Research On Creep Property Of Glubam And Modern Bamboo Composite Structure

Glubam is the basic material for modern bamboo structure, which is attractingworldwide attention for its good mechanical, environmental-friendly and ener-gy-saving properties. Similar to timber, creep is one of glubam’s main features, whichwill exert remarkable impact on the mechanical performance of bamboo structures.Though creep experiment is a time-consuming and labor-consuming work, it hastheoretical significance and practical value to develop the creep research of glubammaterial as well as develop a general analytical model for predicting the creep re-sponse of glubam members and structures.Firstly, this thesis studies the axial creep behavior of glubam material.Short-term tests of glubam material were carried out first. Then three tension creeptests and three compression creep tests of glubam were conducted under normalin-door service conditions in Changsha for a whole year. Each group was subjected toa stress level of0.2,0.4,0.6time the instantaneous mean strength of glubam, respec-tively. The glubam axial creep deformation versus time curves were obtained from thetest mentioned above.Secondly, a full-scale testing model of truck load laminated bamboo (glubam)bridge was constructed for long term load testing, based on an actual structure. Themid-span deflection of CFRP-reinforced glubam girders were instrumented for threeand half years. The results indicate that the average creep deflection of the girdersafter three years loading is approximately7.98-mm. In addition, the increase in tem-perature and humidity may contribute to creep. The model bridge was then loadedwith spread load until collapse at an ultimate total load of18.5-t. By analyzing theexperimental results, it is realized that CFRP-reinforced glubam girders have suffi-cient capacity to meet the strength and durability requirements for practical usage.Although CFRP layers could improve the performance of glubam girders effectively,there is certain degree of decrease in strength and stiffness when considering thelong-term performance. The research may contribute to developing future designguidelines of glubam bridge structures, and construction measures are suggested forthe bamboo bridge according to the results of the experimental and analysis results.At last, based on the data of previous glubam material creep test, the glubamcreep constitutive model was developed in the form of Burgers four elements viscoe-lastic model. Following the method of Gilbert for the analysis of cross sections, the CFRP reinforced glubam beam’s creep behaviors were analyzed. By comparing theanalysis results and experimental results, it was studied that the difference betweenthe two results could be controlled in less than10%. Parametric studies also indicatethat increasing the thickness of CFRP layer plays a significant role in controlling de-formations and improving the creep behaviors.