Ultimate strength behavior of curved steel–concrete–steel sandwich composite beams
Introduction
The steel–concrete–steel (SCS) sandwich structure, comprising two external steel skin plates and a sandwiched concrete core, is a relatively new type of structure and becomes popular in recent three decades [1], [2], [3]. Compared with the normal reinforced concrete structure widely used in civil constructions, the SCS sandwich structure exhibits distinctive advantages, such as saving formworks of concrete casting, shortening site construction time, relative high resistances to static, impact, and fatigue loadings [4], [5], [6]. This type of structure exhibits superiorities in applications which require high strength, high ductility, high blast and impact resistances [5], [6], [7], [8]. The potential applications of the SCS sandwich structure include submerged tunnels, ship hulls, bridge and offshore decks, shear walls in the high-rise building, walls in the nuclear structures, and protective structures [5], [6], [7], [8], [9].
In steel–concrete–steel (SCS) sandwich structures, mechanical shear connectors or cohesive materials are common measures to enhance the composite action at the steel-concrete interface. Cohesive materials, e.g., epoxy, offer continuous bond at the steel-concrete interface. However, imperfections in the epoxy workmanship compromise the structural performance of SCS sandwich composite structure [10]. Mechanical shear connectors offer discrete point-bonding that depends on their spacing in the structure. The main advantage of the mechanical shear connectors over cohesive materials is bridging the shear cracks in the concrete core to provide transverse shear resistance. Different types of mechanical shear connectors have been developed for the SCS sandwich structure, e.g., headed studs in ‘Double skin’ structure [2], friction welded connectors in ‘Bi-steel’ structure [11], laser-welded corrugated connectors [12], J-hook connectors [3], [4], [5], [6], [7], [8], and angle connectors [13]. Including the innovations of the connectors in the SCS sandwich structure, different types of concrete materials have emerged and evolved in the development of SCS sandwich structures [1], [2], [3], [4], [5], [6]. In the early studies, normal weight concrete (NWC) was used as the core materials [1], [2]. In order to reduce the self-weight and make the SCS sandwich structure as a competitive option for the marine and offshore constructions, lightweight concrete (LWC) made of expanded clay type of coarse aggregate was developed for the SCS sandwich structure [5], [6], [14]. The ultra-lightweight cement composite (ULCC) further increased the strength to 60 MPa but retained the density at 1400 kg/m3 [15], [16]. All these developments in the lightweight concrete materials provide more choices to develop the marine and offshore SCS sandwich structures.
Curved steel–concrete–steel sandwich structure has been proposed as the ice resistant wall in the Arctic offshore structures for the oil drilling and productions as shown in Fig. 1 [3], [17], [18]. This structure consists of two external rolling-formed steel shells and a sandwiched lightweight core. This study used the ULCC as the core material and the headed studs with overlap to bond different components working as integrity. Previous studies focused either on the curved reinforced concrete plates [19], [20], [21] or curved SCS sandwich structures without bond enhancement [22]. There is still limited information on the curved SCS sandwich structure especially for this type of structure with lightweight concrete core and shear connectors. Further investigations are thus necessary to advance the understanding on the strength development and failure mechanism of the curved SCS structures to support design protocols in engineering guidelines, which does not currently include provisions for such composite structures [23], [24].
Localised high-pressure zones (HPZ) [25], [26], [27] have become a critical design consideration for Arctic offshore structures, which experience non-uniform pressure caused by a moving ice floe or ice sheet. In this study, the curved SCS sandwich beams were tested under patch loading that considered this critical scenario under the high-pressure-concentrated ice loading.
This paper reported a test program comprising ten curved SCS sandwich beams to examine the failure modes and ultimate load carrying capacities. The experimental results demonstrate that design equations in Eurocode 4 [23] should include essential modifications on the inclination angle of the shear failure surface, the equivalent depth of the curved SCS sandwich beam, and the consideration of the influence of the steel face skin. These modifications lead to a set of new design equations capable of predicting the shear resistance of the curved SCS sandwich beam under patch loading.
Section snippets
Experimental program
The experimental program comprises ten curved SCS sandwich beams. These specimens cover the variation of the critical parameters that influence the ultimate strength of the structure, including thickness of the steel face plate, curvature of the beam, spacing of the connectors, strength of the concrete core, depth of the cross section, and the horizontal restraint stiffness of the support.
General load-deflection behaviors
Fig. 7 plots the load-central deflection curves of the beams. Overall, the load-central deflection curves exhibit brittle behavior and the load carrying capacity cannot sustain at a level after it achieves the ultimate value, i.e., there is a sharp drop in the load-deflection curves.
Fig. 8 depicts the generalized load-deflection curves of the curved SCS sandwich beams failed in shear mode that exhibits four distinct working stages. At stage OA, the curved beam behaved linearly and no cracks
Analysis on shear resistance of the curved SCS sandwich beam
Current design guideline on SCS sandwich structures has several limitations when they are used to predict the shear resistance of the SCS sandwich structures [24] as the following
- 1)
Neglecting the influence of the curvature
- 2)
Ignoring the influence of the steel face plate
- 3)
Overestimating the tensile resistance of the connectors used in the structure (ultimate tensile fracture strength of the connector is used instead)
The design equation proposed by Narayanan et al. [24] is used to predict the shear
Conclusions
This paper studies the ultimate strength behavior of the curved SCS sandwich beams through ten quasi-static tests. The test program investigates the influences of different parameters on the resistances of the curved SCS sandwich beams, and extensive discussions are made based on these experimental observations. Analytical models have been developed to predict the shear resistance of the curved SCS sandwich beam. Based on the experimental and analytical studies, the following conclusions are
Acknowledgements
The research described herein was funded by the Maritime and Port Authority of Singapore, and supported by the American Bureau of Shipping (ABS) and National University of Singapore under research project titled “Curved steel–concrete–steel sandwich composite for Arctic region” (Project No. R-302-501-002-490).
References (38)
- et al.
Tensile resistance of J-hook connectors in SCS sandwich composite structure
J. Constr. Steel Res.
(2014) - et al.
Impact tests on steel–concrete–steel sandwich beams with lightweight concrete core
Eng. Struct.
(2009) - et al.
Fatigue performance of lightweight steel–concrete–steel sandwich systems
J. Constr. Steel Res.
(2010) - et al.
Finite element analysis of steel–concrete–steel sandwich beams
J. Constr. Steel Res.
(2008) - et al.
Static tests on steel–concrete–steel sandwich beams
J. Constr. Steel Res.
(2007) - et al.
Evaluation of the transverse shear stiffness of a steel bi-directional corrugated-strip-core sandwich beam
J. Constr. Steel Res.
(2011) - et al.
steel–concrete–steel sandwich slabs with lightweight core-Static performance
Eng. Struct.
(2011) - et al.
Flexural performance of fiber-reinforced ultra-lightweight cement composites with low fiber content
Cem. Concr. Compos.
(2013) - et al.
Stability of cenospheres in lightweight cement composites in terms of alkali–silica reaction
Cem. Concr. Res.
(2012) Non-simultaneous crushing during edge indentation of freshwater ice sheets
Cold Reg. Sci. Technol.
(1998)
High pressure zone formation during compressive ice failure
Eng. Fract. Mech.
Mechanics of ice-structure interaction
Eng. Fract. Mech.
Shear performance of prestressed ultra-high strength concrete encased steel beams
Constr. Build. Mater.
Flexural tests of steel–concrete–steel sandwiches
Mag. Concr. Res.
An experimental investigation into the behaviour of double skin sandwich beams
J. Constr. Steel Res.
Experimental and analytical study on ultimate strength behaviour of steel–concrete–steel sandwich composite beam structures
J. Mater. Struct.
Ultimate strength behaviour of steel–concrete–steel sandwich composite structures, Part 1: Experimental and analytical Study
Steel Compos. Struct. Int. J.
Push-out tests on J-hook connectors in steel–concrete–steel sandwich structure
J. Mater. Struct.
An Experimental Investigation on Shear Bond Strength between Steel and Fresh Cast Concrete Using Epoxy
IES J. A Civ. Struct. Eng.
Cited by (31)
Steel-concrete-steel sandwich composite structures: A review
2024, Engineering StructuresAnalysis of steel-concrete-steel sandwich plate structure
2022, Materials Today: ProceedingsBehavior of steel-concrete-steel sandwich beams with blot connectors under off-center impact load
2021, Journal of Constructional Steel ResearchFlexural behavior of curved steel-plate composite (SC) walls under combined axial compression and cyclic lateral force
2021, Engineering StructuresCitation Excerpt :Two T/R ratios of the curved SC walls (0.2 and 0.5) were considered without any change in other parameters for the additional curved FE models named SC20-IP, SC20-OP, SC50-IP and SC50-OP. It should be noticed that the sector angles (Lw/R) of these FE models are up to 1.417 (81.2° in degree), which is a common value in previous studies about curved SC walls [22,24,25,44]. The flexural capacities, stiffness degradation and energy dissipation abilities of the four FE models were presented in Fig. 9, Fig. 11 and Fig. 12, respectively.
Experimental study on the flexural behavior of cold-formed U-shaped steel-encased confined prestressed RC beam
2021, Journal of Constructional Steel Research