An array of inertial barriers

Abstract: An array of inertial barriers (10, 50, 30) resting freely on a support surface (55) alongside a vehicle roadway includes a number of separate frangible containers (12), each having a peripheral side wall and a bottom portion. A core or insert (20) is positioned within each container to define an annular space between the core and the respective peripheral wall. This annular space has an average inner diameter which is at least about 25% of its average outer diameter. A dispersible material such as sand (5) is disposed in the annular spaces such that no more than 10% of the mass of sand in any container (12) of the array is disposed in an uninterrupted disc extending across the respective container (12).

Description: This invention relates to an improved array of inertial barriers of the type used alongside a roadway to decelerate a vehicle that has left the roadway. Inertial highway barriers have been used for some time to prevent vehicles from striking an obstacle such as a bridge pier or the like at full velocity. An inertial barrier relies on the mass of the barrier to decelerate the vehicle. Typically, a dispersible material such as sand is enclosed in a frangible container. When the vehicle strikes the container, the momentum of the impacting vehicle is dissipated in accelerating the sand. Early uses of inertial barriers are disclosed in US-RE-29544 and US-A-4183504. In these barriers the mass of sand is elevated above the roadway on a platform in an attempt to match the heights of the centers of gravity of the barrier and the impacting vehicle. In this way, the tendency of the impacting vehicle to be accelerated vertically (either up or down) by the barrier is minimized. Later approaches have used other structures to elevate the center of gravity of the dispersible mass. For example, US-A-4073482 discloses barriers having sand in a wine glass shape. U.S. Patent 4,289,419 discloses an inertial barrier system wherein a central void is provided in the lower part of the barriers. U.S. Patents 4,688,766 and 4,557,466 (see preamble of claim 1) disclose inertial barriers wherein an insert is used to elevate the center of gravity of the lighter weight barriers. In all of the inertial barriers discussed above, the more massive barriers include a substantially monolithic block of dispersible material. This configuration causes the mass per unit of height of the barrier to be relatively large. For this reason, a mismatch of only a few inches between the elevations of the centers of gravity of the barrier and the impacting vehicle can result in undesirably large vertical accelerations being imparted to the vehicle. Note for example the substantially solid masses of sand shown in the barriers of Figures 3a and 3b of US 4688766 and 4557466, in the 635 Kg (1400 pound) barriers of US 4289419 and in all of the barriers of US 4073483, US RE 29544 and US 4183504. This configuration can represent an unnecessary hazard to an impacting vehicle if the sand is wet and frozen. In this case, the monolithic block of sand is no longer easily dispersible, and it can cause unacceptably large decelerations to the vehicle. Additionally, unacceptably large blocks of frozen sand may be accelerated by the vehicle, and these accelerated blocks may present hazards to bystanders. Of course, it should be recognized that not all highway barriers are inertial barriers. Another class of barriers relies on a fixed support for the barrier, and this support may be either horizontally or vertically oriented. Such barriers are secured to the support such that it is not the inertia of the barrier itself that provides the principal decelerating force. Note for example the energy absorbing devices shown in US-A-3666055, US-A-4101115 and US-A-3141655. In the latter specification Figure 6 shows an energy absorbing device that includes an annulus of sand 28. The entire device is secured to a concrete base 14 by a tension rod 30. Because the energy absorbing devices of the above patents are not inertial barriers, they are of limited application to the present invention. This invention provides an array of free standing inertial barriers positioned on a support surface alongside a vehicle roadway, said array comprising: a plurality of frangible containers arranged along an axis, each of said containers comprising an outer wall and a lower portion; certain of the containers having inner cores positioned to define upwardly open annular spaces between the cores and the respective outer walls, said annular spaces having an average inner diameter and an average outer diameter, the average inner diameter being at least about 20% of the average outer diameter; and a plurality of masses of dispersible material, disposed in the respective annular spaces such that each of the masses is substantially annular in shape; wherein at least some of the containers in the array have cores supported on said lower portions of the containers to define annular spaces which extend from the lower ends of the containers upwardly between the cores and container walls in which annular masses of dispersible material are disposed; and in that no more than about 10% of any of the masses of dispersible material in any of the containers of the entire array extends in an uninterruped disc across the respective containers. In one example according to the invention certain containers of the array may have the inner cores mounted on the container walls above the lower portions thereof. More specifically certain containers may have one form of core which is supported on the side wall of the container above said lower portion to hold the mass of dispersible material therein spaced above the lower portion of the container and other containers may have a second form of core which is supported at the lower portion of the container to hold a larger mass of dispersible material but with its centre of gravity at generally the same level. In one specific arrangement the cores may have encircling bases at the lower ends thereof and said one form of core may be supported by the base at the outer wall spaced above said lower portion and the other form of core may be supported by its base on the lower portion of the container. In either of the latter arrangements the dispersible masses in the containers having said first forms of the inner cores may be more massive than the dispersible masses in the containers having said second forms of the inner cores. In any of the above arrangements the masses of dispersible material may be non-uniform in mass, with less massive ones of the masses situated at one end of said axis and progressively more massive ones of the masses situated progressively farther away from said one end of the axis. By way of example the most massive one of the masses may have a weight greater than about 907.18 kilograms (2000 pounds). Also in any of the above arrangements each of the dispersible masses may comprise sand. In accordance with a further feature of the invention each of the frangible containers may rest on the support surface freely without tension members secured between the support surface and the container. The average inner diameter is at least 40% of the average outer diameter for each of the annular spaces. In addition drainage holes may be provided in the frangible containers to drain water from the dispersible masses. According to a still further feature of the invention the array of containers may comprise a plurality of shorter containers at a front end of said axis and at least one taller container at a rear end of the axis; at least certain of the shorter containers having a short form of core which is supported on the side wall of the container above said lower portion to hold the mass of dispersible material therein spaced above the lower portion of the container and at least one taller container having a second taller core which is supported at the lower portion of the container to hold a larger mass of dispersible material but with its centre of gravity at generally the same level. There now follows a description of two specific embodiments of the invention, by way of example, with reference being made to the accompanying drawings, in which: Figure 1 is an exploded perspective view of a first highway inertial barrier included in the presently preferred embodiment of this invention. Figure 2 is an exploded perspective view of a second highway inertial barrier included in this embodiment. Figures 3a-3e are five sectional views of inertial barriers included in the array of Figures 4 and 5. Figure 4 is a plan view of a first preferred embodiment of the inertial barrier array of this invention. Figure 5 is an elevational view in partial cutaway of the array of Figure 4. Figure 6 is a plan view of a second preferred embodiment of the inertial barrier array of this invention. Figure 7 is an elevational view in partial cutaway of the array of Figure 6. Figures 4-7 show two separate arrays of inertial highway barriers that embody the present invention. Before turning to these figures, details of construction of the individual barriers will be described in conjunction with Figures 1-3e. Figure 1 shows an exploded perspective view of a first inertial barrier 10. This barrier 10 includes a container 12 which includes a peripheral sidewall 13 which terminates at its upper end in an annular lip 14 and at its lower end in a bottom panel 15. The bottom panel 15 is provided with an array of drain holes 16, and the sidewall 13 defines a shoulder 18 at an intermediate position. The barrier 10 also includes an inner core or insert 20 that includes an annular flange 22 and a cylindrical or frusto-conical upper section 24. The flange 22 is positioned to rest on the shoulder 18 to support the insert 20 in place, and the flange 22 has sufficient structural rigidity to support a mass of dispersible material such as sand in the annular space between the upper section 24 and the sidewall 13. Finally, the barrier 10 includes a lid 26 which is designed to engage the lip 14 to securely hold the lid 26 in place. Figure 2 shows an exploded perspective view of a second barrier 30 which is generally similar to the barrier 10 described above. The barrier 30 includes a container 32 having a sidewall 34, a bottom surface 36, and drain holes 38. The container 32 is similar to the container 12, but is somewhat higher in overall height. The barrier 30 includes an insert 40 having an annular flange 42 and a frusto-conical upper section 44. The insert 40 is designed to rest on the bottom surface 36 and to create an annular space between the upper section 44 and the sidewall 34. This annular space is intended to receive a dispersible material such as sand when the barrier is fully assembled. Finally, the barrier 30 includes a lid 46 which is similar to the lid 26 described above, but may be more steeply angled as shown in Figure 2. The container 32 is shown as defining a flange in the side wall, but this feature may readily be detected if desired. The arrays of barriers shown in Figures 4-7 include a number of separate barriers. In particular, the array of Figures 4 and 5 includes barriers of five different masses; Figures 3a-3e provide cross-sectional views of these five different barriers. The barriers of Figures 3a, 3b and 3c are identical in structure with the barrier 10 shown in Figure 1, but each contains a different quantity of sand S. The barriers of Figures 3a, 3b and 3c have a sand mass of (90.8, 181.6 and 317.8 Kg) 200, 400 and 700 pounds, respectively. As shown in Figure 3a, the annular space occupied by the sand defines an average inner diameter D I and an average outer diameter D O . Preferably, the average inner diameter D I is at least about 20% of the average outer diameter D O , and most preferably the average inner diameter D I is at least 40% of the average outer diameter D O . Figure 3d shows a more massive barrier 50 having a weight of 1400 pounds (635.6Kg). The barrier 50 is made up of a mix of the parts described above. In particular, the container is the shorter container 12 of Figure 1 while the insert 40 and the lid 46 are as shown in Figure 2. Because the lid 46 is more steeply angled, the container 12 can be used with the insert 40. Finally, Figure 3e shows the distribution of sand in the barrier 30 of Figure 2. Preferably, the centers of gravity of all five of the barriers are at approximately the same height (within a range of about (0.127 m) five inches), and this height matches that of the canter of gravity of the average impacting vehicle for which the barriers are designed. Figures 3a-3e illustrate a number of important features of the inertial barriers 10, 30, 50. First, in all cases the insert 20, 40 extends completely through the mass of sand S such that the mass of sand S has an annular configuration at any cross-section. It is not essential in all embodiments of this invention that the insert 20, 40 pass completely through the mass of sand S, but in general less than 10% of the mass of sand S be disposed in an uninterrupted disc passing completely across the container 12, 32. This configuration for the sand provides several important advantages. First, because the insert 20, 40 occupies a considerable volume, the sand S for a given weight is distributed over a larger vertical distance H (Figure 3a). For this reason, the mass per unit height (M/H), is reduced with the inertial barriers of Figures 3a-3e as compared to an inertial barrier in which the sand is compacted into a monolithic volume as in US Re 29544 patent described above. By reducing M/H, the barriers of Figures 3a-3e operate more reliably when there is a mismatch between the height of the centers of gravity of the barrier and the impacting vehicle. In general, impacting vehicles will have centers of gravity at a range of heights, and it is therefore not possible for any one barrier to have a center of gravity at the correct height for every vehicle. However, by minimizing M/H, the barriers of Figures 3a-3e minimize the vertical forces applied to the impacting vehicle for any given disparity in the heights of the centers of gravity. A second important advantage is that because the sand is disposed completely in an annular space, there is more of a tendency for the sand to be broken into small pieces during an impact. The containers 12, 32 are frangible and are designed to break apart during an impact. In the event the sand is wet and frozen, a monolithic block of sand can result in undesirably large blocks of frozen sand being accelerated away from the impact. The configurations of Figures 3a-3e provide a central void in the mass of sand in each case. This promotes break-up of any frozen sand into manageable sizes during an impact. Yet a third advantage is improved drainage provided by the configurations of Figures 3a-3e. These configurations result in increased vertical height of sand for given mass as compared to a monolithic body of sand. This increased vertical height increases the pressure of water at the bottom of the column of sand, and thereby increases the efficiency with which water is drained via the drainage holes 16, 38. In this regard, it is important that the fit between the insert 20 and the shoulder 18 and the fit between the insert 40 and the bottom surface 36 be sufficiently loose as to allow adequate drainage. Turning now to Figures 4 and 5, these figures show one preferred embodiment of an array of the inertial barriers described above. As shown in Figures 4 and 5, the barriers 10, 30, 50 are freely supported on a support surface SS without tension members or other means for tying the barriers in place on the support surface SS. The barriers 10, 30, 50 are arranged in an array alongside a roadway in front of an obstacle O. The barriers 10, 30, 50 are arranged along an axis extending away from the obstacle O with the lighter weight barriers at one end and the heavier weight barriers at the other, near the obstacle O. In this case, the most massive barrier 50 has a weight in excess of (908 Kg) 2,000 pounds. As shown in Figure 5, each of the barriers in the array includes a respective mass of sand S that is annular in shape, with the respective insert 20, 40 extending completely from the top to the bottom through the mass of sand. Of course, this invention is not limited to arrays of the precise configuration shown in Figures 4 and 5, and it can easily be adapted to either larger or smaller arrays. Figures 6 and 7 show one smaller array made up of four inertial barriers 30, 50. Once again, the barriers are progressively heavier in weight near the obstacle O, and are freely supported on a support surface SS. The preferred embodiments described above provide the advantage of minimizing the total number of component parts required to make up the separate barriers. However, this is not required in all applications, and each barrier may have a distinctive container, insert and lid if desired. The following details of construction are provided in order better to define the presently preferred embodiments of this invention. It should be clearly understood that these details are not intended to be limiting in any way, and that other materials, dimensions, specifications and fabrication techniques can be used if desired. The lids 26, 46 can be rotationally molded of a high, low, or medium density polyethylene resin. The lid should preferably have the properties set out in Table I. The container 12, 32 can also be rotationally molded of a high density polyethylene (H.D.P.E.) using a resin such as that available under the tradename Chemplex 5305 or Allied 7002. The materials listed in Table II can be used in a three-layer system having a center layer of foamed H.D.P.E. and inner and outer layers of nonformed H.D.P.E.. In each case, the various quantities of H.D.P.E., UV Stabilizers and foaming agent are dry blended for a minimum of 20 minutes using a sigma blade mixer. The resulting three layer container should preferably have the physical characteristics set out in Table III. Of course, a three-layer wall is not required for the container 12, 32, and it may be preferable in some applications to use two layers: a foamed inner layer approximately (.476 cm) 3/16" in thickness and an unfoamed outer layer approximately (.159 cm) 1/16" in thickness. The insert 20, 40 can also be rotationally molded of H.D.P.E. such as that described above. The H.D.P.E. is preferably combined with an ultraviolet stabilizer such as (0.99 g per Kg) .45 grams per pound TINUVIN 770 and TINUVIN 327. The resulting insert preferably has the physical properties set out in Table IV. Of course, it should be understood that a wide range of changes and modifications can be made to the preferred embodiments described above. It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, which are intended to define the scope of this invention. Property (Units) Test Method Value Tensile strength (PSI) [KPa] ASTM-D-638 2400 Min [16547 KPa] Elongation (%) ASTM-D-638 200 Min Brittleness Temp (°F) [°C] ASTM-D-746 -40 Lower Limit [-40] Density (gm/cc) [Kg/m³] ASTM-D-1505 .930 - .950 [930 - 950] Low Temperature Impact Resistance ARM Falling Dart Severity Test (5 lb dart with 1/2" radius nose, 3 ft drop, 72°F) [2.27 Kg dart with 0.0127m radius nose, 0.914 m drop, 22°C] No fracture Property (Units) Test Method Value Tensile Strength (PSI) [KPa] ASTM D-638 1400 +/- 200 [9653 +/- 1379] Elongation (%) ASTM D-638 200 min. Low Temperature Impact Resistance ARM Falling Dart Test (5 lb dart with 1/2" radius nose, 2 ft. drop, 72°F.) [2.27 dart with 0.127 m radius nose, 0.61 m drop 22°C] Fracture Property (Units) Test Method Value Tensile Strength (PSI) [KPa] ASTM-D-638 3300 +/- 350 [22753 +/- 2413] Elongation (%) ASTM-D-638 200 Min Density (gm/cc) [Kg/m³] ASTM-D-1505 .950 - .960 [950 - 960] Brittleness Temp. (°F) , [°C] ASTM-D-746 -100 Lower Limit [-73] Low Temperature Impact Resistance ARM Falling Dart Severity Test (5 lb dart with 1/2" radius nose, 3 ft drop, 72 deg) [2.27 Kg dart with 0.127 m radius nose, 0.914 m drop 22°C] No fracture

Claims: An array of free standing inertial barriers positioned on a support surface alongside a vehicle roadway, said array (10, 30, 50) comprising: a plurality of frangible containers (12) arranged along an axis, each of said containers comprising an outer wall (13) and a lower portion (15); certain of the containers having inner cores (20) positioned to define upwardly open annular spaces between the cores and the respective outer walls, said annular spaces having an average inner diameter and an average outer diameter, the average inner diameter being at least about 20% of the average outer diameter; and a plurality of masses (S) of dispersible material, disposed in the respective annular spaces such that each of the masses is substantially annular in shape; characterised in that at least some of the containers in the array have cores supported on said lower portions of the containers to define annular spaces which extend from the lower ends of the containers upwardly between the cores and container walls in which annular masses of dispersible material are disposed; and in that no more than about 10% of any of the masses of dispersible material in any of the containers of the entire array extends in an uninterruped disc across the respective containers. An array of barriers as claimed in Claim 1, characterised in that certain containers (12) of the array have the inner cores (20) mounted on the container walls (13) above the lower portions (15) thereof. An array as claimed in Claim 2, characterised in that certain containers (12) have one form of core (20) which is supported on the side wall (13) of the container above said lower portion (15) to hold the mass (S) of dispersible material therein spaced above the lower portion of the container and other containers (12) have a second form of core (40) which is supported at the lower portion (15) of the container to hold a larger mass (S) of dispersible material but with its centre of gravity at generally the same level. An array according to Claim 3, characterised in that the cores (20, 40) have encircling bases (22, 42) at the lower ends thereof and said one form (20) of core is supported by the base (22) at the outer wall (13) spaced above said lower portion (15) and the other form of core (40) is supported by its base on the lower portion (36) of the container. An array as claimed in Claim 3 or Claim 4, characterised in that the dispersible masses (S) in the containers (12) having said first forms (20) of the inner cores are more massive than the dispersible masses (5) in the containers (12) having said second forms (40) of the inner cores. An array as claimed in any of Claims 1 to 5, characterised in that the masses of dispersible material (S) are non-uniform in mass, with less massive ones of the masses situated at one end of said axis and progressively more massive ones of the masses situated progressively farther away from said one end of the axis. An array as claimed in Claim 6, characterised in that the most massive one of the masses has a weight greater than about 907.18 kilograms (2000 pounds). An array as claimed in any of Claims 1 to 7, characterised in that each of the dispersible masses comprises sand (S). An array as claimed in any of the preceding claims, characterised in that each of the frangible containers (12) rests on the support surface (55) freely without tension members secured between the support surface and the container. An array as claimed in any of the preceding claims, characterised in that for each annular space between a core and container wall, said average inner diameter (D I ) of the annular space is at least 40% of the average outer diameter (D O ) of the space. An array as claimed in any of the preceding claims further comprising drainage holes (16, 38) in the frangible containers to drain water from the dispersible masses (S). An array as claimed in any of the preceding claims, characterised in that the array of containers comprises a plurality of shorter containers (10) at a front end of said axis and at least one taller container (30) at a rear end of the axis; at least certain of the shorter containers (10) having a short form of core (20) which is supported on the side wall (13) of the container above said lower portion (15) to hold the mass of dispersible material therein spaced above the lower portion of the container and at least one taller container (30, 50) having a second taller core (40) which is supported at the lower portion of the container to hold a larger mass (5) of dispersible material but with its centre of gravity at generally the same level.

Inventors: DENMAN OWEN S, KRAGE WILLIAM G, DENMAN, OWEN S, KRAGE, WILLIAM G
Applicants: ENERGY ABSORPTION SYSTEM, ENERGY ABSORPTION SYSTEMS, INC.
Application year: 1990
Main classification: E01F15
IPC codes: E01F15, E01F13