To promote the application of green renewable materials in concrete composite slabs(CCSs)and study the flexural behavior of CCSs with different shapes,the bending performances of three CCSs with a SFRRAC base plate,on...To promote the application of green renewable materials in concrete composite slabs(CCSs)and study the flexural behavior of CCSs with different shapes,the bending performances of three CCSs with a SFRRAC base plate,one cast-in-site concrete slab of ordinary concrete and one CCS of ordinary concrete by steel bar truss(as recommended in the technical specification for precast concrete structures in Chinese)were compared through experiments.The carrying capacity,flexural behaviour and bi-directional mechanical properties of the specimens were systematically analyzed from the failure modes,load-deflection curves,load-bar strain curves,load-slip curves and crack distributions.Results show that the bending failure process of CCSs with a SFRRAC base plate is similar to that of the cast-in-site concrete slab of ordinary concrete and CCS of ordinary concrete by steel bar truss,as all of them went through the plastic phase,elastic plastic phase and failure phase with fully developed cracks and deflection.No sudden breakage or horizontal cracking of the connecting interface between the base plate and concrete topping was observed.The shape of the base plate has a major impact on the bearing capacity of the CCS with the SFRRAC base plate.When calculating the ultimate bearing capacity with the plastic yield line theory,the influence of the base plate shape on the plastic yield line position should be taken into account.展开更多
The recent increase in blast/bombing incidents all over the world has pushed the development of effective strengthening approaches to enhance the blast resistance of existing civil infrastructures.Engineered geopolyme...The recent increase in blast/bombing incidents all over the world has pushed the development of effective strengthening approaches to enhance the blast resistance of existing civil infrastructures.Engineered geopolymer composite(EGC)is a promising material featured by eco-friendly,fast-setting and strain-hardening characteristics for emergent strengthening and construction.However,the fiber optimization for preparing EGC and its protective effect on structural elements under blast scenarios are uncertain.In this study,laboratory tests were firstly conducted to evaluate the effects of fiber types on the properties of EGC in terms of workability,dry shrinkage,and mechanical properties in compression,tension and flexure.The experimental results showed that EGC containing PE fiber exhibited suitable workability,acceptable dry shrinkage and superior mechanical properties compared with other types of fibers.After that,a series of field tests were carried out to evaluate the effectiveness of EGC retrofitting layer on the enhancement of blast performance of typical elements.The tests include autoclaved aerated concrete(AAC)masonry walls subjected to vented gas explosion,reinforced AAC panels subjected to TNT explosion and plain concrete slabs subjected to contact explosion.It was found that EGC could effectively enhance the blast resistance of structural elements in different scenarios.For AAC masonry walls and panels,with the existence of EGC,the integrity of specimens could be maintained,and their deflections and damage were significantly reduced.For plain concrete slabs,the EGC overlay could reduce the diameter and depth of the crater and spallation of specimens.展开更多
Concrete-filled rectangular steel tubular(CFRST)composite truss bridge is a new type of structure composed of a CFRST truss and concrete deck slab.This new type of bridge has the advantages of high structural force-tr...Concrete-filled rectangular steel tubular(CFRST)composite truss bridge is a new type of structure composed of a CFRST truss and concrete deck slab.This new type of bridge has the advantages of high structural force-transferring efficiency,rapid assembly construction speed and excellent total life cycle,which meets the construction concept of green,recyclable and sustainable development.Due to the broad application prospects,experiment on the flexural behavior of CFRST composite truss bridge in the negative moment region was reported by authors previously.This paper thus presents a finite element analysis(FEA)modelling verified by the reported test data to further investigate the detailed analytical behavior of this structure.The structural response and failure mechanism of CFRST composite truss beam in the negative moment region are studied.In addition,the important structural design parameters on the flexural performance of the CFRST composite truss beam are also investigated,including the height to span ratio,the brace-to-chord wall thickness ratio,the reinforcement ratio of steel reinforcements and prestressed tendons and the strength grade of concrete infill in chords.Finally,the reasonable structural design parameters range are proposed for the optimum design of the CFRST composite truss bridge.展开更多
基金The National Natural Science Foundation of China(No.51578446).
文摘To promote the application of green renewable materials in concrete composite slabs(CCSs)and study the flexural behavior of CCSs with different shapes,the bending performances of three CCSs with a SFRRAC base plate,one cast-in-site concrete slab of ordinary concrete and one CCS of ordinary concrete by steel bar truss(as recommended in the technical specification for precast concrete structures in Chinese)were compared through experiments.The carrying capacity,flexural behaviour and bi-directional mechanical properties of the specimens were systematically analyzed from the failure modes,load-deflection curves,load-bar strain curves,load-slip curves and crack distributions.Results show that the bending failure process of CCSs with a SFRRAC base plate is similar to that of the cast-in-site concrete slab of ordinary concrete and CCS of ordinary concrete by steel bar truss,as all of them went through the plastic phase,elastic plastic phase and failure phase with fully developed cracks and deflection.No sudden breakage or horizontal cracking of the connecting interface between the base plate and concrete topping was observed.The shape of the base plate has a major impact on the bearing capacity of the CCS with the SFRRAC base plate.When calculating the ultimate bearing capacity with the plastic yield line theory,the influence of the base plate shape on the plastic yield line position should be taken into account.
基金National Natural Science Foundation of China(Grant Nos.51908188 and 51938011).
文摘The recent increase in blast/bombing incidents all over the world has pushed the development of effective strengthening approaches to enhance the blast resistance of existing civil infrastructures.Engineered geopolymer composite(EGC)is a promising material featured by eco-friendly,fast-setting and strain-hardening characteristics for emergent strengthening and construction.However,the fiber optimization for preparing EGC and its protective effect on structural elements under blast scenarios are uncertain.In this study,laboratory tests were firstly conducted to evaluate the effects of fiber types on the properties of EGC in terms of workability,dry shrinkage,and mechanical properties in compression,tension and flexure.The experimental results showed that EGC containing PE fiber exhibited suitable workability,acceptable dry shrinkage and superior mechanical properties compared with other types of fibers.After that,a series of field tests were carried out to evaluate the effectiveness of EGC retrofitting layer on the enhancement of blast performance of typical elements.The tests include autoclaved aerated concrete(AAC)masonry walls subjected to vented gas explosion,reinforced AAC panels subjected to TNT explosion and plain concrete slabs subjected to contact explosion.It was found that EGC could effectively enhance the blast resistance of structural elements in different scenarios.For AAC masonry walls and panels,with the existence of EGC,the integrity of specimens could be maintained,and their deflections and damage were significantly reduced.For plain concrete slabs,the EGC overlay could reduce the diameter and depth of the crater and spallation of specimens.
基金sponsored by the National Natural Science Foundation of China(No.52008026)Natural Science Basic Research Program of Shaanxi(No.2021JQ-272)the Fundamental Research Funds for the Central Universities(No.300102219310,No.300102211303)。
文摘Concrete-filled rectangular steel tubular(CFRST)composite truss bridge is a new type of structure composed of a CFRST truss and concrete deck slab.This new type of bridge has the advantages of high structural force-transferring efficiency,rapid assembly construction speed and excellent total life cycle,which meets the construction concept of green,recyclable and sustainable development.Due to the broad application prospects,experiment on the flexural behavior of CFRST composite truss bridge in the negative moment region was reported by authors previously.This paper thus presents a finite element analysis(FEA)modelling verified by the reported test data to further investigate the detailed analytical behavior of this structure.The structural response and failure mechanism of CFRST composite truss beam in the negative moment region are studied.In addition,the important structural design parameters on the flexural performance of the CFRST composite truss beam are also investigated,including the height to span ratio,the brace-to-chord wall thickness ratio,the reinforcement ratio of steel reinforcements and prestressed tendons and the strength grade of concrete infill in chords.Finally,the reasonable structural design parameters range are proposed for the optimum design of the CFRST composite truss bridge.
