Clay brick masonry unit(CBMU) walls are widely used in building structures,and its damage and protection under explosion loads have been a matter of concern in the field of engineering protection.In this paper,a serie...Clay brick masonry unit(CBMU) walls are widely used in building structures,and its damage and protection under explosion loads have been a matter of concern in the field of engineering protection.In this paper,a series of full-scale experiments of the response characteristics of 24 cm CMBU walls unreinforced and reinforced with polyurea elastomer subjected to blast loading were carried out.Through setting 5.0 kg TNT charges at different stand-off distances,the damage characteristics of masonry walls at different scaled distances were obtained.The reinforcement effect of different polyurea coating thicknesses and methods on the blast resistance performance of masonry walls under single and repeated loads were also explored.Five failure grades were summarized according to the dynamic response features of masonry walls.Based on the stress wave propagation pattern in multi-media composite structures,the internal stress distribution of masonry walls were analyzed,and the division basis of the masonry walls’ failure grades was then quantified.Combined with Scanning Electron Microscope(SEM)images,the deformation characteristics of soft and hard segments of polyurea and effects of detonation products on microstructures were revealed respectively,which provides an important reference for the design and application of polyurea in the blast resistance of clay brick masonry walls.展开更多
This study investigates a kind of masonry consisting of clay-fired brick(f_(c)=10 MPa;r=1:38 g/cm^(3))and mortar(f_(c)=10 MPa;r=1:8 g/cm^(3)).Clay-fired brick masonry connotes a traditional construction material of ol...This study investigates a kind of masonry consisting of clay-fired brick(f_(c)=10 MPa;r=1:38 g/cm^(3))and mortar(f_(c)=10 MPa;r=1:8 g/cm^(3)).Clay-fired brick masonry connotes a traditional construction material of old architecture and public buildings.We carried out penetration experiments in which four clay-fired brick walls employing two different patterns were subjected to impact from small high-speed projectile,i.e.12.7 mm armor-piercing explosive incendiary projectile and material tests in which the static and dynamic compressive strengths of clay-fired brick and mortar were determined by quasi-static and SHPB(Split Hopkinson Pressure Bar)tests.The experimental data include hit and exit velocities,damage configuration of clay brick masonry and mechanical properties of material at low and high strain rates,though which influence of thickness and bonding patterns of wall on kinetic loss of bullet,the damage patterns of masonry observed experimentally and dynamic increase of material strengths are analyzed.To keep minimum boundary inconsistency with reality,full 3D detailed finite element model consisting of two different material is established.Sharing common nodes and employing automatic tiebreak contact are combined to reduce computational time usage of large-scale model.For description of clay-fired brick and mortar RiedeleHiermaiereThoma(RHT)material model is employed.Material parameter set is derived based on experimental data,available literature and engineering assumptions.The numerical simulations study the mesh resolution dependency of material model,reproduce the crucial phenomena of masonry in experiment acceptably and offer more time-resolved insight into motion of bullet in the process of penetration.The feasibility of means of constructing finite element model and applying RHT model to the masonry herein and analogous constructions is explored through numerical investigation.展开更多
To investigate the causes qf cracks in multistory masonry buildings, the effect of vertical load difference on cracking behaviors was investigated experimentally by testing and measuring the displacements at the testi...To investigate the causes qf cracks in multistory masonry buildings, the effect of vertical load difference on cracking behaviors was investigated experimentally by testing and measuring the displacements at the testing points of a large sized real masonry U-shaped model. Additionally, the cracking behaviors in U-shaped model were analyzed with shear stress and numerical simulated with ANSYS software. The experimental results show that the deformation increases with the increase of the vertical load. The vertical load results in different deformation between the bearing wall and non-bearing wall, which leads to cracking on the non-beating wall. The rapid deformation happens at 160 kN and cracks occur firstly at the top section of non-bearing wall near to the bearing wall. New cracks are observed and the previous cracks are enlarged and developed with the increase of vertical load. The maximum crack opening reaches 12 mm, and the non-bearing wall is about to collapse when the vertical load arrives at 380 kN. Theoretical analysis indicates that the shear stress reaches the maximum value at the top section of the non-bearing wall, and thus cracks tend to happen at the top section of the non-bearing wall. Numerical simulation results about the cracking behaviors are in good agreement with experiments results.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
To establish bonding stress—slip constitutive model between bars and grout concrete,13 test specimens were employed to study the bonding behavior and the force transfer of bars adhered to grout concrete. The bonding ...To establish bonding stress—slip constitutive model between bars and grout concrete,13 test specimens were employed to study the bonding behavior and the force transfer of bars adhered to grout concrete. The bonding stress development of bars adhered to grout concrete was analyzed. The local bonding stress—slip curve was obtained. Based on the test results,a new bonding stress— slip constitutive model between bars and grout concrete was proposed. The results show that the maximum bonding stress is not influenced by the bar bond length,but it is strengthened when the splitting strength of grout concrete is increased. The model matches the experimental results well,and the regressing coefficient equals 1.7.展开更多
基金supported by the National Natural Science Foundation of China nos.51978660。
文摘Clay brick masonry unit(CBMU) walls are widely used in building structures,and its damage and protection under explosion loads have been a matter of concern in the field of engineering protection.In this paper,a series of full-scale experiments of the response characteristics of 24 cm CMBU walls unreinforced and reinforced with polyurea elastomer subjected to blast loading were carried out.Through setting 5.0 kg TNT charges at different stand-off distances,the damage characteristics of masonry walls at different scaled distances were obtained.The reinforcement effect of different polyurea coating thicknesses and methods on the blast resistance performance of masonry walls under single and repeated loads were also explored.Five failure grades were summarized according to the dynamic response features of masonry walls.Based on the stress wave propagation pattern in multi-media composite structures,the internal stress distribution of masonry walls were analyzed,and the division basis of the masonry walls’ failure grades was then quantified.Combined with Scanning Electron Microscope(SEM)images,the deformation characteristics of soft and hard segments of polyurea and effects of detonation products on microstructures were revealed respectively,which provides an important reference for the design and application of polyurea in the blast resistance of clay brick masonry walls.
基金The work presented in this paper is funded by Opening Project of Science and Technology on Transient Impact Laboratory(Grant No.614260601010517).
文摘This study investigates a kind of masonry consisting of clay-fired brick(f_(c)=10 MPa;r=1:38 g/cm^(3))and mortar(f_(c)=10 MPa;r=1:8 g/cm^(3)).Clay-fired brick masonry connotes a traditional construction material of old architecture and public buildings.We carried out penetration experiments in which four clay-fired brick walls employing two different patterns were subjected to impact from small high-speed projectile,i.e.12.7 mm armor-piercing explosive incendiary projectile and material tests in which the static and dynamic compressive strengths of clay-fired brick and mortar were determined by quasi-static and SHPB(Split Hopkinson Pressure Bar)tests.The experimental data include hit and exit velocities,damage configuration of clay brick masonry and mechanical properties of material at low and high strain rates,though which influence of thickness and bonding patterns of wall on kinetic loss of bullet,the damage patterns of masonry observed experimentally and dynamic increase of material strengths are analyzed.To keep minimum boundary inconsistency with reality,full 3D detailed finite element model consisting of two different material is established.Sharing common nodes and employing automatic tiebreak contact are combined to reduce computational time usage of large-scale model.For description of clay-fired brick and mortar RiedeleHiermaiereThoma(RHT)material model is employed.Material parameter set is derived based on experimental data,available literature and engineering assumptions.The numerical simulations study the mesh resolution dependency of material model,reproduce the crucial phenomena of masonry in experiment acceptably and offer more time-resolved insight into motion of bullet in the process of penetration.The feasibility of means of constructing finite element model and applying RHT model to the masonry herein and analogous constructions is explored through numerical investigation.
基金Project(50778067) supported by the National Natural Science Foundation of China
文摘To investigate the causes qf cracks in multistory masonry buildings, the effect of vertical load difference on cracking behaviors was investigated experimentally by testing and measuring the displacements at the testing points of a large sized real masonry U-shaped model. Additionally, the cracking behaviors in U-shaped model were analyzed with shear stress and numerical simulated with ANSYS software. The experimental results show that the deformation increases with the increase of the vertical load. The vertical load results in different deformation between the bearing wall and non-bearing wall, which leads to cracking on the non-beating wall. The rapid deformation happens at 160 kN and cracks occur firstly at the top section of non-bearing wall near to the bearing wall. New cracks are observed and the previous cracks are enlarged and developed with the increase of vertical load. The maximum crack opening reaches 12 mm, and the non-bearing wall is about to collapse when the vertical load arrives at 380 kN. Theoretical analysis indicates that the shear stress reaches the maximum value at the top section of the non-bearing wall, and thus cracks tend to happen at the top section of the non-bearing wall. Numerical simulation results about the cracking behaviors are in good agreement with experiments results.
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Project(2006BAJ03A01-05) supported by National Science and Technology Pillar Program during the 11th Five-Year Plan Period of ChinaProject (JG200705) supported by Key Laboratory of Structural Engineering of Shenyang Jianzhu University, China
文摘To establish bonding stress—slip constitutive model between bars and grout concrete,13 test specimens were employed to study the bonding behavior and the force transfer of bars adhered to grout concrete. The bonding stress development of bars adhered to grout concrete was analyzed. The local bonding stress—slip curve was obtained. Based on the test results,a new bonding stress— slip constitutive model between bars and grout concrete was proposed. The results show that the maximum bonding stress is not influenced by the bar bond length,but it is strengthened when the splitting strength of grout concrete is increased. The model matches the experimental results well,and the regressing coefficient equals 1.7.
