Experimental Study On Seismic Behavior Of Sub-element In Cross Steel Truss

The air-cooled condenser structure system is the main construction support systems for the air-cooled condenser. Its superstructure is cross steel truss and its substructure is large reinforced concrete hollow pipe column. It is a steel reinforced concrete mixed structure system. This structure system has complex connection, which supports heavy equipment loads and complex dynamic loads. Today, many air-cooled condenser structure systems are still designed by developed countries. There are not any full and systemic design method and rules about the air-cooled condenser structure system in our country. It can be a help for the engineering design to deeply analyze the structure behavior and have an experimental research on the typical joints and members in the air-cooled condenser structure system.This article does experimental research on seismic behavior of sub-element in cross steel truss of the air-cooled condenser structure system, which is a constituent part of the experimental research on big model of the entire support structure. Firstly, according to the pseudo-static test of sub-element in cross steel truss, the mostly destroy mode of specimen are summarized, that is to say, the main brittleness breakages of sub-element in cross steel truss are the welded seam connect damages between the level inclined brace and the chord and the welded seam rips on the end joint of the bottom chord. The main ductile breakages of the specimen are high strength bolt slippage, the plate rip in the bolt connect place, the extruded destroy of bolt hole, the level inclined brace is compressed buckled, the diagonal web is compressed buckled and the joint plate is buckled. Secondly, the hysteretic behavior of specimen is analyzed. The conclusion of the experiment analysis is that the bearing capacity of the sub-element in cross steel truss is relatively high, and the deformation capacity and ductility is quite well. The deformation of the joint region is small, and its stiffness is large. The earthquake energy of specimen is mostly dissipated by the truss member deformation, which satisfies the seismic design requirements of "the joint is stronger than the frame member". When vertical load is less, that is to say, the stress-design strength ratio of the truss member is small, both the ductility and energy dissipation capacity of specimen are preferable. Therefore the author put forward the suggestion that the stress-design strength ratio of the member in the truss should be controlled in the certain scope, when structural engineer carries on the seismic design. Finally, in view of the complex dynamic load on this structure system, the bolt connection should be adopted with high-strength friction-type bolts and the contact surfaces can be dealt with sand blasting. And the connecting of the welded seams are advised to use butt weld that are fully welded, but when the double-sided fillet weld is used, they should be design on equal strength.This article uses ANSYS to analyze the model specimen of sub-element in cross steel truss, the simulation analysis indicates that the failure mode of the specimen is basically identical with the experimental failure mode and the consequence of analysis can better reflect the stress condition of the joint region.