Inqaku loBugcisa noKhuseleko oluBalulekileyo: Esi sisicatshulwa semfundo koovimba, hayi ubalo olumileyo, uyilo lolwakhiwo, okanye incwadana yemigaqo yokusebenza. Iifomyula, iimodeli zenkxaso kunye nemizobo zidluliselwe kumxholo wokuqala ngaphandle kokuqinisekiswa kobuchwephesha okanye ukulungelelaniswa nemimiselo yanamhlanje. Umthamo wokuthwala, ukuzinza, imithwalo, izixhobo, amajoyina kunye nesiseko sento ethile kufuneka igqitywe yinjineli yoluntu eqinisekisiweyo ngokusekelwe kwimigangatho esebenzayo, idatha ye-geotechnical kunye nemeko yangempela yesakhiwo. Imifanekiso iyafundisa kwaye ayimeli iiprojekthi eziqinisekisiweyo zeSavo Kusić.
Ubalo olungagungqiyo kunye noyilo lweziseko ezixhasayo aziyonxalenye yonikezelo olutsha lwenkampani. Ujoliso lwangoku lwemveliso lubandakanya iifestile zomthi, iifestile zomthi-aluminiyam kunye neminyango yesiko. Kwifestile ethile okanye iprojekthi yocango, ungathumela isicelo sekowuti.
Ubume kunye nokwahlulwa komthwali
Izinto zenkxaso: uzinzo lwangaphakathi nangaphandle
Izinto zokuthwala zezi:
Iintonga ezilula ezikwaziyo ukuhambisa kuphela i-tensile okanye i-compressive force enomgca wohlaselo ungqamene ne-axis yentonga. Oku kuthetha ukuba iintonga kwiiqhina ziboshwe kunye namalungu apho kungabikho ukungqubuzana, kwaye imikhosi yangaphandle ihlasela amaqhina. Iinkxaso eziquka kuphela iintonga ezilula zibizwa ngokuba zii-trusses.
Iintonga ezixhathisayo ekugobeni - imiqadi - inokuhambisa yomibini imikhosi enemigca yohlaselo ihambelana ne-axis yentonga, kunye nemikhosi emigca yohlaselo ihambelana ne-axis yentonga okanye etyekele kuyo ngokungenasizathu. Imiqadi ifumana amandla aqhelekileyo, amandla aguquguqukayo, amaxesha okugoba kwaye, kwimeko enikiweyo, amaxesha e-torsion. Ezo zikumaqhina zinokubotshwa ngeehenjisi okanye ngeeengile eziqinileyo.
Inkxaso kunye ne-clamps inqanda inkxaso ukuba ihambe ukuya kwiindawo ezizinzileyo kwinqwelomoya okanye kwisithuba. Inkxaso nganye iyakwazi ukudlulisa amandla kwicala elithile elidlula kwi-node emisiwe. Ukuba kukho inkxaso enye kuphela kwi-node exhaswayo - indawo yokuxhasa - ibizwa ngokuba yi-movable bear yenkxaso yendawo. Ukuba i-node ixhaswa zizixhaso ezimbini, ibizwa ngokuba yi-immovable bed yenkxaso eflethi, okanye ibhedi yecarrier line. Ibhedi emileyo yenkxaso yendawo ifuna izixhaso ezintathu.
Ukucofa ngakunye kwentonga ekwaziyo ukugoba kuyakwazi ukuhambisa umzuzu wokupinkisha olele kwinqwelomoya ethile. Kwiimeko ezininzi, i-bearing engenakushukunyiswa ixhunyiwe kwi-clamp, ukwenzela ukuba kwimeko yenkxaso yeflethi kukho izixhaso ezimbini kunye ne-clamp enye, kwaye kwimeko yenkxaso yendawo kukho izixhaso ezintathu kunye neentambo ezintathu. Iintshukumo kunye nojikelezo lobungakanani obuthile bunokwenzeka kwiindawo ezixhasayo kunye nokucinezelwa.
Inani elifunekayo lezinto zokuzinza kwenkxaso lifumaneka kwiimeko zokuzinza ngaphakathi nangaphandle. Inkxaso i-internally stable xa indawo ye-inter-room ye-nodes yenkxaso iqinisekiswa ngenani elaneleyo leentonga ukwenzela ukuba inokutshintshwa kuphela xa ezinye okanye zonke iintonga zitshintsha ubude. Inkxaso yeflethi ezinzileyo yangaphakathi ibizwa ngokuba yi rigid plate. Inkxaso yangaphandle okanye izinzile ngokupheleleyo xa indawo ephakathi kwee-nodes kunye nesikhundla sazo ngokweendawo eziqingqiweyo zendiza, okanye indawo inokutshintsha kuphela kwinqanaba leenguqu kubude beentonga, ukuhamba kwezixhaso okanye ukujikeleza kwe-clamping.
Izibiyeli ezisicaba
Elona nani lincinane leentonga ezifunekayo kuzinzo lwangaphakathi kunye nenani elincinane leentonga kunye nezixhaso ezifunekayo kuzinzo lwangaphandle lwetruss ene s rods, a inkxaso kunye k nodi zezi:
s =2k -3
s + a =2k, (3 ≤_ a)
Umqathango wokuqala ufezekisiwe xa ukuxhaswa kusenziwa ukuqala kwintonga enye ngokudibanisa iinqununu ezingaphezulu kunye neentonga ezimbini nganye, apho iintonga apho enye i-node idityaniswe kufuneka ingalali kumgca ofanayo othe ngqo.
Isibiyeli esine-s1 iintonga ezilula, s2 iintonga ezixhathisayo ekugotyweni, e iiengile eziqinileyo, a1 ixhasa, a2 iipntshisi kunye k iindawo zangaphakathi, okanye ngaphandle zizinzile xa:
s1+ s2+ e ≥ 2k -3
s1+ s2+ e + a1+ a2 ≥2k, (a=a1+ a2≥3)
Sl.1
I-angle nganye eqinileyo inokutshintshwa yintonga elula. Ukuba kwindawo enye i iintonga ziqhagamshelwe ngokungqongqo enye kwenye, inani leengile eziqinileyo kuloo nodi ngu i-1. Xa i-overhangs yeentonga (i-consoles) zibalwa njengeentonga, iziphelo zamahhala kufuneka zibalwe njengama-nodes. Isibiyeli kwikhiwane.1nge s1=9, s2=7, e=5(iphawulwe emfanekisweni) kunye k=12ngaphakathi izinzile. Xa ii-engile eziqinileyo4kwaye5masiyitshintshe ngamajoyina kunye neentonga ezilula, eziphawulwe ngemigca eyaphukileyo emfanekisweni, emva koko s1=11, s2=7, e=3, ngelixa inani leendawo zokuhlala lingatshintshi.
Sl.2kwaye nam2b
Ukuba kwinkxaso enye kunye nenani elincinci elifunekayo lenkxaso, iintonga zomntu ngamnye okanye ii-angles eziqinileyo zitshintshwa zixhaso okanye i-clamps, inkxaso ilahlekelwa ukuzinza kwayo kwangaphakathi, umkhiwane.2a, b. Kwiinkxaso ezinjalo kukho amanye amathuba okuba uzinzo lungavavanywa njani. Ukuba p linani leepleyiti eziqinileyo zenkxaso ngaphandle kozinzo lwangaphakathi, ngelixa kufuneka kuqatshelwe ukuba intonga enye elula okanye intonga echasene nokugoba ihlangabezana neemeko zozinzo lwangaphakathi kwaye inokuqondwa njengeplate eqinile, kwaye ukuba z inani lokusebenzisana kumalungu, ukuzinza kwangaphandle kufuna ukuba: a + _ z_3p. Inani leempendulo eziphakathi kwindawo edityaniswe kuyo ipleyiti (umkhiwane.3,4,5) yi z=2(_kwaye-_1).
Sl.3kwaye4, ngokulandelelanayo
Sl.5
Isakhelo emkhiwaneni.6Iphindaphindwe kathandathu ngokwestatic indeterminate. Ukuba i-overhangs, engenalo impembelelo kwiqondo lokungaguquki kwe-static, ibalwa njengeentonga, ii-angles eziqinileyo apho zifakwe khona kwisistim kufuneka ziqwalaselwe kwaye iziphelo zamahhala ze-overhangs kufuneka zibalwe njengama-nodes (s=7, e=6, a=9, k=8). Kwezi ntlobo zenkxaso, uhlobo olufanelekileyo lweemeko zokuvavanya uzinzo lwangaphakathi nangaphandle lu:
3_s_ ≥3k-3;3s+a ≥3k, (a≥3).
Kwangaxeshanye, ukupasa akufuneki kubalwe njengezinti. Ngokuqhelekileyo, kwiimeko ezinjalo, indlela ekhawulezayo yokufikelela kwisigqibo malunga neqondo lokungaguquki kwe-static yenkxaso ngokusika iintonga okanye ukungabandakanyi ubuninzi be-static de kube ukuxhaswa ngokungathandabuzekiyo, ukuqinisekiswa kwe-statically kusele. Ngamacandelo amathathu aboniswe kwifig.7izixa ezintathu ezimileyo (amandla aqhelekileyo, amandla anqamlezayo, umzuzu wokugoba) azibandakanywanga.
Ukuba kwenye n0-amaxesha estatically indeterminate flat lattice zonke iintonga kwiinodi ziqhagamshelwe ngokungqongqo, idigri ye-static indeterminacy is
n = n0+2s – k.
Fig. 6
Sl.7
Inkxaso yendawo
Elona nani lisezantsi lenkxaso yeegridi zendawo ngu a=6. Ezi meko zilandelayo zisebenza kuzinzo lwangaphakathi nolwangaphandle:
s ≥3k -6; s + a ≥3k, (a≥6).
Umqathango wokuzinza kwangaphakathi udibene xa, ukuqala kwipleyiti enye ye-triangular, ii-nodes ezongezelelweyo kwisithuba ziboshwe ngeentonga ezintathu nganye, ezingamele zilale kwindiza enye. Ngale ndlela, igridi ye-spatial yohlobo lokuqala lwenziwa, uphawu lwayo kukuba isoloko iqulethe i-node enye apho iintonga ezintathu kuphela ziboshwe, kwaye igcina le mpawu naxa loo node eneentonga ezihambelanayo isusiwe.
Ngaphezu koko, iigridi zendawo zingenziwa ngokudibanisa amacwecwe angamanxantathu ngendlela yokuba iiplati ezimbini kunye neembini zidibaniswe neentonga ezintandathu, apho i-node nganye idibaniswe kwiiplati ezikufutshane kunye neentonga ezimbini. Ukudityaniswa kwamacwecwe amabini okanye iigridi zesithuba ezizinzileyo ezimbini zangaphakathi zinokuqondwa ngokudibanisa enye kunye neentonga ezintathu ezingadlulanga kuloo mdibaniso. Ekugqibeleni, iipleyiti ezintathu ze-triangular zinokudibaniswa nazo12yeentonga kunye nokuba nge po4intonga phakathi kwepleyiti nganye. Ngaphakathi, okanye uzinzo lwangaphandle lwenkxaso yendawo apho zonke iintonga zibotshelelwe ngokuqinileyo ekugobeni nasekujikeni, iimeko kufuneka zifezekiswe.
6s ≥6(k-1);6s + a ≥6k
Ngoko ke, umthwali kwifig.8yi24amaxesha ngokwestatically indeterminate, athi, njengangaphambili, anokuqinisekiswa ngokulula kakhulu xa iintonga ezine ezithe tyaba zisikiwe kwaye ngale ndlela izinto ezintandathu ezingaziwayo aziqukwanga kwisiko ngalinye (1amandla aqhelekileyo,2amandla anqamlezayo,2 mukugoba oment kunye1ixesha le-torsional). Ukuba sisusa uxhulumaniso lwe-f ngokufaka amajoyina kwiintonga okanye ukudibanisa kwazo, ke iimeko zozinzo zi:
6s – f ≥6(k-1);6s – f + a ≥6k.
Sl. 8
Umthwalo kunye neempendulo: imisebenzi ye-statics
Kwimeko yenkxaso yeflethi, imikhosi yangaphandle kufuneka ilale kwindiza yenkxaso, kwimeko yokuxhaswa kwendawo, ingaba nesigxina esingenasizathu. Kwi-trusses, kucingelwa ukuba umthwalo uhlasela kwiindawo.
Amandla asebenzayo abangela ukuchasana kwee-external elements, ukusabela kwezixhaso C kwinkxaso kunye nemizuzu yokucinezela E kwiipntshisi. Ukuchasana kwe internal elements zenkxaso - i-cross-sectional forces - yile: i-axial forces S kwiintonga ezilula; kwiintonga ezixhathisa ukugoba kunye nokujija amandla aqhelekileyo okanye amade N, amaxesha okugoba M, ixesha lokujija okanye ixesha lokujija T kunye namandla anqamlezayo Q. Ukunganyangeki kwezinto kunokubangela utshintsho kwiqondo lokushisa kunye nokukhulula izixhasi.
Ubungakanani bezinto zomntu ngamnye kunye nokumisela i-voltages ebonakala kuyo ngumsebenzi we-Material Resistance. Xa umisela amaxabiso amileyo, izinto ezisetyenzisiweyo zibalulekile kuphela kwinqanaba lokuba umthwalo osisigxina uxhomekeke kuwo. Ezinye iimpawu zezinto eziphathekayo zithathelwa ingqalelo kuphela xa kuziwa kwimpembelelo yenkxaso yokunyakaza okanye utshintsho lweqondo lokushisa (i-shrinkage, flow) okanye xa kufuneka kubalwe i-deformations. Ngokubanzi, iigida kufuneka zivavanywe kwiimeko ezahlukeneyo zomthwalo ezingafuneki ukuba zenzeke ngaxeshanye (umthwalo osisigxina, umthwalo oluncedo, umthwalo womoya, umthwalo wekhephu). Kucingelwa ukuba i-elastic deformations incinci kangangokuba inokungahoywa ngokunxulumene nemilinganiselo yenkqubo - kwaye oku kudla ngokuba njalo - umgaqo we-superposition uyasebenza, ngokubhekiselele apho iimeko zomthwalo ngamnye kunye nezinye iimpembelelo zinokujongwa ngokwahlukileyo kwaye amaxabiso abalwe kwi-static okanye yejometri ubuninzi bodityaniswe kunye, kunye nolungiso oluthile lwamaxabiso ngokusebenzisa ukhuseleko olusisigxina kunye ne-coefficients akulunganga).
Izixhaso eziqinisekisiweyo
Iinxaki ezingaziwa nezikhoyo
Kwilattice eqingqwe ngokwestatically, a reactions of the supports and s axial forces ayaziwa, umiselo lukhona xa iletisi ine k nodes.2_k_ inxaki (∑X=0kunye ∑Y=0) kwinqwelomoya i3k inxaki esithubeni. Kwinkxaso ecaba, izinto ezingaziwayo zinokuncitshiswa zibe s1 imikhosi ye-axial yeentonga ezilula, s2 amandla aqhelekileyo eentonga ezixhathisayo ekugotyweni, e ukugoba amaxesha kwii-engile eziqinileyo, a1 ukusabela kweenkxaso kunye a2 amaxesha okubamba. Amandla aguquguqukayo kufuneka anqunywe ukusuka kwimizuzu ekupheleni kweentonga kunye nemikhosi yangaphandle esebenza phakathi kweenodes. Kwindawo apho i iintonga eziqhagamshelwe ngokungqongqo ziqala ukuya kwiindawo ezingabamelwane, kwanele ukwazi i-1 mi-oment - ehambelana nenani leengile eziqinileyo - kuba ukumiselwa komnye umzuzu ongaziwayo kwindawo nganye enjalo kukho imeko yokulingana ∑M=0. Ukumisela s1+imis2 + e + a1 + a2 izinto ezingaziwayo zisekhona2_k_ iimeko zolingano.
Iimeko zolungelelwaniso lwamandla angaphandle kwizixhaso ezisicaba
Iimpendulo zepleyiti zixhasa ukuphumla kwindawo enye emileyo kunye nenye eshukumayo (umkhiwane.9) zifunyanwa ngomzobo kusetyenziswa iipoligoni ezinamandla. Umgca wokuhlaselwa kwamandla B uyaziwa kwaye unolwalathiso lwenkxaso kuloo ndawo, kwaye umgca wokuhlaselwa kwamandla Ka kufuneka udlule kwi-intersection of forces B kunye ne-P. Ibalwa ukusuka kwimeko Ma =0, H =0kunye neMb =0zimiselwa ngokuthe ngcembe ngamandla B, C kunye no-A. Ukuphumla ipleyiti kwiibheringi ezintathu ezihambayo (umkhiwane.10) ichanekile kuphela xa imigca yokusabela ingadibanisi kwindawo enye. Iimpendulo zimiselwa ngokomzobo kusetyenziswa ii polygons zamandla okanye ngokubala kusetyenziswa iiequation zemizuzu ngokunxulumene namanqaku apho imigca emibini yohlaselo yemikhosi idibana khona.
Sl.9
Fig. 10
Kwimeko yokuxhaswa kwe-statically enqunywe ngaphandle kozinzo lwangaphakathi, ngaphezu kweemeko zokulinganisela kwamandla angaphandle ngokubanzi, iimeko zokubambisana nazo ziyaziswa, ezibonisa imfuno yokuba amajoyina akakwazi ukufumana ixesha lokugoba. Ngako oko, umgca wokuhlaselwa wokuphendula uKa wesakhelo esine-hinged ezintathu kwi-Fig. 11 mora idlula kwi-joint g, kwaye i-plate echanekileyo ingaba nokulinganisa kuphela xa imikhosi emithathu esebenza kuyo (P, Kb kunye nokunyanzeliswa kwi-joint = Ka) idibanisa kwinqanaba elinye. Ukuze ufumane iimeko zokulingana eziqulethe enye kuphela engaziwayo nganye, kukulungele ukubala kunye namacandelo amileyo okuphendula i-A kunye ne-B kunye namacandelo C kunye no-D kunye nomgca odibanisa amanqaku axhasayo. Ukususela kwimiqathango ye-Mb = 0 kunye no-Ma = 0, imikhosi A kunye ne-B ifunyenwe, kwaye ukusuka kwimeko ye-joint Mg = 0, ngenxa yemikhosi ehlasela i-plate ekhohlo, i-force C ifunyenwe, kunye nemikhosi ekwi-plate echanekileyo, i-D. 12. Kumthwalo onikiweyo apha, eyona ndlela ikhawulezayo yokufumana isiphumo ngumzobo. Isibiyeli esinamalungu ngokomkhiwane. 13. Amacandelo anqamlekileyo emikhosi yangaphandle ehlasela inkxaso ifunyenwe ngumbhede omileyo, amandla F afunyenwe kwi-∑H = 0. Icwecwe II liphumle kwiindawo g1 kunye g2 kwiipleyiti I kunye III, kunye nepleyiti IV e-g3 ngo-III. Amandla athe nkqo kwiindawo ezihlangeneyo G1, G2, G3 kunye ne-reaction E imiselwa kwimeko yokulingana kwepleyiti II okanye IV, kwaye emva koko inyathelo ngenyathelo iimpendulo B,D, izimisele.
Fig. 11 kunye 12, ngokulandelelana
Fig. 13
Ukumiselwa kweesayizi zangaphakathi ezimileyo
Amandla e-Axial S yeentonga ezilula, njengomthetho, zibonwa zilungile xa zingamandla oxinzelelo, kwaye zingalunganga xa zingamandla oxinzelelo. Ngendlela efanayo, uphawu lwamandla aqhelekileyo N kumqadi lumiselwa. Amandla aqhelekileyo Ni kwinqanaba i licandelo elihambelana ne-tangent ukuya kwi-axis ye-beam kwindawo i yesiphumo R sayo yonke imikhosi esebenza kwi-beam kwicala elinye lenqaku i. I-transverse force Qi icandelo eliqhelekileyo kwi-axis yentonga kwinqanaba kunye nelinye kunye nesiphumo, kunye nomzuzu wokugoba Mi ngumzuzu wesiphumo (umkhiwane 14). Ukumiselwa kwamanani N, Q kunye M kwenziwa rhoqo ukusuka kumandla omntu ngamnye kunye namacandelo awo ahambelanayo kunye ne-perpendicular kwi-axis yentonga ngaphandle kokumisela isiphumo R. Ingqungquthela yezalathiso ezilungileyo iboniswe kwifig. 15.
Fig. 14 kunye 15, ngokulandelelana
Ekubeni iimpendulo zenkxaso zichongiwe ngegraphical, amandla aqhelekileyo, amaxesha okugoba kunye nemikhosi eguquguqukayo inokumiselwa ukusuka kwipolygon yamandla kunye nesicwangciso apho amandla anikwe ngokwesikhundla. Umzekelo, kwikholamu ekhohlo yesakhelo esinehenjisi ezintathu kwifig. 11 icandelo elithe nkqo lamandla Ka ngamandla aqhelekileyo (negative), inxalenye ethe tyaba ingamandla anqamlezayo (negative), kunye Mi = Kari ixesha lokugoba, elingalunganga xa ixesha elibangela uxinzelelo ngaphakathi lithathwa njengelilungile.
Kuzo zonke iindawo apho iintonga zijingiwe khona, imiqathango ∑X=0, ∑Y=0 mayifezekiswe. Iigridi ezenziwe ngendlela elula - ngokudibanisa iinqununu ngeentonga ezimbini nganye - zihlala zinendawo enye ubuncinane apho zidibana khona iintonga ezimbini. Ngokususa iindawo ezinjalo, olu phawu luyagcinwa. Ukubalwa kwamandla e-axial kwiintonga kunokuqhutywa ngokucombulula ngokuthe ngcembe iiequations ezimbini nezimbini ezingaziwayo.
Isisombululo somzobo sifunyanwa ngokwakha i-force plan (isicwangciso seCremana) ngokomkhiwane. 16. Amandla angaphandle P1 ukuya ku-P6 ayalingana. Imikhosi kwiintonga Si izimisele ngokuthe ngcembe ukusuka kwindawo 1 kwaye isuka kwi-node ukuya kwi-node ngendlela ephawulwe ngayo. Ukumakishwa kwemikhosi kwakhona kwenziwa ngokolandelelwano olugqitywe ngalo. I-node nganye ihambelana nepolygon yamandla kunye nesalathiso esiqhubekayo sotolo, apho iimpawu zemikhosi kwiintonga zilandela. Ukuba icandelo lenziwe ngokuxhaswa kwaye ukuba kwiindawo apho iintonga zisikwa khona imikhosi esebenza kwezo ntonga isetyenziswe njengamandla angaphandle, inxalenye nganye ye-lattice ilingana. Koku, inkqubo ye-Culmann's irekhodwa, apho amandla kwintonga engafanelekanga inokumiselwa ngokuzimeleyo ngokuzimeleyo kwamanye amandla.
Fig. 16
Kwisisombululo sohlalutyo lwengxaki yokuseta ii-equations nomntu ongaziwayo, inkqubo ka-Ritter ibaluleke kakhulu. I-lattice inqunywe ukwenzela ukuba iintonga ezintathu zichaphazeleke ngokusikwa. Imikhosi kwimivalo yecandelo isetyenziswe kwindawo nganye ye-truss njengemikhosi yoxinzelelo, ukusuka kwi-node ukuya kwicandelo. Iimeko zokulingana zisebenza kwindawo nganye yeletiyisi. Ukudityaniswa kweentonga ezimbini kunye nezimbini ezinqamlezayo yindawo yomzuzwana xa kumiselwa amandla kwintonga yesithathu (Ritter’s point). Ukuba i-ri ngumgama wamandla Si ukusuka kwinqanaba lomzuzu i, kwaye Mi ngumzuzu wamandla asebenzayo kunye neempendulo zenkxaso ngokumalunga nenqaku i, ngoko amandla kwintonga inikwe ngentetho
Si = ± Mi/ri
Fig. 17
Fig. 18
Ngokwefig. 17 kunye 18 amandla kwiintonga ezinqamlezileyo zezi:
On = -Mn/rn; Un-1 = Mn-1/rn-1;
Dn = Md/rd; Ln = Mv/rv.
Xa ulwakhiwo lwegraphical lunganikezeli ngokuchaneka okwaneleyo, indawo apho amanqaku omzuzu d kunye no v kunye nemigama rd kunye rv kufuneka ibalwe. Ukubalwa kwamandla D kunye L, ezi ntetho zilandelayo zifanelekile ngakumbi, apho kuphela iimpawu zegridi zivela njengamanqaku omzuzu (fig. 19, 18):
D = (Mu/hu – M(o)/ho) * (d/λd), (35)
Ln = ± Ql ± (Mn tgβn + M’n tgγn)/hn.
Kwiilathisi ezinamabhanti ahambelanayo, imikhosi D kunye ne-L inokufumaneka ngokuthe ngqo kumandla anqamlezayo:
D = Umbuzo/isono__φ_; L=±Q
Sl.19
Ukuhambisa umthwalo kunye nemigca yempembelelo
Ukuba inkxaso ilayishwe ngumthwalo ohambayo, imikhosi egxininisiweyo kumgama oqhubekayo phakathi komnye nomnye, ngoko ke iimvavanyo kufuneka zenziwe kwi-most unfavoble load positions. Ngomqadi olula kwiinkxaso ezimbini, i-force enkulu ye-transverse Qmax inokufumaneka ngokusebenzisa i-A-polygon, kunye nomzuzu omkhulu wokugoba Mmax usebenzisa i-polygon yekhonkco kwinkqubo yemikhosi apho inkxaso ihamba khona.
Xa umisela umgca wempembelelo kumthamo omnye omileyo okanye wejometri, kunye nomthwalo Pm=1ehamba ecaleni kwebhanti elayishiweyo yomphathi, kwindawo nganye yomthwalo m isetyenziswa phantsi kwamandla, ukusuka kumgca we-zero omnye, ixabiso elibaliweyo ηm lobungakanani obufunekayo. Umgca odibanisa isiphelo sale mibutho ngu line of influence. Imigca yempembelelo yomzuzu wokugoba Mi kunye ne-transverse force Qi kwinqanaba i le-beam exhaswa kwiindawo a kunye ne-b yimigca ethe tye ga kunye gb amacandelo abo kwii-verticals ezixhasayo aa’ = xi (=M’i= ye_A).1) kunye no_bb’_ = x’i (=M’‘i ye-B=1) (ikhiwane.20). Umgca wempembelelo yonyanzeliso A inikwa ngumgca gb, olungelelwaniso olukwi-axis ethe nkqo ngu-a aa’=1.
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Umgca wempembelelo wobungakanani obume obunye benkxaso emiselwe ngokwezibalo uquka imigca ethe tye ehambelana neepleyiti eziqinileyo zekhonkco elinyanzelweyo lekinematic edalwe kukungabandakanywa kobuninzi obuceliweyo. Imigca inqumla kwi-verticals ngamanqaku omzuzwana, okanye kwiindawo apho iipleyiti zixhomekeke khona. Indawo eboshwe ngumgca we-zero, umgca wempembelelo kunye neendawo ezimbini ezibizwa ngokuba yimpembelelo yendawo. I-divider (inqaku elinguziro lomgca wempembelelo) yahlula iindawo ezilungileyo kunye nezibi zomphezulu wempembelelo.
Njengoko ηm imele impembelelo yamandla ashukumayo Pm=1kubungakanani obufunekayo Z, ngu Pmηm impembelelo yonyanzeliso Pm, ngelixa inkqubo yemikhosi P ibangela impembelelo Z=∑Pη. Amaxabiso alinganiselweyo empembelelo maxZ kunye ne-minZ aya kufumaneka xa inkqubo eshukumayo yamandla adibeneyo adibeneyo isetiwe ukuze awona mandla maninzi aphindaphindwe ngowona mandla mkhulu. Xa eyona ndawo ingathandekiyo ingaziwa ngokuqinisekileyo, impembelelo evela kumgca wempembelelo kufuneka ibalwe ecaleni ngeendawo ezahlukeneyo zomthwalo (inkqubo ephindaphindayo).
Kumthwalo owabiwe ngokulinganayo ngokulinganayo p t/m ngu Z = _∫_p dx η = pF, apho F bubungakanani obuphawulweyo bendawo echaphazelekayo yendawo echaphazelayo. Kumthwalo ongaphelelanga wobude obulinganiselweyo c kunye nemilo yerectilinear yomgca wempembelelo (Fig.58) umthwalo kufuneka ubekwe ukuze η1 = η2 (c1= cxi/l; c2= cx’i/l), ngoko sifumana Z = pc (ηi + η1)/2. Kugqithiso lomthwalo olungathanga ngqo, umgca wempembelelo uphakathi kwe ordinated ηn kunye ηn+1 utshintsho kumgca othe ngqo, fig.21.
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