Pedagogical application of discrete element simulation to brick masonry in uniaxial and localized compression
[Objective]Masonry architecture combines science and art,promoting architectural diversity and culture.The requirement of green and low-carbonization of new town construction provides a new opportunity for developing masonry structures.Masonry structure is an essential professional course in civil engineering education,with the compression of unreinforced masonry being an important part of this course.Masonry is a material that combines brick and mortar.Illustrating masonry failure subjected to compression can help students comprehend the concept of the stress contribution of combined materials,which is vital in the design and reinforcement of masonry structures.[Methods]Discrete element simulation has become an essential supplement to practical teaching and has been increasingly used because of its economy,reproducibility,whole-process illustration,and ability to obtain micromechanical data.To facilitate students'comprehension of the contribution of brick and mortar to bearing external forces,we established brick and mortar clusters and then simulated brick masonry using the discrete element method.Uniaxial and localized compression were conducted on the numerical brick masonry,with the stress-strain relationship,masonry failure mode,bond contact breakage,and the contribution of contact forces to stress analyzed.[Results]The numerical simulation replicates the failure modes of masonry and the corresponding stress-strain relationships under compression.When the masonry is uniaxially and locally compressed,the axial stress reaches its peak value and decreases rapidly,followed by a slow decrease.When the bond strength of the mortar is 30 MPa,under uniaxial compression,the mortar in horizontal and vertical joints is first damaged,subsequent brick-brick bond breakages lead to the splitting of the bricks,and the cracks continue to expand,causing the blocks to break.Thus,many blocks are extruded,and a diagonal shear band appears.In localized compression,failure occurs primarily within a depth range of twice the compression width.Obvious cracks develop in the weak zones on both sides of the compression zone,and the width of the cracks increases rapidly and extends vertically downward.In uniaxial and localized compression,mortar-mortar and brick-mortar bonds break first before reaching the peak stress.These bonds break quickly at the peak stress,while brick-brick bonds only begin to break quickly after the peak stress.The mortar primarily serves to connect the bricks and does not bear the external forces directly.For brick-brick contacts,brick-mortar contacts,and mortar-mortar contacts,the normal contact forces contribute more than the tangential forces to the axial stress.[Conclusions]This study included the introduction of discrete element modeling,uniaxial and localized loading,variations in the number of bonds,and the contribution of contacts to the axial stress.A pedagogical application of these findings was also explored.By combining macro-and microanalysis,students can comprehend that the macromechanical performance of masonry is influenced by the microstructure and micromechanics of the bricks and mortar.They can also recognize the advantages and disadvantages of the discrete element simulation method.Pedagogical application can enhance students'understanding of the mechanism of force transmission and the strength of masonry.This result can further improve students'ability to conceptualize masonry structure design and reinforcement.
brick masonryuniaxial compressionlocalized compressiondiscrete element methodvirtual simulation
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