Journal of Bridge Engineering

Heavy trucks represent a major load to highway bridges in the transportation infrastructure system. These loads are directly related to the truck weight limits of the jurisdiction, and largely determine the standard loads for bridge design and evaluation. Thus, truck weight limit is one of the major factors affecting bridge deterioration and expenditure for maintenance, repair, and/or replacement. Truck weight in this paper not only refers to the truck gross weight but also to the axle weights and spacings that affect load effects. This paper presents the concepts of a new methodology for estimating cost effects of truck weight limit changes on bridges in a transportation infrastructure network. The methodology can serve as a tool for studying impacts of such changes. The resulting knowledge is needed when examining new truck weight limits, several of which have been and are still being debated at both the state and federal levels in the United States. The development of this estimation method has considered maximizing the use of available data (such as the bridge inventory) at the state infrastructure system level. In application examples completed (but not reported herein), the costs for relatively inadequate strength of existing bridges and for increased design requirement for new bridges were found dominant in the total impact cost.

The main objective of this research was to study the effects of different specified trucks on bridge rating with the load and resistance and factor rating (LRFR) procedure. Twelve specified trucks were selected for this study, which include one AASHTO design truck, three AASHTO legal trucks, and eight state legal trucks. These rating trucks were applied on 16 selected Tennessee Dept. of Transportation bridges to obtain the LRFR ratings. The selected bridges covered four commonly used bridge types, including prestressed I-beam bridges; prestressed box beam bridges; cast-in-place T-beam bridges; and steel I-beam bridges. The research results revealed that (1) LRFR AASHTO legal load ratings factors were enveloped by the LRFR HL-93 truck ratings factors, thereby confirming the validity of the LRFR tiered approach with regard to AASHTO legal loads; (2) the lighter state legal trucks were enveloped by the HL-93 loads, whereas the heavier state trucks with closer axle spacing typically resulted in load ratings that governed over the HL-93 loads; and (3) the bridges with both high average daily truck traffic and short spans were more likely to be governed by state legal load ratings instead of HL-93 load ratings.

Structural identification via modal analysis in structural mechanics is gaining popularity in recent years, despite conceptual difficulties connected with its use. This paper is devoted to illustrating the advantages and also the indeterminacy characterizing structural identification problems for bridge structures, even in rather simple instances. In particular, an identification procedure based on modal analysis and finite-element model updating is presented for the characterization of a concrete bridge whose constructive typology is quite diffuse in the area of Friuli Venezia Giulia, Italy. Experience has suggested (so as to restrict the indeterminacy frequently affecting identification issues) resorting to all the a priori information on the system and mindfully selecting the parameters to be identified. The analysis pointed out some particularities in the modeling of bridge typology under study, otherwise not a priori detectable from an analytical point of view.

This paper presents the development and experimental validation of a multizard bridge pier concept, i.e., a bridge pier system capable of providing an adequate level of protection against collapse under seismic and blast loading (but not acting simultaneously). A multicolumn pier-bent with concrete-filled steel tube (CFST) columns is the proposed concept, and the adequacy of this system is experimentally investigated under blast loading. This paper describes simplified blast analysis, multihazard design of bridge piers, and blast experimental program and results. Additionally, the results from the blast experiments are compared with the results from the simplified method of analysis considering an equivalent single degree of freedom system having an elastic-perfectly plastic behavior. It is found that prototype bridge CFST columns can be designed to provide both satisfactory seismic performance and adequate blast resistance. It is also shown that the CFST columns exhibited a ductile behavior under blast load in a series of tests at $1∕4$ scale. Maximum deformation of the columns could be calculated using simplified analysis considering a factor to account for the reduction of pressures on the circular column and determined from this experimental program.

Covered wooden bridges and the principles of heavy timber framing by which they were built represent both a significant chapter in this country’s civil engineering heritage, and a subclass of bridges that are in immediate need of repair and rehabilitation. This work often falls on the shoulders of the municipalities who own the bridges or local consulting engineering companies, neither of which have the resources to perform state-of-the-art damage assessment analyses. This study presents two case studies in which a simplified approach to damage assessment is used. The writers explore the importance of proper condition assessments, including both field observations and load tests, to the creation of viable finite-element models that practicing engineers may use in their repair and rehabilitation of these unique structures. Experimental tests were performed on two covered bridges: Morgan Bridge in Belvidere, Vermont and Pine Grove Bridge, in Oxford, Pennsylvania, and comparisons were made to finite-element models created of those bridges. The combination of experimental and numerical tools led to the identification of several deteriorated components, including scarf joints, lapped brace joints, and retrofitted members within the bridges that may have otherwise gone undetected.

The flexural behavior of an ultrahigh-performance concrete (UHPC) was investigated through the testing and related analysis of a full-scale prestressed I-girder. A $28\mathrm{ksi}$ $\left(193\mathrm{MPa}\right)$ compressive strength steel fiber reinforced concrete was used to fabricate an $80\mathrm{ft}$ $\left(24.4\mathrm{m}\right)$ long AASHTO Type II girder containing 26 prestressing strands and no mild steel reinforcement. Intermediate and final behaviors, including cracking, flexural stiffness, and moment capacity, were investigated. Test results are compared to predictions based on standard analytical procedures. A relationship between tensile strain and crack spacing is developed. The uniaxial stress-strain response of UHPC when subjected to flexural stresses in an I-girder is determined and is verified to be representative of both the stress and flexural stiffness behaviors of the girder. A flexural design philosophy for this type of girder is proposed.

This paper describes a simple, practical, and inexpensive way of anchoring and applying the prestressing force for posttensioning of the concrete bridge superstructures. It is technically named as the lateral posttension (LPT) method. In applying the proposed new method, cable tendons are initially placed straight inside an open preformed channel or external to the cross section of the girder web. The bottom of the preformed channel is cast to match the desired final tendon profile of the prestressing path. Both ends of the tendons are embedded in the end blocks to form a dead-end anchorage system once the concrete is placed and reaches the required strength. The prestressing force is then applied by vertically deflecting the cable tendons to the prescribed profile at the bottom of the channel and locking the tendons at deflected profile. The benefits of this method lie in its simple anchorage system and easy stressing operation, thus it offers a viable posttensioning alternative. Although, further research and testing are needed before this methodology can be implemented to practice, the concept of this method opens a door for the development of a posttensioning operation that is simple, practical, and inexpensive. The accessibility for the stressing routine inspection and final adjustments makes the LPT method very useful for bridge rehabilitation and retrofit construction.

Stud shear connectors are the most widely used shear connectors in steel-concrete composite beams. The composite action of steel beam and concrete slab is effected by the stud shear properties directly. Thirty push-out tests on stud shear connectors were conducted to investigate the effects of stud diameter and height, concrete strength, stud welding technique, transverse reinforcement, and steel beam type on stud failure mode, load versus slip curve, and the shear bearing capacity. Based on the push-out test results, the stud shear mechanism was analyzed, a new expression of stud load-slip relationship was put forward, and a calculation model of stud shear bearing capacity was proposed taking into account the influences of stud diameter and height, material strength, and elastic modulus. Compared with existing models, the computed shear bearing capacities of the proposed calculation model had a better match with the experimental values.

The goal of this paper is to demonstrate the significance of the Bayonne Bridge and to identify it as a work of structural art, because its designer, Othmar Ammann (1879–1965), focused on efficiency, economy, and elegance. To understand Ammann’s ideas and his great arch bridge, we will: (1) briefly describe his educational background; (2) explore his design concept; (3) explain the behavior of the bridge through a careful structural analysis; (4) include a critical analysis of its design; and (5) reflect on lessons to be learned from Ammann. A full, modern technical study of the Bayonne Bridge has never been published. Since we are very fortunate to have one of the few complete sets of the plans, we will present an independent structural analysis to explain Ammann’s design concept and to demonstrate its efficiency in the complete form and its safety during construction.