Journal of Constructional Steel Research 130 (2017) 202–221

Contents lists available at ScienceDirect

Journal of Constructional Steel Research

Steel-concrete-steel sandwich composite structures-recent innovations

J.Y. Richard Liew a,b,⁎, Jia-Bao Yan c,d, Zhen-Yu Huang a

a Department of Civil and Environmental Engineering, National University of Singapore, Singaporeb College of Civil Engineering, Nanjing Tech University, Nanjing, Chinac School of Civil Engineering, Tianjin University, Tianjin 300072, Chinad Key Laboratory of Coast Civil Structure Safety of Ministry of Education, Tianjin University, Tianjin 300072, China

⁎ Corresponding author.E-mail address: ceeljy@nus.edu.sg (J.Y.R. Liew).

http://dx.doi.org/10.1016/j.jcsr.2016.12.0070143-974X/© 2016 Elsevier Ltd. All rights reserved.

a b s t r a c t

a r t i c l e i n f o

Article history:Received 22 March 2016Received in revised form 17 November 2016Accepted 10 December 2016Available online 21 December 2016

Steel-concrete-steel (SCS) sandwich structures consisting of two steel face plates infilled with lightweight ce-ment composite material has been developed. This paper reviews the recent innovations of SCS sandwich struc-tures subject to blast, impact, fatigue, and static loads. Novel J-hook connectors, high strength steel plates andnew lightweight cement composite materials have been considered for the development of the SCS sandwichproducts to improve their strength-to-weight performance. Extensive tests have been conducted to investigatethe effectiveness of J-hook connectors to achieve better composite action to resist flexural, shear, impact, blastand fatigue loads. Flat and curved SCS sandwich plates under patch loading are also investigated. The experimen-tal results are essential to understand the structural behaviour of the SCS sandwich structures and to provide datafor the development of analytical models for design implementation. Design equations have been proposed topredict the shear and tensile resistances of J-hook connectors and to determine the flexural, shear, impact,blast and fatigue resistances of SCS sandwich beam. The punching shear resistance of sandwich shells and com-pression resistance of sandwichwalls are also investigated. The accuracy of the design equations are validated bythe test data and finite element analysis results.

© 2016 Elsevier Ltd. All rights reserved.

Keywords:BlastFatigueImpactSandwich composite beamSandwich composite plateSandwich composite walls

1. Introduction

Steel-concrete-steel (SCS) sandwich composite structures consist oftwo steel face plates and a sandwiched concrete core which are bondedtogether by mechanical connectors to form an integral unit to resist ex-ternal loads. In the early days, SCS sandwich structures were developedfor infrastructures and tunnels to resist loading due to accidental impactand vehicular loading. With the recent investigation on their perfor-mance under static impact, fatigue and blast load [1–6], the applicationsof SCS sandwich structures have been extended to offshore decking,protective structures, oil storage containers and ice-resistant walls [7,8]. Steel-concrete-steel sandwich structures have also been proposedfor structural walls in nuclear facilities [9,10].

Different types of SCS sandwich composite structures have been de-veloped by using different bonding techniques at the steel-concrete in-terface. Cohesive materials, such as epoxy, were used in the SCSsandwich composite structures [11]. Compared with the mechanicalshear connectors, brittle bond failure tended to take place at the steel-concrete interface due to the imperfection of the bonding materialwhich would compromise the structural integrity of the SCS sandwichstructure. A double skin structure with overlapped stud connectors tobond the concrete and steel plates was initially proposed for tunnel

liner [12]. However, the bond between the steel plates and concretecore depends greatly on the spacing and the lapped length of the con-nectors. Once the concrete core failed under the action of extremeloads, the steel plates and the concrete core may separate and affectthe structural integrity of the sandwich plate. One novelway to improvethe structural integrity of SCS sandwich structure is to connect the twosteel face plateswith straight steel bar connectors using frictionwelding[13]. However, the installation of the connectors using the friction weldapparatus limits the thickness of SCS sandwich structure within therange of 200 to 700 mm. Angle-section connectors were also proposedfor SCS sandwich constructions in Japan [14]. Owing to the shallow em-bedment of the angle-section connectors, bond failure tended to occurat the service load level unless additional stiffener plates were provided.To develop a slim deck for offshore platforms, J-hook connectors weredeveloped by Liew et al. [1] as shown in Fig. 1(a). Experimental studiesshowed that SCS sandwich structures with J-hook connectors exhibitedexcellent performances under impact, blast, and fatigue loadings [2,3].This type of structure is suitable for applications in shear walls, protec-tive structure, ship hulls of cargo tank, bridge/offshore decks, and ice-re-sistant wall in Arctic offshore platform as shown in Fig. 1(b–e).

To reduce the self-weight of the SCS sandwich structure, lightweightconcrete (LWC) has been proposed by the authors [13]. LWC with dif-ferent strength to weight ratio offers more choices to design SCS sand-wich structures to achieve higher strength-to-weight ratio. LWC witha density of 1450 kg/m3 and compressive strength of 30 MPa has been

Fig. 1. Applications of the SCS sandwich structure.

203J.Y.R. Liew et al. / Journal of Constructional Steel Research 130 (2017) 202–221

Fig. 2. Novel shear connectors for SCS sandwich structure (a) Angle-Steel bar-Angle (ASA); (b) Angle-T channel (AT); (c) Angle-Steel hoop-Angle (AHA); (d) Angle-C channel-Angle(ACA); (e) U connector-Steel bar-U connector (USU); (f) Angle-I beam-Angle (AIA); (g) Angle–Angle (AA); (h) U connector-Steel Cable-U connector (UCU); (i) Root connector (RC);(j) Through bolt connectors; (k) Overlapped headed stud connectors; (l) J-hook connectors.

Fig. 3. Stress-strain curves of the normal mild steel (NMS) and high strength steel (HSS)under different temperatures.

204 J.Y.R. Liew et al. / Journal of Constructional Steel Research 130 (2017) 202–221

used by the authors in their earlierwork [1,3].More recently, a new typeof ultra-lightweight cement composite (ULCC) material with densityranging from 980 to 1450 kg/m3 and compressive strength up to60MPa has been developed [15,16]. The development of lightweight ce-ment composite material has led to further research on sandwich com-posite structures.

In this paper, recent innovations on SCS sandwich structures aresummarized. These innovations include the development of new J-

Table 1Basic material properties of ULCC at age 28-day.

Item Material property ULCC⁎

1 Density after de-mould 1450 kg/m3

2 Compressive strength, cube fcu 64.0 MPa3 Compressive strength cylinder fck 64.6 MPa4 Ratio fck/fcu 1.015 Splitting tensile strength 4.4 MPa6 Flexural strength 6.7 MPa7 Static modulus of elasticity 16 GPa8 Static Poisson's ratio 0.25

ULCC⁎ = Ultra Lightweight Cement Composite.

Fig. 4. Stiffened steel plate and SCS sandwich structure.

205J.Y.R. Liew et al. / Journal of Constructional Steel Research 130 (2017) 202–221

hook connectors and newultra-lightweight cement composite corema-terials for SCS sandwich structures. Experimental and numerical inves-tigations were carried out to determine the resistances of the shearconnectors, SCS sandwich beams and SCS plates and shells. Their im-pact, fatigue, blast and static load performance were also studied. Final-ly, analytical formulae were developed to predict the design resistanceof SCS structures under axial compression, bending moment, shearand punching loads.

2. Novel connectors for steel-concrete-steel sandwich construction

Steel-concrete-steel (SCS) sandwich structures consist of threemajor components: two external steel face plates, concrete or cementcomposite core and connectors. Among them, the connectors act essen-tially on providing longitudinal and transverse shear resistance, and of-fering pull-out resistance to prevent separation between steel platesand concrete core. SCS sandwich structures with different types ofshear connectors have been developed by Yan et al. [6] and Sohel et al.[17] as shown in Fig. 2. These new types of connectors are (a) Angle-Steel bar-Angle (ASA), (b) Angle-T channel (AT), (c) Angle-Steelhoop-Angle (AHA), (d) Angle-C channel-Angle (ACA), (e) U connec-tor-Steel bar-U connector (USU), (f) Angle-I beam-Angle (AIA), (g)Angle–Angle (AA), (h) U connector-Steel Cable-U connector (UCU), (i)Root connector (RC), (j) Through connectors, (k) Overlapped headedstud connectors, and (l) J-hook connectors.

The angle connectors or the ‘U’ shape connectors are welded to theexterior steel plates to provide interface slipping resistance. The

Table 2Comparisons of the SCS sandwich plate with steel plate.

Comparison

Steel plate structure

SCS sandwich plate

Steel consumption 1.0 1.0 0.67

Overall weight 1.0 1.92 0.44

Moment resistance 1.0 12 1.0

Stiffness 1.0 200 1.03

t0.5t

0.5t15t

t/3

t/35/3t

inserted steel bar (used in ‘ASA’ and ‘USU’), steel hoops (used in‘AHA’), C channel (used in ‘ACA’), ‘I’ beam (used in ‘AIA’) and the steelcables (used in ‘UCU’), all serve the same function which is to link thetwo face steel plates preventing them from tensile separation and toprovide bond enhancement between the concrete core and face plates.These connectors have their own merits in terms of ease of installationand ability to withstand extreme loads without the loss of structuralintegrity.

The cable and U-shaped connectors, as shown in Fig. 2(h), requirethe least steel consumption and they are feasible to install in a thinsandwich panel. Here the cable would be threaded through the U-shaped connectors which were pre-welded to the top and bottomsteel plates in an overlapped position. Jacks would then be used tospread the plates into their final position and deform the cables. Con-crete is pumped in between the two plates and the cables would resistthe tensile separation of the two plates during the casting of theconcrete.

Compared with the overlapped headed shear studs that were com-monly used in the steel-concrete composite structure, the double J-hook connectors, as shown in Fig. 2(l), have the advantages of fast in-stallation, low cost, and equivalent structural performances. The mainadvantage of the J-hook over the overlapped headed studs is that thetensile resistance of the overlapped headed studs greatly depends onthe confinement of concrete while the double interlocked J-hook con-nectors could provide certain degree of tensile resistance without theconfinement of concrete. This advantage becomes more apparentwhen significant cracks developed in the concrete core under the actionof extreme loads. Therefore, considering these advantages, the J-hookconnectors were chosen for further research of SCS sandwich platesunder extreme loads.

3. Use of high strength steel and lightweight concrete materials

In steel-concrete-steel sandwich composite structures, the steel andconcrete are the main materials that are used to resist tension and com-pression forces, respectively. Recently, high strength steel (HSS) withyield strength over 700MPawas available for the steel-concrete compos-ite structure [18–21]. Yan et al. [18,19] studied themechanical propertiesof the mild steel and high strength steel under ambient and low temper-atures (−60 °C) for the applications of the SCS sandwich structure in the

Fig. 5. Shear resistance of SCS sandwich section with overlapped headed shear studs.

206 J.Y.R. Liew et al. / Journal of Constructional Steel Research 130 (2017) 202–221

Arctic region. Fig. 3 compares the engineering stress-strain curves of thenormal mild steel and high strength steel under tension. The steelstrengths in terms of proof load and ultimate tensile strength increaseas the temperature is lower from room temperature of 30 °C to −60 °Calthough the percentage of increase is not very significant (b10%).

Different types of concretemixtures such as normal weight concrete(NWC), lightweight concrete (LWC), and ultra-lightweight cementcomposite (ULCC) could be used in the SCS sandwich composite struc-ture. The ULCC was a special type of fiber-reinforced cement compositematerial with a density of 1450 kg/m3 and 28-day compressive strengthof about 60 MPa. Detailed properties and description of such materialswas reported [15,16]. The ULCC has a high specific strength (strengthto density ratio) above 40 compared to 25 kPa/(kg/m3) for normal con-cretewith similar strength. Besides a 40%weight reduction fromnormalconcrete, the ULCC exhibits ultimate tensile and flexural strengths com-parable with normal concrete of similar strength. Due to its porous ma-trix, the ULCC has lower modulus of elasticity which is approximately50% that of normal weight concrete. Table 1 shows thematerial proper-ties of the ULCC at 28-day. Basic components of the ULCCwere ordinaryPortland cement, silica fume, fine aggregate named cenosphere with adiameter of ranging 100 to 300 μm and 6 mm long polyvinyl alcohol(PVA) fiber. Short PVA fibers (0.5% by volume) were used in ULCC to re-duce the shrinkage and drying effect. To improve the workability andperformance of such material, super plasticiser and shrinkage reducingadmixture were added to achieve a desired flow of 210– 240 mm. Suchhigh flow was required so that the cement composite can fill the thinvoid between the two steel plates and flow around the closely spacedshear connectors. Besides the weight saving, the absence of the coarseaggregates leads to a highly workable material suitable for pumpingand grouting in construction.

The mechanical properties of the normal weight concrete, light-weight concrete, and ULCC under ambient and Arctic low temperatures

Fig. 6. Stress block of the sandwi

have been reported by Yan et al. [7]. These mechanical properties maybe used in the analysis of the structural behaviour of the lightweightSCS sandwich structure.

4. Comparisons of SCS sandwich structure with conventional stiff-ened steel plate structure

A stiffened steel plate (SSP) structure, as shown in Fig. 4(a), waswidely used in the offshore deck and ship hulls. Comparedwith the stiff-ened steel plate structure, theproposed steel-concrete-steel (SCS) sand-wich structure could offer the advantages of (1) elimination of the needof secondary beams as shown in Fig. 4(a) and (b), (2) reduction ofwelding and thus improvement of work productivity, (3) reduction ofsteel surface area and thus lowering the cost of corrosion protection,(4) improvement of acoustic and thermal insulation, (5) achieving asimple structural form that includes easy of fabrication, flexible serviceslayout, easy inspection and maintenance, and (6) improvement of thestructural performance against impact, blast, and fatigue loads.

Table 2 illustrates the detailed conceptual comparisons that includesteel consumption, overall weight, moment resistance of the cross sec-tion, and elastic stiffness between the steel plate structure and SCS sand-wich plate. If all the properties for the steel plate structure were taken asunity, i.e., steel consumption, overall weight, moment resistance of thecross section, and elastic stiffness for the steel plate are equal to 1.0, therelative corresponding values for the SCS sandwich plate are given inTable 2. The comparisons show that if the steel consumption in SCSsandwich plate ismaintained the same as that of the steel plate structure,i.e., the total thickness of the steel plate is kept the same as t, the SCS sand-wich structure with concrete core thickness 15t would significantlyincrease the moment resistance and elastic flexural stiffness by 12 and200 times, respectively. Meanwhile, the overall self-weight of the SCSplate is increased by 92% as compared to the steel plate. If the flexural

ch composite beam section.

207J.Y.R. Liew et al. / Journal of Constructional Steel Research 130 (2017) 202–221

resistance and stiffness of the steel plate structure are to be maintained,then an equivalent SCS sandwich structure would require a plate thick-ness of t/3 and core thickness of 5/3twhich reduces the steel consumptionby33%and theoverallweight by 56%. The above comparisons confirm theadvantages of the SCS sandwich structure over the traditional stiffenedsteel structure in terms of structural efficiency.

5. Mechanical connectors for SCS sandwich structure

Mechanical connectors play an important role in the structural per-formance of SCS sandwich structures. The shear and tensile resistancesof the connectors needed to be established. Under flexural loading, theshear forces at the steel-concrete interface will be resisted by the con-nectors which bond the two face plates and the concrete core. Whenthe SCS plate is subjected to transverse shear force, themechanical con-nectors could behave as reinforcement bars to bridge the shear cracks inthe concrete core, and their tensile resistance will contribute to thetransverse shear resistance of the cross section. Moreover, the connec-tors also provide buckling restraint to the steel face plate under com-pression. Therefore, the shear and tensile resistances of themechanical connectors need to be evaluated carefully.

5.1. Shear resistance of connectors

The design shear resistance of the headed shear studs can be calcu-lated by Eurocode 4 [22]:

PH ¼ min 0:29αd2ffiffiffiffiffiffiffiffiffiffiffiffiffif ckEck

q;0:8σuπd

2=4

� �=γv ð1aÞ

whereα=0.2(hs/d+1) for 3≤hs/d≤4,α=1 for hs / d N 4; hs denotes theheight of the headed shear studs; fck is the compressive strength of con-crete cylinder; Eck denotes elastic Young's modulus of the concrete; d isthe connector diameter; γv is the partial factor; σu denotes the ultimatestrength of the connector.

For the J-hook connectors, Yan et al. [23] proposed a formulae to cal-culate shear resistance as the following:

P J ¼ 0:855 f 0:265ck E0:469c Ashcd

� �0:154

=γv≤0:8σuAs=γv ð1bÞ

Fig. 7. Scatter of R ratio for different typ

where As is cross sectional area of connector, in mm2; hc denotes theembedding depth of connector, in mm.

5.2. Tensile resistance of connectors

The tensile resistance for the mechanical connectors is governed bythe smallest value of concrete breakout resistance TCB, concrete pulloutresistance Tpl, tensile fracture resistance of connector bar Ts andpunching shear resistance of the steel plate Tps [5,24].

For an SCS sandwichwith overlapped headed shear stud (see Fig. 5),the tensile resistance can be determined by [5,24]

Ths ¼ min

TCB ¼ 0:333ffiffiffiffiffiffiffif ck

qπh2s 1þ d=hsð Þ=γc

Tpl ¼ 8Abrg f ck=γcTs ¼ Asσu=γM2

Tps ¼ πdt f ys=ffiffiffi3

p� �=γM0

8>>>><>>>>:

ð2Þ

where hs is height of the connector; Abrg is the bearing area of the headof stud; γM2 is partial factor for cross-section in tension to fracture [25];γM0 is partial factor for resistance of cross-section [25].

For SCS sandwich structure with J-hook connectors, the pullout re-sistance in Eq. (2) needs to be modified as the following [24]

Tpl ¼ 1:26f ckehdþ 0:116f yd2 ð3Þ

where eh denotes the distance from the inner shaft of a J-hook to theouter tip of the J-, and 3d b eh b 4.5d.

5.3. Resistance of connector under combined shear and tension

Yan et al. [26] proposed the following formulae to predict the resis-tance of the J-hook under combined shear and tension based on calibra-tion with numerical and test results:

(a) If applied shear force P≤0.2Pu, full tension resistance can bedeveloped:

P≤Pu ð4aÞ

es of sandwich composite beams.

Fig. 8. Fatigue test set-up, fatigue loading scheme and failure modes of SCS sandwich beams.

208 J.Y.R. Liew et al. / Journal of Constructional Steel Research 130 (2017) 202–221

(b) If applied tensile force T≤0.2ϕTu, full shear resistance can bedeveloped:

T ≤Tu ð4bÞ

(c) If VN0.2ϕVu and NN0.2ϕNu, then the following interaction for-mula may be used:

P=Puð Þ þ T=Tuð Þ≤1:2 ð4cÞ

where P denotes the design shear force; Pu is the design shear resistancefrom Eqs. (1a) and (1b); T denotes the design tension force, Tu is the de-sign tension resistance of the connector from Eq. (2).

6. Flexural and shear behaviour

Three- or four-point bending tests on SCS sandwich beams havebeen carried out to investigate their structural performances underflex-ural and transverse shear forces by Liew and Sohel [1], and Yan et al. [5,6]. Finite element analysis offers a useful means to investigate the struc-tural behaviours of the steel-concrete composite structures comparedto experimental studies which are often expensive to perform [27–29]. Numerical studies on SCS sandwich beams have been reported by

Fig. 9. Comparison of S–N curves with current codes.

209J.Y.R. Liew et al. / Journal of Constructional Steel Research 130 (2017) 202–221

Yan et al. [28–29]. Based on these experimental and numerical studies,the design equations have been developed to predict the flexural andshear resistance of the SCS sandwich beams that are summarized herein[5,6].

6.1. Flexural resistance

Several assumptionsweremade for the calculation of theflexural re-sistance of the SCS sandwich composite beams as the following: (1)plane section remains plane; (2) contribution of tensile strength of con-crete is ignored; (3) full plastic rectangular stress block can be devel-oped in the concrete [5,6]. Based on plastic analysis of the crosssection, the plastic stress blocks acting on a SCS section are shown inFig. 6 [5].

The compressive strength of the concrete can be calculated as [30]

Ncc ¼ η f ckλxB=γc ð5Þ

where B is the width of the beam; x is the depth of the neutral axis po-sition. λ= 0.8 for fck ≤ 50 MPa, λ=0.8− (fck − 50) / 400 for 50 b fck ≤

Fig. 10. (a) Drop weight impact test machine (b) te

90MPa; η=1.0 for fck ≤ 50MPa; η=1.0− (fck− 50) / 200 for 50 b fck ≤90 MPa; γc is the partial factor for concrete.

The maximum force developed in the steel plate is governed by ei-ther the yield resistance of the steel plate or the shear resistance ofthe connectors in the compressive or tension zone of the concrete, i.e.

Ncs ¼ min ncPs; f yscAsc=γM0

� �ð6Þ

where nc is the number of the shear connectors in the compressivezone; Ps is the shear resistance of the connectors calculated by Eqs.(1a) and (1b); fysc and Asc are yield strength and area of the steel platein compression, respectively; γM0 is the partial factor.

Following the same principle, the tension force in the tension steelplate could also be calculated by

Nts ¼ min ntPs; f ystAst=γM0

� �ð7Þ

where nt is the number of the shear connectors attached to the tensionsteel plate; fyst and Ast are yield strength and area of the steel plate undertension, respectively.

Based on the equilibrium of tension and compression force acting onthe section, the depth of compression zone of concrete can be calculatedby

Ncc þ Ncs ¼ Nts ð8aÞ

x ¼ Nts−Ncsð Þη f ckBλx=γc

ð8bÞ

The plastic moment resistance is obtained by takingmoments aboutthe center of the compression steel plate as

Mrd ¼ Nts hc þ tc=2þ ts=2ð Þ þ Ncc λx=2ð Þ ð9aÞ

When the top and bottom steel plates are of equal thickness andstrength i.e. tc = tt, the moment capacity of the section is reachedwhen the neutral axis moves near the lower surface of the compression

st specimen (inter-locking J-hook connectors.

Fig. 11. (a) Damage observed on the SCS sandwich plate due to drop weight. (b) Local indentations observed on the top steel plate.

210 J.Y.R. Liew et al. / Journal of Constructional Steel Research 130 (2017) 202–221

steel plate (i.e., x≈0) until the top steel plate is yielded. Therefore, theplastic moment resistance of the sandwich section may be obtainedfrom Eqs. (7)–(9a) as

Mrd ¼ Nts hc þ tc=2þ ts=2ð Þ ð9bÞ

6.2. Transverse shear resistance

Transverse shear resistance of the SCS sandwich composite beamconsists of contributions from the concrete core and shear resistanceprovided by the connectors as shown in Fig. 5 [5,6]:

V rd ¼ Vc þ V s ð10Þ

Fig. 12. Impact force distribution in sandwich slab.

whereVc is the shear resistance of concrete andVs is the shear resistanceprovided by mechanical connectors. Vc can be calculated as [30]

Vc ¼ CRdkη1 100ρ1 f ckð Þ1=3h i

Bhe ð11Þ

where CRd equals 0.18/γc for normal weight concrete and equals 0.15/γc

for lightweight concrete; k ¼ 1þffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi200=hc

p≤2:0 and hc is height of con-

crete core in mm; η1=0.40+0.60u/2200 is the tensile strength reduc-tion coefficient, and u is density of the lightweight concrete in kg/m3;ρ1= ts/[hc+(ts+ tc)/2]≤0.02; tc is the thickness of the steel plateunder compression; ts is the thickness of the steel plate under tension;B is the width of the beam; he is the effective height of the beam.

Considering the thickness of the steel plate, the effective depth of theSCS beam needs to be modified as [5,6]

he ¼ hc þ tcEs=Ec ð12Þ

where, hc is the height of the concrete core; tc is the thickness of thecompression steel face plate; Es is the elastic Young's modulus of steelface plate; Ec is the elastic secant modulus of concrete.

The shear resistance provided by the presence of headed stud con-nectors is calculated by:

V s ¼ n0T ð13Þ

where T = Ths is the tensile resistance of a pair of overlapped headedstuds embedded in concrete core by Eq. (2).

Fig. 13. Configurations and notations of the specimens in the blast tests. (a) Steel-concrete-steel (4mm–70mm–4mm) sandwich plate with 10mm J-hook connectors. (b) Stiffened plateconsisting of 4 mm face plates with 3 mm internal stiffeners.

211J.Y.R. Liew et al. / Journal of Constructional Steel Research 130 (2017) 202–221

6.3. Resistance under combined bending moment and shear force

The design equation proposed by Roberts et al. [31] may be used tocheck the strength of SCS beam section subjected to combined actionof bending and shear:

VV rd

� �2

þ MMrd

� �2

¼ R2≤1 ð14Þ

where Vrd and Mrd are the shear and bending resistances of the beamsection, respectively; V andM are the shear force and bending momentacted on thebeamsection;R is the index of the strengthwhich is used tocheck the load capacity of the sandwich composite beam.

Fig. 14. Blast tests with 5 kg TNT charge at 5 m: specimen SP

The critical sections of the SCS sandwich composite beam can bejudged from the bending moment and shear distribution diagram.

6.4. Validation

There exist 78 tests on SCS sandwich beams with different types ofconnectors, which were reported by Yan et al. [5,6], Roberts et al. [31],Oduyemi andWright [32], Foundoukos [33], and McKinley and Boswell[34], and these were used to check that accuracy of the proposedmodels. The R ratios which are computed for the test specimens fromEq. (14) are plotted in Fig. 7. R greater than one indicates that the pre-dicted strength of the SCS sandwich specimen which were governedby the failure of the connectors are higher than the maximum strength

(on the left) and Specimen SCS (on the right) after blast.

Fig. 15. SCS Panels subjected to blast loads. (a) Deformedmodes SCS panelswith high strength concrete (HSC), normal strength concrete (NSC) and lightweight concrete (LWC). (b) Mid-span displacement-time history of SCS panels with different core materials.

212 J.Y.R. Liew et al. / Journal of Constructional Steel Research 130 (2017) 202–221

obtained from the tests. Fig. 7 shows that the average R ratio for 78beam tests is 1.29 with a coefficient of variation (COV) of 0.16. The pro-posed equations give conservative and reasonable predictions on the ul-timate strength of the SCS sandwich beam structure.

7. Fatigue behaviour

Dai and Liew [3] performed tests on eight SCS sandwich beams withpartial composite connection subjected to fatigue loads. The test speci-mens consisted offiber-reinforced lightweight concrete core (density=1450 kg/m3) sandwiched in between two face plates which wereinterlocked by J-hook connectors that were capable of providing com-posite action between the steel plates and the concrete core.

Fig. 8 shows the test set-up, loading scheme and failuremodes of SCSsandwich beams subjected to fatigue loading.

The failure mode of the test specimens was due to fatigue failure ofthe steel concrete interface bond which was controlled by the numberof shear connectors. The fatigue test results showed that the SCS sand-wich beam with J-hook connectors were capable of interlocking theface plates providing composite action between steel and concrete

Fig. 16. Comparisons of structural response between flat and curved SC

when it was subjected to transverse load fluctuating within an appliedload range ΔP, as shown in Fig. 8.

The fatigue life of the SCS sandwich structure was affected by boththe fatigue load range ΔP and maximum applied load Pmax. Both themaximum applied stress and stress range affected the fatigue behaviourof the SCS sandwich system as reflected by the permanent deformation,hysteretic response, stiffness and energy absorption capacity. Fatiguelife reduces when the load range ΔP or maximum applied load Pmax

increases.Based on these experimental observations, a three-parameter fa-

tigue design equation is proposed based on calibration with test dataas follow:

log10 N fð Þ ¼ 5:09−4:33� log10Δττu

� �þ 3:00� log10 1−

Δττu

� �ð15Þ

where Nf is the fatigue life, i.e. the number of cycles to failure; Δτ is theshear stress range; τu is the shear strength of the connector.

Fig. 9 shows the comparison of S-N curves obtained from the pro-posed equation (Eq. (15)), BS5400, EC4, Bi-steel S-N curve, JSSC andAASHTO approaches. The results show that the fatigue life predicted

S sandwich structure subjected to 1000 kg TNT blast load at 10 m.

Fig. 17. Typical specimen for curved SCS sandwich panel.

213J.Y.R. Liew et al. / Journal of Constructional Steel Research 130 (2017) 202–221

by Eq. (15) for the J-hook connectors is as good as if not better thanthose of conventional headed stud connectors predicted by variouscodes. The fatigue shear strength of mechanical connectors at 1 × 106

load cycles is in the range of 100 ± 20 N/mm2. Based on the sameshear stress amplitude (Δτ) a less conservative fatigue life (Nf) may beobtained from the proposed design equation.

The proposed SCS sandwich system with lightweight concrete coreand J-hook connectors shows good performance under fatigue loadingmaking it attractive for offshore and marine applications in which slimdesign and lightweight are of prime concerns.

8. Impact behaviour

The impact behaviour of the non-composite and full-composite SCSsandwich beams has been studied experimentally by Liew et al. [4] andRemennikov et al. [35]. Sohel and Liew [36] investigated the impact be-haviour by carrying out 8 tests on SCS sandwich plates measuring1200 × 1200mm2 (width × length) with varying parameters includingdifferent core thicknesses (80 and 100 mm) and face plate thicknesses(4, 6 and 8 mm). Special lightweight concrete of density 1450 kg/m3

and interlocking J-hook connectors have been developed for this pur-pose. The impact testswere conducted by an instrumented drop-weightimpact testmachine as shown in Fig. 10. A photodiode system, compris-ing two laser emitters and two photodiodes, was used to capture the in-cident velocity of the projectile. Both the projectile and the specimenwere instrumented in order to capture the impact force and the re-sponse of the specimen. Local punching is the dominant failure modedue to low velocity impact by a large mass on the SCS sandwich plate(see Fig. 11a). When the projectile struck the slab, very high stresswas developed at the point of impact. The high impact stress wouldcause local indentation on the face plate and crush the concrete core

Fig. 18. Shear failure of the cu

below the impact (see Fig. 11b). The impact stress waves travelledfrom the impact point to the edge supports and induced shear cracksin the concrete core. The slab gained momentum as the projectile trav-elled downward causing downward displacements which further in-duced more damage in the concrete core due to the formation offlexural cracks. The bottom steel plate experienced impact shock wavefrom the top and tended to move downward and separated from con-crete core as shown in Fig. 12. The separation of the bottom platecould be prevented by the interlocking J-hook connectors which con-nected both the top and bottom steel plates. An addition of 1% steel fi-bers in the concrete core showed some beneficial effects in reducingthe cracks and spalling of concrete core, which helped to reduce theoverall deflection of the slab due to impact.

An elastic-plastic model was proposed to predict the force-indenta-tion relationship of SCS sandwich slab subject to central impact force.Using the proposed force-indentation relations, an energy balancemodel was adopted to analyse the global behaviour and energy absorp-tion capacity of SCS sandwich slabs. For a given impact energy and slabconfiguration, the central deflection of the SCS sandwich slab can be de-termined with reasonable accuracy using this energy balance model.The maximum central deflection is an important index for evaluatingthe damage levels of the SCS sandwich slabs subject to impact load pro-vided the failurewas not due to the projectile punching through the topplate.

9. Sandwich panels subject to blast load

An experimental programme was carried out to investigate the re-sistance of SCS sandwich panels subjected to blast loads. A total of sixspecimens were fabricated for three blast tests. Two specimens weretested in each blast load. The configuration and notations of the

rved SCS sandwich beam.

Fig. 19. Inclination angle of θ for curved SCS sandwich beam.

214 J.Y.R. Liew et al. / Journal of Constructional Steel Research 130 (2017) 202–221

specimens are illustrated in Fig. 13. Each specimen had a length of1200 mm and width of 495 mm. The stiffened plate specimen SP wasconstructed as a cellular steel structure with 3 mm internal plate

Fig. 20. SCS Panels subjec

stiffeners welded to the 4 mm face plates. The core thicknesses of thesteel-concrete-steel (SCS) sandwich specimens were 70 mm and theface plate thickness was 4 mm, 10 mm double J-hook connectors wereused to connect the face plates to the internal concrete core.

Three different structural grade concrete materials were employedas the sandwich core: normal strength concrete (NSC), lightweight ag-gregate concrete (LWAC) and ultra-high strength concrete (HSC). Asshown in Fig. 14, five 20 kg TNT (100 kg in total) military crater chargeswere arranged in an annular pattern and were placed at a standoff dis-tance of 5m from the specimens. The same arrangement and position ofthe charges were maintained in all the three blasts.

After the blast, the cellular stiffened plate panel (SP) experiencedvery large permanent deformation (N100mm). The sandwich specimen(SCS), which was subjected to the same blast load, sustained relativelyless deflection. The maximum permanent mid-span deformation was27 mm. Considering the two specimens which were designed as thesame face plate thickness, same stiffness, and same static flexural capac-ity, the difference is mainly attributed to the concrete core that addedmass and rigidity of the structural system. This demonstrated the effec-tiveness of SCS sandwich composite compared with the stiffened platepanel in terms of maintaining structural integrity and residual capacity.

Numerical analyses were carried out using LS-DYNA for sandwichpanels subjected to blast load. Only the effect of concrete core materialwas studied, which included the strength of concrete and mass of con-crete core. These SCS panels were subjected to large impulsive load of100 kg TNT detonated at 5 m. The general deformed shape at their re-spective peak displacements together with the history of the mid-span displacement of 3 panelswith different types of concrete filledma-terials: high strength concrete (HSC), normal weight concrete (NWC)

ted to punching load.

Fig. 21. Punching shear failure of curved SCS panels subjected to patch load.

215J.Y.R. Liew et al. / Journal of Constructional Steel Research 130 (2017) 202–221

and lightweight aggregate concrete (LWAC), are shown in Fig. 15. TheSCS panel with HSC infill core deflected the least while the panel withLWAC core exhibited the largest deflection. The analyses showed thatthe density of the core material and the mass of the structural systemplay a major role in the blast performance of a sandwich panel.

Numerical studies were conducted on blast performance of flat andcurved SCS sandwich panels subjected to large impulsive load 1000 kgTNT at 10 m. Fig. 16 shows the structural responses of flat and curvedSCS sandwich panels. By comparison of the failure mode and mid-span displacement versus time histories, it was found that the flatpanel experiences large flexural deformation (N80 mm) compared tothe curved panel (b10 mm) in which compressive arch action playedan essential role on improving the structural stiffness and deformationcapacity. It is because the rise-to-span ratio of curved panel not onlychanges the load transfer path but also transforms the failure from flex-ural mode to compressive dominated mode. In this way, curved sand-wich panel would be more efficient to resist the blast load, which canoffer a better alternative for the design of protective structures.

Fig. 22. Load-central deflection curves of curved SCS panels.

10. Curved sandwich structure

The expanding demand for oil and gas drives the petroleumexplora-tions in the Arctic region where large proportion of the world's undis-covered oil and gas are stored [37]. Curved sandwich compositestructure, consisting of two external steel curved shells with the annu-lus and sandwiched concrete core (see Fig. 1) has been proposed asthe ice-resistant walls in the Arctic offshore platform which aims to beused in the regionwith the water depth of 10 to 100m [38]. The curvedsandwich structure uses the arching effect to resist lateral load and ca-pable of spanning longer between supports.

10.1. Curved sandwich beams

The ultimate strength behaviour of the curved SCS sandwich beamshas been experimentally and numerically investigated by Yan et al. [39–43]. Fig. 17 shows the details of these tested curved SCS sandwichbeams. The test results showed that all these curved SCS sandwichbeams failed in shear tension mode as shown in Fig. 18. Design equa-tions have been developed to predict the transverse shear resistanceof the curved SCS sandwich beam [38].

The shear resistance of the curved SCS sandwich beam, VCB can bedetermined by [38]

VCB ¼ Vc þ Vsf þ V s ð16Þ

where Vc denotes shear resistance of the concrete core; Vsf denotesshear resistance of the steel face plate; Vs denotes shear resistance ofthe headed studs.

The shear resistance of the concrete core can be determined as

Vc ¼ vcBHce ð17Þ

where vc=uRd,c/γck(100ρfck)1/3+k1σcp, fck in MPa; uRd,c=0.18 fornormal weight concrete; 0.15 for lightweight concrete; k ¼ 1

þffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi200=hc

p≤2:0;hc in mm; ρ ¼ ffiffiffiffiffiffiffiffiffiffi

ρxρyp

≤0:02, ρx ,ρy relate to bondedtension steel in x- and y- directions respectively; σcp=(σcx+σcy)/2,σcx ,σcy are the normal concrete stresses in the critical section in x-and y-direction (in MPa, positive in compression); B denotes width ofthe beam.

Fig. 23. Comparison of predictions with test results.

216 J.Y.R. Liew et al. / Journal of Constructional Steel Research 130 (2017) 202–221

As shown in Fig. 19, owing to the rise of the arch, the actual depth ofthe curved SCS sandwich beam thatwas used to determine the shear re-sistance needs to be modified as the following [38]

Hce ¼ Rþ tt þ 2hcð Þ−ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiRþ tt þ hcð Þ2− b=2ð Þ2

qþ Rþ tsð Þ 1− cosαð Þð18Þ

whereb is thewidthof the loading area; Ladenotes the lengthbetween twomain shear cracks in the beam, and equals 2Rsinα as shown in Fig. 19; αis the angle offset from the centreline to the bottom tip of the shearcrack as shown in Fig. 19, which can be calculated as the following

α ¼ θ−cos−1 Rþ b tanθ=2þ hcR

cosθ� �

ð19Þ

Fig. 24. Fabrication of S

where, 0≤cos−1ðRþb tanθ=2þhcR cosθÞ≤90 °.

The tests and previous studies [5,6,38] show that the steel face plateshave significant influence on the shear resistances of the SCS sandwichstructure. Therefore, the shear resistance contributed by the top steelplate can be obtained by using the equivalent depth of the concretestructure as the following

Vsf ¼ min VcttEs=hcEck;f ysffiffiffi3

p Btt

� �ð20Þ

whereVc is the shear resistance of corematerial calculated by Eq. (21); ttis the thickness of steel face plate; Es is the elastic modulus of steel faceplate; hc is the depth of concrete core.

CS sandwich wall.

Fig. 25. Test set-up of SCS sandwich wall subjected to concentric (e = 0) or eccentric loading (e N 0).

217J.Y.R. Liew et al. / Journal of Constructional Steel Research 130 (2017) 202–221

The transverse shear resistance contributed by the overlapped head-ed shear studs can be determined as follows [38]:

V s ¼Xni¼1

Tihs sinβ

ihs ð21Þ

where n denotes number of the pairs of the overlapped connectors thatthe shear cracks cross in the section of the beam; i= ith connector; Thsi isthe tensile resistance of the ith concoctor; βhs

i is the inclination angle ofthe ith pair of overlapped shear connector to the horizontal surface asshown in Fig. 19.

The numerical and experimental study [38,39,43] showed that theshear resistance of the SCS sandwich beam was influenced by the rise-to-span ratio, span-to-height ratio, steel contribution ratio and supportrestraint conditions. Therefore, these parameters need to be controlledduring the construction to achieve the desired outcome.

10.2. Concentrated load acting on sandwich shells

Nine quasi-static tests on large scale curved SCS sandwich shellsunder concentrated loading that considers the localized ice-contactpressure were reported by Yan et al. [42,44] and two punching testson SCS sandwich shell subjected to large patch loadswere also conduct-ed [8]. Corresponding design equations have also been developed topredict the punching shear resistance of the SCS sandwich compositeshells [7,8,42,44]. Figs. 20 and 21 show the test set-up and failuremodes of curved SCS sandwich panel subjected to punching load. Thetest results showed that introducing the J-hook type of mechanicalshear connectors, adopting higher curvature for the curved SCS sand-wich structure, and using higher flexural reinforcing content and higherstrength concrete core would increase the punching shear resistance ofthe SCS sandwich shell structure. As shown in Fig. 22, the SCS sandwichshell structure exhibits two peak resistances P1 and P2, which corre-spond to the punching shear failure of the concrete core and thepunch through failure of the top steel shell, respectively.

Analytical models have also been developed to predict the punchingresistance based on these two failure modes as follows [42,44]

P1 ¼ 0:75VRd;c þ VRd;s ð22Þ

where VRd,c is the design punching shear resistance of the coremate-rial; VRd,s denotes the design punching shear resistance by the connec-tors or shear reinforcement.

Punching shear resistance contributed by the core material can bedetermined as [42,44],

VRd;c ¼ 2 Varch þ V long � ð23aÞ

Varch ¼ CRdkη1 100ρ1 f ckð Þ1=3h i

Lahlong ð23bÞ

V long ¼ CRdkη1 100ρ1 f ckð Þ1=3h i

Lbharch ð23cÞ

where CRd ,k ,η1, and ρ1, are specified in Section 6.2 under Eq. (11).

hlong ¼ hc þ tsEs=Ec ð24aÞ

harch ¼ Rþ ts þ 2hcð Þ−ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiRþ ts þ hcð Þ2− a=2ð Þ2

qþ Rþ tsð Þ

� 1− cosαð Þ þ tsEs=Ec ð24bÞ

where R denotes the radius of the shell; ts is the thickness of the steelshell; hc is the thickness of concrete core; a denotes the loading area;Es and Ec are the Young's modulus of steel and concrete, respectively.

The punching shear resistance contributed by the shear connectorscan be calculated as [42,44]

VRd;s ¼ nTht sinα ð25Þ

where T is tensile strength of the connectors, calculated by Eq.(2); n isthe quantity of overlapped connectors within the critical perimeter; htis the thickness of the shell section; S is the average spacing of the con-nectors; α is the inclination angle of the shear stud.

Fig. 26. Failure mode of SCS sandwich wall subjected to compression load applied at an eccentricity, e.

Fig. 27. N-M interaction diagram of SCS sandwich section.

218 J.Y.R. Liew et al. / Journal of Constructional Steel Research 130 (2017) 202–221

Fig. 28. Proposed N-M interaction model agaisnt Eurocode 4 prediction, test and FE results.

219J.Y.R. Liew et al. / Journal of Constructional Steel Research 130 (2017) 202–221

The punching shear resistance of the steel shell can bedetermined as

P2 ¼ σutsUp=ffiffiffi3

pð26Þ

whereUp is the perimeter of the patch loading area; ts is the thickness ofthe steel shell.

The predictions by the developed analytical models are comparedwith the tests results in Fig. 23. It shows that the developed analyticalmodel significantly improved the accuracy compared with the otheravailable design guidelines.

11. Sandwich wall subject to compression

Steel-concrete-steel (SCS) sandwich wall infilled with ultra-light-weight cement composite has been developed and proposed for appli-cations in offshore and building constructions. A new form of J-hookconnector is introduced to connect the external plates to improve thecomposite action between the steel face plates and cement compositecore to form an integrated unit which is capable of resisting extremeloads, as shown in Fig. 24. This research experimentally investigatesthe structural behaviour of SCS sandwich composite wall based on a se-ries of combined compression and uniaxial bending tests on short SCSsandwich composite wall with interlocking J-hook connectors [40,45].Fig. 25 shows the test set-up for SCS sandwich wall subjected to com-pression and uniaxial bending. From the tests, it is found that the SCSsandwichwall exhibits good structural behaviourwith a bending failuremodel. Fig. 26 illustrates typical failure mode namely concrete corecrushing followed by post buckling of steel face plates in the specimens.Analytical studies show that the N-M interaction model based onEurocode 4 may over-predict the combined resistance of the SCS sand-wich walls subjected to eccentric loading. Therefore, a modified ap-proach is proposed to evaluate the resistance of sandwich wall toimprove the methodological equation so as to gain a more accurateand conservative prediction. Fig. 27 shows theN-M interaction diagramof SCS sandwich section in which point A represents themodified resis-tance under pure compression, point B represents the balanced failureand the range from point A to B would be in compression failure(small eccentricity), and Point C represents the status of pure bendingwhile the range from point B to point C would be in tension failure(large eccentricity).

To generate the N-M interaction diagram, except the data in purecompression and pure bending, various values of axial loadN and bend-ing moment M should be evaluated. For a given section, the interaction

diagram is generated by selecting successive choices of neutral axis dis-tance xc, from infinity (axial load with eccentricity 0) to a very smallvalue given N = 0 (pure bending). In compression failure range (frompoint A to point B), this is done by assuming the compressive strain ofextreme concrete fiber as achieving to εcu which is the ultimate concretecompression strain. In tension failure range (from point B to point C),this is done by assuming the tensile strain of extreme steel fiber asachieving to εy= fy/Es which is the yield strain of steel.

The axial force and the bending moment equilibrium equations atthe failure moment are displayed as follows.

(1) Pure compression: Point A

By considering the buckling effect of steel face plate, the compres-sion resistance of SCS sandwich wall is calculated by

NA ¼ Npl;Rk ¼ 0:85Ac f ck þ ϕaAs f ys ð27Þ

where ϕa=0.898R−0.771 (R≥0.85) [45], Ac is cross-sectional area ofconcrete; fck is compressive strength of concrete; As is cross-sectionalarea of steel plate; fys is yield strength of steel; R is the width-thickness

ratio, defined as R ¼ Wt

ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi12ð1−ν2Þ f ys

4π2Ea

q≥0:85.

(2) Compression failure: branch AB

Nu ¼ 12f ckbxc þ f 0ystAst−σ sbAsb ð28Þ

Nue ¼ 12f ckbxc hc−

xc3þ tb

2

� �þ f 0ystAst hc þ tbð Þ ð29Þ

where,e ¼ e0 þ hc2 þ tb

2, b is thewidth of section; fyst′Ast is the compressionforce by steel plate in compression side, σsbAsb is the compression forceor tension force by steel plate in tension side.

(3) Tension failure: branch BC

Similarly, the force equilibrium is expressed by

Nu ¼ 12f ckbxc þ f 0ystAst− f 0ysbAsb ð30Þ

220 J.Y.R. Liew et al. / Journal of Constructional Steel Research 130 (2017) 202–221

Mu ¼ Nue ¼ 12f ckbxc hc−

xc3þ tb

2

� �þ f 0ystAst hc þ tbð Þ ð31Þ

where,e ¼ e0 þ hc2 þ tb

2,εyεc ¼ hc−xc

xc,σc=Ecεc≤ fck; fysb′Asb is the tension force

by steel plate in tension side.Fig. 28 illustrates the validation against the test and FE results, show-

ing a reasonable and conservative estimation on the combined resis-tance of SCS sandwich wall. This suggests that the proposed modelcan offer close and conservative predictions for combined compressionand bending resistance of SCS sandwichwall that filled with ultra-light-weight cement composite. Considering the accuracy of the predictions,Eqs. (27)–( 31) are recommended for the check of the resistance ofSCS sandwich wall under combined compression and bending.

12. Conclusions

Novel J-hook connectors and new ultra-lightweight cement com-posite (ULCC) core material with density as low as 980 kg/m3 havebeen developed to enhance the strength to weight ratio and the struc-tural performance of sandwich composite structures. Experimentaland analytical studies were carried out to investigate the structural be-haviours of SCS sandwich structures under static, fatigue, impact andblast loads. Based on these experimental and analytical studies, the fol-lowing conclusions can be drawn:

(1) The use of ultra lightweight cement composite material and highstrength steel was feasible to produce slim form of SCS sandwichstructure and to achieve higher strength to weight ratio com-pared to stiffened plate construction.

(2) Novel mechanical connectors were developed to offer effectiveshear and tensile bond between the steel face plates and the ce-ment composite core. Design equations to predict the shear, ten-sion, and shear-tension interaction resistances of the J-hookshear connectors were developed and the accuracy was verifiedagainst numerical and experimental results.

(3) Flexural and shear behaviours of the SCS sandwich beams havebeen studied experimentally. Design formulae to predict thebending and shear resistances have been proposed and verifiedagainst test results.

(4) Results from fatigue tests on SCS beams showed that their fatiguelife was affected by both the fatigue stress range and maximumapplied stress. The maximum applied stress and stress range af-fected the structural behaviour of the SCS sandwich system.Their fatigue life reduced when the load range or maximum ap-plied load increased. A new three-parameter fatigue designequation was proposed based on calibration with test data.

(5) Instrumented drop weight tests have been conducted on a num-ber of SCS sandwich slabs to evaluate their resistance againstlarge mass projectile/fragment impact. The steel plate strengthand thickness, and the tensile resistance of the J-hook connectorsare the controlling parameters that affect the punching resis-tance of the SCS sandwich plate subject to low velocity impact.The proposed interlocked J-hook shear connectors provide addi-tional resistance to prevent tensile separation of the face platesand enhance the shear resistance of the sandwichpanel. An ener-gy balance model is proposed to analyse the energy absorptioncapacity of SCS sandwich slabs. The deflection of the SCS sand-wich slab can be determined with reasonable accuracy usingthis model, and this can be used to assess the damage levels ofthe SCS sandwich slabs subject to impact load provided the fail-ure was not due to projectile punching through the top plate.

(6) Blast testswere carried out on SCS sandwich plates and their per-formances were compared with stiffened steel plates. The blastperformance of SCS panels improved with the increase in theoverall flexural stiffness and the weight of the internal core ma-terial as compared to steel plates without the internal core

material. The permanent deformations of the SCS sandwichplates subject to blast loadwas lower compared to the equivalentstiffened steel plates subject to the same blast load. The blast per-formance of SCS sandwich structures coupled with their engi-neering flexibility and construction economy make themsuitable to be used as protective structures.

(7) Tests on the curved SCS sandwich shells subjected to patch loadwere carried out. The SCS shells have better design resistanceagainst high punching shear force compared to flat panels be-cause of the arching action. Design formulae to predict thepunching shear resistance of the SCS sandwich shell structurewere proposed and verified against the test results. The designformulae considered the rise-to-span effect, steel plate thicknessand failure mode of shear connectors in the SCS sandwich shell.

(8) Tests on SCS sandwich walls subjected to compression and mo-ment were performed. Test observations showed that SCS sand-wich walls exhibited excellent compression resistance and postpeak ductility if J-hook connectors were provided to prevent sep-aration of the face plates. A newN-M interactionmodel was pro-posed and its accuracy was verified against the test and FEresults. Comparison of results showed that the proposedmethodprovided reasonable and conservative estimations compared tothe Eurocode 4 method.

Acknowledgements

The authors would like to acknowledge the research grant R-302-501-002-490 received from the Maritime and Port Authority of Singa-pore for conducting parts of the works reported herein. The researchworks contributed by Dr. KMA Sohel, Dr. Dai XX, Dr. Wang TY, Dr.Kang KW, Dr. Lee SC, Dr. Chia KS, Dr. Wang Yonghui and Dr. Wang JYare gratefully acknowledged.

References

[1] J.Y.R. Liew, K.M.A. Sohel, Lightweight steel-concrete-steel sandwich system with J-hook connectors, Eng. Struct. 31 (2009) 1166–1178.

[2] J.Y.R. Liew, T.Y. Wang, Novel steel-concrete-steel sandwich composite plates subjectto impact and blast load, Adv. Struct. Eng. 14 (4) (2010) 673–687.

[3] X.X. Dai, J.Y.R. Liew, Fatigue performance of lightweight steel–concrete–steel sand-wich systems, J. Constr. Steel Res. 66 (2) (2010) 256–276.

[4] J.Y.R. Liew, K.M.A. Sohel, C.G. Koh, Impact tests on steel-concrete-steel sandwichbeams with lightweight concrete core, Eng. Struct. 31 (9) (2009) 2045–2059.

[5] J.B. Yan, L. JYR,M.H. Zhang, J.Y.Wang, Ultimate strength behaviour of steel-concrete-steel sandwich composite structures, part 1: experimental and analytical study,Steel Compos. Struct. 17 (6) (2014) 907–927.

[6] J.B. Yan, J.Y.R. Liew, M.H. Zhang, K.M.A. Sohel, Experimental and analytical study onultimate strength behaviour of steel-concrete-steel sandwich composite beamstructures, Mater. Struct. 48 (5) (2015) 1523–1544.

[7] J.B. Yan, X.M. Liu, L. JYR, X. Qian, M.H. Zhang, Steel–concrete–steel sandwich systemin Arctic offshore structure: materials, experiments, and design, Mater. Des. 91(2016) 111–121.

[8] Z.Y. Huang, J.Y. Wang, J.Y.R. Liew, P.W. Marshall, Lightweight steel–concrete–steelsandwich composite shell subject to punching shear, Ocean Eng. 102 (2015)146–161.

[9] A.H. Varma, S.R. Malushte, K.C. Sener, Z. Lai, Steel-plate composite (SC) walls forsafety related nuclear facilities: design for in-plane forces and out-of-plane mo-ments, Nucl. Eng. Des. 269 (2014) 240–249.

[10] J.C. Bruhl, A.H. Varma, J.M. Kim, Static resistance function for steel-plate composite(SC) walls subject to impactive loading, Nucl. Eng. Des. 15 (2015) 843–859.

[11] S.K. Solomon, D.W. Smith, A.R. Cusens, Flexural tests of steel-concrete-steel sand-wiches, Mag. Concr. Res. 28 (94) (1976) 13–20.

[12] M.J. Tomlinson, A. Tomlinson, M. Chapman, A.D. Jefferson, H.D. Wright, Shell com-posite construction for shallow draft immersed tube tunnels, Institute of Civil Engi-neers, Proceedings of the ICE International Conference on Immersed Tube TunnelTechniques. Manchester, Thomas Telford, London, 1990.

[13] H. Bowerman, N. Coyle, J.C. Chapman, An innovative steel/concrete construction sys-tem, Struct. Eng. 80 (20) (2002) 33–38.

[14] N. Malek, A. Machida, H. Mutsuyoshi, T. Makabe, Steel-concrete sandwich memberswithout shear reinforcement, Trans. Jpn. Concr. Inst. 15 (2) (1993) 1279–1284.

[15] J.B. Yan, J.Y. Wang, J.Y.R. Liew, M.H. Zhang, Applications of ultra-lightweight cementcomposite in flat slabs and double skin composite structures, Constr. Build. Mater.111 (2016) 774–796.

221J.Y.R. Liew et al. / Journal of Constructional Steel Research 130 (2017) 202–221

[16] J.Y. Wang, K.S. Chia, L. JYR, M.H. Zhang, Flexural performance of fiber-reinforcedultra-lightweight cement composites with low fiber content, Cem. Concr. Compos.43 (2013) 39–47.

[17] K.M.A. Sohel, J.Y.R. Liew, J.B. Yan, M.H. Zhang, K.S. Chia, Behaviour of steel-concrete-steel sandwich structures with lightweight cement composite and novel shear con-nectors, Compos. Struct. 94 (12) (2012) 3500–3509.

[18] J.B. Yan, L. JYR, M.H. Zhang, J.Y. Wang, Mechanical properties of mild steel and highstrength steel S690 under low temperature relevant to Arctic environment, Mater.Des. 61 (2014) 150–159.

[19] J.B. Yan, W. Zhang, L. JYR, Z.X. Li, Numerical studies on shear resistance of headedstud connectors in different concretes under Arctic low temperature, Mater. Des.112 (2016) 184–196.

[20] M.X. Xiong, J.Y.R. Liew, Mechanical properties of heat-treated high tensile structuralsteel at elevated temperatures, Thin-Walled Struct. 98 (1) (2016) 169–176.

[21] F. Aslani, B. Uy, Z. Tao, F. Mashiri, Behaviour and design of composite columns incor-porating compact high-strength steel plates, J. Constr. Steel Res. 107 (2015) 94–110.

[22] Eurocode 4, Design of composite steel and concrete structures—part 1.1: generalrules and rules for buildings, BS EN 1994-1-1, Brussels, 2004.

[23] J.B. Yan, J.Y.R. Liew, K.M.A. Sohel, M.H. Zhang, Push-out tests on J-hook shear con-nectors in steel-concrete-steel sandwich structure, Mater. Struct. 47 (10) (2014)1693–1714.

[24] J.B. Yan, J.Y.R. Liew, M.H. Zhang, Tensile resistance of J-hook connectors used insteel-concrete-steel sandwich structure, J. Constr. Steel Res. 100 (2014) 146–162.

[25] Eurocode 3, Design of steel structures—part 1-1: general rules and rules for build-ings, BS EN 1993-1-1, Brussels, 2005.

[26] J.B. Yan, J.Y.R. Liew, M.H. Zhang, Shear-tension interaction strength of J-hook con-nectors in steel-concrete-steel sandwich structure, Adv. Steel Constr. 11 (1)(2015) 72–93.

[27] A.J. Wang, K.F. Chung, Advanced finite element modelling of perforated compositebeams with flexible shear connectors, Eng. Struct. 30 (10) (2008) 2724–2738.

[28] J.B. Yan, L. JYR, M.H. Zhang, Ultimate strength behaviour of steel-concrete-steelsandwich composite structures, part 2: finite element analysis, Steel Compos. Struct.18 (4) (2015) 1001–1021.

[29] J.B. Yan, Finite element analysis on finite element analysis on ultimate strength be-haviour of steel-concrete-steel sandwich composite beam structures, Mater. Struct.48 (6) (2015) 1645–1667.

[30] Eurocode 2, Design of concrete structures — part 1-1: general rules and rules forbuildings, BS EN 1992-1-1, Brussels, 2004.

[31] T.M. Roberts, D.N. Edwards, R. Narayanan, Testing and analysis of steel-concrete-steel sandwich beams, J. Constr. Steel Res. 38 (3) (1996) 257–279.

[32] T.O.S. Oduyemi, H.D. Wright, An experimental investigation into the behaviour ofdouble skin sandwich beams, J. Constr. Steel Res. 14 (3) (1989) 197–220.

[33] N. Foundoukos, Behaviour and Design of Steel-Concrete-Steel SandwichConstructionPhD thesis Department of Civil and Environmental Engineering, Uni-versity of London, 2005.

[34] B. McKinley, L.F. Boswell, Behaviour of double skin composite construction, J. Constr.Steel Res. 58 (10) (2002) 1347–1359.

[35] A.M. Remennikov, S.Y. Kong, B. Uy, The response of axially restrained non-compos-ite steel–concrete–steel sandwich panels due to large impact loading, Eng. Struct. 49(2013) 806–818.

[36] K.M.A. Sohel, J.Y.R. Liew, Behavior of steel–concrete–steel sandwich slabs subject toimpact load, J. Constr. Steel Res. 100 (2014) 163–175.

[37] D.L. Gautier, K.J. Bird, R.R. Charpentier, A. Grantz, D.H. Houseknecht, T.R. Klett, T.E.Moore, J.K. Pitman, C.J. Schenk, J.H. Schuenemeyer, K. Sørensen, M.E. Tennyson,Z.C. Valin, C.J. Wandrey, Assessment of undiscovered oil and gas in the Arctic, Sci-ence 324 (2009) 1175–1179.

[38] J.B. Yan, J.Y.R. Liew, X.D. Qian, J.Y. Wang, Ultimate strength behaviour of curvedSteel-Concrete-Steel sandwich composite beams, J. Constr. Steel Res. 115 (2015)316–328.

[39] J.B. Yan, M.X. Xiong, X. Qian, J.Y.R. Liew, Numerical and parametric study of curvedSteel-Concrete-Steel sandwich composite beams under concentrated loading,Mater. Struct. 49 (10) (2016) 3981–4001.

[40] Z.Y. Huang, J.Y.R. Liew, M.X. Xiong, J.Y. Wang, Structural behaviour of double skincomposite system using ultra-lightweight cement composite, Constr. Build. Mater.86 (2015) 51–63.

[41] Z.Y. Huang, L. JYR, Experimental and analytical studies of curved steel-concrete-steelsandwich panels under patch loads, Mater. Des. 93 (2016) 104–117.

[42] J.B. Yan, J.Y.R. Liew, M.H. Zhang, Z.X. Li, Punching shear resistance of steel–concrete–steel sandwich composite shell structure, Eng. Struct. 117 (2016) 470–485.

[43] Z.Y. Huang, J.Y.R. Liew, Nonlinear finite element modelling and parametric study ofcurved steel–concrete–steel double skin composite panels infilled with ultra-light-weight cement composite, Constr. Build. Mater. 95 (2015) 922–938.

[44] J.B. Yan, X.D. Qian, J.Y.R. Liew, L. Zong, Damage plasticity based numerical analysis onsteel–concrete–steel sandwich shells used in the Arctic offshore structure, Eng.Struct. 117 (2016) 542–559.

[45] Z.Y. Huang, J.Y.R. Liew, Structural behaviour of steel-concrete-steel sandwich com-posite wall subjected compression and end moment, Thin-Walled Struct. 98(2016) 592–606.

本文献由“学霸图书馆-文献云下载”收集自网络，仅供学习交流使用。

学霸图书馆（www.xuebalib.com）是一个“整合众多图书馆数据库资源，

提供一站式文献检索和下载服务”的24 小时在线不限IP

图书馆。

图书馆致力于便利、促进学习与科研，提供最强文献下载服务。

图书馆导航：

图书馆首页 文献云下载 图书馆入口 外文数据库大全 疑难文献辅助工具