A Comprehensive Flexural Analysis for Sustainable Concrete Structure Reinforced by Embedded Parts

Ningbo Zhongchun High Tech Co., Ltd., Ningbo 315100, China School of Mines, Key Laboratory of Deep Coal Resource Mining of the Ministry of Education, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China School of Civil and Transportation Engineering, Hebei University of Technology, 5340 Xiping Road, Beichen District, Tianjin 300401, China College of Urban and Rural Construction, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China Chongqing University Industrial Technology Research Institute, Chongqing University, Chongqing 400045, China Institute for Smart City of Chongqing University in Liyang, Chongqing University, Chongqing, Jiangsu 213300, China School of Design and Built Environment, Curtin University, Perth, WA 6102, Australia


Introduction
As the construction industry develops rapidly, the mechanical properties of the concrete have attached more attention [1,2]. Consequently, the reinforced concrete (RC) structures have been widely used in constructions with the advantages of high sustainability, excellent mechanical strength, and considerable deformability resistance [3,4]. However, the ordinary RC structures cannot meet the increasing demand of engineering specifically for the formworks in structure nodes [5][6][7]. is phenomenon points to the need for novel RC structures for filling structure nodes' formworks and producing high-quality constructions [8].
e application of sustainable embedded parts in steelconcrete composite structure joints has been used extensively as a promising material [9]. e embedded parts' structure comprising Halfen channel embedded parts and plate embedded parts are raising attention and can be the feasible solutions towards current drawbacks [10]. e embedded parts' structures do not depend on the secondary construction of the ground in constructions with the advantages of the convenient assembly procedure, low cost, and labor [11]. Stout et al. [12] patented a method for making cast-in-place concrete structures to reveal integrally bounded confines in the structure. Stout et al. [13] also explored a void-creating device to be embedded in a concrete structure, aiming at defining a labyrinth of passageways with the concrete structure, which revealed the passage procedure for service parts through the interior parts within the concrete.
At present, drawing, shearing, and seismic resistance are major concerns for embedded parts worldwide. In engineering application, the slot embedded parts, bearing the bending force and shear force in most cases as the joint of the steel-concrete structure [14]. However, few studies have been conducted on the bending-shear test performance of slot embedded parts. Moreover, despite the embedded parts being widely used, there are few standard designs for slot embedded parts.
In this study, a novel coating treatment was conducted upon three kinds of HALFEN channel embedded parts and two kinds of plate embedded parts to reveal the sustainable function. e bending-shear experiments were carried out with different specifications to analyze the ultimate bearing capacity and failure modes. Under the actual test conditions, the theoretical calculation and finite element analysis using ABAQUS were carried out on the flexural and shear test to determine the reliability of the HALFEN channel embedded parts in the practical application. e study can be regarded as a guideline in this research area.

Experimental Study
2.1. Experimental Design. 15 specimens for two types of embedded parts were analyzed comprising A-1, A-2, B-1, B-2, and B-3. e A group was the structure reinforced by embedded plate and the B group means the grooved embedded parts corresponded to three different types of grooved embedded parts. Each batch contains three samples and the loading configurations are constant. Specifically, A-1 and A-2 were each reinforced by a 150 mm × 150 mm × 10 mm and a 150 mm × 150 mm × 20 mm anchor plate separately. Meanwhile, the embedded plate was welded by 4 steel bar anchor legs (200 mm in length and 20 mm in diameter) and the anchor legs were also welded to an I-beam (150 mm) with different distances towards edges (10 mm for A-1 and 20 mm for A-2). For the B group, the specimen was reinforced by HALFEN groove (40 mm width and 22 mm height for B-1, 50 mm width and 30 mm height for B-2, and 52 mm width and 34 mm height for B-3). e groove was weld by 4 anchor legs with a length of 100 mm (overall length of 300 mm). e anchor legs were linked with 5 T bolts on the other side. e concrete specimen sizes were 450 mm × 450 mm × 450 mm (A group) and 600 mm × 400 mm × 300 mm (B group). e design strength of all specimens was C30 and the embedded parts were Q345-type galvanized steel. e surface of the anchor plate was even with the concrete, embedding all anchor legs. e bending or shearing loads were applied to the I beam or T bolt, and the loading eccentricity was 40 mm from the anchor plate plane. e specimen parameters were demonstrated in Table 1.

Sustainable Treatment.
All designed embedded parts experienced coating treatment to guarantee sufficient sustainability in-service lifespan. A self-developed Zn-A1-Mg-RE alloy on a small scale is utilized coating, as shown in Figure 1. is is because the alloy not only exhibits outstanding corrosion resistance but also fills the microcracks in the coating which enhances the mechanical performance. First, pure Zn strip at the content of 99.9% is sprayed onto the surface of embedded parts as a base by a high-velocity spraying gun (HAS-02) cooperated by a CDM system (AS3000) at 200 μm thickness. Later, the Zn-A1-Mg alloys are coated upon the surface of the embedded part with a thickness of 400 μm. e spraying current stands at 140 A, and spraying voltage employs 30 V. e spraying distance keeps at 250 mm and the air pressure is 0.65 MPa.

Loading Parameters.
e 500t servo compression-testing machine is utilized to load the test specimens. Meanwhile, a self-control device is set on the upside of the specimen to prevent the sliding effect on the workbench. e structure diagram of the entire loading system and selfcontrol device are, respectively, shown in Figure 2.
As for the loading procedure, the servo machine first utilized a 0.2 kN/s preload rate till the 10% yield load followed by a recovering process. After the inspection of the loading device and instrument, the servo machine applied uniaxial load at a rate of 0.4 kN/s with 50 mm eccentricity until failure. e loading value, as well as the strain data, was collected automatically by the servo machine and the static strain tester. Especially, both the circumscribed I-beam of plate-type and the circumscribed T-type bolt of slot-type built-in fitting obtained 4 anchor legs using 8 wires to connect with the static strain tester during loading. e loading procedure of plate-type built-in fitting and slot-type built-in fitting separately are illustrated in Figure 3.

Mechanical Properties.
e experimental results are shown in Figure 4. e average failure load of A-1 was 378.73 kN and was 78 kN higher than that of A-2(299.93 kN). e mean loading capacities for the B batch were 89.76 kN for the B-1 sample, 125.34 kN for the B-2 sample, and 105.63 kN for the B-3 sample.

Failure Mode.
e failure modes and surface cracks for all five embedded specimens are denoted in Figure 5.
All the specimens were damaged by the concrete vertebral body with considerable cracks. For the embedded structures, the concrete around the groove began to crack slightly and then gradually expanded. After a specific threshold (98 kN for B-1 and 92 kN for B-2), the cracks on the original extend rapidly and terminally came into failure. Major cracks in the vertical direction on both sides of the middle groove steel were found, the bottom joint was protruded around the T-bolt and the upper part was pulled out due to the exerted force on the edge.

Design Calculation and Analysis of Plate Embedded Parts.
As for the damage characteristics, when the force moment e/z is less than 0.3, the embedded parts are first crushed by concrete with general shear-bearing embedded parts. When the force moment e/z is more than 0.6, the embedded parts are all damaged by the pulled anchor leg. Otherwise, the embedded part failure is caused by the compound effect of crushed concrete or the pulled anchor leg. In this study, the eccentricity is 40 mm, and the vertical distance Z between the anchor legs is 130 mm. erefore, the moment equals 0.3 and the theoretical damage characteristic ought to be a crushing effect to form vertebral body damage, which is consistent with the actual damage characteristics.
According to the experimental study and theoretical analysis of uniformly arranged bending-shear embedded parts with straight anchor legs, the strength of bending-shear embedded parts can be calculated according to the following equation [16,17]:

Advances in Civil Engineering
According to the reliability analysis of embedded parts, the shear strength of embedded parts can be calculated according to equation (2) and the bending strength of embedded parts can be calculated according to equations (3) to (5): where α v symbols the shear strength coefficient of anchor legs, f c is the design value of concrete compressive strength, f y equals the design value of tensile strength of embedded anchor legs, d is the diameter of steel bars, α r means the influence coefficient of the number of anchor legs, A s is the section area for all anchor legs, α a symbols the reduction coefficient of anchor length, α b is the reduction factor of bending deformation of anchor plate which generally equals 1, l a ′ is the actual length of the anchor leg (200), and l a means the anchorage length (600) of tensile anchor legs is usually selected and calculated according to Table 2. By combining the listed formulas, equation (6) is obtained shown as follows: As the embedded parts met the structural requirements and the anchor plate can be considered as nonbending deformation, α b thus equals 1. e embedded parts are equipped with two rows of anchor legs, and α r is taken as 1.
e design value of compressive strength of concrete specimens is 14.3 N/mm 2 , and the design value of tensile strength of embedded anchor legs is 310 N/mm 2 .
As a result, α a � 1/3 and the shear strength coefficient of anchor legs α v is 0.52. e theoretical calculation solution V is 148 kN, which is far lower than the experimental results of A-1 and A-2, meeting the safety considerations.

Practical Calculation and Analysis of Groove Embedded
Parts.
e embedded depth of the anchor leg was shallow, which is less than 150 mm. e failure form of the groove embedded structure was usually concrete cone failure, and the experimental results verified this assumption. According to CEN/TS 1992-4-3:2009 [15], the formula of a failure bearing capacity of the concrete cone is described as [18,19] where N Rk,c is the failure capacity of the concrete cone when a single anchor leg of groove-type embedded part is applied, α s,N , α e,N , and α c,N are the adjacent anchor correction coefficient, boundary effect correction coefficient, and corner effect correction coefficient, respectively, and φ ucr,N is the cracking correction coefficient of concrete, and when noncracking concrete equals to1.4, φ re,N is the shadow of bearing capacity considering the peeling of surface concrete. e formula for calculating the response coefficient is expressed in equation (8). N 0 Rk,c means the standard value of bearing capacity of concrete cone failure reinforced by single anchor legs of groove embedded parts under tension which is calculated as equation (9): where α ch is the correction factor of channel steel to concrete cone less than 1, f ck,cube is the standard value of compressive strength of concrete cube (N/mm 2 ), and h ef is the length of anchor leg of groove embedded parts. According to the listed formulas, h ef is 100 mm, and φ re,N is thus calculated as 1. When the specimen is C30, f ck,cube take 34.9 N/mm 2 and α ch was chosen as 1; then, N 0 Rk,c is calculated as 50.2 kN. e adjacent anchor repair coefficient, boundary effect repair coefficient, and corner effect repair coefficient α s,N ，α e,N ， and α c,N , are 1, 1.1, and 1.2, respectively, according to the actual situation. e concrete is noncracking concrete, and φ ucr,N is 1.4. As a result, N Rk,c is calculated as 102.1 kN, which is in close agreement with the experimental values.

Selection of Materials.
e groove embedded components (B-1, B-2, and B-3) were simulated in finite element analysis consisting of steel plate, groove embedded parts, and concrete structure. e T-type bolt is simplified as a steel plate in modeling as its main function was to transmit force to embedded parts. e steel Poisson's ratio was 0.274, and the elastic modulus was 2.06 * 10 3 MPa.
ere were three constitutive models of concrete which are provided in ABAQUS including the brittle cracking model, dispersive cracking model, and damageplasticity model [20,21]. e plastic damage model of concrete is adopted in this paper because it was able to simulate the mechanical behavior of concrete under  (10) and (11) [22,23]: where E 0 means the initial modulus of elasticity, D 0 is the initial elastic stiffness, D symbols the degraded elastic stiffness, and d is the damaging factor variable within the domain of 0 and 1. e uniaxial tension constitutive relation defined the peak stress f t as 0.35f cu 0.55 and the softening section when the strain exceeds the ultimate strain ε cu . Meanwhile, the ultimate tensile strain and the corresponding residual stress in the tension-softening section of concrete have a great influence on the convergence of the calculation. e residual stress is thus defined as 0.13f t . Other related parameters are selected according to the measured values. e plastic nonlinear model is difficult to converge in the calculation. Considering that plastic deformation hardly occurs in the noncontact parts (concrete and embedded part), this area post minor impact towards test results. erefore, the noncontact region is set as linear elastic material, and the contact part between concrete and embedded parts is defined as plastic material.

Interaction and Boundary Conditions.
e binding constraints were established at the contact areas between the steel plate and the embedded parts. To facilitate the loading, a reference point was set on the upper surface of the steel plate followed by a kinematic coupling procedure. To coincide with the test results, some surface-tosurface contact pairs were set. Specifically, the steel plate with larger stiffness was set as the main surface and the concrete part was set as the slave surface. Moreover, the finite slip formula was utilized to define the finite element contact because the relative displacement between the embedded parts and the concrete may be arbitrary. e tangential and normal behaviors were mainly considered in the contact properties and the Coulomb friction was adopted in the friction model and the friction coefficient was 0.4. e model was placed on the loading table of the press with a clamp on the opposite side of the embedded part. e load was applied smoothly on the bolt to transfer the force to the embedded part. According to the experimental setting, three degrees-of-freedom constraints were applied to the concrete bottom and the displacement constraints were utilized for the steel plate.

Mesh Generation.
In this paper, the 8-node hexahedron reduction integral entity element C3D8R was used in the plastic nonlinearity analysis. e embedded component was in 8 mm mesh size and the concrete unit was 30 mm; the contact interface unit was in 7 mm. Figure 6 is the comparison of displacement load curve measured in the experiment and simulated by the finite element method. e experimental results of the embedded parts were in close agreement with the finite element analysis results. e displacement load-curve comparison obtained by finite element simulation is shown in Figure 7. It can be seen that the groove embedded parts have obvious elastic and plastic stages and are verified with the mechanical bearing capacity in the experiments. Figure 8 demonstrates the concrete stress cloud diagram for the simulated B group specimens. e stress distribution on the upper surface in the finite element analysis was consistent with the damaged area of the concrete vertebral surface in experiments. When the embedded parts were subjected to bending and shearing force, the T-bolt would be pulled on the upper side, and we exert relatively large    compressive pressure on the lower side of the channel. When the displacement occurred upon T-bolt, the anchor leg in concrete would be pulled out slowly. ereby, the punching effect upon the interaction between the anchor leg end and the concrete would increase. According to the stress cloud diagrams, the obvious stress concentration phenomenon was found at the interfaces for all three specimens, which was in agreement with the vertebral destruction caused by concrete in the mechanical experiments. Figure 9 shows the deformation diagrams for the groove embedded parts' reinforced concretes. e displacement load-curve comparison figure obtained by finite element simulation is shown in Figure 10. From the listed figures, the maximum stresses for the simulated samples occurred at the bolt-channel steel interface and the anchor leg end. For the B-1 sample, the maximum stress reached 272.8 MPa and was mainly at the connection between T-type bolts and groove steel. e groove-type embedded part was still in an elastic state, while the maximum stress of concrete stood at 75. 16 MPa at the end of the anchor leg, exceeding the compressive ultimate limit. e B-2 sample obtains the maximum stress of 268 MPa also at the connection surface between T-type bolts and groove steel. Meanwhile, the groove-type embedded parts have not fully kept the plastic state, but the concrete's maximum stress (58.38 MPa) has already reached the compressive limit at the end of anchor legs. For the B-3 specimen, the HALFEN groove's peak stress was simulated as 281.8 MPa at the connection part between channel steel and T-type bolts. Simultaneously, both the embedded parts and the concrete component did not exceed the plastic level threshold. e works can lay the foundation for future artificial intelligence optimization works.   Advances in Civil Engineering

Conclusion
e purpose of the study was to investigate the reliability of sustainable plate embedded parts and grooved embedded parts' reinforced concrete structures. e main conclusions of the study can be summarized as follows: (1) e self-developed Zn-A1-Mg-RE coating enhances the sustainability performance of the embedded parts, which benefits the whole concrete structure of a longer service life span. e plate embedded parts supplied higher bearing capacity and the HALFEN groove with 50 mm width and 30 mm height was the most suitable category in reinforcing works.
(2) e theoretical calculation of failure bearing capacity for both plate embedded parts and grooved embedded parts reinforced concrete structures was consistent with the experimental results. e failure modes for embedded parts' reinforced concrete structures were the destruction of concrete vertebrae with obvious cracks. (3) Based on the finite element analysis of three groove embedded specimens, the concrete at the end of the anchor leg had an obvious stress concentration phenomenon, which was consistent with the phenomenon of vertebral body destruction caused by concrete in the experiment. e finite element simulations were in according to the experimental results and theoretical calculation results.

Data Availability
All data used to support the study are included within the article.

Conflicts of Interest
e authors declare that they have no conflicts of interest.