钢结构的济南雨棚设计该怎么做？、

　　How to design a steel structure canopy in Jinan? 、

　　想到此前在光伏车棚结构方案比选时涉及到一种结构体系——自平衡拉杆系统。这个看似简单的结构体系却还隐藏了不少结构概念，现在仔细挖一挖其实也别有一番风味！生活也当这样，哪有那么多的高光时刻，光鲜亮丽的外表下何尝不是更多的苦楚与孤独，还是当学会在朴素无华中寻得峰回路转的那份甘甜。你我皆为庸人，何必自扰之。

　　Previously, when comparing photovoltaic carport structural schemes, a structural system called the self balancing pull rod system was involved. This seemingly simple structural system still hides many structural concepts, and now digging it up carefully actually has a unique flavor! Life should be like this, where there are so many shining moments, beneath the glamorous appearance is not more pain and loneliness, or the sweetness of learning to find twists and turns in simplicity. You and I are both mediocre, why bother ourselves.

　　尘埃落定，我想好好翻一翻林同棪大师的《结构概念与体系》，去追忆一下十多年前懵懵懂懂的感觉，找找那会的激情澎湃，追寻大师笔下的结构概念。

　　The dust has settled, and I want to take a good look at Master Lin Tongyan's "Structural Concepts and Systems", to reminisce about the naive feelings of more than ten years ago, to find the passion and excitement of that time, and to pursue the structural concepts in Master Lin's works.

　　峰回路转，我还想用心去多读读书，不分类别。回想一下，毕业后还真没有正儿八经读过几本除了以外的书籍。一直苦苦追寻的究竟为我带来了什么呢？那么功利的学习竟也迎来了这个行业真正的寒冬！多么的讽刺和可笑。

　　The road has turned, and I still want to read more books with my heart, regardless of category. Looking back, I haven't really read a few books outside of my major after graduation. What has the profession that I have been relentlessly pursuing brought me? So utilitarian learning has also ushered in the real winter of this industry! How ironic and ridiculous.

　　云淡风轻，我还想好好陪陪家人，收回自己那仿佛永远长不大的那副稚嫩与臭脾气，在这里的用心的投入可能才会有更多更好的正向反馈。

　　The clouds are light and the wind is gentle. I still want to spend time with my family and take back the immature and bad temper that seems to never grow up. Only by investing my heart here can there be more and better positive feedback.

　　NO.1 结构体系

　　NO.1 Structural System

　　一个完整的结构大体少应有几大元素：基础、竖向构件、水平构件，此为主干，其他皆为枝叶。我们一切的行为都在确保主体平衡的前提下，让枝叶更为“茂盛”，可以是花枝招展，争相斗艳；也可以是温文尔雅，她红仍她红，她艳仍她艳。

　　A complete structure generally should have at least a few major elements: foundation, vertical components, and horizontal components, which are the backbone and the rest are branches and leaves. All of our actions are based on ensuring the balance of the subject, making the branches and leaves more "lush", which can be colorful and competing for beauty; It can also be gentle and refined, she is still red, she is still beautiful.

　　室外雨棚可以算是一个典型的结构小品，结构即建筑，所见即所得！所以如何落得轻巧是结构工程师需要考虑的问题。除了主要的梁柱承重构件外，我们会加一些拉/压杆来寻求新的内部平衡。

　　An outdoor canopy can be considered a typical structural piece, where the structure is the building and what you see is what you get! So how to achieve lightness is a key consideration for structural engineers. In addition to the main load-bearing components of beams and columns, we will add some tension/compression bars to seek new internal balance.

　　对以上几种方案进行计算分析，从构件应力和变形角度比较不同，可以看出方案一在两个维度都是。柱底反力皆相同，这也验证了，拉压杆不过是改变了体系内部的内力，对柱脚而言没有帮助。

　　Through calculation and analysis of the above schemes, it can be seen that Scheme One is optimal in both dimensions from the perspectives of component stress and deformation. The reaction force at the bottom of the column is the same, which also verifies that tension and compression bars only change the internal forces of the system and are not helpful for the column base.

　　独柱悬挑受力简单明确，但我们可以换个角度来看结构体型的优化。道理很简单，想象你抱着小孩的时候，是不是会不自觉通过微微后仰去调整来保持新的平衡。这也类似结构概念设计耳熟能详的确保结构质心与刚心应尽量重合，那是解决结构扭转问题。而我们现在解决的是荷载中心与结构抵抗能力尽量吻合，解决的是不平衡荷载倾覆问题。

　　The force acting on a single column cantilever is simple and clear, but we can look at the optimization of the structural shape from a different perspective. The reason is simple. Imagine holding a child and unconsciously adjusting your center of gravity by leaning back slightly to maintain a new balance. This is also similar to the well-known structural concept design of ensuring that the center of mass and stiffness of the structure should coincide as much as possible, which is to solve the problem of structural torsion. What we are currently solving is to align the load center with the structural resistance capacity as much as possible, and to address the problem of unbalanced load overturning.

　　立柱倾斜一定角度后，可以看出拉压杆应力变化较小，主要是下柱应力有了较大改观，由612减小到了464，柱底弯矩由128减小到100，总体而言减小幅度约25%，效果很明显。仅改变下体型没想到效果竟如此明显，这不比简单的去抠应力比来的更畅快吗？而且建筑佬说不定更喜欢这种“搔首弄姿”的体态，哈哈！

　　After tilting the column at a certain angle, it can be seen that the stress change of the tension compression rod is relatively small, mainly due to a significant improvement in the stress of the lower column, which decreased from 612 to 464, and the bending moment at the bottom of the column decreased from 128 to 100. Overall, the reduction is about 25%, and the effect is very obvious. I didn't expect the effect to be so obvious just by changing my body shape. Isn't it more enjoyable than simply removing the stress ratio? And maybe architects would prefer this kind of "posing" posture, haha!

　　NO.2 荷载不利布置

　　NO.2 Unfavorable load arrangement

　　记得在结构静力手册里有一个篇幅讲到活荷载的不利布置，常用的软件如pkpm或是yjk其实也有活荷载不利布置的黑匣子选项。许多人知道可能那么回事，却在实操中往往容易忽略它的存在。如此，被遗忘的角落可能会让你瑟瑟发抖、夜不能寐。想想那些轰然崩塌的结构不正是在人的不经意间发生的吗？

　　I remember there is a section in the structural static manual that discusses the unfavorable arrangement of live loads. Commonly used software such as pkpm or yjk also have black box options for unfavorable arrangement of live loads. Many people know that it may be the case, but often overlook its existence in practice. So, the forgotten corners may make you shiver and unable to sleep at night. Isn't the sudden collapse of those structures happening unintentionally by humans?

　　为什么要考虑荷载不利布置，因为对称的荷载在某些效应上是可以彼此平衡的，那么荷载的不利布置就是不均匀导致了体系的不平衡。

　　Why consider the unfavorable arrangement of loads? Because symmetrical loads can balance each other in certain effects, so the unfavorable arrangement of loads leads to the imbalance of the system due to unevenness.

　　拉压杆体系

　　Tension compression rod system

　　对于位移控制，我们主要关注的有两个，一是竖向挠度，二是水平向侧移。不同结构/规范对应构件控制的变形限值也不大相同。另外变形要看相对值，而非值，这就是要理解构件控制变形的内涵。

　　For displacement control, we mainly focus on two aspects: the maximum vertical deflection and the maximum horizontal lateral displacement. The deformation limits controlled by components corresponding to different structures/specifications are also not the same. In addition, deformation should be based on relative values rather than absolute values, which is to understand the connotation of controlling deformation of components.

　　拉杆需要注意张紧即刚度，否则你是你，我是我，好似不识！见过现场拉杆居然还有出现下垂现象的，就好比预应力梁忘记张拉一般，这就和设计假定存有天壤之别了！所以对于拉杆设计，一定要确保拉杆有效，一是实际受力是作为拉杆出现的，别考虑受压刚度；二是施工是按拉杆的要求来处理的。若拉杆失效，那么受力体系有变化。

　　Attention should be paid to the tension and stiffness of the pull rod, otherwise you are me and I am you, it seems like I don't know! I have seen the phenomenon of sagging of the tension rod on site, just like forgetting to tension the prestressed beam, which is completely different from the design assumption! So for the design of the tension rod, it is necessary to ensure that the tension rod is effective. Firstly, the actual force is acting as a tension rod, without considering the compressive stiffness; The second is that construction is carried out according to the requirements of the pull rod. If the pull rod fails, there will be a change in the force system.

　　计算假定与实际施工是否相符一直是钢结构设计与施工需要关注的事情，比如上面提到的刚接与铰接边界条件和拉杆设计预张力失效的情况。

　　Whether the calculation assumptions match the actual construction has always been a key concern in the design and construction of steel structures, such as the rigid and hinged boundary conditions and the failure of pre tension in tension rod design mentioned above.

　　结构敏感性

　　Structural sensitivity

　　结构敏感性分析主要从刚度着手，和控制挠度一样的思路，主要关注横梁顶点位移及柱顶侧移。

　　Structural sensitivity analysis mainly starts from stiffness and follows the same approach as controlling deflection, focusing on the displacement of beam vertices and the maximum lateral displacement of column tops.

　　通过分析我们知道了以下几个特征：

　　Through analysis, we have learned the following characteristics:

　　梁的竖向挠度控制不是它自身，实际起作用的是柱及拉杆刚度，所以当出现竖向挠度不够的情况不应该是优先去加大梁截面尺寸，这种不仅不经济且改善不可观；

　　The vertical deflection control of a beam is not its own function, but rather the stiffness of the column and tension rod. Therefore, when there is insufficient vertical deflection, it should not be prioritized to increase the beam section size, which is not only uneconomical but also not significantly improved;

　　柱脚斜杆对于结构侧向刚度有一定的影响，无斜杆结构为完全悬臂柱方案，斜杆将柱敏感系数一下降低50%，显然拉杆方案更为经济有效。

　　The diagonal braces at the column base have a certain impact on the lateral stiffness of the structure. The structure without diagonal braces is a fully cantilevered column scheme, and the diagonal braces reduce the sensitivity coefficient of the column by 50%. Obviously, the tension rod scheme is more economical and effective.

　　在侧移和竖向变形两个维度，柱倾斜方案构件敏感系数较竖向方案更小，说明该方案是有效的。

　　In terms of lateral displacement and vertical deformation, the sensitivity coefficient of the components in the column inclination scheme is smaller than that in the vertical scheme, indicating that this scheme is effective.

　　综上，我们再次验证了拉压杆的存在只解决了结构体系内力分配的问题，对整个系统来说它仍属于一个“悬臂柱”，我们从荷载传递角度/力流的角度来分析与设计，可能会让我们设计更为。

　　In summary, we have once again verified that the existence of tension compression bars only solves the problem of internal force distribution in the structural system. For the entire system, it still belongs to a "cantilever column". We analyze and design it from the perspective of load transmission/force flow, which may make our design more efficient.

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