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，洛杉矶的建筑条例仍然拒绝，所有75英尺以上的建筑，要在消防部门批准后的方位设置应急直升机迫降设施。1974年通过该法律的目的，是让摩天大楼更加安全性，这在相当大程度上是受到了巴西一场惨烈火灾的影响。但我们都告诉，只不过有许多更佳的方法，可以让美国银行（U.S. Bank）大厦这样的地标性建筑更加安全性。最近，洛杉矶宣告中止这项拒绝摩天大楼必需设计为平顶的政策，我回应要求回应青睐。
这项政策对各地的高层建筑有相当大的糅合意义。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【沦为教授之前，笔者曾在SOM-Chicago建筑事务所（原Skidmore, Owings Merrill建筑事务所）兼任建筑师】，我很确切，比起低层建筑，安全性对于高层建筑来说更为最重要，因为高层建筑有更加多居住者，而且高层建筑本身的耗资也更为高昂。此外，我也很确切，如果经过合理的设计和修建，摩天大楼在某些方面比中低层建筑更加安全性。
摩天大楼的混凝土芯，可以忍受强风和地震时的极端侧向力和纵向载荷。摩天大楼的屏蔽安全性设施还包括灭火装置，以及可以必要相连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年世贸中心大厦坍塌之后，人们找到了高层建筑安全性规定的严重不足。
美国国家标准与技术研究所（NIST）得出结论的结论是，如果大楼围观人的情况下遭遇攻击，全部撤离必须三个多小时。在这个过程中，14,000人，即全部居住者的28%，不会因为楼梯间容量严重不足而遇难。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特别强调，时间是撤离的关键。
而楼宇停机坪对撤离时间的影响微乎其微。直升机迫降、登机和降落都必须时间。而且，直升机每次仅有能载运极少数摩天大楼居住者。
研究表明，由于大火产生的热量和浓烟，即便直升机可以相似世贸中心大厦的屋顶（楼宇停机坪已被停止使用），也无法迫降。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:很少被中用的直升机停机坪，可能会强化人们的安全感，除此之外毫无用处。NIST的研究敦促更加明智地用于建筑设计构建安全性。
这些设计要素还包括：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).假设整栋建筑都必须撤离。按照惯例，高层建筑的建造者不会假设将再次发生“分阶段撤离”。当一层再次发生火灾时，居住者在可以安全性回到之前，应当再行撤离到邻近楼层。世贸中心大厦坍塌证明，在应急情况下，高层建筑的居住者更加期望全部撤离。
NIST建议，所有高度多达420英尺的非居住于用摩天大楼，应当设置三个电梯间，且耐火材料应当需要忍受每平方英尺1,000磅的压力（再次发生炸弹攻击、煤气外泄或其他类似于事件时）。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.容许部分上班族在应急情况下用于电梯。按照惯例，在应急情况下，高层建筑的电梯专供消防人员用于。
NIST建议，建筑电梯不应需要忍受火灾和混凝土芯结构损毁。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.用于黑暗中可闪烁的标志命令楼梯间与应急出口。听得一起很非常简单，但并非所有建筑都有这样的标记，特别是在是在2000年之前修建的建筑。
911事件的悲剧再次发生5年后，纽约市规定在楼梯间设置闪烁标识，纽约因此沦为第一个有类似于规定的大城市。目前，多达1,500栋建筑设置了类似于标志，但这在美国的高层建筑中仅有占到一小部分。
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.如果一个城市使用了这些建议，并且拒绝高层建筑设置避难层、视频监控和自动灭火系统，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，限制对直升机停机坪的拒绝，也可以使建筑师们设计出更有意思的屋顶天台。
直升机停机坪最少必须50x50英尺的空间，而且周围一般来说要成立25英尺的缓冲区。这造成各种大同小异、四四方方的屋顶，占有了洛杉矶的天际线。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.除了失礼美感外，另设直升机停机坪的四方屋顶，也错失了利用可持续功能创立“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，在屋顶设计可以搜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.对于限制摩天大楼楼顶直升机停机坪的规定，我们须担忧，恰恰相反，这将给我们带给许多益处。
洛杉矶人会设计出有哪些有创新的摩天大楼呢？我很期望。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）城市规划与政策系由教授。本文原刊出于信息交流网站Zocalo Public Square。
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