# Flexural Behavior of the Composite Girder of a Prestressed Segmental UHPC Channel and a Reinforced Conventional Concrete Deck

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

_{2}reduction, and the pollution of air after about four decades of large-scale infrastructure construction with numerous conventional concrete (CC) structures [8]. To reduce the plate self-weight, UHPC was first applied in bridge engineering in China as the void plates in the dividing strip of the Shijingshan cable-stayed bridge in Beijing in 2003 [9]. Then UHPC cover plates for cable channels and sidewalk slabs have been widely adopted in high-speed railways ever since about 2005 [10]. The first two railway UHPC bridges in China are simply supported by precast prestressed T-shape UHPC girders, one located in the Qian-Cao railway line with a span of 20 m built in 2006, and the other one in the Ji-gang railway covering a particular span of 32 m, built in 2008 [11]. Since 2011, the UHPC thin layer (about 45 mm to 60 mm depth) has been used in more than 30 bridges to stiffen the orthotropic steel deck to prevent the fatigue of the steel structure as well as the early damage of the asphalt overlay [12]. The first UHPC highway bridge built in 2015 features four continuously connected spans of 30 m each, which cross over the expressway from Beijing to Zhuhai at K34 + 690 [13]. The first pedestrian bridge is a landscape bridge at Fuzhou University campus, which is an arch bridge, built in 2015 [14]. A significant application of UHPC in Chinese bridge structures in the last years may be the major girder of the No. 5 Nanjing Yangtze River Bridge cable-stayed bridge completed in 2020, which consists of a steel girder-UHPC deck slab with two main spans of 600 m [15].

- (1)
- Precasting the UHPC segments in a factory allows for steam curing and storage for some time, which can complete most of the shrinkage, resulting in a less negative effect of shrinkage.
- (2)
- Each channel segment is not heavy and can be transported to the site and erected to the design position by conventional lorry and hoisting equipment. This can make the transportation process easier and more cost-effective, as shown in Figure 1a.
- (3)
- The segments are cast by matching each other and are assembled together by post-tensioning without wet joints in the site, which can make the construction simple and faster, as shown in Figure 1b.
- (4)
- UHPC has ultra-high compressive strength but cannot play the whole role in the flange with compressive stresses generally [13]; instead, conventional concrete (CC) with a lower compressive strength can be more efficiently used. Moreover, the CC cast in situ for the whole deck slab can improve the integrity of the girder, as shown in Figure 1c.

- (1)
- For full-section segmental UHPC box girders. The integrity and seismic performance of the box girder is improved by further connecting the segmental U-shaped beams through the cast-in-place concrete deck. At the same time, when the bridge fails, the segmental beams will not directly fall off completely due to the failure of the prestressing cables, which strengthens the safety of the structure;
- (2)
- For UHPC-RC box girders. The prefabrication of UHPC girder segments in the factory is more convenient for UHPC to carry out high-temperature and pressurized maintenance to ensure the quality of the girder segments. On-site construction avoids the erection of supports, reduces the interference with the lower traffic and construction costs, and significantly improves the construction efficiency. When the segment is damaged, the bridge can be repaired by replacing the girder segments, which is conducive to the sustainable development of the bridge;
- (3)
- For steel-concrete composite structures. The amount of on-site welding work and the necessity of the anticorrosive coating of steel beams are eliminated. At the same time, it avoids the problems of different temperature gradients and an excessive stiffness difference between the steel beams and concrete slabs caused by changes in the ambient temperature, and it has obvious advantages in terms of the whole life cycle cost and durability. In addition, the UHPC girder has greater stiffness and less deformation during construction, and the combined PSUC-RCCD girder has greater stiffness.

## 2. Experimental Procedures

#### 2.1. Specimens

#### 2.1.1. Parameters

#### 2.1.2. Size and Reinforcement

#### 2.1.3. Fabrication

#### 2.2. Material Properties

^{4}m

^{2}·kg

^{−1}and an SiO

_{2}content of more than 90%. The particle sizes of the quartz sand were less than 0.6 mm, and its mesh size and percentage are shown in Table 2. The polycarboxylate superplasticizer is a CX-8 type with a water reduction of more than 25%, which provides good workability at a low water–binder ratio.

^{2}·kg

^{−1}and an SiO

_{2}content of more than 65%. The particle sizes of the gravel and river sand were less than 5 mm and 0.6 mm, respectively. Other material parameters are the same as those mentioned in the UHPC.

_{c}is the compressive strength, f

_{t0}is the tensile cracking strength, ε

_{t0}is the tensile cracking strain, f

_{t}is the tensile strength, ε

_{t}is the tensile strain, and E

_{c}is the elastic modulus.

_{p}is the cross-sectional area of the steel, f

_{p}is the yield strength, ε

_{pt}is the yield strain, f

_{pu}is the ultimate strength, ε

_{pu}is the ultimate strain, and E

_{p}is the elastic modulus of the steel.

#### 2.3. Test Setup, Instrumentation, and Loading Protocol

#### 2.3.1. Test Setup and Instrumentation

#### 2.3.2. Loading Protocol

## 3. Experimental Results

#### 3.1. Behaviors of the Basic Specimens

#### 3.1.1. Basic Behaviors

#### 3.1.2. Three Phases in the Whole Loading Process

#### Elastic Phase

_{u}(140 kN; P

_{u}denotes the ultimate load), the specimen cracked and the deflection was 9% W

_{u}(3.8 mm; W

_{u}is the ultimate deflection). The elastic phase ended when the first crack was observed in the dry-joint-2 featuring a width of 0.05 mm and a length of 9 cm.

#### Crack Development Phase I

_{u}(200 kN), a second flexural (vertical) crack appeared at joint-3. The corresponding deflection at the mid-span was 13% W

_{u}(5.6 mm). And then the curve showed apparent nonlinearity and the structural stiffness decreased continuously.

_{u}, a horizontal crack measuring 0.05 mm in width and extending to a length of 4.8 cm materialized at the top of joint-2, precisely along the interface connecting the channel-deck. It is essential to note that, at this juncture, no flexural crack had yet developed on the deck slab of the UHPC channel. Subsequently, when the specimen was subjected to a load of 210 kN, equivalent to 53% P

_{u}, a second horizontal crack, with the same dimensions (0.05 mm wide and 9 cm long), appeared at the interface of joint-3.

#### Crack Development Phase II

_{u}(360 kN), a second crack also reached the deck. The crack width was enlarged to 6.0 mm. The deflection of the specimen was 73% W

_{u}(32.0 mm).

_{u}(380 kN, point C), in the specimen, the stress increasement of the prestressing strands was 446.4 MPa. The total stresses in prestressing strands reached 1536.4 MPa, exceeding the yield strength of 1520 MPa. At this time, the deflections of the specimen were 37.2 mm. The maximum crack width of the specimen reached 9 mm.

#### Failure Phase

_{u}in this study, it is 395 kN and 400 kN for basic girders, respectively.

_{u}at the mid-span of the basic girder was 43.4 mm and 45.6 mm, respectively. They are about 1/80 of the effective spans of the specimens. And the stresses in the prestressing strands reached 1585 MPa and 1599 MPa, respectively.

#### 3.2. Parametric Analysis

#### 3.2.1. Segment Number

#### Load-Deflection Curve of Group 1-1 and Group 1-2

#### Crack Pattern of Group 1-1 and Group 1-2

_{u}(140 kN), while the cracking load of PSUC-RCCD-1 was 59% P

_{u}(240 kN).

_{u}(170 kN) for PSUC-RCCD-5(1), while the flexural crack was only developed to about a quarter depth of the specimen, far away from the top of the joint.

_{u}(360 kN), much higher than the load in the semi-segmental girder because the horizontal crack can only be created after the flexural crack extends to the interface, as illustrated in Figure 10.

#### 3.2.2. Deck Material

#### Load-Deflection Curves of Group 2-1 and Group 2-2

#### Crack Pattern of Group 2-1 and Group 2-2

## 4. Calculation Methods for Cracking Moments and Flexural Capacity

#### 4.1. For PSUC-RCCD Composite Girder

#### 4.1.1. Cracking Moments

_{c-CC}/E

_{c-UHPC}, as shown in Figure 14.

#### Dry-Joint Section

_{p}) in the section disappears in the range of the tensile zone (y

_{cr}). That is, the cracking moment (M

_{cr-seg}) equals the decompression moment (M

_{0}), as expressed in Equation (1).

_{cr-seg}= cracking moments of the semi-segmental section; M

_{0}= decompression moment; σ

_{p}= precompression stress; I

_{cr}= moment of inertia of the cracking cross-section; y

_{cr}= range of the tensile zone.

#### Integral Section

_{0}) plus the cracking moment of the UHPC channel beam, M

_{cr-UHPC}, as shown in Figure 16, which is expressed in Equations (2) and (3).

_{cr-int}= cracking moments of the integral section; M

_{cr-UHPC}= cracking moment of the UHPC channel beam; f

_{t}= tensile strength of the UHPC.

#### 4.1.2. Flexural Capacity

#### Dry-Joint Section

_{c}) is within the web when the girder reaches its failure point, the strain and stress distribution are illustrated in Figure 17b and Figure 17c, respectively.

_{c}.

_{u,seg}of a dry-joint section was established by maintaining force equilibrium within the section, which is demonstrated in Figure 17e. In this representation, concentrated forces are employed to represent the compressive strains in the compression zone, while tensile forces exclusively originate from the prestressing forces.

_{c}) first.

_{c}is within the flange section, then, an equation can be expressed as Equation (4), from which the x

_{c}can be obtained. For an x

_{c}less than the value of the flange depth, i.e., x

_{c}≤ h

_{f}′, it indicates the correctness of the assumption.

_{c}= the compressive strength of CC or UHPC; b

_{f}′ = the width of the deck slab; x

_{c}= the neutral axis depth; f

_{p}= the yield strength of the prestressing strand; A

_{p}= the cross-sectional area of the prestressing strand.

_{u,seg}, the flexural capacity, can be correspondingly obtained using Equation (5).

_{u,seg}= the flexural capacity of the semi-segmental section; b

_{f}= the width of the UHPC bottom; h

_{p}= the height of the prestressing strand to the top slab edge.

_{c}from Equation (4) is larger than the flange depth, i.e., x

_{c}> h

_{f}′, the neutral axis is in the web, as indicated in Figure 17. The x

_{c}should be solved again by Equation (6)

_{c}= the stress at the joint; h

_{f}′ = the height of the deck slab; b

_{w}= the sum of web thickness.

_{u,seg}can then be calculated using Equation (7)

#### Integral Section

_{t}, where k is a reduction factor to consider the real stress of UHPC. From tests, it was found that when the girder failed, the strain of the prestressing strand was 0.0052, much larger than the final tensile strain of the UHPC (0.0027), indicating that the stress of UHPC had entered into the softening branch in the stress-strain relationship curve, i.e., the stress was smaller than the tensile strength f

_{t}and should be a multiple of a factor smaller than 1.0. The reduction factor k is taken as 0.25 by referring to the suggestion in the literature [29] through the regression analysis of the experimental data.

_{u,int}) of an integral section involves the establishment of force equilibrium within the section, as depicted in Figure 18d. Analogous to the procedure employed in calculating the flexural strength of a dry-joint segment, evaluating the flexural capacity of an integral section necessitates the consideration of two scenarios regarding the location of the neutral axis.

_{c}≤ h

_{f}′, the M

_{u,int}can be obtained using Equations (8) and (9).

_{u,int}= the flexural capacity of the integral section; x

_{t}= the height of the tension zone; k = the reduction factor of f

_{t}; h

_{f}= the height of the UHPC bottom.

_{c}> h

_{f}′, the M

_{u,int}can be obtained using Equations (10) and (11).

#### 4.2. For the P-UHPC Girder

#### 4.3. Verification of the Calculating Methods

#### 4.3.1. Verification of the Calculating Methods for the Cracking Moment

_{c}is located in the UHPC webs, while Equations (2) and (3) is used for PSUC-RCCD-1 and P-UHPC-1, in which the x

_{c}is located in UHPC webs.

#### 4.3.2. Verification and Discussion of the Calculation Methods for Flexural Capacity

#### Verification

_{c}is located in RCCD slabs; while for the P-UHPC-5, Equation (5) is used because its x

_{c}is located in the UHPC slab; in addition, Equations (10) and (8) are used for PSUC-RCCD-1 and P-UHPC-1, respectively, because the x

_{c}is located in the web in the former, while it is located in the slab in the latter.

_{u.cal}), comprising both M

_{u,seg}and M

_{u,int}, and experimental values (M

_{u.exp}) for all specimens consistently fall within a 15% margin of error. The mean ratio of calculated to experimental values across all specimens is 0.90, with a standard deviation of less than 0.05. This indicates that the approach employed for determining the flexural capacity of these derived specimens exhibits a commendable level of accuracy, making it a reliable approach for calculating PSUC-RCCD and P-UHPC girders.

#### Discussion

_{u,φ}= cracking moments of a semi-segmental section calculated by the resistance factor; φ = the resistance factor.

## 5. Conclusions

- (1)
- All five specimens behaved similarly, no matter whether the channel beams were segmental or integral or whether the deck slabs were CC or UHPC materials. The entire loading process can be classified into the elastic phase, the cracks development phase, and the failure phase. The segment number and the concrete material property of the deck slab have no significant impact on the flexural behavior of the composite girders, indicating that the PSUC-RCCD composite girders can be used in bridge superstructures.
- (2)
- The dry-joint in the PSUC-RCCD girders does not greatly reduce the flexural capacity of the section, but it does significantly decrease the cracking capacity. The test results indicate that the flexural capacity of semi-segmental girders is 0.96~0.98 times that of the integral girders, but the semi-segmental girders (section) are much lower than those of integral girders (section); the former is only 0.58~0.60 of the latter. This is because of the “bridging effect” of the steel fibers in the integral girders, which makes the specimens crack later, but for the ultimate capacity, the contribution of the tensile stresses in the UHPC is limited because the steel fibers are constantly being pulled out. Therefore, the low cracking moment at the dry-joint section should be paid attention to in practice. To add epoxy to the dry-joints may improve the cracking moment, but the durability of the prestressing strands in them should still be carefully considered in the design.
- (3)
- For both semi-segmental and integral girders, reducing the strength of the deck slab by changing the material from UHPC to CC does not significantly affect their flexural behaviors. Their load-deflection curves are almost overlapped. The cracking moments as well as the flexural capacity of the specimens with a UHPC deck are 1.04~1.15 and 1.02~1.04 times those in the specimens with a CC deck, which means the UHPC material in the deck slab could not be fully utilized, and it is suitable to employ CC in the deck slab to form a PSUC-RCCD to achieve a structurally efficient and economical solution.
- (4)
- Based on the findings of the present experimental study, calculation methods for the cracking moments and flexural capacity of semi-segmental and integral sections in PSUC-RCCD and P-UHPC girders have hereby been developed. These calculated results align perfectly with the test findings. The present discussion further suggests that the recommended resistance factor of 0.85 in certain design codes underestimates the flexural capacity of the semi-segmental girders in this paper, as they are not entirely composed of segments but are semi-segmental in nature. In the initial design phase, one can estimate the flexural strength of the dry-joint segment by calculating it as 0.95 times that of the integral section’s capacity using a resistance factor in reverse.

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## References

- Mishra, O.; Singh, S.P. An overview of microstructural and material properties of ultra-high-performance concrete. J. Sustain. Cem. Mater.
**2019**, 8, 97–143. [Google Scholar] [CrossRef] - Mishra, S.; Mistry, R. Reviewing some properties of ultra high performance concrete. Int. J. Eng. Res. Technol.
**2020**, 6, 108–121. [Google Scholar] [CrossRef] - Larsen, I.L.; Thorstensen, R.T. The influence of steel fibres on compressive and tensile strength of ultra high performance concrete: A review. Constr. Build. Mater.
**2020**, 256, 119459. [Google Scholar] [CrossRef] - Sharma, R.; Jang, J.G.; Bansal, P.P. A comprehensive review on effects of mineral admixtures and fibers on engineering properties of ultra-high-performance concrete. J. Build. Eng.
**2022**, 45, 103314. [Google Scholar] [CrossRef] - Mostafa, S.A.; Faried, A.S.; Farghali, A.A.; EL-Deeb, M.M.; Tawfik, T.A.; Majer, S.; Abd Elrahman, M. Influence of Nanoparticles from Waste Materials on Mechanical Properties, Durability and Microstructure of UHPC. Materials
**2020**, 13, 4530. [Google Scholar] [CrossRef] [PubMed] - Zhou, M.; Lu, W.; Song, J.; Lee, G.C. Application of Ultra-High Performance Concrete in bridge engineering. Constr. Build. Mater.
**2018**, 186, 1256–1267. [Google Scholar] [CrossRef] - Graybeal, B.A.; Brühwiler, E.; Kim, B.S.; Toutlemonde, F. International Perspective on UHPC in Bridge Engineering. J. Bridge Eng.
**2020**, 25, 04020094. [Google Scholar] [CrossRef] - Rahman, M.; McQuaker, T. Application of Ultra-High Performance Concrete in Bridge Engineering in China. In Proceedings of the First International Interactive Symposium on UHPC 2016, Des Moines, IA, USA, 18–20 July 2016; pp. 1–8. [Google Scholar] [CrossRef]
- Zheng, W.; Lv, X. Literature review of reactive powder concrete. J. Build. Struct.
**2015**, 36, 44–58. (In Chinese) [Google Scholar] [CrossRef] - Yan, P.Y. Application of UHPC in China. In Proceedings of the 1st International Symposium of ACF on Ultra High Performance Concrete, Kolkata, India, 7 October 2015; pp. 79–82. [Google Scholar]
- Shuping, G. Application of RPC in Railway prestressed prefabricated bridge. Ready-Mix. Concr.
**2007**, 3, 19–21. [Google Scholar] - Shao, X.; Yi, D.; Huang, Z.; Zhao, H.; Chen, B.; Liu, M. Basic Performance of the Composite Deck System Composed of Orthotropic Steel Deck and Ultrathin RPC Layer. J. Bridge Eng.
**2013**, 18, 417–428. [Google Scholar] [CrossRef] - Su, J.; Ma, X.; Chen, B.; Sennah, K. Full-scale bending test and parametric study on a 30-m span prestressed ultra-high performance concrete box girder. Adv. Struct. Eng.
**2020**, 23, 1276–1289. [Google Scholar] [CrossRef] - Chen, B.C.; Huang, Q.W.; Wang, Y.Y.; Guo, B.; Luo, X.; Jiang, S.H. Design and construction of the first Ultra-high Performance Concrete (UHPC) arch bridge in China. J. China Foreign Highw.
**2016**, 36, 67–71. (In Chinese) [Google Scholar] [CrossRef] - Wang, Y.; Shao, X.; Cao, J. Experimental Study on Basic Performances of Reinforced UHPC Bridge Deck with Coarse Aggregates. J. Bridge Eng.
**2019**, 24, 04019119. [Google Scholar] [CrossRef] - Voo, Y.L.; Foster, S.J.; Voo, C.C. Ultrahigh-performance concrete segmental bridge technology: Toward sustainable bridge construction. J. Bridge Eng.
**2015**, 20, B5014001. [Google Scholar] [CrossRef] - Voo, Y.L.; Hafezolghorani, M.; Foster, S.J. Application of Ultra—High Performance Fiber Reinforced Concrete Technology for Present and Future. In Proceedings of the 2nd International Conference on UHPC Materials and Structures, Fuzhou, China, 7–10 November 2018; pp. 6–20. [Google Scholar]
- Dadmand, B.; Pourbaba, M.; Sadaghian, H.; Mirmiran, A. Effectiveness of steel fibers in ultra-high-performance fiber-reinforced concrete construction. Adv. Concr. Constr.
**2020**, 10, 195–209. [Google Scholar] [CrossRef] - Makhbal, T.O.; Han, S.M.; Kim, D.O. Flexural behavior of ultra high performance fiber reinforced concrete 50 m composite box girder. In Proceedings of the 2nd International Conference on UHPC Materials and Structures, Fuzhou, China, 7–10 November 2018; pp. 777–790. [Google Scholar]
- Lee, S.J.; Makhbal, T.O.; Kim, S.T.; Han, S.M. Flexural Behavior of Segmental U-Girder and Composite U-Girder Using Ultra High Performance Concrete. J. Korean Recycl. Constr. Resour. Inst.
**2017**, 5, 290–297. [Google Scholar] [CrossRef] - Chen, Y.C.; Zhou, J.L.; Guo, F.Z.; Chen, B.C.; Nuti, C. Experimental Study on the Flexural Behaviors of Prestressed Segmental Ultra–High–Performance Concrete Channels and Reinforced Conventional Concrete Deck Composite Girders. Buildings
**2023**, 13, 1841. [Google Scholar] [CrossRef] - Buyukozturk, O.; Bakhoum, M.M.; Michael Beattie, S. Shear behavior of joints in precast concrete segmental bridges. J. Struct. Eng.
**1990**, 116, 3380–3401. [Google Scholar] [CrossRef] - Ahmed, G.H.; Aziz, O.Q. Stresses, deformations and damages of various joints in precast concrete segmental box girder bridges subjected to direct shear loading. Aziz. Eng. Struct.
**2020**, 206, 110151. [Google Scholar] [CrossRef] - GB/T 31387-2015; Reactive Powder Concrete. Standards Press of China: Beijing, China, 2015. (In Chinese)
- SIA 2052:201X; Construction, Recommendation: Ultra-High Performance Fiber Reinforced Cement-Based Composites (UHPFRC). EPFL-Swiss Federal Institute of Technology: Lausanne, Switzerland, 2016.
- 50081-2002; Standard for Method of Mechanical Properties on Ordinary Concrete. Standards Press of China: Beijing, China, 2002. (In Chinese)
- GB/T 228.1-2010; Metallic Materials—Tensile Testing—Part 1: Method of Test at Room Temperature. Standards Press of China: Beijing, China, 2010. (In Chinese)
- Herrera, A.; Baby, F.; Marchand, P.; Toutlemonde, F. UHPFRC direct shear characterization applied to web-flange shear design of T-Shaped Girders. In Proceedings of the AFGC-ACI-Fib-RILEM Int. Symposium on Ultra-High Performance Fibre-Reinforced Concrete (UHPFRC 2017), Montpellier, France, 2–4 October 2017; pp. 431–440. [Google Scholar]
- Li, L. Mechanical Behavior and Design Method for Reactive Powder Concrete Beams. Ph.D. Thesis, College of Civil Engineering, Harbin Institute of Technology, Harbin, China, 2010. (In Chinese). [Google Scholar]
- LRFDUS-6; AASHTO LRFD Bridge Design Specifications. American Association of State Highway and Transportation Officials: Washington, DC, USA, 2012.
- DBJ 43/T 325-2017; Technical Specification for Reactive Powder Concrete Structures. China Architecture & Building Press: Beijing, China, 2017. (In Chinese)

**Figure 1.**PSUC-RCCD Composite Bridge Construction Process. (

**a**) Precast UHPC segment (section 1-1); (

**b**) Assembled into a UHPC channel beam (section 1-1); (

**c**) Erection of the UHPC channel beam (section 1-1); (

**d**) Cast in situ for the whole deck slab (section 2-2); (

**e**) section 1-1; (

**f**) section 2-2.

**Figure 2.**Specimen elevation (unit: mm). (

**a**) PSUC-RCCD-5(1), PSUC-RCCD-5(2) and P-UHPC-5; (

**b**) PSUC-RCCD-1 and P-UHPC-1.

**Figure 4.**Specimen elevation (unit: mm). (

**a**) PSUC-RCCD-5(1), PSUC-RCCD-5(2) and P-UHPC-5; (

**b**) PSUC-RCCD-1 and P-UHPC-1; (

**c**) Test set-up.

**Figure 6.**Concrete strain distribution along the depth of the girder. (

**a**) PSUC-RCCD-5(1); (

**b**) PSUC-RCCD-5(2); (

**c**) PSUC-RCCD-1; (

**d**) P-UHPC-5; (

**e**) P-UHPC-1.

**Figure 7.**Schematic diagram of the PSUC-RCCD-5(1) and PSUC-RCCD-5(2) specimens in an ultimate load. (

**a**) PSUC-RCCD-5(1) crack pattern in a 395 kN load; (

**b**) PSUC-RCCD-5(2) crack pattern in a 400 kN load.

**Figure 11.**P-UHPC composite box girder crack pattern. (

**a**) P-UHPC-5 crack pattern at a 410 kN load; (

**b**) P-UHPC-1 crack pattern at a 420 kN load.

**Figure 13.**Deck slab of the specimen at the failure load. (

**a**) RCCD slab of PSUC-RCCD-5(1) at 395 kN; (

**b**) UHPC slab of P-UHPC-5 at 410 kN.

**Figure 14.**Equivalent cross-section for the cracking moment. (

**a**) Cross-section; (

**b**) Equivalent cross-section.

**Figure 15.**Strain and stress distribution in the dry-joint section at the cracking state. (

**a**) Cross-section; (

**b**) Strain; (

**c**) Stress.

**Figure 16.**Strain and stress distribution in the integral section at the cracking state. (

**a**) Cross-section; (

**b**) Strain; (

**c**) Stress.

**Figure 17.**Diagram for the flexural capacity of the semi-segmental girder. (

**a**) Cross-section; (

**b**) Strains distribution; (

**c**) Stresses distribution; (

**d**) Simplified stress distribution; (

**e**) Internal forces.

**Figure 18.**Diagram for the flexural capacity of the integral girder. (

**a**) Strains distribution; (

**b**) Stresses distribution; (

**c**) Simplified stress distribution; (

**d**) Internal forces.

Girder Notations | Segment Number | Deck Slab Material |
---|---|---|

PSUC-RCCD-5(1) | 5 | CC |

PSUC-RCCD-5(2) | 5 | CC |

PSUC-RCCD-1 | 1 | CC |

P-UHPC-5 | 5 | UHPC |

P-UHPC-1 | 1 | UHPC |

Cement | Silica Fume | Quartz Sand | Quartz Powder | Superplasticizer | Water | ||
---|---|---|---|---|---|---|---|

Coarse | Medium | Fine | |||||

40–70 | 20–40 | 10–20 | |||||

1.00 | 0.30 | 0.14 | 0.41 | 0.53 | 0.09 | 0.02 | 0.23 |

Cement | Flyash | Gravel | River Sand | Superplasticizer | Water |
---|---|---|---|---|---|

1.00 | 0.15 | 2.23 | 1.43 | 0.02 | 0.32 |

Material | f_{c}/MPa | f_{t0}/MPa | ε_{t0}/με | f_{t}/MPa | ε_{t}/με | E_{c}/GPa |
---|---|---|---|---|---|---|

UHPC | 134.2 | 5.7 | 131.2 | 8.7 | 2736.4 | 44.9 |

CC | 53.1 | - | - | 3.8 | - | 38.4 |

Material | d /mm | A_{p}/mm ^{2} | f_{p}/MPa | ε_{pt}/με | f_{pu}/MPa | ε_{pu}/με | E_{p}/GPa |
---|---|---|---|---|---|---|---|

Prestressing strand | 15.2 | 139.0 | 1521 | 0.0108 | 1887 | 0.0639 | 1.94 × 10^{5} |

Steel reinforcement | 6.0 | 28.3 | 400 | 0.0020 | 570 | 0.0260 | 2.02 × 10^{5} |

Group | Parameters: Segment Number | Group | Parameters: Deck Material |
---|---|---|---|

Group 1-1 | PSUC-RCCD-5(1) | Group 2-1 | PSUC-RCCD-5(1) |

PSUC-RCCD-1 | P-UHPC-5 | ||

Group 1-2 | P-UHPC-5 | Group 2-2 | PSUC-RCCD-1 |

P-UHPC-1 | P-UHPC-1 |

Girder Notations | M_{cr.exp} (kN·m) | M_{cr.cal} (kN·m) | M_{cr.cal}/M_{cr.exp} |
---|---|---|---|

PSUC-RCCD-5(1) | 84 | 83 | 0.99 |

PSUC-RCCD-5(2) | 84 | 83 | 0.99 |

PSUC-RCCD-1 | 144 | 142 | 0.99 |

P-UHPC-5 | 90 | 84 | 0.93 |

P-UHPC-1 | 150 | 153 | 1.02 |

Mean value | 0.98 | ||

Standard deviation | 0.028 |

Girder Notations | M_{u.exp}/kN·m | M_{u.cal}/kN·m | M_{u.cal}/M_{u.exp} |
---|---|---|---|

PSUC-RCCD-5(1) | 237 | 209 | 0.88 |

PSUC-RCCD-5(2) | 240 | 209 | 0.87 |

PSUC-RCCD-1 | 246 | 229 | 0.93 |

P-UHPC-5 | 246 | 215 | 0.87 |

P-UHPC-1 | 252 | 237 | 0.94 |

Mean | 0.90 | ||

Standard deviation | 0.033 |

Comparison Girders | M_{exp.seg}/M_{exp.int} |
---|---|

PSUC-RCCD-5(1)/PSUC-RCCD-1 | 0.96 |

PSUC-RCCD-5(2)/PSUC-RCCD-1 | 0.98 |

P-UHPC-5/P-UHPC-1 | 0.98 |

Mean value | 0.98 |

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## Share and Cite

**MDPI and ACS Style**

Chen, Y.; Zhou, J.; Chen, B.; Su, J.; Nuti, C.
Flexural Behavior of the Composite Girder of a Prestressed Segmental UHPC Channel and a Reinforced Conventional Concrete Deck. *Buildings* **2023**, *13*, 3132.
https://doi.org/10.3390/buildings13123132

**AMA Style**

Chen Y, Zhou J, Chen B, Su J, Nuti C.
Flexural Behavior of the Composite Girder of a Prestressed Segmental UHPC Channel and a Reinforced Conventional Concrete Deck. *Buildings*. 2023; 13(12):3132.
https://doi.org/10.3390/buildings13123132

**Chicago/Turabian Style**

Chen, Yicong, Jialiang Zhou, Baochun Chen, Jiazhan Su, and Camillo Nuti.
2023. "Flexural Behavior of the Composite Girder of a Prestressed Segmental UHPC Channel and a Reinforced Conventional Concrete Deck" *Buildings* 13, no. 12: 3132.
https://doi.org/10.3390/buildings13123132