GB2411631A

GB2411631A - Shock absorbing girder for supporting a railway vehicle body

Info

Publication number: GB2411631A
Application number: GB0404521A
Authority: GB
Inventors: Mirko Loeber; Peter Trotsch; Federic Bernhard Carl; Sieghard Schneider; Nino Sifri
Original assignee: Bombardier Transportation GmbH
Current assignee: Alstom Transportation Germany GmbH
Priority date: 2004-03-01
Filing date: 2004-03-01
Publication date: 2005-09-07
Also published as: GB0404521D0

Abstract

The girder (8) defines a longitudinal axis and comprises at least two rigid regions (42,44), each of the rigid regions (42,44) having a closed cross-section, and at least one deformable region (40) located longitudinally between the two rigid regions (42,44), the deformable region (40) comprising an open cross-section, wherein the longitudinal crumpling resistance of the deformable region (40) is substantially smaller than the longitudinal crumpling resistance of the rigid regions (42,44). The girder (8) supports a body end section (16) and a longer main section (14), the deformable region (40) being adjacent to the end section. The open cross-section of the deformable region (40) is provided by a slit or aperture in one girder wall.

Description

2411 631

SHOCK ABSORBING GIRDER FOR RAIL VEHICLES

The present invention relates to a shock absorbing girder for supporting the car body of a railway vehicle, and a railway vehicle having such a shock absorbing girder.

In the present specification, references to a "railway vehicle" or "railway vehicles" is not to be taken to be limited to a particular type of transport, but are to be interpreted as embracing all types of vehicles, including but not limited to rail vehicles, trains, passenger carriages, cargo carriages, locomotives, trams, guided vehicles and 0 transports, and the like. The terms "railway vehicle" and "railway vehicles" are used herein to refer to this generic group of items, unless otherwise specified.

In EP0621416B1, an energy absorbing element is disclosed which can be attached to the ends of a chassis for absorbing, by deformation, impacts in the longitudinal direction of the chassis. The energy absorbing element comprises a thin plate construction having a cross sectional shape of two inverted triangles with a common vertex, wherein the surfaces of the thin plates are stamped to provide deformable regions that collapse longitudinally in a concertina fashion in an impact with an obstacle. Similarly, in FR2698932 an energy absorbing element is disclosed comprising thin plates having a closed cross section of two trapezoids with a common edge. Open sections within the sides of the thin plates provide deformable regions such that the energy absorbing element collapses longitudinally, in a concertina fashion, in an impact with an obstacle.

2s However, the energy absorbing elements of EP0621416B1 and FR2698932 cannot be applied to bear the structural and operational loads of a railway vehicle. This is because they are only cormected in addition to buffers and the like, for additional energy absorption. Further, there is a high likelihood that these designs would in fact deform under the normal operating loads that the various structural girders of the car body experience.

ceeeëeeces Accordingly, there is a need for a load bearing girder that supports a car body of a railway vehicle, where the girder controllably deforms and collapses on impact with an obstacle.

According to the invention there is provided a shock absorbing girder for supporting the car body of a railway vehicle, the shock absorbing girder defining a longitudinal axis and comprising at least two rigid regions, each of the rigid regions having a closed cross-section, and at least one deformable region located longitudinally lo between the two rigid regions, the deformable region comprising an open cross- section, wherein the longitudinal crumpling resistance of the deformable region is substantially smaller than the longitudinal crumpling resistance of the rigid regions.

The shock absorbing girder is designed to bear some, if not all, of the loads experienced by a car body and/or chassis in the normal operations of a railway vehicle. The girder is designed such that it will not deform when placed under these stresses. However, progressive and controlled deformation of the girder, due to the deformable regions, also known as yieldable regions that are defined similarly as the deformable regions, will occur in abnormal operating conditions such as an impact with an obstacle. This minimises the occurrence of catastrophic structural collapse of the car body and/or chassis and improves the safety, for the occupants, of the railway vehicle. Further, although the longitudinal crumpling resistance of the deformable region is substantially smaller than the longitudinal crumpling resistance of the rigid regions, the rigid regions may also progressively deform, by longitudinal crumpling once the deformable regions have fully deformed.

Furthermore, the girder may have a single-cell and/or a multi-cell profile for the conveyance of loads that mainly act in the girder's longitudinal direction. The girder may comprise at least one deformation region (also known as a yieldable region or defined segment) comprising limited dimensions of one or more open sections, (also known as apertures, open profile sections), with the girder having an open section in the surrounding area.

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Preferably the at least one deformation region comprises at least one open section defining at least one hole. The open section provides a controlled deformation, in the form of crumpling and/or buckling, to absorb the impact of an obstacle. As well, the removal of material comprising the open section reduces the weight of the railway vehicle. Further, as the open sections are capable of crumpling and/or buckling they can be designed so that deliberate instabilities such as crumpling are caused in the plastic and/or the elasto-plastic area of the deformation region. This causes deformation of the girder as a whole in abnormal operating conditions and ensures, lo between the start of the deformation and the point of maximum longitudinal force of the impact, that only a small increase in power levels is registered. The deformation may be further controlled by dovetailing the wall thickness and width of the open sections such that longitudinal crumpling and/or buckling or the girder is achieved.

Preferably the open section has at least one longitudinal dimension and at least one perpendicular dimension that is substantially smaller than the longitudinal dimension. The shock absorbing girder has the ability to absorb an impact in the longitudinal direction by deformation due to longitudinal crumpling of the deformation region. Further, the length of the deformation regions and/or the open section can be advantageously set at a minimum of one natural crumpling (or buckling) wavelength of the open section. This may give the deformation region the least crumpling (or buckling) resistance.

Preferably the longitudinal crumpling resistance of the deformable region is at least a factor of to smaller than the longitudinal crumpling resistance of the rigid regions.

The deformable region of the shock absorbing girder is guaranteed to deform before any rigid region of the shock absorbing girder deforms. This also ensures that the shock absorbing girder still keeps its loadbearing capacity under normal operating conditions. The shock absorbing girder may give sufficient stability and stiffness to the frame-based structure of the vehicle so that it can withstand the operational static and dynamic stresses, but also having longitudinal flexibility so that whenever normal stress levels are exceeded a controlled deformation is achieved.

e. e. c: e.: be: e:e c. :: :: , b b In abnormal operating conditions, such as an impact with an obstacle, the deformable region will initially deform progressively, accompanied by axial folding failure, until total crumpling, buckling, and/or compression is reached. The deformation can then s encroach on the neighboring areas, such as the rigid regions, of the unaffected girder.

This then constitutes a start to the deformation of the rigid regions, which have a closed cross section, without causing significant new trigger force peaks. Further, this combination of an open deformation region, and the rigid region provides a girder with two stages of deformation. The open section is capable of crumpling lo and/or buckling first, at a lower power level or impact force, then the closed cross section of the rigid region deforms at a higher power level or impact force.

The point and direction of crumpling (or buckling) is predetermined. The trigger point, the point at which deformation begins, can be further predetermined by a geometrical notch in the power now of the girder, which generates the excess load necessary for triggering at a load level. As well, the girder may be suitable for welded composite hollow box girders as one can achieve by addition of the open sections that the areas exposed to maximum strain will be along the rim of the open sections in the base metal and not at the edges of the hollow box girder around the welding seams.

The shock absorbing girder has different functions, some of which are the conveyance of operational loads, identification of an overload situation or abnormal load due to an impact, and subsequent deformation accompanied by energy absorption. These functions are united in one structural component where there are no movable parts.

According to a second aspect of the invention, there is provided a railway vehicle comprising a car body deeming a longitudinal direction and comprising a first end section and a main section adjacent to the first end section, the main section being substantially longer than the first end section; and at least one shock absorbing girder according to any of the variations as described herein and/or above, wherein the cecceë shock absorbing girder extends in the longitudinal direction of the car body substantially from the first end section for supporting at least the main section of the car body, wherein the at least one deformation region is located adjacent to the first end section. The car body and/or chassis can controllably deform, upon an impact with an obstacle on the first end section. This further minimises the occurrence of structural overloads and catastrophic collapse of the car body and/or chassis.

Preferably a second end section is adjacent to the main section, the second end lo section opposing the first end section, wherein the at least one shock absorbing girder further comprises at least two further rigid regions, and at least one further deformable region located longitudinally between the further rigid regions, wherein the further deformable region is located adjacent to the second end section. A shock impact can occur at either ends of the car body and/or chassis of a railway vehicle. It is advantageous to have at least one further deformation region within the shock absorbing girder adjacent to the second end section to enable the controlled deformation and/or collapse of the car body and/or chassis from this end of the railway vehicle. The girder can be applied to all kinds of rail vehicles and is particularly suitable for girders in the undercarriage level (such as the outside and central longitudinal girders). It can also be advantageous for this girder to be used in other portions of the vehicle's structure and/or frame.

According to a further aspect of the invention there is provided a method for modifying a railway vehicle comprising a shock absorbing girder as described herein. The methods of installation may range from installing at least one shock absorbing girder at the time of manufacture into the chassis of the railway vehicle.

Other methods such as retrofitting existing railway vehicles, with at least one shock absorbing girder can be applied so that older railway vehicles can also benefit, from improved safety and costs of repair and maintenance. This is advantageous since the shock absorbing girder can be incorporated into other existing vehicle structures without requiring additional structural space or adding more weight to the vehicle.

Further the installation and construction of the shock absorbing girder is cost . . a-e::: ec. ee.

effective as there are no movable parts and assembly is easy for both production and operation.

Other advantages and features of the invention will become more apparent from the following description of a specific embodiment of the invention given as a non- restrictive example only having reference to the accompanying drawings, in which: Figure la provides a perspective view of a first aspect of the present lo invention.

Figure lb provides a perspective view of another aspect of the present invention.

5 Figure to provides a perspective view of a further aspect of the present invention.

Figure 2a provides a cross sectional view of the first aspect of the present invention.

Figure 2b provides a cross sectional view of the aspect of the present invention given in figure lb. Figure 2c provides a cross sectional view of the aspect of the present 25invention given in figure I c.

Figure 3 provides a longitudinal sectional view of a railway vehicle of a second aspect of the present invention.

30 Figure 4 provides a longitudinal sectional view of a railway vehicle comprising a another aspect of the present invention.

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Referring to figures la, lb, and to there is shown various portions of a shock absorbing girder 8 defining a longitudinal direction. The deformable region 40 progressively has less resistance to defonnation compared to the two rigid regions 42 and 44 in figures 1 a, lb and l c.

Figure la shows a first aspect of the shock absorbing girder 8 having a rectangular cross section, wherein the deformable region 40 comprises a slit such that the longitudinal dimension of the slit is greater than the transverse dimension of the slit.

lo The resistance to deformation of the deformable region 40 is marginally less than the rigid regions 42 and 44.

Figure lb shows another aspect of the shock absorbing girder 8, wherein the deformable region 40 comprises an open section. The longitudinal dimension of the open section is greater than the transverse dimension of the open section. However, the transverse dimension is now greater such that the open section is not considered a slit as in the second aspect of the shock absorbing girder 8 in figure la. The deformable region 40 definitely has a lower resistance to deformation than the rigid regions 42 and 44, and a lower resistance to deformation than the deformable region 40 of figure la.

Figure lo shows a further aspect of the shock absorbing girder 8. However, the deformable region 40 has a lower resistance to deformation compared to the rigid regions 42 and 44, and compared to the deformable regions of the second and third aspects of the shock absorbing girder 8 in figures la and lb. The open section of the deformable region 40 is such that the transverse dimension extends the length of an edge of the rectangular cross section.

Referring now to figures 2a, 2b, and 2c there are shown various cross sections of the aspects of the shock absorbing girder 8 defined in figures 2a, 2b, and 2c. Shown are the open cross sections of the deformable region 40 as the lateral dimension of the open section increases. Also shown are dashed lines of the deformation, by . Be: q:7 #: at: c . ce, longitudinal crumpling or deflection, of the corresponding sides of the shock absorbing girder 8. Changing the shape of the open section allows various modes of deformation to occur.

The different sizes and applications of railway vehicles 2, for example light rail vehicles through to freight locomotive rail vehicles, means that size of the open section within the deformable region 40 of the shock absorbing girder 8 should be selected accordingly. This ensures that the best shock absorbing girder 8 can be l o fitted to each railway vehicle 2 without deforming under normal operating conditions of that railway vehicle 2. However, the shock absorbing girder 8 is able to deform under abnormal loading conditions such as on impact with an obstacle.

Referring now to figure 3, there is shown a railway vehicle, gencra]ly indicated as 2.

The railway vehicle comprising a first and second end section, 16 and 18, which are attached to a main section 14. The car body of the railway vehicle 2 comprises these sections 14, 16 and 18, which are supported by means of a shock absorbing girder 8.

The railway vehicle 2 of figure 3 includes a chassis or vehicle base 4 being supported on one or more bogies 6 and which further comprises at least one shock absorbing girder 8. The vehicle base 4 and shock absorbing girder 8 support a body structure including main walls 10 extending upwards towards the roof]2, (only one wall is shown in the longitudinal section of figure 1), wherein the walls 10, the roof 12, and the body structure are referred to as the main section 14 which defines a longitudinal direction. Connected to one longitudinal end of the main section 14 is a first end section 16, which could be but is not limited to a vehicle driver's cabin. Similarly, a second end section 18 is connected to the opposing longitudinal end of the main section 14.

The first end section 16 includes at least one first doorframe 20, which can include a door and/or escape exit for authorised personnel. The first doorframe 20 is positioned adjacent to the connection between the first end section 16 and the main |:' :. lt.

: section 14. At least one first side window 22 is positioned between the first doorframe 20 and the first front 24 of the first end section 16. The second end section 18 may be defined in a similar fashion for at least one second doorframe 30, at least one second side window 32 in relation to a second front 34.

The shock absorbing girder 8 substantially extends, longitudinally, the length of the railway vehicle 2. There are two rigid regions 42 and 44 within the shock absorbing girder 8 between these regions 42 and 44 is disposed a first deformable region 40.

ID The first deformable region 40 includes an open cross section where the longitudinal crumpling resistance of the first deformable region is substantially less than the longitudinal crumphng resistance of the two rigid regions 44 and 42. The open cross section is formed by an open section in the shock absorbing girder 8, and is defined by a hole. The open section having at least one longitudinal dimension and at least one transverse dimension such that the longitudinal dimension is longer than at least one transverse dimension.

The first deformable region 42 is positioned within the shock absorbing girder 8 near the first front 24, and substantially adjacent the first end section 16 and aligned with the first side window 22. Similarly, there is a further two rigid regions 52 and 54 between which a second deformable region 50 is disposed. The second deformable region 50 is similarly defined as the first deformable region 40, in relation to the second end section 18, second front 34 and second side window 32.

The first deformable region 40 of the shock absorbing girder 8 provides energy absorption, by a longitudinal crumpling effect, when the railway vehicle 2 collides with an obstacle impacting the first end section 16. The deformable region 40 is designed not to deform under normal operational loads such as, but not limited to, pulling or pushing loads. Similarly, the second deformable region 50 of the shock absorbing girder 8 provides energy absorption for obstacles impacting the second end section 18. This energy absorption reduces the impact energy that is transferred to the main section 14, increasing the likelihood that the main section 14 remains intact :::: : : .: .' after a collision. This allows the repair or replacement of the first and second end sections 16 and 18 while re-using the main section 14 of the railway vehicle 2.

Referring now to figure 4, with the reference numerals of figure 3 being re-used accordingly. Shown is another aspect of the shock absorbing girder 8 disposed within a railway vehicle 2, wherein the first end section 16 is a deformable vehicle cabin. The first end section 16 comprises a rigid section 60 and a deformable front section 62. As in figure 3, a first doorframe 20 is positioned within the rigid section lo 60, where the doorframe 20 may be made of material with the same stiffness as the rigid section 60. Further, the rigid section 60 includes rigid pillars 64 which connect with the first end section's 16 base and roof. The rigid section 60 defines a survival space for the occupants of the first end section 16.

There is a front section 62, where an impact is to be expected, the front section 62 is connected in front of the rigid section 64. A shock absorbing girder 8, that may extend along the length of the railway vehicle 2, forms and/or supports of the front section 62, and may also support the main section 14. The front section 62 comprises at least one deformable region 40, 70, 72, 74, 76, and 78, where the deformable regions have a lower resistance to deformation compared to the rigid section 60 and rigid regions 42 and 44.

The front section 16 comprises a plurality of frame members, including but not limited to 8, 80, 82, 84, 86 88 and 90. These frame members, including but not limited to, 8, 80, 82, 84, 86, 88 and 90 can be made of but not limited to, steel, mild steels, fibreglass, aluminium, carbon fibre, laminates thereof, or any other such material, subassembly or component that is suitable for the purpose of the front section 62.

In the base of the front end section] 6, among other frame members of the front section 62, is at least one shock absorbing girder 8. The shock absorbing girder 8 includes at least one elongated, e.g. rectangular or oblong, open section, which e::e. :e:. a..

. . . defines the base deformable region 40. The base deformable region 40 has a smaller resistance to deformation than the two rigid regions 44 and 42 on either side of the base deformable region 40. The position of the base deformable region 40 is substantially aligned with the first side window 22 of the f rst end section 16.

Connected adjacent to the rigid region 42 of the shock absorbing girder 8, is a headstock frame member 80. The headstock frame member 80, extends along the transverse dimension between the sides of the front end section 16. It also supports a 0 front portion of the front section 62 and further supported on the headstock frame member 80 can be sub-assemblies including but not limited to buffers, couplings, cowcatchers, bull-bars, anti-climbing devices or further energy absorbing elements.

On top of, and/or adjacent, to the headstock frame member 80 is connected at least one lower frame member 82 which inclines at an angle towards the front of the front section 62, wherein the top of the lower frame member 82 is disposed centrally between the base and roof of the front end section 16. A lower deformable region 70 is positioned near the base of the lower frame member 82.

Connected adjacent to the top of the lower frame member 82 is a central frame member 84, which extends along the transverse dimension between the sides of the front end section 16. Adjoining the top of the lower frame member 82 is at least one upper frame member 86. Substantially near the adjoining region of the upper frame member 86 and the lower frame member 82 is a central deformable region 72. In this instance, the central deformable region 72 is positioned above the connection of the central frame member 84 and the lower frame member 82. The central deformable region 72 having two essentially opposing non-intersecting semi-circular sections removed.

The upper frame member 86 may be composed of a material with a high stiffness.

At least one upper deformable region 74 is located either adjacent to the top of the upper frame member 86, or within the top of the upper frame member 86.

cesceceeeece Adjacently connected to either the upper frame member 86, or the upper deformable region 74 is at least one first roof frame member 88. The first roof frame member 88 extends towards the rear of the front end section 16 and above the rigid section 60, finally connecting to the main section 14. A first roof deformable region 76 is located near the end of the roof frame member 88 that is adjacent to the upper frame member 86 or the upper deformable region 74. Above and adjacent to the first roof frame member 88 is a second roof frame member 90 wherein disposed, and adjacently aligned to the first roof deformable region 76 is a second roof deformable lo region 78.

The first roof deformable region 76 includes at least two longitudinally spaced holes, which act as a hinge, by bending, folding, or buckling to provide energy absorption by rotation through an axis of rotation located between the two holes. As well, the IS first roof deformable region 76 provides a longitudinal energy absorption mechanism, in the fond of a crumpling effect. The second roof deformable region 78 comprises semi-circular corrugations removed from the top and/or lower edges, and/or surfaces of the second roof frame member 90. The second roof deformable region 78 performs energy absorption through crumpling or buckling to further minimise the transmission of impact energy to the rear of the first end section 16.

In the event of an impact by an obstacle to the front of the front end section 16 of the railway vehicle 2 given in figure 4 then the front section 62 will controllably collapse to absorb the kinetic energy of the impact. In a medium frontal collision with a flat faced obstacle the lower, central, upper deformable regions, respectively 31, 36, 38 do not fully deform since the obstacle is flat-faced and does not penetrate into the front end section 16. However, the deformable region 40 in the shock absorbing girder 8 and the first and second roof deformable regions 76 and 78 will absorb the kinetic energy of the impact generally by crumpling or buckling in the longitudinal direction.

eJe. .e a. e. .e In a collision with a high contoured obstacle that mpacts at a height may be centrally between the front end section's 16 base and roof wherein the deformable regions 31, 36, 38, 40, 76 and 78 will co-operate to adapt to the contours of the obstacle and absorb the kinetic energy of the impact. The shock absorbing girder 8 and the roof frame members 88 and 90 typically undergo a rotational and/or bending deformation, such that the members rotate inwards to the front end section 16 about the shock absorbing girder's 8, first and second roof deformable regions 40, 76 and 78 respectively. Simu] taneous]y, as the obstacle impacts centrally, most likely, against lo the upper frame member 86 the central deformable region 72 will deflect towards the interior of the front end section 16 and undergo a rotational and/or bending deformation. The obstacle pushes the central deformable region 72 further into the front end section 16. However, the upper frame member 86 prevents the obstacle from actua]]y penetrating and/or puncturing the front end section 16. This is where the full surface area of the front end section 16 begins to dramatica]]y absorb the kinetic energy of the impact, eventually stopping the forward momentum of the obstacle.

Simultaneously, the lower, upper, first and second roof deformable regions 70, 74, 76 and 78 and the shock absorbing girder's deformable region 40 undergo further rotational deformation absorbing the energy of impact as much as possible. The remaining impact energy is also transferred, by compression of the lower and upper deformable regions 70 and 74 into the shock absorbing girder 8 and the first and second roof frame members 88 and 90. This remaining impact energy is dissipated within the shock absorbing girder's 8 and roof deformable regions 40, 76 and 78 by a longitudinal compression. The kinetic energy of the impact is effectively transferred away from the occupants of the front end section 16. The front section 62 will adapt to the shape of the obstacle and absorb as much kinetic energy as possible by the defonnation of the central deformable region 72 and the other deformable regions.

During the impact the occupants of the front end section 16 are pushed back, by the deforming front section 62, into the survival space located in the rigid section 60.

e.e: ::: . . . . . Alternatively, the occupants can be pushed towards the survival space by a drivers console that may be within the front section 62 of the front end section 16, or they can take refuge within the survival section.

The safety of the railway vehicle 2 has improved since the kinetic energy of an impact is absorbed by the shock absorbing girder 8 and/or deformable vehicle cabin and in most circumstances will leave the main section 14 intact. This would also improve the costs involved in repairing and/or replacing the shock absorbing girder 8 lo and/or the deformable vehicle cabin and re-using the main section 14, instead of replacing the railway vehicle 2. While the present invention has been shown and described with reference to

particular illustrative embodiments it will be understood by those skilled in the art IS that various changes in form and detail may be made without departing from the scope of the invention as defined in the appended claims.

Claims

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1 - A shock absorbing girder (8) for supporting the car body of a railway vehicle (2), the shock absorbing girder (8) defining a longitudinal axis and comprising at least two rigid regions (42,44), each of the rigid regions (42,44) having a closed cross-section, and at least one deformable region (40) located longitudinally between the two rigid regions (42,44), the deformable region (40) comprising an open cross-section, wherein the longitudinal crumpling lo resistance of the deformable region (40) is substantially smaller than the longitudinal crumpling resistance of the rigid regions (42,44).

2 - The shock absorbing girder (8) of claim 1, wherein the at least one deformable region (40) comprises at least one open section defining at least one hole.

3 - The shock absorbing girder (8) of claim 2, wherein the open section has at least one longitudinal dimension and at least one perpendicular dimension that is substantially smaller than the longitudinal dimension.

4- The shock absorbing girder (8) of any preceding claim, wherein the longitudinal crumpling resistance of the deformable region (40) is at least a factor of 10 smaller than the longitudinal crumpling resistance of the rigid regions (42,44).

5 - The shock absorbing girder (8) substantially as hereinbefore described having reference to figure 1, figure 2a, figure 2b, figure 2c, figure 3a, figure 3b, figure 3c, or figure 4.

6 - A railway vehicle (2) comprising: - a car body defining a longitudinal direction and comprising a first end section (16) and a main section (14) adjacent to the first end es:'.e ee. :. I. ..

section (16), the main section (14) being substantially longer than the first end section (16); and at least one shock absorbing girder (8) according to any of claims 1 to 5, wherein the shock absorbing girder (8) extends in the s longitudinal direction of the car body substantially from the first end section (16) for supporting at least the main section (14) of the car body, wherein the at least one deformation region (40) is located adjacent to the first end section (16).

lo 7- The railway vehicle (2) of claim 5, wherein a second end section (18) is adjacent to the main section (14), the second end section (18) opposing the first end section (16), wherein the at least one shock absorbing girder (8) further comprises at least two further rigid regions (52,54), and at least one further deformable region (50) located longitudinally between the further rigid regions (52,54), wherein the further deformable region (50) is located adjacent to the second end section (18).

A method for modifying a railway vehicle (2) comprising installing the shock absorbing girder (8) of any of claims 1 to 5.