Study On Whiplash Effect Of Reinforced Concrete Frame Structure With Towers

Presently, the structural system that constructing towers at top of the building is applied increasingly, such as the stair case, elevator case, water tank room, small mezzanine and so on. However, previous damage provided that roof towers had strong response under earthquake. Even without damage or very light damage of main structures, towers were damaged seriously. So, study on whiplash effect of structure with towers under earthquake has important practical significance for avoiding or reducing the damage caused by earthquake.In this paper, taking a six-storey reinforced concrete frame structure with two roof towers as an example, firstly, the frame structure has been determined irregular layout by the rules of structural arrangement. Then, programs 1 ~ 4 are made, assuming that the frame structure in cases of no tower and one–floor, two–floors, three–floors towers. Based on Code for design of concrete structures (GB50010-2002) and Code for seismic design of buildings (GB50011-2001), we study the severity of the whiplash effect and the impact of the whiplash effect on the main structure under earthquake when changing the height of the roof towers. It comes to the following conclusions: 1. In the case of the same main structure, to increase the roof tower floors results in the structural cycle of each mode increasing.2. Obtained by the modal analysis that, with the roof tower floors increasing, the main modes of level transfer from low-order to high-order, it needs to pay attention to the impact of higher modes.3. Maximal lateral deformation occurred on top story. In the corner, concave and convex parts of the top floor produce greater deformation than other parts. With the tower floors increasing, the maximum deformation gradually transfers from the top of main structure to the top of towers, and the largest extent of deformation gradually decreases. It shows that changing the height of the roof towers will alter the overall deformation distribution of structure.4. Along Y direction to enter the earthquake response spectrum, the program 1 ~ 3 show that the overall deformation in left side of structure is greater than that in right side, but the program 4 reverses. It indicates that structural deformation in both ends is inconsistent and prone to reverse effect when the aspect ratio of the structure is greater.5. Increasing the number of roof tower floors mainly causes the top floor's deformation of main structure increasing, and also leads to increasing displacement of other lower floors. Story drift curves mutation multiply as to towers, and the impact is greater with the tower floors increasing.6. Compared with no tower structure, the top floor's level seismic force of main structure with the roof towers is amplified in varying degrees. Compared with the second program, the first tower floor's level seismic force is also amplified in program third and four. It is caused by the whiplash effect of roof towers, and the higher the tower is, the more obvious the whiplash effect is.7. Under different seismic waves, the overall deformation of structure performs in varying, which indicates that the overall deformation distribution of structure can be more fully grasped through a number of seismic waves.This paper not only provides a method to study whiplash effect of reinforced concrete frame structure with towers under earthquake, but also provides some degree reference value for engineering and technical personnel.