Study On The Natural Degradation And Long-term Bending Creep Behavior Of Round Bamboo Bars

Bamboo is a kind of tall arbor like gramineous plant,which is widely distributed in the south of China.It grows very fast and has high strength.It can be used as a good building material.As bamboo is a kind of natural biological material,its performance will be affected by many factors,such as origin,light,variety,individual differences,etc.,this paper selects Nanzhu from Changning bamboo sea,Yibin County,Sichuan Province as the research object,and studies the long-term performance of various mechanical and physical properties of Nanzhu.The main contents of this paper are as follows:(1)Understanding the strength of bamboo is the prerequisite for its scientific application in engineering.In this paper,the tensile strength,compressive strength,flexural strength and compressive strength of bamboo tubes with and without bamboo nodes are tested every 3-4 months,and the tensile,compressive and flexural strength of this batch of bamboo are studied systematically Changes in performance over time.The results showed that the performance of Phyllostachys pubescens under unprotected conditions would deteriorate with time,and its strength would be about 60%-65% of the original one year later.(2)As a kind of biological material,bamboo contains more water in its cells,and its strength will change in the process of water absorption and loss.In this paper,the water content,water absorption and dry shrinkage of round bamboo exposed to natural environment for a long time were tested in batches,and the changes of these properties related to water content in a year were observed.The results showed that the moisture content of bamboo changed significantly with climate,the water absorption increased with time,and the dry shrinkage decreased with time.(3)In this paper,16 bamboo members are tested for long-term bending performance,and the creep performance of Bamboo under different load levels is studied.After the load is added,the deflection changes of bamboo members are recorded every other period of time,and the wood structure model is applied to observe whether it is applicable in bamboo structure.The test and analysis show that the creep model of wood structure overestimates the creep of bamboo structure at low stress level,while the creep model under medium stress level fits well,and it is easy to underestimate the creep of bamboo structure at high stress level.When the applied load exceeds the limit load of bamboo structure,the bamboo structure will not reach a stable state,and the load will increase continuously in a short period of time until it is destroyed.(4)In this paper,the mechanism of bamboo natural degradation was analyzed and explored,and the main influencing factors of bamboo degradation were cracks,mould and moth.Among them,cracks directly affect the mechanical properties of bamboo,mold erodes the cells of bamboo,and makes the water content of bamboo significantly increase,thus affecting the performance of bamboo,and moth is easy to make bamboo produce holes.It was found that bamboo was easy to crack under the alternate action of rain and sunshine,which accelerated the infiltration of rain water and caused rapid growth of mold,further affecting the performance of bamboo.