Research On Calculating And Measuring Methods Of Stress Caused By Shrinkage In Composite Beams

Composite beams can make a better use of properties of both steel and concrete, and highly improve the bearing capacity, stiffness and ductility of structures. But there are still some innate disadvantages in composite structures. Shrinkage and creep of concrete slab may cause complex long-term effects, including stress redistribution in different materials, internal force redistribution in statically indeterminate structures and additional deformation in composite beams.Under normal circumstances, long-term effect in composite beams can cause self-balancing additional internal forces and usually tesion in concrete slabs and compression in steel beams which is a disadvantageous influence in structures. Therefore, it is very important to predict and evaluate the long-term effect reasonably to ensure the security of structures and to improve the veracity of analysis methods. My research aims at finding methods to describe the distribution of shrinkage stress and to measure the shrinkage stress by experiments. Main work and achievements of this article are shown below.(1) Summarizing longterm properties of concrete and calculation methods of these properties by literature investigation.The development of elastic modulus of concrete, the shrinkage of concrete and the creep caused by shrinkage stress are concerned.(2) To simplify the research, choose a simply support composite beam as analytic target. Based on the previous research, the influence of the width of concrete slabs is considered in addition. Subsequently, an improved calculation method is proposed using the concept of effective width in composite structures. Meanwhile, finite element models will be built to verify the veracity of the method and to correct the method if necessary.(3) An example will be calculated using the method above to provide a reference for engineering practice.(4) Designing an experiment to research the measurement of additional internal stress. Because additional internal stress is hard to be measured by traditional measuring methods, it is necessary to find effective method and verify it by experiments and finite element modeling methods.The final objective of the article is to come up with a convenient and effective method to measure the influence of long-term properties of concrete in composite strucures.