Strength of column embedded in footing with new - e

Strength of column embedded in footing with
new reinforcement
Autor(en):
Tsujioka, S. / Inoue, Kazuo / Imai, Katsuhiko
Objekttyp:
Article
Zeitschrift:
IABSE reports = Rapports AIPC = IVBH Berichte
Band (Jahr): 60 (1990)
PDF erstellt am:
14.04.2016
Persistenter Link: http://dx.doi.org/10.5169/seals-46486
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273
Strength of Column Embedded in Footing
with New Reinforcement
Resistance d'une colonne encastree dans une semelle de fondation
Tragwiderstand von Stahlhohlstützen in Stahlbetonfundamenten
TSUJIOKA
Kazuo INOUE
Lecturer
Fukui Inst of Tech
Fukui, Japan
Assoc Prof
Osaka University
Osaka, Japan
S.
1.
Katsuhiko IMAI
M. HIRAYAMA
Manager
Kawatetsu Steel
Koube, Japan
Struct Engineer
Ohbayashi-gumi
Osaka, Japan
INTRODUCTION
The RHS column base embedded in the RC footing is commonly
employed in the rigid column-footing connections and is capable
of resisting the large bendmg moments. However, at the RHS
exterior columns in the frame subjected to the lateral loads as
shown in Fig.l, due to the loss in the bearing strength of concrete
as a results of the failure of the cover concrete it is more awkward
that the strength of the embedded RHS exterior column-footrng
connection is greater than the füll strength of the RHS column.
To avoid such premature concrete failure in the RHS exterior
column-footing connection, an improved embedded type with the
U-reinforcing bars arranged on the outside of the embedded RHS
column is proposed. The advantages of such column base type are
that the shear force and the bending moment can be smoothly
transmitted from the RHS column to the foundation and the RC
tie-beam through the U-reinforcmg bars and the concrete.
Lateral Load
RHS Column
RC Tie-Beam
KISULTS
Cover
Concrete
Foundation -
j
Fig.l
2. TEST
I
»1
/
RHS Exterior ColumnFootmg Connection
As shown m Fig.2, there are three possible collapse mechanisms. Based on the the assumption of a
uniform distribution of the bearing stress over the füll width ofthe steel section, the ultimate strength of
the column-footing connection under the lateral loading is obtained.
The tests were conducted to evaluate the inelastic behavior, the lateral stiffness (KRc), the yield strength
(Qy) and the ultimate strength(Qp). The geometrical configurations of ten speeimens are shown in
Fig.3 and are summarized in Table L The test variables are the arrangement ofthe reinforcement, the
number of the U-reinforcmg bars and the direction af the applied lateral load. Typieal test results are
shown in Figs.4 and 5.
The following conclusions can be drawn from the test
Qps
Opc
Qpf
results
1) The lateral stiffness of the embedded column is
estimated by the results of the analysis including Füll Plastic Df
Plastic Hinge
the effect ofthe rotation resistance ofthe tie-beam. Equivalent FlC Section vy
2) The yield load and the collapse load of the improved
Ty^
<T>*Tir
T<Ty
embedded RHS exterior column base are well pre¬
dicted by the present method through tests.
Shear Pane£A
Pz
3) The U-reinforcmg bars of the improved embedded
*
<7<Fc
o<Fc
Fe
RHS exterior column base is most effective m pre¬
Concrete
Cover
of
resistance.
the
deterioration
,Qpc,Qps)
(Qpf
Qp=Mm
venting
is ignored
4) When the reinforcing bars of the tie-beam termithe
at
crack
inner
nate at the exten or edge, a major
Fig.2 Collapse Mechanisms
side of the embedded column is restricted.
HH
274
STRENGTH OF COLUMN EMBEDDED IN FOOTING WITH REINFORCEMENT
Lateral Load
Positive
Negative
Column
too
Dl50xl50x6
KRc
QkN
(H-150xl50x7xlO)
QP
Top U-Reinforcing Bare
(2D13* or 3D16»
RC Beam(D-375x330)
Qy
_
Main Bars:4D16^,4D13^,
Stirrup: D10<8>100
-0.04
Rc(iad.)
(2D13* or 2D16*)
Main Bars (To Column)
4™^
Main Bar»
(To Footing Edge)
0.08
0.04
Bottom U-Reinfoncing Bars
B
500
No.3
*M^> m
-100
925_
Fig.3 Test Speeimens
Specimen
No
Column
150x150x6
1
No2
No3
No4
No5
No6
No7
No8
No9
100
Q(kN)
U Reinforcing Bars
Arrangement
KRc
Loading
Upper
Lower
of Main Bars
2D130
2D130
To Column
None
None
To Footing Edge
Positive
2D130
2D130
To Footing Edge
Negative
Positive
3D160
2D160
To Column
Negative
Positive
50
Positive
/
Negative
flf
Qy
0.04
0.08
Rc(rad.)
/50--
Negative
H 150x150x7x10
2D130
2D13<|>
No 10
To Footing Edge
To Column
Positive
No.5
Positive
-100
Table
Summary of Test Speeimens
1
100
KRc
Q(kN)
50
Eis
V
/0i
Efc
LE
J
Punching Shear (No.3,5)
Bending Cracking (No.l,9,10)
Concrete Crushing (No.2,4,6,8)
>
La
Lb
/
>
///
/f
u
/
*
0 08
0.04
Rc(»d.)
No9
-100
Füll Plasufication (No.7)
Fig.5 Crack Pattern and Failure Modes
Qp
/
i
-0.04
\P
Fig.4 Typieal Q-Rc Diagrams

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