Improved concept models for straight thin-walled columns with box cross section

This paper focuses on developing improved concept models for straight thin-walled box sectional columns which can better predict the peak crushing force that occurs during crashworthiness analyses. We develop a nonlinear translational spring based on previous research and apply such a spring element to build the enhanced concept models. The work presented in this article is developed on the basis of the publication of the author (Liu and Day, 2006b) and has been applied in a crashworthiness design issue, which is presented by the author in another paper (Liu, 2008).

ANALYTICAL SOLUTION OF RESTRAINED TORSIONAL STRESSES AND DISPLACEMENT FOR RECTANGULAR- SECTION BOX BAR WITH HONTYCOMB CORE

Differential equation of restrained torsion for rectangular-section box bar with honeycomb core was established and solved by using the method of undetermined function.Non-dimension normal stress, shear stress acting in the faceplate and shear stress acting in the honeycomb-core and warping displacement were deduced. Numerical analysis shows the normal stress attenuates quickly along x-axis. Normal stress acting on the cross section at a distance of 20 h from the fixed end is only one per cent of that acting on the fixed end.

Unified expression for failure of reinforced concrete members in bridge

Reinforced concrete structural elements with box section are commonly used in the horizontal and vertical structure of bridges. The reinforced concrete structure in bridge often failed under the combined forces of bending, axial load, shear and torsion caused by wind and earthquake. It is very important to study the mechanism of RC box section structures subjected to a combi-nation of forces. A theoretical study and deduction of the unified expression for failure of reinforced concrete members with box section under combined bending, shear, axial force and torsion were carried out with stress equilibrium assumption. Comparison of theoretical analysis results with experimental results showed that the unified expression for failure of reinforced concrete members with box section can be used for static calculation of such structure members.

New Unified Failure Model on Evenly Distributed Reinforced Concrete Members with Box Section

It is urgently needed to describe the structural collapse process under extreme conditions to survive people.For reinforced concrete structures it is still a difficulty to describe the failure of reinforced concrete members under complex internal force combination,such as under axial forces,bending moment,shear forces, and torsion working together.In this paper,based on the traditional Nielsen model,a new unified failure model on reinforcement evenly distributed concrete members with box section under combined forces is introduced.The advantages of the proposed new model are to consider the dowel actions of reinforcements and reasonably to consider of the shear carrying capacity of concrete,especially when compression stress of concrete is in a high value.Finally,the theoretical results of the new model are compared with a series of experimental results of box section members.The comparison has verified that the new model is more accurate and feasible for the design and calculation of box section members.

Advanced Unified Failure Model on Uniformly Reinforced Concrete Box Section Members

Based on the traditional Nielsen model,a unified failure model on the uniformly reinforced concrete box section members under combined forces was introduced by Luo and Liu.One of their contributions is adjustment of the shear carrying capacity of concrete at the member failure surface.In the unified failure model,the comparison with the experimental results verified this adjustment.Nevertheless,it should be pointed out that the adjustment factor of shear carrying capacity at member failure surface for the reinforced concrete members in the unified failure model is a fixed adjustment constant for all experiment data,which is basically determined by curve fitting.However,the adjustment factor should vary with the normal stress at the member failure surface.In this paper,an advanced theoretical model is introduced,in which the adjustment factor of shear carrying capacity at failure surface is a variable related to the normal stress at failure surface.Furthermore,the advanced unified failure model on the uniformly reinforced concrete box section member can still be expressed in a simple form.Finally,the comparison with several groups of test data has verified that this advanced model is more accurate and feasible to be used in design.