Study On The Simplified Analytical Methods Of Hot Strip Mill Box Foundation

In order to meet the requirement of Rolling Process, the equipment of hot strip mill often set on box foundation whose integral rigidity is quite large, and, the length of the foundation is as long as several hundred meters without settlement joints, usually.For the internal force analysis of super.long box structure, people use simplified analysis methods on abroad. These simplified analysis methods are convenient, are suitable for routine design software, but most of them neglect the connections along longitudinal direction of the box foundation and the characteristics of spatial stress.The rationality of simplified analysis and effect on foundation form different foundation conditions need to be proved, no matter the laminar flow region whose structural arrangement and load are relatively simple or the finishing stand.The paper bases on the background of foundation of 2250 hot rolling line equipment, and using finite element program ABAQUS ,establish three.dimensional finite element model of the foundation of equipment and the simplified analysis model which is used in industrial design for comparison. It can be the reference for designers.The conclusions are as follows:1)The analysis model was constructed using thick shell element S8R of ABAQUS to simulate the deep slab can get the better calculating precision at lower ratio of span to thickness(4~5). The thick shell element in the model of deep flexural member can give better results but beam element is not suitable, so thick shell element is recommended when the ratio of span to thickness is less than 4.2) The 3.D analytical results of laminar flow region show that the moments of top slab and base slab vary little along longitudinal direction, and the absolute moment value of axes with big column is greater than the value of axes without big column, then the results of axes with big column is safe for design. Meanwhile, modulus of subgrade reaction has a great effect on the sagging and negative moment of base slab.3) A comparison between 3.D model of laminar flow region and plan frame model with big column is made to show the minimum displacement of top slab and base slab calculated by these models are close to each other. The absolute minimum and maximum moment of top slab and base slab calculated by plan frame model are smaller 20%~30% than results of 3.D model if the modulus of subgrade reaction is little, and are close to results of 3.D model if the modulus of subgrade reaction is large. Therefore, in the internal force analysis of top slab and base slab of laminar flow region using plan frame model with big column, the minimum and maximum moment of top slab and base slab should be increased about 30%~40% if the modulus of subgrade reaction is little.4)The results of different counter force coefficient along the path in the three.dimensional base slab model of finishing stand shows that the maximal and minimal moment value of transverse direction are smaller 35%~40% than the bedding counter force coefficient if the modulus of subgrade reaction is bigger. But it is litter effect on the value of lognitudial moment.5) The moments of transverse and lognitudial direction in the raft plate model is greater than in the three.dimensional finishing stand model by comparison. The minimal moment value of the raft plate model is closer to the three.dimensional finishing stand model if the coefficients of foundation bed counter force increase. The maximal moment is no change as the same condition. From these, we can conclude that it is secure to use the raft plate model. The absolute moment value of the top and bottom floor in the frame model is bigger than in the three.dimensional finishing stand model and it can be used to design for the structure safely.6) The moment value of the support and the mid.span assumed the two ends of external wall with fixed end restraint is according to the three.dimensional finishing stand model under the water loads. The results are safe to use the top hinged connection and the bottom fixed connection for external wall.The rationality of simplified analysis method of hot rolling equipment foundation has been identified in this paper by researching, and the conclusion can give reference for code and designer.