Concrete cracking and interface slip decrease the bending stiffness of steel-concrete composite beams (SCCBs) in the negative moment region. To evaluate this decrease in the stiffness of SCCBs, a static differential equation is used to derive analytical expressions of interface slip and deflection. Based on the static load test results for SCCBs, the influence of concrete cracking and interface slip on the stiffness is analyzed. A linear stiffness reduction method is proposed for calculating the stiffness of SCCBs in the negative moment region after the concrete undergoes cracking. The proposed method can be used in engineering applications as it enables the facile and accurate calculation of the deflection and slip and the changes in stiffness of SCCBs in the negative moment region. The method can also be used for predicting and evaluating performance in the field of structural design.

The effect of various slope angles, ground roughness and positions on tornado loading characteristics of double-sloped roof is identified through Ward-type tornado numerical simulation. Tornado fields under multiple operating conditions are established through a numerical Ward-type tornado generation apparatus and the reliability is verified by comparing simulation results with experimental data. A comparison of wind pressure distribution for double-sloped roofs with four different angles is used to determine the most unfavourable roof conditions for a tornado field. The wind pressure characteristics of double-sloped roofs at different locations in a tornado field is examined by comparing the wind pressure coefficients at five different locations on smooth and rough ground. Calculations of wind pressure coefficients for five ground roughness are carried out to identify the effect of different ground roughness on wind pressure distribution in roofs. Vortex volumes at different locations are calculated and analyzed to further verify the relationship between the wind pressure characteristics at different locations. This study sheds light on tornado loads on double-sloped roofs at various ground roughness and positions, and helps to clarify the mechanical properties, unfavourable locations and wind resistance design of double-sloped roofs under tornado action.