Pipe Strut vs. Laced Strut

Pipe Strut vs. Laced Strut Chiew Sing-Ping School of Civil and Environmental Engineering NANYANG TECHNOLOGICAL UNIVERSITY 9 July 2015

Pipe Strut vs. Laced Strut Pipe Strut Laced Strut 2

PLAXIS Soil-Structure Interaction Analysis Wall (Beam element) Strut (Bar element) 3

PLAXIS Soil-Structure Interaction Analysis Wall deflection profile Distribution of wall bending moments d hmax = 68.9 mm Wall max BM = +82.6 knm/m and -107.8 knm/m 4

PLAXIS Soil-Structure Interaction Analysis Strut forces compression is -ve 5

Pipe Strut vs Laced Strut Part 1: What is Pipe Strut? Production Process: ERW, Spiral, UOE Press-Forming & Roll-Forming Part 2: Why use Pipe Strut? Design of Pipe Strut vs. Laced Strut Section Efficiency Study Part 3: How to use Pipe Strut? Pipe Connectors for Fixed and Free Ends 6

How to produce a pipe? What is Pipe Strut? ROLL-FORMING SPIRAL-WELDING UOE PRESS-FORMING ELECTRIC-RESISTANT WELDING 7

ERW Electric Resistant Welding 8

UOE Press-Forming 9

Spiral Welding 10

Why use Pipe Strut? Design of pipe strut according to EC3 1. Section classification 2. Non-dimensional slenderness 235 1 93.9 f y L cr i 1 1 3. Buckling curve 0.21 0.49 hot finished cold formed 4. Reduction factor 1 2 2 2 0.2 0.5 1 5. Buckling resistance N b, Rd Af y M 0 11

Design of Laced Strut 2 types of built-up struts Laced Strut Battened Strut Chord Lace Batten Module 12

Design of Laced Strut Efficient Laced Strut: z' I z z I yy z y (affected by module length a) Strong laced members y y z' 13

Design of Laced Strut Section properties of laced strut with two identical members Effective second moment of area: I 2 eff 0.5h0 A ch (EC3-1-1, 6.4.2.1) A ch Area of the chord h 0 distance between the centroids of chords 14

I Design of Laced Strut 2 2 ' ' 0.5h A z z 0 ch I yy Achiy I I ' z z yy ' 0.5h i 2 0 Ach 2 y Ach 2 0 2 y 0.5h i 1 h i y 0 2 radius of gyration about y-axis 15

Effect of Global Stiffness Buckling modes: h i y 0 2 h i y 0 2 Out-of-plane buckling In-plane buckling 16

Effect of Module Length a Buckling mode with inappropriate module length between lacing members: Local In-plane chord buckling 17

Effect of Laced Member Buckling modes with weak laced members: Laced member buckling Torsional buckling 18

Section Efficiency Study Strut Force h Strut Strut length L Strut force (kn/m) Strut spacing (m) Force (kn) 160 6 960 210 6 1260 250 6 1500 290 6 1740 700 6 4200 1000 6 6000 1300 6 7800 2000 6 12000 2300 6 13800 2500 6 15000 Strut spacing @ 6m c/c 19

Compressive Resistance 6000 kn Weight kg/m for pipe and laced struts for various length Grade S275 Strut L (m) Pipe λ Weight (kg/m) 12 711 12 0.56 207 15 762 12 0.65 222 20 813 12 0.81 237 25 914 12 0.90 267 30 965 12.7 1.03 298 35 1016 14.3 1.14 352 40 1067 14.3 1.24 370 45 1067 16 1.39 415 50 1168 16 1.42 455 55 1219 16 1.49 475 60 1219 20 1.63 591 Strut L (m) Laced λy Weight (kg/m) 12 610 229UB101 0.57 222.6 15 610 229UB113 0.7 248.6 20 610 229UB125 0.93 275.2 25 610 305UB149 1.12 328.2 30 686 254UB170 1.23 374.4 35 838 292UB176 1.22 387 40 914 305UB201 1.29 442 45 914 305UB224 1.43 493 50 1016 305UB249 1.48 548 55 1016 305UB272 1.58 598 60 1016 305UB314 1.73 691 20

Weight (kg/m) Compressive Resistance 6000 kn 800 700 600 500 400 300 Pipe Laced 200 100 0 10 20 30 40 50 60 70 Strut length (m) 21

Compressive Resistance 12000 kn Weight kg/m for pipe and laced struts for various length Grade S275 Strut L (m) Pipe λ Weight (kg/m) 12 1016 16 0.39 395 15 1016 16 0.49 395 20 1016 16 0.65 395 25 1168 14.3 0.71 406 30 1168 16 0.85 455 35 1168 19 0.99 540 40 1219 20 1.09 591 45 1320.8 19 1.13 611 50 1320.8 22.2 1.25 711.6 55 1320.8 27 1.39 860.6 60 1320.8 30.2 1.51 960.3 Strut L (m) Laced λ y Weight (kg/m) 12 838 292UB194 0.41 426.6 15 838 292UB194 0.51 426.6 20 914 305UB201 0.65 442 25 1016 305UB222 0.76 488.4 30 1016 305UB249 0.89 547.1 35 1016 305UB272 1.01 599 40 1016 305UB314 1.15 691.5 45 1016 305UB393 1.29 864 50 1016 305UB437 1.43 961 55 1016 305UB487 1.56 1071 60 3/1016 305UB393 1.72 1297 22

Weight (kg/m) Compressive Resistance 12000 kn 1500 1300 1100 900 700 pipe Laced 500 300 10 20 30 40 50 60 70 Strut length (m) 23

Resistance & Slenderness vs. Steel Grade Design resistance of strut = 1500kN Suitable pipe sections with unit-weight (kg/m) for various strut length are given below Strut L (m) Pipe Weight (kg/m) Slenderness λ Resistance (kn) S275 S355 S460 S275 S355 S460 4 323.9 6 47 0.41 0.47 0.53 1564 1986 2602 8 355.6 6.3 54.3 0.74 0.84 0.96 1570 1887 2396 12 406 7.1 70.3 0.98 1.11 1.27 1672 1864 2167 15 457 7.1 79 1.09 1.23 1.4 1678 1821 2032 20 457 10 110 1.46 1.66 1.89 1503 1557 1671 25 508 12 147 1.65 1.87 2.13 1630 1674 1775 30 508 16 194 1.99 2.25 2.57 1533 1560 1632 35 508 25 298 2.36 2.68 3.04 1708 1730 1794 40 508 32 376 2.73 3.1 3.53 1638 1655 1707 24

Resistance (kn) Slenderness Slenderness Resistance & Slenderness vs. Steel Grade When the slenderness is beyond the range of 1.0-1.5, the high strength steel contributes little to compression resistance. 3000 2500 2000 1500 1000 500 S275 S355 S460 Slend275 Slend355 Slend460 4 3.5 3 2.5 2 1.5 1 0.5 0 0 5 10 15 20 25 30 35 40 45 Strut length (m) 0 25

Influence of Steel Grade Design resistance =1500 kn Suitable pipe sections with different steel grade Strut L (m) Pipe S275 S355 S460 Weight (kg/m) Pipe Weight (kg/m) Pipe Weight (kg/m) 4 323.9 6 47 273 6 39.5 219.1 6.3 33 8 355.6 6.3 54.3 323.9 6.3 49.3 273 8 52.3 12 406 8 78.6 355.6 8 68.6 355.6 8 68.6 15 406 10 98 406 8 78.6 355.6 12 101 20 457 10 110 457 10 110 406 14 135 25 508 12 147 508 12 147 457 14.2 155 30 508 16 194 508 16 194 508 16 194 35 508 25 298 508 25 298 508 25 298 40 508 32 376 508 32 376 508 32 376 26

weight (kg/m) Influence of Steel Grade 400 350 S275 S355 S460 300 250 200 150 100 50 0 0 10 20 30 40 50 Strut Length (m) 27

Advantages of Pipe Strut Design of pipe strut is simpler; lesser chance of making a mistake Smaller diameter pipe strut will not be competitive Larger diameter pipe strut can span longer and/or take higher strut force without any intermediate restraint (i.e. no king post, runner beam or splay; hence, higher productivity) No clear advantage in using higher grade steel because design govern by buckling for long span strut 28

How to use Pipe Strut? Hydraulic Jack Free End for manual pre-loading Mast Section Connector Fixed End Automatic hydraulic system 29

Example of Free End Type 1 Common specification: Φ800*1450 mm Adjustable range: 0-30 cm 30

Example of Free End Type 1 Detachable End 31

Example of Free End Type 2 Steel wedge to lock the strut after pre-loading 32

Example of Free End Type 3 33

Example of Free End Type 3 Typical connection between Free End and Waler Steel pipe Detachable End Hydraulic Jack Steel wedge Filling pile Bolted connection Free End Hydraulic Jack Waler 34

Example of Fixed End 900mm Twin Waler 700mm 500mm 300mm 500mm 35

Flexible Cone Connectors Twin Waler Stiffener Flexible cone connector 36

Flexible Cone Connectors Stiffener 500mm φ 300mm φ 37

Connection between Mast Sections Bolted connections and connectors Connector Bolts 38

Concluding Remarks Use of laced struts in Singapore is highly developed and efficient because of our many years of experience of MRT construction. For pipe strut to be more competitive and productive, it has to space wider and span longer without any intermediate restraint. This will naturally lead to the use of larger diameter pipe struts. However, pre-loading and connection design will be more challenging. Some clever device for manual or automatic pre-loading and flexible connectors will have to be developed. 39