# Design Approach for Composite Pavement Structure Incorporating Reflective Crack Considerations  
[PERSON]  
1 School of Civil Engineering, Tianjin Chengian University, Tianjin 300384, China; [EMAIL_ADDRESS] (N.F. ); [EMAIL_ADDRESS] (X.W.) [PERSON]  
1 School of Civil Engineering, Tianjin Chengian University, Tianjin 300384, China; [EMAIL_ADDRESS] (N.F. ); [EMAIL_ADDRESS] (X.W.) [PERSON]  
3 Academy of Eco-Civilization Development for Jing-Jin-Ji Megalopolis, Tianjin Normal University, Tianjin 300387, China  
that can affect driving comfort and stability [3; 4]. Nevertheless, the substantial disparity in material modulus between the rigid and flexible pavement layers gives rise to the challenge of disparate pavement deformation. Hence, the determination of the appropriate asphalt layer thickness holds a major significance in pavement structure design [5; 6]. Currently, the design methods employed for composite pavement structures encompass several approaches. The American Asphalt Association's AI deflection method [7] primarily emphasizes the control of average deflection and deflection discrepancies at slab edges near joints or cracks. It prescribes that the deflection difference between the two slab edges at joints or cracks should not exceed 0.05 mm, and the average deflection value of these edges should remain below 0.36 mm. Furthermore, it recommends a minimum thickness of 10 cm for the asphalt surface layer. In situations where there are substantial variations in the temperature gradient, particularly when the maximum and minimum temperature differences exceed the daily average recorded over the past 30 years, a minimum asphalt overlay layer thickness of 20 cm is advised. However, it is important to note that this method relies on empirical determinations of asphalt layer thickness and lacks a scientific calculation foundation. The AASHTO (American Association of State Highway and Transportation Officials) method [8] employs the concept of equivalent thickness to determine the appropriate thickness of asphalt layers, incorporating comprehensive factor corrections to enhance flexibility and facilitate widespread utilization. Consequently, this method achieves better alignment with real-world projects. However, it overlooks control parameters pertaining to cracks in cement concrete pavement following the addition of the asphalt surface layer. This oversight implies that the cement concrete pavement stabilizes and remains undamaged after the asphalt surface layer is applied, which does not align with actual conditions. The COE (Corps of Engineers) method, developed by the US Army Corps of Engineers [9; 10], offers empirical formulas for calculating asphalt layer thickness through a combination of theoretical analysis and experimentation. The effective thickness method [7] is predicated on the notion that the overlay layer thickness should encompass the requirements of both the new road surface and the effective thickness of the existing road surface. Nonetheless, the formulas proposed by these methods exhibit relative simplicity and consider a limited number of factors. Additional design methods, such as the static model analysis method developed by Austin Research Engineers [11], the asphalt overlay design method based on fracture mechanics [12], and the analysis system implemented by the University of California, Berkeley [13], rely on foreign experiences to ascertain the appropriate thickness of the asphalt layer. In general, different countries have put forth composite pavement design methods tailored to their specific contexts, offering valuable insights for composite pavement design in China. However, it should be noted that these methods cannot be directly applied to the unique circumstances in China [14]. The design methodology for composite pavement structures outlined in China's \"Design Specification for Highway Cement Concrete Pavements\" [15] centers around the primary design criterion of preventing fractures in cement concrete slabs.