Study On Explosion Resisting Performance Of Outer Stiffening Ring Joint Of Concrete-filled Steel Tube Frame

Since the 21 st century,terrorist attacks and accidental explosions have occurred frequently in various parts of the world.Explosion shock waves act on building structures causing structural damage or even collapse,causing great damage to people's lives and property.Therefore,the anti-knock research of building structures has become an important issue in the field of structural design in recent years.In recent years,a large number of studies on the structure of concrete-filled steel tubes show that Concrete-filled steel tube structure has excellent explosion resistance which shows great potential in the design of anti-knock structures.At present,the research on the anti-knock of concrete-filled steel tubular structures mainly focuses on the anti-explosion research of concrete filled steel tubular columns,there is little research on the anti-knock performance of the joints between beams and columns.The position of the node is a key part of the framework structure,which plays a key role in ensuring the integrity and stability of the entire structure.Therefore,it is of great theoretical and practical significance to study the anti-knocking performance of steel-concrete-filled concrete(CFST)frame joints.In this article,according to the explosion test of the concrete-filled steel tube concrete specimens previously made by the research group in Nanjing,the author create explosive,air,steel and concrete models using LS-DYNA finite element software,and make a full-process simulation of the dynamic response of concrete-filled steel tube specimen under explosine of No.2 emulsion explosive,analizing the whole process of explosion shock wave generation,propagation,action on the surface of specimens and the response of specimens.Verify the accuracy of finite element model parameters and material parameters by comparing the key data such as the deformed shape of the specimen in the finite element model and the test,the pressure-time history,impulse-time history and the displacement-time history.According to the validated finite element model parameters and material parameters,finite element model for explosion test of reinforced ring side column and corner column joint of reinforced concrete filled steel tube frame were established.And a new method named ‘modified definition of load curve method' suitable for large-scale structural explosion test simulation is proposed in order to achieve the balance between computational accuracy and computational efficiency.Using this method to study the anti-knock performance of outer stiffening ring joint of concrete-filled steel tube frame,analyze the deformation of the node,the displacement of key points,the stress of the strengthened ring plate,and the stress of the beam and column,study on failure mechanism of joints under blast loading.Then analizing the effect of scale distance,material strength,steel tube thickness,reinforcement ring plate width and reinforcement ring plate thickness on the anti-knock performance of the joint by a large number of finite element models.The results show that the “modified definition of load curve method” can accurately simulate the dynamic response of structures under blast loading,outer stiffening ring joint of concrete-filled steel tube frame have good resistance to explosion.In the explosion of a large equivalent explosive,the frame beam has a strong support for the node area whick can effectively limit the displacement of the node area.The weak parts of the structure occurred in the joint between the steel beam and the reinforcement ring plate and the mid-span part of the concrete-filled steel tube column.The outer stiffening ring corner joint has better antiexplosion performance than the outer stiffening ring side joint.At the same time,parameter analysis shows that scale distance has a significant effect on node damage,the larger the scale distance,the less severe the damage to the node.The increase of material strength,steel tube thickness and reinforced ring plate thickness can increase the antiknock performance of the joints to varying degrees.While under the premise of a certain increase in the amount of steel used,Increasing the thickness of the steel pipe can enhance the anti-knocking performance of the joint more than the thickness of the outer stiffening ring.