4 Barrier Design 2008

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  • Barriers are certified for a velocity of up to 30 m/s. Usually the range of velocity for the crash test is between 25 and 30 m/s. This means that the highest free fall is nearly 50 m. In case of higher speed ( i.e. 35 m/s for a free fall of 60 m/s) the impact doesn’t deform, but pierces the barrier. Then multiple lines of barriers could be used: the first line so called “sacrificial” can be broken slowing down the block, the second barrier can stop it. Depending on the morphology of the slope, an embankment could be the best solution. Roughly speaking, we can say that the deepest penetration into the embankment is twice the diameter of the boulder.
  • Falling energy is the sum of the rotational energy and the translational energy. The most important energy is the translational one that is normally at least 80% of the total kinetic energy. The rotational energy is around 10-20% of the total and is related to the shape of the block. Normally square blocks have a low rotational energy. The diagram shows the energy level in the Y axis versus the height of free fall for boulders with different volumes (with unit weight 26.5 kN/m3). The red arrows show the energy range for commonly used rockfall barriers. Note that a barrier with 2000 kJ stops only one boulder with that energy level, because after the impact it is destroyed. The highest energy level is guaranteed by embankments which can resist several impacts with energy of 5000 kJ.
  • The energy of a boulder is proportional to the square of its velocity, and is directly proportional to its mass. A doubling of the mass gives a doubling of the energy. But a little change in the velocity produces a big change in the energy level. The falling velocity is reduced by impacts of the boulder during its path. For this reason in the case of a short slope as in the picture, we can roughly estimate the energy level to be equal to one third of the potential energy.
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  • Based on the most frequent questions by designers and contractors
  • Based on the most frequent questions by designers and contractors
  • El panel se deforma pero no cede de forma brusca ni presenta roturas. Velocidad de video acelerada. Toma lateral. The panel is deformed but is not deformed sharply, does not even present breaks. Speed of video accelerated. Lateral capture. el pannello si deforma, ma non dà cedimenti improvvisi o rotture. Filmato accelerato
  • Based on the most frequent questions by designers and contractors
  • Based on the most frequent questions by designers and contractors
  • Based on the most frequent questions by designers and contractors
  • Based on the most frequent questions by designers and contractors
  • Based on the most frequent questions by designers and contractors
  • Based on the most frequent questions by designers and contractors
  • Based on the most frequent questions by designers and contractors
  • 4 Barrier Design 2008

    1. 1. ROCKFALL BARRIER
    2. 2. FALLING VELOCITY A=Broken barrier A = Sacrificial Barrier B = Effective barrier Higher velocities (i.e. 35-40 m/s) are assumed to make one barrier collapse under the impact . In such case multiple barrier lines shall be used: the first sacrificial line will break dissipating the block, the second barrier will stop it. Barriers are certified for velocities up to 30 m/s.
    3. 3. FALLING ENERGY E nergy of a falling rock: E = E  + E k E k = translational energy = ½ M v 2 M = block mass v = translational velocity E  = rotational energy = ½ I  2 I = inertia moment  = angular rotational velocity The most effective energy is the translational one which is normally 80% (or higher) than the total kinetic energy. The rotational energy is around 10-20% of the total energy and is related to the shape of the block.
    4. 4. FALLING ENERGY E = potential energy m = mass g = gravity 9.81 m/s 2 h = falling height h E  1/ 3 m g h
    5. 5. WHERE TO PLACE THE BARRIER What to consider: <ul><li>the slope morphology </li></ul><ul><li>the deformation of the barrier </li></ul><ul><li>the accessibility of the site both for installation and maintenance requirements </li></ul>- The most favorable morphology should be chosen: Normally barriers are less efficient if they are built in ditches or at the slope bottom; - The deformation of flexible barriers can be several meters, sometimes also bigger than 10 m: the structure cannot be placed close to the road or the infrastructure to protect; - The maintenance procedure should be also considered: it is also important to consider the site accessibility. A B C D
    6. 6. THE “VERTICAL” MORPHOLOGY OF THE POSITION WHERE TO INSTALL THE BARRIER: WHAT IS TO BE CONSIDERED ? <ul><li>The minimum distance between the barrier and the raod/building to be protected… </li></ul><ul><li>Presence of retaining walls, slopes … </li></ul><ul><li>Other… </li></ul>Normally the barrier should be further than 6 m (20 ft) from the road or infrastructures. The barrier doesn’t have to be placed at the bottom of the slope, it can be placed higher in order to catch the rocks. SOIL WALL WALL BOULDER SOIL ROAD D C B A
    7. 7. HOW TO ANALYSE THE FALLING OF THE ROCKS - Site observations; - Numerical modeling ; THE SITE OBSERVATIONS NORMALLY GIVE THE POSSIBILITY TO APPRECCIATE THE EFFECTS OF THE FALLING OF THE ROCKS. NUMERICAL MODELLING CAN DESCRIBE THE FALLING TRACKS, SUGGESTING THE KNOWLEDGE OF THE PARAMETERS TO BE USED DURING THE FINAL DESIGN OF THE PROTECTION.
    8. 8. THE PARAMETERS USED FROM THE AVAILABLE DESIGN PARAMETERS <ul><li>Topographic slope section; </li></ul><ul><li>Coefficients describing the energy dissipation after any block impact; </li></ul><ul><li>Coefficients describing the rolling of the block along the slope; </li></ul><ul><li>Coefficients describing the slope roughness; </li></ul><ul><li>Block size; </li></ul><ul><li>Portion of block detachment; </li></ul><ul><li>Change of the above mentioned parameters along the slope; </li></ul><ul><li>Other parameters used as data control. </li></ul>Good input data can approximate the falling rocks tracks, speed, energy and heights of impact with a realistic approximation. N = axis perpendicular to the slope T =axis tangent to the slope
    9. 9. NUMERICAL MODELLING RESULTS ( IN 2 DIMENSIONS ) The most relevant results obtained from the numerical model are: Topographic section with the rock trajectory
    10. 10. Topographic section with the end point of the trajectory
    11. 11. Topographic section with the trajectory related to the maximum falling heights
    12. 12. Topographic section showing the maximum falling energies
    13. 13. WHAT MUST BE INCLUDED IN A PROJECT <ul><li>Making numerical simulations along different cross sections, the following tables can be produced: </li></ul><ul><li>Information at the end point of the trajectory </li></ul><ul><li>Information on of the blocks falling heights </li></ul><ul><li>Information on the falling energies </li></ul><ul><li>Information on the interventions </li></ul>TOGETHER WITH THE OTHER FACTORS ( FREQUENCY OF THE FAILURES, RISK FOR SURROUNDING ROADS AND INFRASTRUCTURES ) ALLOW TO PREPARE THE FINAL PROJECT AND THE PRIORITIES FOR THE DIFFERENT PHASES OF THE INTERVENTION.
    14. 14. <ul><li>Barrier destroyed by 1.5 m3 (estimated velocity 3 - 5 m/s – 55 kJ energy) </li></ul><ul><li>Barrier pierced by a boulder 0.04 m3 (estimated velocity 12-14 m/s, 18 kJ energy) </li></ul>The limits of non deformable barriers
    15. 15. F  t = M  v The capacity of a “non deformable” barrier is related to the elastic deformability of its components. Because its components are stiff (cable, post), the “non deformable” barriers must slow down the velocity (  v) in a very short time (  t). The force F of impact F = M  v /  t is very high. Then the non deformable barrier break at very low energy level. The limits of non deformable barriers
    16. 16. Rockfall barriers New barrier series according to ETAG 27 GUIDELINE FOR EUROPEAN TECHNICAL APPROVAL of FALLING ROCK PROTECTION KITS - Draft - Edition November 2006 OM CTR barriers satisfy a wide range of energy levels ETAG 27 and performances Energy level Velocity Boulder Volume Name of Barrier 500 kJ 25 m/s 0.6 m 3 CTR 05/07/B 1 000 kJ 25 m/s 1.2 m 3 CTR 10/04/B 2 000 kJ 25 m/s 2.4 m 3 CTR 20/04/A (ring panel) 2 000 kJ 25 m/s 2.4 m 3 CTR 20/04/B (cable panel) 3 000 kJ 25 m/s 3.5 m 3 CTR 30/04/B 5 000 kJ 25 m/s 5.8 m 3 OM CTR 50/07/A
    17. 17. ETAG 27 require 2 test: OM CTR barriers are certified both for MEL and SEL tests ETAG 27 and performances MEL = Maximum Energy Level The barrier has to catch a boulder with the maximum energy level. The residual height of the panel after the impact indicates the quality level of the barrier. SEL = Service Energy Level The barrier has to catch two impacts of a boulder with 1/3 of the MEL energy without damage. The residual height after the first impact must be greater than 70%. The second impact needs only to catch the boulder.
    18. 18. ETAG 27 and performances Lateral view of a falling rock protection kit OM CTR barriers do not need down slope cable
    19. 19. 0°    90°  -20°     +20° Nominal height of the barrier Residual height (after impact) OM CTR barriers give the best residual height ETAG 27 and performances  
    20. 20. OM CTR barriers give the best residual height ETAG 27 and performances Producer of 3000 kJ ISOFER AG GEBRUGG AG CTR Name of the barrier ISOSTOP 3000 kJ RXI 300 CTR 30/04/A Nominal Height 5.23 m 4.79 m 5.00 m Residual height after 100% Energy 49.14 % (5.23 m) 62.23 % (3.18 m) 66.00 % (3.30 m) Producer of 2000 kJ ISOFER AG GEBRUGG AG CTR CTR Name of the barrier ISOSTOP 2000 kJ RXI 2000 CTR 20/04/A CTR 20/04/B Nominal Height 4.80 m 5.11 m 4.00 m 5.00 m Residual height after 100% Energy 54.79 % (2.63 m) 62.23 % (3.18 m) 71.25 % (2.85 m) 73.00 % (3.65 m)
    21. 21. Falling rock protection kit classes A classification for residual height for MEL is also foreseen as follows: Category A : Residual Height ≥ 50 % nominal height Category B : 30% nominal height < Residual Height < 50 % nominal height Category C : Residual Height ≤ 30 % nominal height OM CTR barriers are classified in “A” category They are safer with respect to the height of impact. ETAG 27 and performances
    22. 22. ETAG 27 and performances OM CTR barriers gives the lowest elongation unload position Maximum elongation during the impact More flexibility when installing close to infrastructure   Net before impact
    23. 23. ETAG 27 and performances OM CTR barriers give the lowest elongation More flexibility when installing close to infrastructure PRODUCER OF 2000 kJ ISOFER AG GEBRUGG AG CTR CTR Name of the barrier ISOSTOP 2000 kJ RXI 2000 CTR 20/04/A CTR 20/04/B Max deformation with Max Energy Level (dynamic condition) no one indication no one indication 4.65 m 4.30 m Residual deformation after Max Energy Level (static condition) 6.80 m 6.70 m 4.20 m 4.05 m PRODUCER OF 3000 kJ ISOFER AG GEBRUGG AG CTR Name of the barrier ISOSTOP 3000 kJ RXI 300 CTR 30/04/A Max deformation with Max Energy Level (dynamic condition) no one indication no one indication 5.20 m Residual deformation after Max Energy Level (static condition) 7.40 m 6.60 m 4.60 m
    24. 24. Block size Energy FIELD TEST Vertical field test Inclined field test Falling velocity >= 25 m/s OM CTR barriers are tested on vertical field ETAG 27 and performances
    25. 25. ETAG 27 and performances The force shall be measured during the entire time of impact The field tests done by OM CTR measure the force acting on the stream cable and on the base plate. No other manufacturer measures shear and pressure forces acting on the base plate
    26. 26. The field test is conducted on a barrier with 3 modules in a straight line, that is why 3 modulus is the suggested minimum length of a barrier Configuration of the Crash test barrier ETAG 27 and performances Plan view Front view Lateral post Intermediate post Lateral post Intermediate post
    27. 27. 1000 KJ Barrier Test
    28. 28. ETAG 27 and performances
    29. 29. OM CTR barriers allow some tolerance when positioning the post: more flexibility when installing on rough slope. Easy to install R 15° (*) Plan view Front view (*) the value can be increased using lateral anchors or downslope anchor. 10.0 m 0.50 m
    30. 30. Length Easy to install <ul><li>OM CTR barriers allows the sharing of the lateral post between two section. </li></ul><ul><li>This allows: </li></ul><ul><li>Installation along curves </li></ul><ul><li>The assembly of long barriers </li></ul>The best performances are developed by barriers 50 – 70 m long Yes Proposal L = 60 m + 50 m Yes Proposal L = 110 m Exception Proposal L < 30 m
    31. 31. Easy to install Note: The correct design and on site positioning of barriers is typically site specific. Up slope down slope Up slope down slope Plan view The barrier works in a good way but could require some down slope anchors to stabilize the structure The barrier could work in a bad way but doesn’t require any devices to stabilize the structure
    32. 32. OM CTR barriers can be installed both on vertical and inclined slopes. Easy to install
    33. 33. Easy to install OM CTR barriers do not require downstream cables This allows faster and cheaper installation. Down slope Up slope
    34. 34. Easy to install OM CTR barriers are simple to install Taking into account the experiences on job sites, the assembling of the OM CTR barriers has been simplified by technical solutions. E.g. many connections are directly arranged in the factory.
    35. 35. OM CTR barriers are simple to install A number of field crash tests were performed which indicates the barrier has been designed and manufactured in the most economical and effective way (e.g. 15 for 500 kJ). No one component of the barrier is oversized (e.g. diameter of the cables). Many demanding jobs have been reduced (e.g. number of clamps) . Useless components have been removed (e.g. thimbles). Easy to install
    36. 36. Easy to install OM CTR barriers are fast and economical to install The standing up of the post is helped with a steel arm. The assembling of the posts by helicopter is faster. It requires one fifth of the time usually employed for other barriers.
    37. 37. Easy to install OM CTR barriers are more economical to install The forces measured on the base post are low. OM CTR barriers don’t require big plinths. The plinths are aimed to level and smooth the ground only.
    38. 38. Easy to install OM CTR barriers are easy to install Basically it is enough to use steel bars or miropiles for the foundations. Different base plates will be adopted. The plinth levels the ground. When ordering the barrier don’t forget to specify the kind of soils
    39. 39. Easy to install OM CTR barriers are fast to install OM CTR barriers has been created by people that assemble barriers in the field. The post can double up as ladder (*) (*) not for CTR 500 kJ where the posts are done by tubular elements
    40. 40. OM CTR barriers ensure high performances The friction brake is rasped by the rope running inside two steel plates. So the brake changes its behavior during the impact. In OM CTR barriers the brake system works by deformation and not by friction. This ensures the effectiveness of the system during the impact and in the most varying environmental situations (rust on cables, temperature, changes in the galvanization, etc.) Technology
    41. 41. Technology OM CTR barriers are easy to maintain The pin at the base of the post is designed as a fuse. It releases the post before the foundation can be destroyed. In this way the foundation is saved even if the boulder hardly hits the base of the post.
    42. 42. OM CTR barriers give high performances Technology Barrier CTR 20/04/A - 2006 June – Amelia - Italy Height of fall 70 m - Volume 4 m 3
    43. 43. OM CTR 2000 kJ, the best performances Technical comparison Producer ISOFER AG GEBRUGG AG CTR CTR OM Name of the barrier ISOSTOP 2000 kJ RXI 200 CTR 20/04/A CTR 20/04/B Certificated by UFAM/BAFU date 05/19/06 No. S 05 10 UFAM/BAFU date 05/19/06 No. S 04 7 DISTR University of Bologna DISTR University of Bologna Code for the test Swiss code Swiss code ETAG /Swiss ETAG / Swiss Kind of test Vertical field test Vertical field test Vertical field test Vertical field test Test velocity 25.00 m/s 25.00 m/s 25.78 m/s 25.35 m/s Number of test 1 - Small energy for piercing 1 - Small energy for piercing 1 - Small energy for piercing 1 - Small energy for piercing 2 - 50% energy (1000 kJ) 2 - 50% energy (1000 kJ) 2 - 100% energy (2250 kJ) 2 - 100% energy (2250 kJ) 3 - 100% energy (2000 kJ) 3 - 100% energy (2000kJ) 3 - 50% energy (1134 kJ) 3 - 100% energy (2250 kJ)     4 -1/3 energy (742 kJ)       5 -1/3 energy (742 kJ)  
    44. 44. OM CTR 2000 kJ, the best performances Technical comparison Producer ISOFER AG GEBRUGG AG CTR CTR OM Name of the barrier ISOSTOP 2000 kJ RXI 2000 CTR 20/04/A CTR 20/04/B State of the structure after 100% energy   Bending of a post, rupture of a base of a post, folding of a base plate     Notes concerning the test Repairing works between 2nd and 3rd test Repairing works between 2nd and 3rd test No one repairing works No one repairing works Substitution of No. 14 brake systems Substitution of No. 13 brake systems   no one   no one Nominal Height 4.80 m 5.11 m 4.00 m 5.00 m Residual height after 100% Energy 54.79 % (2.63 m) 62.23 % (3.18 m) 71.25 % (2.85 m) 73.00 % (3.65 m) Maximum deformation with 100% energy no one indication no one indication 4.65 m 4.30 m Residual deformation after 100% energy 6.80 m 6.70 m 4.20 m 4.05 m Forces on foundation 117 kN max 235 kN max 260 kN lateral; 185 kN up slope 270 kN lateral; 220 kN up slope Notes on certificate RESERVATION: Should deficiencies arise following certification of the safety net, FOEN may revoke product release and delete it from the type approval list. RESERVATION: Should deficiencies arise following certification of the safety net, FOEN may revoke product release and delete it from the type approval list. No one reservation No one reservation

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