost never used to handle import loads, because therandomness of retrieval order generates a high re-handle incidence. In facilities where FELs are used tohandle imports the stack height and width is kept at two or less containers.

As with RTGs, export loads are sorted in FEL blocks according to ship stowage designations. Duringship load-out operations, all of the containers in a block will be considered logically interchangeable, sothat the FEL can always work the most accessible container and avoid re-handling.

Empties in FEL blocks are sorted according to their physical type and ownership. During delivery ofempties to the ship or a trucker, all of the containers in a block will be considered logicallyinterchangeable, minimizing the need for re-handles. Some physical types, e.g., dry 40-foot standardcubes are quite common, and generate large, full blocks. Some physical types or ownership categoriesare rare, and generate poorly utilized blocks.

The need to avoid re-handling in FEL blocks places a practical limit on the utilization of these areas.Utilization will vary from terminal to terminal, based on local commercial patterns. These utilization

patterns need to be considered when calculating annual FEL and truck trips.

2.3 Grounded Container Yard Operations with Straddle Carriers


Figure 2-9 shows a typical modern straddle carrier.

Straddle carriers (strads) combine the ability to stack and transport containers over long distances. Moststraddle carriers are eight-wheeled machines, with the steering of the wheels coordinated to generate atight turning radius. Most strads are built for one-over-two operations. Some terminals are now usingone-over-three straddle carriers. One high strads are also available as transporters only.


Straddle carriers can drive equally well, forward or backward. The operators cab is at the top, at one

end. The driver is typically on a swivel chair, and can orient to see either direction of travel. However,many drivers prefer to drive longer distances with the cab forwards, because visibility and safety areimproved. Many terminals have operating rules that dictate this behavior.


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Figure 2-9 Typical Straddle Carrier, One -Over-Two

The hoist and spreader move vertically, with some limited ability to adjust spreader position for finealignment to stacks.

Long-distance travel is supposed to be done with the container in the lowered position, so that stability isincreased. There is usually a transition between long-distance travel over the open roadway and motion

over container stacks. During this transition, the spreader is raised and the strad slows down to ensureproper alignment.

There is limited clearance between stacked containers and the inner face of the drive equipment. Travelspeed over stacks is reduced, and the driver must take some care to avoid striking the stacked containers.It has been found that when traversing long strad stacks, the drivers attention may wander, increasing the

probability of collision. Any irregularities in the pavement may cause the strad to wander, furtherincreasing the probability of collision. To minimize collision probability, the length of strad stacks isgenerally limited to twelve or fourteen 20-foot slots.

Figure 2-10 shows a typical stack configuration in a straddle carrier storage area. It is important to notethat adjacent blocks of containers share strad tire paths, so that strads may not pass one another in

adjacent blocks. This is done to maximize storage density. It affects the number of tire passes over anyone tire path.


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StacksStradTire Paths

Figure 2-10 Typical Strad Stack Configuration

Storage run positions are painted onto the pavement, and do not vary much with time. The strad tire wearpaths can stay in one place for years, concentrating load repetitions in fairly tight bands.

2.3.3 Strad-Truck Interchange

Strad-based terminals have an interchange area where trucks and straddle carriers can exchangecontainers. This area is generally laid out for maximum safety and visib ility, because of the hazardsinherent to the operation. The layout of this area will vary considerably between terminals, depending onlocal safety practices, truck-driver skill, and strad-driver skill.

Figure 2-11 shows the interchange area at Portsmouth Marine Terminal in Virginia.

Figure 2-11 Strad/Truck Interchange Area

Portsmouth Marine Terminal, Virginia

Figure 2-12 shows the layout of a typical strad/truck interchange area. The layout of the area allowsstrads to simultaneously serve adjacent trucks. The tire paths between adjacent interchange slots are not


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shared. Depending on local safety rules, trucks may either be backing into the interchange slot, or drivingforward into it from inside the strad work zone. Herringbone configurations are also common.

Strad

Truck

InterchangeSlot

Driver

Zone

Tire Paths

Figure 2-12 Strad/Truck Interchange Area

2.3.4 Usage

Strads are used in conditions requiring moderate storage density and high productivity. Strads are capableof effective re-handling. Figure 2-13 shows the empty spaces required to accommodate re-handling ofcontainers in 1-over-3 and 1-over-2 configurations. Terminal operators typically want to limit thedistance a strad driver needs to move to find an open slot for a rehandled box. This requires that a certainnumber of slots be kept clear, reducing the effective stacking height.

11

Strad 1+2 High

1.75 Effective Height

Target

Target2

Strad 1+3 High

2.50 Effective Height

12 1

Figure 2-13 Container Rehandling Space for Strads

Strads are used for both loaded and empty container operations, although many terminal operators preferto keep the bulk of their empty containers in side-pick configurations for higher density.

Each container storage or retrieval operation typically requires that the strad traverse the entire length ofthe storage run.


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Export loads are typically sorted in runs corresponding to ship stowage patterns, so re-handles arerelatively rare. Re-handling is more common in import load areas, and the additional strad motions upand down the run need to be considered in calculating load repetitions.

2.4 Intermodal Yard Operations with RTGs or Travelifts


Figure 2-14 shows an RTG serving an intermodal double-stack rail car.

Figure 2-14 RTGs Serving Intermodal Doublestack Car

The configuration of the machine is similar to that used in grounded container yard operations. Onecommon difference is the presence of a stabilizer system that restricts the side-sway of the spreader. Thisstabilizer system is critical in the handling of trailers, as it allows the rapid attachment of trailer kingpins

to support stanchions on piggyback cars. Stabilizer systems are more common in inland intermodalyards, where domestic trailer operations are more common. Maritime intermodal yards frequently usestandard, non-stabilized, wire-rope RTGs.


The motions of the RTG are similar to those described in Section 2-1.1 for grounded container yardoperations using RTGs.


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2.4.3 Truck Motions

Trucks commonly traverse the length of the RTG run along bypass lanes, because of the great length ofmany of the rail car cuts. See Figure 2-15 below. The trucks weave into the loading access lane just

upstream of the target location, and weave back to the bypass lane when they are clear of the RTG.

2.4.4 Usage

Figure 2-15 shows one common layout for high-density intermodal working tracks, using RTGs. Thereare many variations on this theme, based on the dimensions of the RTGs, the nature of the truck and railtraffic, and the configuration of the site.

Runway

Runway

Runway

Runway

Access Lane

Access Lane

Bypass

Bypass

RTG Rail Car

Truck

Tracks

Tracks

Figure 2-15 Typical RTG Intermodal Rail Layout

The amount of gantrying by the RTGs is much less than in grounded container yard operations, becausethe RTGs are generally working in a systematic way from one end of the track to the other. There are, ofcourse variations between terminals, but most RTG assignments are pretty well-organized.

The utilization of double-stack rail equipment is fairly high, so it is reasonable to assume, for the purposesof traffic counts, that cars arrive loaded and depart loaded.

2.5 Intermodal Yard Operations with Front-End Loaders


Figure 2-16 shows an FEL working an intermodal double -stack car.


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Figure 2-16 Front End Loader Serving Intermodal Car

Top-picks and reach-stackers are commonly used on intermodal operations. Side-picks are not commonlyused.

Reach-stackers have the advantage of being able to reach a second track, by extending the boom. This isparticularly useful in serving tracks set against a terminal boundary.FELs are capable of serving curved working tracks, while RTGs are not.


The motions of FELs in serving rail cars are similar to those described in Section 2.2.2 for groundcontainer yard operations. The FEL typically moves fore and aft, turning frequently to move from car tocar. The area of pavement immediately adjacent to the track sees a great deal of traffic, as depicted inFigure 2-17.

In grounded CY operations, the stacks are in fixed locations, and so the FEL tire wear patch does not varyover time. In intermodal operations, the alignment of cars is not constant, as each train has differentmixture of car and platform lengths and positions. The tire wear patch shifts constantly, spreading the

repetitions over a much greater area.

2.5.3 Truck Motions

Trucks generally traverse the length of the working track segment along the access lane, as shown inFigure 2-17. The access lane thus sees the combined traffic of trucks running parallel to the track, andFELs moving back and forth perpendicular to the tracks.


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2.5.4 Usage

Figure 2-17 shows one common layout for high-density intermodal working tracks, using top-picks.There are many variations on this theme, based on the nature of the truck and rail traffic, and the

configuration of the site. Note the differing car alignments, and their impact on the location of FEL tirewear paths.

Track

Track

Track

Track

Access Lane

Access Lane

Access Lane

Access Lane

FEL

FEL Tire PathTruck

Rail Car

Figure 2-17 FEL and Truck Access for Inermodal Operations

2.6 Wheeled Container Yard Operations


Figure 2-18 shows a typical wheeled storage row.

Figure 2-18 Typical Wheeled Storage Row


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In wheeled container storage, containers are mounted and parked on street-capable chassis. Whileparked, the chassis are sitting on their landing legs, which can be retracted for travel. The pads on thelanding legs generate a high ground pressure, frequently causing local pavement damage.

Street chassis have twist locks at each corner to secure the container for road travel. Chassis for 40containers are just over 40 long. They have a gooseneck which mates to a well built into the undersideof the standard container. Chassis for 20 containers are generally 28 or longer, to avoid exceedinghighway axle load limits.

Containers may also be mounted on dedicated terminal chassis, known as bomb carts. Bomb carts arenot generally street-legal, because they are wider than 8 feet. They are equipped with flare guides at eachcorner, making container mounting faster and easier. Bomb carts are typically 40 or 45 long, and canhold two 20 containers with a total rated load of 48 long tons. Figure 2-19 shows the rear flare guides ona typical bomb cart.

Figure 2-19 Rear Flare Guides on a Bomb Cart

A mixture of in-terminal tractors, and off-terminal, or street, trucks typically accesses wheeledcontainer storage. The configuration of street trucks varies considerably. Terminal tractors are muchmore uniform, and differ from street trucks in a number of ways:

Shorter wheel baseHydraulically-liftable fifth wheel

Tighter turning radius

Single rear axle

The hydraulic-lift wheel on terminal tractors allows them to back under a parked chassis, pick the chassisup off its landing legs using the fifth wheel, hook up the brakes and electrics, and drive away. The


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terminal tractor can park chassis just as quickly. The act of lowering the chassis using the fifth wheelincreases the impact load under the landing leg pads, exacerbating pavement damage.A typical terminal tractor is shown in Figure 2-20.

Figure 2-20 Typical Terminal Tractor

2.6.2 Truck Motions

Removing a chassis from storage is a fairly simple truck motion.Placing a chassis into storage generally requires some maneuvering, especially for street tractors. Parkingslots are typically ten feet wide, and long-wheelbase tractors have some difficulty backing a 40-footchassis gracefully into this width.

The access aisles running between rows of parked containers frequently double as general traffic

circulation roads for the terminal. As such, the number of truck repetitions is not directly related to justthe storage and retrieval operations within a row. Truck repetitions within a row will depend on theoverall traffic layout of the terminal. If the terminal is amply supplied with dedicated arterial circulationroads, traffic will be diminished in the storage rows.

2.6.3 Usage

Wheeled storage is used where low storage density is acceptable, and high container accessibility isrequired. Wheeled storage is used for import and export loads, and for empties. Wheeled storage iscommonly used for reefer containers, since plugging, unplugging, and servicing reefers is easier whenthey are mounted and accessible.

Peak storage utilization is typically very high, because re-handling is not required in any circumstance.When utilization is high, drivers may have to search a bit to find an empty slot to park a chassis in. Thisincreases driving time, and increases the number of pavement load repetitions.

When wheeled storage is in use, bare chassis can make up a considerable portion of the total storagedemand. At times, the high population of bare chassis mandates that their storage be densified. Figure2-21 shows a typical high-density storage area for bare chassis. Note these chaises are stacked to saveyard spaces.


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Figure 2-21 High Density Bare Chassis Storage

2.7 Gate Areas with Highway Tractors and Chassis

2.7.1 Configuration

There are many different configurations in use for gate complexes. In general, however, they have incommon a number of basic components:

Queuing Lanes: In-stream queuing space for trucks waiting for processing.

Remote Processing Stations: Locations where the truck driver can interact with terminal staff throughtelecommunications equipment, without leaving the truck cab.

Scales: Weigh scales.

Inspection Stations: Locations where the truck is visually inspected, and paperwork is exchanged.

Holding Areas: Locations where trucks are parked awaiting resolution of problem transactions, or areotherwise out of the main gate traffic stream.

Only street tractors pass through terminal gates, and only with street-legal chassis. Neither terminaltractors nor bomb carts are suitable for open-road use, and they are generally not registered as such. Theconfiguration of street trucks varies widely, based on local commercial conditions.

A typical gate can process about 20 to 25 trucks per hour, per lane. The number of gate lanes isestablished through queuing analysis based on the exact nature of the gate process.

2.7.2 Usage

A typical truck process through a gate requires many stops and starts, within queuing areas, at processingand inspection stations, at stop-lines established to protect pedestrians, and around holding areas.

Gate traffic tends to be concentrated at the interfaces between the gate and road, and gate and containeryard. Within the gate, truck traffic is diffused across many processing lanes, spreading the repetition loadout to a considerable degree.


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3. Typical Container Handling Equipment Wheel Load Calculation...... .................................. 3-1

3.1 Container Handling Tires and Pressures ...................................................... ................ 3-1

3.2 Yard Equipment............................................................... ............................................ 3-23.2.1 RTGs ..................................................................................................................................................................3-23.2.2 Straddle Carriers .............................................................................................................................................3-33.2.3 Top Picks ............................................................................................................................................................3-33.2.4 Side Picks............................................................................................................................................................3-43.2.5 Reach Stackers ..................................................................................................................................................3-53.2.6 Yard Hustlers ....................................................................................................................................................3-6

3.3 Container Distribution...................................................... ............................................ 3-6

3.4 Static Loads .................................................... ....................................................... ....... 3-8

3.5 Typical Load Repetition Analysis for Container Terminals and Intermodal Facilities . 3-8

3.5.1 Entrance Gate ...................................................................................................................................................3-93.5.2 Wheeled Storage Area ....................................................................................................................................3-93.5.3 Side/Top Pick and Truck Operations ...................................................................................................... 3-103.5.4 RTG and Truck Operation ........................................................................................................................3-11

3.6 Equipment Weight Distribution and Wheel Loads ........... ............................ ...............3-14

3.6.1 RTG ..................................................................................................................................................................3-143.6.2 Side or Top Pick ............................................................................................................................................3-153.6.3 Yard Trucks ................................................................................................................................................... 3-17

3.7 Pavement Damage ................................................... ....................................................3-18

3.7.1 Damage ............................................................................................................................................................3-183.7.2 Proportional Damaging Effect ..................................................................................................................3-193.7.3 Average Damage............................................................................................................................................ 3-193.7.4 Critical Damage .............................................................................................................................................3-193.7.5 Total Damage of a Plant and Wheel Proximity Factors .....................................................................3-20

3.8 Equivalent Load Repetitions ....................................................... .................................3-213.8.1 RTG ..................................................................................................................................................................3-213.8.2 Yard Trucks ................................................................................................................................................... 3-213.8.3 Side and Top Picks........................................................................................................................................3-22

3.9 A Comprehensive Wheel Load Calculation Example ...................................................3-22

3.9.1 Key Notations ................................................................................................................................................. 3-233.9.2 RTG Operation RTG Repetitions .........................................................................................................3-233.9.3 RTG Operation Truck Repetitions ....................................................................................................... 3-243.9.4 Side/Top Pick Repetitions ...........................................................................................................................3-243.9.5 Damage Top Pick .......................................................................................................................................3-253.9.6 Damage RTG ............................................................................................................................................... 3-313.9.7 Design Summary ...........................................................................................................................................3-33


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3. Typical Container Handling Equipment Wheel Load Calculation

One important function of the pavement on the container handling equipment runways is to distributerepetitive load into earth structures. Therefore, calculation of design load and design load repetitions

(Load Repetition: Number of time that an area undertaking a certain amount of load.) plays an importantrole in the pavement design. This section provides a guide on calculation of design load and design loadrepetitions in a container terminal. Different equipment types, container load distribution, tire load, axleand tire configuration, and repetitions of loads are considered for different areas such as RTG runwaysand top pick operation area. At the end of the section, a comprehensive example is presented to illustratethe described concepts and methods.

3.1 Container Handling Tires and Pressures

Container handling equipment, including FELs, RTGs, strads, hustlers with bomb carts, hustlers withchassis, and street legal trucks with chassis, is typically used in container terminals and intermodal railfacilities. Table 3-1 lists typical tire pressures for different makers and different tire sizes of container

handling equipment.

Table 3-1. Typical Tire Pressures

Tire PressuresMaker Size psi. bars

Goodyear 11R22.5 144 9.9Nokian 14.00-24 161 11.1

Goodyear 14.00-24 144 9.9

Kalmar spec. 14.00-24 138 9.5

AVE 14.00-24 148 10.2

Goodyear 16.00-25 152 10.5Nokian 16.00-25 131 9.0

Nokian 16.00-25 170 11.7Kalmar spec. 16.00-25 116 8.0

AVE 16.00-25 142 9.8Goodyear 18.00-25 131 9.0Goodyear 18.00-25 167 11.5

Paceco spec. 18.00-25 139 9.6

Nokian 18.00-25 165 11.4Kalmar spec. 18.00-25 131 9.0

AVE 18.00-25 147 10.1Nokian 18.00-33 145 10.0

Goodyear 18.00-33 144 9.9AVE 18.00-33 145 10.0

Goodyear 21.00-25 112 7.7Kalmar spec. 21.00-25 116 8.0

AVE 21.00-25 114 7.9

Other manufacturers:Michelin

General Tire


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3.2 Yard Equipment

This section presents various yard equipments, such as RTGs, straddle carriers, top picks, side picks,reach stackers, and yard hustlers. Pictures, typical dimensions, and typical specifications for different

makers are provided for each equipment type.

3.2.1 RTGs

Figure 3-1 A typical RTG

Kalmar 402315-2045C

16 wheels, 5+1 lift, 40.6t max lift, 125.6t dead weight, 16.00-25 tires. 8 wheels, 5+1 lift, 40.6t max lift, 127.8t dead weight, 18.00-25 tires.

PACECO PTD 200503

8 wheels, 5+1 lift, 40.6t max lift, 126.0t dead weight, 18.00-25 tires.

Other manufacturers:Noel (Gottwald)

PMCTaylorFantuzzi


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3.2.2 Straddle Carriers

Figure 3-2 A typical Straddle Carrier

Kalmar CSC

8 wheels, 4 container stack capacity, 50t max lift, 74.95t dead weight, 16.00-25 tires.

Kalmar Shuttle Carrier

4 wheels, 2 container stack capacity, 50t max lift, 45t dead weight, 18.00-33 tires.

Other manufactures:Belotti

NelconNoel (Gottwald)

MHI

3.2.3 Top Picks

Figure 3-3 A typical Top Pick


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Kalmar DCF450CSG

6 Wheels, 5 container stack capacity, 100,000 lbs. max container weight, 165,000 lbs. deadweight, 18.00x33 tires.

Kalmar DCF410CSG

6 wheels, 5 container stack capacity, 90,000 lbs. max container weight, 154,000 lbs. dead weight,18.00x33 tires.

Taylor 954

6 wheels, 4 container stack capacity, 95,000 lbs. max container weight, 157,800 lbs. dead weight,18.00x25 tires.

Other manufacturers:Hyster

Fantuzzi

3.2.4 Side Picks

Figure 3-4 A typical Side PickKalmar DCE80-45 E8

6 wheels, 7/8 (9.5/8.5 containers) container stack capacity, 17,600 lbs. max lift, 81,600 lbs. deadweight, 12.00x24 tires.

Kalmar DCE100-45 E8

6 wheels, 7/8 (9.5/8.5 containers) container stack capacity, 25,400 lbs. max lift, 92,400 lbs. dead

weight, 12.00x24 tires.

Kalmar DCD70-40 E5

6 wheels, 5 container stack capacity, 15,400 lbs. max lift, 68,100 lbs. dead weight, 12.00x20 tires.

Other manufacturers:Taylor

Hyster

Fantuzzi

SM V


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3.2.5 Reach Stackers

Figure 3-5 A typical Reach Stacker

Kalmar DRF4000C-450C

6 wheels, 5-4-3 (9.5) 5-5-4 (8.5) stacking capacity, 99,200 max lift, 194,000 dead weight,18.00x25 tires.

Kalmar DRS4527-4531


Kalmar DRD450-80S


Other manufacturers:Taylor

Hyster

Fantuzzi

SM V


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3.2.6 Yard Hustlers

Figure 3-6 A typical Yard Hustlers

Ottawa 50

6 wheels, 63,300 maximum capacity, 14,500 dead weight, 11R22.5 tires Ottawa DOT/EPA 60

6 wheels, 62,000 maximum capacity, 18,000 dead weight, 11R22.5 tires

Kalmar YT-50

6 wheels, 63,300 maximum capacity, 14,500 dead weight, 11R22.5 tires

Other manufacturesMagnum

Capacity of Texas

3.3 Container Distribution

Heaviest load will cause most damage but may only make up less than one percent of the containerstransported. Therefore, to accurately analyze heavily loaded port pavements it is important to understandthe weights of cargoes that will be handled. Such container distribution will be used to calculate

proportional damage effect, as seen in section 3.7.2.

Typical container weights range from approximately 10,000 to 67,000 pounds. Containers over 67,000pounds are within a very small percentage and generally overweight for highway transport. A vessel

discharge report summarizing all containers sizes and weights discharged and loaded during a vessel callin representative month can be obtained from a container terminal operator. A simplified tabulation ofthe combined import/export container distribution for a container terminal in the northwest is shown inTable 3-2 below. Figure 3-7 shows the comparison between measured and assumed containerdistributions. It should be noted that container weight distributions are highly sensitive to changes in thetypes of commodities handled. Therefore, the pavement designer should work closely with terminal

planners to understand possible changes to commodities types in the region.


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Table 3-2. Container Weight Distribution

0%

5%

10%

15%

20%

25%

30%

35%

0-10

,000

10,001-25,0

00

25,001-35,0

00

35,001-40,0

00

40,001-45,0

00

45,001-50,0

00

50,001-55,0

00

55,001-60,000

60,001-65,0

00

65,001-70,0

00

72,501-100

,000

Container Weight (pounds)

P

ercentage

ofInventory

Measured Vessel Distribution Assumed Yard Distribution

Figure 3-7Measured vs. Assumed Container Distribution

Using the assumed container distribution discussed above, container handling equipment wheel loads, tirecontact pressure, and tire contact radius (Typical pavement design generally assumes the tire loads isuniformly distributed over a circular area.) for each load increment can be tabulated. A typical table forstraddle carrier is shown in Table 3-3. Empty container handler wheel loads, with and without an emptyrefrigerated container are shown in Table 3-4.

Container Weight

Range

(pounds)

Container Weight

(pounds)

Container Weight

Distribution

0 10,000 10,000 (empty box) 25%

10,001 25,000 25,000 17%

25,001 35,000 35,000 12%

35,001 40,000 40,000 7%

40,001 45,000 45,000 8%

45,001 50,000 50,000 8%

50,001 55,000 55,000 8%

55,001 60,000 60,000 7%60,001 65,000 65,000 6%

65,001 70,000 70,000 1%

72,501 100,000 100,000 1%


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Table 3-3. Kalmar CSC-350 Straddle Carrier Wheel Loads

Container Weight

(pounds)

Single Wheel Load

(pounds)

Tire Contact Radius

(inches)

Tire Contact Pressure

(psi)

0 17,088 6.12 14510,000 18,338 6.34 145

25,000 20,213 6.66 145

35,000 21,463 6.86 145

40,000 22,088 6.96 145

45,000 22,713 7.06 145

50,000 23,338 7.16 145

55,000 23,963 7.25 14560,000 24,588 7.35 145

65,000 25,213 7.44 145

70,000 25,838 7.53 145

100,000 29,588 8.06 145

Table 3-4. Taylor TEC-155H Wheel Loads With or Without An Empty Container

Container

Weight

(pounds)

Front Axle

Dual Wheel

Load

(pounds)

Front Axle

Single Tire

Contact

Radius

(inches)

Front

Tire

Contact

Pressure

(psi)

Rear Axle

Single

Wheel Load

(pounds)

Rear Axle

Single Tire

Contact

Radius

(inches)

Rear

Tire

Contact

Pressure

(psi)

0 22,000 5.40 120 11,900 6.15 100

11,000 31,167 6.43 120 8,233 5.12 100

3.4 Static Loads

In addition to dynamic loading from container handling equipment, port pavements are typicallysubjected to static loading from corner castings on containers and either dolly wheels or sand shoes onchassis. Corner castings measure 7-inches by 6 3/8-inches and project approximately -inch below thecontainer base. While containers may be stacked in a block arrangement up to four high, it is unlikelythat all containers in the stack will be fully loaded. Two high container stacks exert an average load ofapproximately 120,950 pounds and a contact stress of 677 pounds per square inch. Chassis dolly wheelsare typically 4-inches wide by 9-inches diameter. The contact area of each wheel is approximately-inch by 4-inches and generates a stress of 5,600 psi. Sand shoes are typically 6-inches by 9-inches andexert a contact stress of 280 psi.

3.5 Typical Load Repetition Analysis for Container Terminals and Intermodal Facilities

Different areas in container terminals may have different equipment and subject to different loadrepetitions. This section presents formulas of typical load repetition calculation for different areas in acontainer terminal.

Areas of the yard that can be converted to other use, such as the conversion of wheeled parking to side-pick empty storage or top-pick storage to RTG storage, need to be designed for more severe loading


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condition. In order to achieve the maximum flexibility, some terminals use a uniform design for themajority of the pavement.

Typically, there are two approaches to compute load repetitions of vehicles. One approach is to convert

various loads and repetitions to an equivalent number of standard or equivalent loads. This is calledESAL (Equivalent Single Axle Loads) approach. The most common equivalent loads used in the U.S. isthe 80 kN (18,000 lbs). Another more complex but more accurate approach characterizes loads directly bynumber of axles, configuration and weight. No conversion to ESAL is involved. In the following sections,

both approaches are discussed.

3.5.1 Entrance Gate

Obtain the estimated throughput capacity per year for the terminal in Twenty Equivalent Units (TEUs)and a conversion factor from lifts to TEUs from terminal planners. Also obtain the assumed percentage(%) of the total throughput going through the gate (D T). If there is no on-dock rail intermodal facility the100% of the throughput would go through the gate. Use the following equation to compute Equivalent

Single Axle Loads (ESAL).

Given:

C4 = TEU/Lift (typical number of TEU per lift between 1.7 to 1.85)

C5 = Transactions/Lift (typical number of truck transaction per lift between 1.5 to 2)

DD =50 % (directional split, 50% in and 50% out)

DL = 90% (% of traffic in the preferred lane)

DT = % (% of lifts moved by truck 100% for no on-dock intermodal facility)

TF = 3 ESAL/Trans (estimated number of ESAL per transaction)

YC = total annual terminal capacity in TEUs

We have:

Design Lane ESALs = YC / C4 C5 DT DD DL TF (3-1)

3.5.2 Wheeled Storage Area

Given:

PS = estimated number of wheeled storage slotsC5 = 2 Transactions/Slot (typical number of truck transaction per slot)

TF = 3 ESAL/Trans (estimated number of ESAL per transaction)

SU = estimated slot utilization between 70 to 90%

DW = assumed average chassis/container dwell time


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We have:

Design ESALs = PS SU 365 / DW C5 TF (3-2)

3.5.3 Side/Top Pick and Truck Operations

It is assumed the containers will be delivered using truck and stacked using side or top-picks. Assumingthat the storage area has the configuration as shown in the Figure 3-8, the calculations are as follows:

In the Side/Top Pick yard, the heaviest traffic will be directly in front of the first row. At this locationthere are two types of traffic - Side/Top Loader and Truck traffic. The Side/Top Pick traffic is limited tothe number of boxes in the first row, while the truck traffic is defined by the size of the whole stack,

because the trucks follow each other along the length. For Side/Top Picks, the storage area can beaccessible from only one side or two sides. If Side/Top Picks and trucks can access both side, therepetitions will be decreased to a half. In the calculation, the variable, "Number of accessible sides (C7)",is added for this purpose.

Given:


DW = assumed average container dwell time in days

C4 = TEUs per lift (typical number of TEU per lift between 1.7 to 1.85)

C5 = trips per box (2 for Side/Top Pick area)

C6 = moves per tripC7 = number of accessible sides (1 or 2)

L = length of the stack in TEUs

W = width of the stack in TEUs

H = height of the stack in TEUs


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Figure 3-8 Dimensions of a yard block

We have:

Truck Load Repetitions = C5 C6 (365 / DW) SU L H W / C4 / C7 (3-3)

Side/Top Pick Load Repetitions = C5 C6 (365 / DW) SU H W / C7 (3-4)

3.5.4 RTG and Truck Operation

We use the following method to compute RTG repetitions. For truck operation in the RTG area, sameformula as in side or top pick area is used. Two scenarios needs to be considered: RTG Gantrying andRTG Lifting.

Scenario 1: RTG Gantrying

Case I: RTG retrieving boxesIn order to compute RTG repetitions, we need to count how many times RTG pass a point along a run

way in a block. If a uniform distributed storage block (i.e., boxes in a block have equal dwell timesaveragely) is assumed, it is easy to see that the worst point at which the maximum repetition occurs is atthe middle point along the run way. The following argument is used to compute the RTG repetitions atthe middle point for the case that RTG takes boxes out of a block, as shown in Figure 3-9.

LH

W


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Figure 3-9 illustration of RTG repetitions

When taking a box out of a block, there is a chance that the RTG will cross the middle point. This willhappen only when the RTG and the box are at the different side of the block. The probability of this eventis:

PG = Prob( RTG cross the middle point)= Prob(RTG at the left and box at the right) + Prob(RTG at the right and box at the left)= + = 0.5 (under the assumption of uniform distribution)

This is the probability that one operation of RTG will cross the middle point. The number of times theRTG cross the middle point is obtained by multiplying the probability with the number of operations peryear. During peak/semi peak times when there is more than one truck waiting for a box, the Operator mayget the closest box first, creating an efficiency factor (C8). This factor will always be less than one, butcan be adjusted according to port productivity. The busier they are, the more trucks are waiting, whichmeans the potential for efficiency raises, causing the factor to go down. Thus, the load repetition for RTGgantrying when receiving boxes is given by:

Efficiency factor Prob( RTG cross the middle point) (Number of operations/year)= C8 PG (365/DW) SU H W L / C4/C9

Case II: RTG receiving boxesWhen putting a box into the storage area, there will be less gantry reps than taking out a box, because theRTG Operator can put the box in the first available space. Thus, the formula for the case of retrieving

boxes to compute load repetitions may still be used since that is the worse case.

Combining Case I and Case II, we obtain the following formulas.

TruckL/2 L/2

The middle point along the run way,

where the maximum repetition occurs.


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Given:


DW = assumed average container dwell time in days

C4 = TEUs per lift (typical number of TEU per lift between 1.7 to 1.85)

C5 = trips per box (2 for RTG area)

C7 = number of sides (1 for a RTG setup)

C8 = efficiency factor (1: inefficient, 0.5: efficient, .25: very efficient)

C9 = number of RTG cranes working stack

L = length of the stack in TEUs

W = width of the stack in TEUs

H = height of the stack in TEUs

PG = Probability that an RTG crosses the worst point along the run way (1/2 for a uniform

distributed storage block)

We have:

Truck Load Repetitions = C5 C6 (365 / DW) SU L H W / C4 (3-5)

RTG Retrieval Load Repetitions (retrieving boxes) = C8 PG (365/DW) SU H W L / C 4/C9 (3-6)

RTG Storage Load Repetitions (receiving boxes) = same as (3-6) (3-7)

Scenario 2: RTG Lifting

Calculation methods are as follows:

The RTG repetitions when lifting can be computed by counting the boxes will go into and out of a bay.For each box, there will be one lift in and one lift out (C5 = 2). Thus, we have:

RTG Lifting Repetitions = C5 C6 (365 / DW) SU H W (3-8)


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3.6 Equipment Weight Distribution and Wheel Loads

Weight distribution and wheel load calculations are stated as seen in the British Ports Associations 1982heavy duty pavement manual (refer as British Manual from here on). This section summarize the

formulas used to calculate wheel loads for RTG, side or top picks, and yard trucks.

3.6.1 RTG

For RTG, when the container is at the right-most (or left-most) position, the weight distribution (as shown

in Figure 3-10) gives the maximum wheel loads.

A1 = 1 (xc/ x2) (3-9)

A2 = xc/ x2 (3-10)

W1 = fD ( ( (WcA1) / M ) + U1 ) (3-11)

W2 = fD ( ( (WcA2) / M ) + U2 ) (3-12)

Where:

W1 = wheel load of engineless side

W2 = wheel load of engine and container side

Wc = weight of container

x2 = distance from side 1 to side 2 (wheel to wheel)

xc = distance from side 1 to the center of the lifted container when it is fully trolleyed to side

2 (engine side)

U1 = unladen weight of gantry crane on each wheel of side 1

U2 = unladen weight of gantry crane on each wheel of side 2

A1, A2 = weight distribution ratios

M = number of wheels on each side

fD = dynamic factor (See British Manual for values, typically 1.0, 1.1, and 1.2.)


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Figure 3-10 Weight distribution RTG

3.6.2 Side or Top Pick

The weight distribution for the side or top pick is as shown in Figure 3-11. We have:

A1 = -x2 / ( x1 x2) (3-13)

A2 = -x1 / ( x2 - x1) (3-14)

B1 = ( xT - x2 ) / ( x1 x2 ) (3-15)

B2 = ( xT -x1 ) / ( x2 - x1) (3-16)

W1 = fD ( (WcA1) + (WTB1) ) / M (3-17)

W2 = fD ( (WcA2) + (WTB2) ) / M (3-18)

W1 W2

x2

xc

Wc


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Where:

W1 = front wheel load

W2 = rear wheel load

Wc = weight of container

WT = weight of vehicle

x1 = distance from container center to front wheels

x2 = distance from container center to rear wheels

xT = distance from container center to lifts center of mass

A1, A2, B1, B2 = weight distribution ratios

M = number of wheels on the respective axle (usually 2 for rear, and 4 for front)

fD = dynamic factor

Figure 3-11 Weight distribution Top Pick

Wc

W1WT

W2

x2

xT

x1


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3.6.3 Yard Trucks

The weight distribution is as shown in Fig

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Port Pavement Design Guide