Study On The Concrete Lattice Beams Of The Prestressed Anchor Cable Frame And The Design Method Research

Slope retaining is an important problem which is usually involved in the municipal construction. Many kinds of measure have been used for the slope retaining, such as anchor bar, prestressed anchor, pile and retaining wall. Nowadays,a new compound structure of lattice beam and prestressed anchor is widely used for preventing and remedying landslide. The anchor force is transferred by the lattice beam to the slope body, and results in the compressive stress in the slope body and the stress distribution in the body is improved. The compound structure of lattice beam and prestressed anchor is an effective landslide controlling measure, which takes account to both the deep anchoring and the surface retaining, and the construction of the structure is safe and accessible, and the maintenance of the structure is convenient. So the compound structure of lattice beam and prestressed anchor is worth popularizing in the coming days. However, the research of the anchoring principle is plenty now, but the internal force study of the lattice beam is limited, so the design of the beam is usually based on the engineering experience, and there is no code for designing. Therefore, the study of the lattice beam and the research of the beam designing method are very necessary. In this thesis, the internal force of the lattice beam is studied through theoretical analysis which deals with the plane model and numerical simulation which deals with the space model, and a design method for the beam is put forward in the end of the thesis. The theoretical analysis of the lattice beam includes two methods which respectively based on two theories, one is the Winkler's assumption, another is half-space elastic foundation theory. The results of the two methods are compared, and the one which is closer to the fact is chosen to be the theory foundation for deducing the design method. Meanwhile, to confirm and modify the theoretical results, the numerical simulation is carried out by FLAC3D. According to the above theoretical and numerical analysis, the main results and conclusions of the thesis are as follows: â‘ On the soil ground, the moment results concluded from two theoretical methods are different. The negative moment of the beam can not be concluded by the method based on the half-space elastic foundation theory, but the negative moment is proved by the numerical analysis. However the results concluded from the method based on the Winkler's assumption is closer to the fact. On the rock ground, the results concluded from two theoretical methods are similar, but compared with the numerical results, the results value concluded from the method based on the Winkler's assumption is smaller. â‘¡Compared the FLAC3D analysis results and the theoretical results, the result difference between the numerical model analysis and the theoretical model analysis is obvious. According to the numerical model analysis which based on the space model, the moment distribution in the vertical beam is not symmetrical. The maximum positive moment appears at the position held by the anchor near to the top of the slope. The moment distribution in the horizontal beam is nearly symmetrical, but the moment value of the horizontal beam is strongly affected by the position of the beam on the slope and the slope geological condition. In short, the numerical results more exactly reflect the affection of the slope geological parameters to the internal force of the beams, and reflect the restriction of the beams to each other. â‘¢Because the numerical model is more similar to the fact and the numerical results are relatively reliable, it is necessary to modify the theoretical results according to the numerical results. In the thesis, the modifying detail are presented. Based on theoretical and numerical analysis, the design method of the lattice beam is concluded. This method is fit for manual work, so it is convenient for the designers. Compared with an engineering example, it is proved that this design method can be used for reference in engineering.