| Reconsolidated bamboo, also called heavy bamboo,was a kind of artificial board, which had high strength, large specifications and a natural bamboo texture. It was prepared by drying, sizing, forming and hot pressing from long bamboo strip, bamboo thread or bundle of bamboo filament. The glued laminated timber was formed by timber, whose thickness was less than 45mm and was mainly glued together along the grain. Wood-frame houses or bamboo structural building were energy conservation and environmental protection, safe and reliable, and had short building cycle. Otherwise, wood and bamboo were renewable, lightweight and high-strength. Introduced the prestress technology into wood-frame or bamboo structure could make full use of compressive strength and reduce member section size. However, in the long term usage of bamboo-timber structures, creep would influence the mechanical behavior, and the research on creep was blank. Therefore, it was of high theoretical significance and practical value to carry out the long-term bending properties of prestressed gluing bamboo-lumber beams. Based on above reasons, the following works were carried forward in this paper:First, in order to analyze the experimental result of prestressed gluing bamboo-lumber beams after long-term loading test, the compressive test on gluing bamboo-lumber along the grain and the tensile test on prestressed steel wire were arranged, and then the corresponding strength and elastic modulus were obtained.Second, under the indoor environment of normal use in Harbin, the prestressed gluing bamboo-lumber beam was divided into A, B and C groups. For group A, remained total pre-tension value and long-term load invariable, and changed the prestressed steel wires number; for group B, remained prestressed steel wires number and long-term load invariable, changed the total pre-tension value; for group C, remained prestressed steel wires number and total pre-tension value invariable, changed the long-term load. The test was divided into three batches, and 14 beams were loaded in the whole experiment period. Through continual monitoring of 60 days on beams of each batch, the data of prestressed gluing bamboo-lumber beam under normal use environment was obtained, and the change law with time of beams mid-span deflection and steel stress were analyzed, and then, the influence of prestressed steel wire stress variation and prestressed steel wires number and timber creep on total pre-tension value and long-term load were obtained.Third, the short-term damage test was conducted on group A & B & C, after the long-term loading test. Compared the beam ultimate load without long-term loading, under long-term loading without deformation recovery, under long-term loading with deformation recovery to initial loading state, the influence of creep and prestressed control on short-term test performance were analyzed.Finally, a short-term rigidity formula and a long-term rigidity proposed formula was summarized through theoretical deduction, long-term deflection of prestressed gluing bamboo-lumber beams obtained. |
