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摘要:钢管桩支架现浇施工为桥梁工程重点和难点工程之一。某桥主桥为五跨变截面预应力混凝土连续箱梁,全长823米,桥梁施工支架的搭设对于工程建设结构安全至关重要。本文结合变截面预应力混凝土连续箱梁施工方法和特点,对钢管桩支架结构承载力和稳定性进行计算,给出施工监测和控制要点,可为同类型工程施工提供参考。
关键词:变截面;箱梁大桥;钢管桩;结构计算
1、前言
据统计,每年都有桥梁因为支架的倒塌而产生人员伤亡[1],通常发生事故原因有两个,一是设计荷载不足,安全失效,二是施工管理不到位,工作人员蛮干,导致施工安全事故。桥梁施工支架的施工方法和技术对于工程建设的顺利进行以及结构的安全至关重要。
随着桥梁技术不断发展,变截面大体积预应力混凝土箱梁得到越来越广泛的应用,其设计及施工单位更加重视施工计算和脚手架培训工作。例如李明星[2]结合某市政变截面曲线匝道桥满堂门式支架施工,详细介绍了满堂门式支架的构架方法和稳定性计算。文瑜 谢玮[1].对桥梁施工临时支架倒塌的常见原因进行了分析,对影响支架稳定性的因素和支架稳定性计算方法进行了总结。刘明军,林志军[3]介绍田安大桥主桥拱面部分的梁段安装支架钢管桩的设计计算与施工。希文峰,黄羚[4]根据满堂支架的结构及受力特征,分析了满堂支架荷载计算方法以及立杆、底模、纵向方木、横向方木等主要组成构件的计算模型。
2、工程概况
某桥工程桩号分别为K0+000,终点桩号K2+300,全长2.3km。主桥上部构造:混凝土C55:16293.6m3Ⅰ钢筋606t,Ⅱ钢筋2747t,预应力钢绞线841t。该桥左幅设计为:(4×32m)等截面预应力砼连续箱梁+(58+3×96+58)变截面预应力砼连续箱梁+(3×24)等截面预应力砼连续箱梁+(4×32)等截面预应力砼连续箱梁+(3×32)等截面预应力砼连续箱梁;右幅设计为:(3×32m +24.175m)等截面预应力砼连续箱梁+(58+3×96+58)变截面预应力砼连续箱梁+(25.825+2×27)等截面预应力砼连续箱梁+(4×32)等截面预应力砼连续箱梁+(3×32)等截面预应力砼连续箱梁。
该桥主桥设计为58m+3×96m+58m五跨变截面预应力混凝土连续箱梁。主跨箱梁单“T”共分12段悬臂浇筑,0号梁段长12m,其余1-12号梁分段长为7×300+5×400cm,邊跨、次边跨、中跨合拢段都为2m,边跨现浇段长10m。0号梁段和边跨现浇段采用钢管桩支架现浇施工,主跨T构采用对称挂篮悬臂现浇施工,悬浇最重梁段为1794kN。
3、钢管桩支架计算
主要临时支架破坏形式为失稳破坏,即支架倒塌。倒塌主要是由于支架承受的施工临时荷载时位移变形过大而造成,即几何非线性的影响十分明显。为保证临时支架结构体系,整体稳定性满足要求是设计过程的首要问题。支架现浇方案,采用布架灵活、搭拆方便、承载力大。如图2所示,取单根钢管桩受力进行分析。
![](https://www.soolun.com/img/pic.php?url=data:image/png;base64,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)
图2 单根钢管桩受力示意
Figure 2single steel pipe pile stress
A1断面平均截面积6.45 m2,砼体积26.8 m3,A2断面平均截面积2.47 m2,砼体积10.25 m3,A3断面平均截面积5.81m3,砼体积24.1 m3。通过分析比较,只计算中间钢管桩和两侧钢管桩。依照有关规范[5,6],对荷载作用进行计算。
4.1中间钢管桩计算
中间钢管桩最大平均受力面积A=6.45m2;现浇预应力钢筋砼自重:q1=26KN/m3×26.8 m3=697 KN
模板自重:q2=2.5KN/m2×3.25m×4.15m=33.72KN
振捣砼产生荷载:q3=2.0 KN/m2×3.25m×4.15m=27.0KN
运输、堆放荷载:q4=3.0 KN/m2×3.25m×4.15m=40.46KN
恒载:(q1+q2)×1.2=876.9KN;活载:(q3+q4)×1.4=94.4KN;荷载:恒载+活载=971.3KN
钢管桩结构计算:
钢管桩φ700×8mm的A3钢钢管,自由长度层距4m。
钢管惯性矩:
![](https://www.soolun.com/img/pic.php?url=data:image/png;base64,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)
;截面積:
![](https://www.soolun.com/img/pic.php?url=data:image/png;base64,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)
; 慣性半径
![](https://www.soolun.com/img/pic.php?url=data:image/png;base64,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)
;柔度系数
![](https://www.soolun.com/img/pic.php?url=data:image/png;base64,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)
;
极限柔度
![](https://www.soolun.com/img/pic.php?url=data:image/png;base64,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)
;
![](https://www.soolun.com/img/pic.php?url=data:image/png;base64,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)
λ<λ2,屬于短粗杆(小柔度杆),用经验公式计算F=σcr×A;
F=cr×A=200
![](https://www.soolun.com/img/pic.php?url=data:image/png;base64,R0lGODlhFgALAHcAMSH+GlNvZnR3YXJlOiBNaWNyb3NvZnQgT2ZmaWNlACH5BAEAAAAALAEAAgAUAAcAhQAAAAAAAAAAAwgKDQ0LCgQAAAsGAwMGCw0LCwgDAwoEAAADCAsLCwQABAoLDQ0KCggEAwQIDQMDAwQDCAsLDQ0KCAMABAMAAAAEBAQAAwsICgoGAwQGCg0IBAAABAoICwMGCggECAsKCAMDCAAECg0ICAMAAwQGCwADBAQDAAECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwZgQADAIBgICYWAMnAQOp2IhBGgWDCkhIbj6XxAIkPJgTChVCyOygWTmWo2hwpH2lEWCe2OZ4v4dEAhIiMUCmBCBk0dJEIlAxUmA4hZWwBRjhdgdQsiJwZLTE4KASgpCxRBADs=)
×
![](https://www.soolun.com/img/pic.php?url=data:image/png;base64,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)
=3480KN;安全系数为:
![](https://www.soolun.com/img/pic.php?url=data:image/png;base64,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)
;
中间钢管桩满足施工要求。
4.2两侧钢管桩计算
平均横断面积A=5.81m2。方法同中间钢管桩计算方法,最终得出,安全系数
![](https://www.soolun.com/img/pic.php?url=data:image/png;base64,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)
,中间钢管桩满足施工要求。 4.3縱向分配梁受力计算
通过分析,纵向分配梁最不利位置为中腹板,荷载由六根Ⅰ25b工字钢承担,工字钢间距1.2m。
计算得出恒载:(q1+q2)×1.2=328KN;活载:(q3+q4)×1.4=23.5KN;
荷载:恒载+活载=351.5KN;荷载:q=125.5KN/m
分配梁结构计算:Ⅰ25b悬臂长度2.8m。
惯性矩:
![](https://www.soolun.com/img/pic.php?url=data:image/png;base64,R0lGODlhEQAMAHcAMSH+GlNvZnR3YXJlOiBNaWNyb3NvZnQgT2ZmaWNlACH5BAEAAAAALAEAAgAPAAgAhAAAAAAAAA0IBAMGCwoEAA0LCwgDAwgKDQ0LCgQDCAsLDQgDAAADCAAECgsGAwQIDQ0KCAMAAAECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwUqIAAIQTCIaIoSp+oWxuG6SKKIxVKWzD02M5fjgcrtAj0ATBYUQSJIXzAEADs=)
6×5280cm4=3.168×108mm4;截面抵抗弯矩:W=
![](https://www.soolun.com/img/pic.php?url=data:image/png;base64,R0lGODlhCgANAHcAMSH+GlNvZnR3YXJlOiBNaWNyb3NvZnQgT2ZmaWNlACH5BAEAAAAALAEAAgAHAAkAhAAAAAAAAAgDAA0LCwAAAwgKDQ0LCgQAAw0KCAMDCAsLDQsGAwMGCwgDAwMAAAAABAoLDQECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwECAwUfIAAMQkAUImAcaIokSgosjDw0rfjGKW3jLkfgARGFAAA7)
÷ymax=6×423×cm3=2.54×106mm3
弹性模量:E=206000N/mm2 容许应力:fm=200N/mm2
强度计算:
![](https://www.soolun.com/img/pic.php?url=data:image/png;base64,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)
;σmax=
![](https://www.soolun.com/img/pic.php?url=data:image/png;base64,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)
÷W=193MPa<=193MPa。 刚度计算:
![](https://www.soolun.com/img/pic.php?url=data:image/png;base64,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)
;f/L=1/570~1~
分配梁強度、刚度均满足要求。但分配梁偏弱,增加斜撑加强。
4、施工控制和监测方法
影响箱梁线型和内力的因素主要有混凝土容重、弹性模量、收缩徐变、日照和温度变化、预应力大小、结构体系转换、施工荷载和桥墩变位等。在施工过程中还需要做好主桥箱梁施工监控工作,主要内容如下:
1)对挂篮进行加载试验,消除非弹性变形,并向监控单位提供非弹性变形值及挂篮荷载—弹性变形曲线。
2)在0号块箱梁顶面建立相对坐标体系,以此相对坐标控制立模标高值。施工过程中及时采集观测断面标高值并提供给监控单位。
3)温度控制:为掌握箱梁截面内外温差和温度在截面上的分布情况,在梁体上布置温度观测点进行观测,以获得较为准确的温度变化规律。
4)挠度观测:为了尽量减少温度变化对箱梁施工的影响,挠度的观测安排在一天中温度相对变化小的时间进行。在箱梁顶板和底板布置测点,并测量立模时、混凝土浇筑前、混凝土浇筑后、预应力束张拉前、预应力束张拉后的标高。
5)应力观测:根据连续梁的受力特点,合理布置测试截面和测点,并埋设应力测试元件,在施工过程中测试截面的应力变化与应力分布情况,以验证各施工阶段被测梁段的应力值和仿真分析的吻合情况。
6)施工不平衡荷载的控制:严格控制施工中不平衡荷载的分布及大小。具体的主桥箱梁施工监控严格按照监控单位提供的实施细则执行。
5、结论
结合某桥工程,对桥梁结构形式、结构特点、0号块施工技术要点、钢管桩支架施工、支架稳定性计算和施工监控控制方面做了介绍。根据施工监控结果,该桥在施工过程中结构变形、应力、临时支撑结构等均在安全范围内,大桥施工进展顺利。
参考文献:
[1]文瑜 谢玮.公路桥梁施工临时支架稳定性计算与分析[J].山西建筑.2012,38(23).167-169
[2]李明星.变截面曲线桥现浇梁模板支架的稳定性计算[J].山西建筑.2013,39(3).177-179
[3]刘明军 林志军.田安大桥支架钢管桩设计与施工[J].城市道桥与防洪.2012(4).83-88
[4]希文峰,黄羚.桥梁满堂支架施工力学计算模型研究与应用[J].公路与汽运.2012(2).172-176
[5]中华人民共和国交通部.JTG D60-2004公路桥梁设计通用规范[S].北京:人民交通出版社,2004.
关键词:变截面;箱梁大桥;钢管桩;结构计算
1、前言
据统计,每年都有桥梁因为支架的倒塌而产生人员伤亡[1],通常发生事故原因有两个,一是设计荷载不足,安全失效,二是施工管理不到位,工作人员蛮干,导致施工安全事故。桥梁施工支架的施工方法和技术对于工程建设的顺利进行以及结构的安全至关重要。
随着桥梁技术不断发展,变截面大体积预应力混凝土箱梁得到越来越广泛的应用,其设计及施工单位更加重视施工计算和脚手架培训工作。例如李明星[2]结合某市政变截面曲线匝道桥满堂门式支架施工,详细介绍了满堂门式支架的构架方法和稳定性计算。文瑜 谢玮[1].对桥梁施工临时支架倒塌的常见原因进行了分析,对影响支架稳定性的因素和支架稳定性计算方法进行了总结。刘明军,林志军[3]介绍田安大桥主桥拱面部分的梁段安装支架钢管桩的设计计算与施工。希文峰,黄羚[4]根据满堂支架的结构及受力特征,分析了满堂支架荷载计算方法以及立杆、底模、纵向方木、横向方木等主要组成构件的计算模型。
2、工程概况
某桥工程桩号分别为K0+000,终点桩号K2+300,全长2.3km。主桥上部构造:混凝土C55:16293.6m3Ⅰ钢筋606t,Ⅱ钢筋2747t,预应力钢绞线841t。该桥左幅设计为:(4×32m)等截面预应力砼连续箱梁+(58+3×96+58)变截面预应力砼连续箱梁+(3×24)等截面预应力砼连续箱梁+(4×32)等截面预应力砼连续箱梁+(3×32)等截面预应力砼连续箱梁;右幅设计为:(3×32m +24.175m)等截面预应力砼连续箱梁+(58+3×96+58)变截面预应力砼连续箱梁+(25.825+2×27)等截面预应力砼连续箱梁+(4×32)等截面预应力砼连续箱梁+(3×32)等截面预应力砼连续箱梁。
该桥主桥设计为58m+3×96m+58m五跨变截面预应力混凝土连续箱梁。主跨箱梁单“T”共分12段悬臂浇筑,0号梁段长12m,其余1-12号梁分段长为7×300+5×400cm,邊跨、次边跨、中跨合拢段都为2m,边跨现浇段长10m。0号梁段和边跨现浇段采用钢管桩支架现浇施工,主跨T构采用对称挂篮悬臂现浇施工,悬浇最重梁段为1794kN。
3、钢管桩支架计算
主要临时支架破坏形式为失稳破坏,即支架倒塌。倒塌主要是由于支架承受的施工临时荷载时位移变形过大而造成,即几何非线性的影响十分明显。为保证临时支架结构体系,整体稳定性满足要求是设计过程的首要问题。支架现浇方案,采用布架灵活、搭拆方便、承载力大。如图2所示,取单根钢管桩受力进行分析。
图2 单根钢管桩受力示意
Figure 2single steel pipe pile stress
A1断面平均截面积6.45 m2,砼体积26.8 m3,A2断面平均截面积2.47 m2,砼体积10.25 m3,A3断面平均截面积5.81m3,砼体积24.1 m3。通过分析比较,只计算中间钢管桩和两侧钢管桩。依照有关规范[5,6],对荷载作用进行计算。
4.1中间钢管桩计算
中间钢管桩最大平均受力面积A=6.45m2;现浇预应力钢筋砼自重:q1=26KN/m3×26.8 m3=697 KN
模板自重:q2=2.5KN/m2×3.25m×4.15m=33.72KN
振捣砼产生荷载:q3=2.0 KN/m2×3.25m×4.15m=27.0KN
运输、堆放荷载:q4=3.0 KN/m2×3.25m×4.15m=40.46KN
恒载:(q1+q2)×1.2=876.9KN;活载:(q3+q4)×1.4=94.4KN;荷载:恒载+活载=971.3KN
钢管桩结构计算:
钢管桩φ700×8mm的A3钢钢管,自由长度层距4m。
钢管惯性矩:
;截面積:
; 慣性半径
;柔度系数
;
极限柔度
;
λ<λ2,屬于短粗杆(小柔度杆),用经验公式计算F=σcr×A;
F=cr×A=200
×
=3480KN;安全系数为:
;
中间钢管桩满足施工要求。
4.2两侧钢管桩计算
平均横断面积A=5.81m2。方法同中间钢管桩计算方法,最终得出,安全系数
,中间钢管桩满足施工要求。 4.3縱向分配梁受力计算
通过分析,纵向分配梁最不利位置为中腹板,荷载由六根Ⅰ25b工字钢承担,工字钢间距1.2m。
计算得出恒载:(q1+q2)×1.2=328KN;活载:(q3+q4)×1.4=23.5KN;
荷载:恒载+活载=351.5KN;荷载:q=125.5KN/m
分配梁结构计算:Ⅰ25b悬臂长度2.8m。
惯性矩:
6×5280cm4=3.168×108mm4;截面抵抗弯矩:W=
÷ymax=6×423×cm3=2.54×106mm3
弹性模量:E=206000N/mm2 容许应力:fm=200N/mm2
强度计算:
;σmax=
÷W=193MPa<=193MPa。 刚度计算:
;f/L=1/570~1~
分配梁強度、刚度均满足要求。但分配梁偏弱,增加斜撑加强。
4、施工控制和监测方法
影响箱梁线型和内力的因素主要有混凝土容重、弹性模量、收缩徐变、日照和温度变化、预应力大小、结构体系转换、施工荷载和桥墩变位等。在施工过程中还需要做好主桥箱梁施工监控工作,主要内容如下:
1)对挂篮进行加载试验,消除非弹性变形,并向监控单位提供非弹性变形值及挂篮荷载—弹性变形曲线。
2)在0号块箱梁顶面建立相对坐标体系,以此相对坐标控制立模标高值。施工过程中及时采集观测断面标高值并提供给监控单位。
3)温度控制:为掌握箱梁截面内外温差和温度在截面上的分布情况,在梁体上布置温度观测点进行观测,以获得较为准确的温度变化规律。
4)挠度观测:为了尽量减少温度变化对箱梁施工的影响,挠度的观测安排在一天中温度相对变化小的时间进行。在箱梁顶板和底板布置测点,并测量立模时、混凝土浇筑前、混凝土浇筑后、预应力束张拉前、预应力束张拉后的标高。
5)应力观测:根据连续梁的受力特点,合理布置测试截面和测点,并埋设应力测试元件,在施工过程中测试截面的应力变化与应力分布情况,以验证各施工阶段被测梁段的应力值和仿真分析的吻合情况。
6)施工不平衡荷载的控制:严格控制施工中不平衡荷载的分布及大小。具体的主桥箱梁施工监控严格按照监控单位提供的实施细则执行。
5、结论
结合某桥工程,对桥梁结构形式、结构特点、0号块施工技术要点、钢管桩支架施工、支架稳定性计算和施工监控控制方面做了介绍。根据施工监控结果,该桥在施工过程中结构变形、应力、临时支撑结构等均在安全范围内,大桥施工进展顺利。
参考文献:
[1]文瑜 谢玮.公路桥梁施工临时支架稳定性计算与分析[J].山西建筑.2012,38(23).167-169
[2]李明星.变截面曲线桥现浇梁模板支架的稳定性计算[J].山西建筑.2013,39(3).177-179
[3]刘明军 林志军.田安大桥支架钢管桩设计与施工[J].城市道桥与防洪.2012(4).83-88
[4]希文峰,黄羚.桥梁满堂支架施工力学计算模型研究与应用[J].公路与汽运.2012(2).172-176
[5]中华人民共和国交通部.JTG D60-2004公路桥梁设计通用规范[S].北京:人民交通出版社,2004.