| 요약2 |
There are four differential movements which impair the masonry walls, that is: 1) Hygroscopic expansion and contraction. 2) Therma expansion and contraction. 3) Defect of construction and design. 4) Poor workmanship. These differential movements, while always caused by the same factors, may occur in different way. When walls are continuously and rigidly, both to each other and to the structural frame, and no provisions are made for predictable and cumulative inovements, there must be cracks in the walls shmost inevitable. As the results of analyzing above mentioned causes, I propose the following factors which minimizing the cracks in the masonry walls.1. Select the proper masonry materials. 1) Use the fire clay masonry units which the water absorption is little, and concrete masonry unit which the moisture content is little. 2) Select the masonry units which the difference of expansion and contraction is not serious to each other. 3) Select the masonry unit which the compressive streength is high. 4) Select the block which the face shell is thick.2. Improve the construction method. 1) The exteror walls should be tied to the frame with flexible anchors which take tension and compression, but no shear, and permit longitudinal and vertical movement between the frame and the wlll. 2) Control joints should be lacated in masonry walls to provide a complete separation in the structre in order to control the differential movements.3. Rationalize the construction and design. 1) Degign the bearing masonry walls above the allowable stress. 2) Decide the bearing wall thickness properly according to the lateral support of wall. 3) Decide the bearing wall length beyond 55 centimeters or 0.3 times of the wall height. 4) Locate the bearing walls uniformly. 5) Reinforce the bearing walls with bars, where crack is possible. 6) Design the foundation in order not to accour unequal settlement. 7) Use the joint reinforcement. 8) Use the wall girder or bond heam.4. Improve the workmanship 1) Wet the masonry unit properly. 2) Propertion and mix the mortar satisfactory. 3) Lay the masonry units with face shell mortar bedding. 4) Fill the mortar fully to the horizental and vertical joints. |