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1、 高层建筑厚板式转换层施工技术探讨摘 要:本文结合工程实例,在施工技术方案分析的基础上,通过合理选用支撑体系,并采用大掺量粉煤灰、聚丙烯纤维混凝土技术,有效地保证了厚板式转换层的施工质量,并对模板工程、钢筋工程、混凝土浇筑施工技术进行了详细阐述。 关键词:高层建筑;厚板式;结构转换层;一次性浇筑;模板支撑 1工程概况 湖南某商住综合楼工程地下3层,地上30层,建筑物总高度102m,建筑面积65000m2。工程设有3层裙房,裙房为框架结构,做商务办公和大型超市。在塔楼四层上设有厚板式结构转换层,其上部为剪力墙结构。转换层平面尺寸为38.80m38.16m,建筑面积1480 m,厚度在边柱部位3.
2、1m,其它部位2.2m,核心筒部位为双层板(图1),混凝土强度等级为C40,浇注量为2850 m3。 2施工方案分析 经计算转换层施工时在边柱部位最大垂直荷载88kN/m2,其它部位68kN/m2。为承受转换层的施工荷载,设计考虑将三层楼板加厚到250mm,并将配筋加强,设计承载力70kN/m。边跨梁高3.1m的部位,考虑模板荷载较大,为了便于施工,在满足结构安全的前提下,建议设计将边跨梁设计成双层梁。只要保留二、三层模板的支撑体系,通过二层、三层楼板的连续支撑,将施工荷载分散传递到下面的竖向结构上,就能保证转换层施工的安全。因此采用900mm1400mm边梁先行浇筑,2.2m厚板式转换层混凝
3、土不留施工缝,一次性浇筑的施工方案。大体积混凝土工程采用大掺量粉煤灰,掺加聚丙烯纤维技术,降低水化热,控制混凝土的温度裂缝。 3转换层施工技术 3.1 模板工程 该工程结构转换层混凝土浇筑一次性完成,施工速度快,但模板支撑数量大。选择模板支撑方案主要考虑以下因素:保证转换层混凝土的结构质量,满足结构设计要求模板支撑体系稳定可靠,确保高大模板施工的安全:选材方便,降低工程成本。 3.1.1底模板及支撑 选择定尺的483.5mm钢管脚手架支撑体系,通过计算确定模板支撑体系立杆的间距、步高及剪刀撑的间距。立杆下铺垫板,上端设可调顶托,主楞骨为100mm100mm方木,密排50mm厚木方作次楞骨,选用
4、12mm竹胶合板模板,胶合板模板上面铺设一层0.6mm厚的塑料薄膜,用以对混凝土底面的保温、保湿养护。支撑采用双立杆布置的方法,除满足荷载要求外,还应考虑操作方便。纵距为550mm,双立杆间距250mm,间隔布置(即La=550 mm ),步高(h)为850mm,横距(b)为400 mm。设置双向扫地杆,每3600 mm设置双向剪刀撑(图2)。 边梁部位转换层厚度3.1m,且较三层外挑1080mm,竖向支撑在三层楼板上布置16#槽钢800作挑梁。槽钢外挑1300mm,内压1700mm,遇墙时在墙上穿孔。在悬挑槽钢上通长布置6根10#槽钢,立杆按设计要求布置在上面,支撑边梁底部,边梁900mm高
5、混凝土先行浇筑后与梁底支撑系统共同作用,支撑2.2m厚板式转换层的施工荷载。 3.1.2侧模支撑 转换层在15.65m标高上,为了防止出现胀膜现象,保证混凝土外观质量,侧模采用了全钢大模板。模板高度3240mm,设锚固螺栓固定侧模,螺栓与支撑系统、竖向及水平混凝土结构连接固定(图3)。二、三道螺栓在有柱的部位焊接在柱的钢筋上,在无柱的部位,第二道螺栓焊接在梁上的预埋筋上,第三道螺栓焊接在10槽钢上。 由于钢大模板散热较快,混凝土侧表面与环境的温差极易超过25。为了满足温差要求,及时采取了拆除钢模板,覆盖、保湿、保温的措施。 3.1.3楼梯支模 由于楼梯及预留孔洞的承载力比其它部位低,所以采取了
6、槽钢和斜撑辅助加固的措施(图4)。调整三层楼梯板的设计,增大其承载力,脚手架支撑从一层开始加固,以确保该部位支撑的稳定。 3.2钢筋工程 结构转换层钢筋用量大约1100t,全部采用HRB400型,钢筋密集,钢筋直径大。结构转换层纵横各设置11道暗梁,暗梁宽度10002600mm,梁上层钢筋双排28mm,下层筋双排28mm。板筋上下层采用25mm和28mm两种,双排双向。为抵抗混凝土局部强度收缩应力,在板中上下排钢筋间设16200双向钢筋网,无暗梁区域上下排钢筋间设16400抗剪兼架立筋。 板内布筋原则:横向筋放于外排,竖向筋放于内排,上部筋在跨中连接,下部筋在暗梁处连接。 由于钢筋层数较多,为
7、保证钢筋连接质量和方便施工,板中所有受力钢筋均采用直螺纹连接。板主筋保护层取50mm,梁主筋保护层取30mm,转换层厚板内的钢筋,不得在暗梁内截断,施工时不得留施工缝。排水管采用4根DN250无缝钢管套管,排水管安装时遇钢筋时钢筋弯曲,不得截断钢筋。暗梁钢筋安装搭设临时脚手架钢管支架,先安装同一方向的暗梁,再安装另一方向的暗梁,避免钢筋纵横交叉,架空叠加超高。因转换层钢筋单位面积重量大,特别是暗梁部位,采用现场特制的高强保护层垫块,并增加垫块数量,以保证钢筋保护层的厚度。 3.3 混凝土工程 转换层混凝土强度等级为C40,为控制大体积混凝土的裂缝,设计要求采用循环冷却水管降温,并加膨胀剂。考虑
8、转换层内钢筋密集,循环水管施工困难,造价高。膨胀剂在保湿养护条件下,能较好补偿混凝土的收缩,但在转换层侧面和底部受养护条件限制,膨胀剂对此较难发挥作用。经论证,决定取消循环冷却水管和掺加膨胀剂的方案,采用大掺量粉煤灰降低水化热,并在混凝土中增加聚丙烯纤维控制混凝土的早期收缩裂缝。 3.3.1配合比设计 经试验,选用强度等级42.5普通硅酸盐水泥,其质量稳定,具有保水性好、泌水性小的特点,适用于泵送混凝土。为了减少水泥用量,降低水化热,控制混凝土温度及收缩产生裂缝,用级粉煤灰取代30水泥,粉煤灰的超量系数为1.35。碎石的粒径为535mm;河砂的细度模数2.7。同时掺加0.9kg /m3的KDZ
9、-II 型聚丙烯纤维,纤维密度0.91g/cm3,线密度偏差率5%,断裂强度659MPa,断裂延伸率16%,伸长率5%时的初始模量7171MPa。 配合比水胶比为0.38,砂率41。选用LX一1(T)型外加剂延缓混凝土的凝结时间,推迟水化热峰值时间,初凝时间(自然条件下薄膜覆盖)约为20h左右,终凝时间约为40h 。出机坍落度为205mm,1.5h后为180mm( 白天2531)。混凝土配合比见表1 。标养试块按60d强度评定。 3.3.2混凝土 转换层厚度2.2m,面积约为1480m2,共需混凝土2850m3,均采用商品混凝土。现场配备混凝土输送泵3台,混凝土供应能力60m。采1用平面分层浇
10、筑方案,有利于支撑系统的稳定,降低水化热。 混凝土分3层整体连续浇筑,每层约700mm。大掺量粉煤灰纤维混凝土应属于高性能混凝土范畴,混凝土坍落度较大,采用50mm插入式振捣棒,严格控制层间搭接振捣,不过振漏振,振捣以混凝土表面不再显著下降,不出现气泡,表面泛浆为准,初凝前需进行二次振捣。梁、柱、墙相交的部位,由于钢筋较密应采用30mm的振捣棒。 大体积混凝土表面水泥浆较厚,浇筑后应进行处理。初凝前12h,先用长刮杆刮平;终凝前,再用铁滚筒碾压数遍,并用木抹子打磨压平,以闭合表面收缩裂缝。核心筒部位混凝土浇筑:核心筒部位是双层板,根据该部位的结构形式,分二次浇筑。 3.3.3大体积混凝土的养护
11、及测温 转换层混凝土初凝后,表面即覆盖一层塑料薄膜和保温毯,实施保温、保湿养护,并根据测温情况随时调整保温措施,使混凝土中心与表面、表面与环境的温差均不大于25。混凝土内部温度低于峰值后,采用浇水养护的措施。 为能及时有效地了解混凝土的温度变化情况,转换层共设16个测温单元,共48个温度传感器,用电子测温仪测量读数,对混凝土温差实施跟踪和监测。混凝土浇筑12h后开始测温,根据混凝土升温的速率决定测温频次。浇筑后3 5d时间内,24h测一次,其后46h测一次,并作好记录。实测结果表明板中心峰值温度62.5,在第4d出现,同时测得板底混凝土温度58,板面混凝土温度45。 4结束语 本工程在转换层混
12、凝土施工前后对模板支撑体系进行了详细的检查,支撑体系稳定可靠,变形均在允许范围之内。混凝土施工时间为9月下旬,气温较高。通过采用大掺量粉煤灰、聚丙烯纤维混凝土技术,有效地控制了大体积混凝土的裂缝,较冷却循环水管降温方案,造价明显降低。 大体积混凝土内部产生的水化热较大、温度较高,强度上升比拆模试块要快得多。而结构转换层占有周转材料较多,为了既节约周转材料的费用,又能保证混凝土的拆模强度。建议采用回弹结构转换层侧模混凝土,并结合测温记录求得的混凝土等效龄期强度来判断混凝土达到的实际强度。 参考文献: 1 高层建筑混凝土结构技术规程.JGJ3-2202.S. 2 混凝土结构设计规范.GB 5001
13、0-2002.北京,中国建筑工业出版社,2002. 3 唐兴荣.高层建筑转换层结构设计与施工M.北京:中国建筑工业出版社,2002. 4 谢晓锋.高层建筑转换层结构型式的应用现状及问题J.广东土木与建筑,2004. 5 建筑施工脚手架实用手册.北京:中国建筑工业出版社,2004.organization system and working mode, the selection of a number of municipal strengthening group to build innovation and strengthen the organization of the basi
14、c level organizations advanced model.(seven) the manual work of the Communist Youth League Organization published and League branch of manual work, to promote the use of two manuals in the citys organizations at various levels. The county committee, directly under the group (work) is under the juris
15、diction of grassroots League and group (total) using branch ratio shall not be less than 70%.Three, to further strengthen the groups leadership and team building(a) to strengthen the leagues leadership at all levels of construction. Continue to do a good job of municipal Party Committee Organization
16、 Department on the strengthening of the Communist Youth League cadres management opinions implementation. To promote the group counties (autonomous counties, cities) Commission and city directly under the group (workers) appointed to carry out the Five team building activities. Improve the League As
17、sociation Department working mechanism. Conscientiously fulfill the duties of CO, combined with the city group directly under (the) Committee of the general election and the adjustment, actively jointly with the unit where the party organization department good group leadership selection with the wo
18、rk. Do a good job in municipal Party committee assistant committee leadership and leading cadres of the annual assessment work, adhere to and improve the assistant secretary of the Communist Youth League talk system group To weave individual conversation and collective conversation, to strengthen th
19、e committees of all levels, the Standing Committee of the Standing Committee, the establishment of a sound system of central group learning, the system of investigation and study, the system of important issues and the reporting system.(two) to strengthen the work of education and training of cadres
20、 to conscientiously implement the Central Committee. On the implementation of grassroots cadres training project and opinions on carrying out the mission municipal CYL Cadres training project implementation opinions, full implementation of the project of the City Youth League cadres training educati
21、on. Focus on the county grassroots cadres and workers focused on training, the new school system vocational training League cadres, for the Municipal Organization Department jointly held the third session of the Communist Youth League system training cadres in party. Focusing on the construction of
22、new socialist countryside, strengthening village cadres and rural construction team group member of the young team, the county organizations at various levels throughout the year is expected to train 100 00 rural grassroots cadres, plans to train 1000 village secretary of the village Party branch.(t
23、hree) actively promote grassroots cadres election work. Under the unified leadership of the party organization, to strengthen grassroots organizations direct work, standardize the election work rules and procedures, in the designated candidate, open competition to democratically elected branch secre
24、tary at the same time, actively and steadily the development of Township, streets and other grassroots organizations in the direct election of the pilot work, on the basis of summarizing the experience and gradually expand the scope of the pilot, and gradually formed a set of measures and cadres ele
25、ction system.(four) to strengthen the cadres testing exercise. To study the development of XX city from 2006 to 2008 cadres testing exercise planning. To select outstanding cadres to the central mission in Beijing, Shanghai, Guangzhou and other central organs and sending work in developed areas. Wit
26、h the Central Committee the implementation of the western region and ethnic minorities cadres training plan . To carry out the eighth batch of municipal organs attachment cadre management, selection, training work. The outstanding cadres to start the National Development Bank XX branch testing exerc
27、ise.(five) to strengthen the group construction. The main position to play the role of Youth League cadre education and training as the city, in accordance with the requirements of post training, further curriculum scientifically and rationally, adopt arrangement menu course, basic theory includes g
28、roup work, focus, hot and difficult issues, to enhance the content and practice; to strengthen the construction of teaching staff, the integration of teachers, establish a quality teacher training team, establish and implement course evaluation system; take delivery of training to the countryside, o
29、n-site training, and increase the rural grassroots cadres training efforts.Four, efforts to strengthen the work of young talent(a) to tenth XX young 54 medal in recognition of the publicity, and actively explore the XX youth service. 54 Medal of institutionalization, standardization and socializatio
30、n mechanism. Give full play to the XX award in recognition of 54 youth medal Association, Youth Award winner in the 54 chapter, investigation activities. Who won the Youth Service medal, dedication to the society to create conditions, build the stage. During the 54, named in recognition of the tenth
31、 XX young 54 medal. The association of XX editing of young talent , the exchange of information and communication platform for the XX of outstanding young talents.(two) the establishment of municipal Party committee of young talent information database. In accordance with the feasible, effective, cl
32、assification management, implement step by step principle, the establishment of municipal Party committee of youth talent database; guiding organizations at various levels generally established the young talent database, construction of city, county (directly under the Communist Youth League), grass
33、roots organizations three young talent information database the relevant information collection system, and gradually establish the citys young people, the Communist Youth League youth talent information network, provide information platform for young talent resource development.Five, take effective
34、 measures to strengthen the mission management(a) to strengthen the mission management work. Strengthen the dues collection and management, continue to adhere to the dues collection regularly reporting system, the annual comprehensive award in recognition of the tour and the tour one vote veto syste
35、m audit system. Do statistical work in the group. The group service award in recognition of the advanced units, standardization, promoting group management work institutionalized.(two) to strengthen the organization of research and information exchange efforts. Grassroots carry out research, efforts
36、 to form a number of theoretical results. Make full use of the network carrier, to explore the establishment of electronic group service system, promote the work of Communist Youth League information.Attachment 4:XX municipal Party Committee Propaganda Department of the Communist Youth League work p
37、ointsIn 2006, the Communist Youth League propaganda ideological work XX to Deng Xiaoping theory and the important thought of Three Represents as guidance, study and implement the partys sixteen and the spirit of the the fifth Plenary Session of the 16th CPC Central Committee implementation of the ei
38、ght plenary session of the two committee, the citys cultural work conference, the Propaganda Department of the meeting and the the fourth Plenary Session of the 15th CPC Central Committee permanent mission spirit, closely around 11th Five-Year XX the goal of full implementation of Scientific Outlook
39、 on Development, emancipating the mind, seeking truth from facts, keep pace with the times, close to reality, close to life, close to the young, persevere grasp orientation, grasping deepening, grasping construction innovation, further improve the groups propaganda and ideological work ability, unit
40、y To guide the majority of members of the youth to achieve the 11th Five-Year planning tasks, the overall construction of a well-off society, building a socialist harmonious society to make new contributions.One, adhere to the Three Represents important thought and Scientific Outlook on Development
41、education to guide the youth, to further strengthen the ideological and political education of youth(a) armed with youth science theory. Unremittingly with Deng Xiaoping theory and the important thought of Three Represents armed members of youth education, to promote the study and implement to expan
42、d the depth and breadth. To study and implement the important thought of Three Represents with the establishment and implementation of Scientific Outlook on Development combine with the implementation of the requirements of constructing socialist harmonious society with Scientific Outlook on Develop
43、ment, carry out education as an important part of the theory of armed youth in the new period, strengthen the establishment and implementation of Scientific Outlook on Development education, educate and guide the youth to fully understand the great significance of establishment and implementation of
44、 Scientific Outlook on Development, in-depth understanding of the Scientific Outlook on Development era back The king, the practice foundation, basic connotation, historical status, spirit and practice requirements, a profound understanding of Scientific Outlook on Development with Marxism Leninism,
45、 Mao Zedong thought, inheriting and developing relationship between Deng Xiaoping theory and the important thought of Three Represents, to help young people establish and consciously practice Scientific Outlook on Development. Persist in learning, grasping the backbone, grasp the practice, grasp the
46、 opportunity. Catch club, effective way to grasp the network, with the group of cadres, young students and young backbone fronts as the focus, to promote the work of the armed youth theory to develop in depth, to help the youth continue to firm ideals and beliefs, to build a powerful spiritual pilla
47、r. To carry out the study and implementation of the partys sixteen session of the five Eight plenary session of the two plenary session of the Central Committee and the party spirit, to the citys Youth League members thinking into the spirit of the meeting, to achieve the goal of national consciousn
48、ess and XX economic and social development in 11th Five-Year period. Contribute to help and guide the youth to a profound understanding of the significance and main task of building a socialist harmonious society, actively join the construction of socialist harmonious society.(two) to strengthen the ideological and moral construction of teenagers. Thoroughly implement the central spirit of the document No. 8, No. 16 and the program for Improving Civic Morality to minors and students as focus groups, to strengthen and improve th