Flexural Stiffness And Bending Capacity Of Frame Composite Slim Beam With Deep Deck

With the steel beam encased in the concrete slabs, the bonding force between in the steel-concrete composite slim beam guarantees that the two materials are working corporately as well as ultimately developing their own mechanical capacity. The slim beam systems have many advantages, such as minimizing floor depths, good fire resistance performance, fast erection and good serviceability, etc. This new type of composite floor has been widely used in some European countries; especially the slim beam with deep deck becomes the present focus in multi-storey steel residential buildings.Many research results have been released on the structural behavior of simply-supported slim beams. However, the slim beams are more applicable as frame beams in multi-story buildings. But the research on the frame slim beam with deep deck is not mature both by theoretical analysis and experiment in China. A simple, convenient and rational design method is urgently needed all over the world.In this dissertation, some full-scale tests, finite element method (FEM) and theoretical analysis are used to investigate the flexural behavior of frame slim beam with deep deck. The main tasks are concentrated on the followings: (1) two frame slim beams, with concrete slab width about 1/8 span, have been designed and tested in order to study the flexural behavior of the beam and the cross-section strain distribution in the different loadings; (2) test specimens have been simulated by FEM, of which the validity and feasibility have been verified by the test results; and the strain / stress distribution has been revealed further. (3) Based on the results above, the formula of calculating the bending capacity in the hogging moment region of the slim beam with deep deck has been proposed; together with the formula in the sagging moment region given by the former researcher, the design method has been derived to calculate the bending capacity of the frame beam, and its rationality has been testified by the test. (4) The results of the tests and the FEM have indicted thatthe sections of the specimens remain flat during the elastic stage. Therefore the classical Euler-Bernoulli theory could be employed and a formula to calculate the flexural stiffness of composite slim beams with deep deck has been proposed by the method of equivalent cross-section and the principle of equivalent stiffness. The feasibility of the formula is certified by the experimental results.Also parameter analysis by FEA has been carried out to study the influence of the floor slab depth, the ratio of reinforcement and the steel beam on loading capacity of the hogging region in slim beam with deep deck. The conclusion is obtained that concrete in the deep deck resists little load and its stress is low, which provide basis to simplify the calculation model and improve the shape of the MMR-238 deck which is used in China nowadays. All of these will promote the study on new type of the slim beam that is more practical and more efficient.