Research On Ultra-High Toughness Cementitious Composites And Reactive Powder Concrete Slabs Under Blast Loading

The explosion accidents seriously threaten the safety of human life and property.At present,ordinary concrete is widely used as a building material in protective structures.When subjected to blast loadings,the integral and local damage will occur in the concrete structures because of the brittleness of ordinary concrete.The blast resistant performance of concrete structures can be improved based on materials and structures.One method is to add the fibers into the cementitious composites to form fiber reinforced cementitious composites(FRCC),and another one is to design the functionally graded structures.This study concentrates on two types of FRCC,one is the ultra-high toughness cementitious composite(UHTCC)which displays excellent strain hardening properties with ultimate strain over 3.0 %,and another one is the reactive powder concrete(RPC)which shows high compressive strength over 120 MPa.This study employs the experimental,numerical and theoretical methods to study the blast performance of UHTCC,RPC and the functionally-graded panels(RPC/UHTCC).The main researches and conclusions are listed as follows:(1)Studying the blast resistant performance of UHTCC.(i)Calibrating the parameters of K&C model for UHTCC under blast loadings,based on the available experimental data.And providing suitable parameters for K&C model in numerical simulations of UHTCC under blast loadings.(ii)Conducting blast tests on UHTCC slabs with different dimensions and the results shows that UHTCC presents excellent blast resistant performance than ordinary concrete.Discussing the applicability of the empirical formulae for predicting the failure modes of UHTCC slabs after blat tests finding that the empirical formulae underestimate the blast resistance of UHTCC.Obtaining the relationships between the residual load-carrying capacity and the scaled distance.(iii)Employing the structured and unstructured discretizations to simulate the dynamic response of UHTCC slabs under detonations and discussing the accuracy of two types of discretizations.Using the Polynomial Chaos Expansions(PCE)model and the Sobol' sensitivity indices to conduct uncertainty analysis on the relevant parameters of UHTCC,and the results show the maximum failure strain of UHTCC mainly contributes the effect on the cratering area and maximum deflection of the mid-span.(iv)Establishing the Single-Degree-ofFreedom(SDOF)model for UHTCC flexural slabs,using the numerical results to verifying the accuracy of SDOF and employing SDOF to obtain the Pressure-Impulse(P-I)curves for UHTCC slabs.Analyzing the influence of relevant parameters of UHTCC slab on the P-I curves,obtaining the calculating method of UHTCC flexural failure modes and providing the designation methods of UHTCC for protective engineering.(2)Studying the blast resistant performance of RPC.(i)Conducting the quasi-static and dynamic splitting tests on RPC.And obtaining the relationship between the tensile dynamic impact factor and strain rate.(ii)Conducting blast tests on RPC square slabs.Using the experimental results to verify the calibrated parameters of K&C model for RPC.(iii)Establishing the Single-Degree-of-Freedom(SDOF)model for RPC flexural slabs,using the numerical results to verifying the accuracy of SDOF,and employing SDOF to obtain the Pressure-Impulse(P-I)curves for RPC slabs.Analyzing the influence of relative parameters of RPC slab on the P-I curves,obtaining the calculating method of RPC flexural failure modes and providing the designation methods of RPC for protective engineering.(3)Exploring the blast resistant performance of functionally-graded slabs.(i)Designing a type of functionally-graded panel composited by UHTCC and RPC,and the results show that the functionally-graded slab displays excellent energy absorption property.(ii)Using the experimental results verify the numerical model.And employing the verified numerical model to investigate the thickness ratio of UHTCC to RPC on the blast resistant performance of functionally-graded slab,analyzing the feasibility of functionally-graded panel and providing a reference for protective engineering.