Lightweight Composite Deck Research Articles

Experimental study on bond behavior of steel bar embedded in thin UHPC

Due to the high compressive strength and excellent tensile properties of UHPC, reinforced UHPC with a thickness of 45 mm–60mm and a concrete cover of 15 mm–19mm has been used in the steel-UHPC lightweight composite deck. However, the researches about the bond behaviors of steel bar in UHPC with the concrete cover less than 20 mm were still limited. This paper aimed to study the bond behaviors of steel bars in UHPC with a thinner concrete cover (≤20 mm) and develop the calculation method for the lower bound of bond strength. A program of pullout test was conducted using the tensile test setup mimicking the tensile stress condition of structural members. The effects of concrete cover (10 mm, 15 mm and 20 mm), steel fiber volume fraction (0.5%, 1% and 2%), steel bar diameter (10 mm, 12 mm, 14 mm and 16 mm), embedment length of steel bar (4db, 6db, 8db, 10db) on the bond behaviors of steel bar in UHPC were investigated through 11 groups of pullout test specimens. The test results showed that most specimens failed in concrete cover splitting and the bond strength was influenced to different degrees by the test variates. The bond strength for steel bar in UHPC with a steel fiber volume fraction of 2% varied from 12.29 MPa to 15.88 MPa, and an embedment length of 8db with a concrete cover of 15 mm could ensure the steel bar with a diameter less than 16 mm reached its nominal yield stress of 400 MPa before the bond failure. On the basis of pullout test results in this study and the published test data, an empirical equation was proposed to predicted the lower bound of bond strength for steel bar in UHPC.

Study on early shrinkage and cracking of slab in UHPC light-weight composite deck based on ambient temperature and humidity effects

This study investigates the early performance and potential issues of ultra-high-performance concrete (UHPC) light-weight composite decks (LCBDs) used in municipal highway bridge design. The major objective of this research was to understand the complex evolution of temperature and humidity within immature UHPC thin layers, which can lead to deformation and secondary stress, potentially causing cracks and threatening the long-term applicability and safety of steel-concrete composite bridges. Understanding of the mechanism of this process will be the basis for subsequent work. The early performance of UHPC with ordinary concrete is compared. Besides, discussions are conducted on the basic thermal conductivity theory of three-dimensional porous media and the hydration mechanism of cement-based materials that are appropriate for early-stage UHPC. Subsequently, a refined thermo-mechanical coupling analysis method for steel-UHPC LCBD was proposed, implemented using ABAQUS, and validated through a UHPC composite beam test. This method was applied to calculate the early shrinkage of the UHPC layer in a steel-UHPC LCBD and evaluate the risk of cracking in an actual bridge expansion project, providing a rationality evaluation of a bridge design and its construction procedure.

A simplified analysis method for long-span suspension bridges within the deck overlay retrofitting process from asphalt to UHPC

The steel-ultrahigh performance concrete (UHPC) lightweight composite deck (LWCD) is increasingly adopted by in-service steel bridges to address the fatigue cracking issue for orthotropic steel decks (OSDs) and the premature damage issue for asphalt overlays. While for in-service long-span suspension bridges that need to be retrofitted by LWCDs, the response of the UHPC layer in casting is complex. Within the UHPC casting process, the moment of the stiffening girder changes continuously as the self-weight of the stiffening girder changes in casting, and the change of moment will produce strains in the UHPC portion set earlier; in other words, the UHPC portion cast latter will produce strains in the UHPC portion cast earlier. If the resultant tensile strains are too high, the UHPC layer may crack within the casting process, which should be avoided. In this paper, a simplified analysis method, based on the linearized deflection theory, was proposed to rapidly obtain the response of long-span suspension bridges in retrofitting without significantly compromising the accuracy of the analysis results. A new solving method based on exponential functions was proposed, which is simpler than the commonly used hyperbolic function-based method. The proposed method was implemented as computer codes in Matlab and verified through two examples: a single-span suspension bridge and a three-span suspension bridge. The simplified analysis method was used to perform a detailed analysis for the Yichang Yangtze River Expressway Bridge (YYREB), a 960-m-long single-span suspension bridge in China, for which the existing asphalt overlay was replaced by an LWCD in 2021. In the analysis, three cast sequences were considered for the UHPC layer, i.e., from end to end, from mid-span to ends, and from ends to mid-span. It is revealed that the mid span-to-ends cast sequence produces the minimum tensile strain in UHPC, so the cracking risk of UHPC could be well controlled by using this casting method. Thus, the mid span-to-ends cast sequence was adopted by the YYREB within the deck overlay retrofitting process from asphalt to UHPC.

Key Design Parameters Analysis and Calculation Theory Research on Bending Performance of Steel–UHPC Lightweight Composite Deck Structure

This paper aims to study the influence of key design parameters (e.g., reinforcement ratio, cover thickness, stud spacing, and thickness of the ultra-high-performance concrete (UHPC) layer) on the longitudinal and transverse bending performance, as well as the cracking load and ultimate bearing capacity calculation theory of steel–UHPC lightweight composite deck (LWCD) structure. Four transverse bending tests and four longitudinal bending tests on steel–UHPC composite plates and steel–UHPC composite beams were conducted, respectively. The refined finite element models of components with different key design parameters based on ABAQUS were established. The influences of different key design parameters on the transverse and longitudinal flexural behaviors (e.g., load-mid-span displacement curve, cracking stress, stiffness, elastic limit load, critical slip load, ultimate bearing capacity and ductility) were compared and analyzed in detail. The ultimate bearing capacity can be improved by increasing the thickness of UHPC layer and the reinforcement ratio of longitudinal reinforcement, and reducing the cover thickness and the spacing of studs. According to the longitudinal bending characteristics of the steel–UHPC lightweight composite deck structure, the calculation formulas for the cracking load and the ultimate bearing capacity of the steel–UHPC composite beam are proposed, and the calculated values are in good agreement with test results (the errors are basically within 10%), which is convenient for practical engineering applications.

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.

Study on Static and Fatigue Behaviors of Steel-UHPFRC Composite Deck Structure.

Ultra-high-performance fiber-reinforced cementitious composite (UHPFRC) is used in orthotropic steel deck (OSD) to form a lightweight composite deck structure (LWCD), which is expected to solve the problems of fatigue cracking of traditional steel deck and pavement damage. This paper aims to study the influence of key design parameters on longitudinal bending and transverse fatigue performance, as well as the ultimate bearing capacity calculation theory of the LWCD. A local finite-element (FE) model was built to evaluate the vehicle-induced stress ranges of six typical fatigue-prone details. In total, eight negative bending tests on steel-UHPFRC composite beams and one fatigue test on a steel-UHPFRC composite plate were conducted to investigate the longitudinal bending performance and the transverse flexural fatigue behavior of the LWCD, respectively. The results show that adding a 60-mm UHPFRC layer can significantly reduce the stress amplitude of six typical fatigue details by 44.8% to 90%. The failure mode of the longitudinal bending tests is the U-rib buckle and all UHPFRC layers exhibit multiple cracking behaviors when the specimens failed. The longitudinal cracking stresses of the specimens are between 20.0 MPa to 27.3 MPa. The reinforcement ratio and cover thickness have a great influence on the cracking stress. While the ultimate bearing capacity of specimens with different parameters has little difference. The calculation method of the ultimate bearing capacity of a steel-UHPFRC composite structure is proposed. When the strain at the bottom of the u-rib is taken as 1.2 times the design yield strain, the calculated results are in good agreement with the experimental results. No fatigue failure was observed after 66.12 million fatigue cycles under the design load, highlighting the favorable fatigue resistance of the proposed LWCD.

Effect of stress reversals on fatigue life evaluation of OSD considering the transverse distribution of vehicle loads

The effect of stress reversals, generated by vehicles passing the bridge deck in sequence from different transverse locations, has been underestimated or even ignored in the fatigue life evaluation of orthotropic steel decks (OSDs), which may result in an overestimated fatigue life of the whole bridge. In this paper, four distribution patterns of vehicle transverse locations were considered and the effect of stress reversals on the fatigue evaluation of a conventional OSD (COSD) and a lightweight composite deck (LWCD) was investigated from infinite-life and finite-life perspectives based on finite element analysis. The results show that the maximum stress range could be underestimated by over 40% if the most unfavorable stress reversal is underestimated. A convenient and efficient vehicle loading scheme was proposed to determine the accurate maximum stress range for the infinite fatigue life evaluation of OSDs. Besides, the stress reversals are found to have a significant effect on the finite fatigue life evaluation of both the COSD and the LWCD, and the fatigue life of COSDs could be overestimated by 95% if the stress reversals are ignored. Nevertheless, the effect of stress reversals on the finite fatigue life evaluation of the LWCD is much less than that of the COSD, which indicates a better anti-fatigue performance of the LWCD over the COSD. In addition, the stress reversals induced by overloaded trucks have a significant effect on the fatigue performance of OSDs. The results from the study can provide some references for the fatigue design and evaluation of OSD systems.

Design and Mechanical Properties of Steel‐UHPC Lightweight Composite Decks

Orthotropic steel decks (OSDs) have been widely used in long‐span bridges due to their advantages of being lightweight, having high capacity, and allowing rapid construction. However, due to the insufficiency of local stiffness of OSD, fatigue cracking and pavement damage have been common problems of OSDs worldwide. It seriously affects the safety and durability of long‐span bridges. Therefore, to solve this problem, this paper introduces an innovative steel ultrahigh‐performance concrete (steel‐UHPC) lightweight composite deck (LWCD). LWCD can reduce the fatigue stress of the conventional OSD by up to 80% and extend the fatigue life to twice the design requirements. Furthermore, engineering practices in China have proven that LWCD can effectively reduce manufacturing costs and maintenance costs throughout the whole life cycle of the structures. Thus, to provide references for design and maintenance of long‐span bridges, this paper introduces the structural design, construction techniques, joint construction design, repair methods, and economic benefits of LWCD in detail. Furthermore, numerical simulations and laboratory tests are introduced in this paper to validate the superiority of LWCD.

Dynamic Serviceability of Lightweight Composite Deck as Floor System Under Human Excitation

Lightweight composite deck is widely used as floor system due to the advantage of minimum weight as well as to speedy the construction process. There are numerous investigations on the structural behaviour of lightweight composite deck, but its reliability and understanding on dynamic serviceability remain ambiguous. Therefore, this study intents to numerically investigate the dynamic serviceability of lightweight composite deck as floor system. The lightweight composite deck with dimension of 2900 mm span and 900 mm was modelled in STAAD.Pro. The thickness of lightweight composite deck varied from 100 mm to 225 mm. The isotropic equivalent plate model and effective homogenous criterion were adopted for the geometry and material properties. Dynamic serviceability in term of natural frequency and displacement were analysed in corresponds to the thickness of lightweight composite deck. It is noticeable that by increasing the thickness led to the improvement in the natural frequency. In contrast, the displacement become smaller as the thickness become larger. It was identified that only the lightweight composite deck with thickness 200 mm and 225 mm comply the allowable limit.

Transverse bending behavior of the steel-UHPC lightweight composite deck: Orthogonal test and analysis

The lightweight composite deck (LWCD) is a new countermeasure to address issues of fatigue cracking in orthotropic steel decks (OSDs) and premature damage in asphalt overlays, which is composed of an OSD and a thin ultra-high performance concrete (UHPC) layer. The objective of this paper is to reveal the transversal bending behavior of the LWCD under negative bending moments. An orthogonal experimental test was accomplished on 40 steel-UHPC composite specimens. The specimens covered four parameters, i.e., the stud spacing, the UHPC thickness, the cover thickness, and the number of steel reinforcement in UHPC. The responses of the specimens were analyzed and discussed from different aspects, including the failure mode, the load-deflection curve, the strain distribution, the cracking status, and the interfacial slip. To facilitate the design of the LWCD, the influence of the four parameters on the average crack spacing, the cracking stress in UHPC and the ultimate load was discussed. In addition, equations for calculating the ultimate load of the composite specimens were proposed and were validated through the test results.

Multiparameter Fatigue Analysis of a Steel–Super-Toughness-Concrete Lightweight Composite Bridge Deck

This study aimed to comprehensively analyze the effects of the thickness of a super toughness concrete (STC) layer, the thickness of diaphragms, and the spacing of stud shear connectors on the fatigue property of a lightweight composite bridge deck. A multi-parameter analysis was performed on a steel-STC lightweight composite deck to facilitate its fatigue design. Based on a real bridge, a serial local finite element model was built to calculate the fatigue stress range of the typical fatigue-prone cracking details of the steel bridge deck under different combinations of the three parameters. On the basis of the FE analysis, the nominal stress of each fatigue-prone detail was obtained, and the following observations were obtained. First, the lightweight composite bridge deck structure could strongly enhance the local stiffness of the steel bridge deck, but its contribution to the global stiffness of the bridge deck is limited. Second, increasing the STC layer thickness from 45 mm to 60 mm could further reduce the fatigue stress range of fatigue-prone details in the steel deck. Third, increasing the thickness of the floor beams could improve the cracking details at the U-rib-to-diaphragm connection and butt weld at the U-rib lower edge, and the stress range reduction is about 20%-29%. Fourth, reducing the spacing of the stud shear connectors could obviously decrease the stress range of the U-rib-diaphragm welded joints and the arc cutouts in floor beams, and the stress range decreases by 22.01%-27.96%.

Static and fatigue properties of the steel-UHPC lightweight composite bridge deck with large U ribs

A lightweight composite deck (LWCD) is a bridge deck system composed of an orthotropic steel deck and an ultra-high performance concrete (UHPC) layer. In this paper, the LWCD was refined with the concept of large U ribs. Based on an example bridge, the Sutong Bridge in China, the new LWCD scheme with large U ribs was proposed. Calculation showed that the steel consumption was basically the same as that of the original design, while the weld seam length in OSD was decreased by about 38.7%. Global and local finite-element (FE) models were built for the new LWCD scheme. The analysis results showed that for the LWCD with large U ribs, the stress reductions on fatigue-prone details were close to those of the LWCD with normal U ribs. The FE analyses also indicated that the maximum tensile stress of the UHPC layer was 10.9 MPa. Further, a full-scale longitudinal specimen was tested under negative bending moments. The test results showed that the nominal cracking stress of the UHPC layer was 24.1 MPa, implying that the UHPC layer could meet the design requirement. In addition, a nonlinear FE analysis was performed to make a comparison between the theoretical results and the test results.

Fatigue Assessment of Steel-UHPC Lightweight Composite Deck Based on Multiscale FE Analysis: Case Study

AbstractA lightweight steel–ultrahigh performance concrete (UHPC) composite deck (LWCD) was developed for alleviating deterioration issues in orthotropic steel decks (OSDs). In recent years, the LW...

Fatigue Performance of a Lightweight Composite Bridge Deck with Open Ribs

An innovative lightweight composite deck (LWCD) is proposed for steel bridges to avoid premature fatigue cracking. The composite deck is composed of an open-ribbed orthotropic steel deck (OSD) and a thin ultrahigh-performance concrete (UHPC) layer. This study is based on a suspension steel bridge in China, namely, the Second Dongting Lake Bridge. The following investigations were performed: (1) preliminary finite-element analysis (FEA) was carried out to evaluate the vehicle-induced stress ranges (i.e., Δσ = σmax − σmin) of six typical fatigue-prone details; (2) parameter analyses were performed to investigate the effects of the shape of cutouts and the thickness of the floor beams; and (3) two fatigue tests, one that used a full-scale LWCD panel and another that used a LWCD beam specimen, were conducted to reveal fatigue performance of the OSD and the stud shear connectors, respectively. Results of the preliminary FEA show that, with the contribution of the UHPC layer, the vehicle-induced stress ranges at some fatigue details of the LWCD, such as the rib–deck plate welded joints and the splice welds of the longitudinal ribs, were reduced to be less than their constant-amplitude fatigue limits, which indicates theoretically infinite fatigue lives of these details. The parameter analyses reveal that the apple-shaped cutout had relative good fatigue properties among the four cutout schemes and that the thickness of the floor beams is recommended to be 14–18 mm. According to the fatigue tests on the composite panel specimen and on the composite beam specimen, both the open-ribbed OSD and the stud shear connectors exhibited satisfactory fatigue endurances, which were much greater than 2 million cycles. The current theoretical and experimental investigations reveal that the proposed open-ribbed LWCD has favorable fatigue performances.

Retrofit of an orthotropic steel deck with compact reinforced reactive powder concrete

Compact reinforced reactive powder concrete (CRRPC) was proposed to retrofit deteriorated asphalt overlays and to strengthen orthotropic steel deck (OSD) bridges. The resultant OSD-CRRPC composite deck is also referred to as a light-weight composite deck (LWCD) system. This paper provides experiences and lessons learned from the first application of CRRPC to retrofit the deficient asphalt overlay of an existing steel bridge in China. The paper includes information relating to finite element (FE) model analyses, a fatigue loading test, construction processes and a field measurement. FE analyses revealed that a 50-mm CRRPC layer decreased the vehicle-induced stresses in the OSD by 34–83% relative to an OSD with an 80-mm asphalt overlay. As a result, the fatigue life of the OSD could be extended significantly. The static and fatigue safeties of CRRPC were proved by comparing the predicted and experimental stresses, and field construction demonstrated the feasibility of the proposed system. CRRPC developed no shrinkage cracks after hot-steam treatment in field application. In addition, a field measurement verified that CRRPC outperformed an asphalt overlay in reducing the vehicle-induced stresses in the OSD. The results demonstrate the safety and feasibility of retrofitting and strengthening OSD bridges with CRRPC.