Corrugated Structural Metal Decking System under Tensile Strength Test

Corrugated metal decking has been widely used in the construction industry for many years due to its benefits towards the sustainability, improve time performance of the projects and environmental aspects. This article includes the investigation of tensile strength and identify the failure behaviour of different corrugated surface profile of the metal decking that innovated for structural slab. Novelty of this research is the discovery of the tensile performance of a cold rolled corrugated metal decking profiles at various points of interest for a composite flooring system. Tensile strength specimen preparation complies with the ASTM E8 Standard. A total of 60 specimens with different thicknesses and different parts of metal deck have been tested by the universal testing machine (UTM). The findings on how Base Metal Thickness (BMT) affects the tensile strength and the unique roll formed of the corrugated metal decking system, with 0.75BMT & 1.00BMT, are discussed and analysed in this article. Results showed that the average tensile strength value for 0.75BMT and 1.00BMT from part A was 592.47MPa and 554.41MPa, respectively, and the metal decking is up to the designed strength and the unique roll forming embossment provides better bonding quality between concrete and steel to be used in the industry.


Introduction
Steel has become an essential material as steel has brought a great deal of advantages to the performance of projects.However, it is also crucial to steel structure's life cycle and environmental aspects.Apart from that, steel structures play an essential role in the construction industry towards sustainability since steel is a durable and recycled material that is highly suitable for construction use [4].Besides, it helps reduce construction waste as steel can be easily melted and then refabricated into new steel products.Buildings that are designed in use of steel to energy efficient and eco-friendly.For example, steel enables the capture of natural light to reduce artificial lighting, which can help reduce energy consumption [16].Some buildings are considered composite construction because of the usage of dissimilar materials, such as steel and concrete, simultaneously.Using composite steel and concrete brings together the key benefits of the two materials.The composite structure carries high concrete compressive strength and 1303 (2024) 012001 IOP Publishing doi:10.1088/1755-1315/1303/1/012001 2 steel tensile strength [16].The EN 1994-1-1:2004 defines a composite slab as a slab where steel sheets function as permanent formwork at the beginning then combine with the hardened concrete to withstand the tension force in the slab [9].Corrugated steel is one of the steels that have been widely used in the construction industry.Corrugated steel has a wavy design and comes in sheets type.Corrugated steel became famous after being invented because of the prefabrication in the factory; lightweight, easily transported, and not much technical skills are needed for workers during the installation [1].Corrugated metal decking is lightweight and modular by design, making it simple to transport and install.The advantages of corrugated metal decking are that it speeds up on-site construction and reduces waste.Steel-concrete composite floor systems are one of the most cost-effective options for multi-story steel buildings because it combines structural efficiency with construction speed.This system used to builtup web steel girders of corrugated floor decking and concrete slabs connected with shear connections that offers greater advantages in building [12].
The wavy design is made through a cold form process in which the steel sheets are flattened first and then pressured with rolling dies until the desired corrugation shape is formed.After the desired shape is formed, the corrugated steel sheets are cut into the desired length [15].The process named as cold form process.
Corrugated steel sheets have a solid strength-to-weight ratio among most construction materials.The metal performs well in water shedding too.Hence, the metal is desirable in roof and facade applications.The corrugated metal provides good rigidity even though with a slim design.The metal is an ideal material to be chosen when it needs extra reinforcement in the specific slab.The addition of the steel decking means that less volume of concrete is needed for the piece of the slab but still maintains the slab's strength.The slab becomes lighter in weight but stronger in strength than the conventional slab [17].
Two main characteristics to meet the 'composite' action between the steel deck and concrete are the mechanical interlock provided by indentations or embossments and the frictional interlock provided by the corrugated shape design [11].Corrugated floor decking has a greater strength than a conventional reinforced concrete slab.It forms composite actions by combining the compressive strength from concrete and flexural strength from the composite beam.In fact, steel and concrete have similar thermal expansion and contraction properties, which are able to work perfectly toward each other.The wavy design of steel decking provides slippage resistance between the surface of both steel and concrete materials.Floor decking differed from another metal decking, such as roof decking, due to high rigidity and flattened floor decking on top and bottom parts, giving a better area for adhesion with the concrete with roll-formed stiffeners.
Three common types of metal decking, re-entrant, trapezoidal, and deep decking have been widely used in the industry.Fig. 1 shows the two popular types of shallow decking, which are re-entrant and trapezoidal shape decks used by most of the mid to high-rise building construction.Re-entrant and trapezoidal decking are so-called shallow decking, and the depth of the deck ranges from 45mm to 90mm for shallow decking systems.The rib spacing has a range from 150mm to 300mm.For deep decking of more than 200mm, it is commonly used for constructing a slim flooring system [10].For this research, innovated metal deck is categorized as a shallow deck (re-entrant) and commonly applied to the short slab span between 3m to 4.5m.Decking with 95mm depth could sustain a slab span with 4.5m length and above without propping.The decking system is used in several spans rather than a singlespan design to maintain its stiffness and strength.
Research shows embossment could enhance the composite slab's effectiveness and strong against deflection [13].Besides, the embossments may have the function of developing interaction forces and resistance at the end and strengthening the adjacent ribs while the incline orientation on the resistivity of slippage is reduced.The embossments also increase the steel sheet's stiffness, hence improving the steel's total slip strength [7].The corrugated steel deck with embossment, as shown in Fig. 1, is part of the metal decking stiffener.However, researchers have yet to discover the strength of the metal embossments for a better understanding of the overall strength of the newly innovated metal decking.In most cases, the exact size of the specimen cut from the steel deck might be different from the American Society for Testing and Materials (ASTM) standard, some might be bigger, and some might be smaller in size than the standard.These are not allowable as stated in the standard.However, according to the standard that will apply in this study, ASTM E8 [2], the thickness of the specimen varies in range, depending on the thickness of samples under any condition that the maximum sample thickness shall not be over 19mm.Obviously, different thicknesses might have a different result on the strength.From the previous study, the size of the rectangular specimen also affects the tensile strength, including ductility and related properties [14].
Studies have found that uniform elongation and post-necking elongation increases when the thickness of the specimen increases [18].Apart from that, when the base metal thickness (BMT) plate decreases ultimate tensile strength of the specimen decreases.On the other hand, the yield strength accuracies decrease when the BMT plate increases [20].The thickness applied to the test specimen in this research ranges between 0.17mm to 2mm.The hypothesis of this research believed that when the thickness increased, the flow stress of grains on the free surface increased, thus resulting in higher strength.However, embossment or stiffened steel plate areas may not comply with this fundamental theory.
The origin effect of the flow stress is associated with the metallic grain size effect.The microstructure size effect can be categorized into grain size and feature size effects.The grain size effect is derived and explained with the Hall-Petch theory.The theory states that a material with a bigger grain size will lead to lesser strength and vice versa.For the grain size effect, the grain size increases with decreasing thickness of the specimen and leads to a decrease in flow stress [11].This is because dislocation is easier when the grain size increases, and less force is needed for deformations, making the specimen easier to fail [5].Fig 2 shows the surface model which used to explain the decreases of flow stress with decreases in thickness.Feature size also significantly affects to the flow stress.By referring to the model, the surface grains are likely to have imperfections compared to the inner grains.This leads to a lower resistance when there is a deformation.In short, when a thickness decreases, the sharing of surface grains increases, hence improving the stress distribution [5].
Fig. 2 Grain distribution in a material section of different material [11].
The aim of this research is to investigate the material properties and tensile behaviour of innovated metal deck.The objectives are as follow:

Embossment
• To obtain material properties of different BMT corrugated metal decking system.
• To obtain the stress strain curves of different BMT corrugated metal decking system.
• To obtain the yielding and ultimate strength of different BMT metal decking system.

Metal Deck Specimens Specification and Test Setup
Fig. 3 shows the specification of the test specimens.The specimens in this study are classified as rectangular tension test specimens.The specimen size is prepared based on the ASTM E8 standard, as shown in table 1. Sheet type standard specimen (200mm in length) and subsize specimen (100mm in length) are chosen in this research.However, the plate type specimen is out of consideration due to the thickness of the specimen did not comply with the standard, whereby the required thickness is a minimum of 5mm [3].Fig. 4 shows the sample labelled A, B, and C on a different part of the metal.The part labelled A was cut according to the sheet-type standard specimen (200mm in length).However, part labelled B and C was cut according to the subsize specimen (100mm in length).Each sample is then labelled according to BMT of 0.75mm and 1.00mm for various sampling locations.Tensile strength test is used to assess the properties of the material.A tension load is applied at a specific rate to the test specimen while it is secured at both ends in a load frame.This causes the specimen to elongate and eventually break.Various quantitative data, including deformation characteristics under different loads, are gathered, and recorded throughout the test.After the test, values for several mechanical characteristics are obtained, including but not limited to Young's modulus, Poisson's ratio, yield strength, ultimate tensile strength, elongation, and reduction area [8].The research aims to achieve a minimum yield stress of at least 350MPa and a tensile stress of 550MPa, in accordance with the design standard requirements.

Metal Deck Specimens Specification and Test Setup
Table 2 and fig.6 show the initial results of one of the sixty tensile test results, named 0.75BMT Specimen 2, obtained from the Bluehill software.Main parameters such as tensile stress at maximum load, young modulus, and tensile stress at yield point were determined from the experiment output.Fig. 7 and Fig. 8 show the results of the stress-strain curve from part A of 0.75mm BMT and 1.00mm BMT metal decking, respectively.A total of 10 metal decks are assessed with three locations individually for each thickness as shown in fig. 4. Hence, a total of 60 specimens are evaluated by the UTM.Most of the curves are focused on stress ranging from 500MPa to 600MPa.From fig. 7, the maximum tensile stress of specimen two does not achieve up to 700MPa.Compared with fig.8, more specimens can achieve at 600MPa, proving that the greater the thickness, the higher the tensile stress can withstand.Fig. 9 and fig. 10 show the stress-strain curve from part B of 0.75mm BMT and 1.00mm BMT metal decking, respectively.Part B is selected from the part with lesser width of the metal deck; hence, the specimens are cut into a smaller size.Hence, the tensile strength has a similar behavior to part A which is that the thicker the metal, the greater the tensile strength.However, the results tested in part B do not show significantly different tensile strengths between the two thicknesses.The highest tensile strength of both metal decking achieved 600MPa.12 show the stress-strain curve from part C of 0.75BMT and 1.00BMT, respectively.Part C is the part that has an embossment design on both metal decking.From the observation of the curve, the yield stress, tensile strength, and elongation change considerably compared to flat specimens from parts A and B. The yield stress is lower than most flat specimens might be due to the thickness in the center of the bulged area being reduced.Apart from that, the results do not clearly prove that the higher tensile strength will be obtained with the presence of embossments, where improvement of metal deck rigidity due to embossments is not so pronounced.Most studies proved that the rigidity is improved when the restoration process is done on the metal decking due to the strain hardening effect.Restoration process for metal deck involves strain hardening or restructuring metallic bonding grain from the metal through pre-heat treatment under control temperature [19].Strain hardening is a process to increase in strength and hardness of the metal due to a mechanical deformation in macrostructure of the metal.3 and table 4 shows the summary tensile stress results at yield (offset 0.2%) of all 60 specimens.Each part of the metal decking is tested with ten specimens & the data is recorded from UTM. Yield stress defines as the point where the specimens start to change shape permanently.In the construction industry, yield stress is commonly used in structural analysis, hence, the values obtained must achieve the minimum requirement of 350MPa based on design standard [6].As yield stress is not easy to be defined through the shape of the stress-strain curve, it is arbitrarily defined at 0.2% plastic strain.From the table, average yield stress from part C of both metal thicknesses is obviously lower if compared with parts A and B due to the embossments on the ribs.The embossment process increased the interaction forces between concrete and metal decking but lowered the strength of the metal.Hence, pre-heated treatment is needed to restructure the macrostructure of the metal in other to strengthen the yield stress.However, material cost could be rise due to heat treatment.The yield stress of parts A and B enabled to achieve the minimum strength requirement various range from 400MPa to 700MPa.6 shows the summary of tensile stress at the maximum point of all 60 specimens.Each part of the metal decking is tested with ten specimens and the data is generated directly from the UTM.Tensile stress defined as ultimate strength which aim to achieve a minimum of 550MPa based on the design standard [6].From the table, the results show that the maximum tensile stress for most specimens fluctuated from the range 450MPa to 700MPa, whereby the average values for all parts are reached the minimum requirement.By comparing the value one by one, the results cannot clearly show that the greater the thickness, the higher the maximum tensile stress.This situation might be due to the difference in thickness of specimens needs to be bigger to have a precise result.Fig. 13 represents the summary of the yield stress chart, which the data were obtained from table 3. The chart of fig. 13 shows that the metal deck of 0.75 BMT has a gradient value of -70.41 of the average downward trendline, whereas 1.00 BMT has an oblique gradient of a trendline with a value of -74.621.It can be concluded that the results of part c in 1.00 BMT have lower yield stress than 0.75 BMT.Apart from that, all the yield stress data obtained from the 1.00 BMT metal deck can be graded as consistency, while the graph of 0.75 BMT was scattered and can be grouped as inconsistency results.The inconsistent result of 0.75 BMT could be attributed to various potential issues, including the inconsistency of the breaking point for the specimens due to natural causes, as shown in fig.14.In addition, consistent result of 1.00 BMT leads to high consistence product strength reliability.Fig. 15 shows the summary of the tensile stress chart where the input data were obtained from table 4. Chart fig.15 shows that the metal deck of 0.75 BMT has a gradient value of -41.06 of the average trendline, whereas 1.00 BMT has an oblique gradient of a trendline with a value of -6.8.Besides, all tensile stress data obtained from the 0.75 BMT metal deck were graded as consistent, while the graph of 1.00 BMT was scattered at part c, grouped as inconsistency tensile stress due to presence of embossments.The inconsistence result of part C could be attributed to various potential issues, including the inconsistency of the breaking point for the specimens due to present of embossments which lead to uneven surface.According to the average value of each part in the metal deck 1.00 BMT; the gradient shows consistency which lead to high product strength reliability.Both are types of fracture where the specimens break into half or pieces due to tension or compression stress loaded on the specimens at the temperature before the melting point.The type of failure can easily be determined depending on the amount of elongation of specimens before fracture.The type of failure in this study is considered as ductile failure.The specimens used in the study are rolled-formed from hot-dipped and zinc-coated steel.From the stressstrain curve obtained, all the specimens undergo the plastic deformation stage, which is the part after the yield point until fracture.This happened when the specimens started to change its shape permanently.Moreover, the elongation of specimens is observed, and most importantly, necking happens before every fracture.Fig. 19 shows the fracture of the specimen.Necking can be observed in the figure.The presence of necking indicates that; the material underwent significant plastic deformation before failure, or flow stress is higher than the hardening work rate.Hence, ductile failure is proven.The fractured part must be within the extensometer and only considered as a complete and correct test, as shown in the figure.This is important for understanding the material's ductility and its ability to withstand applied loads without fracturing which leads to obtain accurate results during test.

Conclusion
In conclusion, the findings of the mechanical properties were obtained, and the type of failure of corrugated metal decking was determined.The result shows that the average yield strength for both 0.75BMT and 1.00BMT is satisfactory.Among both thicknesses, the minimum average yield strength is found in Part C of 1.00BMT, with a value of 386.67MPa, exceeding the expected yield strength of 350MPa.
Moreover, the average tensile stress for the 0.75BMT part A, B, and C is 592.47MPa,558.46MPa, and 510.34MPa.Similarly, for 1.00BMT part A, B, and C, the average tensile stress values are 554.41MPa,510.83MPa, and 540.81MPa, respectively.Hence, the results from 0.75BMT part A, 0.75BMT part B, and 1.00BMT part A proved that the tensile stress of the metal decking is up to the expected result, which is 550MPa.However, 0.75BMT part C, 1.00BMT part B, and 1.00BMT part C failed to obtain the expected tensile stress due to the absence of proper heat treatment for the rolled formed stiffeners and embossment, resulting in a failure to restore the metal's strength.

Necking
Theoretically, the thicker the BMT, resulting in higher strength.Nevertheless, results from 1.00BMT are lower than 0.75BMT, possibly due to the inadequate heat treatment of the rolled-formed stiffeners and embossments similar to 0.75BMT part C, 1.00BMT part B, and 1.00BMT part C.This research found that embossment has the least tensile strength among stiffeners on the rib.Hence, part C has the least tensile strength compared to parts A and B of the metal deck, but it does not compromise the yield strength for construction purposes.However, the design purpose of embossment part C on the metal decking contributes to shear strength in supporting the shear load instead of tensile strength.Hence, the way to solve the problem is to let the metal undergo heat treatment to restructure the mechanical properties of steel like a hot roll I beam.

Fig. 4
Fig. 4 Sampling location of part A, B, C, and labelling.

Fig. 5
Fig.5shows the Universal Testing Machine (UTM) model named Instron 5582.Instron 5582 is attached to the Bluehill operating system, which helps collect and analysed data.It gives a maximum frame of up to 100kN, with different types of specimen fixtures and extensometers.Moreover, the machine also carries out different types of tests, such as flexure, compression, and tension tests in this study.The test fixtures include a 3-point bend setup (for flexure test), platens (for compression test), and wedge grips (for tension test)[8].

Fig. 11
Fig.11and fig.12show the stress-strain curve from part C of 0.75BMT and 1.00BMT, respectively.Part C is the part that has an embossment design on both metal decking.From the observation of the curve, the yield stress, tensile strength, and elongation change considerably compared to flat specimens from parts A and B. The yield stress is lower than most flat specimens might be due to the thickness in the center of the bulged area being reduced.Apart from that, the results do not clearly prove that the higher tensile strength will be obtained with the presence of embossments, where improvement of metal deck rigidity due to embossments is not so pronounced.Most studies proved that the rigidity is improved when the restoration process is done on the metal decking due to the strain hardening effect.Restoration process for metal deck involves strain hardening or restructuring metallic bonding grain from the metal

3. 3 .
Failure Behavior of Metal Decking fig.16, fig.17, and fig.18 are the tested specimens, from various part such as part A, part B, and part C, respectively.The failure types are promising and can be categorized into two types of failures.The failures are ductile failure and brittle failure.

Table 2 .
Sample of result table that obtained after tensile test.

Initial Area at Area Reduction (mm 2 ) Final Area at Area Reduction (mm 2 ) Thickness (mm)
Fig. 6 Sample of stress-strain graph after tensile test.

Table 3 .
Yield stress of each specimen assessed (MPa) for 0.75 BMT.

Table 4 .
Yield stress of each specimen assessed (MPa) for 1.00 BMT.

Table 5 .
Tensile stress at maximum of each specimen tested (MPa) for 0.75 BMT.

Table 6 .
Tensile stress at maximum of each specimen tested (MPa) for 1.00 BMT.