a混凝点土拆模时间 规范专业讲解.doc
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1、In order to ensure normal teaching order, protecting students healthy growth, ensuring that national (property) is not lost, to prevent or minimize the occurrence of safety accidents, follow the prevent, rescue each other, ensure safety and reduce losses principle, according to the local conditions,
2、 make the management system. 1, the principal is the responsibility of school safety, school security under the leadership of President security work leading group. The head teacher to the leadership team is responsible for, implementation of the accountability system. 2, school monthly student know
3、ledge about safety education, education should be diversified in the form every safety education for students of classes per week should be targeted. To carry on emergency issues dealing with education in General, self-help and mutual rescue knowledge. Emergency calls (such as 110, 119, 122, 120, an
4、d so on) use common sense in education. 3, the establishment of major accident reporting system. School students report major accident within an hour of education; student run and disappearances to report; report of the accident to a written report in triplicate, a correctional centre, a police stat
5、ion, a township peoples Government shall not conceal the accident. 4 week, teachers are on duty system, establish and improve the leadership values; strengthen the education, management of teaching activities in schools to ensure normal teaching order; responsible for school safety leadership always
6、 maintained close contact and district police stations, canvassing support from the police station on school safety and help. 5, strengthening teachers moral education, establish a dedicated love, improving education quality, observe the students psychological changes at any time and take preventive
7、 measures, no corporal punishment and covert corporal punishment on students, student out of the classroom, schools may not be. 6, units or departments use student Street propaganda or participate in the celebrations, as well as participating in other social work, without approval of the Correctiona
8、l Centre, school principals consent, without organization. Without the approval of relevant departments, may organize students to participate in fire fighting, disaster relief and so on. 7, schools should educate students to obey the school rules and regulations, on time, on time home to prevent acc
9、idents. 8, school to school inspections on a regular basis, found hidden in time, and in severe cases, it is hard to eliminate immediately closed, and reported to the local peoples Government, education, and rule of law section. 9, the school should always check the internal walls, retaining walls,
10、ponds, railings, handrails, doors, Windows, staircases and a variety of sports, extracurricular activities, facilities such as fire safety, infrastructure security, unsafe facility to immediately repair and demolition to ensure that teachers and students work, learn, live venues and facilities are s
11、afe and reliable. Song Lin Xiang Liu Jia ping elementary school March 2016 song Lin Xiang Liu Jia ping primary school fire safety systems to enhance fire safety, protection of public property and the life and property safety of teachers and students, school fire safety into day-to-day management, is
12、 developing the following fire safety system. 1, strengthen fire safety education of the whole school. According to the requirements of the Fire Services Act, so that everyone has of keeping fire control safety, protecting fire control facilities, fire prevention, reports of fire混凝土拆模时间 规范专业讲解1.拆模时间
13、依据、梁、板模板的拆模时间依据:同条件混凝土试块试压强度、柱、墙模板的拆模时间为混凝土达到终凝后、拆模不影响混凝土质量为宜。2.底模拆除时的混凝土强度要求混凝土结构工程施工质量验收规范(GB502042002)4.3.1规定,拆除底模和支架时的混凝土强度要求:1、板A:构件跨度不大于2米,要求达到设计的混凝土立方体抗压强度标准值的百分率应不小于50%;B:构件跨度在区间(2m,8m的,要求上述值不小于75%;C:对于构件跨度大于8米的,要求达到100%2、梁、拱、壳A:跨度不大于8米的构件 要求达到75%以上的百分率;B:跨度大于8米的构件 ,要求强度达到100%3、悬臂构件,均要求设计强度达
14、到100%。侧模拆除的混凝土强度应保证其混凝土表面和棱角不受损伤3.拆模时间一般是多少天?(1)混凝土侧模拆模时间一般只要保证表面及棱角不因拆模而受到损伤就可以了,一般情况下混凝土浇筑完一天后就可以拆了,从实际情况来看也是尽早拆拆模效果比较好。(2)底模就根据GB50204-2002中的要求。一般来说在混凝土施工时现场留置同条件拆模试块,在估计时间差不多时进行试压,试压达到要求后经监理同意后进行拆除(因为需要填报拆模检验批,里面有拆模强度一项,要求填的就是拆模试块强度)。(3)拆模时间柱、墙、梁不做支撑的侧模:12小时单向版(净跨距里3-6M,活载重不大于静载重):7D单向版(净跨距里3-6M
15、,活载重大于静载重):4D单向版(净跨距里6M,活载重不大于静载重):10D单向版(净跨距里6M,活载重大于静载重):7D梁底模(净跨距里3-6M,活载重不大于静载重):14D梁底模(净跨距里3-6M,活载重不大于静载重):7D梁底模(净跨距里6M,活载重不大于静载重):21D梁底模(净跨距里6M,活载重大于静载重):14D混凝土拆模强度的时间控制 混凝土结构工程施工质量验收规范(GB50204-2002)第4.3.1条规定:底模及其支架拆除时的混凝土强度应符合设计要求;当设计无具体要求时,混凝土强度应符合下表规定: 构件类型 构件跨度(m) 达到设计的混凝土立方体抗压强度标准值 (f cu
16、, k ) 的百分率(%) 板 2 50 2,8 75 8 100 梁、拱、壳 8 75 8 100 悬臂构件 100 如何科学地确定达到上述拆模强度所需的时间, 是日常施工中经常遇到的难题, 长期以来一直未得到很好解决, 这使生产进度安排、质量控制造成极大盲目性; 尽管规范要求制作同条件养护试块强度作为拆模的依据, 但目前试块的养护很不规范, 虚假因素较多。同时, 具体操作上也还存在一定的难度, 即无法具体确定送检时间。另一方面, 施工单位为了追求利润, 降低成本, 减少投入, 模板与支架数量配置往往不足, 随意拆模的现象十分普遍, 对工程质量、施工安全造成隐患。 t= t= 3.1 影响混
17、凝土强度增长的主要因素 一是混凝土成熟度M。大家知道,混凝土强度的增长是随着时间的增加而增长的,温度越高增长越快,反之,温度越低增长也就越慢。混凝土成熟度就是时间与温度对于混凝土强度增长的综合影响值, 可按下式确定: Mt (T10) (1) 式中: M- 混凝土成熟度(.d); T- 混凝土平均养护温度() t- 混凝土养护时间(d)(从终凝开始起算 ) 二是混凝土强度增长特征值A。 大家知道,同样的养护温度条件,混凝土强度的增长也各有不同,这种特性,我们用强度增长特征值A表示,A值大,早期强度高;A值小, 早期强度低,其大小与水泥、外加剂品种以及水灰比大小有关。 3.2 混凝土强度增长与成
18、熟度的关系式f t / f28 = M / (A .M + B)(2)式中: f t -某一龄期混凝土强度值; f28 -混凝土28天强度值; B与A值大小有关的常数,B=840(1-A) 3.3 混凝土达到拆模强度所需的时间 1. 混凝土达到拆模强度所需成熟度M =C.B / (1- C.A) (3) 式中: C-规范规定的混凝土拆模强度与混凝土配制强度的比值, 例如:C30混凝土达到抗压强度标准值的75%时应为22.5N/mm2, 如果混凝土配制强度按设计强度标准值的1.15%考虑,则C=22.5/ (301.15)=0.65。 以8m跨度以内的梁为例(A=0.84), 混凝土达到拆模强度
19、所需的成熟度应为192, 而跨度等于、大于8m 时, 混凝土达到拆模强度所需的成熟度M应为430。 2. 混凝土达到拆模强度所需的养护时间 t 可按下式确定: t = M / (T+10) (5)现以混凝土配置强度f0 按1.15f,cu,k,为例, 给出混凝土分别达到抗压强度标准值的75 %、100 %所需的养护时间(见下图)。 M= t= 注:1. 实线为混凝土达到抗压强度标准值的75%所需时间,虚线为混凝土达到抗强度压标准值的100%所需时间。2. 图中: A=0.82, A=0.84, A=0.86, A=0.88。 从以上分析可以看出: 一是温度越高, 混凝土所需的养护时间越短, 冬
20、季施工所需的养护时间几乎是常温季节时的2倍甚至更多;二是达到100%强度所需的养护时间几乎是75%强度所需时间的2倍甚至更多。 3.4 几点建议 1. 采用本方法预估混凝土的时间,其关键一是准确掌握各种水泥、外加剂、水灰比的A值。为此, 需要进行必要的试验, 积累一定的试验数据,建议预拌混凝土厂对日常试验资料进行统计分析,为用户提供依据; 二是认真做好施工现场气温记录 (气象预报温度与实际有一定误差, 只能作为参考)。 2采用本方法预估拆模时间,拆模前尚需对试块进行试压, 并根据试压结果确定能否拆模。 3. 冬季施工时应适当提高混凝土配制强度, 以降低混凝土拆模强度与混凝土配制强度的比值 C。
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