Answering a call from the Federal Highway Administration, a group of steel-bridge advocates have introduced a new type of tub girder that requires less fabrication and installation time.
WVU的工程教授卡尔·巴尔斯（Karl Barth）说，大约五年前，与西弗吉尼亚大学和马歇尔大学一起，与西弗吉尼亚大学和马歇尔大学结合使用了短跨度钢桥联盟（PBTG）系统。“ 2009年的FHWA向我们发出了挑战，要求为140英尺或更少的钢桥开发一种具有成本效益的加速桥梁建设系统。我们探索了各种概念，从Twin-Tub Girder类型到正交甲板系统，”他说。
SSSBA organized a modular steel-bridge task group to explore the possibilities. The group, made up of more than 30 partners from the steel industry, academia, government organizations and bridge owners, developed the PBTG system in three years.
The system consists of shallow, modular galvanized trapezoidal boxes fabricated from cold-bent structural-steel plates. In practice, the concrete deck is precast on the girder, and the modular unit is shipped by truck to the bridge site.
旧系统，新优势
The pressed-brake tub-girder system concept is not new but had never been fully developed, Barth adds. “What we’re doing is taking all the advantages of a large, deep, welded tub girder and scaling [it] down to a short-span bridge system. All the bracing, welding and other details that go into a large tub girder simply couldn’t be economically deployed in short spans.”
巴特指出，虽然冷弯曲的钢制造商经常制造起重机繁荣和公用电线杆，但“它们不一定是您的传统桥梁制造商。因此，这正在为拥有大型新闻制动系统的人创建新的业务系列。”
SSSBA looked at ways to maximize girders made from the standard steel plates, typically 72 in. or 96 in. wide, made by steel mills, says Greg Michaelson, assistant professor at Marshall University. “You hit the plate with a press brake four times—two on the ends and two in the center—to get the U-shaped tub,” he says. “Then, you put shear studs on the top flange and diaphragms, add a concrete deck on top, and now that composite unit can be shipped.”
The system offers as much as a 50% reduction in fabrication costs, compared to proprietary cold-formed box-girder systems, due to cold-bending versus cutting and welding of the section, according to the SSSBA.
小组补充说，加强剂和十字架的降低。梁可用于切线和偏斜的配置以及简单且连续的跨度。
迈克尔森（Michaelson）指出，一项测试证明了吉尔德（Girder）处理300 kips负载的能力，这是行业标准的四倍。FHWA创新桥研究计划的赠款资助了爱荷华州布坎南县的第一座PBTG桥梁；它在一月份完成。布坎南县工程师Brian Keierleber说，这座380,000美元的阿米什锯木厂桥长52英尺，宽30英尺，表现良好。
“毫无疑问，我们这里有一个非常长的结构，”基尔勒伯说。“我们使用了金属螺栓固定的护栏部分，而不是现场混凝土 - 所有镀锌。取代我们许多旧结构是一项有前途的技术。”
Three more PBTG bridges are in the works in Ohio and West Virginia.
