Self-balancing constant loading device for researching creep performance of concrete-filled steel tube member

Abstract

The invention discloses a self-balancing constant loading device for researching creep performance of a concrete-filled steel tube member, and belongs to the field of building structure engineering. In order to research the creep mechanical property of the concrete-filled steel tube, a long-term constant load test needs to be carried out on a concrete-filled steel tube member, and the self-balancing constant loading device is easy to operate, convenient and easy to implement, and does not need to occupy a large reaction frame of a laboratory for a long time; the working principle is as follows: a jack, a bearing plate and an anchor bolt form a self-balancing loading system to apply a test load, an anchor nut of the bolt fastens and locks the test load value, the jack supplements load relaxation caused by concrete shrinkage and creep, and a supplementary loading nut fastens and locks the supplemented load value. Therefore, the purpose of simulating the real long-term constant load of the building structure is achieved. The device is simultaneously provided with other measuring tools and the like, and can be used for analyzing and researching the creep mechanical behavior of the concrete-filled steel tube.

Description

technical field [0001] The invention relates to the field of building structure engineering, in particular to a self-balancing constant loading device for studying the creep performance of steel pipe concrete components. Background technique [0002] The steel pipe concrete member is made of concrete poured into the steel pipe. It is a composite member of steel and concrete. The load is shared by the steel pipe and the concrete material. Due to the restraint of the steel pipe on the concrete, the compressive strength of the concrete is greatly improved. Constrained by the steel pipe, the local buckling strength of the steel pipe is greatly improved, so this composite member has excellent mechanical properties and is widely used in building structures. However, under the action of long-term pressure load, the concrete in the steel pipe will have a shrinkage and creep effect, which will cause a significant change in the mechanical properties of the steel pipe concrete member. ...

AI Technical Summary

Problems solved by technology

[0003] In the past, the test device for steel pipe concrete members under long-term loads was loaded by a set of bolt fastening pretension and specimen self-balancing method. This loading method has two major problems: first, it is only suitable for operations with small loads. When the load is large (more than 10 tons), it is very difficult to manually tighten the bolts, and the ultimate load of the general steel pipe concrete specimen test needs to reach more than 120 tons, and it must be loaded with the help of a jack and a large reaction force frame or a pressure testing machine; second, When tightening a single bolt, it will affect the stress of other bolts. Due to the mutual influence of the force between multiple bolts, it is very difficult to manually control the pre-tightening force of all bolts to be uniform. In addition, when tightening the nuts When the torque must be applied, it means that the CFST specimen bears the additional torque and generates additional shear stress, which is inconsistent with the actual situation of the project.

[0004] Under long-term loading, the shrinkage and creep effect of the core concrete in the steel pipe will cause the stiffness of the steel pipe concrete to degrade continuously, making the pre-tension force of the bolt lock continue to relax, which means that the test load strength is constantly attenuating. To ensure the long-term stability of the test load strength Relying on a large reaction force frame or a pressure testing machine will occupy the test equipment for a long time, and the cost is very high, which is unbearable for the laboratory. This project is to solve this problem and develop a A self-balancing long-term constant loading device capable of flexible supplementary loading

Images