1 Introduction

The orthotropic steel bridge deck is the preferred bridge deck of large and medium span bridges at domestic and foreign countries [1]. Most of orthotropic steel bridge decks are covered with asphalt pavement. The integral stiffness of orthotropic steel bridge deck cannot be effectively improved due to the low stiffness and poor high temperature stability of asphalt pavement. Under the cyclic load of vehicles, this type of pavement is prone to pavement damage and fatigue cracks at the welds of the orthotropic steel bridge deck [2]. The traditional solution is mainly to improve the weld details and increase the thickness of the roof for the orthotropic steel bridge deck. However, the traditional method does not fundamentally solve the problem. The application of Ultra-high Performance Concrete (UHPC) provides a new direction for solving above problems.

Shao’s research team [3] proposed a new steel-UHPC lightweight composite bridge deck structure that connects UHPC pavement with steel deck through stud connectors. The steel stud connectors are the key to realize the joint work of the orthotropic steel bridge deck and the UHPC pavement [4]. Previous studies focused on the asphalt pavement. In recent years, the interlaminar shear stress of the new steel-UHPC lightweight composite bridge deck structure have been widely concerned [5]. Taking the light composite deck of two bridges on Dongting Lake with opening ribs as the engineering background, Zhang et al. (2017) analyzed the influence of local wheel load on the shear stress between the UHPC layer and steel roof interface layer [3]. The results show that, the shear strength of steel studs under the action of standard load vehicles could meet the requirements of static bearing capacity [5].

The interlaminar shear stress distribution of steel-UHPC light composite deck composed of orthotropic steel deck with closed ribs is more complex than that of composite deck with open ribs. This paper calculates the interlaminar shear stress distribution between the UHPC pavement and the steel roof in the steel-UHPC lightweight composite deck with closed ribs of a bridge in North China, and checks the shear strength of the steel stud connectors. Selecting the standard five axle overload vehicles specified in the “General code for design of highway bridges and culverts”, we analyze the influence of triple axle wheel’s load and overloaded vehicles’ conditions on the calculation of interlaminar shear stress between UHPC pavement and steel roof.

2 Finite Element Model of Interlaminar Shear Stress Analysis for Light Composite Bridge Deck

2.1 The Establishment of Local Finite Element Model

This study adopts the local finite element model established by Deng et al. (2017) [6]. The model is based on a bridge in North China. In order to improve the disease resistance of the bridge deck pavement and increase the fatigue life of the steel bridge welds, the new pavement adopts a new steel-UHPC lightweight composite bridge deck as shown in Fig. 1.

Fig. 1.
figure 1

The structure of new steel-UHPC lightweight composite bridge deck.

Full size image

As shown in Fig. 2, the local finite element model of light composite bridge deck contains four diaphragms and five U-shaped ribs. The following assumptions are used in the calculation. The pavement layer is equivalent homogeneous isotropic elastomer. The bonding between pavement layers as well as between the pavement layer and the top plate of orthotropic steel deck are ideal. The displacement boundary conditions of the model are: restraining the displacement of x direction at the end of bridge deck, the displacement of y direction at the end of outer beam, and the displacement of z direction at the bottom of the beam.

Fig. 2.
figure 2

Local finite element model of lightweight composite bridge deck.

Full size image

2.2 Selection of Vehicle Load

Working condition 1: the calculation load of Deng et al. (2017) selects the standard five-axis vehicle specified in the “General Code for Design of Highway Bridges and Culverts”. As shown in Fig. 3, the wheel load of each rear axle is 70 kN. The wheel load area is 0.2 m 0.6 m, and the vehicle wheel load is applied to the mid-span in Fig. 2. Deng et al. (2017) adopts three common transverse loading positions of the wheel: in-between-rib loading, riding-rib wall loading and over-rib loading. The loading methods are shown in Fig. 4. Because six-axis vehicles are increasing and the distance between the rear three axles in a six-axis vehicle is smaller than the distance between the two adjacent diaphragms, this study considers the effect of triple-axle wheel load on the interlayer shear stress of the new steel-UHPC light composite bridge deck structure. The wheel load of each rear axle is taken as 70 kN.

Fig. 3.
figure 3

The axle loads of standard five-axis vehicle (the length unit is in meter).

Full size image
Fig. 4.
figure 4

Three transverse positions of wheel loading.

Full size image

Working condition 2: performing a statistical analysis of vehicle load based on the WIM (Weigh-In-Motion) system. As shown in Fig. 5, the single axle load of the rear axle of five-axle overload vehicle is 252 kN, and the wheelbase is 1.4 m. According to the relative position between the wheel moving load centerline and the reference diaphragm, each wheel load condition moves forward with 100 mm per step.

Fig. 5.
figure 5

The axle loads of overloaded five-axis vehicle (the length unit is in meter).

Full size image

3 The Interlaminar Shear Stress of Steel-UHPC Light Composite Bridge Deck

Based on different wheel load forms and overloaded vehicles, we calculate the maximum interlayer shear stress between UHPC pavement and steel roof in the new steel UHPC light composite deck structure.

3.1 The Influence of Triple-Axle Wheel Load on Interlaminar Shear Stress

The results of Deng et al. (2017) show that the riding-rib wall loading generates the largest interlaminar shear stress, which is the most unfavorable transverse position of wheel loading. After analyzing the most unfavorable transverse position of wheel loading, we further study the influence of triple-axle wheel loads on the interlayer shear stress of the new steel-UHPC light composite bridge deck structure. Figure 6 shows the interlayer shear stress under triple axle load at the selected most unfavorable transverse position of wheel loading. As shown in Fig. 6, when the standard load vehicle is under triple axle wheel load, the interlayer shear stress continued to increase after the wheel load position 1.4 m away from the diaphragm and reached the maximum at the mid-span of the two diaphragms.

Fig. 6.
figure 6

The maximum interlaminar shear stress of different positions under triple axle load of standard vehicle.

Full size image

Table 1 shows the peak values of interlaminar shear stress of steel-UHPC lightweight composite bridge deck structure under different wheel loading methods. As shown in Table 1, the wheel loading method has a great influence on the maximum interlaminar shear stress. The maximum interlaminar shear stress generates under the action of triple axle load. Taking the maximum transverse shear stress between layers as an example, the maximum transverse shear stress between layers under the action of triple axle load is 1.2 times that of double axle load and 1.6 times that of single axle load, which indicates the necessity of considering triple axle load.

Table 1. Peak values of interlaminar shear stress of Steel-UHPC lightweight composite bridge deck structure under different wheel loading methods.
Full size table

3.2 The Interlaminar Shear Stress of Steel-UHPC Light Composite Bridge Deck Under the Action of Overloaded Vehicles

We conduct the statistical analysis of vehicle load based on the WIM system. At the selected most unfavorable transverse loading position, the maximum interlaminar shear stress of different positions under biaxial load of overloaded vehicle are shown in Fig. 7.

Fig. 7.
figure 7

The maximum interlaminar shear stress of different positions under biaxial load of overloaded vehicle.

Full size image

According to results of Fig. 7, under the action of double axle load of overloaded vehicle, the change of interlaminar shear stress of steel-UHPC light composite bridge deck structure is the same as that under the action of double axle load of standard vehicle. After the wheel load position of 0.7 m away from the diaphragm, the value of the interlayer shear stress continues to increase due to the wheel load changing from single axle load to biaxial axle load, and reaches a maximum value at the mid-span of the two diaphragms.

Table 2 shows peak values of interlaminar shear stress of steel-UHPC lightweight composite bridge deck under the action of overloaded vehicles. The maximum shear stress between layers increases significantly under the action of overloaded vehicles. Taking the maximum transverse shear stress between layers as an example, compared with the double axle load of standard vehicle, the maximum transverse shear stress between layers under the action of the double axle load of overloaded vehicle increases by 80%. The shear stress on the studs increases significantly under the action of overloaded vehicles. Therefore, in order to ensure the effective connection between the UHPC layer and the steel roof, it is important to check whether the studs meet the interlayer shear requirements under the action of overloaded vehicles.

Table 2. Peak values of interlaminar shear stress of steel-UHPC lightweight composite bridge deck under the action of overloaded vehicles.
Full size table

4 The Shear Strength Check of Steel Stud Connectors

According to the calculation results of Deng et al. (2017) [6], the shear strength of the studs corresponding to its shear force capacity is 1.84 MPa resulting from the current “Code for Design of Steel-Concrete Composite Bridges” of China.

It can be seen from Table 2 that the studs meet the strength requirements under standard vehicle load. However, under double-axle load of the overloaded vehicle, the maximum transverse shear stress between the UHPC pavement and the steel roof is greater than the maximum shear stress corresponding to the shear bearing capacity of studs. Then studs have the potential to be sheared. Therefore, it is necessary to restrict the passage of overloaded vehicles to meet the strength conditions of the stud connectors, and to ensure that the steel-UHPC light composite bridge deck structure can effectively work.

5 Conclusion

By considering the triple axle wheel load and overload vehicles, this study calculates the interlaminar shear stress of steel-UHPC light composite bridge deck that composed of orthotropic steel deck with U-shaped ribs. The following conclusions can be drawn from the calculation results in this paper.

1) The loading mode has a great influence on the interlayer shear stress calculation of the light composite bridge deck structure. The maximum interlayer shear stress is generated under the action of the triple axle load. Taking the maximum transverse shear stress between layers as an example, the maximum transverse shear stress between layers under the action of triple axle load is 1.2 times that of double axle load and 1.6 times that of single axle load. Therefore, the interlaminar shear stress in the steel-UHPC lightweight composite bridge deck structure generated by the vehicle load will be greatly underestimated when considering only the single-axle load.

2) The interlayer shear stress of the light composite bridge deck structure increases greatly under the action of overloaded vehicles. Taking the maximum transverse shear stress between layers as an example, compared with the double axle load of standard vehicle, the maximum transverse shear stress between layers under the action of the double axle load of overloaded vehicle increases by 80%.

3) According to the calculation results of the maximum interlaminar shear stress of the new steel-UHPC light composite deck structure under different load conditions, the maximum interlaminar transverse shear stress under the action of overloaded vehicles is higher than the shear strength limit corresponding to the shear capacity of the studs in the steel-UHPC light composite deck. Therefore, it is necessary to restrict the passage of overloaded vehicles.