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Mitigation of blast effects caused by accidental explosions is one of the major challenges in structural engineering. Fiberreinforced polymer (FRP) sandwich panels offer promising systems for blast mitigation applications due to their considerable energy absorption compared to other materials with similar density. The FRP sandwich panels can have different inner core configurations that can be filled with other materials whenever needed. This paper numerically evaluates the effectiveness of new FRP honeycomb sandwich panels in resisting blast loads. A numerical model has been created using nonlinear explicit finite element simulation. Then, the model has been validated using the experimental field tests in the literature. Twelve FRP panels with different inner core configurations have been proposed to enhance the panels' performance by reducing their peak deformation and increasing their energy dissipation. The paper also investigates the effect of filling the FRP sandwich panels with sand on the panels' blast resistance. The analyses have shown that the FRP panels utilizing the new core configurations are able to dissipate more than twice the energy compared to the experimental panels with even less deformations. It has been found that using sand as a filling material provides a damping medium that enhances the panels' behavior under blast effect. [ABSTRACT FROM AUTHOR]

This paper investigates the load-bearing capability of sandwich panels (composed of fiber-reinforced polymer faces and a foam core) connected by aluminum hinges in an origami-inspired deployable structure intended for temporary sheltering. The structure is studied (1) during deployment (loaded under self-weight only), and (2) as both individual and combined modules subjected to uniform pressures emulating wind loads. The measured results are used to validate finite element models, with comparisons focusing on surface strains and displacements at panel centers (to study global behavior), as well as surface strains near connections (to study local behavior). The validated numerical models are used to perform parametric studies investigating design decisions for (1) deployment, including panel reinforcement, location of lifting equipment, and size of lifting equipment, and (2) combined modules, including restraints and connections between modules, gasketing between panels, and panel reinforcement. This research ultimately demonstrates the load-bearing capability of deployable structures composed of hinged sandwich panels and provides design guidelines and recommendations. [ABSTRACT FROM AUTHOR]

Green building practices have created an opportunity for the forest products industry to become a leader in the creation of in- novative building products derived from renewable materials. In other industries, sandwich composites have proven to be efficient structures by meeting structural demands of traditional panel products while consuming less material. A prototype molded-core sandwich panel made of span-rated oriented strand board (OSB) facings and a bidirectional molded wood-strand core was produced. Critical mechanical properties were evaluated to determine the feasibility of this product for use in building applications. The goals of this study were to generate details on structural performance of the product, validate the design, and provide suggestions for future product development. Results indicate that this molded-core panel performs particularly well in flexure while connection properties had the largest scope for improvement. Sufficient performance was observed to validate the design, warranting production and testing of panels sized for end-use. Future product development should explore different connection systems, perform detailed engineering analyses of the mechanical properties necessary for complete structural design, and characterize physical properties of the panel. [ABSTRACT FROM AUTHOR]

This paper presents finite-element analyses and analytical models of innovative, small-scale, prototype deck panels examined under monotonic bending. The deck panels consisted of two glass fiber-reinforced polymer (GFRP) facesheets separated by webs formed from E-glass-woven fabric placed around trapezoidal-shaped, low-density, polyurethane foam segments. The proposed panel exhibited a higher structural performance in terms of flexural stiffness, strength, and shear stiffness than those of conventional sandwich panels. Analytical models were used to predict critical facesheet wrinkling in the sandwich panel. Furthermore, a three-dimensional model using simulation software was developed for analysis of the proposed panel system under monotonic four-point loading. The finite-element results in terms of strength, stiffness, and deflection were found to be in good agreement with those from the experimental results. A parametric study was also conducted to further evaluate the effects of the stiffness of the top facesheet fiber layers, the mass density of the polyurethane foam, the existence of web layers, and the introduction of an overlay above the top facesheet. A flexural beam theory approach was used to predict the flexural strength of the sandwich panel. [ABSTRACT FROM AUTHOR]

This paper discusses the impact of hinged connectors (a common connection in folding structures) on the behavior of sandwich panels (with fiber-reinforced polymer faces and foam core). A sandwich panel is subjected to uniform loading and tested when restrained by hinged connectors in compression and in tension. The measured results are compared to finite-element numerical models, focusing on global behavior (displacements and strains at center) and local behavior (strains near connectors). Parametric studies using these validated numerical models investigate the impact of the number, size, and relative placement of hinged connectors. These studies culminate in guidelines for the design of structures comprised of hinged, folding panels. Ultimately, this paper addresses a research gap in understanding the behavior of sandwich panels connected by hinges. [ABSTRACT FROM AUTHOR]

This paper presents the evaluation of an innovative low-cost small-scale prototype deck panel under monotonic and fatigue bending. This new system introduces a trapezoidal-shaped polyurethane foam core with a thermoset polyurethane resin that has a longer pot life to facilitate the infusion process. The proposed panel exhibited a higher structural performance in terms of flexural stiffness, strength, and shear stiffness. The panels consist of two glass fiber-reinforced polymer (GFRP) facings with webs of bidirectional E-glass-woven fabric that are separated by a trapezoidal-shaped low-density polyurethane foam. The GFRP panels were manufactured using a one-step vacuum-assisted resin transfer molding process. The specimens studied were constructed in the Composite Manufacturing Laboratory in the Mechanical and Aerospace Engineering Department at Missouri University of Science and Technology. Small-scale prototype deck panels were tested both statically and dynamically in four-point bending to investigate their flexural behavior. The ultimate bearing capacity of the proposed sandwich panels was determined from compression crushing tests. In addition, the load-deflection behavior of the proposed panel was investigated under three loading conditions: compression, static flexure, and dynamic flexure. The initial failure mode for all panels was localized outward-compression skin wrinkling of the top facing. The ultimate failure was caused by local crushing of the top facing under the loading point due to excessive compressive stresses. First-order shear deformation theory was used to predict the panel deformation in the service limit state. In general, the analytical results were found to be in good agreement with the experimental findings. [ABSTRACT FROM AUTHOR]

Structural sandwich panels with fiber-reinforced polymer (FRP) skins are becoming an increasingly popular system because of their remarkable light weight, ease and speed of installation, and high thermal insulation capabilities. This paper looks into the potential for replacing conventional glass fiber-reinforced polymer (GFRP) skins with bio-based skins made of unidirectional flax fibers and a resin blend consisting of epoxidized pine oil. A comprehensive material testing program was first carried out on 70 standard tension and compression coupons. Then, 36 sandwich panels of 1,000 x 150 x 75 mm were tested under four-point loading. The number of flax fiber-reinforced polymer layers of skin was varied from one to five [in comparison to one layer of GFRP, an epoxidized pine oil resin blend to epoxy, and the wet layup (WL) fabrication method to vacuum bag molding]. Sandwich panels with three layers of flax fibers provided equivalent strength and stiffness, but better deformability, compared to panels with one layer of glass fibers. Epoxidized pine oil-based skins decreased strength by up to 23% compared to epoxy-based skins. Vacuum-bagged panels decreased strength by up to 27% compared to WL as a result of thinner skins. As the number of flax layers increased from one to five, failure modes transitioned from skin wrinkling in the constant moment region to core shear failure or compression skin crushing in the shear span. [ABSTRACT FROM AUTHOR]

This paper discusses self-supporting sandwich panels, which are used as wall and roof cladding. They consist of two external thin and flat facings and a thick soft core. The panels are subjected to mechanical and temperature actions. The aim of this paper was to find the optimal solution for supports of a multispan sandwich structure. The following support models were considered: rigid support and linear-elastic support, with or without an imposed limit of elastic deflection. The problem was formulated as a two-criterion optimization (i.e., the maximization of the load multiplier and the maximization of the allowable length of the span). The criteria were in mutual exclusion (i.e., the results of the optimization comprise a set of nondominated optimal solutions). It shows that the optimal choice of supporting conditions remarkably improves the capacity of thermally loaded sandwich panels used in civil engineering. [ABSTRACT FROM AUTHOR]

Precast concrete floor systems represent a major component of the cost and weight of precast concrete buildings. Hollow-core (HC) planking is considered the most common precast concrete floor system for residential and commercial buildings because of their economy, light weight, structural capacity, and ease of production and erection. However, the high thermal conductivity of HC planks hinders their use in radiant heated floor and roof applications where thermal insulation is needed. This paper presents the development of a precast/prestressed concrete sandwich floor panel that consists of an internal wythe of insulation and two external wythes of concrete similar to those used in sandwich wall panels. The main difference between the sandwich floor and wall panels is the design of shear connectors between concrete wythes to achieve full composite action under ultimate loads while simultaneously having an adequate creep resistance under sustained loads and acceptable deflection under live loads. Truss-shaped glass fiber-reinforced polymer ties, known as NU ties, were used as shear connectors because of their structural and thermal efficiency. The proposed floor panels have comparable weight and capacity to HC planks while being more thermally efficient and can easily be fabricated in standard casting beds with typical equipment, thus eliminating the high initial investment required for HC production. This paper presents the design, detailing, production, and testing of three 7.9-m-long (26-ft-long), 1.22-m-wide (4-ft-wide), and 200-mm-thick (8-in.-thick) specimens with 50-mm-thick (2-in.-thick) composite topping. The three specimens represent two different panel designs. One specimen has solid concrete ends and was designed for a total superimposed service load of 9.6 kPa (200 psf), whereas two specimens are fully insulated and designed for a total superimposed service load of 4.8 kPa (100 psf). The performance of the three specimens under flexure and shear loadings indicated that the proposed sandwich floor panels can achieve full composite action and have satisfactory structural performance and acceptable deflection characteristics. [ABSTRACT FROM AUTHOR]

Precast concrete sandwich panels have been used in building construction since the 1960s. These sandwich wall panels are constructed with two wythes of concrete separated by a layer of thermal foam plastic insulation and a shear connector mechanism between concrete wythes. Recently, more research is focused on fiber-reinforced composite grids as shear connectors due to their superior thermal performance compared to other connectors such as steel or solid concrete. However, while there are guidelines for design of concrete sandwich panels, there is no standardized guidance that provides testing and capacity determination for composite shear connectors. Therefore, testing and acceptance criteria were developed to evaluate the shear transfer capacities of fiber-reinforced composite grid connectors used in combination with rigid insulation in concrete sandwich panel construction. The criteria are intended to standardize testing and evaluation of the interaction between concrete and composite shear connectors so manufacturers can provide consistent results, and the data pool generated by standardized testing can support the formulation of design assumptions. [ABSTRACT FROM AUTHOR]

Numerical simulation is often used in the design of aircraft structural components subjected to bird-strike loads. To verify the numerical method, a test of bird striking was performed on honeycomb-based sandwich panels made from 3003 aluminum honeycomb and 2024-T3 aluminum skin. The dynamic responses of displacement and strain on the rear skin of the sandwich panel during bird striking were measured using strain gauges and a laser sensor, respectively. A numerical model of bird striking was developed with a nonlinear, finite-element program. A coupling smooth particle hydrodynamics-finite-element analysis algorithm was used to simulate the interaction of the impacting contact between the bird and the target. The numerical simulation results were compared with the tests, and they are in good agreement, which validated the reasonableness of the numerical model established in the present paper. This shows the potential of using the FEM in simulating the dynamic response of aircraft structural components in bird-strike events. [ABSTRACT FROM AUTHOR]

Sandwich panels composed of glass fiber-reinforced polymer (GFRP) skins and low-density polyurethane core are investigated for potential structural applications such as lightweight insulated roofing or cladding systems. Ten panels, including three control specimens, were tested under high-cycle fatigue at maximum load levels of 45-70% of the ultimate static load. Fatigue tests were carried out to failure, thereby enabling the development of the complete fatigue life () curve and stiffness degradation. Digital imaging correlation was used to map shear deformations and showed that shear contributes about 90% of the deflection. Both static and fatigue failure modes were due to core shear failure. The study showed that fatigue threshold was 37% of the ultimate static capacity, and that to sustain at least 2 million cycles, service load should be limited to 45% of ultimate. The maximum design service live and snow loads, as well as wind load based on the most critical conditions in Canada, were all below the fatigue threshold of the panel. The panels had a strength safety factor of 2.1 relative to the factored maximum design live and snow load, and 6.5 relative to the factored maximum wind load. Deflection limits may govern for some service load conditions, but is not critical when only wind load considered. Stiffness degradation reached a maximum of 15-20%, but residual deflections upon unloading were insignificant. [ABSTRACT FROM AUTHOR]

The concept, design, and experimental validation of the new Avançon Bridge in Bex, Switzerland, are described. The lightweight glass fiber-reinforced polymer (GFRP) sandwich bridge deck adhesively bonded to steel girders, reduced the traffic disruption period by approximately 40 days or 80% compared to a cast-in-place concrete bridge, and also enabled the bridge to be widened to two lanes. The semi-integral bridge concept allows the application of a continuous asphalt layer across the abutments without expansion joints and thus facilitates and reduces maintenance. The GFRP sandwich deck with structural balsa core fulfils all the requirements concerning serviceability, ultimate limit state, and fatigue. The bridge deck dimensions significantly depended on the selected and applied design recommendation. In the case of the Avançon Bridge, the German and British recommendations provided the most conservative sets of material factors, the Dutch recommendation specified the least conservative, with the Eurocomp recommendation lying somewhere in between. In particular, the selected material factor applied to stiffness influenced the deck composition and material consumption. [ABSTRACT FROM AUTHOR]

This paper investigates the contribution of unreinforced masonry infill panels to the robustness of composite steel framed buildings subject to sudden column loss. A previously developed multilevel robustness assessment approach is extended and used to establish the system pseudostatic capacity, which determines the level of gravity loading that could be sustained under sudden column loss without exceeding the system ductility limit. The infill panels are modeled according to the ultimate failure mode and confinement caused by the frame, where a simplified approach is proposed based on extracting the infill panel contribution in isolation of the surrounding frame. The developed modeling approach is applied to a 7-story building, where it is shown that accounting for infill panels can increase the structural resistance to sudden column loss significantly, thus avoiding disproportionate collapse in most cases. [ABSTRACT FROM AUTHOR]

Modeling and numerical simulation of foam sandwich panels subjected to impulsive loading are presented. The sandwich panels consist of steel sheets at front and back with two varieties of foam cores in between. Stiffeners are provided at the back sheet for improved response. The dynamic response of the stiffened steel plate (SSP), sandwich foam panel (SFP), and stiffened sandwich foam panel (SSFP) are compared. The foam material modeling accounts for elastic-plastic behavior with volumetric hardening. The finite element-based numerical simulation for dynamic analysis is performed using a combination of shell and solid elements for sheets and foam, respectively. Central point displacements caused from the impulsive load of peak pressure of 0.7 MPa and lasting for 15 ms applied uniformly to the sandwich panels are studied. The analysis is carried out with an objective of understanding the effects of foam thickness, type of foam, and the stiffener configurations. The results obtained indicate that the SSFP considerably increase the resistance to impulsive loading compared with the SSP and SFP. [ABSTRACT FROM AUTHOR]

Glass fiber-reinforced polymer (GFRP) shear connectors provide much reduced thermal bridging in insulated concrete sandwich panels compared to steel connectors. In this study, 50 specimens with dimensions of representing segments of a precast sandwich wall comprising two concrete wythes and a concrete stud surrounded by insulation foam have been tested in a double-shear configuration. Three types of GFRP connectors produced from available sand-coated and threaded rods were tested and compared to conventional steel and polymer connectors. GFRP connector diameters varied from 6 to 13 mm, and spacing varied from 80 to 300 mm. Both circular and rectangular cross sections were examined, along with various end treatments to compare with simple straight embedment. The shear strength of GFRP connectors, including the effect of friction between concrete and foam, ranged from 60 to 112 MPa, significantly higher than polymer connectors but lower than steel connectors. As the connectors bridged a small gab of insulation between concrete wythe and stud, their shear strength was lower than manufacturer-reported values. Varying the size, spacing, cross-section shape, or end treatment of connectors had insignificant effect on their strength. The connectors failed by longitudinal delamination then transverse shear but did not pull out of the concrete wythe. Adhesion bond between concrete and insulation was quite significant and contributed about 28%, but was quite random and variable. A model was developed to predict the strength of connectors and clearly demonstrated the reduction in strength as thickness of insulation layer increases. [ABSTRACT FROM AUTHOR]

The natural stone veneer used to clad sandwich panels needs to be less than 1 cm thick to ensure a lightweight structure. However, diminishing the thickness reduces slab strength, which is important when the stone is to be rough finished. Thus, traditional techniques such as bush-hammering and flaming are unfeasible for these veneers. The main aim of this study was to investigate the possibility of using high pressure waterjet technology for stone veneer finishing. First, the characteristics of the stone were determined (origin, petrography chemistry, strength). Suitable combinations of waterjet operating parameters (pressure, traverse speed, distance between successive passes) were then tested to determine optimal results in terms of both performance and aesthetics. The investigation demonstrated the success of this technique for processing large slabs (), with thickness of just 3 mm, thus also overcoming the problems involved in maneuvering heavy slabs with thickness of more than 2 cm. Surface roughness analysis of the treated stone showed it to compare favorably with competing technologies, with the advantage that waterjet maintains the natural color of the rock. Finally, some economic considerations are discussed. [ABSTRACT FROM AUTHOR]

In this paper, an improved higher-order zigzag theory for vibration of soft core sandwich plates with random material properties is proposed. The theory satisfies the condition of continuity in transverse shear stresses at all the layer interfaces and transverse shear stress free condition at the top and bottom of the plate, including the transverse flexibility effect of the core. The variation of in-plane displacements through thickness is assumed to be cubic while transverse displacement varies quadratically within the core and constant throughout the faces. The core is modeled as a 3D elastic continuum. An efficient C0 finite element in conjunction with a first-order perturbation approach is developed for the implementation of the proposed plate theory in a random environment and is employed to evaluate the second-order statistics of the eigensolutions by modeling lamina material properties as basic random variables. The mean and standard deviations of natural frequencies and their mode shapes are computed and validated with Monte Carlo simulation. [ABSTRACT FROM AUTHOR]

Glass fiber-reinforced polymer (GFRP) materials possess inherently high strength-to-weight ratios, but their effective elastic moduli are low relative to civil engineering (CE) construction materials. While elastic modulus may be comparable to that of some CE materials, the lower shear modulus adversely affects stiffness. As a result, serviceability issues are what govern GFRP deck design in the CE bridge industry. An innovative solution to increase the stiffness of a commercial GFRP reinforced-sinusoidal honeycomb sandwich panel was proposed; this solution would completely replace the GFRP honeycomb core with a hexagonal honeycomb core constructed from commercial steel roof decking. The purpose of this study was to perform small-scale tests to characterize the steel hexagonal honeycomb core equivalent elastic moduli in an effort to simplify the modeling of the core. The steel core equivalent moduli experimental results were compared with theoretical hexagonal honeycomb elastic modulus equations from the literature, demonstrating the applicability of the theoretical equations to the steel honeycomb core. Core equivalent elastic modulus equations were then proposed to model and characterize the steel hexagonal honeycomb as applicable to sandwich panel design. The equivalent honeycomb core will enable an efficient sandwich panel stiffness design technique, both for structural analysis methods (i.e., hand calculations) and finite-element analysis procedures. [ABSTRACT FROM AUTHOR]

Precast/prestressed concrete sandwich panels consist of two concrete wythes separated by a rigid insulation foam layer and are generally used as walls or slabs in thermal insulation applications. Commonly used connectors between the two wythes, such as steel trusses or concrete stems, penetrate the insulation layer causing a thermal bridge effect, which reduces thermal efficiency. Glass fiber-reinforced polymer (GFRP) composite shell connectors between the two concrete wythes are used in this research as horizontal shear transfer reinforcement. The design criterion is to establish composite action, in which both wythes resist flexural loads as one unit, while maintaining insulation across the two concrete wythes of the panel. The experiments carried out in this research show that hybrid GFRP/steel reinforced sandwich panels can withstand out-of-plane loads while providing resistance to horizontal shear between the two concrete wythes. An analytical method is developed for modeling the horizontal shear transfer enhancement using a shear flow approach. In addition, a truss model is built, which predicts the panel deflections observed in the experiments with reasonable accuracy. [ABSTRACT FROM AUTHOR]

Currently within the military there is a need for a universal light-weight bridge deck system capable of supporting extreme loads over a wide temperature range. This research presents the development, testing, and analysis of five different fiber-reinforced polymer (FRP) webbed core deck panels. The performance of the FRP webbed decks are compared with an existing aluminum deck and with a baseline balsa core system, which has previously been tested as part of the development of the composite army bridge for the US Army. The study shows that for one-way bending, the FRP webbed core can exceed the shear strength of the baseline balsa core by a factor of 3.2 at a core’s density, which is 28% lighter than the balsa baseline. In addition, weight savings in excess of 30% are shown for using FRP decking in place of conventional aluminum decking. Based on test results and finite-element analysis, the failure modes of the different FRP webbed cores are discussed and design recommendations for FRP webbed core decks are provided. [ABSTRACT FROM AUTHOR]

This paper presents a study on the evaluation of the static performance of a glass fiber-reinforced polymer (GFRP) bridge deck that was installed in O’Fallon Park over Bear Creek west of the City of Denver. The bridge deck has a sandwich panel configuration, consisting of two stiff faces separated by a light-weight honeycomb core. The deck was manufactured using a hand lay-up technique. To assist the preliminary design of the deck, the stiffness and load-carrying capacities of four approximately 330 mm (13 in.) wide GFRP beam specimens were evaluated. The crushing capacity of the panel was also examined by subjecting four 330×305×190 mm (13×12×7.5 in.) specimens to compression tests. The experimental data were analyzed and compared to results obtained from analytical and finite element models, which have been used to enhance the understanding of the experimental observations. The failure of all four beams was caused by the delamination of the top faces. In spite of the scatter of the tests results, the beams showed good shear strengths at the face-to-core interface as compared to similar panels evaluated in prior studies. [ABSTRACT FROM AUTHOR]

The application of fiber-reinforced composites (FRP) is gaining momentum as an alternative material for bridge replacement, repair, and rehabilitation. While a number of states now use FRP, a lack of standards, codes, and performance data for FRP bridge decks has resulted in the use of FRP technology not being widely accepted. This paper presents the performance results, based on acoustic emission (AE), of six full-scale glass FRP bridge deck panels with nominal cross-sectional depths varying from 152 mm (6 in.) to 800 mm (30 in.). The objective was to develop for use during in-service field inspections an AE monitoring strategy that will determine the structural performance of the deck. As such, the characterization of damage, e.g., fiber breakage, matrix cracking, and delamination, was part of the investigated criteria and the contributing factors for identification of a monitoring strategy. Although some factors were determined to be associated with the performance evaluation of the structural integrity of the decks, further investigation is needed. [ABSTRACT FROM AUTHOR]

An exact analytical solution based on the propagator matrix method and a semianalytical solution based on a higher-order mixed approach (displacement and stress interpolation) have been presented in this paper to evaluate the natural frequencies as well as the stress and displacement mode shapes of simply supported, cross-ply laminated and sandwich plates. Continuity of the transverse stresses and displacements has been maintained at the laminae interfaces. Results have been presented for orthotropic plates, symmetric as well as nonsymmetric cross-ply composite and sandwich laminates. Results from the propagator matrix agree well with the published results for frequencies as well as displacement and stress mode shapes. Furthermore, the frequencies and displacement and stress eigenvectors obtained from the proposed layerwise mixed method are in excellent agreement with those obtained by three-dimensional elasticity theory. Results obtained from the present equivalent single layer theory are in good agreement with those obtained from the displacement based higher order methods. The high accuracy of the present methods is further confirmed by comparing the response of a sandwich plate with significantly different layer properties for which the conventional displacement based formulations yield inaccurate solutions. [ABSTRACT FROM AUTHOR]

By considering the total transverse displacement of a sandwich plate as the sum of the displacement due to bending of the plate and that due to shear deformation of the core, a 72 degrees of freedom high precision high order triangular-plate element is developed for the thermal postbuckling analysis of rectangular composite sandwich plates. Due to an uneven thermal expansion coefficient in the two local material directions, the buckling mode of the plate can be changed from one mode to another as the fiber orientation or aspect ratio of the plate is varied. By examining the local minimum of total potential energy of each mode, a clear picture of buckle pattern change is presented. Numerical results show that for a sandwich plate with cross-ply laminated faces, buckle pattern change may occur when the plate has a long narrow shape. However, for sandwich plates with angle-ply laminated faces, the buckling mode is dependent on the fiber orientation and aspect ratio of the plate. The effect of temperature gradient on the postbuckling behavior of the sandwich plate is limited except for angle-ply laminated sandwich plates with fiber angle greater than 70° or less than 20°. [ABSTRACT FROM AUTHOR]

An efficient six-noded triangular element based on refined plate theory is developed for the analysis of sandwich plates with stiff laminated face sheets and it is applied to a free vibration problem in this paper. The plate theory represents parabolic through thickness variation of transverse shear stresses with continuity at the layer interfaces, which introduces discontinuity at these interfaces for the shear strains. It is to be noted that the plate theory requires unknowns at the reference plane only. Moreover, it ensures a shear stress-free condition at the top and bottom surfaces of the plate. Thus, the plate theory has all of the features required for an accurate modeling of laminated sandwich plates. The plate theory suffers from a problem in its finite element implementation since it requires C1 continuity of transverse displacement at the element interfaces. As very few elements based on this plate theory exist and they possess certain disadvantages, an attempt has been made to develop this new element. It has been utilized to study some interesting problems of laminated sandwich plate. [ABSTRACT FROM AUTHOR]

A considerable amount of research studies have demonstrated the capability of metallic sandwich panels in dissipating blast loading energy. Metallic sandwich panels dissipate blast energy through large plastic deformation of the core and plates, making them more effective than a single metallic plate of similar density. This study numerically evaluated the effectiveness of using woven shapes as a new core topology in sandwich panels for resisting blast loads. The results of the proposed woven shapes were compared to honeycomb and folded shapes to examine their effectiveness in blast mitigation. Numerical models were developed using ANSYS Autodyn software and were validated using available data in the literature. Eleven panels were studied: three honeycomb panels, five folded panels, and three woven panels. The effect of changing the front layer's thickness and the back layer's thickness was investigated. A new scenario was investigated where the same sandwich panels were exposed to a second blast load following the first one. Finally, the effect of changing the charge weight was studied where parameter charts for the honeycomb topology, folded topology, and woven topology were developed. The results show that woven shapes achieved the best energy dissipation capability compared to the honeycomb and folded shapes. Moreover, woven shapes achieved less back layer deflection than the folded shapes and more back layer deflection than the honeycomb shapes. [ABSTRACT FROM AUTHOR]

Experimental and analytical studies were conducted to investigate the axial strength and failure modes of sandwich panels with glass fiber reinforced polymer (GFRP) skins and soft polyurethane core. A total of 45 specimens of cross-section and of lengths varying from 500 to 2,400 mm [i.e., slenderness ratio () of 15-70, where is the radius of gyration] were tested concentrically using pin-ends (). The effects of skin thickness and an internal GFRP rib on axial behavior were studied. The study first assessed the level of out-of-straightness and concluded that all specimens generally fall within an acceptable limit of . A model based on sandwich panel theory, accounting for excessive shear deformations of the soft core, was used to predict axial strength at a wide range of and then used in a parametric study. It was shown that short panels with of 15-17 experienced local failure, outwards skin wrinkling in non-ribbed panels, or skin crushing in ribbed panels. Slender panels with of 41-70 experienced global buckling followed by secondary local failure. Panels with intermediate slenderness (17-41) showed mixed failure modes. The load at which local failure governs at low appears to be a constant, independent of , whereas the global buckling load decreases significantly with increasing . Increasing skin thickness appears to be more effective at high whereas increasing core shear modulus appears to be more effective at low . [ABSTRACT FROM AUTHOR]

This paper investigates the cyclic fatigue behavior of sandwich panels composed of glass fiber reinforced polymer (GFRP) skins connected by longitudinal -shape ribs and low-density polyurethane foam core. Eighteen panels with ribs of two different flange widths, including three control static tests, were tested in fatigue under fully reversed loading () and fully unloaded () conditions, to maximum loads () of 20-70% of their ultimate static strength (). Fatigue life curves were established and compared with those of panels without any ribs. It was shown that internal ribs increased static strength and stiffness by 80 and 66%, respectively, but were only beneficial within the low cycle fatigue range. Under of 50% , number of cycles to failure () at was only 6% of at in the ribbed panels. Fatigue failure consistently initiated by flange debonding of the rib from skin. In panels loaded to higher than of their nonribbed counterparts, final shear failure of foam core occurred simultaneously with rib debonding, whereas in panels loaded below this level, additional fatigue life was attained after rib debonding, until core shear failure, but at significantly lower stiffness. To achieve an of 2M cycles, should not exceed 35 and 21% of at and , respectively. A three-dimensional (3D) failure surface (Haigh diagram) was established for the ribbed panels. It predicts fatigue life for a given mean and amplitude loads. [ABSTRACT FROM AUTHOR]

This paper investigates the structural performance of steel-concrete-steel (SCS) sandwich beams interconnected by channel connectors with large interval. Nine simply supported SCS beams with shear span/depth ratio between 1.0 and 5.5 were tested under static load. The contribution of the channel connectors was also studied. All the beams failed because of either tension plate failure in midspan (flexural failure) or tension plate failure in shear span (vertical shear failure). As shear span decreased, failure tended to be governed by shear, whereas for larger shear span, failure was governed by bending. The channel connectors were confirmed to directly affect the vertical shear resistance and ductile performance after critical diagonal cracking. On the basis of the observed failure mode, a mechanical model was developed to predict the ultimate shear resistance of SCS deep beams after critical diagonal cracking. The accuracy of this lower-bound approach was ascertained by comparing with the test results. [ABSTRACT FROM AUTHOR]

A research program was conducted to assess the capability of conventional non-load-bearing insulated precast concrete exterior wall panels to withstand blast loadings. Typical construction details from the tilt-up and prestressed concrete industries were examined. The sensitivity of insulation type, reinforcement, foam thickness, and shear tie type on the flexural resistance was assessed. Forty-two single-span static experiments were conducted on 14 different panel designs. From the results of these experiments, resistance functions and deformation limits for insulated concrete sandwich panels were determined. The resistance functions were used to develop predictive dynamic models for panels subjected to blast demands. The models were found to be accurate in comparison to measurements from four full-scale blast detonations. The findings of the research indicate that both prestressed and non-prestressed insulated concrete wall panels meet current rotational limits defined by the U.S. Army Corps of Engineers for protective structures. Simplified methods for modeling the pressure-deformation characteristics of insulated panels can be used to approximate the peak dynamic deformation and reaction loads. [ABSTRACT FROM AUTHOR]

The aim of this work was to investigate to what extent the performance of a glass fiber-reinforced polymer (GFRP) sandwich slab-bridge with a uniform high-density balsa core could be improved in terms of structural efficiency and weight by using a more complex core assembly. This core consisted of high-density and low-density balsa and a fiber-reinforced polymer (FRP) arch inserted into the balsa high/low density interface. Quasi-static load-bearing experiments on sandwich arch-beams with complex core assemblies under symmetric four-point and asymmetric three-point loading were performed. The FRP arch reduced the force in the upper face sheet in the mid-span region and thus prevented compression failure of the latter, which led to a higher ultimate load. It also contributed to the shear resistance by up to 20% for symmetric loading. The best overall performance in terms of structural efficiency (stiffness and resistance) and weight resulted from a core configuration with a GFRP arch between an upper high-density and lower low-density balsa core. [ABSTRACT FROM AUTHOR]