Dynamic Properties of Lightweight Concrete Beams Made by Sedimentary Lightweight Aggregate

Abstract

This research aimed to investigate the engineering and dynamic properties, such as unit weight, stiffness, natural frequency and damping ratio, of lightweight aggregate concrete (LWAC) beams made with sedimentary lightweight aggregate (LWA) and to compare with companion normal weight concrete (NWC) beams. The primary design variables included compressive strengths of 20, 40, and 60 MPa and reinforcement ratios of 0%, 1.03%, and 2.32%, respectively. A total of 62 beams were made and tested. Test results showed that the unit weight of LWAC beams was about 16–23% lower than that of NWC beams for the same strength level. In addition, the reduced modulus of elasticity of LWAC resulted in a stiffness decrease of reinforced lightweight concrete (RLC) beams of 5–15% related to the reinforced NWC (RC) beams. Nevertheless, the natural frequency of RLC was still higher by about 1–10% than that of RC. In contrast, it was also found that the porous LWA with high damping capacity enhanced the damping ratio of RLC beams by 13–30% for concrete strength in the range from 20 to 60 MPa. As a whole, the lower the concrete strength is (e.g., 20 MPa), the more effective will be for the lightness of LWAC beam and the damping ratio, which in turn is more favorable to the seismic resistant efficiency of LWAC beam.