Experimental and numerical study on the mechanical behavior of prestressed continuous composite I-girder bridges with partial connection

This material may be downloaded for personal use only. Any other use requires prior permission of the American Society of Civil Engineers. This material may be found at https://ascelibrary.org/doi/abs/10.1061/JBENF2.BEENG-5955.A partial connection–prestressing (PCP) method is proposed in this paper to decrease the prestress that was transferred to steel girders in the negative moment region of steel–concrete composite bridges. The partial connection is achieved by the application of rubber-sleeved studs (RSS) in the prestressed concrete slab in the negative moment region. Since there is no experimental research on the PCP method in continuous composite girders, to the best of the authors’ knowledge, two continuous composite girders were tested under a four-point static load to evaluate their mechanical performance. The test results showed that without decreasing the ultimate strength and overall stiffness of the steel–concrete composite girders, the PCP method enhanced the cracking load (Pcr) 3.1 times. In addition, 12.5% of the prestressing force was transferred into the steel girder at the internal support section with the PCP method, and the girder without the PCP reached 25.9%. Then, to elucidate the partial interaction effect and prestressing effect on continuous girders’ mechanical behavior, numerical models were developed and calibrated with the test results. From the numerical analysis, compared with normal composite girders, the application of RSS or prestressing could improve Pcr by 11.8% and 157.0%, respectively, and the value increases to 234.3% when RSS and prestressing are applied at the same time. The results indicate that the application of RSS in the negative moment region could effectively increase the prestressing efficiency in the concrete slab and enhance the bridge's durability.This research is sponsored by the National Natural Science Foun-dation of China (No. 51978501) and the Major Research and De-velopment Project of Jiangxi Province (No. 20165ABC2800).Peer ReviewedPostprint (author's final draft

Mechanical performance based rationalization research on steel-concrete double composite action

Casting an extra concrete bottom layer to a steel-concrete composite box girder in a hogging moment region can increase sectional stiffness and prevent steel buckling. However, a lower sectional neutral axis may not be favorable to concrete slab cracking and steel flange stress control. To this end, a double composite girder segment was proposed and investigated. Particularly, a static loading test on a large-scaled two-span continuous girder specimen with the double composite action in hogging moment region was conducted for mechanical investigation. Meanwhile, parametric analysis was carried out as well for a rational design scheme of the double composite section. The test results revealed that the load-carrying capacity of double composite section could be increased due to the contribution of extra bottom concrete layer. The transverse deformation of steel parts was favorably constraint. The parametric analysis results indicated that slab thickness that was 15% of steel girder height could provide most obvious contributions to the improvements of both sectional load-carrying capacity and cracking moment. Due to the additional reinforcement, the steel web thickness of double composite girder can be saved 16.7% and the steel bottom flange thickness only needs to meet the constructing requirement compared with common composite girder. Besides, the analysis also showed replacing the tub section with steel box section in the hogging moment region can reduce the stress on top flange by 24.4%. These results are an important basis for establishing a rational design scheme for the novel double composite section.This research is sponsored by the National Natural Science Founda-tion of China (No. 51978501) and the China Scholarship Council (No. 202106260050). The supports are gratefully appreciated.Peer ReviewedPostprint (author's final draft

Behavior of Orthotropic Steel-UHPC Composite Bridge Deck under Cyclic Loading

In recent years, ultra-high performance concrete (UHPC) has been introduced in the design of orthotropic steel decks (OSD) to reduce the risk of fatigue cracking. To investigate the fatigue behaviour and fatigue damage process of the orthotropic steel-UHPC composite bridge deck, a fullscale specimen was designed and tested under cyclic loading. Test results show that the fatigue resistance of orthotropic steel-UHPC composite bridge deck satisfies the requirements of the designed vehicle load up to 2 million cycles with no cracks occurred in this phase. Rib-to-crossbeam weld and U-rib butt-welded connection are the two most vulnerable details to crack in OSD under cyclic loading. The fatigue resistance of U-rib bolted connection was investigated, and it is concluded that it performs better than that of U-rib butt-welded connection. The short-headed studs fractured under excessive cyclic loading and 5 types of the fatigue failure modes are identified. And the UHPC layer above the crossbeam exhibited limited number of cracks with the maximum crack width less than 0.05mm at the end of the cyclic, much beyond the requirements.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Steel & Composite Structure

Structural performance and on-site monitoring of steel-concrete composite bridge with link slab

In this paper, the project case of Qiwu bridge in Jiangxi Province using link slab action between simply sup-ported spans is introduced. The structural system of Qiwu Bridge consists of a series of 3 simply supported steel-concrete composite spans connected at the pier supports by a link slab, so at this point only continuity through the concrete slab is achieved (semi-continuous bridge). This solution has both advantages of smooth driving condition of continuous bridge and enhancement of durability by removing expansion joints and clear structural behavior as simply supported spans. A non-linear finite element model of Qiwu Bridge was estab-lished through ABAQUS to simulate and predict the mechanical response and structural performance of this semi-continuous solution. Numerical results showed that the removal of the shear connection between steel beams and concrete slab close to the supports magnificently increased the stress level in the shear stiffness mutation region and made it easier to crack. A monitoring plan is also introduced to follow the actual structural response of Qiwu bridge during construction and along the service life to check the long-term performance of the proposed solution. The monitoring system is also described in the paper and the preliminary results during the early construction stages are also presented.Postprint (published version

Behavior of short-headed stud connectors in orthotropic steel-UHPC composite bridge deck under fatigue loading

The short-headed stud connectors play a critical role on the interaction of the orthotropic steel deck (OSD) and the ultra-high performance concrete (UHPC) layer in orthotropic steel-UHPC composite bridge deck. In this paper, the fatigue behavior of these short-headed stud connectors was experimentally investigated in a beam test. The failure modes of the short-headed stud connectors were identified and classified into 5 types. The fatigue test results were analyzed by linear regression analysis neglecting run-outs and treating run-outs as failure respectively. On the other hand, the maximum likelihood estimation (MLE) approach was used to shape the S-N curve by considering the influence of run-outs. Additionally, the push-out and beam fatigue test data were compared, and the push-out test presented a relatively conservative result. Last, the applicability of existing specifications on design guidelines regarding the short-headed stud connectors design in orthotropic steel–UHPC composite bridge deck is discussed, and a design S-N curve with 95% survival probability is proposed.</p

Application of partial shear connection in steel–concrete semi-continuous composite girder bridges

This is an Accepted Manuscript of an article published by Taylor & Francis Group in Structural Engineering International on 2022, available online at: http://www.tandfonline.com/10.1080/10168664.2022.2048436In the hogging moment regions of steel–concrete composite continuous girder bridges, a detrimental condition appears such that concrete slab bears tensile stress and the steel girder bears compressive stress. Decreasing the shear connection in the hogging moment regions helps to improve the mechanical performance for steel–concrete continuous composite girder bridges. In this paper, analytical models for the calculation of composite girders considering partial shear connection (PSC) action are discussed. A project case of Qiwu Bridge in Jiangxi Province using partial shear connection action is introduced. A nonlinear finite element model of Qiwu Bridge is established through ABAQUS® to simulate and predict the mechanical properties and structural performance. Based on the finite element method results, the influence of PSC on various parameters is analysed by performing a parametric analysis. Numerical results show that arranging a partial shear connection region can effectively reduce the crack region and disperse areas having high stress concentration, but shear stiffness mutation can significantly increase the stress level at the edge of the partial shear connection region.This work was supported by the China Scholarship Council [Grant number: 202106260050] and the Zhejiang Provincial Program of Traffic Engineering Construction [Grant number: 2020031].Peer ReviewedPostprint (author's final draft

Modeling and Testing of a Composite Steel–Concrete Joint for Hybrid Girder Bridges

A hybrid girder bridge adopts a steel segment at the mid-span of the main span of a continuous concrete girder bridge. The critical point of the hybrid solution is the transition zone, connecting the steel and concrete segments of the beam. Although many girder tests revealing the structural behavior of hybrid girders have been conducted by previous studies, few specimens took the full section of a steel–concrete joint due to the large size of prototype hybrid bridges. In this study, a static load test on a composite segment to bridge the joint between the concrete and steel parts of a hybrid bridge with full section was conducted. A finite element model replicating the tested specimen results was established through Abaqus, while parametric studies were also conducted. The test and numerical results revealed that the concrete filling in the composite solution prevented the steel flange from extensive buckling, which significantly improved the load-carrying capacity of the steel–concrete joint. Meanwhile, strengthening the interaction between the steel and concrete helps to prevent the interlayer slip and simultaneously contributes to a higher flexural stiffness. These results are an important basis for establishing a rational design scheme for the steel–concrete joint of hybrid girder bridges

Influence mechanism of Steel-concrete interlayer partial shear connections on mechanical properties of composite girders

A reduction in composite action using a partial shear connection (PSC) in the hogging moment region of a steel–concrete bridge can mitigate the concrete tensile cracking risk while maintaining the structural ultimate bearing capacity. To date, specific mechanical effects, important for the establishment of evaluation theory, have not been studied. To this end, four girders and six push-out specimens were tested for the effect investigation. Numerical analysis with material damage plasticity models and an analytical study were conducted for parametric and mechanistic investigations. The push-out test results showed that a wrapping rubber sleeve reduced the shear stiffness of the stud by 91.9%, whereas its strength varied slightly. The girder test results showed that arranging rubber sleeved stud (RSS) connectors in the composite girders reduced the girder load-carrying capacity and bending stiffness by 17% and 12%, respectively. Moreover, the concrete tensile cracking performance was improved. The analysis results showed that, for reducing the concrete tensile stress, the RSS connector in the girder had a more favourable effect on prestress distribution than increasing the ordinary stud spacing. In addition, an evident stress concentration appeared when the stud distance was increased. According to the analytical analysis of the girder under negative bending, the concrete tensile stress is exponentially related to the interlayer stud stiffness, and the exponential is expected to be 5/3. The research revealed the detailed mechanical behaviour of the girder with a PSC and simultaneously compared the effects of the two PSC methods. This research will help establish design and evaluation methods for PSC action.This research was sponsored by the National Natural Science Foundation of China (No. 51978501), Fundamental Research Funds for the Central Universities (No. 22120210437), and China Scholarship Council (No. 202106260050). This support is greatly appreciated.Peer ReviewedPostprint (author's final draft

A new gold(I) complex-Au(PPh3)PT is a deubiquitinase inhibitor and inhibits tumor growthResearch in context

Background: Ubiquitin-proteasome system (UPS) is integral to cell survival by maintaining protein homeostasis, and its dysfunction has been linked to cancer and several other human diseases. Through counteracting ubiquitination, deubiquitinases (DUBs) can either positively or negatively regulate UPS function, thereby representing attractive targets of cancer therapies. Previous studies have shown that metal complexes can inhibit tumor growth through targeting the UPS; however, novel metal complexes with higher specificity for cancer therapy are still lacking. Methods: We synthesized a new gold(I) complex, Au(PPh3)PT. The inhibitory activity of Au(PPh3)PT on the UPS and the growth of multiple cancer cell types were tested in vitro, ex vivo, and in vivo. Furthermore, we compared the efficacy of Au(PPh3)PT with other metal compounds in inhibition of UPS function and tumor growth. Findings: Here we report that (i) a new gold(I) complex-pyrithione, i.e., Au(PPh3)PT, induced apoptosis in two lung cancer cell lines A549 and NCI-H1299; (ii) Au(PPh3)PT severely impaired UPS proteolytic function; (iii) Au(PPh3)PT selectively inhibited 19S proteasome-associated DUBs (UCHL5 and USP14) and other non-proteasomal DUBs with minimal effects on the function of 20S proteasome; (iv) Au(PPh3)PT induced apoptosis in cancer cells from acute myeloid leukemia patients; (v) Au(PPh3)PT effectively suppressed the growth of lung adenocarcinoma xenografts in nude mice; and (vi) Au (PPh3)PT elicited less cytotoxicity in normal cells than several other metal compounds. Interpretation: Together, this study discovers a new gold(I) complex to be an effective inhibitor of the DUBs and a potential anti-cancer drug. Fund: The National High Technology Research and Development Program of China, the project of Guangdong Province Natural Science Foundation, the projects from Foundation for Higher Education of Guangdong, the project from Guangzhou Medical University for Doctor Scientists, the Medical Scientific Research Foundation of Guangdong Province, and the Guangzhou Key Medical Discipline Construction Project Fund

Behavior of short-headed stud connectors in orthotropic steel-UHPC composite bridge deck under fatigue loading

The short-headed stud connectors play a critical role on the interaction of the orthotropic steel deck (OSD) and the ultra-high performance concrete (UHPC) layer in orthotropic steel-UHPC composite bridge deck. In this paper, the fatigue behavior of these short-headed stud connectors was experimentally investigated in a beam test. The failure modes of the short-headed stud connectors were identified and classified into 5 types. The fatigue test results were analyzed by linear regression analysis neglecting run-outs and treating run-outs as failure respectively. On the other hand, the maximum likelihood estimation (MLE) approach was used to shape the S-N curve by considering the influence of run-outs. Additionally, the push-out and beam fatigue test data were compared, and the push-out test presented a relatively conservative result. Last, the applicability of existing specifications on design guidelines regarding the short-headed stud connectors design in orthotropic steel–UHPC composite bridge deck is discussed, and a design S-N curve with 95% survival probability is proposed.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Steel & Composite Structure