# Structural Behaviour of Aluminium-Timber Composite Beams with Partial Shear Connections
## 1 Introduction
Furthermore, the behaviour of aluminium and timber composite beams with partial shear connections calls for further investigation. Due to the fact that the thermal expansion coefficients of aluminium and timber are different, the impact of the thermal effects should be evaluated [31]. Furthermore, composite structural elements may require strengthening [32]. For this reason, guidelines for strengthening of aluminium-timber composite structures should be developed. Furthermore, the fire resistance of aluminium-timber composite elements should be investigated. Last but not the least, aluminium-timber composite structures should meet the requirements of sustainable construction. Sustainability in construction is a very important trend in modern design [33]. Demountability is essential for sustainable construction. For this reason, new types of composite systems should be easily demountable at the end of their service life. Thanks to demounting, construction materials can be reused or recycled [34]. Steel and concrete composite beams have been widely used in civil engineering. Headed shear studs welded to the top flanges of steel girders are economical and easy to install, and, as a consequence, they are the most commonly used shear connectors [35]. However, the use of such headed studs makes the dismantling of composite beams nearly impossible, and beam components cannot be reused in the future. For this reason, demountable shear connectors for steel and concrete composite structures have been developed and investigated in recent years to facilitate the deconstructability of composite beams. [PERSON], [PERSON], [PERSON], [PERSON], and [PERSON] [36; 37; 38; 39; 40] modified headed studs to develop demountable shear connectors. Similarly, [PERSON] and [PERSON] modified headed studs to create a new demountable shear connector for aluminium and concrete composite beams [41]. Due to the fact that no design guidance for composite beams with demountable shear connectors is currently available, [PERSON] et al. [38] suggested applying the rules specified for headed shear studs and bolts in the EN 1994-1-1 [27] and EN 1993-1-8 [42] standards, respectively, to evaluate the load capacity of demountable shear connectors. [PERSON] et al. [40] compared the structural behaviour of a demountable composite floor system and a non-demountable composite floor system. The load-bearing capacity of both compared systems was similar, but the initial stiffness of the composite floor system with demountable shear connectors was lower than the one of the composite floor system with conventional headed studs. Based on their tests, [PERSON] et al. [40] demonstrated that the plastic resistance of the demountable composite floor system with partial shear connection can be obtained using the rectangular stress blocks method as well as the interpolation method. [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], and [PERSON] [35; 43; 44] tested demountable shear connectors made of high-strength friction-grip bolts. [PERSON] and [PERSON] [35] described the load-slip curve for a connection with pre-tensioned bolted shear connectors. The load-slip curve had three distinct sections. In the first section, the authors observed \"full interaction\" held by friction. In the second section, they noticed a region of \"zero interaction\" with slip corresponding to the clearance between the surrounding concrete and the bolts. In the last section, they discovered \"partial interaction\" because the bolts started to bear onto the concrete. [PERSON] et al. [45; 46] analysed the steel and concrete composite elements with high strength bolts. They conducted push-out tests and compared the bolts with headed studs. The load-carrying capacity of the shear connection with the bolts was 5% lower than the shear resistance of the connection with the headed studs. The stiffness of the connection with the bolts was 50% lower than the stiffness of the connection with headed studs [47].