Development of UHPC Pi-Girder Sections for Span Length up to 41 m

Ultrahigh performance concrete (UHPC) presents many superior properties, such as advanced strength, durability, and long-term stability. The use of existing cross section geometries for materials with advanced properties results in inefficient designs and less cost-effective solutions. This study focused on developing a series of finite-element optimized sections of pi-girders to effectively utilize the superior mechanical properties of UHPC over span lengths of up to 41 m (135 ft). The research was performed using a finite-element model that has been calibrated and verified against experimental results. The optimization was progressively conducted at local, element, and structural levels. At the local level, the focus of the investigation was to find the optimal deck thickness and prevent transverse bending failure of the deck. At the element level, sectional parameters, including girder height, bulb size, web thickness, and strand layouts, were investigated to find the minimal sectional size that accommodates standard loads for a span length of 23 m (75 ft) or above. At the structural level, deflection under a live load was checked such that the bridge system using the proposed sections can meet the deflection requirements specified in guidelines. Four cross sections based on the second generation pi-girder were proposed, and a design chart was provided to facilitate preliminary design for bridge engineers.