Sap2000 - Explain
Sap2000 - ExplainInsertion PointThs. Phm Tun Minh
Insertion PointMt mt ct thanh c gn tnh cht v vt liu v hnh hc m
qua m t c mt ct ngang ca mt hoc nhiu phn t thanh. Mt ct c nh ngha
mt cch c lp v c gn n cc phn t.Local Coordinate System.Tnh cht mt ct
c nh ngha lin quan n h ta a phng ca mt phn t thanh nh sau: Trc 1 dc
theo trc ca phn t. N vung gc vi mt ct v i qua giao im ca hai trc
trung ha ca mt ct. Trc 2 v 3 c nh ngha trong mt phng mt ct. Thng
thng trc 2 dc theo kch thc chnh ca mt ct(chiu su depth), cn trc 3
th i dc theo kch thc ph ca mt ct(chiu rng width), nhng iu ny khng
bt buc.[footnoteRef:1] [1: Xem trang 14 phn hng dn s dng
Sapbasic.]
Material propertiesTnh cht vt liu ca mt ct c xc nh lin quan n vt
liu nh ngha trc . Tnh cht vt liu c s dng trong mt ct: M un n hi,
e1, ng vi cng ko nn v cng chng un. M un chng ct, g12, ng vi cng
chng xon v ct chng ct. Khi lng ring, m, tnh ton khi lng phn t. Trng
lng ring, w, tnh ton ti trng bn thn. Chn loi thit k, ides, ch dn
liu phn t s dng mt ct ny nn c thit k thp, b tng, nhm, thp t hp, hoc
khng thit k.(Geometric properties and section stiffnesses)c trng
hnh hc v cng mt ctSu c trng hnh hc c s dng, cng vi c trng vt liu,
to cng cho tit din. l: Din tch mt ct ngang(cross section area), a.
Ta c cng ko nn ca mt ct l a. e1. Mmen qun tnh(Moment of inertia),
i33, quay quanh trc 3 un cong trong mt phng 1-2, v m men qun tnh,
i22, quay quanh trc 2 un cong trong mt phng 1-3. Tng ng ta c cng
chng un ca tit din l i33.e1. Hng s xon(torsion constant), j. Ta c
cng chng xon ca tit din l j. g12. Ch rng hng s xon khng cng m men
qun tnh cc, tr l hnh trn. [footnoteRef:2] [2: Xem Roark v
Young(1975) hoc Cook v Young(1985) c nhiu thng tin hn.]
Din tch ct(shear areas), as2 v as3, tng ng l khng ct trong mt
phng 1-2 v 1-3. Tng ng ta c cng chng ct ca tit din l as2 . g12 v
as3 . g12. [footnoteRef:3] [3: Cng thc tnh ton din tch ct ca mt ct
in hnh hnh 2 trang 19 quyn Sapbasic.]
a, j, i33, hoc i22 bng khng s tng ng vi cng theo m bng 0. V d,
mt thanh dn c th c m hnh ha bng cch t j = i33 = i22 = 0, v mt thanh
dm thng un trong mt phng 1-2 c th c m hnh bng cch t j = i22 = 0.
as2 v as3 bng khng tng ng gy ra bin dng ct tng ng bng khng. Kt qu
l, mt din tch ct bng khng(zero shear area) c hiu l cng v cng. cng
ct c l i nu cng un tng ng bng khng.Shape typeVi mi mt ct, su c trng
hnh hc(a, j, i33, i22, as2, as3) c th xc nh trc tip, tnh ton t kch
thc mt ct xc nh(theo cc cng thc ca Sc bn vt liu), hoc c t mt file c
s d liu. iu ny c xc nh bi loi hnh dng, sh, xc nh bi ngi s dng: Nu
sh = G(mt ct chung chung), su c trng hnh hc phi c xc nh mt cch r
rng. Nu sh = R, P, B, I, C, T, L hoc 2L, su c trng hnh hc c tnh ton
mt cch t ng t kch thc mt ct xc nh nh m t bn di. Nu sh l mt gi tr bt
k khc( v d W27x94 hoc 2L4x3x1/4), su c trng hnh hc c xem t file c s
d liu. Xem bn di.
Automatic section properties calculation(t ng tnh ton c trng hnh
hc)Su c trng hnh hc c th c tnh ton mt cch t ng t kch thc xc nh ca
nhng tit din n gin[footnoteRef:4] . Kch thc yu cu cho mi hnh dng nh
hnh di. [4: Xem hnh 3 trang 21 ti liu Sapbasic.]
Ch rng kch thc t3 l chiu su ca tit din theo phng trc 2 v c vai
tr chnh khi tnh i33.Tnh ton c trng hnh hc t ng hin ti p dng cho
nhng loi hnh dng sau: sh = R: Rectangular section(mt ct hnh ch nht)
sh = P : Tit din ng rng hoc c sh = B : tit din hp. sh = I : tit din
ch I. sh = C : Tit din thp gc ch C sh = T : Tit din ch T sh = L :
Tit din thp gc. sh = 2L : Tit din hai thp gc.Section property
database file( file c s d liu c trng mt ct)c trng hnh hc ca mt ct c
th c ly t mt trong nhng file d liu. Mt s c s d liu c cung cp trong
Sap2000, bao gm: AISC.pro v AISC3.pro : hnh dng thp xy dng ca vin
khoa hc M. AA6061-T6.pro : Hnh dng t hp nhm. CISC.pro : hnh dng thp
ca vin khoa hc Canada. SECTIONS8.pro : y ch l mt file c s d liu
copy ca AISC3.pro.File thm vo c cung cp bao gm hnh dng tiu chun ca
cc nc khc.Bn phi to file c s d liu ring ca bn s dng chng trnh
PROPER m c mua t CSI[footnoteRef:5] [5: Computer and Structural,
Inc.]
c trng hnh hc c lu theo n v xc nh khi c s d liu c to. Nhng ci ny
c chuyn i mt cch t ng n n v s dng khi vo Sap2000.
Mi loi hnh dng lu trong file c s d liu c th lin quan n mt hoc
hoc hai nhn(label)khc nhau. V d, loi thp W36x300 trong file
AISC.pro c th c c nhn W36x300 hoc nhn W920x446.Bn c th chn mt file
c s d liu khi nh ngha mt mt ct thanh. File d liu ny c th c thay i
bt k lc no. Nu khng chn file d liu no th file d liu mc nh
SECTIONS8.pro s c chn. Bn c th copy bt k c trng no n file d liu
SECTIONS8.pro.Tt c file d liu c trng mt ct, bao gm file
SECTIONS8.pro, phi c t trong th mc cha file d liu hoc th mc ci t
Sap2000.
