Visayas State University College of Engineering DEPARTMENT OF CIVIL ENGINEERING Baybay, Leyte GEng 112 General Surveying II
Name: Joycelyn H. Uy #$%# Co&rse an! 'ear: BSCE()
Date erforme!: De December ", ", Date S&bmitte!: Jan&ary ), #$%)
TRIANGULATION FOR A BRIDGE SITE La!ra"!ry E#er$i%e N!& ' I&
In"r!(u$"i!n) *+e met+o! of s&rveying calle! triang&lation is base! on t+e trigonometric roosition t+at if one si!e an! t-o angles of a triangle are no-n, t+e remaining si!es can be com&te!. /&rt+ermore, if t+e !irection of one one si!e si!e is nono-n, n, t+e t+e !ire !irect ctio ions ns of t+e rema remain inin ing g si!e si!es s can can be !ete !eterm rmin ine! e!.. 0 tria triang ng&l &lat atio ion n syst system em cons consis ists ts of a seri series es of 1oin 1oine! e! or over overla la in ing g tria triang ngle les s in -+ic -+ic+ + an occa occasi sion onal al si!e si!e is meas meas&r &re! e! an! an! remaining si!es are calc&late! from angles meas&re! at t+e vertices of t+e triang triangles les.. *+e vertic vertices es of t+e triang triangles les are are no-n no-n as triang triang&la &latio tion n stations. *+e si!e of t+e triangle -+ose lengt+ is re!etermine!, is calle! t+e base line. *+e lines of triang&lation system form a net-or t+at ties toget+er all t+e triang&lation stations.
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O*e$"ive+%,) %. *o estab establis lis+ + t+e contro controll oints oints for a lo- or!er or!er triang triang&la &latio tion n system 2consisting of a single 3&a!rilateral4 nee!e! to stae o&t a site for a s+ort(san bri!ge. #. *o learn +o- to aly aly t+e aro5 aro5imate imate met+o! met+o! of a!1&sting a!1&sting a 3&a!rilateral an! +o- to !etermine lengt+ of t+e bri!ge an! t+e lengt+s of ot+er &nno-n & nno-n si!es of t+e 3&a!rilateral.
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In% In%"ru"ru-e en"% n"% an( an( A$$ A$$e%%!rie !rie% %) Engineer6s *ransit, Sta!ia ro!, C+aining ins, an! H&bs or egs
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Pr!$e(ure) %. *+e t-o en! oints !e7ning t+e lengt+ of a roose! 2or imaginary4 bri!ge -as establis+e! an! t-o ot+er oints -it+in t+e vicinity of t+e bri!ge site in or!er to form a triang&lation 7g&re in t+e s+ae of a 3&a!rilateral. *+ese oints -ere calle! 0, B, C, an! D -it+ line 0B !e7ning !e7ning t+e lengt+ an! centerline centerline of
t+e roose! bri!ge. egs or +&bs -ere &se! to mar t+ese oints. #. Lines 0D an! BC -ere !esignate! as t+e base line an! c+ec base, resectively. *+eir resective lengt+s -ere meas&re! acc&rately t-ice an! t+e mean meas&rements -ere recor!e! as t+e act&al lengt+ of eac+ line. ). *+e instr&ment -as set & an! levele! at 0 an! eac+ +ori8ontal angle abo&t t+e station -as meas&re! in t-o reetitions. *+e observe! val&es -ere recor!e! accor!ingly. 9. n a similar rocess, t+e +ori8ontal angles at stations D, B, an! C -ere also meas&re!. ;. *+e observe! an! calc&late! val&es -ere t+en tab&late! accor!ingly. V&
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/or Correction:
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DISCUSSION)
*able % an! # s+o-s t+e station an! 7g&re a!1&stment, resectively. n t+e 7rst a!1&stment, all t+e observe! +ori8ontal angles abo&t a station -ere 1&st a!!e!. *+e s&m -as t+en s&btracte! from )"$o. *+e !ierence -as t+en !ivi!e! by t+e n&mber of angles abo&t t+e station. *+e res<ing val&e is t+en a!!e! algebraically to eac+ angle in or!er to mae t+e s&m of all angles abo&t eac+ station e3&al to )"$ o. O+ile in t+e secon! a!1&stment, t+e s&m of t+e interior angles of t+e 3&a!rilateral m&st be e3&al to 2n(#4%@$ o, -+ere Pn6
reresents t+e n&mber of si!es. n t+e t+ir! table, t+e oosite angles at t+e intersection of t+e !iagonals s+o&l! be e3&al. *+e val&es of t+ese angles -ere revio&sly a!1&ste! in earlier a!1&stments an! -ere comare! an! t+e !ierence bet-een t+em -as !ivi!e! by 9. *+e com&te! correction -as t+en a!!e! to smaller air of angles an! s&btracte! to t+e larger air. n t+e last table, it s+o-s t+e trigonometric con!ition. t -as satis7e! by t+e means of com&tations involving t+e sines of t+e angles. *+e angles -ere a!1&ste! so t+at t+e com&te! lengt+ of an &nno-n si!e oosite a no-n si!e -ill be t+e same regar!less of -+ic+ of t+e fo&r ro&tes is &se!. n t+is manner, ro&te % an! ) -ere com&te! an! its average -ill t+en reresent as t+e com&te! !istance of BC or t+e c+ec base. VI&
C!n$lu%i!n) *+erefore, t+e control oints for a lo- or!er triang&lation system 2consisting of a single 3&a!rilateral4 nee!e! to stae o&t a site for a s+ort( san bri!ge -as establis+e!. *+e alication of t+e aro5imate met+o! of a!1&sting a 3&a!rilateral -as also learne!, so as to !etermine t+e lengt+ of t+e bri!ge an! t+e lengt+s of ot+er &nno-n si!es of t+e 3&a!rilateral.
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D/ resentation R Control S&rveys by 1betco
