Seismic analysis of steel beam encased column composite – Open vs closed geometry

<title>Abstract</title> <p>A composite frame structure steel beam encased column precast without slab under I-section and hollow square tubular section to analyse the seismic performance and provide the structural solution over conventional reinforced concrete. The dynamic properties, viz., acceleration, velocity, displacement of the structure and its failure modes were analysed by shake table test by scaling the G-storey three-span structured model to 1:3. A scaled structured model was recorded using El Centro (1940) ground motion. The prototype details, measurements, construction, design and its testing methods were presented. Correspondingly, a non-linear numerical model,SeismoStruct developed to simulate structural response under identical earthquake excitation and validate the numerical prediction against experimental results. As inferred from the dynamic analysis, the maximum acceleration exerted by the I-encased composite is followed by controlled and better acceleration of hollow and RC structures, respectively. Moreover, the velocity of all the frame structures shows a comparatively similar range. Whereas, hollow section experienced a lower displacement range, followed by I-section and RC structure. Based on the analysis, encased composite provided a higher stiffness-to-weight ratio with better ductility, post-elastic stability and reduced cracking concentration. Open geometry provided strong directional stiffness with bending resistance and moment capacity, whereas closed geometry provided more torsional behaviour with good confinement and potentially better over the symmetry. In addition, hollow sections are better suited in economic aspects than conventional structures. Numerical model SeismoStruct structurally simulates the dynamic properties with an error margin of ± 5, which shows a reasonable agreement and is considered to be essential for engineering applications. An outcome of the study provides the effectiveness of using encased composite frame structure as seismic resilience in earthquake-prone regions.</p>