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MT SNG TO NHTRONGXY DNG TNG HMNH CAO T

NG

KTS. L Hoi Vit

Trn ThHng (chp bt)

y l gii php ang c p dng ti mt d n Vit Nam. Do d n vn cha hon

thnh nn cc thng tin c th skhng c nu trong bi ny. Sng kin ny do tp th

nhng ngi lm d n a ra. Bi ny ch cp n gii php nh mt cch ng dng

thnh cng PPLSTVM, cc gii php chi tit skhng c m t.

I. PHNG PHP THI CNG TOP DOWNPhng php Top-Down c quy trnh xy dng nhsau

1) Xy dng tng vy: chng bn hng ca tng hm, ngn st lt, chngthm nc.

2) Khoan cc nhi: khoan cc n su thit k, btng ct thp (BTCT) cc ncao y tng hm.

3) Lp t King-post: l thanh thp chu lc tm thi trong qu trnh thi cng tng hm(thanh mu trong hnh Top Down 1).

4)BTCT sn tng trt da trn hKing-post chu lc.5)o t n tng trt tip tc lm tng hm B1, sau l nhng tng hm tip

theo v mng nh. Song song l xy t tng trt ln cc tng lu trn cao. Ccthanh King-post c BTCT bc xung quanh trthnh ct chng cho ta nh(hnh Top Down 2).

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u im ca phng php hin ti: gim thi gian thi cng do xy dng cng lc cc tnghm v cc tng trn.

Phm vi p dng: p dng cho nhng cng trnh c thc hin ng tin (ngha l qutrnh xy dng khng bngng gin on).

II. BI TONTrong tnh hnh kinh tsuy thoi, nh u tkhng vn cung ng cho vic thi cngnn cng trnh sphi tm dng mt thi gian (khong 1-2 nm). Nhvy cc thanh King-post bng thp sbgkhi trong lng t lu ngy. Do , mt vn c t ra:

Lm thno cc thanh King-post khnng chu lc sau thi gian 2 nm hoc lu

hn na trong khi vn sdng phng php thi cng Top-Down m khng lm pht

sinh chi ph.

Bng kinh nghim v cch lm thng thng, ta c mt sgii php nhsau:

MK1: Nu lm cho King-post khng bg bng cch sn (ph) mt lp chng n mn thngn nga c tc gst, chi ph khng cao nhng khng m bo sngn gst chothanh khi lp t (v thanh King-post c thbtry xc lp sn phkhi ng xung lngt).

MK2: Nu lm thanh King-post to, dy hn th tng c thi hn chng n mn cathanh nhng iu ny li tng chi ph. Cha k, nu thanh King-post gp phi vtr c ncngm v khong cht n mn mnh th gii php ny khng khthi.

MK3: Nu dng vt liu mi (thp khng g, gm, si Carbon) chto thanh King-postth gii quyt trit khnng chng n mn ca thanh nhng iu ny lm tng chi ph vc thphi thay i cng nghthi cng.

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Vi mc ch cn t l thanh c khnng chng n mn vi thi gian khng hn ch(ligii l tng) th vic chn hng gii quyt sdng vt liu mi l hp l. Tuy nhin, yphi gii quyt vn cn li: vic tng chi ph (do sdng nguyn liu mi) mc chp nhnc v khng phi thay i nguyn l lm vic (phng php thi cng).

Thng sc trong bi ton Thng skthut tng ng

Khnng chng n mn vi thi gianca thanh King-post

bn (14)

tin cy (27)

Chi ph tng cao do thay i kch thcca thanh King-post

Cc nhn tc hi sinh ra bi chnh i tng (31)

Lng cht th(26)

Sdng cng ckhc phc mu thun kthut, chng ta c

(14, 31) = 15, 35, 22, 2 (27, 26) = 21, 28, 40, 3

Tcc nguyn tc sng to thu c trn, nguyn tc sng to 40 v 2 c ch . Theongn ngvt liu trong ngnh, b tng ct thp chnh l vt liu hp thnh.

Vy, thanh King-post thay bng ct b tng ct thp.

III. NH GIVic sdng ct b tng ct thp l phbin trong xy dng, hn na, cng nghang s

dng l khoan cc nhi. Nhvy, King-post sl on cc nhi ko di bng b tng ctthp (BTCT).

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Do c tnh ca BTCT l chng n mn rt tt, tui thgn nhvnh vin nn t yu cu biton t ra. Cng nghkhoan cc ang c sdng ti cng trng. Tuy gi thnh caohn thanh King-post bng thp nhng b li, cc ny trthnh ct ca tng hm nn stitkim c chi ph lm ct.

IV. KT LUNScc theo thit kban u

Trnh tthi cng tng tnhthi cng Top-Down, bqua bc lp t King-post

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Do chuyn cc thnh ct, nn cn tng kh nng chu lc ca cc, ngha l tng tit dincng nhtng chiu su cc. Kt qul chng ti gim slng cc so vi thit kbanu (gim 2/3 s ct) nn tit kim hn 100 tng v rt ngn thi gian thi cng 45ngy.

V. NHNG IU CN NI THMMt sbi ton con ny sinh khi trin khai gii php:

1. V cc BTCT sau ny trthnh ct, nn sai sthng ng cho php l nhhn so visai slm cc mng thng thng

2. V cc BTCT sau ny trthnh ct, nn phi to mi lin kt vi dm v sn tng hm sc lm sau theo cng nghTop-Down.

Theo cc bn, gii quyt nhng vn ny nhthno?

Cng bt m vi cc bn, nhng vn ny chng ti cng gii quyt xong. Nu cc bnc nhng vn cn trao i, xin lin htheo a ch: hoaiviet90@yahoo.com

Scc sau khi iu chnh