轻钢结构檩条设计方案问题探讨

1、轻钢结构檩条设计问题探讨摘 要：PKPM-STS软件设计中檩条的强度及稳定计算提出一些应用 思路。关键词：PKPM-STS ；屋面檩条； 墙面檩条一、屋面檩条1简支檩条计算通常选用C型檩条，开口朝向屋脊方向。如屋面为单层或双层彩钢板夹玻璃丝棉的维护材料， 恒荷载通常 取0.150.2KN/ m2。其它材料跟据实际重量核算。活荷载取荷载规范 规定的屋面活荷载与当地雪荷载的较大值。 积灰荷载与施工荷载根据 实际情况确定。如果屋面板采用自攻螺钉与檩条固定，保证屋面板与檩条可靠连 接，能阻止檩条上翼缘侧向位移和扭转，此时只需计算檩条强度，但 这种板型因温度变形能力和防水能力较差，现在较少采用。目前采用

2、较多的是暗扣式板型，这种连接方式在温度变化较大时屋面板能产生 滑动，不宜将它假定为能阻止檩条上翼缘侧向位移和扭转，除了计算檩条强度，还需计算其稳定性。屋面檩条计算和拉条的设置有关。根据门规，当檩条跨度大于 4m时，宜在檩条间跨中设置拉条；跨度大于6m时宜在檩条跨度三分点处各设一道拉条，在屋脊处还应设置斜拉条及撑杆。在恒载活载及风压力作用下，檩条上翼缘受压，拉条应设置在檩条上翼缘1/3处。在风吸力作用下使檩条下翼缘受压，拉条不能保证檩条下翼缘的 侧向位移和扭转，如果计算时要考虑拉条能约束檩条下翼缘，此时应在檩条下翼缘1/3处同样设置拉条，所以檩条设计最好用双层拉条。2连续檩条计算通常选用Z型檩条

3、，开口朝向檐口方向。由于 Z型檩条可用搭 接形式，故可把这样的檩条假定成连续构件。(1) 采用Z型搭接连续檩条比简支檩条内力分布均匀，刚度大，可 节省用钢量。(2) 搭接连续檩条在支座处搭接区存在嵌套松弛现象 ，其刚度小 于等截面连续单檩的刚度，因此在支座处有一定弯矩释放，在跨中弯矩 有一定的增大。(3) 连续檩条整体稳定计算目前尚不完善 ，其整体稳定可利用屋 面蒙皮作用和拉条支撑系统解决。(4) 连续檩条支座处的弯矩大于跨中弯矩 ，搭接区承载能力按两 檩条的抗弯模量之和考虑是合理的，可以大大节省用钢量。(5) 连续檩条的搭接长度不宜小于跨长的10 % ,搭接长度按端跨 和中间跨的弯矩分布情况

4、分别考虑，以搭接端弯矩不大于跨中弯矩为 条件来确定搭接长度可使设计更为经济合理。(6) 用檩条兼作屋面纵向压杆，当单檩不能满足承载力要求，可用 双檩条，此方法节省用钢量。(7) 连续檩条与屋面梁的连接应采用加檩托板螺栓连接方式以 防檩条局部腹板压屈和整体倾覆。当檩条腹板高厚比较大时尚应加设厚垫片以改进其支座处的承载力(8) 般情况下，设计带隅撑的檩条时，隅撑对檩条的有利作用与 不利影响可考虑相互抵消，忽略不计，以简化设计二、墙面檩条1. 简支墙梁计算通常选用C型檩条，开口朝向根据实际情况确定。一般墙梁开 口朝上，但窗洞口下侧檩条可让檩条开口朝下布置以满足固定窗框的 需求。墙梁设计与屋面檩条类似

5、，同样要考虑墙板 拉条的约束作用。 不同的是墙板有自承重和非自承重两种，要根据具体情况具体分析。 另外。墙梁设计时根据构造条件的不同要考虑双弯矩板的影响。根据冷弯薄壁型钢结构技术规范条及条文说明，两侧挂墙板的墙梁和一侧挂墙板.另一侧没有可以阻止其扭转变形的拉杆墙 梁，可不计双力矩的影响？(即可取B=0)，此时可仅进行墙梁的强度计 算。对于风吸力作用下内翼缘的稳定性计算，与屋面檩条类似，墙板一般采用自攻螺钉与檩条固定，可认为墙板能阻止墙梁外翼缘侧向失 稳。拉条设置在墙梁内侧比增大檩条截面更经济。对于自承重墙板， 可仅在内侧设置拉条。对于非自承重墙板，宜在墙梁内外设双侧拉条， 外侧拉条可以作为墙板

6、在自重作用下墙梁的竖向支撑点。在墙板顶部和窗户下的墙梁处应同时设置斜拉条和直撑杆， 将拉力传至刚架柱或 墙架柱，底部墙梁一般固定在墙垛或矮墙上，整体稳定有保证，故底部墙梁处可不设置斜拉条和直撑杆。三、拉条的设置拉条虽小，作用不小。实际上有檩条系的压型钢板轻型变形和扭 转，减小檩条的计算长度，保证檩条的侧向稳定作用。拉条一般通过 螺栓与檩条连接，拉条与屋面板的共同作用能有效地提高檩条的整体 抗扭转度和减少外部荷载引起的扭转效应。虽然在檩条下翼缘附近有无拉条对檩条的抗弯承载力有很大影响，但当拉条强度满足后，拉条的刚度对抗弯和压弯承载力的影响可忽略。所以门规推荐拉条的最小直径取10mm，去除车丝对截

7、面的削弱及锈蚀等因素外是可行的，但 应注意：每一个坡面上的檩条是一个大的串联系统，因此檩条的受力是不均匀的，恒活载作用下离屋脊处越近的拉条内力越大，而在风吸力作用下正好相反。在檩条的设计中应考虑多根檩条由拉条串联后的 内力叠加。当房屋坡度方向较大应间隔一定数量的拉条设置一对斜拉 条，以分段传递内力。因拉条只能受拉，但拉条作为檩条的侧向支撑 点时，同时受拉和受压，因此在檐口和屋脊应布置斜拉条和撑杆，以 形成几何不变体系。撑杆按压杆设计，不宜用圆钢。Light steel purli n desig n problem discussed in this paperPick to: PKPM -

8、STS software in the desig n of purli n the stre ngth and stability calculati on of some applicati ons.Keywords: PKPM - STS; Roofi ng purli ne; The metope of purli nA, roof purli n1. The simply supported purli n is calculatedUsually choose C purli n, ridge directi on.Such as roofi ng for sin gle or d

9、ouble colored powder glass cott on material to maintain, constant load usually take 0.15 0.2 KN /. Othermaterials according to the actual weight calculation. Live load in load code for the rules of roof live load and the larger value of the local snow load. Heavy load and con structi on load accord

10、ing to the actual situati on. If roof board with self-tapp ing screws fixed and purli n, en sure roof panel and purlin connections, can prevent the purlin flange on the lateral displaceme nt and tors ion, just calculate purli n inten sity at this time, but this kind of board type deformation due to

11、temperature and waterproof ability is poorer, less used no w. Is curre ntly using more dark buckle type plate type, the conn ecti on way in large temperature cha nges in the roof plate can produce sliding, unfavorable and it can prevent the purlin is assumed on the flange lateral displaceme nt and t

12、ors ion, in additi on to the purli n stre ngth calculatio n, still n eed to calculate the stability.Roofi ng purli ne calculati on and brace is set. Accord ing to the rules, whe n the purli n spa n more tha n 4 m, appropriate is set in the purli n across brace; A time spa n is more tha n 6 m in spa

13、n purli n three locati ons in each set a brace, also should be set at roof of batter brace and poles. At constant load. Under the action of live load and wind pressure, purlin flange compressi on and brace should be set on the purli n flange 1/3. Un der the wi nd sucti on un der the acti on of the p

14、urli n flange compressi on and brace does not guara ntee purli n flange lateral displaceme nt and tors ion un der, if can brace should consider when calculating constraint purlin flange, should now under the purlin flange 1/3 place to stay with the same Sett in gs, so the purli n desig n best double

15、 brace.2. Con ti nu ous purli n calculati onUsually choose Z type purli n, ope ning directi on toward the eaves. Since Z type purlin overlap forms are available, and it can be such a purlin assumed to continu ous artifacts.(1) using lap tha n simply supported con ti nu ous purli n Z purli n internal

16、 force distributio n is uni form, stiffness big, qua ntity of steel can be saved.(2) con ti nu ous purli n overlap overlap area exists in support n ested flabby phe nomenon, its stiffness is smaller tha n the cross-secti on stiff ness of the sin gle con ti nu ous purli n, therefore had a certa in mo

17、me nt release in the beari ng, the bending mome nt in the spa n have in creased.(3) continu ous purli n overall stability calculatio n is not yet perfect, the available roofi ng env elope on overall stability and brace support system.(4) continuous purlin bending moment is greater than the cross of

18、bending mome nt of the beari ng, beari ng capacity accord ing to the two overlapp ing area purli n bending modulus of the sum of the con siderati on is reas on able, can greatly save the steel qua ntity.(5) con ti nu ous purli n of the lap len gth should not be less tha n 10% spa n len gth, the lap

19、len gth accord ing to the bending mome nt distributi on of end spa n and middle spa n were con sidered, with overlapp ing end bending moment is not greater than midspan moment for the conditions to determine the lap length can make the design more economical and reas on able.(6) made roof purli n an

20、d Ion gitud inal compressive bar, si ngle purli n whe n can not meet the requireme nt of the beari ng capacity of double purli ne are available, and this method saves the qua ntity of steel.(7) con ti nu ous purli n beam conn ecti ons should be used with the roof and purlin plate bolt connection in

21、case of purlin local web buckling and overall overtur ning. Whe n high purli n web thick ness is larger fashi on should be added a thicker gasket to improve its beari ng capacity.(8) in gen eral, the desig n with a knee brace purli n, the ben eficial effect of the knee brace to the purli n and adver

22、se effects can cel each other out, may be con sidered n egligible, to simplify the desig nSecond, metope purli n1. The simply supported beam wall is calculatedUsually choose C purli n, ope ning towards accord ing to actual situati on. Wall beam with ope ning up com mon ly, but huma nly scaled mouth

23、un derside purli ne allows purli n ope ning dow nwards arran ged to meet the n eeds of the fixed frame.Wall beam desig n and roof purli n is similar, also want to con sider wallboard. Restricti on in brace. Is differe nt pan els are self support ing and self support ing two kin ds, accord ing to par

24、ticular case is particular an alysis. In additi on. Whe n wall beam desig n accord ing to the differe nt tectonic conditions want to consider the impact of dual bending plate. Accord ing to tech ni cal specificati on for the cold bending thi n-wall steel structure 8.3.1 and provisions that, on both

25、sides of the hang hang wallboard wall beam and side wall. On the other side can not preve nt the torsional deformati on of rod wall beam, but excludi ng double mome nt of impact? (that is, the opti on B = 0), but on ly the stre ngth of the wall beam calculati on at this time.For wi nd sucti on flang

26、e in the stability calculati on, like roofi ng purli ne, wallboard gen erally USES self tapp ing screw and purli n fixed, can thi nk outside wallboard can preve nt wall beam flange lateral in stability. Brace is set in the wall beam in side more econo mic tha n in creas ing the purli n secti on. For

27、 the beari ng wallboard, can be set up only in the in side of the brace. For non self beari ng wallboard, appropriate is set in and out of the wall beam dual lateral brace, the lateral brace can be used as wall panel in the weight of the wall beam un der the acti on of vertical support. On top of th

28、e wall panel and win dow of the wall beam should be set at the same time suspension and straight poles, would transmit the force to rigid frame colu mn or wall frame colu mn, the bottom of the wall beam fixed on the low wall or wall battleme nts com mon ly, the overall stabilityguara nteed, so the a

29、rticle did nt set at the bottom of the wall beam suspe nsion and poles.Three, brace is setBrace is small, effect. Actually have purlin is pressed steel plate light deformatio n and tors ion, reduce the purli ne len gth calculati on, en sure the lateral stability of purlin. Brace general through bolt

30、s and purlin conn ecti on, brace and roof plate can effectively improve the fun cti on of purli n of the torsi on degree of whole and reduce the exter nal load caused by the reverse effect. Although un der the purli n flange n ear any brace has a great in flue nee on the flexural beari ng capacity of purli n, but whe n meet brace inten sity, stiff ness of the brace effect on bending and bending bearing capacity can be