Study On The Design Method Of Mixed Bearing Wall In Modern Rammed Earth Dwelling

The traditional rammed earth dwelling has advantages of energy conservation,environmental protection and regeneration.In order to take account of the thermal insulation performance and the space utilization ratio of house,plenty of farmers take thick rammed earth as external walls and thin brick as internal walls,which has the characteristic of mixed load-bearing of brick and earth.On this base,the modern rammed earth dwelling which has improvements of material performance and design method is better in safety and durability than the traditional rammed earth dwelling.However,there is still the problem of mixed load-bearing wall with uncertain force,which seriously affects the structural design of the house.Thus,in order to provide reasonable advices for the design of the wall,the load distribution rule of mixed wall under vertical load is researched by finite element analysis.The main contents are as follows:(1)Improvements of modern rammed earth dwelling in material optimization,structural conceptual design,seismic structural measures are introduced and the importance of mix proportion and the principle of modified material are analysed in details.The compressive strength and the elastic modulus of modified mixture with cement,lime and pavement milling material are researched by basic mechanical test so as to provide a reasonable reference for the finite element analysis.(2)The influence law of different factors for the load distribution of mixed wall of brick and earth in “T” and “一” forms under vertical load are researched by ABAQUS.The results show that the elastic modulus of rammed earth wall and the height of ring beam are main factors which affect the load distribution of mixed wall under uniform load.On the basis,the calculation formula of load distribution is derived and its applicability is discussed.(3)In consideration of the dry shrinkage of rammed earth wall,the load redistribution law of mixed wall in “T” form is researched by ABAQUS.The results show that it is effective to control the level of load redistribution by improving the elastic modulus of rammed earth wall,reducing the height of mixed wall or limiting the length of rammed earth wall.Besides,it is suggested that the setting of structural column would be advantageous to ring beam,because it can adjust the complex stress state of beam and improve the local compression of mixed wall.(4)In consideration of the dry shrinkage of rammed earth wall,the whole house without ring beam is researched.The results show that the loading method of two-way slab has the trend of transferring to one-way slab with the development of the dry shrinkage of rammed earth wall.It is suggested that the longitudinal reinforcement should be reinforced,and the distance of reinforcement within local compression area should be encrypted.Besides,there should be certain surplus for the foundation design of brick wall to cope with the load redistribution during the period of dry shrinkage.In summary,the stress state of mixed load-bearing wall of brick and earth in modern rammed earth dwellings has a certain particularity.It is significant to study the load distribution rule of mixed wall before and after shrinkage,which is advantageous to the design of such house.