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Chapter 7 Seismic Design of Masonry Buildings Chapter 7: Seismic Design of Masonry Buildings 7.1 Introduction 7.2 Considerations after Wenchuan Earthquake 7.3 Design criteria 7.4 Essentials in calculation of masonry buildings 7.5 Details Base shear method n standard value of horizontal seismic action applied on mass i n the seismic shear force of the i-th story ( ) n - d å F 1 G H G H F n EK j 1 j j i i i ＝ ＝ (i n) i å < n j Vi Fj ＝ ＝ 7.4 Essentials in calculation of masonry building 7.4.1 calculation of horizontal seismic action n The base shear method can be used in the seismic design of multi-story masonry buildings a1＝a max a=[h20.2 -h1(T-5Tg)]ama x Tg a=( 2 )h2amax 0.1 0 0.45ama x Tg a h2amax 5Tg T(s) 6.0 T g g Fig.3.8 a Seismic Effect Coefficient Curve FEK max Geq ＝a × e q j n e q j j S D O F : G G M D O F : G G 1 å＝ ＝ ＝ 0.85 FEK 1 Geq ＝a × n additional horizontal seismic action applied at the top additional horizontal seismic coefficient, For penthouse, parapet, and chimney n d Vn n = 3F F F n n EK D = d 7.4 Essentials in calculation of masonry building 7.4.1 calculation of horizontal seismic action G1 Gj Gi n （a）多层砌体结构房屋 （b）计算简图 n层 i层 j层 室内地坪 底层 Gi Gj G1 Hn Hi Hj H1 Gn 1 j i n Calculation Sketch Fj F1 Hi Gj G1 Gi Hn Gn Fi Fi F1 Fj Fn Fn FEK FEK Vi Fn Hj Fi H1 7.4 Essentials in calculation of masonry building 7.4.1 calculation of horizontal seismic action
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7.4.2 Principle for the distribution of horizontal seismic actions n Rigid diaphragms: n such as cast-in-place and precast reinforced concrete floors and roofs, n the distribution may be done in proportion to the equivalent stiffness of the lateral force-resisting members. i m i m i m i m L i i i i i i m m 1 K K A V V V V K A K = å＝ ＝ ＝ i i i m i m 3h Et b K ＝ Aim, ― the area of the section of the wall (m) in story (i) n Flexible diaphragms: n such as wood floors and roofs, n the distribution may be carried out in proportion to the representative values of gravity load （Gim） acting on the floor area（Fim）, braced by the lateral forceresisting members i m i m i i i i G V V V V G i im im i i i q F F q F F = = g g ＝ Fim, ― the area of the part of floor which supported by the wall (m) in story (i) n Semi-rigid diaphragm: n Such as ordinary prefabricated reinforced concrete floors and roofs, n the average value of the results obtained from the abovementioned two methods of distribution may be used. i i i m i i m i m V F F K K 2 1 V ÷ ÷ ø ö ç ç è æ ＝ + 7.4.3 Seismic load-bearing capacity of the crosssection of walls n Walls with ordinary brick or hollow brick n The seismic load-bearing capacity of the cross-section of walls with ordinary brick or hollow brick shall be checked by the following equation n V —— design value of shear force of the wall； n A —— transversal cross-section area of the wall n —— seismic adjusting coefficient for load-bearing capacity n fVE —— Design value of seismic shear strength along the stepped cross section of various types of unit masonry R E f V EA V g £ R E g 7.4.2 Seismic load-bearing capacity of the crosssection of walls n where fV —— Design value of shear strength of unit masonry in non-seismic design n —— Effect coefficient of normal stress of masonry strength and may be taken in accordance with Table 7-5 V E N V f ＝x f x N Type of masonry 0.0 1.0 3.0 5.0 7.0 10.0 12.0 ≧16.0 Ordinary brick or hollow brick 0.80 0.99 1.25 1.47 1.65 1.90 2.05 — Small-size concrete block — 1.23 1.69 2.15 2.57 3.02 3.32 3.92 Table 7-5 Effect coefficient of Normal Stress of Masonry Strength 0 V s /f No s 0 te: is the mean compressive stress on the cross-section of unit masonry, corresponding to the representative value of gravity load N x
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7.4.2 Seismic load-bearing capacity of the cross-section of walls(GB50011-2010) n Ordinary brick or hollow brick walls with horizontal reinforcement n The seismic load-bearing capacity of the cross-section of Ordinary brick or hollow brick walls with horizontal reinforcement shall be checked by the following equation n fy —— design value of tensile strength of the reinforcement； n —— total cross section area of the reinforcement in the vertical cross-section of the wall in a story,its reinforced ratio should be not less than 0.07% and not more than 0.17%; n —— effect coefficient of reinforces and can be taken from table 7.2.7 of GB50010-2010. Ash z s ( ) V E yh sh R E f A f A 1 V s z g £ + 7.4.2 Seismic load-bearing capacity of the crosssection of walls n Walls with small-size concrete blocks n The seismic load-bearing capacity of the cross-section of walls with small-size concrete blocks shall be checked by the following equation n ft ——design value of axial tensile strength of concrete in the core column； n Ac——total area of the core column cross-section； n AS ——total area of cross-section of the reinforcement in the core column； n ——effect coefficient of the core column and may be taken from table 7-7 ( ( ) ) V E t c y S c R E f A 0.3f A 0.05f A 1 V z g £ + + z c Table 7-7 effect coefficient of the core column (GB50011-2010) c z Filled opening ratio ＜0.15 0.15≤ <0.25 0.25≤ ＜ 0.5 ≥0.5 0 1.0 1.10 1.15 r r r r r Note: Filled opening ratio is the ratio of the number of core columns to the total number of openings in blocks n The base shear method may be used in the seismic calculation for brick buildings with framed first one/two stories or inner-frames n Design value of seismic shear force in the longitudinal and the transversal directions in the framed part of brick buildings with framed first one/two stories shall be multiplied by an amplification factor in the range of 1.2~l.5, based on the ratio of lateral drift stiffness of the upper story to that of the framed part. 7.4.3 Essentials in calculation of multi-story masonry building with framed first one/two stories n Design value of seismic shear force in corresponding direction, and can be distributed in proportion of the lateral stiffness of the shear walls. n Seismic action effect of frame columns at first story may be determined by the following method: n Design value of seismic shear force may be determined in proportion of the effective lateral stiffness of all lateral force resisting members. 7.4.3 Essentials in calculation of multi-story masonry building with framed first one/two stories 7.5 Details 7.5.1 Dimensional limitations （GB50011-2010） n The building height (in meter and/or in story) shall not exceed the values in Table 7-1 房屋 类别 最小 抗震 墙厚 度 （mm） 烈度和设计基本地震加速度 6 7 8 9 0.05g 0.10g 0.15g 0.20g 0.30g 0.40g 高 度 层 数 高 度 层 数 高 度 层 数 高 度 层 数 高 度 层 数 高 度 层 数 多层 砌体 结构 普通砖 多孔砖 240 240 21 21 7 7 21 21 7 7 21 18 7 6 18 18 6 6 151 5 5 5 12 9 4 3 多孔砖 190 21 7 18 6 15 5 15 5 15 5 — — 小砌块 190 21 7 21 7 18 6 18 6 15 5 9 3
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n The building height (in meter and/or in story) shall not exceed the values in Table 7-1 房屋 类别 最小 抗震 墙厚 度 （m m） 烈度和设计基本地震加速度 6 7 8 9 0.05g 0.10g 0.15g 0.20g 0.30g 0.40g 高 度 层 数 高 度 层 数 高 度 层 数 高 度 层 数 高 度 层 数 高 度 层 数 底部框 架-抗震墙 砌体房屋 普通砖 多孔砖 240 22 7 22 7 19 6 16 5 — — — — 多孔砖 190 22 7 19 6 16 5 13 4 — — — — 小砌块 190 22 7 22 7 19 6 16 5 — — — — 7.5 Details 7.5.1 Dimensional limitations （GB50011-2010） n The maximum ratio of height to width for a multi-story masonry building shall be in accordance with Tab. 7-3 Ratio 2.5 2.5 2.0 1.5 Intensity 6 7 8 9 7.5 Details 7.5.1 Dimensional limitations （GB50011-2010） n Spacing of seismic transverse shear walls of multi-story masonry buildings shall not exceed the values as set forth in Tab. 7.6 (m) 房屋类别 烈 度 6 7 8 9 多层 砌体 现浇或装配整体式混凝土楼、屋盖 装配式钢筋混凝土楼、屋盖 木楼、屋盖 15 11 9 15 11 9 11 9 4 7 4 — 底框 架-抗 震墙 上部各层 同多层砌体房屋 － 底层或底部两层 18 15 11 － 房屋抗震横墙最大间距（m） 表7.6 7.5 Details 7.5.1 Dimensional limitations （GB50011-2010） n Local dimension limitation of multi-story masonry buildings should not exceed the values in Tab. 7-4 (m) 部位 6度 7度 8度 9 度 承重窗间墙最小宽度 1.0 1.0 1.2 1.5 承重外墙尽端至门窗洞边的 最小距离 1.0 1.0 1.2 1.5 非承重外墙尽端至门窗洞边 的最小距离 1.0 1.0 1.0 1.0 内墙阳角至门窗洞边的最小 距离 1.0 1.0 1.5 2.0 无锚固女儿墙（非出入口处） 的最大高度 0.5 0.5 0.5 0.0 7.5 Details 7.5.1 Dimensional limitations （GB50011-2010） n Constructional measures for multi-story brick buildings n Constructional measures for multi-story block masonry buildings n Constructional measures for the multi-story masonry buildings with frame-shear wall in lower stories 7.5 Details 7.5.2 Constructional measures （GB50011-2010） Constructional measures for multi-story brick buildings n Reinforced concrete constructional columns shall be installed in accordance with the following requirements for multi-story ordinary or hollow brick buildings n locations of constructional columns shall be in accordance with the requirements in Tab.7.3. l of GB 50011-2010 n For multi-story brick buildings with exposed or single-side corridor, the constructional columns shall be installed in accordance with the requirements in Tab. 7.3.1 of GB 50011-2010, based on the building assumed with one more story, and the longitudinal walls on both sides of the single-side corridor shall be treated as exterior walls
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Constructional measures for multi-story brick buildings u For buildings with few transverse walls, such as school buildings and hospitals, constructional columns shall be installed in accordance with the requirements in Clause l or 2 on the above, but the number of stories in Table 7.3.1 of GB 50011-2010 shall be increased by two n Constructional columns of the multi-story ordinary or hollow brick buildings shall comply with the following requirements: u For a constructional column the minimum cross-section may be taken as 240×180 mm u Bricks in the connection of the constructional column and the adjacent walls should be laid with toothing, and 2ф6 tie bars shall be placed at every 500 mm spacing along the height of the wall Reinforcement details for connection of brick walls and constructional column Constructional measures for multi-story brick buildings u Constructional column shall be connected with the ring beam and the longitudinal reinforcement of the constructional column shall be continuous through the ring beam u Foundation may not be installed individually for a constructional column, but the column shall extend 500 mm below the outdoor ground level Reinforcement details for the joint of poured in-situ ring beam and constructional column Constructional measures for multi-story brick buildings n For large rooms with a bay longer than 7.2 m in the intensity of Ⅵ or Ⅶ, 2ф6 tie bars shall be placed at every 500 mm along the height of the wall n For a post-built non-bearing partition wall, 2ф6 bars tied with bearing wall or column shall be arranged along the height of the wall at every 500 mm in spacing n Poured in-situ reinforced concrete ring beams in multistory brick buildings shall be installed in accordance with the following requirements n For brick buildings with precast reinforced concrete, the ring beams shall be installed in accordance with the requirements as set forth in Table7.3.3 of GB 50010-2010 Constructional measures for multi-story brick buildings n For buildings with reliable connection of the poured in-situ or precast monolithic reinforced concrete floors and roof to the brick walls, the ring beams may be ignored. But the slab shall be securely connected with the corresponding constructional columns by means of reinforcement. n For buildings with brick arch floors and roof in the intensity Ⅵ to Ⅶ , the ring beams shall be installed on all walls for each story. n Construction of the poured in-situ reinforced concrete ring beams in multi-story clay brick buildings shall comply with the following requirements. Constructional measures for multi-story brick buildings
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n Ring beams shall be closed or overlapping where interrupted by an opening; ring beams should be installed at the same level as the precast floor slab or close to the bottom of the slab n If no transverse wall exists in the spacing as set forth for ring beams, the reinforcements in the beam or slab joint shall be used in lieu of ring beams n Height of the cross-section of ring beams shall not be less than 120 mm, and the reinforcement shall comply with the Tab. 7.3.4 of GB50011-2010 Constructional measures for multi-story brick buildings Reinforcement details for ring beam Constructional measures for multi-story brick buildings n Reinforced concrete beams or trusses in the floor and roof system shall be connected securely with walls, columns (including constructional columns) or ring beams n Sloping roof trusses shall be connected securely with the ring beam at the top story of a building n Precast balcony shall be connected reliably with the ring beam and the poured in-situ stripe in the floor slab Constructional measures for multi-story brick buildings Constructional measures for multi-story block masonry buildings n For small-size concrete block buildings, reinforced concrete core columns shall be installed in accordance with Tab. 7.4.1 of GB 50011-2010 n Core column in small-size block buildings shall comply with the following constructional requirements: n Cross-section of the core column in small-size concrete block buildings should be not less than 120 mm ×120 mm n Concrete strength grade of the core column shall be taken as Cb20 at least n Vertical inserted reinforcement of the core columns shall pass through the whole wall and be connected with the ring beam of each story n Core column shall extend to a depth of 500 mm below the outdoor surface n the core columns installed for improvement of the seismic shear strength of the wall should be lay out evenly in the wall with spacing not greater than 2m n Poured in-situ reinforced concrete ring beams in small-size block buildings shall be installed in accordance with Table6.12 n Tying mat reinforcement should be placed on the intersection of walls or connection of the core column or constructional column with the wall in small-size block buildings Constructional measures for multi-story block masonry buildings Reinforcement details for core columns and small-size concrete block walls Constructional measures for multi-story block masonry buildings
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Constructional measures for the multi-story masonry buildings with frame-shear wall in lower stories Commonly-used pattern n Reinforced concrete breastsummer of the buildings with frame-shear walls in lower stories should comply with the following requirements n Cross section of beam should have width more than 300mm and height no less than one tenth of the span n Stirrup not less than 8mm with spacing not greater than 200mm n Along the height of the beam lumbar should be laid not less than 2ф14 with spacing not greater than 200mm Constructional measures for the multi-story masonry buildings with frame-shear wall in lower stories Reinforcement details for breastsummer n Material Strength: The strengthen grade of the material for the buildings with lower frame-shear walls, should comply with the following requirements n Grade of concrete for frame-column and seismic shear wall and breast summer should be not less than C30 n Grade of mortar for walls of transition layer should not be less than M10 Constructional measures for the multi-story masonry buildings with frame-shear wall in lower stories n Reinforced concrete constructional columns should be installed in the upper stories of the multi-story masonry building with frame-shear wall in lower stories and shall comply with the following constructional requirements n The locations of constructional columns shall be in accordance with the requirements in Tab.7.3. l of GB 50011-2010 n Cross-section of the core column should be not less than 240 mm ×240 mm not less than 4ф16 in the intensity of Ⅶ n be connected reliably with the ring beams or the in-situ floor Constructional measures for the multi-story masonry buildings with frame-shear wall in lower stories n The floor slabs of the buildings with frame-shear walls in lower stories comply with the following requirements： n The floor slabs of the transition storey should be poured in-situ with thicness not less than 120mm n For other floors if the precast reinforced concrete slabs is used, the poured in-situ ring beam should be used. Constructional measures for the multi-story masonry buildings with frame-shear wall in lower stories
Constructional measures for Constructional measures for the multi-story masonry buildings with the multi-story masonry buildings with frame-shear wall in lower stories frame-shear wall in lower stories .The seismic shear wall in lower stories should comply with .When normal brick is used for seismic shear wall of the the following requirements lower frame-wall building,the constructions should Beams and frame-columns should be laid in circumference comply with the following requirements of the wall to fomm the frame .The thickness of the wall should not be less than The thickness of seismic shear wall plate should not be less than 160mm and not be less than 0.05 times of the clear 240mmand the grade of the mortar should not be less than M10 height of the wall plate The ratio of the longitudinal and transverse reinforcement .28 tie bars shall be arranged at every 300 mm along both should not be less than 0.30%and be two-bank with the frame-column and along the whole length of the spacing not less than 600mm and diameter not less than wall 6mm If the length of the wall is greater than 4m,additional constructional column should be installed in the wall Thank you Please Review this Chapter and Do Excise 4 and/or 5!
n The seismic shear wall in lower stories should comply with the following requirements n Beams and frame-columns should be laid in circumference of the wall to form the frame n The thickness of seismic shear wall plate should not be less than 160mm and not be less than 0.05 times of the clear height of the wall plate n The ratio of the longitudinal and transverse reinforcement both should not be less than 0.30% and be two-bank with spacing not less than 600mm and diameter not less than 6mm Constructional measures for the multi-story masonry buildings with frame-shear wall in lower stories n When normal brick is used for seismic shear wall of the lower frame-wall building, the constructions should comply with the following requirements n The thickness of the wall should not be less than 240mm and the grade of the mortar should not be less than M10 n 2ф8 tie bars shall be arranged at every 300 mm along the frame-column and along the whole length of the wall n If the length of the wall is greater than 4m, additional constructional column should be installed in the wall Constructional measures for the multi-story masonry buildings with frame-shear wall in lower stories Thank you Please Review this Chapter and Do Excise 4 and/or 5 !