TR Consulting
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FOR THE STUDENTSAs you all know, large scale suspension bridge design is not only related to static calculations, but to dynamics, vibration and aerodynamic as well as construction techniques. We receive a lot of inquiries from students who ask for more details, calculations etc. For those of you interested in some very basic calculations, here is a source code for a simple bridge calculation program you may compile in Basic, QB or VB. The following variables are used: N = Number of hanger wires on one side of main span cable, L = The total span between towers in meters, H = Distance between the hangers, F = Vertical distance from top of tower saddles to bottom of main cable (sag) , Q = specific load of girder inclusive traffic and safety factor ( kN / m ), RATIO = F / L ratio deciding type of curvature, Beta = angle at hanger, Zeta = Angle at hanger, So = Horizontal force ( kN) at tower top, S = Main span cable length (m) between towers, Sm = Main cable force in kN The program structure : Put an empty floppy disk in your A: drive a. ) Program declares variables b.) Asks if new data shall be entered c.) If yes, allows new data to be entered d.) Stores input data on the file "A: Brdata" e.) Displays the width / sag ratio and informs on choice of chain line or parabola calculation f.) Calculates, and asks if data shall be stored g.) Asks if the form of the main cables shall be calculated and stored The program will store the data for the cable geometry in a DXF form, so that it may be read by a graphic program like AutoCad etc. The program source code : ( Once upon a time written for fun in Basic. The source code has not been checked, so we advice you not to try and build a 1000 m span bridge at home.) SUSPENSION BRIDGE CALCULATIONS 10 COLOR 2,0 11 CLS: DIM N(15) : DIM N$(15): DIM Y(500):DIM TGALFA(500):DIM GR(500): DIM ALFA (100): DIM TGBETA(500):DIM BETA(500):DIM ZETA(500) 20 REM PROGRAM START 30 PRINT " PUT THE BRIDGE DATA FLOPPY DISK IN STATION A: " 50 INPUT "DO YOU WISH TO ENTER NEW DATA " ;J$: IF J$="Y" THEN 100 60 OPEN "I",#1,"A:BDATA" 70 IF EOF(1)THEN PRINT " NO AVAILABLE DATA ON DISK ":GOTO 50 80 INPUT #1,L,N,H,F,Q 90 GOTO 190 100 REM INPUT NEW DATA 110 INPUT "DISTANCE BETWEEN TOWERS OVER CROSSING I METERS " ;L 120 INPUT "NUMBER OF HANGER CABLES FROM CENTERLINE TO TOWER ";N 130 INPUT "DISTANCE BETWEEN HANGER CABLES IN METERS ";H 140 INPUT "VERTICAL DISTANCE FROM TOWER TOP TO BOTTOM MAIN CABLE I M ";F 150 INPUT "SPECIFIC LOAD OF BRIDGE GIRDER IN kN/m " ;Q 155 REM THE SPECIFIC WEIGHT OF THE GIRDER OF A 2 LANE 800 M BRIDGE IS 5.5 TON/M 160 OPEN "O",#1,"A:BDATA" 170 PRINT #1, ;L; ",";N;",";H;",";F;","Q 180 CLOSE # 1 190 REM CALCULATION OF RATIO F/L 200 RATIO =F/L 210 PRINT "RATIO OF F/L =" RATIO 220 FOR 1= 1 TO 500 :NEXT I 230 IF RATIO < 0.2 THEN PRINT "PARABOLA CALCULATION IS OK" 240 IF RATIO => 0.2 THEN PRINT "CHAIN LINE CALCULATION SHOULD BE USED" 250 REM PARABOLA CALCULATIONS 260 SO=(Q*L^2)/(8*F) 270 PRINT "HORIZONTAL FORCE So =" SO 280 REM LENGTH OF MAIN CABLE s 290 S=L*(1+2/3*(2*F/L)^2) 300 PRINT "THE MAIN CABLE LENGTH BETWEEN TOWERS S = " S "meter" 310 REM MAXIMUM TENSION IN MAIN CABLE Sm 320 SM=((Q*L/2)*(SQR(1+(L/(4*F))¨2))) 330 PRINT " MAXIMUM TENSION IN MAIN CABLE Sm = "SM "Kn" 340 INPUT " DO YOU WISH TO STORE THESE DATA ";J$: IF J$="Y" THEN GOTO 350 ELSE GOTO 380 350 OPEN "O",#3,"A:BDATA" 360 PRINT #3,RELSATION;",";SO;",";S;",";SM 370 CLOSE #3 380 INPUT "DO YOU WISH TO CALCULATE THE CABLE GEOMETRY ";J$: IF J$="Y" THEN GOTO 390 ELSE GOTO 4 390 INPUT "DO YOU WISH TO STORE THE DATA IN DXF FORMAT ";J$: IF J$="Y" THEN GOTO 400 ELSE GOTO 410 400 OPEN "O",#4,"A:BRFORM.DXF" : LET FLG=1:GOTO 420 410 OPEN "O",#2,"A:BRFORM": GOTO 430 420 REM THE MAIN CABLE GEOMETRY MAY NOW BE CALCULATED 421 GOSUB 770 430 FOR Z=0 TO N 440 x=(H*z) 450 Y(x)=(Q/(2*SO))*x^2 460 T=T+1 470 IF FLG=1 THEN GOSUB 640 480 REM THE ANGLE AT THE HANGER CABLE CLAMPS 490 TGALFA(x)=(Q/SO)*x 500 GR(X)=(180/3.1415)*ATN(TGALFA(X)) 510 REM CHANGE IN ANGLE OF THE MAIN CABLE OVER THE HANGER CLAMP 520 ALFA(X)= GR(X)-GR(C) 530 C=X 540 REM CHANGE IN MAIN CABLE ANGLE IF THE REST OF THE CABLE IS STRAIGHT 550 A=(L/2-X):B=(F-Y(X) :TGBETA(X)=B/A 560 BETA(X)=(180/3.1415)*ATN(TGBETA(X)) 570 ZETA(X) =BETA(X)-GR(X) 580 IF FLG=1 THEN GOTO 600 590 PRINT #2,X;",";Y(X);",";GR;",";ALFA(x);",";BETA (X);",";ZETA(X) 600 NEXT 610 IF FLG=1 THEN GOSUB 720 620 CLOSE #2 630 END 640 REM READ DATA FROM DISK 650 IF T=1 THEN GOTO 710 660 N$(1)= "LINE":N(2)=8:N(3)=0:N(4)=10:N(5)=(X-H):N(6)=20:N(7)=Y(X-H):N(8)=11: N(9)=X:N(10)=21:N(11)=Y(X):N(12)=0 670 PRINT #4,N$(1) 671 PRINT #4,N(2) 672 PRINT #4,"0" 680 FOR 1=4 TO 12 690 PRINT #4,N(I( 700 NEXT 710 RETURN 720 PRINT #4,"ENDSEC" 730 PRINT #4,0 740 PRINT #4,"E0F" 750 CLOSE #4 760 RETURN 770 PRINT #4,N(3) 775 PRINT #4,"SECTION" 780 PRINT #4,2 790 PRINT #4,"ENTITIES" 800 PRINT #4,N(3) 810 RETURN |
TR Consulting, Joh. Falkb.gt. 10, 5538 Haugesund, Norway. Tel: +47 52729124, Fax: +47 52724196, C.E.O. Cell phone. +47 90 616969 e-mail: trcons@online.no or trcons@start.no |