Tevfik Terzioglu

Experimental Investigation of a Full-Scale Spread Slab Beam Bridge

AbstractThe Texas Department of Transportation (TxDOT) uses precast prestressed concrete slab beams in a side-by-side configuration for short-span bridges in low-clearance areas. To reduce costs, a new bridge type called a spread slab beam bridge was recently developed using the same concept as spread box beam bridges in which the beams are spaced apart. A full-scale spread slab beam bridge was constructed and tested under static and dynamic vehicular loads to evaluate constructability and structural performance. The load-distribution behavior was investigated through field testing, and experimental live-load distribution factors (LLDFs) were evaluated using alignments that provided the most adverse loading cases. The measured response provides detailed experimental data to validate computational modeling techniques for this new class of bridge systems. Research findings show that spread slab beam systems provide a viable construction method for short-span bridges, and that the desired performance was ach...

Nondestructive Evaluation of Non-Strand Defects in Stay Cable Specimens

Stay cable systems are used extensively for the construction of long-span bridges owing to their inherent advantages. In most cable-stayed bridges the steel strands within the main tension elements (MTEs) are grouted to provide a corrosion protection system. However, there could be segregated grout, voids, and water accumulation/infiltration within these voids in the ducts due to poor quality of the grouting material and grouting techniques. These locations may act as initiators for the corrosion of steel strands within the ducts, which can have serious implications on the load carrying capacity and safety of cable-stayed bridges. In this investigation, several nondestructive evaluation (NDE) techniques are evaluated to determine their ability to detect grout defects within the anchorage regions, end caps, and MTEs of the stay cable system. Four stay cable specimen mock-ups with known grout defects and voids were fabricated. NDE methods that were part of this investigation included ground penetrating radar, infrared thermography, electrical capacitance tomography, impact echo, sounding, ultrasonic tomography, ultrasonic pulse velocity, low frequency ultrasound, visual testing, and borescope. While a few NDE methods could identify voids and water infiltration defects within the high-density polyethylene (HDPE) MTEs, it is evident that there is still a need for a method that is effective in detecting grout defects within the metal ducts embedded in the anchorage region and metal MTEs. Although visual testing and borescope methods are effective in identifying the defects, prior information about the location of the defects is generally required.

Design and Constructability of Spread Slab-Beam Bridges

AbstractA new bridge type called a spread slab-beam bridge was developed recently by using the same concept as that used for spread box beam bridges, in which the beams are spaced apart. This paper presents an evaluation of the new bridge system in terms of design and constructability and investigates the challenges encountered during construction. Forty-four bridge geometries were designed by using standard Texas DOT (TxDOT) slab-beam types to determine the feasible design space. One of the most aggressive geometries with widely spaced slab beams was constructed at full scale. On the basis of the research findings, it was concluded that spread slab beams with a topped panelized deck provide a viable construction method for short-span bridges. Results of a shear-design check show that the standard interface shear reinforcement must be doubled for the first quarter of the span length for more aggressive designs. Larger-than-expected camber of the precast slab beams might cause construction challenges and d...