Member Descriptions [name, end point names, weight (if in objective function), second power of length (if a constraint), member category, Obj/Con/Exc (put in objective function, use as a constraint or exclude from computations), flags] For assembly purposes, only the name and end point names are of interest. The other information may be of interest after A Practical Guide to Tensegrity Design has been consulted. # struts <Member> struta pa2' pa1 -1.0 sqr(0.75) 1 Con * <Member> strutb pb2' pb1 -1.0 sqr(0.75) 1 Con * <Member> strutc pc2' pc1 -1.0 sqr(0.75) 1 Con * # interlayer tendons <Member> xltc pc1' pc1 1.0 0.5 3 Obj * <Member> xltb1 pb1 pc1 1.0 sqr(0.178) 3 Con * <Member> xltb2 pb1' pc1 1.0 sqr(0.37) 3 Con * <Member> xlta1 pa1 pb1 1.0 sqr(0.178) 3 Con * <Member> xlta2 pa1' pb1 1.0 sqr(0.37) 3 Con * # end tendons <Member> basea pa2 pa1 1.0 0.5 2 Con * <Member> enda' pa2' pa1' 1.0 0.125 4 Con * <Member> endb' pb2' pb1' 1.0 0.125 4 Con * <Member> endc' pc2' pc1' 1.0 0.125 4 Con *
In-Situ Member Lengths These are the lengths of the members when they are in place and prestress is applied. The strut lengths are from pin insertion point to pin insertion point, as are the tendon lengths. The values are in model units. struta: 0.75 strutb: 0.75 strutc: 0.75 xltc: 0.52349 xltb1: 0.178 xltb2: 0.37 xlta1: 0.178 xlta2: 0.37 basea: 0.707107 enda': 0.353553 endb': 0.353553 endc': 0.353553 baseb: 0.706905 basec: 0.706576
Relative Member Force Magnitudes These values are useful for developing an assembly strategy for the structure. The tighter tendons are much easier to tie in place early on, while the looser tendons can be left to the last. This information is also used to adjust tendon lengths since the measured length of a tendon will be shorter for a highly-stressed tendon with the same in-situ length as a tendon which is not so stressed. struta: -1.23205 strutb: -0.756595 strutc: -0.75 xltc: 0.52349 xltb1: 0.482199 xltb2: 0.594721 xlta1: 0.785004 xlta2: 0.968612 basea: 0.542416 enda': 0.785501 endb': 0.482123 endc': 0.407942 Average tendon force magnitude: 0.619112
Construction Lengths (in millimeters and halves) The construction length of a tendon is less than the in-situ length since when the tendon is measured off it isn't under any prestress force. The construction length for the strut represents the length of the 3/16-inch-diameter wooden dowel. The tendons were made of 12-lb.-test braided nylon fishing line. In this case, the attachment point at the hubs was a simple metal pin stuck into the end of the strut, so no member-length adjustments were necessary. Prestress forces are assumed not to affect strut lengths. Elongation of Tendon of Unit Cross Section Under Force of Average Magnitude (fraction)> .02 Length Scale Factor> 200/0.75 Strut and Tendon Hub Adjustments - s;t> 0 0 struta: 200 0 strutb: 200 0 strutc: 200 0 xltc: 137 1 xltb1: 46 1 xltb2: 97 0 xlta1: 46 1 xlta2: 95 1 basea: 185 1 enda': 92 0 endb': 93 0 endc': 93 0
Aspension Tower II with Point Labels
structure file: marcus/x3l3marcusa.rc variable file: marcus/x3l3marcusa.dat digit list: src/mm.dls |
CONTACT: Bob Burkhardt Tensegrity Solutions Box 426164 Cambridge, MA 02142-0021 USA e-mail: bobwb@juno.com |