建筑幕墙设计风荷载取值的再讨论

建筑幕墙设计风荷载取值的再讨论(一)中国幕墙网收集整理 作者:张芹 日期:2006-1-20 建筑幕墙设计风荷载是玻璃幕墙设计诸荷载(作用)中最重要的一项。它的取值直接影响玻璃幕墙的安全，尤其是体型复杂的高层建筑玻璃幕墙的设计风荷载更要慎重采用。 玻璃幕墙工程技术规范JGJ102-2003指出，“经验表明，玻璃幕墙的设计主要取决于风荷载作用，对于体型复杂的幕墙工程或房屋高度较高（比如超过200m）的幕墙工程，应确保风荷载作用下的可靠性”，“一般情况下，对幕墙起控制作用的是风荷载。幕墙面板本身必须具有足够的承载能力，避免在风荷载作用下破碎。我国沿海地区经常受台风的袭击，设计中应考虑有足够的抗风能力。”鉴于设计风荷载对玻璃幕墙设计的重要性，在台风过后，不少地区对台风给玻璃幕墙的影响进行了调查和分析，也有不少学者对玻璃幕墙进行了风洞试验和风力测试分析，提出了很多论文和报告，这些论文和报告对完善玻璃幕墙设计风荷载起极大作用，但也有些问题需要进一步探讨，现提出以下几个问题和全国同行们讨论。 一玻璃幕墙设计风荷载计算中，基本风压是取50年一遇的基本风压，还是要提高到取100年的基本风压值 GB50009指出：“对于围护结构，其重要性与主体结构相比要低些，仍可取50年一遇的基本风压。” 现在有些地方建设部门，以厦门9914号台风、浙江2005年云娜台风的瞬时风速为由，提出要改取100年一遇的基本风压。这是由于当地新闻单位误导的结果，厦门9914号台风阵风风速46米/秒，按厦门1958年1961年221次风过程统计分析，瞬时风速为10分钟平均风速的1.45倍，按此折算10分钟平均风速为31.72米/秒（按全世界平均值1.5倍折算10分钟平均风速为30.67米/秒），为11级风（风速28.532.6米/秒），不是14级风（风的等级表只有012级，12级为风速32.6米/秒，没有14级风），按厦门基本风压0.80kN/m2折算风速为35.78米/秒，即厦门9914号台风远未达到厦门50年一遇的基本风压；2005年云娜台风，温州阵风风速36.9米/秒（按全世界平均值1.5倍折算10分钟平均风速为24.6米/秒），为10级风（风速24.528.4米/秒）未达到其50年一遇的基本风压0.60 kN/m2（折算基本风速31米/秒）；下大陈阵风风速58.7米/秒（按全世界平均值1.5倍折算10分钟平均风速为39.13米/秒），为12级风（风速32.6米/秒）但未达到其50年一遇的基本风压1.4kN/m2 （折算基本风速47.33米/秒）。说明玻璃幕墙设计风荷载取50年一遇的基本风压计算是可行的。 二怎样评价风洞试验报告 玻璃幕墙工程技术规范JG102-2003规定：“玻璃幕墙的风荷载标准值可按风洞试验结果确定；玻璃幕墙高度大于200m或体型、风荷载环境复杂时，宜进行风洞试验确定风荷载。” 有的论文提出：“风洞试验值比规范更精确”。“ 风洞试验之所以精确，因为它真正模拟表现出了风对于不同建筑物的影响”。上海中心“由国际著名风工程专家主持边界层风洞试验室完成的风洞实验。其实验数据翔实，方法可靠，结论合理。”这些论点值得商榷。 我们要认识到，风洞不能自动创造某建筑物所在地点的风环境，并得出建筑物表面各处风荷载。建筑物所在地区的风速是通过风速仪等仪器长期观测纪录、并经数理统计分析得出的；对风剖面还要用高桅塔或高空气球来测得不同高度风速后进行数理分析、回归成公式来表述。因此不是风洞创造预定的风环境，而是人根据长期观测资料的分析结果确定风环境有关参数，风洞试验时在风洞中摸拟大风边界层流场，风洞中摸拟的风环境与再现的预计风环境近似程度完全取决于人对风环境有关参数的理解和运用。如果风环境参数选择不当，则模拟的风环境与预定情况大相径庭。同时还要指出风洞试验的结果主要是体型系数来流风压与建筑表面实际（压）吸力的比值，也有的风洞试验可在风洞中的各高度调整风速来测得不同高度的压力系数(即体型系数与风压高度变化系数近似乘积)，各处的风荷载是将测点的压力系数乘以风洞对应点风速换算成实际风环境中风速计算出来的风压，即风荷载是计算值，而不是直接从风洞试验中得到，在计算中采用的风环境计算参数取值直接影响风荷载计算结果。 上海中心风洞试验报告中“对上海风环境进行研究后，在其风洞试验报告所选用的梯度风风压为1.5KPa。这与按规范GB50009中上海地区50年回归期基本风压0.55 KPa，并经风压风速转换后利用规范公式-2推导的结果比较，的梯度风风压结论介于地粗面糙度A类B类之间，而不是通常认为的陆家嘴地区为地粗面糙度C类。”上海地区基本风压0.55 KPa是根据上海气象台历年（50年以上）来的最大风速记录，经统计分析确定的（规范对梯度风高度分别规定为hTa=300m、hTb=350m、hTc=400m、hTd=450m）。上述风洞试验报告所选用的梯度风风压为1.5KPa，没有说明梯度风高度取多高，梯度风风速用什么方法（仪器），经过多少（几十）年、取得多少（几十、几百、几千、几万-）个样本，用什么方法得出的。怎样得出比规范更精确的结论的。 在大气边界层内，风速随离地面高度而增大。在大量观测资料积累的基础上，基于相似理论得出的近地层的风速廓线(剖面) 近似符合指数规律，尽管这种方法具有思路清析、概念明确、易于操作的特点，但从对若干个有100m以上的超高层建筑地区不同高度最大风速记录统计分析，100m以上风速廓线(剖面)并不符合指数规律，而是呈抛物线或多项式曲线分布。风洞试验时一种方法是取全断面同一流场速度（流场速度的不均匀性小于2%），试验的结果主要是体型系数（来流风压与建筑表面实际（压）吸力的比值），用此体型系数乘以风压高度变化系数和用风洞对应点风速换算成实际风环境中风速计算的风压的结果即为设计风荷载（阵风还考虑阵风系数）。另一种方法是风洞试验时，在风洞中试验区前设挡板、百页、搁栅、滤网等使试验区风洞剖面上、下各点风速不同，并使风洞风剖面符合规定的指数规律，试验的结果测得不同高度的压力系数(即体型系数与风压高度变化系数近似乘积)，测点的压力系数乘以风洞对应点风速换算成实际风环境中风速计算出来的风压，得出风荷载值，但是风剖面取不同指数值，会得出不同结果。例如上海中银（浦东国际金融）大厦风洞试验，同济大学取=0.16（基准点取为350 m、基准点风压3.8 KPa），得230m处风荷载为7KPa，上海建筑科学研究院取=0.18（基准点取为230 m、基准点风压1.65KPa），得230m处风荷载为7.49KPa，如果将上海建筑科学研究院取=0.18用算换公式C=（230/10）0.16（230/10）0.18=0.939，7.490.939=7.037.00KPa。上海中心风洞试验报告报告的“风洞试验值与按规范公式计算结果不同，按规范公式计算风压随楼层高度而升高，在400米处，即规范的（C类）梯度风高度趋于平稳。但风洞试验显示风压在260米处达到最大，然后开始随高度上升平稳下降”（也有部分风洞试验报告有类似报告）。不过上述风洞试验报告未说明风洞试验区风洞风剖面指数取值（按C类还是介于地粗面糙度A类B类之间）。风洞试验值与按规范公式计算结果不同，形成这种差异的原因还不能确定，是来流风速对高层建筑的效应就是这样，还是风洞中风环境（有风洞壁约束）与自然界风环境（自由流通）的差异形成的，谁更精确要用实践是检验真理的唯一标准来评价，即在进行过风洞试验的建筑上每隔一定高度，同时设风速仪和风压板，测出某一高度大气流场风速和同一高度建筑上风压值，积累观测资料得出更精确的结论。 风压是速度压，风速只是代表在自由气流中某点的风速，房屋建筑设计时不能直接以该风速作为结构荷载，因为房屋本身并不是理想地使原来的自由风流停滞，而是让气流以不同方式在房屋表面绕过，因此房屋对气流形成某种干扰，要完全从理论上确定气流影响的物体表面的压力，目前还是做不到。一般都是通过试验的方法确定风作用在建筑物表面所引起的压力(吸力)与来流风压的比值，即风荷载体型系数，它表示建筑物表面在稳定风压作用下的静态压力分布规律，主要与建筑物的体型与尺度有关(荷载规范共列出38种基本体型)，一些高层建筑采用一些特殊的体型（非基本体型），且不同高度采用不同的截面形状，沿高度变化的截面风压分布复杂多变，例如正负风压系数都出现在双园弧面尖角拐角，双园弧面与过渡段交接处的尖角上有极强的压力脉动等，这些分布规律在荷载规范风荷载体型系数表中是查不到的，需要通过风洞试验来验证和确定。 风洞试验用模型为实际尺寸的1/2001/400，如1/400模型上最外一测点距边5mm，它反映的是建筑上距边2m处的风压值，风压值在边角部变化很快，测点微小的变化即会引起较大的偏差，就是说风洞模型在边角部的读数有可能与实际值存在偏差，因此，对于边角部风压值要在风洞试验值的基础上考虑适当调整。建筑结构荷载规范GB50009指出：“对封闭式建筑物，考虑到建筑物内实际存在的个别孔口和缝隙，以及机械通风等因素，室内可能存个在正负不同的气压”。“验算围护构件及其连接的强度时，可按下列规定采用局部风压体型系数-二、内表面 对封闭式建筑物，按外表面风压的正负情况取-0.2或0.2。”而风洞试验只反映外表面的正负风压，因此设计时要在风洞试验值的基础上考虑内表面局部风压体型系数。建筑结构荷载规范GB50009指出：“当多个建筑物，特别是群集的高层建筑，相互间距较近时，宜考虑风力相互干扰的群体效应；一般可将单独建筑物的体型系数s乘以相互干扰征增大系数，该系数可参考类似条件的试验资料确定；必要时宜通过风洞试验得出。”当周围有较多高层建筑时，这一群体对风产生特定的群体干扰因而形成了特定的风环境，对所设计的高层建筑也会产生影响，受到群体干扰影响时，对称的截面形状会出现并不对称的风压分布，特别是上游和下游建筑物对气流产生的干扰造成群体干扰影响下的气流特性与单体有很大差别，其风压分布复杂多变，而我国现行规范未考虑群体干扰的影响因素，这些分布规律在荷载规范风荷载体型系数表中是查不到的，需要通过风洞试验来验证和确定。必须指出风洞试验时，群体干扰效应必须采用最不利组合，例如上海中银（浦东国际金融）大厦风洞试验时，进行了有或无交银大厦的对比试验，无交银大厦时北面邻紧交银大厦大面上风压有所增大，有交银大厦时，由于交银大厦的存在，+143米近边缘处局部风压系数增大近4倍。因此，风洞试验时，不仅要考虑现有建筑布局，而且要考虑将来建筑布局变化后的不利影响，取最不利组合。 7.3 风荷载体型系数 当多个建筑物，特别是群集的高层建筑，相互间距较近时，宜考虑风力相互干扰的群体效应；一般可将单独建筑物的体型系数 s 乘以相互干扰增大系数，该系数可参考类似条件的试验资料确定；必要时宜通过风洞试验得出。验算围护构件及其连接的强度时，可按下列规定采用局部风压体型系数 s：一、外表面1正压区按表 采用；2负压区 对墙面，取 -1.0； 对墙角边，取 -1.8； 对屋面局部部位（周边和屋面坡度大于 10的屋脊部位），取 -2.2； 对檐口、雨篷、遮阳板等突出构件，取 -2.0。 注：对墙角边和屋面局部部位的作用宽度为房屋宽度的 0.1 或房屋平均高度的 0.4，取其小者，但不小于 1.5m。二、内表面 对封闭式建筑物，按外表面风压的正负情况取 -0.2 或 0.2。 注：上述的局部风压体型系数 s(1) 是适用于围护构件的从属面积 A 小于或等于 1m2 的情况，当围护构件的从属面积大于或等于 10m2 时，局部风压体系系数 s(10) 可乘以折减系数 0.8，当构件的从属面积小于 10m2 而大于 1m2 时，局部风压体系系数 s(A) 可按面积的对数线性插值，即s(A)s(1)s(10)s(1)logA附录A 风荷载体型系数 风荷载体型系数应根据建筑物平面形状按下列规定采用： 1 矩形平面 2 L形平面 3 槽形平面 4 正多边形平面、圆形平面 5 扇形平面 6 梭形平面 7 十字形平面 8 井字形平面 9 X形平面 10 艹形平面 11 六角形平面 12 Y形平面 （英文版 ） Two regulations promulgated for implementation is in the party in power for a long time and the rule of law conditions, the implementation of comprehensive strictly strategic plan, implementation in accordance with the rules and discipline to manage the party, strengthen inner-party supervision of major initiatives. The two regulations supporting each other, the adhere to a positive advocate, focusing on morality is of Party members and Party leading cadres can see, enough to get a high standard; around the party discipline, disciplinary ruler requirements, listed as negative list, focusing on vertical gauge, draw the party organizations and Party members do not touch the bottom line . Here, the main from four square face two party rules of interpretation: the first part introduces two party Revised regulations the necessity and the revision process; the second part is the interpretation of the two fundamental principles of the revision of laws and regulations in the party; the third part introduces two party regulations modified the main changes and needs to grasp several key problems; the fourth part on how to grasp the implementation of the two regulations of the party. and revised the necessity and revised history of the CPC Central Committee the amendment to the Chinese Communist Party members and leading cadres honest politics several guidelines and column 1 by 2015 to strengthen party laws and regulations focus. Two party regulations revision work lasted a Years, pooling the wisdom of the whole party, ideological consensus, draw historical experience, respect for the wisdom of our predecessors, which reflects the unity of inheritance and innovation; follow the correct direction, grasp the limited goals, adhere to the partys leadership, to solve the masses of the people reflect a focus on the problem. The new revision of the and , reflects the partys 18 and the eighth session of the third, the spirit of the fourth plenary session, reflecting the experience of studying and implementing the General Secretary Xi Jinping series of important speech, reflects the partys eighteen years comprehensive strictly practice. (a) revised two regulations of the party need of in based on revised, the promulgation and implementation of January 2010, to strengthen the construction of the contingent of leading cadres play an important role. But with the party to manage the party strictly administering the deepening, has not been able to fully meet the actual needs. Content is too complicated, eight prohibition, 52 are not allowed to hard to remember, and also difficult to put into practice; the second is concisely positive advocated by the lack of prohibited provisions excessive, no autonomy requirements; the third is banned terms and discipline law, both with the party discipline, disciplinary regulations repeat and Criminal law and other laws and regulations repeat; the fourth is to clean the theme is not prominent, not for the existing problems, and is narrow, only needle of county-level leading cadres above. is in 1997 based on revision, in December 2003 the promulgation and implementation, to strengthen the construction of the party play very important role. Along with the development of the situation, which many provisions have been unable to fully meet the comprehensive strictly administering the practice needs. One is Ji law, more than half of the provisions and criminal law and other countries laws and regulations Repetition; two is the political discipline regulations is not prominent, not specific, for violation of the party constitution, damage the authority of Party Constitution of misconduct lack necessary and serious responsibility to pursue; third is the main discipline for the leading cadres, does not cover all Party members. Based on the above situation, need to and the two is likely to be more relevant regulations first amendment. By revising, really put the authority of Party discipline, the seriousness in the party tree and call up the majority of Party members and cadres of the party constitution of party compasses party consciousness. (II) two party regulations revision process the Central Committee of the Communist Party of China attaches great importance to two regulations revision . Xi Jinping, general books recorded in the Fifth Plenary Session of the eighth session of the Central Commission for Discipline Inspection, on the revised regulations made clear instructions. According to the central deployment, the Central Commission for Discipline Inspection from 2014 under six months begin study two regulations revision. The Standing Committee of the Central Commission for Discipline Inspection 4 review revised. Comrade Wang Qishan 14 times held a special meeting to study two regulations revision, amendment clarifies the direction, major issues of principle, path and target, respectively held a forum will listen to part of the province (area) secretary of the Party committee, Secretary of the Discipline Inspection Commission, part of the central ministries and state organs Department The first party committee is mainly responsible for people, views of experts and scholars and grassroots party organizations and Party members. Approved by the Central Committee of the Communist Party of China, on 7 September 2015, the general office of the Central Committee of the Party issued a notice to solicit the provinces (autonomous regions, municipalities) Party, the central ministries and commissions, state ministries and commissions of the Party (party), the General Political Department of the military, every 3 people organization of Party of two regulations revision opinion. Central Commission for Discipline Inspection of extensive solicitation of opinions, careful study, attracting, formed a revised sent reviewers. In October 8 and October 12, Central Committee Political Bureau Standing Committee and the Political Bureau of the Central Committee After consideration of the two regulations revised draft. On October 18, the Central Committee of the Communist Party of China formally issued two regulations. Can say, two laws amendment concentrated the wisdom of the whole party, embodies the party. Second, and revision of the basic principles of two party regulations revision work and implement the partys eighteen, ten eight plenary, the spirit of the Fourth Plenary Session of the Eleventh Central Committee and General Secretary Xi Jinping important instructions on the revised and , highlighting the ruling party characteristics, serious discipline, the discipline quite in front of the law, based on the current, a long-term, advance as a whole, with Bu Xiuding independent and . Main principle is: first, adhere to the party constitution to follow. The constitution about discipline and self-discipline required specific, awaken the party constitution of party compasses party consciousness, maintaining the authority of the constitution. General Secretary Xi Jinping pointed out that no rules, no side round. Party constitution is the fundamental law, the party must follow the general rules. In early 2015 held the eighth session of the Central Commission for Discipline Inspection Fifth Plenary Session of the 16th Central Committee, Xi Jinping again pointed out that constitution is the party must follow the general rules, but also the general rules. the revision of the and is Method in adhere to the regulations established for the purpose of combining rule of virtue is to adhere to the party constitution as a fundamental to follow, the constitution authority set up, wake up the party constitution and party rules the sense of discipline, the party constitution about discipline and self-discipline specific requirements. 4 second is to adhere to in accordance with the regulations governing the party and the party. The Party of rule of virtue de, mainly refers to the partys ideals and beliefs, excellent traditional style. The revised the closely linked to the self-discipline, insisting on the positive initiative, for all members, highlight the vital few, emphasized self-discipline, focusing on the morality, and the majority of Party members and the ideological and moral standards. The revised Ji method separately, Ji, Ji Yan to Method, as a negative list, emphasizing the heteronomy, focusing on vertical gauge. Is this one high and one low, a positive reaction, the strict party discipline and practice results transformation for the integration of the whole party to observe moral and discipline requirements, for the majority of Party members and cadres provides benchmarking and ruler. Third, insist on to. In view of the problems existing in the party at the present stage, the main problems of Party members and cadres in the aspect of self-discipline and abide by the discipline to make clearly defined, especially the partys eighteen years strict political discipline and political rules, organization and discipline and to implement the central eight provisions of the spirit against the four winds and other requirements into Disciplinary provisions. Not one pace reachs the designated position, focusing on in line with reality, pragmatic and effective. After the revision of major changes, major changes in the and modified and needs to grasp several key problems (a) adhere to according to regulations governing the party and party with morals in combination, for at the present stage, the leadership of the party members and cadres and Party members in existing main problems of self-discipline, put forward principles, requirements and specifications, showing Communists noble moral pursuit, reflected at all times and in all over the world ethics from high from low 5 common requirements. One is closely linked to the self-discipline, removal and no direct relation to the provisions of . the second is adhere to a positive advocate, eight prohibition 52 are not allowed to about the content of the negative list moved into synchronization amendment . Three is for all the party members, will apply object from the leadership of the party members and cadres to expand to all Party members, fully embodies the comprehensive strictly required. The fourth is prominent key minority, seize the leadership of the party members and cadres is the key, and put forward higher requirements than the ordinary Party members. Five is to simplify, and strive to achieve concise, easy to understand, easy to remember. The revised is the ruling Party since the first insists on a positive advocate forAll Party members and the self-discipline norms, moral declaration issued to all members of the party and the National Peoples solemn commitment. criterion of a clean and honest administration consists of 4 parts, 18, more than 3600 words. After the revision of the , a total of eight, 281 words, including lead, specification and Party member cadre clean fingered self-discipline norms, etc. Part 3 members low-cost clean and self-discipline, the main contents can be summarized as four must eight code. Lead part, reiterated on ideal and faith, fundamental purpose, the fine traditions and work style, noble sentiments, such as four must the principle of requirements, strong tone of self-discipline, The higher request for 6 and supervised tenet, the foothold in permanent Bao the partys advanced nature and purity, to reflect the revised standards requirements. Members of self-discipline norms around the party members how to correctly treat and deal with the public and private, cheap and rot thrifty and extravagance bitter music, put forward the four norms. Party leader cadre clean fingered self-discipline norms for the leadership of the party members and cadres of the vital few, around the clean politics, from civil servant of the color, the exercise of power, moral integrity, a good family tradition and other aspects of the leadership of the party members and cadres of the four norms to fully adapt to the strictly requirements, reflects the according to the regulations governing the law of recognition of deepening, the realization of the discipline construction and Jin Ju. is party a ruler, members of the basic line and follow. And the majority of Party members and cadres of Party organizations at all levels should adhere to the bottom line of thinking, fear discipline, hold the bottom line, as a preventive measure, to keep the partys advanced nature and purity. 1, respect for the constitution, refinement and discipline. Revised from comprehensive comb physical constitution began, the party constitution and other regulations of the Party of Party organizations and Party discipline requirements refinement, clearly defined in violation of the party constitution will be in accordance with regulations to give the corresponding disciplinary action. The original 10 categories of misconduct, integration specification for political discipline, discipline, honesty and discipline masses Ji Law and discipline and discipline and other six categories, the content of real return to Party discipline, for the majority of Party members and listed a negative list. 7 2, highlighting the political discipline and political rules. Regulations according to the stage of the discipline of outstanding performance, emphasizing political discipline and political rules, organization and discipline, in opposition to the partys leadersh