| What are         Horizontal Bands Necessary in Masonry Buildings?         Role of Horizontal Bands Horizontal bands are the most important         earthquake-resistant feature in masonry buildings. The bands are         provided to hold a masonry building as a single unit by tying all the         walls together, and are similar to a closed belt provided around         cardboard boxes. There are four types of bands in a typical masonry         building, namely gable band, roof band, lintel band         and plinth band (Figure 1), named after their location in the         building. The lintel band is the most important of all, and needs to be         provided in almost all buildings. The gable band is employed only in         buildings with pitched or sloped roofs. In buildings with flat         reinforced concrete or reinforced brick roofs, the roof band         is not required, because the roof slab also plays the role of a band.         However, in buildings with flat timber or CGI sheet roof, roof band         needs to be provided. In buildings with pitched or sloped roof, the roof         band is very important. Plinth bands are primarily used when there is         concern about uneven settlement of foundation soil. The lintel band ties the walls together and creates a         support for walls loaded along weak direction from walls loaded in         strong direction. This band also reduces the unsupported height of the         walls and thereby improves their stability in the weak direction. During         the 1993 Latur earthquake (Central India), the intensity of shaking in         Killari village was IX on MSK scale. Most masonry houses sustained         partial or complete collapse (Figure 2a). On the other hand, there was         one masonry building in the village, which had a lintel band and it         sustained the shaking very well with hardly any damage (Figure 2b). Design of Lintel Bands During earthquake shaking, the lintel band undergoes         bending and pulling actions (Figure 3). To resist these actions, the         construction of lintel band requires special attention. Bands can be         made of wood (including bamboo splits) or of reinforced concrete (RC)         (Figure 4); the RC bands are the best. The straight lengths of the band         must be properly connected at the wall corners. This will allow the band         to support walls loaded in their weak direction by walls loaded in their         strong direction. Small lengths of wood spacers (in wooden bands) or         steel links (in RC bands) are used to make the straight lengths of wood         runners or steel bars act together. In wooden bands, proper nailing of         straight lengths with spacers is important. Likewise, in RC bands,         adequate anchoring of steel links with steel bars is necessary.          Indian Standards The Indian Standards IS:4326-1993 and IS:13828(1993)         provide sizes and details of the bands. When wooden bands are used, the         cross-section of runners is to be at least 75mm×38mm and of         spacers at least50mm×30mm. When RC bands are used, the minimum         thickness is 75mm, and at least two bars of 8mmdiameter are required,         tied across with steel links of at least 6mm diameter at a spacing of         150 mm centers.q Related Earthquake Tip Tip 5: What are the seismic         effects on structures? Tip12: How brick masonry         houses behave during earthquakes? Tip13: Why masonry buildings         should have simple structural configuration? Resource Material IAEE, (1986), Guidelines for         Earthquake Resistant Non-Engineered Construction, International         Association for Earthquake Engineering, Tokyo, available on         www.nicee.org. IS 4326, (1993), Indian         Standard Code of Practice for Earthquake Resistant Design and         Construction of Buildings, Bureau of Indian Standards, New Delhi. IS 13828, (1993), Indian         Standard Guidelines for Improving Earthquake Resistance of Low-strength         Masonry Buildings, Bureau of Indian Standards, New Delhi.   Authored by:        C.V.R. Murty Indian         Institute of Technology Kanpur, Kanpur, India   Sponsored by:        Building Materials and Technology Promotion Council, New Delhi.           Suggestions/comments may be sent to eqtips@iitk.ac.in
   To see         previous IITK-BMTPC Earthquake Tips, visit www.nicee.org
                                                                                                                         Back to Contents         |