EVALUATION DEMAND OF SEPARATION GAP ANGLE IN ADJACENT STEEL MOMENT RESISTING FRAMES UNDER FAR-FIELD AND NEAR-FIELD EARTHQUAKES

In crowded cities, building structures are usually constructed in close proximity to one another because of restricted availability of space. In many cases, every building in a block is in full or partial contact with its neighboring buildings. Because of insufu{fb01}cient separations, their different heights and seismic-resisting systems collision can occur between adjacent buildings during strong ground motions. This collision can make partial or general damages to the structural elements and accelerate their failure by affecting their stiffness. This phenomenon is commonly referred to as structural pounding. Pounding between inadequately separated buildings has been observed in most previous major earthquakes. Each time pounding occurs, building structures will sustain short duration large impact force not specifically considered in conventional designs. The severity of the impact depends on the dynamic characteristics of the adjacent buildings in combination with the earthquake characteristics. Aiming to prevent such collisions, the present study tends to estimate the demand of separation gap angle at the highest collision level using various proximity compositions of two regular steel moment resisting frames under near-field and far-field earthquake records. Accordingly, 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20 story three-span steel moment resisting frames are placed in all possible pair proximity states, and their demand of separation gap and separation gap angle is calculated using dynamic analysis of the nonlinear time history with the OPENSEES software, and compared to Standard 2800 (Fourth Edition) requirements. The results indicate that in some proximity states the Standard 2800 requirements underestimate the demand of separation gap angle. Meanwhile, the average of demand of separation gap angle in the states studied under the component vertical to the fault of near-field earthquakes is 1.48 and 1.35 times greater than those of the far-field earthquakes and the component parallel to the fault of near-field earthquakes respectively.