Earthquake
Figure 5.19 The mortar in unreinforced masonry walls such as these in Iran,1990(A) can easily fail during an earthquake. Oftentimes the entire structure crumbles, leaving a pile of rubble in which survive. Shown in(B) is one of the many masonry homes to collapse during the 1988 Armenia earthquake (M6.9), claiming nearly 25,000 lives.
The failure is called soft-story collapse. Soft-story collapse is a common problem in commercial building where the first floor has considerable open space for parking or retail shopping Generally speaking the most dangerous types of homes are those constructed of unreinforced masonry because they offer very little resistance to lateral shearing motion . In this technique walls are usually constructed of brick or stone bond together with mortar, as opposed to reinforced walls with internal supports of wooden or steel –note that most brick homes in the United States have an internal wooden frame with a brick facade. Although unreinforced masonry walls have great load-bearing capacity, the mortar readily fails during an earthquake, leaving the wall in a weakened state (Figure 5.19) when this occur, continued shaking during an earthquake may cause the entire structure to crumble, crushing its inhabitants some of the highest death tolls from earthquakes have occurred in regions where homes where largely built of stone or brick. For example, most of the deaths in the 1976 Tangshan earthquake were attributed to homes being built with unreinforced masonry walls. Compounding the problem in Tangshan was were asleep in their homes With respect to multistory buildings, many of which are nonresidential, construction usually involves an interior skeleton made of steel-reinforced concrete Under normal conditions the entire weight of the building is easily supported by its vertical columns as shown in Figure 5.20. However, during an earthquake the strong lateral forced will cause the structure to sway. In some cases this
The failure is called soft-story collapse. Soft-story collapse is a common problem in commercial building where the first floor has considerable open space for parking or retail shopping Generally speaking the most dangerous types of homes are those constructed of unreinforced masonry because they offer very little resistance to lateral shearing motion . In this technique walls are usually constructed of brick or stone bond together with mortar, as opposed to reinforced walls with internal supports of wooden or steel –note that most brick homes in the United States have an internal wooden frame with a brick facade. Although unreinforced masonry walls have great load-bearing capacity, the mortar readily fails during an earthquake, leaving the wall in a weakened state (Figure 5.19) when this occur, continued shaking during an earthquake may cause the entire structure to crumble, crushing its inhabitants some of the highest death tolls from earthquakes have occurred in regions where homes where largely built of stone or brick. For example, most of the deaths in the 1976 Tangshan earthquake were attributed to homes being built with unreinforced masonry walls. Compounding the problem in Tangshan was were asleep in their homes With respect to multistory buildings, many of which are nonresidential, construction usually involves an interior skeleton made of steel-reinforced concrete Under normal conditions the entire weight of the building is easily supported by its vertical columns as shown in Figure 5.20. However, during an earthquake the strong lateral forced will cause the structure to sway. In some cases this