某橋梁樁基礎(chǔ)設(shè)計(jì)計(jì)算

1、某橋梁樁基礎(chǔ)設(shè)計(jì)計(jì)算第一章樁基礎(chǔ)設(shè)計(jì)一、設(shè)計(jì)資料1地址及水文河床土質(zhì)：從地面（河床）至標(biāo)高32.5m為軟塑粘土，以下為密實(shí)粗 砂，深度達(dá)30m；河床標(biāo)高為40.5m, 一般沖刷線標(biāo)高為38.5m,最大沖 刷線為35.2m,常水位42.5m。2、土質(zhì)指標(biāo)表一、土質(zhì)指標(biāo)3、樁、承臺(tái)尺寸與材料承臺(tái)尺寸：7.0mx4.5mx2.0mo擬定采用四根樁，設(shè)計(jì)直徑1.0mo 樁身混凝土用20號(hào)，其受壓彈性模量eh=2.6x104mpa4、荷載情況上部為等跨25m的預(yù)應(yīng)力梁橋，混凝土橋墩，承臺(tái)頂面上縱橋向荷載 為：恒載及一孔活載時(shí)：?n0?56594kn、?h00?2988kn、?m0?3847.7kn?m

2、1.0m）自重每延米為：恒載及二孔活 載時(shí)：?n?6498.2kno樁（直徑q?1.024?15?11.78kn/m故，作用在承臺(tái)底面中心的荷載力為:?n?5659.4?(7.0?4.5?2.0?25)?7234.4kn?h?298.8kn?m?3847.7?298.8?2.0?4445.3kn恒載及二孔活載時(shí)：?n?64982?(70?45?20?25)?80734kn樁基礎(chǔ)采用沖抓錐鉆孔灌注樁 基礎(chǔ)，為摩擦樁二、單樁容許承載力的確定根據(jù)公路橋涵地基與基礎(chǔ)設(shè)計(jì)規(guī)范中確定單樁容許承載力的經(jīng)驗(yàn) 公式，初步反算樁的長(zhǎng)度，設(shè)該樁埋入最大沖刷線以下深度為h, 般沖 刷線以下深度1為 h3,則:nh?p

3、?u?li?i?moa?o?k2?2(h2?3)2當(dāng)兩跨活載時(shí)：8073.21nh?3.3?11.78?11.78h 42計(jì)算p時(shí)取以下數(shù)據(jù)：樁的設(shè)計(jì)樁徑lom,沖抓錐成孔直徑為1.15m,樁周長(zhǎng)u?1.15?3.6m,a?124m0?0.9,k2?6.0,?0?550kpaz?2?12kn/m2?0.485m 乙？0.7?l?40kpa,?2?120kpa, lp?3.16?2.7?40?(h?2.7)?120?0.70?0.9?0.785?2 550?6.0?12?(h?3.3?3)?nk?2057.17?5.89 ?h?8.78m現(xiàn)取h=9m,樁底標(biāo)高為26.2m。樁的軸向承載力符合要求

4、。具休見(jiàn)如圖1所示。縱橋向斷血橫橋向斷面三、樁頂及最大沖刷線處荷載pi、qi、mi、mo、qo、po 一、參 數(shù)計(jì)算1、樁的計(jì)算寬度blbl?kj?k0?k?d?0.9?(d?l)k?0.9?(l?l)k?1.8k 又：ll?1.5m:hl?3(d?l)?6m:n?2:b?0.6 故：l?b?lll?0.61.5k?b?0.6?0.7670.6hl0.66?bl?0.99?0.767?1.382、樁的變形系數(shù)？:?mlhl?m2(2hl?h2)h28?103?2.7?25?103?(2?2.7?1.3)?1.3m?2hm42?17.25?103kn/m3e?0.67ek?0.67?2.6?10

5、kn/ml?32?d464?0.0491m4?l?0.489m樁在最大沖刷線以下深度h=9m,其計(jì)算長(zhǎng)度為：?h?0.489?9?4.401?2.5 故按彈性樁計(jì)算。3、樁頂剛度系數(shù)?1、？2、?3、?4值計(jì)算l?d2io?3.3m;h?9m;?;a?o.785m2c0?10m0?10?25?103?2.5?105kn/m3 a?按樁中心距計(jì)算面積，001?aec0a0?4?2.52?4.91m2 ?1?13.3?91?1?0.785?2.6?1072.5?105?4.91 ?8.355?105?0.977ei已知：?h?0.489?9?4.401?4,取用 4。0?10?0.489?3.3?

6、1.614 由已知資料和查附表得：xq?0.262564;xm?0.448403;?m?1.063181 ?q?3elxq?0.031ei、?m?2elxm?0.107ek?m?ei?m?0.520ei4、計(jì)算承臺(tái)底面原點(diǎn)o處位移?0、b0、?0n7234.41851.42b0?n?14?0.977eiein?4?l?xi2?4?0.50ei?0.977ei?4?1.252?8.185eii?lmn ?2?4?0.031ei?0.124ein ?3?4?0.107ei?0.429ei(n?3)2?(0.429ei)2?0.184(ei)2 所以:?0?(n?4?l?xi2)h?n?3mi?lm

7、n ?2(n?4?l?x)?(n?3)28.185ei?298.8?0.429ei?4445.352299.66?20.124ei?8.185ei?0.184(ei)ei ?0?n?2m?n?3hn ?2(n?4?l?x)?(n?3)2ii?lm2?0.124ei?4445.3?0.429ei?298.8820.80 ?20.124ei?8.185ei?0.184(ei)ei<二>計(jì)算作用在每根樁頂上的作用力豎向力：pi qi mio1851.42820.80pi?i(b0?xi?0)?0.977ei?1.25?eiei2810.87kn ?806.33kn水平力：

8、5299.66820.80qi?2?0?m?0?0.031ei?0.107ei?eiei?74.7kn彎矩：820.805299.66mi?4?0?m?0?0.520臼？0107ei?eiei?141.50kn?m校核：nqinii?4?74.7?298.8kn?h?298.8kn i?xp?nmi?l?2?(2810.87?806.33)?1.25?4?(?141.50) ?4445.3knm?m?4445.3knm?npi?lni?2?(2810.87?806.33)?7234.4kn?m?7234.4kn<三>計(jì)算最大沖刷線處樁身彎矩mo水平力qo及軸向力po

9、om0?mi?qli0?141.50?74.7?3.3?105.00knm q0774.7kn、p0?2810.87?0.785?3.3?15?2849.73kn四、最大彎矩mmax及最大彎矩位置zmax的計(jì)算?0489、?h?0.489?9?4.401 cq?m0q00.489?105.00?0.687 74.7由設(shè)計(jì)規(guī)范查表得：1.043?z?1.043> z?2.132、km?1.972 0.489所以：mmax?m0km?105.00?1.972?207.06knm五、樁頂縱向水平位移驗(yàn)算樁在最大沖刷線處水平位移x0和轉(zhuǎn)角?0：ax?2.44066,bx?l.62100,a?1.

10、62100,b?1.75058q0m0x0?3ax?2bx?ei?ei74.7105?2.44066?1.62100320.489ei0.489ei 符合規(guī)范要求。？2644?10?3m?2.644mm?6mm?0?q0m0a?b?2?ei?ei74.7105?3?(?1.62100)?(?1.75058)?1.027?10rad20.489ei0.489ei3qi074.7?3.33?3x0?1.042?10m?1.042m53ei3?8.588?10?4xm?8.97?10m?0.897m 52ei2?8.588?10所以樁頂縱向水平位移xl?(2.644?1.027?12.3?1.042

11、?0.897)?10?3?15.43?10?15.43mm水平位移容許值?六、樁身截血配筋的計(jì)算<一>、配筋的計(jì)算最大彎矩截面在z=2.132處，次處設(shè)計(jì)最大彎矩為mj設(shè)計(jì)最大彎矩為：?3?2.5cm,符合要求。?207.06knm,hnj?2849.73?2.132?11.78?40?3.61?2.132?22?2708.36kn由截面強(qiáng)度的計(jì)算公式：?h?b2nj?r?ar?rgc?r2?c?s?b?b3nj?eo?mj?r?br?rgd?gr3?c?s取以上兩式的臨界狀態(tài)分析，整理得：rabr?a?eo?rgc?eo?dgr1、計(jì)算偏心距增大系數(shù)現(xiàn)擬定采用20

12、號(hào)鋼筋，i級(jí)鋼筋，ra?llmpa> rg?240mpa207.06nj270.394.0?因?h?4.401?4.0,故樁的計(jì)算長(zhǎng)度 lp?0.5?3.3?50740mm,0.489?長(zhǎng)細(xì)比mjip5740?5.740?7,可不考慮縱向彎矩對(duì)偏心距的影響，取dlooo?lo2、計(jì)算受壓區(qū)高度系數(shù)dlooo?e0?l?76.5?76.5mm r?500mm22設(shè) g=0.9 則 rg?gr?0.90?500?450mmonu?b?r?ar2?brgc?r2?c?s11b?5oo?a76.5o.95o.9522?11?a?5oo?24oc?5oo?240c?765?d?450、1.251.

13、255500b?841.5a?2090000a?45600000c?18360c?108000d現(xiàn)采用試算法列表計(jì)算，見(jiàn)下表:rabr?a?eo?rgc?eo?dgr由計(jì)算表可見(jiàn)，當(dāng)?二0.97時(shí)，計(jì)算縱向力nu與設(shè)計(jì)值nj之比較為合 理，故取?二0.97, ?二0.002726為計(jì)算值。3、計(jì)算所需縱向鋼筋的截面積ag?r2?0.002726?(500)2?2141mm2現(xiàn)選用10d)18, ag混凝土凈保護(hù)層?25.45cm2,布置如圖2所示。20c?60?50mm?25mm 縱向鋼筋間凈距為 256mm>80mm。2鋼筋布置示意圖& it;二>對(duì)截面進(jìn)

14、行強(qiáng)度復(fù)核由前面的計(jì)算結(jié)果?e0?76.5mm,a?60mmjg?450mm,g?0.9 實(shí)際配筋率?4ag?d2ipd?4?25.45?0.01296 2?501在垂直與彎矩作用平血內(nèi) 長(zhǎng)細(xì)比?5.740?7,故縱向彎曲系數(shù)?混凝土截面積為ah?d24?785398mm2,實(shí)際縱向鋼筋面積ag?2545mm2,則在垂直于彎矩作用平面內(nèi)的承載力為：nu?b(l ?craah?l?s?ag)rg11?1?0.95?(?11?785398?240?2545) 1.251.25?7030.137kn?nj?2708kn2、在彎矩作用平血內(nèi)?eo?bra?d?grgara?c?rgrb?ll?d?0.

15、01296?0.9?240?500a?ll?c?0.01296?2405500b?1327.95d?lla?3.110c同樣采用試算法可得，當(dāng)?0.98時(shí)(?e0)?78.99mm,與設(shè)計(jì)的?e0?76.5mm很接近，故取?0.98為計(jì)算值。在彎矩作用平面內(nèi)的承載 力?b?b2nu?raar?rgc?r2?c?s為?0.950.95?11?2.6424?(500)2?240?2.3690?0.007353?(500)2 1.251.25?6327.73kn?nj?2708knmu?b?rabr3?bd?gr2rg?c?s0.950.95?ll?0.3717?(500)3?240?0.6339?

16、0.00 7353?(500)2 1.251.25?484.07knm?mj?207.06knm樁截面符合強(qiáng)度要求。七、承臺(tái)結(jié)構(gòu)設(shè)計(jì)計(jì)算1、承臺(tái)受沖切驗(yàn)算a0xl00?0.565樁邊沖切，計(jì)算沖跨比:0xh0177?0y?a0yh0?25?0.141?0.2,取 0.2 1770.840.84?1.098 計(jì)算沖切系數(shù)：0x?0x?0.20.565?0.2 ?0y0.840.84?2.100 ?0y?0.20.2?0.2 2?0x(bc?a0y)?0y(hc?a0x)?hpfth0取?hp?1.0,則:?2?0.565?(l?0.25)?2.100?(2?1.5)?1.0?1100?1.77

17、?32371.04kn?2810.87kn滿足要求。樁向上沖切，cl?c2?150cm;alx?100cm;aly?0.25cm;所以，?lx?0565;?2y?02 0.560.56?0.7321x 計(jì)算沖切系數(shù)：?lx?0.20.565?0.20.560.56?ly?1.400?ly?0.20.2?0.2取?hp?1.0,所以：alx?lx(c2?)?ly(cl?)?hpfth0220.732?(1.50?0.125)?1.400?(1.50?0.5)?1.0?1100?1.77 ?7767.56kn?2810.87k n滿足要求。3、抗剪承載力計(jì)算alyaxl00?0.565 ax?100cm,ay?25cm,所以，?x?h017725?y?0.141,取 0.2。h?177cn,剪切承載力截面高度 0h0177影響系數(shù)?hs?1.0o ay1.751.75?hsftb0h0?1.0?1100?7?1.77?1.00.2?1.0?19875.63kn?h?298.8kn所以抗剪承載力滿足要求。4、承臺(tái)受彎承載力計(jì)算mmax?my?nixi?2?2810.87?1.50?8432