1 00:00:36.000 --> 00:00:40.000 When it comes to building skyscrapers, there is no piece of construction equipment more 2 00:00:40.000 --> 00:00:42.000 essential than the tower crane. 3 00:00:42.000 --> 00:00:47.000 These heavy lifting machines dominate city skylines, hoisting materials and machinery 4 00:00:47.000 --> 00:00:50.000 to some of the highest construction sites on Earth. 5 00:00:50.000 --> 00:00:55.000 They have become a part everyday life in almost every major city as contractors race to build 6 00:00:55.000 --> 00:01:00.000 high-rise after high-rise, and more than 100,000 can be found in operation around the world 7 00:01:00.000 --> 00:01:02.000 at any given time. 8 00:01:02.000 --> 00:01:07.000 Despite how common tower cranes are, they often seem to appear in the sky out of nowhere 9 00:01:07.000 --> 00:01:10.000 leaving many of us wondering how they got there in the first place. 10 00:01:10.000 --> 00:01:15.000 The vast majority are erected using mobile cranes that are larger in size, but obviously 11 00:01:15.000 --> 00:01:19.000 this cannot always be done when you are building a record-breaking structure and taller cranes 12 00:01:19.000 --> 00:01:21.000 simply don’t exist. 13 00:01:21.000 --> 00:01:25.000 Some construction sites in dense urban areas may not have enough space for a large mobile 14 00:01:25.000 --> 00:01:31.000 crane either, and many projects also require tower cranes to be erected in stages so that 15 00:01:31.000 --> 00:01:34.000 they rise in unison with the constructed portion of the building. 16 00:01:34.000 --> 00:01:38.000 In these scenarios, the cranes must raise themselves to the final working height all 17 00:01:38.000 --> 00:01:42.000 on their own using a method known as climbing, and that is what we will be looking at in 18 00:01:42.000 --> 00:01:43.000 today’s video. 19 00:01:43.000 --> 00:01:49.000 In general terms, climbing a tower crane simply refers to the process of adding or removing 20 00:01:49.000 --> 00:01:53.000 sections of the mast in order to increase or decrease the overall height. 21 00:01:53.000 --> 00:01:58.000 The concept is fairly straightforward in principle, but it is quite difficult to execute safely 22 00:01:58.000 --> 00:02:03.000 in the field with catastrophic consequences if anything should go wrong. 23 00:02:03.000 --> 00:02:07.000 It is one of the most dangerous operations that can be performed with a tower crane, 24 00:02:07.000 --> 00:02:11.000 and it is only carried out when absolutely necessary to complete a project. 25 00:02:11.000 --> 00:02:16.000 Before climbing can begin, a tower crane must first be erected to an initial height using 26 00:02:16.000 --> 00:02:18.000 a suitable mobile crane. 27 00:02:18.000 --> 00:02:22.000 The process begins by constructing a stable foundation, which usually consists of a large 28 00:02:22.000 --> 00:02:27.000 concrete slab reinforced with steel rebar, and this takes place about a month before 29 00:02:27.000 --> 00:02:31.000 the crane goes vertical so that the concrete has enough time to cure. 30 00:02:31.000 --> 00:02:35.000 Once the concrete has reached its full strength, the first steel truss section of the mast 31 00:02:35.000 --> 00:02:41.000 is lifted into place, and it is secured with anchor bolts that are embedded in the foundation. 32 00:02:41.000 --> 00:02:44.000 Additional sections are then stacked on top of one another to complete the tower portion 33 00:02:44.000 --> 00:02:49.000 of the crane, and they are fastened together with high-strength steel bolts. 34 00:02:49.000 --> 00:02:53.000 The mast is topped off with a slewing unit, which is basically a turntable that allows 35 00:02:53.000 --> 00:02:58.000 the top of the crane to rotate, and this serves as a base for the operator’s cab and lifting 36 00:02:58.000 --> 00:02:59.000 components. 37 00:02:59.000 --> 00:03:03.000 The exact arrangement of the top assembly varies depending on the type of tower crane, 38 00:03:03.000 --> 00:03:08.000 but the one shown here has a hammerhead configuration with a cathead and a fixed jib that cannot 39 00:03:08.000 --> 00:03:10.000 be moved up or down. 40 00:03:10.000 --> 00:03:14.000 The cathead is the first component to be installed on top of the slewing unit, followed by the 41 00:03:14.000 --> 00:03:19.000 counter jib and working jib, and these are connected with steel tie rods that help to 42 00:03:19.000 --> 00:03:21.000 transfer loads to the mast. 43 00:03:21.000 --> 00:03:26.000 Once the top assembly is complete, a counterweight is then added to the counter jib, which normally 44 00:03:26.000 --> 00:03:29.000 consists of several concrete slabs. 45 00:03:29.000 --> 00:03:34.000 The counterweight helps to balance the load when the crane is performing a lift, effectively 46 00:03:34.000 --> 00:03:39.000 reducing the bending moment, or torque, that must be carried by the mast. 47 00:03:39.000 --> 00:03:44.000 Since the working jib is fixed on this particular crane, a trolley system must be used to adjust 48 00:03:44.000 --> 00:03:49.000 the radius of the hook so that the load can be positioned closer or further from the mast. 49 00:03:49.000 --> 00:03:54.000 This is not the case for luffing jib tower cranes, however, as they can adjust the radius 50 00:03:54.000 --> 00:03:57.000 simply by raising or lowering the working jib. 51 00:03:57.000 --> 00:04:01.000 In either case, the ability to change the position of the load makes it possible to 52 00:04:01.000 --> 00:04:06.000 perfectly balance the crane on top of the mast, and this is essential for the climbing 53 00:04:06.000 --> 00:04:08.000 process to be carried out safely. 54 00:04:08.000 --> 00:04:12.000 When a tower crane is ready to be climbed, a steel climbing frame is first assembled 55 00:04:12.000 --> 00:04:17.000 around the base of the tower, and it is lifted up to the underside of the slewing unit. 56 00:04:17.000 --> 00:04:21.000 The frame has a square cross-section with a lattice structure around three sides, but 57 00:04:21.000 --> 00:04:25.000 the front is left open so that new mast sections can pass through. 58 00:04:25.000 --> 00:04:30.000 The top is securely fastened to the underside of the slewing unit with high-strength steel 59 00:04:30.000 --> 00:04:34.000 bolts, and a hydraulic jack at the bottom is positioned over a push point on the existing 60 00:04:34.000 --> 00:04:35.000 mast. 61 00:04:35.000 --> 00:04:39.000 A new mast section is then hoisted up to the frame, where it is either placed on a steel 62 00:04:39.000 --> 00:04:44.000 tray or suspended from a guide rail that extends out above the opening. 63 00:04:44.000 --> 00:04:48.000 At this point, the top of the crane must be perfectly balanced over the jack before it 64 00:04:48.000 --> 00:04:53.000 can be lifted, which is accomplished by placing a weight on the hook to offset the counterweights. 65 00:04:53.000 --> 00:04:58.000 An additional mast section is typically used for this, and it is positioned at a precise 66 00:04:58.000 --> 00:05:03.000 radius from the mast so that there is no net moment applied onto the climbing frame. 67 00:05:03.000 --> 00:05:07.000 The crane top essentially behaves like a large balance scale during the climb, and it could 68 00:05:07.000 --> 00:05:11.000 topple off the mast if its center of gravity is not in line with the jack. 69 00:05:11.000 --> 00:05:16.000 In addition, the climbing frame is not designed to carry significant torsion, and it is extremely 70 00:05:16.000 --> 00:05:20.000 important that the crane is not slewed during the climbing process. 71 00:05:20.000 --> 00:05:24.000 The new mast sections are therefore arranged in a straight line on the ground to eliminate 72 00:05:24.000 --> 00:05:29.000 any need to rotate the crane, and the operator will usually leave the cabin during the climb 73 00:05:29.000 --> 00:05:32.000 so that the crane cannot be slewed accidentally. 74 00:05:32.000 --> 00:05:36.000 Once the crane is confirmed to be in balance and all safety checks have cleared, the hydraulic 75 00:05:36.000 --> 00:05:40.000 cylinder is then pressurized to take the weight of the crane top, and the slewing unit is 76 00:05:40.000 --> 00:05:43.000 unbolted from the top of the mast. 77 00:05:43.000 --> 00:05:47.000 The cylinder is used to lift the climbing frame along with the top of the crane until 78 00:05:47.000 --> 00:05:51.000 there is enough clearance to insert a new mast section, which usually requires several 79 00:05:51.000 --> 00:05:54.000 strokes depending on the cylinder’s length. 80 00:05:54.000 --> 00:05:58.000 The mast section can then be maneuvered inside the frame, where it is bolted to the underside 81 00:05:58.000 --> 00:06:03.000 of the slewing unit, and the hydraulic cylinder is depressurized so that the bottom of the 82 00:06:03.000 --> 00:06:06.000 new section engages with the top of the existing mast. 83 00:06:06.000 --> 00:06:11.000 After the joints are securely fastened, the cylinder is retracted and repositioned on 84 00:06:11.000 --> 00:06:17.000 the next push point, and the whole cycle can repeat until the crane reaches the desired height. 85 00:06:39.000 --> 00:06:43.000 Once the process is complete, the climbing frame will either be lowered down the mast 86 00:06:43.000 --> 00:06:48.000 or removed entirely until it is needed to raise the crane higher or to bring it back 87 00:06:48.000 --> 00:06:50.000 down at the end of construction. 88 00:06:50.000 --> 00:06:55.000 Now, up to this point, we have only talked about tower cranes that climb externally on 89 00:06:55.000 --> 00:07:00.000 the outside of a building, however they can also climb internally on the inside of a building. 90 00:07:00.000 --> 00:07:04.000 In this scenario, the weight of the crane is carried by the constructed portion of the 91 00:07:04.000 --> 00:07:09.000 building, which can increase the lifting capacity and reduce costs by eliminating the need for 92 00:07:09.000 --> 00:07:10.000 a tall mast. 93 00:07:10.000 --> 00:07:16.000 The process begins in the same way as before by erecting a crane on top of a concrete foundation, 94 00:07:16.000 --> 00:07:19.000 but the tower must now include a climbing section at the bottom that will be used to 95 00:07:19.000 --> 00:07:22.000 lift the crane later on. 96 00:07:22.000 --> 00:07:26.000 As the building is constructed around the mast, two steel collars are installed approximately 97 00:07:26.000 --> 00:07:31.000 three stories apart, which connect the crane to the building’s structural system. 98 00:07:31.000 --> 00:07:35.000 Climbing rails extend between the collars down the inside of the open shaft, and these 99 00:07:35.000 --> 00:07:40.000 provide support for a hydraulic jack that is positioned inside the mast climbing section. 100 00:07:40.000 --> 00:07:44.000 When the crane is ready to be climbed, the tower is unbolted from the foundation, and 101 00:07:44.000 --> 00:07:48.000 the hydraulic cylinder is pressurized to take the its weight. 102 00:07:48.000 --> 00:07:52.000 The cylinder is then used to lift the crane upwards until the bottom of the mast reaches 103 00:07:52.000 --> 00:07:56.000 the first collar, while a ratcheting system ensures that the crane cannot fall back down 104 00:07:56.000 --> 00:07:58.000 the shaft. 105 00:07:58.000 --> 00:08:03.000 As additional floors are added to the building, a third collar is installed three stories 106 00:08:03.000 --> 00:08:09.000 above the first two, and the crane can then be lifted from the bottom collar to the middle one. 107 00:08:15.000 --> 00:08:20.000 At this point, the bottom collar is no longer needed, so it is removed and re-located another 108 00:08:20.000 --> 00:08:26.000 3 stories above, thus allowing the whole process to be repeated as the building stretches higher. 109 00:08:26.000 --> 00:08:30.000 When construction is finally complete, the tower crane will either be disassembled using 110 00:08:30.000 --> 00:08:35.000 a larger mobile crane, or a smaller crane will be hoisted to the top of the building 111 00:08:35.000 --> 00:08:39.000 that can be dismantled by hand once the tower crane is removed. 112 00:08:39.000 --> 00:08:43.000 Tower cranes play an essential role in countless construction projects all around the world, 113 00:08:43.000 --> 00:08:48.000 and their ability to climb upwards entirely on their own means there is virtually no limit 114 00:08:48.000 --> 00:08:49.000 to how high we can build. 115 00:08:49.000 --> 00:08:53.000 These awesome machines always get the job done safely and efficiently, just like the 116 00:08:53.000 --> 00:08:57.000 sponsor for today’s video, NordPass. 117 00:08:57.000 --> 00:09:00.000 We all know that using a unique password for every website is the best ways to protect 118 00:09:00.000 --> 00:09:05.000 your online accounts, but it can often be difficult to remember all these passwords 119 00:09:05.000 --> 00:09:07.000 and time-consuming to type them into webpages yourself. 120 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