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International Journal of Mechanical And Production Engineering, ISSN: 2320-2092,
Volume- 4, Issue-9, Sep.-2016
COMPOSITE SLAB NUMERICAL STRENGTH TEST METHOD
UNDER M-K APPROACH
1
IZIAN ABD KARIM, 2KACHALLA MOHAMMED
1,2
Universiti Putra Malaysia
E-mail: [email protected], [email protected]
Abstract- The paper presents an experimental validation of proposed numerical strength determination function for profiled
deck composite slab (PDCS). The study is timely in finding solution to the costlier and mandatory laboratory procedure
required for the strength determination for PDCS. The study load carrying capacity is from the longitudinal shear capacity
estimation using slope-intercept method. The study yields to the formation of numerical load determination function for PDCS
and the validation test programme consisted of four shear span length under unrestrained conditions. The litmus test
comparisons of load capacity with the experimental test result shows good prospect of the numerical load model in determining
the strength capacity of PDCS.
Index Terms- Composite slab, Failure test load, Longitudinal shear, Slope-intercept method.
Fig. 1 can be transmitted effectively with the
development of longitudinal shear at the steel-concrete
interface. The shear bond failure is one of the three,
and most common failure modes associated with
composite slab [2, 4], flexural failure and shear at
support are the other modes of failure. Many studies
[6-8] result findings confirm the behavior of profiled
deck composite slab is affected by the bond failure in
the longitudinal direction.
The longitudinal shear failure mode (see 2-2 in
I. INTRODUCTION
The use of steel sheeting deck and concrete has been
one of the most popular composite constructions in the
globe [1-5]. The use of such system has numerous
advantages. For instance, the profiled sheeting can
serve as shuttering and shoulders’ wet concrete during
construction stage, and will act as tension
reinforcement within the composite slab system. Other
advantages include the effectiveness of the steel
sheeting deck and the hardened concrete in carrying
any addition loads that are consider during the design
in addition to supporting their self-weight.
Furthermore, unlike with conventional RC slab
design, the use of flexural reinforcement steel is
seldom required under this constructional method. The
mesh reinforcement mostly provided is for hydration
and shrinkage control only. Moreover, the method
gains more popularity because of eliminating
time-consuming erection and subsequent removal of
temporary forms at site, and the gained associated with
concrete strength during service through performing
the function of tensile reinforcement by the profiled
steel deck [4, 6].
The ultimate strength governs the design of composite
slab and the shear bond strength defines its capacity.
On general, the composite action between the profiled
steel sheeting deck and the hardened concrete like the
one
shown
in
Fig. 1) happen before reaching the plastic bending
capacity of the composite slab, and will result in
inadequate shear connection between the profiled
sheeting deck and the hardened concrete. This is
primarily due to the fact that ultimate load associated
with shear bond loss between the steel sheeting and
concrete is low [9].
The shear bond analysis for PDCS with the use of
shear bond equations requires the experimental failure
test load (FTL) values. For example, under
slope-intercept (m-k) method, the application of
regression analysis on the test results, leads in
obtaining the shear strength parameters. It is evident
that the experimental failure test is essential in
determining the requisite shear parameters. The
process is cumbersome and costly. However, the
volumes of research findings and proposals on the
complex shear characteristics of profiled deck
composite slab, the laboratory performance testing
Composite Slab Numerical Strength Test Method Under M-K Approach
42
International Journal of Mechanical And Production Engineering, ISSN: 2320-2092,
Volume- 4, Issue-9, Sep.-2016
stands to be the only accurate means for the
determination of composite slab strength. The issue is
critical and warrant much further thoughts from
different perspective other than the deterministic
approach that are costlier and time consuming [10].
A. The m-k method
The m and k parameters are deduced from the linear
relationship plots of vertical shear, V t bd p against
That limitation has led to many research development
through the use of numerical solutions all with the aim
of eliminating the uneconomical full scale test that is
required to verified the performance of composite slab
[2, 6]. Therefore, the development of a rational based
numerical test load function from longitudinal shear
capacity consideration is a necessity in augmenting the
previous futile attempts for strength determination of
PDCS devoid of the costlier and expensive laboratory
procedure. This paper presents the viability of a
simplified numerical function in determining the
strength capacity of PDCS. This can be achieve
through evaluating the safety performance of PDCS
based on longitudinal shear capacity, and by
establishing the deck properties in defining its
capacity in relation to the performance function. The
study validates the performance of the developed
numerical load function estimation with experimental
procedure.
capacity test values of long,
shear bond, Ap bls for two groups of experimental
x and short, y as
depicted in Fig. 2. The parameter A p is the sheeting
deck effective cross-sectional area with yield strength,
fy p and d p is the clear distance from the centroid-al
distance of the profile sheeting to the topmost face of
the concrete. For ductile failure condition, the support
reaction, Vt  w / 2 .
Fig. 2 Shear parameters determination method
The design shear resistance V i ,R d
expression given in Eq.(2).
V i, Rd =
bd p
1.25
[m (
Ap
bls
is by the
) + k ] (2)
B. The performance function
This study performance function for the determination
of the safety index,  using first order reliability
method is on the material load carrying capacity and
the design load estimation from the shear resistance of
composite slab as given by Eq.(3).
Fig. 1. PDCS failure positions
II. SAFETY PERFORMANCE ANALYSIS
The safety consideration analysis in this paper is by
the use of reliability concept application in
determining the failure probability, p f . This value
indicates the chance that a particular point the
difference between the resistances offered by the
material, R in relation to the applied load, Q will
result in a value whether it’s within the acceptable
range or otherwise, and the mathematical expression is
shown in Eq.(1).
Qm -
2V i,R d
L
= R - Q (3)
Where the mean resistance, Qm = Qn (M n Fn Pn ) .
The parameter Qn is the nominal resistance value
having a bias factor of 1.0. The variables M n , Fn ,
p f = prob (R - Q < 0 ) = p (k < 0 ) (1)
Pn are factors for material fabrication, fabrication
factor for geometry and dimension of the component,
and professional factor for approximation in structural
analysis, respectively. Similarly, those factors mean
resistance
coefficient
of
variation,
where k is the limit state function (LSF) that defines
the desired boundary; condition from the un-desired
boundary condition, k < 0 . This study performance
function is based on the load capacity estimation from
the use of longitudinal shear using m-k method, and
experimental test load.
VQ =
(vm2 v f2v p2 ) . The parameters, vm , v f and
v p are corresponding coefficient of variation, cov for
Composite Slab Numerical Strength Test Method Under M-K Approach
43
International Journal of Mechanical And Production Engineering, ISSN: 2320-2092,
Volume- 4, Issue-9, Sep.-2016
the factors M n , Fn , and Pn respectively. The study
adopted values for the mean cov for those factors are
1.10, 0.1; 1.0, 0.05 and 1.11, 0.09, with all having
normal distributions accordingly [3]. Similarly, on the
basis of Ellingwood and Galambos [11], the cov value
and distribution type for the parameters b and ls are
0.17 and log-normal distribution, and each has a bias
factor of 1.0.
Furthermore, in determining the nominal resistance
value, this study uses external experimental test
results. The detailed test specimens properties and
their laboratories performance can be found in
Marimuthu, et al. [2] and Hedaoo, et al. [12].
Fig. 4. Relationship between  and design load
Hence, the numerical FTL function for the strength
determination of PDCS is
C. Numerical failure load function
Assuming, the load ratio, lr function defines the ratio
FT L = 0.001zdl flr l (4)
 dl . The
establishment of best-fit relation between the lr
function and the  value estimation is highly
of experimental FTL over the design load,
The following section in this paper gives the
experimental works in validation of the computation
using the expression given in Eq.(4) that computes the
numerical FTL value devoid of experimental test
procedure.
essential in fulfilling the study goal, and Fig. 3 shows
that.
III. EXPERIMENTAL TEST SET-UP
The experimental test scope considered in this study
comprises the testing of PDCS at the University of
Putra Malaysia. A total of eight specimens consisting
two each for both long and short shear span lengths of
228 mm, 243 mm, and 305 mm, 320 mm, respectively.
For simplicity, these specimens are identified using
notations SS and LS; for example, SS-228 and LS-305
represents short and long specimen with shear span
length of 228 mm and 305 mm, respectively.
D. Materials properties and concreting
The metal deck has a thickness of about 0.47 mm, and
its 1829 mm long (L), having width (b) value of 820
mm as shown in Fig. 5. The desired concrete strength
is normal grade concrete, and the mix is prepared
using 20 mm aggregate for 120 mm thick concrete. For
hydration control, 5.2 mm mild bars are mesh through
at 220 mm both ways, and placed 20 mm above the
metal deck. Similarly, the fabrication of the concrete
form is with the use of plywood, and the concreting
works under supportive laboratory condition.
Fig. 3 The safety performance in relation with lr
In Fig. 3, the average lr between the upper and lower
point is 1.44, and this is considered as load ratio factor,
flr . The evaluation of these points comes from the
determination of the failure test load and their
equivalent  dl estimation from longitudinal shear
while grouping the section into compact ( l / 8 ) and
slender section ( l / 6 ). Moreover, the decking
characteristic   Ap f yp d p / ls is useful in
expressing the estimation of the
in Fig. 4.
 dl value as depicted
Composite Slab Numerical Strength Test Method Under M-K Approach
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International Journal of Mechanical And Production Engineering, ISSN: 2320-2092,
Volume- 4, Issue-9, Sep.-2016
Fig. 7 LVDT arrangements
The experimental test results will validate the
numerical solution estimation for the strength capacity
determination of PDCS. The closeness between the
compared results will validate the suitability of the
developed model for strength capacity estimation of
PDCS. The mechanical hydraulic jack aided in
applying the test load and data logger-TDS-530
records the hysteresis behavior. Moreover, the final
end-slip value between the decking sheet and the
concrete is from the average difference between the
two edges LVDT results.
Fig. 5 Test specimen profile
The necessary laboratory checks on the mix design
prior to concreting are fully adhered to according to
the ACI-318 standard, and the mix design found to be
workable as it is within the acceptable code's limit.
Moreover, cubes for the determination of the
compressive strength from the batch mixes for testing
after 28 days of proper curing shows an average
compressive strength of 28.5 MPa. Similarly, the
prepared test specimens was carried to the testing site
from the yard with the aid of proper support; bearing
in mind the consequences of transferring any flexural
load to the slab while in transit will be disastrous.
E. Experimental test set-up
The load is applied with the used of two spreader roller
weighing about 10 kg each which are placed on top of
the slab specimen with the intention of applying the
two point load from cross beam that also weigh about
70 kg. The overhang length lo is 100 mm from both
IV. RESULTS AND DISCUSSION
Fig. 8 shows the experimental performance of the
tested slab specimens under four different shear span
lengths, depicting also the maximum FTL sustained
under each respective shear span length for the PDCS.
Importantly, only one out of the test specimens
exhibits brittle failure mode. This type of failure mode
is when the slip value between the decking sheet and
the concrete is more than 0.3 mm.
ends. In determining the slab failure mode during the
test procedure, linear variable displacement
transducers (LVDT) were at the edges of the decking
sheet and the concrete as depicted in Fig. 6. Similar
LVDT is also at the mid-span to measure the slab
deflection (Fig. 7). The data logger-TDS-530 records
the values of the end-slip, the mid-span deflection
including the test load. The testing is halted when the
maximum applied load drops by about 20%, or the
mid-span deflection value is approaching l 30 as
adopted by [13].
Fig. 8 Force-deflection behaviour under different shear span
lengths
Table 1. Experimental and approximate failure test load
comparisons
Fig. 6 Specimen experimental test set-up
Table 1 shows the results for the experimental and the
approximate estimation for the PDCS. Previous
Composite Slab Numerical Strength Test Method Under M-K Approach
45
International Journal of Mechanical And Production Engineering, ISSN: 2320-2092,
section had the detailed descriptions of the slab
properties. Moreover, in Table 1, the approximate
estimation is from the use of Eq.(4). The statistical
p-value concept is sort in determining the closeness
between the FTL values. Evidently, the result shows
no significant difference between the FTL results (
t  0.169, dof  6, p  0.05 ). This result
indicates that the numerical FTL determination
function devoid of the costly experimental procedure
will be effectively useful especially in appraising
manufacturer supplied test data on decking sheet.
[3]
[4]
[5]
[6]
CONCLUSION
This paper presented a rational based study on load
carrying capacity of profiled deck composite slab
design provision under longitudinal shear capacity
using slope-intercept method. The study yields to the
formation of numerical load determination function
for PDCS and validation through experimental test.
The litmus test comparisons of load capacity with the
experimental test result shows good prospect of the
numerical model in determining the strength capacity
of PDCS under the slope-intercept method.
[7]
[8]
[9]
ACKNOWLEDGEMENT
[10]
The authors will like to thank the Universiti Putra
Malaysia for providing full financial support
(GP-IPS/2015/9453400) required for this work.
[11]
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