Value-Engineering Methodology for the Selection of an Optimal Bridge System

Maintaining and enhancing the functionality of the infrastructure at an affordable cost are major challenges for decision makers, particularly given the need to cope with growing societal and transportation demands. This study introduces a systematic multi-criteria value engineering (VE) approach for the selection of a sustainable bridge system. A thorough VE analysis for a proposed long-span bridge in New Jersey, USA was carried out as a pilot study. The function analysis system technique was used to develop logical relationships between the project’s functions. A detailed 100-year life-cycle cost analysis (LCCA) was conducted. The study developed and evaluated eight alternative designs for deck and superstructure systems against set VE criteria comprising constructability, maintenance strategies, and environmental impact. A relative value index was used as an unbiased measure for the selection of the optimal structural system. With total savings of approximately 21% of the original design ($132.5 million), steel plate girders with a high-performance lightweight steel grid deck system have proven to “outvalue” the other alternatives, including the preferred preliminary alternative (PPA). Design engineers and decision makers can use this methodology as a systematic and convenient guide for the selection of economical and sustainable bridge systems. As such, it is necessary to re-evaluate the current practices and policies used for this purpose.

Aerodynamics of a Train and Flat Closed-Box Bridge System with Train Model Mounted on the Upstream Track

The aerodynamic features of a train and flat closed-box bridge system may be highly sensitive to train-bridge aero interactions. For the generally utilized railway bridge-deck with two tracks (the upstream and downstream ones), the aero interactions above are occupied-track-dependent. The present paper thus aims to reveal the aero interactions stated above via a series of wind tunnel tests. The results showed that the aero interactions of the present train-bridge system display four typical behaviors, namely, the underbody flow restraining effect, bridge deck shielding effect, flow transition promoting effect, and the flow separation intensifying effect. The above four aero interactions result in obvious reductions in the aerodynamic forces of the train in wind angle of attack α of [−4°, 12°] and in the static stall angle of the bridge-deck, and leads to sensible increases in the absolute values of the bridge aerodynamic forces in α of [−4°, 12°]. Upon comparing the results with the same train and bridge system but with the train model mounted on the downstream track, the quasi-Reynolds number effect was non-detectable when the train model was moved to the upstream track. Thus, no drag crisis and other saltatory aerodynamic behaviors were observed in the present study in α of [0°, 12°].

The Precise Temperature Measurement System with Compensation of Measuring Cable Influence

The article presents an active bridge system that enables the solution of a significant problem consisting in ensuring correct indications of temperature values in a wide measuring range for a Pt100 temperature sensor with properties defined by the standard (EN-60751 + A2). The presented active bridge system combines the properties of the measuring amplifier with the stabilization of the current value in the branch in which the Pt100 sensor was placed. The article focuses on the comparison of the temperature measurement in a typical resistance bridge and the measurement made in the developed active bridge, which has also become the subject of a patent. For the performed tests, in which the correctness of the temperature measurement system operation was verified, and on the basis of the obtained results, the quality of temperature measurements was compared in a wide range of changes.

Seismic fragility models of a bridge system based on copula method

Seismic fragility assessment widely uses a probabilistic measure for assessing the seismic performance of structural components or systems. This article proposes a copula-based seismic fragility (CBSF) method to derive the system-level damage probabilities of reinforced concrete bridges and to consider the correlation among seismic demands of components. First, the marginal distribution functions of the random variables are calibrated, and three Archimedean copula models are considered. Subsequently, the relevant parameters of the copula models are estimated using the semi-parametric maximum likelihood method. Next, the damage probabilities of a bridge system are calculated based on the joint distribution model with the most suitable copula model and the calibrated marginal distribution functions. Finally, the CBSF method is used to estimate the damage probability of a simply supported box girder bridge. The performance of the CBSF method is validated by a comparison of fragility curves obtained using the CBSF method and the probabilistic seismic demand analysis (PSDA) method. The comparative results demonstrate that the fragility curves obtained by the CBSF method are better than those obtained using the PSDA method. The proposed CBSF model can serve as a tool for assessing the seismic performance of structures and estimating the economic loss of existing bridge systems.