Refined safety assessment of steel grid structures with crooked tubular members

For grid structures, damages of structural members such as crookedness significantly affect the overall structural safety. Traditional assessment methods can hardly evaluate the impact of crooked members in existing grid structures accurately due to difficulties lying in crookedness measurement and residual load-bearing capacity analysis. In this paper, a new method of refined model adjustment and structural assessment with crooked tubular members of steel grid roofs taken into consideration is proposed, while the crooked measurement is conducted with an image-based 3D measurement method for the first time. Firstly, the original shape of crooked members is recovered using image-based 3D measurement method. Secondly, the measured deformation of the crooked members is adjusted from the load status at the time of measurement to the zero-load status in two ways. Finally, the FE model of the entire grid structure, together with the adjusted crooked tubular members is adopted in the residual load-bearing capacity analysis considering both geometric nonlinearity and material nonlinearity. A large span steel grid roof structure containing four crooked tubular members is utilized for the illustration and validation of the proposed methodology. The proposed method inventively offers a new direction for refined assessment of existing grid structures with crooked members and provides significant potential for practical implementation.