Curvature Ductility of Concrete Element under High Strain-Rates

2012 ◽  
Vol 166-169 ◽  
pp. 2910-2917 ◽  
Author(s):  
Zubair Syed ◽  
Priyan Mendis ◽  
Nelson Lam ◽  
Tuan D. Ngo
Keyword(s):  
Strain Rate ◽  
Material Properties ◽  
Static Load ◽  
High Strain ◽  
Strain Rate Effect ◽  
Rate Effect ◽  
Strain Rates ◽  
Material Models ◽  
Curvature Ductility ◽  
Concrete Elements

Considerable amount of studies on the ductility and flexural behaviour of normal and high strength concrete elements under static load can be found in literature. However, most of the previous theoretical investigations on moment-curvature (M-φ) relationship of concrete elements to calculate curvature ductility and flexural capacity did not take account of the strain-rate effect on the material models. M-φ analysis of concrete elements under dynamic loading are often conducted with material models developed for quasi-static load by applying Dynamic Increase Factors (DIF) to the material properties to reflect the strain-rate effect. Depending on magnitude and duration of applied dynamic load, element stiffness and boundary condition strain-rate varies over the cross section. Thus, the application of DIF to modify peak material properties often fails to reflect the strain-rate effect reliably. The improvement of using material model which incorporated strain-rate in its constitutive equations has been explored in this study. The effects of reinforcement amount, grade and concrete strength on curvature ductility for different strain rates have been studied using material models which have strain-rate effects included in theirs formulation. Based on the parametric study, a simple formula to estimate curvature ductility for concrete elements under explosive loads (high strain-rates) has been proposed.

Study of the Strain Rate Effect on Cold-Reduced Carbon Steel and Aluminium Alloy with Numerical Simulations

2006 ◽  
Vol 532-533 ◽  
pp. 973-976
Author(s):  
Lin Wang ◽  
Tai Chiu Lee ◽  
Luen Chow Chan
Keyword(s):  
Carbon Steel ◽  
Strain Rate ◽  
Strain Path ◽  
Plastic Material ◽  
Strain Rate Effect ◽  
Rate Effect ◽  
Forming Process ◽  
Risk Area ◽  
Sensitive Material ◽  
Simulation Results

In this paper, the effect of strain rate has been considered in the simulation of forming process with a simple form combined into the material law. Quite a few researchers have proposed various hardening laws and strain rate functions to describe the material tensile curve. In this study, the strain rate model Cowper-Symonds is used with anisotropic elasto-plastic material law in the simulation process. The strain path evolution of certain elements, when the strain rate is considered and not, is compared. Two sheet materials, Cold-reduced Carbon Steel (SPCC) JIS G3141 and Aluminum alloy 6112 are used in this study. Two yield criteria, Hill 48 and Hill 90, are applied respectively to improve the accuracy of simulation result. They show different performance when strain rate effect is considered. Strain path of the elements in the fracture risk area of SPCC (JIS G3141) varies much when the strain rate material law is used. There is only little difference of the strain distribution of Al 6112 when the strain rate effect is included and excluded in the material law. The simulation results of material SPCC under two conditions indicate that the strain rate should be considered if the material is the rate-sensitive material, which provides more accurate simulation results.

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