报告题目-1：Special Topics on Bridge Engineering
报告人：Professor Mo Yilung
In this seminar the following issues in bridge engineering will be discussed.
Issue 1: End cracks in prestressed concrete girders. Prestressed concrete I-beams are used extensively as the primary superstructure elements in Texas highway bridges. A commonly observed problem in these beams is the appearance of end zone cracking due to the prestressing forces, thermal effects of hydration, and secondary effects of shrinkage and temperature variation. Even though a large quantity of transverse steel reinforcement is provided in the end zone, the cracking problem persists. The research was targeted to develop a workable steel fiber reinforced concrete mix that would be capable of partially or completely replacing the dense traditional reinforcement and eliminating cracking in the end zone.
Issue 2: Steel Fiber Replacement of Mild Steel. In traditional prestressed concrete beams, longitudinal prestressed tendons serve to resist bending moment and transverse mild steel stirrups are used to carry shear forces. Producing and placing stirrups, however, requires costly labor and time. To overcome these difficulties, it is proposed to replace the stirrups in prestressed concrete beams with steel fibers. This replacement concept was shown to be feasible in a TxDOT sponsored project recently completed at the University of Houston (UH).
Issue 3: Rational Shear Provisions. Prestressed concrete I-beams are used extensively as the primary superstructure components of bridges in Texas highways. This research intends to solve one of the most troublesome problems in prestressed concrete beams: shear. Central to the problem is the lack of a rational model to predict the behavior of prestressed concrete structures under shear and the various modes of shear failures. Because of this deficiency, all existing shear design provisions, including those in the ACI Codes and ASSHTO Specifications, are empirical, complicated and have severe limitations. Based on our research, a set of rational shear design provisions will be presented that has also been extended to high strength concrete bridge girders.
Issue 4: Skew Reinforcing in Inverted-T Bridge Caps. Reinforced concrete inverted-T bridge caps are used extensively in Texas bridges. Many of these bridge structures must be skewed, some in excess of 45 degrees. Faster and easier construction could be obtained if skewed transverse reinforcing steel is utilized. Accordingly, there is a concern that whether using skewed transverse reinforcement will provide reasonable structural behavior for the skewed inverted-T bridge cap in term of overall cracking occurrence and structural performance. This presentation will the answer.
Issue 5: Non-Contact Splices at Drilled Shaft to Bridge Column Interface. Use of the contact lap splices of the reinforcement is common for the construction of reinforced concrete structures. It is now often required to provide a reinforcing steel splicing arrangement with non-contact lap splices for the connection of non-circular bridge columns interfacing directly with circular drilled shafts. The general requirement of a splice is to transfer the forces from one rebar to another without spalling of surrounding concrete and large cracks. Accordingly, there is concern that whether the non-contact splices at drilled shaft to bridge column connection is safe and cost-effective. We will discuss this concern in this seminar.
报告题目-2：A three-dimensional explicit constitutive model for high-fidelity simulation of RC and SC structures