Composite Deck Research Articles

Impedance-based damage assessment of steel-ECC composite deck using piezoelectric transducers

The excellent crack and fatigue resistance of Engineering Cementitious Composites (ECC) materials makes it promising to be used in orthotropic bridge deck system. However, overloading and fatigue load might cause structural damage and, consequently, structural performance degradation. In this work, the piezoelectric lead-zirconate-titanate (PZT) transducers are used to identify the structural damage of the steel-ECC composite deck by implementing both experimental test and numerical simulation. Two steel-ECC composite deck are prepared and four-point bending loading tests are performed on the two specimens to introduce several damage scenarios by gradually increasing the load. The impedance output signals of the piezoelectric sensors are measured under different damage scenarios, and the damage index are extracted to identify the structural damage. A finite element model of the steel-ECC composite deck is established, and the impedance signals with different damage scenarios are calculated and used to assess the structural damages. According to the experimental test and numerical simulation, the impedance-based technology performs to be an effective way to identify the structural damage of the steel-ECC composite deck.

Fatigue assessment of steel-UHPC composite deck with a thin polymer overlay in a long-span suspension bridge under static and random traffic loads

Steel-ultra-high performance concrete (UHPC) composite deck emerges as a novel structure that is promising to improve the fatigue performance of orthotropic steel deck (OSD). However, a long-span suspension bridge has a strict requirement on the self-weight of a steel-UHPC composite deck because it is susceptible to dead load variations. This study evaluates the fatigue performance of the steel-UHPC deck with a thin polymer overlay (TPO) in the Yichang Yangtze River Highway Bridge, a long-span suspension bridge, under static load and random traffic flow. The measured strains at the fatigue-prone details were employed to calculate the equivalent stress ranges and total fatigue life of the steel-UHPC deck. A three-dimensional finite element model was established and validated by experimental measurements to evaluate the steel-UHPC deck’s stiffness and the TPO layer’s crack resistance. The differences between the stress values predicted by the validated model and the experimentally measured ones were around 5%. The results showed that the steel-UHPC deck with TPO significantly reduced fatigue-prone details’ equivalent stress ranges without increasing the dead load. The maximum stress reduction at various details reached 62%, and the total fatigue life at each detail in the steel-UHPC deck reached infinite life. The TPO layer has enough crack resistance in case the deck is overloaded by 50%. Compared with the original deck, the steel-UHPC composite deck improves the OSD’s local stiffness and reduces relative deformation between structural components, thus reducing the stress ranges at fatigue-prone details and improving the bridge deck’s fatigue performance. The results can provide a reference for the design and retrofit of the deck overlay of the long-span suspension bridge with OSD.

Fatigue behavior evaluation of full-scale OSD-UHPC composite bridge deck system

To investigate the fatigue performance and fatigue damage process of the Orthotropic Steel Deck (OSD) - Ultra-High Performance Concrete (UHPC) composite bridge deck, a two-span continuous full-scale specimen was designed and tested under cyclic loading. Test results showed that the fatigue cracks firstly initiated near the lower part of the weld toe of the rib-to-cross beam welded joint, and then cracks along the weld length of the U-rib butt-welded joint developed. These observations followed by the OSD-UHPC interface debonding. The U-rib bolted joint exhibited better fatigue resistance than the U-rib butt-welded joint. The S-N curves of the rib-to-cross beam welded joint, the U-rib butt-welded joint and the U-rib bolted joint were established based on existing fatigue test data, and were compared with provisions in design codes. The S-N curves from the beam test for the short-headed stud connectors were compared with that from the push-out test. And the established S-N curves with 95% survival probability from the push-out test could be used to assess the global fatigue performance of the composite deck. Considering the durability-based critical crack width of UHPC, the established tensile S-N curve regarding critical UHPC crack width of 0.05 mm could be used to evaluate the anti-fatigue cracking ability of the UHPC layer in the composite deck system.

Monitoring and Simulation Study on Shrinkage Behaviour of Steel-UHPC Composite Deck

Combining an Ultra-High Performance Concrete (UHPC) layer with an orthotropic steel bridge deck by stud connectors could enhance the fatigue performance of a deck system because of the improved system stiffness. However, UHPC is featured by significant early-term shrinkage owing to the material composition. Inappropriate constraints introduced by stud connectors may result in a high risk of UHPC cracking, leading to unexpected safety and durability issues. This study investigated the early-term shrinkage behaviour of a steel-UHPC composite bridge deck by conducting an 80-day shrinkage monitoring test at first. The monitoring results showed that the UHPC hardening process lasted for over 44 h, and the maximum UHPC shrinkage under constraint in the composite deck was only 120 μϵ, while the shrinkage induced compressive stress on the steel deck plate reached 36 MPa. Meanwhile, qualitative simulation and parametric analysis works were carried out to investigate structural dimension effects on shrinkage behaviour of the composite bridge deck in detail. According to the analysis results, the UHPC shrinkage and the induced stress on the steel deck plate had obvious uneven distribution feature. And stud spacing was found as a sensitive factor to shrinkage constraint extent compared with rebar spacing and stiffener thickness. Therefore, a rational stud spacing and design suggestions for practical applications were discussed in addition.

Experimental and analytical study on crack resistance of fully prefabricated steel-UHPC composite deck using PBL connectors

To improve the crack resistance of a fully prefabricated composite deck, this study employed perfobond rib (PBL) connectors as the anti-cracking structure at the steel–ultra-high-performance concrete (UHPC) interface. Eight specimens were designed and tested through four-point bending tests. The crack development, ultimate failure pattern, and load-deflection response were observed. According to the test results, the interface employing the PBL connectors achieved satisfactory crack resistance, which was even better close to the cast-on-site reinforced UHPC section. The amount and size of the holes in the PBL connectors, and the placement direction, had an obvious impact on the crack resistance. An analytical model is proposed to describe the cracking mechanism at the steel-UHPC interface. A comparison with the test results revealed that the analytical model has satisfactory accuracy. Sensitivity analyses were performed on the three main design parameters, and the initial cracking strength of the interface was most sensitive to the height of the PBL connectors.

Saleyard Bridge, UK – an improved approach to precasting steel–concrete composite bridge decks

Saleyard Bridge carries the A465 Heads of the Valleys Road over the River Clydach near Gilwern, Monmouthshire, UK. It comprises a 67 m single-span steel–concrete composite multi-girder superstructure made integral with the abutments. A full-depth precast deck was chosen to tackle site constraints and improve constructability. The alternative precast panel connection detail developed used straight laps to overcome the problems that can arise from using typical U-bar loop type connections between precast deck panels. The successful use of the precast panels proved that a deck design with straight laps was a practical alternative. The ability to increase the multi-beam centres and avoid cantilever edge formwork created a more economical solution with savings estimated at £500 000. The paper examines the detailed design and construction planning needed to realise the savings and speed up construction as well as improving site safety. The lessons learnt are also applicable to the wider use of precast panels as an alternative to in situ concreting.

Experimental and Numerical Study on UHPC–RC Decks within Hogging Moment Region

Steel–concrete composite continuous bridges can take full advantage of concrete and steel, but in regions with hogging moments, cracking of the concrete deck is a big issue affecting the durability of bridges. In order to solve cracking problems within the hogging moment region, this study proposes a composite deck method using ultra-high-performance concrete (UHPC) and regular concrete (RC). In this way, the layers of UHPC and RC are composited to take advantage of the high tensile strength of UHPC materials to improve the anti-crack performance of the concrete deck within the hogging moment region. Four different specimens were designed to account for different layer thickness of UHPC. Bending experiments of the UHPC–RC composite deck were undertaken and a corresponding finite element model was established to study the behavior of the UHPC–RC composite deck. The regularity of crack development in different UHPC layer thicknesses was revealed, and the load-displacement results were compared to investigate the ultimate capacity of a steel–concrete composite bridge structure using a UHPC–RC composite deck. Finally, with consideration of material cost, a reasonable UHPC layer thickness suitable for the composite deck was obtained to provide a reference for the design of a UHPC–RC composite deck.

Experimental and analytical studies on flexural behavior of composite bridge decks with orthotropic steel deck and ultra-high-performance concrete (UHPC) slab under negative moment

Ultra-high-performance concrete (UHPC) has been used to enhance the mechanical behavior of orthotropic steel bridge decks through steel-UHPC composite actions. This research develops a method to evaluate the flexural behavior of steel-UHPC composite sections via experimental and analytical investigations. Four composite deck specimens were fabricated and tested to study the mechanical behaviors under negative moment along the transverse and the longitudinal directions. A polyline model is proposed to link the strain, crack width of UHPC, and the bearing capacity of steel-UHPC composite decks, considering the crack behavior of UHPC with different fiber contents. The polyline model is used to derive engineer-friendly formulae for the flexural behavior of composite decks. Results showed that the proposed method provided adequate predictions for the flexural behavior of composite decks in the evolution of the crack width in UHPC with different fiber contents.

A Simple Mechanical Model for Steel Beam – Column Slab Subassembly Nonlinear Cyclic Behaviour

ABSTRACT A simple strut-and-tie macro-model has been developed to represent the seismic behaviour of a composite deck slab, acting as part of a steel moment-frame beam-column-slab joint. The moment frame is subject to large lateral deformations, representing those from a strong earthquake, and yielding occurs at the beam ends. The frame sub-assemblies were modelled as elastic line elements connected with non-linear/linear spring elements. The model behaviour was compared to experimental test results. It was found that the model developed satisfactorily represented the envelope cyclic behaviour of the test frame sub-assembly with the different slab configurations. It is easy to implement in practice using widely used commercial software available to practising engineers.

FiberCore Europe to replace or reinforce concrete decks with composites in Norway

FiberCore Europe's Norwegian partner, Module Solutions & Systems, will, together with Multiconsult, design and deliver innovative and sustainable solutions for bridge maintenance to Vestland County Municipality, in Norway. Two concepts will be designed, one of which, SUREbridge with InfraCore® Inside, reinforces the existing concrete deck with a thin composite deck on two bridges. The second concept replaces the existing bridge deck in concrete with a composite deck on two steel girder bridges.

Experimental study on flexural behavior of hollow steel-UHPC composite bridge deck

The application of UHPC might reduce the weight of the bridge deck and improve its crack resistance and durability. This study proposes a hollow steel-UHPC composite deck composed of the hollow steel tube and UHPC without shear connectors. The flexural test was performed on the hollow steel-UHPC composite deck to evaluate the effects of the embedded steel tubes, steel bars, UHPC material, and flange thickness. In addition, the mechanical properties of hollow steel-UHPC composite decks were compared with waffle decks and solid concrete decks. Results indicated that the hollow steel-UHPC composite deck had excellent bending capacity and material utilization. The load-deflection curve of the composite decks could be divided into four stages: elastic stage, working stage with cracks, nonlinear stage, and fully plastic stage. Without any additional shear connection, the steel-UHPC interface slip did not occur until the load reached 0.89Pu. In the ultimate limit state, the strains at the mid-span cross-section of steel and UHPC were almost the same, suggesting that there was a good composite effect between the embedded steel tube and the outer UHPC. The embedded steel tube had a significant influence on improving the original stiffness (K0), the stiffness at the working stage with cracks (K1), and the flexural capacity (Pu) of composite decks. The flexural failure of the hollow steel-UHPC composite deck was controlled by the tensile zone. Finally, a theoretical formula was proposed to predict the flexural capacity of the hollow steel-UHPC composite deck.

Shrinkage effect and mechanical performance of steel-ultra-high performance concrete composite deck under negative bending action

Shrinkage effect can result in damages in steel-UHPC composite decks. And these damages may even cause mechanical performance degradations. The details are critical to deck design practice and evaluation theory establishment while not being clearly understood. In this study, static shrinkage monitoring and negative bending tests on two full-scale segmental composite deck specimens (D12 and D16) were sequentially conducted. 12-mm- and 16-mm-diameter reinforcements were respectively embedded in the specimens. Simulation and parametric analysis were executed as well for further understanding. The 90 days static shrinkage monitoring results showed the maximum induced compressive strains on reinforcements of D12 and D16 were 559 με and 328 με. The maximum compressive strains on steel deck plates were 80 με and 82 με. It indicated shrinkage effect cannot be ignored. The bending test results showed the UHPC tensile strain maximums were 1458 με and 1149 με in the two specimens when the maximum UHPC crack width was 0.10 mm. Moreover, the simulation analysis results also showed that the model with 90 days shrinkage effect had a 16% lower bending secant stiffness at the load level equivalent to allowable UHPC crack width. And the reduction increased to nearly 40% when the crack width reached 0.10 mm. In addition, the parametric analysis showed that a strain-hardening feature could be favorable to delay the UHPC damage evolution compared with a strain-softening one with relatively lower tensile strength. These results provided important support to the design practice of steel-UHPC composite decks.

Bending behavior of steel-UHPC composite bridge deck based on epoxy adhesive

Using ultra-high performance concrete (UHPC) as the pavement layer on the orthotropic steel deck (OSD) can greatly enhance the rigidity to solve the fatigue cracking of the steel deck and the resulting damage to the pavement layer. However, the thin UHPC layer limits the extensive use of the short stud connector. In this study, three types of interfaces were designed by introducing different additives into the epoxy matrix, and the shear properties of each interface and short stud connector were compared. Then, the influence of short stud connectors and optimized interface on the composite bridge deck’s bending property was analyzed through the composite bridge deck’s bending test. Moreover, the mechanical behavior of the interface in the composite bridge deck is discussed based on the finite element model. The results show that the ultimate load of the composite bridge deck with the optimized interface is reduced by 21.5% compared with that of the composite bridge deck with the short stud connector. However, the composite bridge deck with the optimized interface has higher bending stiffness before failure and is less affected by cyclic loading. Moreover, the composite bridge deck with the optimized interface is unsuitable for cyclic loading conditions when the defect area reaches 30%. Finally, the numerical simulation of the composite bridge deck with the optimized interface is successfully realized based on the cohesive zone model, and the applicability of the interface in the composite bridge deck is verified.

Analysis of composite bridge deck considering the effects of concrete cracking

Abstract Cracking in composite steel-concrete bridge decks is a common problem in civil engineering. Before, or shortly after, the bridge is subjected to live loads; various levels of cracking can appear, mostly due to plastic shrinkage and temperature effects. This paper presents an investigation of the behavior of cracked concrete in a composite deck slab of a railway bridge supported by steel girders using the finite element method. Eurocode 4-2 proposes a few simplified methods for calculating shrinkage and cracking effects in concrete. Through the proposed methods of analysis, an analytical simulation of a continuous composite steel-concrete bridge deck is performed and some practical recommendations for analyzing beam girders of this type are given.

Numerical and analytical methods for the design of beam-column sub-assemblies with composite deck slab

A finite element numerical model is used to estimate the force displacement backbone curve of steel moment frame beam-column-joint subassemblies tested at large scale under repeated cyclic loading with different composite deck slab configurations. The slab configurations included: no-slab; fully isolated slab; two configurations for detailing the slab near the region between the column flanges; and a full depth reinforced slab. Then, a simple analytical model was developed so that designers can estimate the likely peak strength due to slab effect. This analytical model considers the common deformation modes and the strength hierarchy. It was found that the finite element numerical model captured the backbone envelope of experimental tests done on different slab configurations for the bare frame, isolated slab and full depth slab configurations, but overestimated the strength at larger displacements for the other configurations due to difficulty in considering the slab modes of failure. The simple analytical model considered the nonlinear deformation modes of steel beam plastic hinging, concrete crushing both outside the column flange and within the beam flanges, slab shear fracture between the column flange tips, slab longitudinal and lateral reinforcement yielding as it carried the subassembly moments and transferred forces between the steel frame and the slab, and shear stud deformation. The proposed analytical model matched the experimental strengths and failure modes. The proposed finite element model is suitable for research, and the analytical model matched the experimental results, and is suitable for consideration in design.

Experimental and numerical studies on the two “lock-in” regions characteristic of vertical vortex-induced vibration of Π-shaped composite bridge deck

The Π-shaped bridge deck may easily occur vertical vortex-induced vibration, due to the bluff body aerodynamic configuration, which may cause the uncomforting of vehicles and pedestrians on the bridges. The present study mainly focused on the two “lock-in” regions characteristics of vertical vortex-induced vibration (VIV) of Π-shaped bridge deck, which can reveal the aerodynamic mechanism of vibration mitigation countermeasures. The vertical VIV response of original Π-shaped deck and those with different countermeasures are experimentally investigated detailly. Computational fluid dynamics (CFD) method is employed to numerically simulate the surrounding flow field of original girder section and those with different aerodynamic countermeasures. The numerical method is firstly verified through the comparison with the results of corresponding experimental results obtained in wind tunnel test. Afterwards, the flow pattern and vortex structure around the girder section simulated by CFD are utilized to interpret the effects of the mitigation countermeasures. The numerical results show that: (a)The vibration mitigation effect in the first vortex “lock-in” region is not sensitive to the position of the aerodynamic countermeasures, while the vibration mitigation effect in the second “lock-in” region is more sensitive to the position of the aerodynamic countermeasures; (b) The phase of aerodynamic lift and displacement response is close to synchronization in the ascending section of the VIV amplitude, greater than 90° in the descending section, and close to 180° outside the vortex-induced resonance range. The first vertical VIV region is related to the “Karman vortex street” at the trailing edge of the section, while the second vertical VIV region is related to the vortex shedding at the lower edge of the front end of the section and the secondary vortices on the upper surface.

Tensile behavior of a prefabricated Steel–UHPC composite deck system with notched perfobond strips

This paper proposes a prefabricated steel–ultra-high-performance concrete (UHPC) composite deck (PSUCD) system equipped with notched perfobond strips (NPBLs) for long-span cable-stayed bridges. Compared with the use of an ultra-thin UHPC overlay, the proposed deck system better leverages the high compressive strength of the UHPC. Seven full-scale composite panel specimens with varying details of joint interfaces and shear connectors are subjected to tensile tests. The experimental results reveal that compared with a monolithic UHPC layer, the tensile strengths of the UHPC layer at the initial and nominal cracking (corresponding to a maximum crack width of 0.05 mm) are reduced by 47 % and 64 %, respectively, when flat joint interfaces are introduced and by 16 % and 40 %, respectively, when the interfaces are rectangular-tooth-shaped. The higher steel reinforcing ratio derived from the use of NPBLs placed across the joint interfaces leads to a distinct improvement in the post-cracking performance of the wet joints. Considering the weakened tensile strength and sectional area ratio of the joint interfaces, a prediction method for the crack widths at the wet joints in PSUCD systems is developed, and its prediction accuracy is verified.

Behaviour of the lockbolt demountable shear connector under combined shear and tension loading

A demountable ‘lockbolt’ shear connector (LB-DSC), consisting of a short partially threaded bolt that is locked on a steel flange to eliminate tolerance and initial slip issues and a compatible machined tube that can be fastened/unfastened over the bolt to facilitate the easy and fast disassembly process for reuse of all components, was proposed for use in composite floors or decks of buildings or bridges. This paper focuses on the numerical investigation of the structural behaviour of the LB-DSC under combined tension and shear loading. A detailed finite element method (FEM) model considering material and contact nonlinearity was built and calibrated based on previous standard pushout tests on the LB-DSC. The calibrated FEM model was used to investigate the effects of various parameters on tensile and shear behaviour of the LB-DSC, including the concrete strength of slab, the bolt diameter and strength, the steel tube thickness, and the presence and strength of infill grout. The shear resistance of the connector is significantly reduced when a tensile force more than 20% of the tensile resistance of the connector is applied. Design equations for predicting the tension resistance and tension-shear interaction are proposed to expand the application of the LB-DSCs in sustainable steel–concrete composite construction.

Full-scale experimental study on continuous UHPC slabs of steel-UHPC composite deck system

The heavy self-weight and the cracking of normal strength concrete (NSC) deck slabs hindered the application of steel-concrete composite girders in long-span bridges. These problems can be solved by using ultra-high performance concrete (UHPC) deck slabs instead of the NSC deck slabs. Based on Yellow River Bridge of Zhanhua-Linzi Highway, a steel-UHPC composite cable-stayed bridge with span length of 442 m, full-scale tests on seven continuous UHPC (NSC) deck slabs were conducted. The studied parameters were sagging-to-hogging reinforcement ratio, concrete type, yield strength of steel bars and wet joints. The static properties of continuous UHPC (NSC) deck slabs were investigated in detail, including failure modes, load-deflection response, cracking behavior, strain development and moment redistribution. Discussions were made on the effect of different parameters according to the experimental data. Results showed that the use of UHPC can avoid shear failure, which was the case for the continuous NSC slab. Reducing the sagging-to-hogging reinforcement ratio from 1.00 to 0.63, the failure mode changed due to the altered formation order of plastic hinges. The ultimate capacity was decreased while the ductility and moment redistribution were improved by decreasing the yield strength of steel bars. The existence of wet joints significantly weakened the deck slabs. Strengthening the wet joints with steel plates can effectively compensate for this effect and even achieve better mechanical properties compared with integrally cast slabs. Furthermore, placing a comb-shaped wet joint at the intermediate support of continuous slab will result in a certain decrease of ultimate capacity and stiffness, which is acceptable for the transverse direction with relatively small internal forces. It is suggested that wet joints should be avoided at the supports of continuous deck slabs along the longitudinal direction.

Steel-alkali activated cement based ultra-high performance concrete lightweight composite bridge decks: Flexural behavior

The production energy consumption and carbon dioxide emissions of alkali activated cement-based material (AAM) are low which make it environmentally friendly. At the same time, alkali activated cement based ultra-high-performance concrete (AAUHPC) has equivalent mechanical properties to ultra-high performance concrete (UHPC). In this paper, the effects of the loading regime, the thickness of concrete cover, reinforcement ratio and the degree of shear connection on the bending performance were investigated, and the failure mode, load–deflection behavior, load–strain response and interface slip between the AAUHPC overlay and steel deck were analyzed. The results show that the bending resistance of a steel-AAUHPC lightweight composite deck is equivalent to that of a steel-UHPC lightweight composite deck (LWCD). Under both positive and negative moment, the evolution of the load–deflection and load–strain response of a LWCD has staged characteristics. An increase of the thickness of concrete cover can delay the arrival of the yield stage and reduces the peak value of the bending strain, while improving its bending performance. An increase of the reinforcement ratio can effectively reduce the ultimate tensile strain at each stage of the composite plate, delay crack development, reduce the crack width, and greatly improve the ductility of the steel-AAUHPC lightweight composite deck. An increase of the degree of shear connection significantly increases the compressive strain in the steel deck, and significantly reduces the relative slip between the AAUHPC overlay and steel deck, thereby improving the composite action. It can provide a basis for the design and application of steel-AAUHPC lightweight composite decks and promote the development of more environmentally sustainable steel–concrete composite structures.