Sandwich Roof Research Articles

Numerical Simulation Study on Mechanical Bearing Behavior of Arch Steel–Concrete Composite Sandwich Roof

In order to study the mechanical bearing behavior of arched sandwich roof structures, a full combination and independent action mode of concrete sandwich composite panels was constructed using the finite element method, and an arched steel–concrete composite sandwich roof with a span of 18 m was subjected to a numerical simulation test under a full-span vertical uniformly distributed load, with the bearing characteristics of the arched sandwich roof discussed in depth. The results show that the cross-sections of l/16 and l/2 of the elliptical arch sandwich roof are weak sections, and the tensile cracking of concrete appears for the first time in the upper and lower wythes of the elliptical arch sandwich roof, the von Mises stress level of the lower wythe of the l/16 section is higher under the ultimate load, and the roof shows four-part form failure characteristics. With the expansion of the cracking range of the upper and lower concrete wythes of the steel–concrete composite sandwich arch roof, the load–displacement curve of the roof structure does not decrease significantly, and the bearing capacity of the structure is high and the vertical deformation is small. The steel–concrete composite segment at the end of the roof effectively strengthens the edge constraint of the roof and improves the integrity of the sandwich roof. The upper and lower concrete wythes of the sandwich roof show a fully combined action mode in the elastic working stage and, when the concrete cracks, it shows a partial combined action mode.

Comparative Study to Assess the Thermal Behaviour of Sandwich Roof Panels with Coconut Fibre as an Alternative Core Material to Polyurethane

Sandwich panels (modular panels) promote optimal solutions to some major issues prevailing in the construction industry such as increased energy consumption by building elements, excessive disposal of constructional waste and unproductive time spent during construction. Hence, the inclination towards sandwich elements has been increased vastly deviating from conventional building construction materials and methods. However, the potentiality of using locally available natural materials for the development of sandwich panels is a salient sustainable approach that needs to be addressed. This study evaluates the current and potential materials used in modular panels and key properties of sandwich panels including mechanical, thermal insulation, and sound insulation properties. Moreover, various test methods followed, and standards specified to investigate the mechanical, thermal and acoustic insulation properties are also discussed. The possibility of using coconut fibre as a locally available natural alternative core material to polyurethane core of sandwich panels has been evaluated using simulations based on the material properties obtained from literature. The study identifies coconut fibre as a potential alternative core material for sandwich roof panels as it reflects nearly similar thermal behaviour to polyurethane.

Typha as a circular building material.

Innovation towards biobased energy concepts.In 2050, the European Union aims to have created a carbon free and circular society. At the same time nature and biodiversity needs to be restored. For the current energy transition in the built environment this means not only developing solutions that can reduce energy consumption considerably, preferably changing the built environment, who currently is responsible for 40% of total energy consumption worldwide, into an energy producing part of society. This also means that the embodied energy and the environmental impact of solutions used for this major renovation challenge needs to be lowered substantially, or better still, to be transformed into a positive impact.The aim of this paper is to describe the outcomes of a development towards a circular and biobased sandwich panel from Typha. Research is used to make an inventory of the possibilities for realizing a circular sandwich roof element with the use of Cattail (Typha) as a construction and insulation material. It is important to determine what the properties are of the new Cattail sheet material and what preconditions are needed to use Cattail in construction. Currently the industry mainly uses harmful binders, such as aldehydes and isocyanates, these chemicals are heavily polluted These binders cannot be regarded as a circular solution and therefore alternatives had to be found. How can a circular sandwich roof element be made from Cattail and which circular adhesives are important? Finally, it is important to determine what the use of Cattails contributes to the reduction of the amount of carbon and nitrogen. It is possible that a renovation concept can be realized with a negative carbon footprint.

Thermal properties of novel sandwich roof panel made of basalt fiber reinforced plastic material

The design of roof panels faces practical challenges, such as thermal property requirements. In this study, following the function-integrated design concept, a novel Basalt Fiber Reinforced Plastic (BFRP) sandwich roof panel is presented. A series of experiments, together with theoretical and numerical analysis are performed to investigate their thermal performance as roof panels. The main works and results are: (i) According to Calibration Hot Box (CHB) results, for BFPR panel with 70 mm thickness, the heat transfer coefficients of 3 specimens infilled with XPS, PU or Rock wool are 0.55 W·m-2·K-1, 0.40 W·m-2·K-1 and 0.60 W·m-2·K-1 respectively, which well match with theoretical and numerical results. (ii) Analytical model and Finite element (FE) method are used to calculate heat transfer coefficients of BFPR panels with five different thickness (60 mm,70 mm,80 mm,90 mm, 100 mm), which offer choice to adapt to thermal property requirements for different thermal regions defined by the code. (iii)Comparing with some newly developed SIPs in literatures, BFRP STPs have better thermal performance than plywood-faced sandwich and bamboo-wood based shear walls with similar thickness. (iv)According to temperature distribution pattern on BFRP panel surface, thermal bridge was seen occurring at the edge of BFPR square tubes. However, by steady-state analysis, heat flow passing by edge of BFRP square tubes occupies 5.82%–10.17% of that of the total section. The main contributions of this paper thus lie in three aspects: (1) Proposing a novel structural insulated panels (SIPs), utilizing BFPR as face and rib for sandwich structure, and isolation materials as core materials, which are specially designed and manufactured as building roof panels; (2) Thermal properties of the BFRP SIPs are systematically studied, which shows BFRP SIPs have excellent thermal properties with low heat transfer coefficient and thermal bridge effect. (3) Effect of thickness on thermal conductivity is investigated by numerical simulation, and proper thickness of BFRP SIPs are recommended to meet the thermal property requirements for different thermal regions in the code.

Numerical analysis on flexural behaviour of GFRP sandwich roof panel with multilayer core material

In this study, the flexural performance of Glass Fibre Reinforced Polymer (GFRP) sandwich roof panel with multilayer polyurethane foam core was investigated using commercial FEM software ANSYS WORKBENCH. The GFRP sandwich panel is composed of thin GFRP face sheets at top and bottom infilled with Polyurethane (PU) foam core of two different densities. GFRP sandwich panels with different stacking sequences of the multilayer core was considered to determine the best sequence in which the different layers of core material can be laid on top of each other. The optimum panel size was obtained from parametric study conducted with number of GFRP plies and thickness of core as parameters. Alternatively, the flexural behaviour of GFRP sandwich panel with three different web core configurations were also studied, which includes trapezoidal shaped GFRP webs infilled with PU foam (Type 1), rhombus shaped GFRP webs infilled with PU foam (Type 2), and wave shaped GFRP webs infilled with PU foam (Type 3). Based on the finite element analysis, GFRP sandwich panel with Type 3 core configuration (wave shaped GFRP webs infilled with PU foam) with lesser deformation represented a feasible model to be used as a roofing panel for small residential buildings and prefabricated modular constructions.

Validated Simulation of a Sandwich Roof in a Crash Load Case

Validated Simulation of a Sandwich Roof in a Crash Load Case

07.28: Fastening to face sheets of sandwich panels

ABSTRACTIn several applications the need to anchor loads in sandwich panels arises. This is normally done by introducing the load into one face, using mechanical fasteners such as screws or rivets for tensile and shear forces or contact for compression forces. Nowadays the most common example for these applications are fastening of solar cells (PV‐modules) on sandwich roof panels or fastening of additional façade layers on sandwich wall panels.The paper deals with the different possibilities of introducing forces into the panels, covering both flat or lightly profiled faces used for walls and profiled faces used for roofs. Special attention is paid to design, including verification of fastenings, web crippling of profiled faces and effect on global load‐bearing behaviour of the sandwich panels.In a second step, delamination caused by tensile forces is investigated in more detail: Pull‐out failure is generally the acceptable failure mode and can be achieved by keeping a minimum edge distance. But if repeated loads such as wind loads are acting on the fasteners, the governing failure mode tends to be delamination at lower load levels. Small cracks in the bond layer grow until final failure of the connection or even of the complete sandwich panel by reducing the wrinkling strength of the face. To study both, the influence of the edge distance and the effect of repeated loads, experimental tests and numerical investigations were performed. The results are presented and discussed.ECCS TC7 TWG7.9 and CIB W056 are currently working on a document dealing with point and line loads acting on sandwich panels. Fastening to face sheets of sandwich panels is one of several topics. Thus the present paper may be regarded as a position paper, showing the state of the art related to a specific single item of the document and giving additional references related to this topic.

Long-term design of FRP-PUR web-core sandwich structures in building construction

The structural behavior of GFRP-polyurethane (PUR) web-core sandwich structures subjected to sustained loading was investigated. As a basis, a study of the mechanical behavior of rigid PUR foams used as core materials was conducted, with emphasis on creep. The study showed that the foam anisotropy, its density and the loading type applied must be considered to assess the structural performance of the GFRP-PUR web-core sandwich. The influence of creep on the web-core interaction, i.e. on the shear load distribution and local instability phenomena were then analyzed. The effects of applying particular design recommendations on the design were assessed based on the example of a real GFRP-PUR sandwich roof. The design shear resistance of the GFRP webs, their dimensions and governing failure mode significantly depended on the applied recommendation. A design procedure to evaluate the overall shear resistance of the GFRP-PUR core over time, taking into account creep effects, was presented.

NEST HiLo: Investigating lightweight construction and adaptive energy systems

This paper presents research on lightweight construction and smart, integrated and adaptive building systems. The research is focused on addressing challenges related to the building industry at large, including most prominently the improvement of energy efficiency, onsite power generation, and the reduction of the quantity of materials required to build. We introduce four innovations in context of the design of an experimental building (NEST HiLo): a lightweight, unreinforced funicular floor system; a flexibly formed, concrete shell sandwich roof; a soft actuated, adaptive solar facade and an automated, occupant-centred control system. We demonstrate novel structural engineering approaches to compression-only concrete elements and shell design using multi-criteria shape optimisation. We explore a building facade concept, which employs robotic actuators for solar shading and on-site generation. In addition, the operational phase of the building will be used as a living laboratory where occupants' locations and needs for comfort are detected and used for the control of the energy innovations. The research provides insight into design topics that will become increasingly relevant for the evolution of improved lifecycle energy buildings.

Structural Design of the Flexibly Formed, Mesh-Reinforced Concrete Sandwich Shell Roof of NEST HiLo

Structural Design of the Flexibly Formed, Mesh-Reinforced Concrete Sandwich Shell Roof of NEST HiLo

Testing of adhesive joints in sandwich structures

This paper describes the design and the verification chain for sandwich structure using the example of the vehicle sandwich roof. This contains determination of the mechanical characteristics for sandwich core including adhesive, tests of mechanical properties of sandwich specimens and sandwich structure nodes and finally verification of the selected solution on the global sandwich structure (roof segment). Experiments are used for tuning and verification of numerical analyzes suitable for the use on global construction.

Sandwich Roof of the Bus – Fatigue and Strength Tests

Lightweight and safe roof of the bus was solved within the MIT CR: FR-TI4/349 project. Several variants of sandwich roof were tested on samples in a prior period. Several errors of adhesive joints occurred during the production of the bus roof. Methyl methacrylate adhesive was tested with respect to the declared adhesive ability for arbitrary surfaces. Standardised shear test of the adhesive joints were made for tuning of the numerical model. The obtained parameters are used forthe numerical model of sandwich roof segment. Roof segments were loaded by four points bending and experimentally obtained data were compared with the results of numerical simulations. Several specimens were subjected to cyclic loading in order to get approximate fatigue life of tested variants.

Development of the Bus Sandwich Roof Experimental and Numerical Approach

This paper describes the design verification process of a new bus roof. The aim was to obtain a roof with comparable or better mechanical properties and likely dropped weight. The sandwich roof is developed in the framework of the project when properties matching real roof were compared to test samples. Different core materials and faces have been investigated. The experimental results serve to verify the suitability of the proposed FEM modelling for the future use on global structure roof numerical model.

Uncertainty evaluation and implications of spectrum adaption terms in determining the airborne sound insulation in building elements

The paper presents the implications of spectrum adaptation terms in determination of airborne sound insulation characteristics. The work discusses two major aspects pertaining to the usage of spectrum adaptation terms in determining the airborne sound insulation, viz., uncertainty evaluation and applicability to other noise sources. A parametric study correlating the uncertainties in single-number quantities with corresponding value of single-number quantities for sandwich gypsum constructions and heavy weight sandwich facade and roof constructions is presented. The present analytical investigations reveal that expanded uncertainty difference in two frequency ranges 50 Hz to 5 kHz and 100 Hz to 3.15 kHz is observed as 2.8 dB for Ctr adaptation term and 1.6 dB for C-spectrum term.

Instability of thin-walled GFRP webs in cell-core sandwiches under combined bending and shear loads

An analytical investigation of the buckling/wrinkling behavior of GFRP webs in cell-core sandwiches subjected to combined in-plane shear and bending stresses is conducted. Web–core panels are modeled as long orthotropic plates stabilized by a relatively thick layer of elastic foam. The boundary condition of the plate is defined according to the interaction between the webs and face sheets in the presence of the core material by applying a series of numerical analyses using the three-dimensional finite element modeling. Two approaches are adopted to predict the wrinkling behavior. The first is to predict the buckling/wrinkling of webs subjected to combined shear and bending loads using a mixed-mode interaction formula. In the second approach, the wrinkling behavior of web–core panels is treated as a biaxial compression–tension local buckling problem. The developed approaches are applied to predict the wrinkling loads of thin-walled webs in GFRP cell-core sandwich beams designed for the GFRP cell-core sandwich roof of the Novartis Campus Main Gate Building constructed in Switzerland.

Multiscale approach for the design of composite sandwich structures for train application

In the present work a multiscale approach is considered for the design of composite sandwich structures for a roof of railway vehicle. The procedure consists in different steps that start from cost/benefit analysis on materials and their manufacturing process and cycle up to analysis of sub-components and entire structures. Each step is characterized by experimental, theoretical and numerical studies. The design activities herein presented count experimental campaigns able to characterize both the properties of novel sandwich material, manufactured expressly for transportation industry, the sandwich and joint behaviors. Analytical and numerical approaches have been used to validate and optimize the structural layout. Finite element analysis has been also performed on a test article to verify the “new” sandwich roof in regard to structural requirements suggested by European Code.

Structural Concept, Design, and Experimental Verification of a Glass Fiber-Reinforced Polymer Sandwich Roof Structure

This paper reports on the design and construction of a lightweight glass fiber-reinforced polymer roof structure in Basel, Switzerland. The sandwich construction allowed for an integration of static, building physical and architectural functions that enabled the prefabrication of the entire roof in only four lightweight elements that were easily transported to the site and rapidly installed. Cutting of foam blocks with a computerized numerical control machine and adhesive bonding proved to be advantageous procedures for the fabrication of the complex roof shape, without the use of expensive molds. The factor of safety of the design was adjusted during the design process through experimental verification. Although some of the characteristic material properties were overestimated in the preliminary design, the design properties for the final design were higher than for the preliminary design as it was possible to reduce the resistance factors (according to Eurocode format) after testing by a factor of 2.0. Existing design models and test standards to determine material properties proved to be applicable. © 2008 ASCE.

Stiffness of Profiled Sandwich Panel Roof Cladding

This paper deals with a study which was made of the load‐deflection relationships of profiled sandwich panel roof cladding. A series of measurements were made on the cladding loaded by air bags to give a uniform pressure. A theoretical method based on the observed deflection characteristics of the cladding is suggested, which makes it possible to calculate the flexural stiffness and deflection of the cladding in a reasonably simple way. The observed deflection pattern is described together with the results of the tests and the predictions of the theoretical method. A reasonable agreement is demonstrated between the measured and predicted results.

Subcores in cosmic-ray air showers and high transverse momentum

The rate of subcores in cosmic-ray air showers has been measured near sea level with a close-packed 35 m2 array of spark chambers. A large transition effect was observed from wood beams in the original roof. After the first year, the spark chambers were affixed directly to a new styrofoam sandwich roof of thickness 20 cm (2.2 g cm-2) in order to minimise transition effects. The measured rate is 0.038+or-0.01 per shower of size N>or=105 particles for subcores of size n25>or=50, where n25 is the net number of subcore particles within a circle of radius 25 cm. The dependence on subscore size goes approximately as n25-3.4. The higher rates of subcores reported in other experiments are probably due to transition effects. If pt is calculated by assuming subcore production by pi 0's, the authors find no cases of p1>5 GeV/c. The problem of abstracting realistic information from the subcore data in order to test theories of high-energy interactions at 1015 eV is treated. Simulation results that predict significant improvement in data acquisition at higher altitudes are presented.

Deterioration of bond strength in metal-faced sandwich roof panels

Instances involving the delamination of bonded insulated roof panels have been encountered in practice, particularly within agricultural buildings. Attempts have been made to identify the causes of delamination by means of laboratory tests followed by shear strength measurements. Results indicate that temperature and moisture can reduce bond strength, depending on the panel type. Actual tests within a building have confirmed that the bond strength of such panels does decrease with time, possibly due to these factors. It is recommended that more data should be gathered on the likely long-term performance of sandwich core panels.