La loai san rna trong do nhirng thanh phan c6u tao san nhu ban, hoac ban d~m
diroc thuc l1i~11d~ trd thanh mot khdi duy nhat va lien tue d moi di~m ngay tli luc due
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176
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- Hinh thirc ban ddm dl1C1cap dung trong truong hop nhip cua san tirong d6i Ibn, neu dung hinh thirc ban thi dO day cua ban se Ibn khong kinh t6, do do rna phai them
cac dam d~ giam bot chieu dai nhip cua ban. I
- Vbi san co ket cau theo hinh thirc ban ddm se dat diroc hieu qua kinh t6 khi san co nhip trung binh - Tuy nhian se t6n g6 van khuon hon loai san hinh thirc ban. M~t
duci cua san se khongbang phang va phai lam tran treo khi co yeu cau .
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2.2 Pftari lo~i : Theo hinh thirc chiu 111cco th~ phan thanh 2 loai : San mot 11~th6ng dam.
- San hai h~ th6ng dam.
a San mot h~ dam: (H4-3IA) ap dung khi mat bang san hep, Can chon phurrng chiu 111cd~ co nhip cua dam ngan nhat vci khoang each gilia cac dam tir In1 de'n 2m.
b San hai 11~darn : (H4-3IB.C) ap dung khi mat bang san rong so dd ke't ca'u duoc xem 1111111aban ke lel1 dam phu, ddrn phu g6i len dam chmh dat len cot.
b I - Sa do bo trf dam : Phuong cua h¢ dam diroc chon tuy thuoc vao su b6 trf chung cua ngoi nha va cac yeu cau khac.
Khi d~t dam chinh theo phirong doc nha, tran nha va ca gian nha diroc chieu sang tot hon nhung co th~ phai ke mot so dam phu len phan tuong tren 0 cira a nrong doc - hie do can d~t lanh to khoe de chiu lire tit mut dam phu truyen xu6ng. Trong tnrong hop dat dam chlnh theo phirong ngang nha, no se cung voi cot tao thanh khung ngang lam tang dQ cirng khong gian cua 0 cira,
Ngoai ra khi bo trf cot trong nha, can quan tam den nhirng yeu cau str dung ngoi nha nhu su sap xep day chuyen san xuat viec sir dung khong gian cua phong 6c ...
Trong pham vi moi nhip cua dam chinh co th~ bo tri mot, hai hoac ba dam phu, va nen xcp d~t the nao cho co mQt dam phl;l d~t theo trl;lc cQt.
Theo chu vi san, ban va dam co th~ ke trl!c tiep I~n tuang chiu Il!c (duai mut dam can d~t tam d~m betong cot thep) ho~c duc lien toan kh6i vai giang tUimg.
b2- Tham s6 kich thuac ban va dam:
- Dam chinh : dQ cao h clla dam chinh > 1/151, thuemg dung 1/S1 - 1/121 vai nhip cua dam chinh 1 trong khoang tit 5 den Sm.
- Dam phl;l : de.?cao h cua dam phl;l > 1/201' vai nh!p clla dam phl;l l' trong khoang 4 den 6m va khoang cach dam phl;l tit 1,5 - 2,5m.
- Ban: Khoi Iuqng betong clla san t~p trung phan Ian a ban~ do do can chQn chieu
- La loai san co sinm g6m cac ban va h~ dam tao thanh tren mat bang nhirng 0
hinh chir nhat vbi ti s6 gifta 2 canh >2. .
177 c- SU<mtren : (H4- 34c )
La lo~i san c6 suOn v6i ban d~t tren dam giii nhi~m Vl,1 ket cau m~t san, va ban duc li~n m~t duoi cua dam giii nhi~m Vl;) che dau suOn dong thai cung la m*t tran san. De thl!C hi¢n de dang lo~i san ban kep th(jng thuOng chung ta phai chon b6 luon van khuon
(1 ben trong than san. Do do rna lo~i san nay se tiet giam dang ke ve truy~n nhi~t, truyen am va chan dQng.
Tuy theo vi trf lien ket giiia ban va dam rna cau tao san betong c6t thep hlnh thirc ban dam diroc quy v~ 3 kieu each chinh nhu sau :
a- San duoi : (hoac dam IQ) (H4-34a), (H4-35).
San duoc due vci ban tren darn dum, d~t theo mot phtrong, hai phirong hoac dan 0
ca. Trong tnrong hop nay, khi co yeu cau can che dau siren thi co th~ cau tao them tran phang bang giai phap tran treo lOp trat tren lu6i thep ho~c tren lati gan vao su<m.
Lo~i san nay thu<mg duqc Ung d1:Jngcho co xucrng ho*c nha kho.
b- Ban kep : (H4- 34b)
day ban d mire dO be nhat co th~ trong khoang tit 6 de'n Iflcm. Theo yeu cau ky thuat chieu day cua ban khong ldy nho hon 5cm d6i vrri mal, 6cm d6i ydi san nha dan dung,
7CIll doi vrri san nha cong nghiep, Bcm d6i vdi san tren co xe di lai.
- Khi san ke true tie'p len tinrng doan ke len tircng gach khong be hon cac tri so sau cho cac bO phan : 12cm doi vrri ban, 22cm d6i vrri dam phu, 34cm doi vrri dam chinh.
Neu b~ day cua tirrrng khong du thi can lam them bo tru. Mut dam chmh phai ducc due
li~ll toan khdi vdi c¢t betong cot thep d~t d trong tutrng hoac sat tUdng.
c San 0 cd : San (J cd la mot dang d~c bi~t cua san co ban ke bon canh, K~t cau
cua san dUQCcau tao bdi h~ dam giao nhau theo 2 phuong, chia mat san thanh cac 0
ban k~ bon canh, khoang each giit8 cac dam khong qua 2m.
cr San 0 cd hinh vuong, chit nhat : Phuong cua dam duoc d~t song song vrri canh
Sail, ti so kich thinrc m~t bang san dUQCchon ld/ln khong nen qua 1,5, khi mat bang Sa11qua rong 110:)Ckeo dai can lam cac cot va dam chmh trung gian. (H4-32a + H4-33)
c2- San 0 co hinh qua tram : Phuong cua dam duoc chon xien goc 45° voi canh san, luc nay chieu dai san khong bi han Chef D~c diem cua phirong an dam dat xien la a ch6
cac dam ngan dc)t sat goc lam g6i nra dan hOi cho nhtrng dam dai giao nhau v6i no. Kh6i lirong betong cot thep gan gi6ng nhau so voi san 0 co dam thang nhirng se giam thieu diroc nhieu cot hon, r~t thich dung cho cac phong tien sanh, cira hang ... (H4-32b).
2.3- Ki~ueach cau tao :•
17X
Tlly tl1eo yell Call sue dtJng rna nell 11hilduqc cau t~o tlleo hai lo~i 11811ballg va n~ll doc.