Deck Conditions Research Articles

Corrosion behavior of low alloy steel for cargo oil tank under upper deck conditions

A simulated corrosion test apparatus was used to investigate the corrosion behavior of a low alloy steel under simulated upper deck conditions in a cargo oil tank. The estimated corrosion loss of conventional E36 class ship plate steel is 4.27 mm, which is clearly inadequate compared with the standard adopted by International Maritime Organization. Outer rust layer of specimens starts to peel off after 77 days and becomes fragmented after 98 days. X-ray diffraction, scanning electron microscopy, and Raman spectroscopy revealed that the resulting rust is composed of σ-FeOOH (the main protective phase), Fe2O3, FeS, elemental S, and FeSO4. FeSO4 in the interface of the base and rust layer leads to localized corrosion. Elemental sulfur forms on the surface of σ-FeOOH, and the quantity and size thereof increase with increasing corrosion time. Furthermore, layered elemental sulfur promotes fracture and peels off the rust layer.

A Multi-Point Tire Model for Studying Bridge–Vehicle Coupled Vibration

The contact between a vehicle tire and the road surface has been usually assumed as a single-point contact in the numerical simulation of vehicle–bridge interacted vibrations. In reality, the tire contacts the road surface through a patch instead of a single point. According to some recent studies, the single-point tire model may overestimate the dynamic amplification of bridge responses due to vehicle loadings. A new tire model, namely, the multi-point tire model, is therefore proposed in this paper with the purpose of improving the accuracy of numerical simulation results over the single-point model, while maintaining a certain level of simplicity for applications. A series of numerical simulations are carried out to compare the effect of the proposed tire model with those of the existing single-point model and disk model on the bridge dynamic responses. The proposed tire model is also verified against the field test results. The results show that the proposed multi-point tire model can predict the bridge dynamic responses with better accuracy than the single-point model, especially under distressed bridge deck conditions, and is computationally more efficient and simpler for application than the disk model.

Reduction of Biomechanical and Welding Fume Exposures in Stud Welding.

The welding of shear stud connectors to structural steel in construction requires a prolonged stooped posture that exposes ironworkers to biomechanical and welding fume hazards. In this study, biomechanical and welding fume exposures during stud welding using conventional methods were compared to exposures associated with use of a prototype system that allowed participants to weld from an upright position. The effect of base material (i.e. bare structural beam versus galvanized decking) on welding fume concentration (particle number and mass), particle size distribution, and particle composition was also explored. Thirty participants completed a series of stud welding simulations in a local apprenticeship training facility. Use of the upright system was associated with substantial reductions in trunk inclination and the activity levels of several muscle groups. Inhalable mass concentrations of welding fume (averaged over ~18 min) when using conventional methods were high (18.2 mg m(-3) for bare beam; 65.7 mg m(-3) for through deck), with estimated mass concentrations of iron (7.8 mg m(-3) for bare beam; 15.8 mg m(-3) for through deck), zinc (0.2 mg m(-3) for bare beam; 15.8 mg m(-3) for through deck), and manganese (0.9 mg m(-3) for bare beam; 1.5 mg m(-3) for through deck) often exceeding the American Conference of Governmental Industrial Hygienists Threshold Limit Values (TLVs). Number and mass concentrations were substantially reduced when using the upright system, although the total inhalable mass concentration remained above the TLV when welding through decking. The average diameters of the welding fume particles for both bare beam (31±17 nm) through deck conditions (34±34 nm) and the chemical composition of the particles indicated the presence of metallic nanoparticles. Stud welding exposes ironworkers to potentially high levels of biomechanical loading (primarily to the low back) and welding fume. The upright system used in this study improved exposure levels during stud welding simulations, but further development is needed before field deployment is possible.

Thermal property analysis and applications of GFRP panels to integral abutment bridges

Integral abutment bridges (IABs) have been designed and constructed during the last several decades in the United States and around the world. Many benefits can be expected from IABs, especially, the joints related water-leaking issues can be resolved. However, the integral bridges have not been widely applied in practices, which may be partly due to the lack of understanding on the thermal performances of IABs. For example, the commonly adopted concrete superstructure may limit the maximum length a jointless bridge can be designed, since concrete materials have relatively large thermal expansion coefficients but small tensile strength capacities. Regarding to this issue, glass fiber reinforced polymers (GFRPs) are considered as the substitute materials for IABs in this study, because GFRPs can be designed with comparatively small thermal expansion but large tensile strength. Therefore, in this paper, the thermal behaviors of IABs are firstly investigated through a numerical study on an as-built bridge, Caminada Bay Bridge, LA. Secondly, a homogenization modeling method is proposed to analyze GFRP panels under temperature loading effects. Finally, the thermal responses of an IAB are compared between two different deck conditions, i.e., GFRP panels and concrete slabs. Based on the investigation in this paper, the efficiency of the proposed homogenization modeling method for GFRP structures is discussed and the thermal benefits of applying GFRP panels to IABs are justified.

Application of Impact Resonance C-Scan Stack Images to Evaluate Bridge Deck Conditions

AbstractThis study presents a practical approach for imaging concrete pavement and bridge deck slabs for the presence of delamination defects. Air-coupled impact resonance (impact-echo) test data are presented as a fused image by using stacked spectral C-scans of the tested deck surface. The low frequency (<6 kHz) dynamic vibrational response of delamination defects, primarily caused by the behavior of flexural vibration modes, clearly and accurately reveals the presence of internal shallow delamination defects. Images are constructed with data from air-coupled impact resonance tests carried out on laboratory and field concrete deck samples and an in-service concrete bridge deck. The test data are arranged along surface x- and y-coordinates, with spectral amplitude represented by a coupled gray scale–opacity index. The image parameters are defined by data-driven rule-based criteria, with the presence of near-surface delamination defects indicated by shaded regions. The data manipulation and image constru...

Vehicle-Induced Vibration of Steel Deck Arch Bridges and Analytical Methodology

The purpose of this study is to investigate the dynamic behavior of steel deck-arch bridges with side-by-side multiple vehicle loadings moving over a rough deck. A brief description of analytical theory is provided, including vehicle model, bridge model, and numerical methods. Both vehicle and bridge are treated as three-dimensional models. The effectiveness of mode superposition and Newmark numerical methods are investigated. Most of the important factors that affect the dynamic response of bridges are considered in this study. The effects of the deck, column and arch boundary conditions are also studied, and the analytical impact factors of deck, column, and arch rib are compared with those determined on the basis of current American Association of State Highway and Transportation Officials (AASHTO) specifications. Study results are useful for both bridge engineers and bridge engineering researchers.

Nondestructive Detection of Delamination in Concrete Slabs

The delamination of concrete slabs is the separation along a plane roughly parallel to, and generally near, the surface. Corrosion-induced delamination is a common problem in old concrete bridge decks. If undetected, delaminations could expand, reach the surface, and result in spalling. Early detection of delamination is necessary for planning timely repairs that prevent costly deck replacement projects. Most bridge owners rely on routine visual and traditional surveys of bridge deck conditions. These surveys are highly subjective and can locate only large shallow delaminated zones. Several nondestructive testing (NDT) techniques have recently been employed for bridge deck evaluation to obtain more objective and comprehensive assessment. The reliability of applicable methods needs to be established before a greater role for NDT in routine inspections can be encouraged. This paper presents a validation study aimed at evaluating the effectiveness of three NDT techniques, namely impact echo, ultrasound (US) echo, and US linear array, in detection of delamination. This study is unique because the subject test specimens were deteriorated bridge deck segments preserved from the demolition of a prestressed box girder bridge. The results of the tests conducted on one of the specimens are presented and discussed here: impact echo provided satisfactory overall assessment, but the individual results were often difficult to interpret; US echo detected deep delaminations but not shallow ones; and US linear array located the extent of deep delaminations and provided indications of shallow ones.

Stochastic Response of Bridges Seismically Isolated by Friction Pendulum System

Stochastic response of bridges seismically isolated by the friction pendulum system (FPS) is investigated. The earthquake excitation is modeled by a nonstationary random process (i.e., uniformly modulated broadband excitation). The stochastic response of the isolated bridge is obtained using the time dependent equivalent linearization technique due to nonlinear force-deformation behavior of the FPS. The nonstationary response of the isolated bridge is compared with the corresponding stationary response in order to study the influence of nonstationary characteristics of earthquake excitation. An optimum value of the friction coefficient of FPS for which the root mean square absolute acceleration of the bridge deck attains a minimum value was observed. The influence of system parameters such as isolation period of the FPS, frequency content, and intensity of an earthquake on the optimum friction coefficient of FPS is investigated. It was observed that the above parameters have significant effects on the optimum friction coefficient of FPS. A closed form expression for the optimum friction coefficient of FPS and corresponding response of the isolated bridge system are proposed. These expressions were derived based on the model of the bridge with rigid deck and pier conditions subjected to stationary white-noise excitation. It was concluded that there is a good comparison between the proposed closed form expressions and actual optimum parameters and the response of the isolated bridge system. The maximum difference observed was about 10–15% percent and these expressions may be used for initial optimal design of the FPS for bridges.

Forecasting bridge deck conditions using fuzzy regression analysis

A good bridge management system requires an accurate and efficient bridge performance and prediction model. Ordinary regression models have been extensively used to forecast future infrastructure conditions. However, data on current bridge conditions obtained from inspectors are inherently subjective and non‐crisp; thus ordinary regression techniques are incapable of predicting future bridge performance when inspection data are not numerical. This paper presents a multiple fuzzy linear regression model for the estimation of bridge deterioration conditions. The proposed model can effectively tackle non‐crisp data and a mixture of fuzzy data and crisp data. An empirical case study using bridge inspection data from Taiwan is used to examine the variables contributing to deterioration of concrete decks. The results demonstrate the capability and effectiveness of the proposed model, which can assist bridge managers to better predict bridge deck performance.

Detection of Common Defects in Concrete Bridge Decks Using Nondestructive Evaluation Techniques

The transportation infrastructure in the United States is deteriorating and will require significant improvements. Consequently, innovations in the area of transportation infrastructure maintenance and rehabilitation are keys to the health and wellness of this valuable national asset. A major component of maintenance and rehabilitation is the ability to accurately assess the condition of the transportation infrastructure. This can be accomplished in part by using nondestructive evaluation techniques. Several nondestructive techniques have been used on concrete bridge decks and have proven to be efficient and effective. This paper aims at studying the different nondestructive evaluation techniques used in the assessment of concrete bridge deck conditions. An experimental investigation to evaluate the ability of infrared thermography, impact echo, and ground penetrating radar to detect common flaws in concrete bridge decks is developed and discussed. Results from this study showed the ability of these methods to detect defects with varying precision. Capabilities of the methods were verified and comparisons among the methods were made.

Integration of stochastic deterioration models with multicriteria decision theory for optimizing maintenance of bridge decks

This paper presents a new approach to optimizing the maintenance of concrete bridge decks. This approach combines a stochastic deterioration model and a multiobjective optimization model. The stochastic deterioration model is based on the first-order Markov chain, which predicts the probabilistic time variation of bridge deck conditions. The multiobjective optimization model takes into account two important and conflicting criteria: the minimization of maintenance costs and the maximization of the network condition. This approach achieves the best compromise between these competing criteria while considering the uncertainty in bridge deck deterioration. The feasibility and capability of the proposed approach are demonstrated with field data for a sample network of bridge decks obtained from the Ministère des Transports du Québec database. This example illustrates the effectiveness of the proposed approach in determining the optimal set of maintenance alternatives for reinforced concrete bridge decks when two or more relevant optimization criteria are taken into consideration.Key words: concrete bridge deck, maintenance management, multicriteria optimization, Markov chain, deterioration model.

Strength demands of line handlers on the Panama canal

Vessels transiting the Panama Canal are guided through the locks using locomotives attached by means of towlines (made of wire rope), which are fastened to bitts on the deck by line handlers. The latter activity requires high pulling strength demands and is thought to be a cause of the high incidence of low back disorders in these workers. At the invitation of the Panama Canal Commission, NIOSH researchers evaluated the strength demands of line handlers and the strength capabilities of a line handling crew. Strength demands measured during a transit indicated high pulling force demands for attaching ropes to the bow and stern bitts (&lt; 1000 N), but lower force requirements for midships bitts (&lt; 400 N). Tests of pulling strength capabilities of a line handling crew suggest that at least 4–5 line handlers are needed to perform the most demanding tasks. When pulling upwards or downwards on a rope in a team effort, ordering the crew according to stature appears important. Simulation of slippery deck conditions resulted in a 13% decrease in team pulling strength. Though the short duration of the study prevented an extensive evaluation, the data obtained provides insight into the design aspects of occupations where team-pulling activities are required.

Stress and Delayed Mortality Induced in Pacific Halibut by Exposure to Hooking, Net Towing, Elevated Seawater Temperature and Air: Implications for Management of Bycatch

The extent of stress and eventual mortality in Pacific halibut Hippoglossus stenolepis that resulted from simulated capture by hooking or towing in a net, followed by abrupt exposure to warmer seawater temperature and air, were determined under laboratory conditions. Abrupt exposure to 16°C seawater and air after either method of capture increased capture-induced stress, with accompanying mortality of 33% for hooked fish and 78% for fish towed in a net. Moreover, these deaths occurred as long as 30 d after experimental treatment, suggesting that delayed mortality should be considered in any study of Pacific halibut bycatch mortality. Stress induced by hooking or towing in a net followed by air exposure was reflected in cessation of negative phototaxis and feeding, both of which were resumed after 5 d with no mortality occurring. The results of this study clearly show that seasonal increases in temperature associated with thermoclines and deck conditions have the potential for markedly increasing the mortality of Pacific halibut that might otherwise survive capture and release in colder seasons. Strategies for effective management of Pacific halibut bycatch need to include consideration of seasonal temperature increases and how this factor might increase mortality.

Semiparametric Hazard Rate Models of Reinforced Concrete Bridge Deck Deterioration

The development of models to predict the distribution of times between changes in condition- state for reinforced concrete bridge decks is presented in this paper. The authors used semiparametric hazard rate modeling techniques to develop stochastic duration models for bridge decks in the Indiana Bridge Inventory database. The advantage of semiparametric methods is that they do not constrain the hazard rate to follow a prespecified probability density function. This approach is flexible enough to accommodate different types of deterioration processes, and can account properly for both censored and uncensored data. Furthermore, it relates observed deterioration to relevant explanatory variables. Finally, because this approach quantifies the time- dependent hazard rate function, it facilitates the computation of time-dependent transition probabilities for use in bridge management systems. The models presented in this paper are characterized by realistic trends. The estimated parameters are statistically significant and have, for the most part, intuitively correct signs. However, the models include only a small number of explanatory variables, and thus do not capture the entire array of relevant factors that contribute to bridge deck deterioration. This is especially true when they are compared to the state-based models obtained in earlier research using the same data. The reasons are that the deck conditions are observed at infrequent points in time (every 2 years) and that the window of observation is relatively short (10 years).

Risk reduction in diving spinal cord injury: Teaching safe diving skills

Thirty-four recreational swimmers underwent an intervention program to improve diving skills. Participants with low diving skills completed seven 10-minute sessions which emphasised locking thumbs and holding arms extended beyond the head, and steering and gliding skills. Various dive entries were video-recorded and maximum depth reached was used as the criterion measure. A one-way repeated measures analysis of variance was conducted for each dive condition. Maximum depth decreased for all dives. Velocity at maximum depth was greater for the Treadwater, Deck and Block conditions. Improved streamlining and increased 'spring' were evident in more confident participants. Hands separated in 71% of pre-intervention dives but only in 3% of post-intervention dives. Preintervention, arms were pulled backward before. or at, maximum depth in 30% of participants but none did this post-intervention. Diving skills were improved following participation in the intervention program.

Statistical analysis on long-term measurement of wave induced load of naval ships

This report is concerned with statistical analysis on long-term measurement of wave induced load of naval ships. We have analyzed wave-induced vertical bending stresses at midship deck and wave conditions measured by 12 naval ships which are equipped with Ship Motion Analyzing Computer System (SMACS) over a period of 84 years. We have introduced contribution rates between wave period and wave height on long term distribution of wave induced vertical bending stress in each stress revels and contribution rates between wave period and heading angle between ship and wave direction on the long term distribution. We derive the following conclusions.(1) When the range of the probability of exceedance in the long term distribution are from 10-1 to 10-2, the contribution rates between wave period and wave height and the rates between wave period and heading angle widely distribute over the wave conditions and heading angles.(2) For the range of the probability of exceedance from 10-4 to 10-8, the contribution rate is centered at a wave condition and a heading angle. The condition equals to the broad sense of resonance when the peaks of both the response amplitude function of the wave bending stress in regular wave and wave spectra are superimposed.

Principles of Thermography and Radar for Bridge Deck Assessment

Traditional methods of bridge deck condition assessment are slow, labor‐intensive, intrusive to traffic, and unreliable. Two new technologies, radar and infrared thermography, which have recently been introduced, show promise for producing rapid and accurate condition assessment for bridge decks. These technologies are being applied without the benefit of a firm physical understanding of their inherent capabilities and limitations. This paper discusses the physical principles upon which these techniques are based, and proposes simple physical models for the prediction of radar and infrared response to various bridge deck conditions. Parameter studies are carried out using these models to predict the radar and infrared response to moisture, chloride, delamination, and deck geometry. The model study results show the range of sensitivity and the inherent limitations of these two techniques. These results have led to the suggestion of a predictive technique that has been used in field studies of repaired and ...