For 40 years, Los Angeles’ building code has required all buildings 75 feet and taller to have a rooftop emergency helicopter landing facility in a location approved by the fire chief. The idea in 1974, when the law was passed, was to make skyscrapers safer, in part as a reaction to a catastrophic fire in Brazil. But we know now there are better ways to make structures like the landmark U.S. Bank tower safe. I, for one, am cheering for the recently announced end of a policy requiring flat-topped buildings in Los Angeles. It’s a policy that holds lessons for tall buildings everywhere.
40年来，洛杉矶的建筑条例一直要求，所有75英尺以上的建筑，要在消防部门批准的位置设置紧急直升机降落设施。1974年通过该法律的目的，是让摩天大楼更安全，这在很大程度上是受到了巴西一场惨重火灾的影响。但我们都知道，其实有许多更好的方法，可以让美国银行（U.S. Bank）大厦这样的地标性建筑更安全。最近，洛杉矶宣布终止这项要求摩天大楼必须设计为平顶的政策，我对此决定表示欢迎。这项政策对各地的高层建筑有相当大的借鉴意义。

As an urban planner and architect (before becoming a professor, I was an architect at SOM-Chicago, the former Skidmore, Owings & Merrill), I know safety is more critical in tall buildings than in low-rise structures because tall buildings host a greater number of inhabitants and are themselves expensive investments. I also know that, if appropriately designed and built, skyscrapers are safer in many respects than low-rise and mid-rise buildings. They have concrete cores that are designed to withstand the extreme lateral forces and loads that occur during high winds and earthquakes. Fire safety systems in skyscrapers include sprinklers and wet and dry standpipes, to which firefighting hoses can be connected.
作为一名城市规划师和建筑师【成为教授之前，笔者曾在SOM-Chicago建筑事务所（原Skidmore, Owings & Merrill建筑事务所）担任建筑师】，我很清楚，相比低层建筑，安全性对于高层建筑来说更加重要，因为高层建筑有更多居住者，而且高层建筑本身的造价也更加不菲。此外，我也很清楚，如果经过合理的设计和建造，摩天大楼在某些方面比中低层建筑更安全。摩天大楼的混凝土芯，可以承受强风和地震时的极端侧向力和横向载荷。摩天大楼的防火安全设施包括洒水装置，以及可以直接连接消防软管的湿式和干式竖管。
Codes for tall building safety were found to be deficient following the World Trade Center collapse in 2001. The National Institute of Standards and Technology concluded it would have taken more than three hours to evacuate the buildings if they had been full of people at the time of the attacks. In the process, 14,000 people – 28% of the occupants – would have died because of insufficient stairwell capacity.
2001年世贸中心大厦倒塌之后，人们发现了高层建筑安全规定的不足。美国国家标准与技术研究所（NIST）得出的结论是，如果大楼挤满人的情况下遭遇袭击，全部疏散需要三个多小时。在这个过程中，14,000人，即全部居住者的28%，会因为楼梯间容量不足而丧生。
NIST stressed that time is of the essence in evacuation. And helipads have a very small impact on evacuation times. Helicopters take time to land, load people, and take off. They only take a small number of a skyscraper’s occupants each time. Research indicated that if the World Trade Center rooftops had been accessible (the helipad fell in disuse), helicopters couldn’t have landed because of the heat and smoke.
NIST强调，时间是疏散的关键。而楼宇停机坪对疏散时间的影响微乎其微。直升机降落、登机和起飞都需要时间。而且，直升机每次仅能运送极少数摩天大楼居住者。研究显示，由于大火产生的热量和浓烟，即便直升机可以接近世贸中心大厦的屋顶（楼宇停机坪已被停用），也无法降落。
Our rarely used helipads may enhance the perception of safety but do little else. The NIST study called for a smarter strategy of using building design for safety. Among the key elements:
极少被用到的直升机停机坪，可能会增强人们的安全感，除此之外毫无用处。NIST的研究呼吁更明智地使用建筑设计实现安全性。这些设计要素包括：
Assume that the full building will evacuate. Conventionally,builders of high-rises have assumed “staged evacuations” will occur. During a fire on one floor, occupants were supposed to evacuate to adjacent floors until it was safe to return. After the World Trade Center collapse, it became clear a tall building’s occupants would likely want to evacuate all at once in an emergency situation. NIST recommends that all non-residential skyscrapers that exceed 420 feet in height have three stairwells and fireproofing capable of withstanding a pressure of 1,000 pounds per square foot (in the event of a bomb, gas breakout, or something similar).
假设整栋建筑都需要疏散。按照惯例，高层建筑的建造者会假设将发生“分阶段疏散”。当一层发生火灾时，居住者在可以安全返回之前，应该先疏散到临近楼层。世贸中心大厦倒塌证明，在紧急情况下，高层建筑的居住者更希望全部疏散。NIST建议，所有高度超过420英尺的非居住用摩天大楼，应该设置三个电梯间，且耐火材料应该能够承受每平方英尺1,000磅的压力（发生炸弹袭击、煤气泄漏或其他类似事件时）。
Allow some office workers to use elevators in an emergency.Conventionally, in an emergency situation, elevators in high-rise buildings are used by firefighters only. NIST recommends building elevators that can withstand fires and structural damage in the concrete core of a building.
允许部分上班族在紧急情况下使用电梯。按照惯例，在紧急情况下，高层建筑的电梯仅供消防人员使用。NIST建议，建筑电梯应能够承受火灾和混凝土芯结构受损。
Mark stairwells and exits with glow-in-the-dark signs.As simple as it sounds, not every building has such markings, especially those built before the 2000s. New York was the first large city to require luminous markings in stairwells, five years after the 9/11 tragic events. More than 1,500 buildings now have the markings, but that’s still a small fraction of America’s tall buildings.
使用黑暗中可发光的标志指示楼梯间与紧急出口。听起来很简单，但并非所有建筑都有这样的标记，尤其是在2000年之前建造的建筑。911事件的悲剧发生5年后，纽约市规定在楼梯间设置发光标识，纽约因此成为第一个有类似规定的大城市。目前，超过1,500栋建筑设置了类似标志，但这在美国的高层建筑中仅占一小部分。
If a city adopts these recommendations – and also asks tall buildings to include refuge floors, video-camera surveillance, and automatic sprinkler systems — the safety of the skyscrapers will increase significantly.
如果一个城市采用了这些建议，并且要求高层建筑设置避难层、视频监控和自动洒水系统，摩天大楼的安全性将大幅提高。
Relaxing the requirements of a helipad also will empower architects to create more interesting rooftops. A space 50-by-50-feet wide at minimum is required for a helipad spot, plus a typical additional 25 feet around it as a buffer. This has resulted in a repetitive, boxy roof shape in the Los Angeles skyline.
此外，放宽对直升机停机坪的要求，也可以使建筑师们设计出更有趣的屋顶天台。直升机停机坪至少需要50x50英尺的空间，而且周围通常要设立25英尺的缓冲区。这导致各种大同小异、四四方方的屋顶，占据了洛杉矶的天际线。
Beyond aesthetics, boxy rooftops with helipads are really a missed opportunity to create “green” roofs with sustainable features. Now Los Angeles can do something like the spiral form in the rooftop of Shanghai Tower in Shanghai that captures rainwater. Some towers’ tops are now designated for wind turbines to harness wind energy, such as the Strata Tower in London.
除了有失美感外，设有直升机停机坪的四方屋顶，也错过了利用可持续功能创建“绿色”屋顶的机会。现在，洛杉矶的大楼也可以像上海的上海中心大厦（Shanghai Tower）一样，在屋顶设计可以收集雨水的螺旋形结构。部分摩天大楼的屋顶设计了风力涡轮机，用来风力发电，例如伦敦的斯特拉塔（Strata Tower）。
There’s nothing to fear – and much to gain – in relaxing the helipad requirement. I, for one, will be watching to see what inventive skyscrapers Angelinos come up with.
对于放宽摩天大楼楼顶直升机停机坪的规定，我们无须担心，恰恰相反，这将给我们带来许多好处。洛杉矶人会设计出哪些有创意的摩天大楼呢？我很期待。
Kheir Al-Kodmany is a professor in the Department of Urban Planning and Policy at the University of Illinois at Chicago. He wrote this for Zocalo Public Square.
本为作者海尔o阿尔孔德曼尼是伊利诺伊大学芝加哥分校（University of Illinois at Chicago）城市规划与政策系教授。本文原刊登于信息交流网站Zocalo Public Square。