Innovative orthotropic deck strengthening design for the Suurhoff lifting bridge

Hydrocarbon fire accidents in offshore deck structures are of serious concern due to the confined environment of offshore oil drilling and production platforms, which limits the escape routes. One of the major structural components that are highly affected during fire accidents is the deck plates. The deck plates are usually designed as stiffened plates with high strength steel. The increase in temperature during fire changes the mechanical properties of steel significantly, which may result in strength and geometric instability of the structure. The present study aims to investigate the behavior of a stiffened steel deck plate under different hydrocarbon fire scenarios using sequential thermal and structural analyses using Ansys. The stress distribution and deformation of the plate in time scale are presented, discussing the highly affected region concerning the source of the fire. The fire rating for the steel deck under hydrocarbon fire is also suggested for different fire scenarios considered in the study. It was observed that the deformation of the deck plate varies to the area of deck plate in direct contact with fire, boundary conditions of the plate, and the area of steel plate with elevated temperature beyond which the mechanical properties of steel are highly affected. Also, the numerical investigations of the deck plate under the combined action of mechanical load and hydrocarbon fire had shown an increased deformation in the deck plates, which in turn reduces the fire rating of the plate under all fire scenarios. The effect of creep strain at high temperature on the response of the steel deck plate is also studied for the different fire loading cases.

Fatigue resistance of rib-to-bimetallic steel deck welded joints in orthotropic steel bridge decks

Under heavy traffic conditions, some fatigue cracks have been found at welding joints between U-shaped ribs “trough ribs” and deck plates. Fatigue cracks along thickness direction of deck plate from root tip are important because visual crack detection from outside is limited. In this paper, new functional steel plates with initiation resistance of fatigue crack at weldment and propagation resistance at base material are applied to deck plate to evaluate improvement of fatigue life. We conducted fixed-point fatigue tests with real scale partial models consisted with one trough rib and a transverse girder, and the elastic FEM (Finite Element Method) analysis corresponding to the fatigue test specimen. Based on these results, we studied the fatigue properties which focused on the difference between conventional steel plates and newly developed steel plates, FCA (Fatigue Crack Arrester). Fatigue cracks were initiated from root tip of welded joints between a trough rib and a deck plate. It is clarified that FCA steel plates instead of conventional steel plates can improve the fatigue life under the same welding conditions. This improvement effect becomes much clearer in the high cycle region, which is noticeable at the operation and management stage of bridges.

<p>Fatigue damage is a major topic in bridge maintenance. The fatigue damage to steel bridge deck has been dramatically increasing since the first fatigue damage was observed in Hanshin expressway in early 2000s. Insufficient knowledge of bridge fatigue design and unexpected increase of traffic demand and heavy vehicle could be the cause of the fatigue damage.</p><p>Replacement of base pavement course to steel fiber reinforced concrete (SFRC) has been generally used for strengthening of steel decks; however, the countermeasure from the topside of the bridge deck could make serious traffic disruption. Therefore, reactive and proactive maintenance for such steel decks has not been well progressed so far.</p><p>According to the background above, Hanshin expressway has been making an effort on developing new method by strengthening steel deck from the bottom side. The idea of the new method is to enhance fatigue resistance by improving the weld joint between deck plate and U-rib plate. Three potential methods were identified and the effectiveness of those methods was studied in field for making sure of not only fatigue resistance improvement but also field construction.</p><p>This paper will introduce the new retrofit methods for steel deck and describe the effectiveness of those methods.</p>

If the serviceability of an existing shield tunnel structure is endangered, strengthening is required. A newly proposed technique of strengthening of segmental tunnel linings, called steel plate – concrete composite structure (SPCCS) strengthening, was experimentally investigated in previous research, in which the tunnel lining was strengthened at the ultimate state. Such a strengthening scheme is denoted as delayed strengthening. Experimental results have shown that the new strengthening technique is advantageous in enhancing the design life of shield tunnels, as compared to traditional strengthening techniques. However, in engineering practice, the tunnel lining must be strengthened before the ultimate state is reached. Hence, the timing of strengthening is a critical parameter in the design of the strengthening process. In the present research, a full-scale test was conducted such that the segmental tunnel lining was strengthened ab initio, i.e. before being subjected to external loading. This mode of strengthening is termed as initial strengthening scheme. The ultimate capacity, the failure process, and the failure mode were investigated. The failure mechanism, the ultimate capacity, the ductility, and the toughness of segmental tunnel linings, reinforced by the SPCCS strengthening technique, were compared with the ones of initial and delayed strengthening schemes. It is shown that the timing of strengthening does not have much influence on the ultimate capacity. However, it has a significant influence on the stiffness, the ductility, and the toughness. The ultimate load bearing capacity of the strengthened structure in case of initial strengthening was found to be only 5.7 % larger than the one in case of delayed strengthening, whereas the increase of the structural stiffness, the ductility, and the toughness is 520.6 %, 46.1 %, and 64.6 %, respectively. Regarding the utilization efficiency of the steel plate, the results have shown that the earlier the structure is strengthened, the greater the utilization efficiency of the strengthening material.

<p>Aiming to resolve two main distresses of traditional orthotropic steel bridge deck such as the welding fatigue crack and the premature damage of pavement, this paper proposes a new kind of orthotropic steel bridge deck based on corrugated steel plate. The fundamental elements of this new deck include a steel plate in the upper layer, a corrugated steel plate in the middle layer which give a role of U-type rib in the traditional bridge deck, and a steel plate in the lower layer. Besides the fundamental structure of steel deck, a thin layer of reactive power concrete (named as RPC) is conceived to be paved on the steel deck. This paper mainly analyzes the mechanical properties of this new deck such as the transverse load transfer path and the hot spot stress, the mechanical properties comparison is also completed between this new orthotropic steel deck and the traditional one. The research shows that the mechanical properties of global deformation and local stress for the new orthotropic steel deck are much advanced than the traditional one.</p>

The major cause of failure of pavements on orthotropic steel bridge decks has been fatigue cracking of the pavement over the points of attachment of the webs of the longitudinal stiffeners to the steel deck plate. Accelerated constant load fatigue tests on composite (deck plate and pavement) flexural fatigue beams have been used to compare pavement systems and to predict service life. However, accelerating the tests to provide useful information in a reasonable time frame requires that the load frequency or load level, or both, be substantially increased beyond service conditions. If the load is increased too much, permanent distortion of the specimen may result, thus making the test no longer a fatigue test. Increasing load frequency too much may overheat the test specimen. Since pavement stiffness decreases as its temperature increases the temperature increase reduces the stresses that cause the fatigue cracks. This paper discuses these potential problems and presents test results to help define the limitations of accelerated fatigue tests for orthotropic steel deck pavements.

In this study, an analytical procedure for the evaluation of the expected performance of existing reinforced concrete (RC) beam-column joints before and after being retrofitted using fiber-reinforced polymer (FRP) composite materials is presented. Focus is given on the evaluation of the shear-strength versus deformation properties of the panel zone region either in the as-built or FRP-retrofitted configuration. Based on experimental and numerical evidence as well as on physical models representing the mechanics of the joint region, principal tensile stresses versus joint shear deformation relationships are adopted and preferred to more traditional nominal shear-strength rules, to evaluate, within a step-by-step iterative procedure, the combination of the joint shear contribution provided by the FRP composite material and that provided by the concrete core alone. The use of principal stresses allows one to directly account for the effects of variation of axial load, typically neglected in the assessment and retrofit of beam-column joints. The hierarchy of strength and sequence of events (damage mechanisms) expected within a beam-column subsystem are visualized via M-N interaction performance domains, used as a basis for a performance-based retrofit philosophy. Specific limit states or design objectives are targeted, with attention given to both strength and deformation limits. The proposed analytical procedure is validated on the results of a set of experimental tests available in the literature. With the intention to provide a simple design tool that can be easily implemented by practicing engineers, a worked example for the evaluation of the expected performance of an FRP retrofitted beam-column joint is provided and used as a basis for a parametric study to illustrate the effects of different strengthening schemes on the behavior of strengthened exterior joint panels under various axial load levels.

Use of UHPFRC overlay to reduce stresses in orthotropic steel decks

The orthotropic steel deck is a welded structure consisting of a flat and thin steel plate stiffened by a series of longitudinal ribs with support by orthogonal crossbeams. Since its development in 1950’s, the orthotropic steel deck system has been utilised all over the world. Over the last few decades, many reports have been published concerning fatigue cracking in orthotropic steel decks resulting from the complicated welded details and minimised plate thickness to reduce weight. In Japan, more than 2,300 orthotropic steel deck bridges have been constructed so far and fatigue cracking in orthotropic steel decks has been observed mainly in heavily trafficked urban expressways. In 1980’s and 1990’s, fatigue cracking at the rib-to-crossbeam connection and the welded rib splice was a major issue, while during the last 15 years, fatigue cracking at the rib-to-deck welded joint has been increasingly observed where trapezoidal ribs are used. The objective of this paper is to present a novel inspection method using phased array ultrasonic testing for rib-to-deck welded joints of orthotropic steel decks. Phased array ultrasonic testing has been used for medical diagnosis for more than forty years. Meanwhile, application of the phased array ultrasonic testing to industries wasn’t so popular until 1990’s, and then the rapid technology development encouraged the use of phased array ultrasonic testing in the industrial field. A phased array ultrasonic probe consists of multiple transducer elements each of which can act as a single ultrasonic transducer. The transducer elements are arranged in various patterns where individual and independent driving of an element must be attainable without inducing vibration in nearby elements and the performance of each element must be as close as possible for the formation of a homogeneous beam. Due to the ability to control the acoustic characteristic of ultrasonic beams, phased array ultrasonic systems can achieve the electronic scanning techniques that are not made possible by using conventional ultrasonic systems. Three main advantages of phased array ultrasonic testing over conventional ultrasonic testing are increased inspection sensitivity, increased inspection coverage and decreased inspection time. Fatigue cracks initiated at the rib-to-deck weld root can grow into either the deck plate or the weld bead. Therefore, in order to detect fatigue cracks at the rib-to-welded joint as internal part-through cracks at the early stage of development, both the deck plate and the weld bead are necessary to be examined. In view of this, an electrically driven scanner holding twin phased array ultrasonic probes is developed, allowing us to perform simultaneous examination of the deck plate and the weld bead (Fig. 1). The developed scanner is applied to the orthotropic steel deck of the Meiko-Chuo Bridge, a three-span steel cable-stayed bridge and the ability to detect internal part-through cracks in the weld bead is verified. Figure 1 Electrically driven scanner holding twin phased array ultrasonic probes (a) general view drawing and (b) schematic of twin probes fixed to the deck plate and the rib wall. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig29_1.tif/>

A large number of highway bridges have been constructed in China since 1980s. Most of the aging bridges are in need of strengthening, which will lead to consuming big amounts of material and energy resources, producing air emissions and solid waste. This paper made a life cycle assessment for a highway bridge with four different strengthening plans by using Eco-indicator 99 to figure a total environmental impact score of the bridge. Based on analyzing the life cycle assessment (LCA) investigations of bridges, the adopted LCA method for the highway bridge tracks materials and energy resources through the various stages of the bridge life cycle including production, transportation, construction, strengthening, and demolition, considering the impact of vehicle detours during strengthening construction, to calculate environmental impact for ecosystem quality, human health, energy, and resources. This is done for four strengthening schemes, which are traditionally compared based only on the basis of economic cost. In order to account for the variability of critical input variables, a Monte Carlo simulation was performed to estimate the variability of environmental scores associated with the transportation distance, the average fuel consumption for each vehicle, detouring distance, the structure closure period, and maintenance times. Ten thousand iterations were conducted based on previous studies. The analysis shows that the maintenance phase alone contributes about 66 % of the total environmental impact (including detouring stage 50 %, repaving bridge deck 12 %, strengthening 4 %), followed by material production stage (approximately 40 %). Of the four strengthening plans, plan 1 and plan 3 have relatively greater contributions in terms of environmental damage while the cost budgets are much lower. On the contrary, plan 2 and plan 4 have lower environmental burdens but cost much more. Sensitivity analysis shows that the damage to resources and ecosystem quality are more sensitive to the variation of parameters. A life cycle assessment for a highway bridge in China with four different strengthening plans is conducted by using Eco-indicator 99 to figure a total environmental impact score of the bridge. It determines that the maintenance phase contributes the most to the environment deterioration. This study also shows that the energy consumptions and pollutant emissions related to traffic disruption during maintenance operations should not be excluded. Regarding the strengthening plans, it can be concluded that the environmental impact of bonding carbon fiber-reinforced polymer is fewer than that of bonding steel plates.

The high-performance topping concrete overlay would significantly reduce the fatigue stresses at susceptible details of orthotropic steel deck (OSD) and effectively improve the fatigue performance. Full-scale fatigue tests and numerical simulations were carried out to quantify the effects of steel fiber reinforced concrete (SFRC) topping pavement in reducing the OSD fatigue stresses based on a practical bridge design. Fatigue stress of the OSD critical details was measured from tests and cracking was observed in the SFRC overlay. Both an innovative pre-pump-pulse Brillouin optical time domain analysis (PPP-BOTDA) distributed optical fiber sensor and strain gauges were also used to measure the stress at OSD fatigue-prone details, including the crossbeam cut-out, rib-to-deck weld, rib-to-crossbeam weld and splice of U-rib. The corresponding three-dimensional (3-D) finite element model was then established and verified by the test results, and used to conduct a parametric study to obtain a quantitative expression of fatigue stress reduction factor, in terms of relative elastic modulus and thickness of overlay and steel deck plate. The proposed quantitative model of the fatigue stress reduction effect can guide the cost-effective design of composite bridge deck.

In order to solve the problems of the pavement delamination or slip caused by the failures of waterproof adhesive layer or anti-corrosion coating, the epoxy zinc-rich paint, the epoxy clear water paint and epoxy asphalt adhesive material with good performance was selected for the roughness-adhesive force test, tensile test under different temperatures and corrosion resistance test. The optimal anti-corrosion layer and adhesive layer were selected to increase the service life of the steel deck pavement. The test results show that: When the steel roughness is 60μm, the anti-corrosion material has the highest adhesive strength with the steel plate. Both the epoxy zinc-rich paint and the epoxy water paint have high adhesive strengths with the steel plate at room temperature. But at low temperature, the adhesion performance of the epoxy water paint is significantly better than that of the epoxy zinc-rich paint. At 70 °C, the adhesive strengths of both the epoxy water paint and epoxy zinc-rich paint adhesive system greatly decrease. The destruction morphology shows the opening of the adhesive layer. The specialized anti-corrosion coating must be brushed on the steel deck.

Stress analyses and fatigue evaluation of rib-to-deck joints in steel orthotropic decks

Welding residual stress in roots between deck plate and U-rib in orthotropic steel decks