## 1 Introduction  
Foam concrete is a cellular lightweight concrete with reduced density. It is made of cement and fly ash with a compressive strength between 9 and 24 MPa in different densities [1]. The density of foam concrete varies from 400 kg/m\({}^{3}\) to 1600 kg/m\({}^{3}\), much lighter than normal concrete. Up to now, foamed concrete has been widely used for non-structural members in buildings, working as a lightweight material for sound barriers, and as filling for composite members [2]. It has also been used as filling for masonry due to its good thermal insulation and ability to protect against fires [3]. Although foam concrete has been widely used for non-structural purposes, there is an increasing trend for its use in structural members. Little research has been done for the compressive and flexural resistance of foam concrete members [4]. [PERSON] al. made numerical studies on steel-UHPC-steel sandwich beams with novel enhanced C-channels [5]. [PERSON] et al. [6] studied the behavior of steel-concrete-steel sandwich structures with lightweight cement composite and novel shear connectors. However, no studies on composite structures using foam concrete can be found in the current literature. Due to its inherent low strength, foam concrete has to be further reinforced by steel reinforcements for structural purpose [7, 8, 9]. [PERSON] et al. [10] studied the heat of hydration in foamed concrete. [PERSON] et al. [11] studied the effect of high fly ash content on the compressive strength of foamed concrete. [PERSON] et al. [12] introduced the process of continuous manufacturing of lightweight foamed concrete. The cold-formed thin-walled steel structure has been developed for more than half a century, and has been widely used in many construction projects. In 2001, the United States, Canada, and Mexico integrated the specifications for cold-formed thin-walled steel, and released the integrated specification \"Code for Design of Cold-Formed Steel Components\" [13]. China also published the national standard \"Technical Specification for Cold-Formed Thin-Walled Steel Structures\" (GB50018-2002) in 2002 [14].In 1987, in order to promote the application of profiled steel-concrete composite slabs in the UK, [PERSON] and [PERSON] [15] did a large number of related tests, which greatly promoted the application of composite slabs. In 1997, [PERSON] and [PERSON] [16] analyzed the slip of composite slabs. In 2004, [PERSON] and [PERSON] [17] used high-strength concrete instead of ordinary concrete to cast composite slabs, and analyzed the stiffness changes of composite slabs and the performance of the slabs when the ultimate load was reached. [PERSON] and [PERSON] [18] developed a method to calculate the bearing capacity of composite slabs, and verified the feasibility of this calculation method through experiments. In 2008, [PERSON] [19] proposed a new method that can calculate the composite board by launching a test, which is more economical and simpler than the traditional test method. Therefore, to enable a further application of this new type of concrete to the current construction projects such as tall buildings [20; 21; 22], a new composite floor slab system made of cold-formed thin-walled C steel channel embedment and foam concrete is developed in this paper. As it shown in Figure 1, it is a one-way slab system. It uses a cold-formed thin-walled C steel channel as a major steel skeleton embedded into the foam concrete, which is laterally connected by steel belts. After casting the foam concrete, the one-way slab is formed. Due to the lightweight feature and excellent fire resistance of foam concrete compared to normal concrete, this new composite slab system exhibits a great application prospect in multi-story buildings. However, the failure mechanism and the flexural capacity of this type of new composite floor slab system are still not clear.