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In order to investigate the effects of steel fiber, polyvinyl alcohol (PVA) fiber and mineral powder contnet on permeability resistance of steel-PVA hybrid fiber high performance concrete (HFHPC). The orthogonal experiment was designed to conduct the permeability resistance test of steel-PVA HFHPC, and the test results were analyzed through range analysis, variance analysis and regression analysis. The results show that the influence degree on the impermeability of HFHPC is steel fiber, mineral powder and PVA fiber from high to low. In the range of test level, the optimal horizontal combination of impermeability of concrete specimens is as follows: steel fiber volume fraction of 1.0%, PVA fiber volume fraction of 0.7% and slag powder mass replacement rate 20% . When the steel fiber volume fraction exceeds 1.0%, the impermeability of HFHPC decreases slightly, but it is still higher than that of standard plain concrete. Finally, multiple regression analysis is used to establish the prediction model of HFHPC permeability and steel fiber, PVA fiber and mineral powder. [ABSTRACT FROM AUTHOR]

In order to understand the heavy metal content and health risk level in water of kasrt cave in Libo, Guizhou Province, the concentration of 8 heavy metals in water from 13 caves was analyzed and detected, and the health risk assessment model recommended by US EPA was used to estimate the health hazard risk level of heavy metal pollutants in drinking water. The results showed that the average concentration of heavy metals is Zn>Cr>Cu>As>Ni>Cd>Pb>Hg, which did not exceed the class III water standard of Quality Standard for Ground Water (GB/T 14848-2017). The content of heavy metals in cave water in Libo is generally lower than (or only a little close to) surface water and groundwater outside the cave. Spearman correlation analysis showed that Zn was significant positive correlation between Pb and Cu, Cd was significant positive correlation with Hg, As was significant negative correlation with Cr and Hg. The health risk assessment showed that the mean values of the total health risk of adults and children caused by heavy metals in cave water were Cr>As>Cd>Cu>Hg>Ni>Pb>Zn. The average annual health risk for both adults and children caused by Cr and As (85% of caves) exceed the maximum acceptable risk for the Swedish Environmental Protection Agency, the Dutch Construction Environmental Protection Agency and the Royal Society of the United Kingdom. This indicates that drinking cave water for a long period of time may lead to a certain risk of carcinogenesis. The average contribution rate of Cr and As to the total health risk of adults and children is 99.60%, so Cr and As should be regarded as the priority control and management of pollutants of cave water in Libo. The total health risks of adults and children were 4.80x10-6~3.51x10-5 a-1 and 5.46x10-6~3.97x10-5 a-1, respectively, indicating that children are more sensitive risk receptors than adults, and the control and management of children's drinking water safety should be strengthened. [ABSTRACT FROM AUTHOR]

In order to study the seismic behavior of CFRP-reinforced seismic-damaged joints in composite frame consisting of concrete-filled square steel tubular (CFSST) columns and steel beams, four one half scaled models of exterior joints in composite frame consisting of CFSST columns and steel beams were designed and manufactured. The test consisted of pre-damage loading, rehabilitation with CFRP and destruction tests under lateral cyclic loading. The effectiveness of CFRP-strengthened seismic-damaged joints and the reinforcement effect on different levels of seismic damage were studied. Based on the test data, the hysteretic loops, skeleton curves, the CFRP strain, ductility, dissipative ability, ultimate strength and stiffness degradation, etc. were obtained. Results show that CFRP-strengthened seismic-damaged exterior joints in composite frame consisting of CFSST columns and steel beams meets the strong column-weak beam requirement of seismic design, and the failure modes of all joints are bending failure of beam. The reinforcement with CFRP has a significant on increasing the ultimate capacity and the seismic behaviors of the joints. The study indicates the rehabilitated joints can reach or even exceed the level of their original seismic performances before seismic damage in a certain extent of damage level. [ABSTRACT FROM AUTHOR]

To study the seismic behavior of unsymmetrical steel reinforced concrete column, cyclic loading tests were carried out on 12 columns with T-shaped section steel and 12 columns with L-shaped section steel. The test parameters included shear span ratio, axial compression ratio, stirrup ratio and presence of cross tie. Mechanical process, failure mode, hysteretic characteristics, skeleton curves, ductility and energy dissipation ability were taken into comparison. The result indicates that unsymmetrical steel reinforced concrete column possesses good seismic performance under constant axial compression and cyclic horizontal load. The failure modes include bonding failure, shear-bond failure, shear compression failure and shear-composition failure. Obvious asymmetry phenomenon of positive and negative hysteresis loop are shown. The span ratio has great influence on failure mode and shear-composition failure usually takes place in L-shaped steel section column. With the increase of axial compression ratio, the ductility decreases, which is obvious in L-shaped steel section column. The ductility and bearing capacity of the T-shaped steel section columns are improved greatly with the increase of stirrup ratio, but not obvious for T-shaped steel section column with smaller span ratio. Cross ties can improve bearing capacity, limit strength and stiffness degradation and enhance deformation capacity of L-shape steel section columns clearly. [ABSTRACT FROM AUTHOR]