Please wait a minute...

Frontiers of Structural and Civil Engineering

Front. Struct. Civ. Eng.    2017, Vol. 11 Issue (4) : 412-423     https://doi.org/10.1007/s11709-017-0416-8
Research Article
Instantaneous deflection of light-weight concrete slabs
Behnam VAKHSHOURI(), Shami NEJADI
Centre for Built Infrastructure Research (CBIR), University of Technology Sydney (UTS), P.O. Box 123, Sydney, Australia
Download: PDF(758 KB)   HTML
Export: BibTeX | EndNote | Reference Manager | ProCite | RefWorks
Abstract

Construction loading before the age of 28 d can have the most significant effects on the slabs, especially for multi-story structures. The changing properties of the young concrete complicate the prediction of serviceability design requirements also. An experimental investigation is performed on four simply supported Light-Weight Concrete (LWC) one-way slabs subjected to immediate loading at 14 d. Effects of aggregate type, loading levels and cracking moment together with the influences of ultimate moment capacity and service moment on the instantaneous deflection of slabs are studied. Comparison of the obtained results with predictions of existing models in the literature shows considerable differences between the recorded and estimated instantaneous deflection of LWC slabs. Based on sensitivity analysis of the effective parameters, a new equation is proposed and verified to predict the instantaneous deflection of LWC slabs subjected to loading at the age of 14 d.

Keywords instantaneous deflection      light-weight concrete      expanded polystyrene      effective moment of inertia      cracking moment      moment capacity      service moment     
Corresponding Author(s): Behnam VAKHSHOURI   
Online First Date: 16 June 2017    Issue Date: 10 November 2017
 Cite this article:   
Behnam VAKHSHOURI,Shami NEJADI. Instantaneous deflection of light-weight concrete slabs[J]. Front. Struct. Civ. Eng., 2017, 11(4): 412-423.
 URL:  
http://journal.hep.com.cn/fsce/EN/10.1007/s11709-017-0416-8
http://journal.hep.com.cn/fsce/EN/Y2017/V11/I4/412
Service
E-mail this article
E-mail Alert
RSS
Articles by authors
Behnam VAKHSHOURI
Shami NEJADI
Fig.1  Deformation response of idealized reinforced concrete beam at critical section
Fig.2  EPS beads in fresh and hardened LWC
referenceequationEq.applicationexpression
[13]Im=23IcrIe8Icr+15Ie(1)FRP beamIm: average I
Ie from ACI-318-87
[15]Ie=(McrMa)3βdIg+[1(McrMa)3]×Icrγγ=(0.0017ρρb+0.8541)(Ef2Es+1)(2)FRP beamEs : steel
Ef : fiber
ρ: tensile steel ratio
[16]Ie=[1.4215(McrMa)]IcrIg:1McrMa<3(3)FRP beam
[17]Ie=IcrIgIcr+[1β1β2(McrMa)2](IcrIg)Ig(4)CC beamβ1 : 0; 1smooth; ribbed bar
β2 : 0;1sustained; first load
[18]Ie=Icr+[(IgIcr)ρMcrMa×LcrL]IgIe=Icr+[(IgIcr)McrMa×LcrL]Ig(5)
(6)
FRP , CCLcr : cracked length
L : member length
ρ: tensile steel ratio
[19]Ie=(McrMa)3Ig7+0.84[1(McrMa)3]IcrIg(7)FRP beam
[20]Ie=(McrMa)2Ig+[1(McrMa)2]IcrIgIe=(McrMa)3Ig+[1(McrMa)3]IcrIg
Ie=(McrMa)4Ig+[1(McrMa)4]IcrIg
(8)
(9)
(10)
CC beampower in equation
2 : Initially expected
3 : Average behavior
4 : Section behavior
[28]Ie=Icr1ηβ(McrMa)Ig
η=1Icr/Ig
(11)CC beamβ : 1; 0 for complete and no tension stiffening
[29]Ie=Icr+(IgIcr)(McrMa)30.8ρIg(12)Point loadρ: tensile steel ratio
[3032]Ie=(McrMa)3Ig+(1(McrMa)3)IcrIg(13)CCIe≤0:6Ig in AS-3600(09)
[33]Ie'=Icr1γηβ(McrMa)Ig(14)Equivalent Iesimply supported beam
UDL
[34,35]Ie=Icr1η(McrMa)2Ig
η=1Icr/Ig
(15)CCoriginally for axial tension
[14,31]Ie=(McrMa)3βdIg+[1(McrMa)3]×IcrIgβd=ab(Ef/Es+1),ab=0.2ρ/ρb1(16)FRP bar in tensionEf ; Es
elasticity of
FRP bar and steel
[36]Ie=Icr?IgIcr+[10.5(McrMa)2](IcrIg)Ig(17)FRP beam
[37]Ae=PcrP3Ag+[1(PcrP)3]AcrAg(18)Direct tensionanalogous approach
for Ie in ACI-318
Tab.1  Existing models of effective moment of inertia (Ie) in literature
sieve sizepassing (%)
pepper-threewashed Kurnell
4.75 mm100
2.36 mm80
1.18 mm55100
600 µ m3799
300 µ m2358
150 µ m112
≤75 µ m (%)5Nil
uncompacted bulk density (t/m3)1.691.33
compacted bulk density (t/m3)1.861.47
particle dry density (t/m3)2.692.52
particle density (SSD) 1)(t/m3)2.712.55
apparent particle density (t/m3)2.762.59
water absorption (%)0.91.0
pH value of soil8.8
degradation factor of aggregate85
the wash water after using permitted 500 mlClear
method of determining void content (% voids)40.7
silt content (%)3
Tab.2  Properties of fine and coarse sand types
sieve sizepassing (%)
13.2 mm100
9.5 mm88
6.7 mm53
4.75 mm20
2.36 mm4
1.18 mm2
misshapen particles (%)
ratio 2:123
ratio 3:16
uncompacted bulk density (t/m3)1.33
compacted bulk density (t/m3)1.5
moisture of the aggregate (%)3.0
particle dry density (t/m3)2.63
particle density (SSD) 1)(t/m3)2.66
apparent particle density (t/m3)2.76
water absorption (%)1.9
ave. dry strength (kN)366
ave. wet strength (kN)246
strength variation (wet/dry) (%)33
test fraction (mm)–9.5+6.7
amount of significant breakdown (%)<0.2
abrasion resistance (%)15
Tab.3  Properties of crushed Dunmore latite
chemical componentsphysical propertiesmechanical properties
CaO (%)62.6fineness (m2 /kg)395initial setting time (min)105
SiO2 (%)19.26autoclave Expansion (%)27.7final setting time (min)150
Al2O3 (%)5.15residue (45 µm )2.3drying shrinkage-28 d (µε)570
Fe2O3 (%)3.08fc − 3 d (MPa)34
MgO (%)1.14fc − 7 d (MPa)45.6
K2O (%)0.53fc − 28 d (MPa)61.1
Na2O (%)0.08Soundness (mm)1
LOI (%)4.1
SO3 (%)3.1
Tab.4  Properties of SL cement
componentproportion
cement (kg/m3)500
water (liter)180
water to cement ratio0.36
BST aggregate (Liter) (vol. %)300 (23%)
fine aggregate (kg/m3)
coarse sand310
fine sand310
coarse aggregate (kg/m3)800
WRA (liter)2
Tab.5  Mixture proportions of the EPS-LWC (Based on SSD condition)
Fig.3  Bar arrangement, cover details and dimension of slab specimens. cs= 40 mm, cb= 25 mm, s = 106 mm 4N12 bars in the section
Fig.4  Loading blocks and LVDT positioning for flexural test of LWC slabs
Fig.5  Development of compressive strength and modulus of elasticity with age
slabWa (kN/m)Mu (kN/m)Ma(kN/m)Ma/ Mu (%)Δe (mm)
14 d28 d14 d28 d14 d28 d
LWC−17.027.427.6510.7239.1338.784.994.57
LWC−27.027.427.6510.7239.1338.784.994.57
LWC−35.2927.427.658.09529.5529.293.773.45
LWC−45.2927.427.658.09529.5529.283.773.45
Tab.6  Loading values, moment ratios and elastic deflection of slabs
Fig.6  Ratio of recorded deflection to estimated elastic deflection at two ages
Fig.7  (Dins/De) 14 under different ratios of service and ultimate moments
Fig.8  Growing rate of Dins−14 due to 10 % increment of Ma/Mu
Fig.9  Effect of moment ratios on (Dins/De) 14
Fig.10  Predictions of existing models for Dins−14 and recorded data
coefficientβρMcr/MaIe
limitEc−14/ Ec−28≥0.005≤3≤0.6Ig
Tab.7  Coefficients and limitations of proposed model for Ie in LWC slabs
Fig.11  Comparison of the recorded and predicted deflection of slabs at 14 d by proposed model
1 Mazzotti C, Savoia M. Long-term deflection of reinforced self-consolidating concrete beams. ACI Structural Journal, 2009, 106(06): 772–781
2 Yoğurtcu E, Ramyar K. Self-compacting lightweight aggregate concrete: Design and experimental study. Magazine of Concrete Research, 2009, 61(7): 519–527
https://doi.org/10.1680/macr.2008.00024
3 Güneyisi E, Gesoğlu M, Booya E. Fresh properties of self-compacting cold bonded fly ash lightweight aggregate concrete with different mineral admixtures. Materials and Structures, 2012, 45(12): 1849–1859
https://doi.org/ 10.1617/s11527-012-9874-6
4 Mazaheripour H, Ghanbarpour S, Mirmoradi S H, Hosseinpour I. The effect of polypropylene fibers on the properties of fresh and hardened lightweight self-compacting concrete. Construction & Building Materials, 2011, 25(1): 351–358
https://doi.org/10.1016/j.conbuildmat.2010.06.018
5 Vakhshouri B, Nejadi S. Mix design of light-weight self-compacting concrete. Case Studies in Construction Materials, 2016, 4: 1–14
https://doi.org/10.1016/j.cscm.2015.10.002
6 Xu Y, Jiang L, Xu J, Li Y. Mechanical properties of expanded polystyrene lightweight aggregate concrete and brick. Construction & Building Materials, 2012, 27(1): 32–38
https://doi.org/10.1016/j.conbuildmat.2011.08.030
7 Trussoni M, Hays C D, Zollo R F. Fracture properties of concrete containing expanded polystyrene aggregate replacement. ACI Materials Journal, 2013, 110(5): 549–557
8 Sabaa B, Ravindrarajah R S. Engineering properties of lightweight concrete containing crushed expanded polystyrene waste. In: Materials Research Society, 1997, Fall Meeting, Symposium MM, Advances in Materials for Cementitious Composites. 1997
9 Scanlon A, Bischoff P H. Shrinkage restraint and loading history effects on deflections of flexural members. ACI Structural Journal, 2008, 105(4): 498
10 Vakhshouri B. Time-dependent bond transfer length under pure tension in one way slabs. Structural Engineering and Mechanics, 2016, 60(2): 301–312
https://doi.org/10.12989/sem.2016.60.2.301
11 Li Y, Liu N, Chen B. Properties of lightweight concrete composed of magnesia phosphate cement and expanded polystyrene aggregates. Materials and Structures, 2015, 48(1-2): 269–276
https://doi.org/10.1617/s11527-013-0182-6
12 Achintha P M, Burgoyne C J. Moment-curvature and strain energy of beams with external fiber-reinforced polymer reinforcement. ACI Structural Journal, 2009, 106(1): 20–29
13 FazaS, Gangarao  H. Pre-and post-cracking deflection behaviour of concrete beams reinforced with fibre-reinforced plastic rebars. In: Proceedings of the First International Conference on Advance Composite Materials in Bridges and Structures (ACMBS-I). Sherbrooke: Canadian Society of Civil Engineers, 1992
14 Yost J R, Gross S P, Dinehart D W. Effective moment of inertia for glass fiber-reinforced polymer-reinforced concrete beams. ACI Structural Journal, 2003, 100(6): 732–739
15 Rafi M M, Nadjai A, Ali F, Talamona D. Aspects of behaviour of CFRP reinforced concrete beams in bending. Construction & Building Materials, 2008, 22(3): 277–285
https://doi.org/10.1016/j.conbuildmat.2006.08.014
16 Alsayed S, Al-Salloum Y, Almusallam T. Performance of glass fiber reinforced plastic bars as a reinforcing material for concrete structures. Composites. Part B, Engineering, 2000, 31(6): 555–567
https://doi.org/10.1016/S1359-8368(99)00049-9
17 Hall T, Ghali A. Long-term deflection prediction of concrete members reinforced with glass fibre reinforced polymer bars. Canadian Journal of Civil Engineering, 2000, 27(5): 890–898
https://doi.org/10.1139/l00-009
18 Fikry A M, Thomas C. Development of a model for the effective moment of inertia of one-way reinforced concrete elements. ACI Structural Journal, 1998, 95(4)
19 Benmokrane B, Chaallal O, Masmoudi R. Flexural response of concrete beams reinforced with FRP reinforcing bars. ACI Structural Journal, 1996, 93(1): 46–55
20 Branson D E. Instantaneous and Time-Dependent Deflections of Simple and Continues Reinforced Concrete Beams. HPR Report, No.7 Part 1. Alabama Highway Department/U.S. Bureau of Public Roads, 1965
21 AS-1012.14, Methods of Testing Concrete—Method for Securing and Testing Cores from Hardened Concrete for Compressive Strength. Standards Australia, 1991
22 ASTM-C39, Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens. American Society of Testing and Materials, 2000
23 AS-1012.17-97, Methods of Testing Concrete—Determination of the Static Chord Modulus of Elasticity and Poisson’s Ratio of Concrete Specimens. Standards Australia, 2014
24 ASTM-C469/C469M-14, Standard Test Method for Static Modulus of Elasticity and Poisson’s Ratio of Concrete in Compression. American Society of Testing and Materials, 2000
25 AS-1141, Methods for Sampling and Testing Aggregates. Standards Australia, 2011
26 T235. R., Aggregate Least Dimension. Roads AND MARITIME SERVICES (RMS) NSW, Australia, 2006
27 T239. R., Aggregate fractured faces. Roads and Maritime Services (RMS) NSW, Australia, 2006
28 Bischoff P H. Deflection calculation of FRP reinforced concrete beams based on modifications to the existing Branson equation. Journal of Composites for Construction, 2007, 11(1): 4–14
https://doi.org/10.1061/(ASCE)1090-0268(2007)11:1(4)
29 Alshaikh A H, Al-Zaid R. Effect of reinforcement ratio on the effective moment of inertia of reinforced concrete beams. ACI Structural Journal, 1993, 90(2): 144–149
30 ACI-318-08. Building Code Requirements for Structural Concrete and Commentary. ACI Committee, American Concrete Institute, International Organization for Standardization, 2008
31 ACI-435, Control of Deflection in Concrete Structures, ACI 435R-95. American Concrete Institute, 2000
32 AS-3600-09, Concrete Structures. Standards Australia, 2009
33 Bischoff P H, Gross S P. Equivalent moment of inertia based on integration of curvature. Journal of Composites for Construction, 2010, 15(3): 263–273
https://doi.org/10.1061/(ASCE)CC.1943-5614.0000164
34 Bischoff P H, Paixao R. Tension stiffening and cracking of concrete reinforced with glass fiber reinforced polymer (GFRP) bars. Canadian Journal of Civil Engineering, 2004, 31(4): 579–588
https://doi.org/10.1139/l04-025
35 CEBFIP-MC90. CEB-FIP Model Code (MC-90).London: Thomas Telford Ltd., 1993
36 Newhook J. Reinforcing Concrete Structures with Fibre Reinforced Polymers. ISIS Canada: Design Manual No.3, The Canadian Network of Centres of excellence on intelligent sensing for innovative structures, 2001
37 ACI-224. Cracking of Concrete Members in Direct Tension. In: ACI Journal Proceedings. Farming Hills: American Concrete Institute, 1986
38 AS-1478.1, Methods for Sampling and Testing Aggregates, Particle Size Distribution-Sieving Method. Standards Australia, 2000
39 AS-3972, General Purpose and Blended ceMents. Standards Australia, 2010
40 AS-2350, Methods of testing Portland and Blended Cements. Standards Australia, 2006
Related articles from Frontiers Journals
[1] Abdussamad ISMAIL. Estimating moment capacity of ferrocement members using self-evolving network[J]. Front. Struct. Civ. Eng., 2019, 13(4): 926-936.
[2] WANG Jingfeng, LI Guoqiang. Bending and rotational behaviour of semi-continuous composite beams[J]. Front. Struct. Civ. Eng., 2008, 2(2): 116-122.
Viewed
Full text


Abstract

Cited

  Shared   
  Discussed