Steel Segments Research Articles

16.13: Queensferry crossing cable‐stayed composite bridge

ABSTRACTThe Queensferry Crossing near Edinburgh is a road bridge which is constructed as a composite cable‐stayed bridge with two main spans of 650 m and two approach bridges. The main bridge has a width of 40 m and has two skew cable planes with spacing of 16.4 m. The composite deck comprises a single open steel box with a concrete slab on the top.The bridge is designed in accordance with the Eurocodes design standards. The general design approach for the steel deck is based on the Reduced Stress Method in accordance with Eurocode 3 together with finite element (FE) shell method calculations for individual plates and for whole plate panels. The FE shell methods are in accordance with [7] Annex C model 5, which means that the calculation is based on nonlinear material properties and non‐linear geometric behaviour and finally includes plate imperfections.The typical steel deck box is stiffened with longitudinal trough stiffeners and cross bracing frames at a spacing of 4.05 m. Special details are made around the three Towers and the Transition zone between the single steel box in the cable‐stayed span and separated twin boxes on the approach viaducts.The steel structure for the cable‐stayed bridge was fabricated in China and steel segments with a length of 16.2 m were transported to Scotland, where the concrete deck was cast. Afterwards the segments were transported by sea to the bridge site, lifted to their final position and the two segment cables were installed and anchored to the deck and the towers.The Queensferry Crossing is the UK's tallest bridge and has been recognised in the 2016 Guinness World Records for the world's largest freestanding balanced cantilever. The north and south approach bridges were launched with a maximum cantilever span of 104 m.

16.26: Design and construction of composite bridges

ABSTRACTComposite bridges, where steel girders are used compositely with a concrete deck slab, can be preferred over steel or concrete bridges due several reasons. They are less expensive and require less maintenance than orthotropic steel decks and they are lighter than concrete girders. They often require less temporary structures for execution and by using prefabricated elements fast erection can be achieved. Composite bridges are often chosen for span ranges that are in between the typical span ranges of concrete and steel bridges.When designing a composite bridge deck it is important to carefully consider the different material characteristics of steel and concrete to achieve an optimum design both in respect of erection sequence and material quantities. The concrete slab has a high resistance to compression forces whereas steel is prone to buckling, but has a high tension capacity.The Constantine ramp bridges (Algeria, 2014) are open steel box girders with a filigran concrete slab. They are located on steep slopes in a congested urban area, which gave limitations to the construction methods. A composite deck solution was chosen so that steel segments could first be lifted into place by a medium size crane and secondly prefabricated concrete slab filigran members could be placed on the steel and used as formwork for the final in situ casting of the concrete slab. The construction sequence was planned so that the concrete slab would be mainly in compression in the dead load situation to optimize material quantities.Composite bridge decks are often applied in cable stayed bridges, since the concrete slab has good abilities to resist the high compression induced by the inclined cable stays particularly near the towers. Examples of recent composite cable stay bridges are Busan Bridges (Korea 2014, main span 475 m) and New NY Bridge (New York, under construction, main span 366 m) where bolted wide flange steel girders were used in combination with a concrete slab and Sungai Johor Bridge (Malaysia 2013, main span 500 m) where an open box section was applied.Composite bridge decks are often used in combination with all steel or all concrete decks to balance the weight when for example the main span is very large compared to the back spans such as for the Stonecutters bridge (Hong Kong, 2009, Main Span 1018m).

Wavelet energy ratio index for health monitoring of hysteretic dampers

This paper presents new contributions to evaluate the damage suffered on a particular type of hysteretic damper called web plastifying damper (WPD) for the passive control of structures subjected to earthquakes. WPDs consist of several I-section steel segments arranged to form a brace-type structural element. Energy input by the earthquake is dissipated by the WPD through plastic deformations of the web of the I-sections. These devices, properly installed in reinforced concrete test models, were tested under successive seismic simulations of increasing magnitude with a shaking table. To assess the damage of the web of the I-section after each seismic simulation, a new damage index called wavelet energy ratio (WER) was developed; it uses the signals collected by piezoelectric sensors in simple vibration tests. The index is based on wavelet package decomposition and energy calculation of properly chosen wavelet coefficients. It was correlated with a mechanical energy-based damage index—ID—proposed in past research, which has proven to accurately characterize the level of damage yet requires costly instrumentation to acquire the load–displacement curve needed for its computation. The experiments reported in this paper demonstrate a good correlation between WER and ID indices in a realistic seismic loading scenario. On the basis of this correlation, it is possible to estimate ID indirectly from the WER, which involves much simpler and less expensive instrumentation, easily applicable for in situ continuous monitoring of the dampers.

Structural Analysis of a Cantilever Beam with Tapered Web Section through Fea

This paper examines the twisting anxieties of steel web decreased I segment cantilevers. Cantilevers with different level of decrease web broke down. The anxiety design along an I segment is recognized and the area and extent of the most extreme bending anxiety are talked about. The basic activity of a customary web decrease I segment under immediate or offbeat stacking is prevalently twisting, with different impacts, for example, distorting, pivot and parallel torsional clasping. The web decreased steel segment cantilever shaft is a broadly utilized auxiliary component as a part of numerous fields of use in light of its various great properties. FEA study on the conduct of steel I-segment (200 mm × 100 mm and 5 m length with a vertical heap of 500 kg) with straight web under stacking is displayed in this course. The examination is made with I segment having same dimensioned level web. The study incorporates bending execution, sidelong torsional clasping. It is presumed that steel bar with decreased web segment has higher imperviousness to twisting, sidelong torsional clasping contrasted with that of an area with level web segment cantilever bar. The point of turn is likewise diminished with increment in decreased proportion. 3:2 decrease proportions are reasonable as the proportionate anxiety is less for this proportion.

Experimental and analytical investigation on bond-slip behaviour of deformed bars embedded in engineered cementitious composites

This paper investigates the bond-slip behaviour of steel reinforcement embedded in engineered cementitious composites (ECC), a ductile concrete exhibiting tensile strain hardening performance. Two series of experimental tests were carried out on short and long reinforcement subject to pull-out actions. The maximum bond stress that embedded steel reinforcement could sustain was quantified through pull-out tests on short rebars. Experimental results of short reinforcement suggested that ECC significantly increased the maximum bond stress of steel reinforcement. For long reinforcement, special attention was paid to the bond stress of steel segments at post-yield stage. Bond stress profiles were determined in accordance with attached strain gauge measurements along the steel bars. Besides, the effect of localised necking beyond ultimate strength on the force-slip relationships of reinforcement was studied. Thereafter, an analytical model was proposed based on experimental results to predict the force-slip relationship of long reinforcement either anchored in concrete or in ECC. Reasonably good agreement was achieved between experimental and analytical force-slip curves. Finally, parametric studies were conducted to quantify the required embedment length of steel reinforcement in ECC.

A Comparison of Cone-beam Computed Tomography with Periapical Radiography in the Detection of Separated Instruments Retained in the Apical Third of Root Canal–filled Teeth

IntroductionThis study compared the diagnostic efficacies of cone-beam computed tomographic (CBCT) imaging and periapical radiography (PR) in the detection of retained separated instruments located at the apical third of filled root canals. MethodsSixty single-rooted extracted human teeth were instrumented to size #25 and were randomly divided to a simulated 2-mm #30 K-file (stainless steel or nickel-titanium) segment separation at the apical third of the canal (n = 40) or a control group without a separated instrument (n = 20). The canals were obturated to the separated instrument or the working length for the teeth without an instrument using gutta-percha with AH26 (Dentsply DeTrey GmbH, Konstanz, Germany) or Roth sealer (Roth International Ltd, Chicago, IL). The teeth were invested in a mandible model simulating the bone density and imaged using CBCT imaging and PR. The images were evaluated separately by 2 calibrated observers twice with an interval of 4 weeks. Cohen kappa was used to evaluate the observer agreement. Receiver operating characteristic curve analysis was used to evaluate the discrimination ability. ResultsThe intraobserver kappa was 0.744 and 0.627, and between the observers, it was 0.593 and 0.275 for PR and CBCT imaging, respectively. Using PR, the mean sensitivity was 71.25%, and the specificity was 93.75%. Using CBCT imaging, the sensitivity and specificity were 41.25% and 71.25%, respectively. Although for PR the area under the curve values ranged between 0.75 and 0.91 (P < .05), for CBCT they ranged between 0.48 and 0.60 (P > .05), regardless of the instrument or the sealer type. ConclusionsPR performed better than CBCT imaging for the detection of retained separated instruments located at the apical third of extracted human root canal–filled teeth.

Vision-based technique for bolt-loosening detection in wind turbine tower

In this study, a novel vision-based bolt-loosening monitoring technique is proposed for bolted joints connecting tubular steel segments of the wind turbine tower (WTT) structure. Firstly, a bolt-loosening detection algorithm based on image processing techniques is developed. The algorithm consists of five steps: image acquisition, segmentation of each nut, line detection of each nut, nut angle estimation, and bolt-loosening detection. Secondly, experimental tests are conducted on a lab-scale bolted joint model under various bolt-loosening scenarios. The bolted joint model, which is consisted of a ring flange and 32 sets of bolt and nut, is used for simulating the real bolted joint connecting steel tower segments in the WTT. Finally, the feasibility of the proposed vision-based technique is evaluated by bolt-loosening monitoring in the lab-scale bolted joint model.

Integrated Multispeed Magnetic Gears: A Novel Approach to Design of Magnetic Transmission Systems

In this paper, a novel approach for the design of magnetic gears is proposed to provide various gear ratios per unit in a magnetic gear system, including a stator, a rotor, and steel segments. This design utilizes rod-shaped permanent magnets in the stator complex instead of arc-shaped permanent magnets used in ordinary magnetic gear systems. Interestingly, the number of pole pairs on a stator is varied only by rotating the rod-shaped magnets. The number of pole pairs on the rotor is kept constant. Therefore, the gear ratio is changed as a function of varying the number of pole pairs on stator. During changing the gear ratio, the number of the steel segments is changed with a specially designed configuration to maintain the maximum efficiency for the system. The concept and working principles of the proposed approach are presented. Simulation studies are employed to validate the performance of the system.

Health monitoring of a new hysteretic damper subjected to earthquakes on a shaking table

This paper presents the experimental results obtained by applying frequency-domain structural health monitoring techniques to assess the damage suffered on a special type of damper called Web Plastifying Damper (WPD). The WPD is a hysteretic type energy dissipator recently developed for the passive control of structures subjected to earthquakes. It consists of several I-section steel segments connected in parallel. The energy is dissipated through plastic deformations of the web of the I-sections, which constitute the dissipative parts of the damper. WPDs were subjected to successive histories of dynamically-imposed cyclic deformations of increasing magnitude with the shaking table of the University of Granada. To assess the damage to the web of the I-section steel segments after each history of loading, a new damage index called Area Index of Damage (AID) was obtained from simple vibration tests. The vibration signals were acquired by means of piezoelectric sensors attached on the I-sections, and non-parametric statistical methods were applied to calculate AID in terms of changes in frequency response functions. The damage index AID was correlated with another energy-based damage index-ID- which past research has proven to accurately characterize the level of mechanical damage. The ID is rooted in the decomposition of the load-displacement curve experienced by the damper into the so-called skeleton and Bauschinger parts. ID predicts the level of damage and the proximity to failure of the damper accurately, but it requires costly instrumentation. The experiments reported in this paper demonstrate a good correlation between AID and ID in a realistic seismic loading scenario consisting of dynamically applied arbitrary cyclic loads. Based on this correlation, it is possible to estimate ID indirectly from the AID, which calls for much simpler and less expensive instrumentation.

Piezoelectric sensing and non-parametric statistical signal processing for health monitoring of hysteretic dampers used in seismic-resistant structures

The paper proposes a new application of non-parametric statistical processing of signals recorded from vibration tests for damage detection and evaluation on I-section steel segments. The steel segments investigated constitute the energy dissipating part of a new type of hysteretic damper that is used for passive control of buildings and civil engineering structures subjected to earthquake-type dynamic loadings. Two I-section steel segments with different levels of damage were instrumented with piezoceramic sensors and subjected to controlled white noise random vibrations. The signals recorded during the tests were processed using two non-parametric methods (the power spectral density method and the frequency response function method) that had never previously been applied to hysteretic dampers. The appropriateness of these methods for quantifying the level of damage on the I-shape steel segments is validated experimentally. Based on the results of the random vibrations, the paper proposes a new index that predicts the level of damage and the proximity of failure of the hysteretic damper.

Experimental and analytical study on stiffened steel segment of hybrid structure

Hybrid structures which innovatively and reasonably combine two different materials in longitudinal direction have been applied world-widely, such as hybrid girder, hybrid pylon and hybrid arch skewback. The hybrid structure segment generally consists of steel stiffened segment, concrete strengthened segment and hybrid joint. In order to investigate ultimate capacity and buckling mode of steel stiffened segment in hybrid structure, model tests on five different specimens have been carried out. The test results indicated that embedded T-reinforcing stiffeners had the best axial stiffness, while the out-plane stiffness, ultimate capacity and local stress concentration of circumscribed π-reinforcing stiffeners were best among the three traditional reinforcing stiffeners. Besides, the methods of extending reinforcing stiffener web and adding diaphragms on the end of reinforcing stiffeners not only obviously improved both axial and out-plane stiffness but also increased ultimate capacity and reduced local stress concentration. Five three-dimensional finite element (FE) models of steel stiffened segments considering initial imperfections and residual stress were established. Theoretical analysis based on the principle of stationary potential energy was carried out. The reduced parameters based on FE analysis results were consistent with those from tests and theoretical analysis and tended to be conservative at a safety level. The presented overall investigation may provide reference for the design and construction of stiffened steel segment in hybrid structure.

Comparative life cycle assessment of tubular wind towers and foundations – Part 2: Life cycle analysis

In the first part of the paper the design of tubular towers and respective onshore foundations was addressed. The considered solutions were based on steel, concrete and hybrid steel-concrete tubular towers supporting multi-megawatt turbines of 2, 3.6 and 5MW power with hub heights of 80, 100 and 150m respectively. In this second part of the paper, the life cycle analysis of the designed case studies is performed and conclusions about their environmental impact are drawn. Two different scenarios concerning the lifetime of the towers were established. The first scenario considers 20years lifetime and two different construction methods for the connection of the steel segments, the first based in current technology using flange connections and the second using newly developed friction connections. Assuming equal importance for all environmental categories in this scenario, it may be concluded that for heights up to 100m hybrid towers with friction connections are the most efficient solution. For higher heights, the concrete tower becomes more efficient. The second scenario considers an increased total lifetime of 40years, assuming the reuse of the tower after 20years of operation. In this case, the use of friction connections in steel towers enhances the possibility of dismantling and reusing the tower potentiating much better performance in relation to the environmental category of global warming.

Health monitoring of web plastifying dampers subjected to cyclic loading through vibration tests

This article investigates experimentally the application of health monitoring techniques to assess the damage on a particular kind of hysteretic (metallic) damper called web plastifying dampers, which are subjected to cyclic loading. In general terms, hysteretic dampers are increasingly used as passive control systems in advanced earthquake-resistant structures. Nonparametric statistical processing of the signals obtained from simple vibration tests of the web plastifying damper is used here to propose an area index damage. This area index damage is compared with an alternative energy-based index of damage proposed in past research that is based on the decomposition of the load–displacement curve experienced by the damper. Index of damage has been proven to accurately predict the level of damage and the proximity to failure of web plastifying damper, but obtaining the load–displacement curve for its direct calculation requires the use of costly instrumentation. For this reason, the aim of this study is to estimate index of damage indirectly from simple vibration tests, calling for much simpler and cheaper instrumentation, through an auxiliary index called area index damage. Web plastifying damper is a particular type of hysteretic damper that uses the out-of-plane plastic deformation of the web of I-section steel segments as a source of energy dissipation. Four I-section steel segments with similar geometry were subjected to the same pattern of cyclic loading, and the damage was evaluated with the index of damage and area index damage indexes at several stages of the loading process. A good correlation was found between area index damage and index of damage. Based on this correlation, simple formulae are proposed to estimate index of damage from the area index damage.

Seismic analysis and evaluation of several recentering braced frame structures

After earthquakes, residual inter-story drifts greater than 0.5% in buildings may indicate a complete loss of the structure from an economic point of view. Recently, research efforts have been extended to the utilization of superelastic shape memory alloy materials for the smart control systems that can automatically reduce the plastic deformation of the structure subjected to strong seismic loading. Superelastic shape memory alloys are unique metallic alloys that undergo substantial inelastic deformations and regain their original conditions when applied loads are removed, thus alleviating the problem of permanent deformation. The frame structures make the best use of such shape memory alloy’s recentering capability if the superelastic shape memory alloy segments used to replace the steel segments are installed at the part where large deformation is likely to occur. The primary focus of this study is on the seismic response of special steel concentrically braced frames and buckling-restrained braced frames, utilizing superelastic shape memory alloy braces. In order to examine the comparative residual inter-story drift response of both braced frames, 3- and 6-story buildings were designed in accordance with current code specifications, and then nonlinear time-history analyses for two seismic hazard levels were conducted on 2D analytical frame models. The braced frames with superelastic shape memory alloy bracing systems were also compared to those with conventional steel bracing systems. Overall, analysis results show that the superelastic shape memory alloy bracing systems are more effective in decreasing residual inter-story drifts than the conventional steel bracing systems.

Stonecutters Bridge, Hong Kong: main span erection

To erect a main span of a bridge across the entrance of one of the busiest container ports in the world without causing disruption is a complex operation. Stonecutters Bridge, Hong Kong, was also the second longest cable-stayed span in the world with a unique twin box deck design that was being erected through a typhoon season. Extensive preparation works were carried out from wind tunnel tests in the UK, marine simulations, new erection procedures, typhoon studies and continuous erection analysis. The main span consisted of 53 steel segments weighing between 500 and 600 t and lifted from a purpose-built self-propelled barge. The closure of the main span posed special problems with the large deflection and expansion from a 500 m cantilever, and that the closure segment was in two pieces erected at the same time. The 224 parallel wire strand stay cables were some of the longest and heaviest cables ever erected.

New strategy of substructure method to model long-span hybrid cable-stayed bridges under vehicle-induced vibration

Hybrid cable-stayed bridges consist of steel and concrete bridge segments, of which steel–concrete joints are of great importance and raise strong research interest. Due to the limitation of the traditional methods, i.e., the member finite element (FE) method and Mixed Dimensional Coupling (MDC) method, the present study proposes a substructure method to model long span bridges. The current application of the substructure method is to extract some specific parts of the whole structure to refine and analyze them. Different from the routine substructure approach, here the entire structure is modeled in detail and divided into many substructures. All the substructures are then condensed into super-elements except the concerned part. The application of the method is then illustrated through numerical studies of the vehicle–bridge coupling vibration of the Jingyue Yangtze River Bridge with a main span of 816 m. The entire bridge is first divided into many substructures with a reasonable length. Among them, the concerned substructure with 23.8 m in length including the steel–concrete joint is modeled in detail but not formed into super-element, while all the other components are modeled in detail and formed into super-elements using the component mode synthesis (CMS) method. All the components including both the super-elements and non-super-elements are then assembled into a complete and fine full bridge model. Finally, the model is used for the vehicle-induced dynamic analysis under deterministic traffic flows. The results show that the joint works well, and the transition between the steel girders and concrete beams is very smooth.

Study on Local Buckling at Main Girder of Steel Segment in Great Depth Shield Tunnel

Study on Local Buckling at Main Girder of Steel Segment in Great Depth Shield Tunnel

Study on Local Buckling at Main Girder of Steel Segment

Study on Local Buckling at Main Girder of Steel Segment

Experimental study on joint of spliced steel–PSC hybrid girder, part II: Full-scale test of spliced hybrid I-girder

A full-scale test is conducted on a spliced steel–PSC (prestressed concrete) hybrid I-girder of 40 m length, in order to verify a new type of joint splicing steel and PSC segments. The spliced hybrid girder offers a competitive solution to medium-span bridges, with its various benefits such as a transportation constraint solution, high quality girders, span-length flexibility, the advantage of a hybrid system, and others. At the same time, it requires a proper joint connecting its PSC and steel segments at a site. A new type of joint consisting of parallel perfobond ribs, encased prestressed concrete, and steel plates, is adopted and tested to remove the vulnerabilities from joint areas where PSC I-section and steel I-section are connected. After the PSC segments with the joint and the steel segment are fabricated in a factory, they are transported to a test site and spliced into one girder. The experimental results show that the spliced steel-PSC hybrid I-girder is of sufficient strength, ductility, and stiffness without giving failure of joint. Indeed, the joint clearly transfers the load between the steel and PSC segments without incurring damage. It is concluded that the applied joint can be an effective system guaranteeing sound performance up to the ultimate capacities of the spliced steel–PSC hybrid I-girder.

A Transferência de Conhecimento na Implantação de um Escritório de Gerenciamento de Projetos

A transferência de conhecimento na implantação de um escritório de gerenciamento de projetos (EGP) é muito preocupante, pois o mercado encontra-se cada vez mais competitivo e exigindo rapidez e assertividade nos projetos desenvolvidos nas organizações, contemplando menores prazos, custos e escassez de mão de obra qualificada e equipamentos para apoio ao projeto. A gestão do conhecimento organizacional na implantação de um EGP é fundamental para garantir um diferencial competitivo, juntamente ao comprometimento da alta administração, a qual subsidia esta implantação. O objetivo deste artigo é descrever como transferir conhecimento na implantação de um EGP, considerando a maturidade da aprendizagem ao longo da implantação e utilizando como estudo de caso uma empresa do segmento siderúrgico, pertencente a um grande produtor de aço mundial.