Requirements and Constraints by xiuliliaofz

VIEWS: 1 PAGES: 4

									1 Requirements & constraints
Before starting the designing it is important to identify the requirements and
constraints of the concept to be designed. In the first part of this report the concept of
river-sea shipping is being proposed. This concept originates from the market and/or
product in these markets. In this case first the concept of river sea shipping is chosen
followed by the decision for transportation of the vehicles. In chapter four is stated that
the river-sea shipping concept should consist of a ship and a service, which together can
be characterized as the design of the concept. The design will be part of the environment
it functions within, so designing the ship and the service will be performed taking the
environment into account. Figure 8.1 elaborates on this in a schematic way.
Requirements originate from the market and from the product and are being imposed
on the concept as a whole. All of these requirements imposed can be specified towards a
specific requirement on ship or service. Constraints are mostly imposed by its
environment. Thereby most important characteristic of a constraint is the fact that it is
something that must dealt with in the design, but the designer cannot influence these
constraints.
This chapter deals first with the different requirements imposed on the design of the
ship and the service of the river-sea shipping concept. Next to this the constraints on the
design are identified.

 Market/Products                                   Concept




                                   Ship                               Service



                                                                            Design

                                                                         Environment
Figure 8.1: Requirements and constraints during the designing phase

1.1 Requirements
It is essential to identify the requirements that should be imposed on design of the ship
and the service. With identifying requirements it will be possible to make clear what the
specific need is and how a requirement should be stated to describe the specific need.
When the requirements are identified designing can be initiated. During the designing
process the requirements should be actively involved so the design should fully fulfill all
requirements stated before. After the design these requirements makes it possible to
check if the final design fulfills the identified requirements.
Depending on the level detail it is possible to indentify different requirements:
requirements on the highest level of the concept (the ship should float), but also on the
tiniest sub-system of the ship (the light should be switched on or off). This paragraph
will handle the requirements on a concept level and how these requirements influence
the design of the ship and service. For a complete overview of the requirements
identified with this application of river-sea shipping see appendix X.X.
Damage on vehicle should be minimized


Loading and unloading should be done in minimal time


Availability should be maximized


Reachebility in the corridor should be maximized


The concept should be highly costs competing with the current ways of
transport


The concept should be highly time competing with the current ways of
transport


Pushing vessel should be changed when going sailing on sea and vice versa


The concept must be durable

Iets van conclusive dat alles van elkaar afhangt en dat er een afweging gemaakt moet
worden tussen time/costs/damage


1.2 Constraints
Constraints are just like requirements very important during design. Most constrains on
the ship design are imposed by natural, physical characteristics of the river that is being
used for navigating. On the contrary no constraints on the ship design imposed by the
sea on the route of transport are found. Another group of constraints have a legal
character where by a distinction can be made between legal constraints on the ship and
the service design. Last group of constraint originates from the market: these are mostly
imposed on the service design. These three groups of constraints will be elaborated in
the following paragraphs.

1.2.1 Physical constraints
For a ship that is navigating on a river, there are a couple of physical boundaries that
limit the choice of parameters of a ship. In general these boundaries limit the
dimensions of the ship. For the sea part of the transport service, there are boundaries as
well, but they are irrelevant when compared to those of the river. The following table
shows the boundaries that are valid for the Rhine, up to Bonn.
Parameter                      Limit          Caused by
Breadth                        11,40          Only for Dortmund, breadth of a lock
Draught                        3,5            Depth of the river
Free height                    9,2            Fixed bridge
Table 1: Physical boundaries for the Rhine, up to Bonn
1.2.2 Legal constraints
The constraints of the design follow from rules and regulations of governmental
institutions that have a legal position in the operational area. For the river Rhine that
are the Dutch and German government and for the part on the North Sea that is the
International Maritime Organization (IMO).
The Dutch and German legal requirements for inland navigating ships are aligned, so
there are not a lot of differences. The Dutch regulations are issued in the “Rijnvaart
politie regelement” and “Binnenschepenwet”. Besides a lot of specific rules, there are
some rules that really bound the solution space. Table 2 shows these regulations, the
columns show the type of inland ship it involves, the parameter or item it involves and
the limits.
Type of ship        Parameter             Limit
Inland              Length                135m
                    Breadth               22,8m
                    Line of sight         Empty ship, 50% stores 250m from wheelhouse
                    Stability             GM minimum: 0,5m or 1m in case of unlashed
                                          containers
                    Minimum speed         Capable of 13km/h through the water
                    Freeboard             0,15m, 50cm extra if no hatch-covers are applied
                    Crash bulkhead        Between 0,04*L and 0,04*L+2 meters
Inland L>110m       Propulsion            Double configuration
                    Double bottom         600mm height, throughout the length
Push barge          Crash bulkhead        Not necessary when barge is strong enough
                    Length of convoy      269m upstream, 193 downstream, max barge length
                                          110m
Push boat           Length                40m
                    Engine power          Max 4500kW
Table 2: Rules and regulations for Rhine Navigation, up to Mainz

Vaartijdenwet

Legal constraints voor op zee uitwerken als loadunit gekozen is.

1.2.3 Market constraints
Origin and destination of vehicles
Production volumes

1.2.4 Requirements
There are three parameters that have the most influence on the operational profile: the
speed, the capacity and the ability to load and unload autonomously. The first two are
also bounded by the constraints and shown before.

The maximum size of the box the ship has to fit in under water is 135m*22,8m*3,5m.
Combined with a fleet average block-coefficient of 0.8, the maximum displacement of
the ship will around 8600 tons. Assuming that for cost effectiveness on the sea, the scale
advantages are very important, the ships size should be maximized. Especially the
length is very attractive to maximize, since the total resistance, and therefore fuel
consumption, is smaller for a longer ship than for a shorter one, everything else being
the same.
If it is decided to keep Dortmund as a possible stopover, the breadth needs to be
reduced to 11,4m which results in an extremely narrow ship that may suffer severe
stability problems. However, a ship with a breadth of 22,8 meters may have trouble with
accelerations due to sea-state.
Minimizing the structural weight, or lightweight, of the ship leaves a maximum cargo
capacity. Therefore innovations in construction of the vessel should be investigated.


Sailing a ship along a river has a lot of consequences for the design, a lot of requirements
and constraints are specifically determined by the fact that the ship has to be able to
navigate on the strict boundaries of the river. This paragraph will focus on shaping a box
in which the ship has to fit, together with the rules and regulations that apply on the
internal structure of the box. The requirements follow from the desired operational
profile and the constraints from rules and regulations of different governmental
institutions.

								
To top