Supported by 130 steel shoring towers and wrapped in reinforced concrete panels, the partially built sphere designed to house the Academy Museum of Motion Pictures’ new 1,000-seat theater in Los Angeles looks anything but light.

但是，一旦放置了混凝土盖，钢制圆顶圆顶均附着，额外的钢筋被烧毁和支撑掉了，这个13,000吨的球似乎将“漂浮”在露天广场上方12到20英尺。

“Most of the initial ideas were not about doing a reinforced concrete ball,” says Derrick Roorda, a principal at BuroHappold, the project’s structural engineer. A sphere made of structural steel, after all, would better resist seismic forces and contribute to the design’s airy lightness. On the other hand, this particular sphere was a movie theater.

“Acoustically, the building wants to have very massive walls to isolate the interior of the theater from street noise,” Roorda says. “We had a steel structural solution but were adding a lot of worthless mass to it anyway. So we came to the solution: Let’s just make the thing out of concrete. Let’s use that mass for structural purposes and acoustic, too.”

Designed by Renzo Piano, the sphere and its rooftop terrace join a renovated 1939 Art Deco structure to form a film-industry museum complex to be completed in 2019. The buildings will include 50,000 sq ft of gallery space with a permanent exhibition tracing the evolution of moviemaking and an “Oscars experience” allowing visitors to “accept” an Oscar award.

这项耗资38.8亿美元项目的第一阶段基金会工作于2015年开始，花了两年时间。第二阶段始于6月，包括40,281平方英尺的球体的地上建筑，以及250,000平方英尺的前5月公司建筑的持续翻新和改造，将其更名为Saban Building。

Grading on a Curve

The decision to build a 125-ft-high concrete sphere brought new challenges, Roorda says. Using cast-in-place concrete, poured against formwork, would be difficult and expensive and might not yield the smooth, natural finish that Piano envisioned. To ensure a pristine exterior, the team is building most of the sphere’s outer skin with 690 precast concrete panels, each typically 4 ft wide and up to 13 ft tall.

该学院首席运营官里奇·樱桃（Rich Cherry）说，这些弯曲的面板的重量也为1-2吨，也充当模板。工人将面板悬挂在钢制框架上，并添加结构钢筋，然后将shotcrete喷在它们上，将框架锁定在面板上，并加强了shot污了。任何裸露的钢都被烧掉了，而Shotcrete的镶板墙成为建筑物的结构框架。

“这是一个非常有创意的教学,能建立一堵墙,“雪儿ry says. “Otherwise you’d be building up this curved wall, and then hanging those panels on it, which would be a lot of work. So they took a bunch of steps out of the process by just shotcreting the back of the panels.”

该项目的总承包商Matt Construction Corp.的副总裁Greg Wade也认为该技术与众不同。韦德说：“我们已经完成了shotcrete，并且已经做了预制，但是我们从来没有像这样把它们放在一起。”

To support the finished sphere, contractors built four 8-ft by 20-ft reinforced-concrete columns, extending 10-15 ft underground to a concrete pile cap. Hollow shafts within the columns allow subcontractors to run MEP services into the sphere. Each column is topped with two base isolators that allow the sphere to move up to 30 in. in any direction during an earthquake.

罗尔达说：“剧院在地面上方孤立是不寻常的。”“大多数基地孤立的建筑物，您在建筑物周围都有一种护城河。”

韦德说，球体本身位于两个12英尺乘12英尺的水平转移梁上，每个传递长90英尺长，遍布整个基础隔离器。但是，即使有圆柱和大梁，直到安装了“盖子”（非常浅的混凝土圆顶）之前，球体也无法自信。

The lid’s steel skeleton will be shaped like a wagon wheel, with concrete poured on top, starting from the center to the perimeter and locking in the entire structure, Wade says. Until then, 60,000 pieces of steel shoring support the unfinished sphere, with load cells on 15 of the 130 shoring towers to monitor any shifts in weight.

“The columns are sufficient themselves, but the building would tend to tear itself apart if we pulled those supports out now,” Roorda says. “You have these curving walls without the lid on top. Until the lid is there, if you don’t hold up the edges, the whole thing wants to unfold.”

球体的盖子还旨在容纳计划在建筑物的屋顶露台上计划的钢和玻璃圆顶。韦德说，圆顶的玻璃是根据单独的合同建造的，是由一家德国公司定制的。圆顶钢肋骨内部的张紧电缆将有助于将其固定在一起，并在墙壁中嵌入圆顶，并具有玻璃的四分之一英寸公差。仅圆顶将重350吨，并可以向外部空气开放。

Bridging the Gap

Three 64-ft-long steel-and-glass bridges will connect the sphere to the six-story Saban Building. The 78-year-old former department store is being restored with original materials such as Italian gold-leaf mosaic tile for its iconic gold column and shell-indented limestone from Texas.

Crews are chipping out concrete and installing structural collectors tied into the building’s new shear walls, while the structure itself will be supported by 216 micropiles drilled down 60 ft, Cherry says. Workers are exposing original concrete with a wood grain pattern from the original formwork in the 1930s.

桥梁构成了艰巨的地震挑战，因为这两座建筑物将以不同的方式颤抖。韦德说，基本隔离器将允许球体移动，而萨班建筑的改造旨在限制运动。桥梁将锚定在Saban建筑物上，并设计为枢轴，在发生地震时与球体一起移动。

罗尔达说：“由于剧院是孤立的，因此至少相对于普通建筑物，它会经常移动。”“然后，这些桥梁必须滑动并旋转，并允许两座建筑物彼此独立移动。”

罗尔达说，同样的原理将适用于计划在球体侧的室外钢楼梯。该团队考虑只是悬挂剧院的楼梯，以便他们可以在地震期间滑动地面，但选择添加一个旨在随着球体移动而旋转和旋转的细分市场。

Deciding where to place the bridges was a challenge as well, since the space between the upper bridge leading from the Saban Building to the rooftop terrace and the lower bridge into the theater needed to accommodate the theater’s 66-ft by 33-ft screen. Like most aspects of the project, the entrance to the theater will be unconventional, with audiences traveling through the historic building, crossing a bridge and entering the theater beneath the screen itself.

The challenges posed by the theater’s design demand solutions that seem counterintuitive, Roorda says. “People’s normal understandings of how buildings work don’t necessarily apply with this one.”