Abstract: An impact energy absorption system for aircraft seats and the like, comprising seat mounting means, a seat movable between a first unloaded position and a second crash induced position, a deforming die and an additional set of die jaws connected to the seat mounting and defining an aperture of variable size, and a deformable rod having a shoulder connecting the seat to the mounting the rod passing through the deforming die and the variable die jaws. During crash induced movement of the seat between its two positions the rod is pulled through the deforming die and the die jaws to absorb impact energy by deformation of the rod. The aperture defined by the die jaws is variable being adapted to allow for self adjustment of the aperture size and respective impact energy absorbing capacity corespondent to the weight of the seat occupant.

Abstract: A deformation structure includes a hollow member and a tapered deformation member having a smaller diameter than the hollow member and arranged to be inverted into the hollow member in response to an applied force. The hollow member has a pleat-denting response to higher applied forces so that the pleat engages the surface of the inverted deformation member within the hollow member.

Abstract: A deformable, reinforced tubular door member for absorbing energy occasioned by an impact force exerted thereupon is disclosed, having a deformable tube having an open space therewithin, and a spiralled stiffening element positioned within the open space of the deformable tube and having a plurality of surface elements which are arranged such that when the impact force is exerted upon the tubular member, the elements exert a resisting force against the tubular member. In one embodiment, the stiffening element is a coiled or spiral spring. In another embodiment, the stiffening element is a strip which is twisted about its lengthwise axis so that the surface elements are arranged in a double helix. In a still further embodiment, the strip is twisted in order that it have one twist per centimeter.

Abstract: A fold-back deformation arrangement includes a deformation tube of plastically deformable material and a support arrangement with a fold-back surface engaging one end of the tube. The arrangement is designed so that relative angular motions between the fold-back surface and the deformation tube are possible without tending to buckle the tube.

Abstract: An impact attenuating device such as a truck mounted attenuator includes at least two cartridges, which are secured together by flanges and angled backing elements on adjacent portions of the upper and lower sheets of the cartridges. The forwardmost bay of the impact attenuating device includes stiffening elements on the lower surface and deformable elements which come closely adjacent to the lower surface of the impact attenuating device in order to urge an impacting vehicle with having a low bumper height upwardly, toward the center of the impact attenuating device. The end of the impact attenuating device initially struck by an impacting vehicle is covered by a resilient collapsible element having parallel pleats and recessed corners, such that the collapsible element can absorb low energy impacts without damage to the impact attenuating device.

Abstract: A system for arresting movement of an aircraft traveling off the end of a runway at high speeds. Rigid, friable, fire resistant foam boards, preferably phenolic foam, are connected to form a panel, and a plurality of layers comprised of stacked panels are adhered to a base surface. The panels are formed from unfaced foam boards, the compressive strength of the stack of boards being less than the force exerted by the landing gear of the aircraft to allow the boards to be crushed by the landing gear.

Abstract: A shock absorber is adapted to be disposed within a perforating gun string or within the tubing string above the perforating gun and includes an energy absorbing element adapted to absorb and store mechanical energy during detonation of the perforating gun and to permanently deform in response to the storage of the mechanical energy, the stored energy being released in the form of heat, and not in the form of kinetic energy. Therefore, following absorption of the mechanical energy by the shock absorber, no further expansion of the shock absorber is experienced. The shock absorber includes an inner housing, an outer hosuing, a connection for interconnecting the inner and outer housing, and a break up charge for breaking the connection and releasing the inner housing from the outer housing when the perforating gun is detonated whereby the shock absorber is as strong as the tubing string before the connection is broken and is flexible after the connection is broken.

Abstract: A guardrail extruder terminal for flattening a folded or W-beam guardrail and bending the guardrail to dissipate the energy of a vehicle impacting the end of the guardrail includes a feeder chute. The feeder chute is provided with an inlet in which the guardrail is positioned. The feeder chute extends into a terminal housing, and is in communication with an extruder or flattening throat. The flattening throat is of a smaller width than the feeder chute to flatten the guardrail. A bending member is also provided in the terminal to bend the guardrail in an curvilinear arc away from the impacting vehicle. Also included is a cable anchor releasably mounted on the guardrail. A cable extends from the cable anchor to a first post located at the end of the guardrail. The cable anchor includes lugs that release from the guardrail upon engagement of the extruder terminal with the cable anchor.

Abstract: Impact energy is absorbed by empolyment of a discrete elongate body of a ductile material arranged along a longitudinal axis to receive an axial impact force at a first end thereof along the longitudinal axis and apparatus arranged adjacent a second end of the body of ductile material for extrusion thereof, the body of ductile material being operative to transmit the axial impact force axially therethrough from the first end to the second end.

Abstract: A crushable, composite, columnar, self-stabilized structure for absorbing energy by progressively reacting compression forces along the axis of the structure. The compression failure initiates at one end and progresses to the second end of the stiffener in a controlled fashion in that at any cross section, the local compression strength at that point is less than the general stability strength of the remaining structure.

Abstract: A crash attenuator (10) includes a plurality of layers (22) of fibrous cellular material. Each of the layers is comprised of a plurality of hexagonal elongate cells fabricated of a fibrous cellulose material that has a longitudinal axis that is disposed horizontal to the ground such that the edge of the cell is directed toward the impacting vehicle. A flat sheet of fibrous material (24) is disposed between each of the layers to provide an energy dispersing surface. A rear impact plate (18) is disposed on the impacting end of the crash attenuator (10) and is fabricated from a soft metal. A front mounting plate (20) is disposed on the opposite end thereof and the two secured by tension cables (42). The exterior of the layers (22) is covered by sheets (26) and (46). Thereafter, a layer of moisture proof material (78) is disposed over the surface of the crash attenuator (10) to prevent moisture from entering the interior.

Abstract: A component which is to be installed for an absorption of energy with an ideal displacement-compressive force characteristic consists of a prismatic straight metal rod, which is long relative to its transverse dimensions and is adapted to inelastically buckle in the direction of the axis of its larger principal moment of inertia under an axially acting compressive load and is provided with spur teeth, which extend transversely to the longitudinal direction and are provided on at least one of the broadsides, which extend at right angles to the axis of the larger principal moment of inertia.

Abstract: This invention relates to a reinforcement member to be mounted internally in the doors of an automobile, and more particularly to the member comprising two parallel flat members and one or two corrugated members which connect said two parallel members in such a manner as to position the ridges of folds thereof perpendicular to the surfaces of the plate members. The reinforcement member is mounted internally in car doors. When the car receives an impact from the side of the door, the corrugated surfaces of the member can distribute the impact evenly by deforming themselves into a fan-like shape to thereby prevent the door from being abruptly folded at one point.

Abstract: There is disclosed a marine vessel which is particularly suited for mine hunting operations or the like because of improved survivability characteristics in the presence of multi-directed underwater transmitted excessive shock or vibration forces, such as are generated by a nearby exploding mine or the like. The ship is of the propeller driven type having a propeller shaft driving engine and gearbox unit mounted inboard of the vessel hull upon a rigid sled-like platform which in turn is resiliently supported relative to rigid structure of the vessel by spring means sandwiched therebetween. The spring means are of such nature as to resiliently yield in response to excessive compression, tension, shear or roll forces encountered from any direction. The spring means comprises an array of spaced apart spring devices, and back-up blocks of non-resilient compression-deformable material are provided in association therewith.

Abstract: A front end structure of a vehicle body includes a pair of front side members and a pair of bumper mounting brackets secured to front ends of the side members. A pair of shock absorbers are interposed between a bumper and the respective bumper mounting brackets to interconnect the same. The bumper mounting brackets are constructed so that a maximum compressive load thereof is smaller than that of the side members and larger than a maximum opposing force of the shock absorbers.

Abstract: A guardrail extruder terminal for flattening a W-beam guardrail and bending the guardrail to dissipate the energy of a vehicle impacting the end of the guardrail includes a feeder chute. The feeder chute is provided with an inlet in which the guardrail is positioned. The feeder chute extends into a terminal housing, and is in communication with a flattening throat. The fattening throat is of a smaller width than the feeder chute to flatten the W-beam. A bending member is also provided in the terminal to bend the guardrail in an curvilinear arc away from the impacting vehicle. Also included is a cable anchor releasably mounted on the guardrail. A cable extends from the cable anchor to a first post located at the end of the guardrail. The cable anchor includes lugs that release from the guardrail upon engagement of the extruder terminal with the cable anchor.

Abstract: A beam or girder in a side wall or door of a passenger motor vehicle and adapted to provide resistance to lateral collision has a compression flange thereof provided with openings in the form of bores and/or notches so that brittle fracture of the beam can be avoided when the elastic limit is exceeded.

Abstract: A contractible mine stopping adapted to be installed to extend as a vertical wall from the floor to the roof of a passageway in a mine, comprising a series of rows of substantially solid substantially non-compressible blocks of substantially fire-resistant material stacked one on top of another, and at least one row of contractible substantially fire-resistant block-like members adapted to contract without loss of structural integrity when the wall is subjected to a compressive load, as during a convergence of the floor and roof of the passageway. Each block-like member is preferably a hollow metal member which, when subjected to a compressive load, is adapted to contract heightwise of the member a distance corresponding to at least a major portion of the height of the member without loss of structural integrity of the member.

Abstract: An advanced dynamic impact extension module, used to protect occupants of vehicles from the adverse effects of extremely rapid deacceleration of a vehicle when the vehicle impacts an end of a concrete barrier wall is disclosed. According to the invention, a barrier wall is provided which has a structural concrete base and a channel portion adaptable to receive low strength reinforced concrete modules. The concrete modules are composed of three layers of crushable material of varying strengths. The first or lowest layer is composed of semi-crushable, higher strength concrete and which is adaptable to secure reinforcement and S-beam connectors. The second layer is lower strength material and the top layer is intermediate strength material. The second and top layer keep an impacting vehicle down and prevent ramping. The modules are arranged linearly beginning at a front end closest to the path of an oncoming vehicle and proceeding toward a back end proximate a roadside obstacle.

Abstract: A light weight, energy dissipation bumper system for protecting the columns of an offshore platform. A plurality of rows of crushable tubes are provided to dissipate collision energy through absorption without storing such energy. The tubes have a diameter to thickness ratio between 30 and 40 for mild steel providing neutral/positive buoyancy. The tubes may be easily replaced when their ability to protect the column to which they are attached to exhausted through flattening. The tubes may extend either axially along or radially outward from the column.

Abstract: A structure which resists dynamic forces, forming a mounting for a seat of an air transport craft and a seat having such a structure comprising front and rear feet, a front anchorage, an energy absorption device, and a stop mechanism. The front and rear feet are articulated at their upper ends on the seat framework, so that each can pivot about a horizontal and transverse pivot axle. The front anchorage comprises a joint having a traverse horizontal pivot axle, which allows the front foot to pivot forwards from its normal position about the joint pivot axle. The energy absorption device extends between the lower front anchorage and the upper part of the rear foot, but at a distance from the upper rear joint. The energy absorption device includes a stop mechanism for preventing the forward pivoting of the rear foot about its lower rear anchorage on the fixed structure of the craft.

Abstract: Several embodiments (10, 30, 80) of an energy absorption system are designed for permitting progressive collapse of the system by absorbing energy within the system. In one embodiment, a system (10) comprises conical bodies (12) separated by cables (20), which system progressively collapses through plastic deformation of compression members (16) cooperating with each cable (20). In another embodiment, a system (30) incorporates plastically collapsible compression members (44, 46, 48) which collapse progressively to permit the bodies (32) to move together. In another embodiment, a system (80) is provided where the progressive collapse is permitted by frictional sliding of a securing device (92) along a track (90) which permits bodies (82) to move together.

Abstract: An impact absorbing device is provided for a vehicle having a bumper. The device comprises an energy absorber having an axis along which it is reducible in length at a substantially uniform rate in response to an impact force to absorb the energy of impact. At last one bendable plate is secured between the vehicle frame and bumper adjacent to but spaced vertically from the energy absorber. When the bumper is impacted with a force at an angle to said axis, the plate will bend in a direction generally perpendicular to the axis and constrain the energy absorber to reduce in length along the axis and absorb the impacting force.

Abstract: A shock absorbing assembly having sections for controlling the modal deformation of collapse and capable of absorbing the dynamic energy of impact caused by the rapid deceleration of heavy masses is provided. The shock absorbing assembly has a plurality of arcuate steel sections sandwiched between steel plates with an elastomeric rubber compound secured to and covering at least one surface of one plate. Each of the arcuate steel sections are provided with a groove in its soffit.

Abstract: An advanced dynamic impact extension module, used to protect occupants of vehicles from the adverse effects of instantaneous deacceleration of a vehicle when the vehicle impacts an end of a concrete barrier wall is disclosed. According to the invention, a composite barrier is provided which has an upper, low density, crushable component and a lower, substantially non-crushable, base component. The height of the base component will increase from the front of the barrier to the back of the barrier, located proximate the end of the concrete barrier wall, so that a vehicle impacting the barrier will first crush the upper, low-density, crushable material. If a vehicle has sufficient impact force or velocity to crush the upper crushable front component of the barrier, the undercarriage of the vehicle will coact with raised non-crushable base components of the barrier in order to bring the vehicle safely to rest before it impacts the end of a concrete barrier wall.

Abstract: An anti-terrorist vehicle crash barrier includes side support structures, crushable energy absorbing aluminum honeycomb modules, and an elongated impact-resistant beam extending between, and at its opposite ends through vertical guideways defined by, the side support structures. An actuating mechanism supports the beam at its opposite ends for movement between a lowered barrier-withdrawn position in which a traffic-supporting side of the beam is aligned with a traffic-bearing surface permitting vehicular traffic between the side support structures and over the beam, and a raised barrier-imposed position in which the beam is aligned with horizontal guideways defined in the side support structures above the traffic-bearing surface, providing an obstruction to vehicular traffic between the side support structures. The beam is movable rearwardly in the horizontal guideways with its opposite ends disposed transversely therethrough upon being impacted at its forward side by an incoming vehicle.

Abstract: An impact skirt 16 for a radioactive waste material cask 10, each impact skirt fitting over the end of the cask and having portions 18 and 20 lapping the cask axially and radially, each skirt comprising a one piece, monolithic, member of a solid, soft, light metal material such as aluminum.

Abstract: A mounting system for a vehicle-mounted impact absorption box filled with a collapsible open cell network provides a lessened tendency for disintegration when subjected to the vibrations of the vehicle. The system contains a bolt surrounded by a region of transverse cells, with the bolt bonded to the cell walls and passing therethrough in a generally perpendicular direction. A further feature of the system is a pivot bracket constructed in two parts--a rigid portion and a pivot arm, the latter stabilized by springs which absorb torsional impulses on the arm arising from the vehicle vibrations. These two features work in conjunction with each other in reducing shock damage to the interior of the box, and thereby increase the life expectancy of the box as a whole.

Abstract: In e.g. a projectile launcher, an arresting sleeve (12) absorbs energy by deformation, which is necessary to arrest a piston (15) from which a counter-mass or a projectile is ejected. The counter-mass (17) should be dispersed as rapidly as possible on exit, in order not to endanger those in the vicinity of the gunner. According to the invention the arresting sleeve (12) has annular peripheral grooves (13,14) on its outer face and also on its inner face of equilateral triangular cross-section, and the piston (15) has a cartridge (16) holding the counter-mass (17), which at its forward end has a greater wall thickness than at its rearward end.

Abstract: A filament-reinforced plastic composite tube or tubular component is adapted to be load bearing and to more efficiently absorb energy by stable collapse in the event of axially compressive impact. The tubular component has at least one substantially planar wall comprising coplanar laminations of filament-reinforced plastic, wherein at least a portion of the filaments are non-oriented material such as graphite or glass and extend axially substantially parallel to the longitudinal axis of the tube. The tubular component is characterized in that the tube is provided at one end with a collapse trigger means adapted to promote stable, energy absorbing collapse of the tube. Specifically, the tube wall has a bevelled end surface forming at least one apex substantially normal to the plane of the aforesaid coplanar laminations. Each bevelled end surface is at an angle of about 5.degree.-40.degree. to a line coplanar with the laminations and perpendicular to the axially extending filaments thereof.

Abstract: A vehicle mounted crash attenuator includes an array of parallel diaphragms. A set of cell assemblies is interposed between adjacent diaphragms, and each cell assembly is formed of two L-shaped sheet metal components which are riveted together to form a rectangular column extending between the adjacent diaphragms. These columns are cross braced by ribbed braces which extend diagonally between adjacent columns. These cross braces stabilize the columns against long column buckling and promote short column buckling, thereby increasing the energy absorbing capability of the columns.

Abstract: A side member of a motor vehicle in which at least one of four side walls forming a closed tetragon has disposed thereon a plurality of beads extending transverse to the longitudinal direction of said at least one side wall. The beads are shorter than the width of said at least one side wall and are spaced at a pitch of P to (a+b).times.(1.+-.0.1)/2, where b is the transverse length said at least one side wall and a is the transverse length of a side wall adjacent said at least one side wall.

Abstract: A mounting system for a vehicle-mounted impact absorption box filled with a collapsible open cell network provides a lessened tendency for disintegration when subjected to the vibrations of the vehicle. The system contains a bolt surrounded by a region of transverse cells, with the bolt bonded to the cell walls and passing therethrough in a generally perpendicular direction. A further feature of the system is a pivot bracket constructed in two parts--a rigid portion and a pivot arm, the latter stabilized by springs which absorb torsional impulses on the arm arising from the vehicle vibrations. These two features work in conjunction with each other in reducing shock damage to the interior of the box, and thereby increase the life expectancy of the box as a whole.

Abstract: A stationary impact attenuation system (10) for reducing the severity of vehicular collisions occasioned by an errant vehicle striking an immovable object. The subject stationary impact attenuation system (10) includes support means (14), impact attenuating means (12) and protective means (16). The support means (14) is located in juxtaposed relation to an immovable object and so as to lie between the immovable object and an oncoming errant vehicle. The impact attenuating means (12) is positioned in supported relation on the support means (14) and is selectively operative to entrap an errant vehicle striking the stationary impact attenuation system (10) at a first location and to redirect an errant vehicle striking the stationary impact attenuation system (10) at a second location.

Abstract: An impact attenuating body is disclosed for use on trucks or the like, the impact attenuating body being arranged for engagement by vehicles or the like, the impact attenuating body being further adapted for gradually arresting motion of the vehicle and dissipating its impact energy. The impact attenuating body is formed with a collapsible form including laterally extending members with interconnecting brackets forming rows of compartments, the compartments being generally elongated along the direction of travel of the vehicle, selected compartments being void and different densities of shock absorbing material such as expanded plastic foam being arranged in the other compartments for arresting movement of the vehicle and dissipating its impact energy as the vehicle travels a selected distance after initial engagement with the body, the arrangement of shock absorbing material in the compartments being selected for causing the vehicle to continue generally along its initial travel direction.

Abstract: There is provided a shock absorber for containers for the transportation and/or storage of radioactive materials consisting of one or more radially or axially arranged chambers which are filled with shock absorbing material characterized by the shock absorber containing cup spring shaped sheets having a curvature directed away from the container.

Abstract: A displacement control device for damping relative movement between a structure and a support for the structure, and for absorbing energy when the relative movement exceeds a predetermined amount.

Abstract: A universal front anchoring system for reusable impact attenuation devices is provided. Buffer elements are positioned in an ordered array extending forwardly of a rigid backing member adjacent to a fixed structure. Diaphragm members are interposed in the array and extend laterally outward of the array at fixed intervals. Fender panels are pivotally coupled to laterally extending ends of the diaphragm members and extend rearwardly from their associated diaphragm members and partially overlap the fender panels coupled to the succeeding diaphragm members. Nonrigid means such as restraining cables and secondary cables interconnects the backing member and the diaphragm members. A pair of laterally spaced anchor assemblies is connected to the nonrigid means at the forward end of the impact attenuation device. The anchor assemblies are adapted for fixing to the ground and are symmetrical, identical and interchangeable with each other.

Abstract: A device for simulating railcar shock during coupling of freight cars comprising an inclined ramp, a backboard at the bottom of the ramp, a dolly to roll down the ramp into the backboard, a disposable hollow cylinder to be temporarily attached to the backboard or the dolly to be crushed therebetween when the dolly rolls into the backboard.

Abstract: A buffer device for an elevator employs, as a buffer member, a foamed plastic material such as polyurethane foam which undergoes very little permanent deformation upon receipt of an impact. The foamed plastic material is accommodated in a box made of a thin non-combustible material, and a heat-insulating material is disposed between the box and the buffer member in the box.

Abstract: The present invention relates to a device for damping impacts caused by the fall of heavy objects. This device comprises a group of deformable mechanical members arranged perpendicularly to a first plate and a second plate, a supplementary plate having substantially the same weight as each mechanical member being placed between the latter and the second plate. The supplementary plates are contiguous and each mechanical member has at least one predeformation at its end adjacent to the second plate. Application to the protection of discharge ponds against the fall of caskets.

Abstract: A vehicle comprises a main body including a firewall having a pair of side rails connected thereto and extending forwardly therefrom. A front bumper beam is secured to the side frames. The bumper beam comprises an elongated box structure having a pair of tubular elements therein in alignment with the pair of side rails. The tubular elements provide additional crush distance in the event of a frontal collision.

Abstract: An improved cushioning or shock absorbing device attachable to the ends of a generally cylindrical container for transporting or storing radioactive material, especially spent nuclear fuel elements, has a substantially uniform dampening or cushioning characteristic even for different impact directions. The device is cap-shaped, having an annular part with a plug part in the outer end thereof. The annular part includes a strong rigid inner sleeve extending from the open end of the device partly between the two parts. The inner end of the plug part has a sheet metal disc-like inner cover secured to the sleeve for detachment on impact. Both parts are divided into a plurality of interior chambers by sheet metal plates, the chambers being filled with cushioning material.

Abstract: An obstacle protection arrangement composed of a series of interconnected deformable segments, each comprising a U-shaped support member and a box structure containing crumpling tubes. Both sides of the arrangement are formed by overlapping flank members such that during a front collision there will be dissipation of energy by deformation of the segments, whereas during a side collision the arrangement behaves like a rigid girder.

Abstract: A protective strip or bumper for a road vehicle has an energy absorbing structure, partly formed of plastics material, mounted on a metal backing member. Within the plastics material body are a plurality of metal crushable elements which are plastically deformable in order to absorb energy when an impact occurs and which are also readily replaceable.

Abstract: A bidirectional mechanical load limiter for a push-pull control linkage includes a tubular crushable core that crushes in response to a predetermined tensile or compressive load to thereby limit the load in the linkage. The load limiter includes a tubular casing and a piston arranged in a telescoping configuration. The tubular crushable core, together with a pair of slide elements positioned adjacent the opposite ends of the core, is located within the casing by stop elements affixed to the inside of the casing. The piston passes through the bore of the tubular core and the slide elements and is retained in place by impeller elements affixed to the piston adjacent and abutting the slide elements. In normal operation, the load limiter operates as a rigid link in the linkage, with tensile and compressive loads being transmitted between the piston and casing through the crushable core. Under an excessive tensile load the piston and casing undergo relative extension as the core yields under the load.

Abstract: An energy absorbing apparatus is provided to dissipate the energy of the impact force of a vehicle. A plurality of energy absorbing sheets are arranged in a stacked relation to resist the impact force and to thereby dissipate the energy of the force. Each sheet has a honeycomb structure of hexagonal cells that are filled with a deformable material such as polyurethane foam and that are defined by walls of relatively rigid material. In operation, an impact force is applied to the stack of energy absorbing sheets and each sheet is thereby caused to cut or shear into its abutting sheet so that at least a portion of the energy of the impact force is dissipated. As the stacked sheets cut into one another, the energy of the force is further dissipated by the compression of the polyurethane foam of the sheets.

Abstract: An impact attenuator for installation along highways particularly at exit lanes from limited access roads is disclosed. The impact attenuator features the use of one or a plurality of novel crash cushions formed of polyurethane foam having a structure therein to help maintain the integrity of structure. The reinforcement may be a wire basket disposed therein. The attenuator is a device having a plurality of telescoping crash sections that nest upon impact.

Abstract: A shock absorber disposed between a steering wheel and a steering post, which comprises upper and lower holding rings to be coupled to hold the steering wheel and the steering post, respectively, and a plurality of supporting elements connected between the upper and lower holding rings. The upper and lower holding rings and the supporting elements form one substantially cylindrical unit, and the supporting elements are bent radially inwardly and outwardly to absorb an impact which may be caused during operating the vehicle.

Abstract: A contractible mine stopping adapted to be installed to extend as a vertical wall from the floor to the roof of a passageway in a mine, comprising a series of rows of substantially solid substantially non-compressible blocks of substantially fire-resistant material stacked one on top of another, and at least one row of contractible substantially fire-resistant block-like members adapted to contract without loss of structural integrity when the wall is subjected to a compressive load, as during a convergence of the floor and roof on the passageway. Each block-like member is preferably a hollow metal member which, when subjected to a compressive load, is adapted to contract heightwise of the member a distance corresponding to at least a major portion of the height of the member without loss of structural integrity of the member.