Longitudinal Joints Research Articles

Research on the Fatigue Performance of Composite Girders with CSW and ST Truss

To study the fatigue performance of a composite girder with corrugated steel web (CSW) and steel tube (ST) truss, based on an engineering object, a test and finite element (FE) analysis were carried out. The fatigue failure mode and the sensitivities of the hot spot stress to the geometric parameters of the composite girder above were studied. The position with the maximum hot spot stress and the fatigue crack position were discussed and determined. Furthermore, a fatigue life evaluation method was discussed. It was found that linear extrapolation was applicable to finding the hot spot stress. The fatigue performance evolution comprised three stages, including initiation, expansion, and failure of the fatigue crack. The fatigue crack initiation stage accounted for about 95.6% of its fatigue life, and the fatigue crack was opening type I. The maximum hot spot stress emerged at the endpoint of the inclined web of CSW (point S). The main reason for the behavior was that the inclined web had a small out-of-plane flexural stiffness but had to bear an out-of-plane bending moment. Moreover, for the same section of the CSW, the hot spot stress on the molding side was less than that on the non-molding side. The hot spot stress exhibited negative correlations with the chord diameter, chord thickness, and bend radius, meanwhile, it had the highest sensitivity to the chord diameter. The existing S-N curves were not suitable to evaluate the fatigue life of the composite girder with CSW and ST truss. Since the intersecting weld between the CSW and the chord was located in longitudinal welded joints, the hot spot stress method suggested adopting the basic fatigue strength of 100 MPa, corresponding to 2,000,000 load cycles. Meanwhile, an empirical calculation model of the S-N curve for the composite girder with CSW and ST truss was created.

Integrated waterproofing evaluation method for longitudinal joints of shield tunnel subjected to extreme surcharge: Numerical analysis and experimental validation

Sufficient waterproofing performance is critical to ensure a normal operation and safety of tunnels, and certain safety margin is essential to cope with uncertain external loads. This study proposes a novel methodology for evaluating the waterproofing performance of shield tunnels subjected to extreme surcharges, by integrating an analytic derivation, numerical analysis, and experimental validation. First, the analytical derivations of stresses at longitudinal joints and a finite element (FE) model for calculating the internal forces of tunnel linings under external loads are established; these are subsequently combined to compute the gasket deformation. Then, the stress–deformation curve of the gasket is fitted by a material-scale FE model to evaluate the contact stress against the underground water pressure. Finally, the methodology is validated via measurements from a full-scale experiment. The results help establish that the presumptions derived from the proposed method are consistent with the experimental results. It is also anticipated that the waterproofing performance would reach the actual failure point at the approximate 4–7 m depth of the equivalent dumped soil, which is remarkably consistent with the on-site observations in the Shanghai Metro tunnel. This study provides an efficient and economical method in terms of engineering applications, with emphasis on the importance of structural analysis in the waterproofing evaluation.

Dislocation Detection of Shield Tunnel Based on Dense Cross-Sectional Point Clouds

Tunnel dislocation affects the stability and waterproof of the structure and endangers its service life. This paper presents a dislocation calculation method of shield tunnel based on cross sectional point clouds, which contain three main steps. First, a longitudinal joint detection method is proposed based on the circumferential joints detected by the existing gradient accumulation method. The point clouds containing capping block in each ring are converted into gray image to obtain the center line position of the block, and the longitudinal joints are calculated through combining with the tunnel design data. Second, tunnel appendages are removed quickly through unfolding the tunnel point clouds by cylinder projection and adjusting the parameters of the cloth simulation filtering algorithm. Finally, the circumferential dislocations are calculated by selecting multiple denoised sections on both sides of the joint and clustering the points at each angle. Meanwhile, the longitudinal dislocations are calculated through fitting the segments in each ring separately. Experimental results show that the automatic extraction rate of longitudinal joints is higher than 94%. The point clouds filtering method can quickly separate the very long tunnel lining from the close appendages attached to it. Meanwhile, the RMSE of the repeated circumferential and longitudinal dislocation are evaluated to be 1.56 mm and 0.57 mm respectively. Compared with the existing state of art methods, these values reach 1.75 mm and 0.63 mm. Through the method proposed, the dislocation value at any mileage and any angle of tunnel can be displayed intuitively.

In situ behaviour of an instrumented ring subjected to active eccentric tail seal passage

With common TBM configurations, the last assembled ring is contemporarily loaded by the thrust jacks and a generally off-centered tail seal system. In active eccentric scenarios of tail seal passage, significant tail-ring eccentricities can be locked by the opposing action of sealing pressures and thrust jacks (Gil Lorenzo, 2022). In this paper, the in situ response of the CAM3 instrumented ring in the Crossrail’s Thames tunnel (CTT) during active eccentric tail seal passage is examined in detail. The field data comprises selected TBM data, the distributed strain measurements of a Brillouin Optical Time Domain Reflectometer (BOTDR), plus the output quantities of vibrating wire strain gauges (VWSGs) and biaxial micro-electro-mechanical system (MEMS) tiltmeters. The field data was completed with relevant analytical models (Gil Lorenzo, 2019a; 2022) and compared with the outputs of the finite element (FE) model conducted alongside (Gil Lorenzo, 2021a; 2021b), showing good agreement with the FE-computed deformational quantities. It was found that the eccentric tail seal passage was the main cause of the high and uneven lining pressures detected at the early stages of tunnelling. The active eccentric tail seal passage, with upwards seal pressure gradients and downwards transverse jack forces, triggered the ring deformations in the unsupported tunnel, which became essentially irrecoverable. The radial rotations of the outer springline segment were largely affected by the interfacial quality between ram shoe and segment first, and between segments once the next ring was erected. The high sealing pressure gradients yielded a 0.12% ring distortion ratio increment already close to recommended construction limits. The top half of the non-bedded ring behaved as an arch-like structure with the crown segment supported by the neighbouring rings. At the lower segments, the hoop curvatures were the result of the ring ovalisation whereas, at the upper segments, the hoop curvatures were primarily induced by the inward radial jack forces. The outer springline segment worked under considerable torsion in the first TBM cycle. Initial in-plane angularities in longitudinal joints with contact at the rear can be accentuated by the advance of the sealing pressures from rear to front and become irreversible. Longitudinal cracking is more likely in the first TBM cycle while the ring is radially loaded at the rear only. In addition, a field example of concrete cracking in a segment with a defective packer support after ring erection is provided.

Implementing clinical decision support for reducing women Veterans' cardiovascular risk in VA: A mixed-method, longitudinal study of context, adaptation, and uptake.

Evaluations of clinical decision support (CDS) implementation often struggle to measure and explain heterogeneity in uptake over time and across settings, and to account for the impact of context and adaptation on implementation success. In 2017-2020, the EMPOWER QUERI implemented a cardiovascular toolkit using a computerized template aimed at reducing women Veterans' cardiovascular risk across five Veterans Healthcare Administration (VA) sites, using an enhanced Replicating Effective Programs (REP) implementation approach. In this study, we used longitudinal joint displays of qualitative and quantitative findings to explore (1) how contextual factors emerged across sites, (2) how the template and implementation strategies were adapted in response to contextual factors, and (3) how contextual factors and adaptations coincided with template uptake across sites and over time. We identified site structure, staffing changes, relational authority of champions, and external leadership as important contextual factors. These factors gave rise to adaptations such as splitting the template into multiple parts, pairing the template with a computerized reminder, conducting academic detailing, creating cheat sheets, and using small-scale pilot testing. All five sites exhibited variability in utilization over the months of implementation, though later sites exhibited higher template utilization immediately post-launch, possibly reflecting a "preloading" of adaptations from previous sites. These findings underscore the importance of adaptive approaches to implementation, with intentional shifts in intervention and strategy to meet the needs of individual sites, as well as the value of integrating mixed-method data sources in conducting longitudinal evaluation of implementation efforts.

Three-dimensional coupled hydromechanical analysis of localized joint leakage in segmental tunnel linings

Water leakage has become the main defect that affects the safe operation of shield tunnels in the saturated stratum. Long-term leakage is proven to change the load distribution and stress state of the tunnel lining, which hampers the structural performance of the tunnel. This paper proposes a novel numerical approach to simulate the localized leakage of segmental linings. The mechanical response of the longitudinal/circumferential joints is obtained by using a developed joint connection element, while the seepage response of the joints is simulated by implementing the DFLOW subroutine in Abaqus. The hydraulic boundary conditions are set at both longitudinal joints between segments and circumferential joints between rings. The hydromechanical behavior of the surrounding soil is incorporated based on the stress-pore water pressure interaction. A series of parametric numerical analyses is performed to explore the influences of partial leakage at the circumferential joints on the lining forces, lining deformation, and ground settlement. The simulation results demonstrate that the internal forces and maximum settlement of the tunnel structure and the magnitude of the ground settlement are substantially affected by the seepage rate, while the shear stiffness of the circumferential joints has only a slight effect. The longitudinal settlement of the tunnel and ground surface increase with the increase in the seepage rate of the circumferential joints, and a leakage-location-related distribution pattern is observed. The shear stiffness of circumferential joints mainly affects the pattern of the differential settlement of segmental linings in the longitudinal direction. These analyses indicate the appropriateness of such detailed three-dimensional simulations for capturing the realistic hydraulic and mechanical interactions of joint-leaked segmental linings.

Full-scale experimental study on failure characteristics of the key segment in shield tunnel with super-large cross-section

Due to the size effect and the change of joint design, the mechanical behavior of the shield tunnel with super-large cross-section is different from that of the conventional medium and large section tunnel. In addition, the mechanical and failure characteristics of the key segment are different from those of other segments in shield tunnels due to its unique shape and weaker stiffness. In this paper, a series of full-scale experiments were carried out to investigate the failure characteristics of the key segment in the shield tunnel with a super-large cross-section under general loading. The safety state of the whole structure was quantitatively evaluated based on the obtained bearing capacity, deformation characteristics, and progressive damage features. The testing procedure was introduced in detail, including the examined specimen, measurements, and loading conditions based on a revisit to the prototype. A multi-functional three-dimensional loading system was adopted to apply a compression-bending load similar to that in practice on the testing specimen. In-depth discussions were conducted on the displacement, joint opening, joint dislocation, and the failure characteristics of the segments directly recorded and observed during the tests. The results show that the longitudinal force acting along the tunnel axis significantly limits the inward convergence of segments, the opening of circumferential joints, and the dislocation of longitudinal and circumferential joints in a specific range. Under general loading conditions, when the load reaches the most unfavorable load combination, the testing segments are still in a safe state, whose deformation does not exceed the design requirements, and no damage occurs. After reaching the destructive load, distinct crack propagation behavior is found in different stages, which can be divided into four steps according to the observed distribution characteristics. The final failure of the segments begins with the collapse of the longitudinal joint compression zone. Additionally, the reverse shear circumferential joint is seriously damaged, whereas the forward shear circumferential joint is only slightly damaged. The results can provide novel insights into the failure characteristics of the key segment in the super-large cross-section tunnel.

A model for predicting the splitting bearing capacity of Fiber Reinforced Concrete elements under partially loaded areas

AbstractConcrete elements are frequently subjected to partially loaded areas; a typical example is represented by precast tunnel segments. In fact, during the excavation process, the hydraulic jacks of the boring machine exert, on the last assembled ring, high forces concentrated on small areas with respect to the size of ring joint. Similarly, when lining is embedded in ground, high hooping forces are transmitted through longitudinal joints, which present a contact zone smaller than the segment cross section. In both cases, spreading these loads into tunnel segments result in tensile transverse stresses which may cause splitting cracks. In the last decades, the growing desire to find more economic and sustainable solutions has driven enormous efforts in the tunnel industry to find new design solution such those based on Fiber Reinforced Concrete (FRC) or a combination of FRC and traditionally steel rebars. Research studies have already demonstrated the ability of fibers in controlling splitting crack phenomena. However, there is a lack of knowledge on reliable analytical approaches to quantify these benefits. The main aim of this paper is to develop a new model for determining the bearing capacity of FRC elements under partially loaded areas when splitting failure occurs. The analytical model herein reported allows a good prediction of the maximum loads exhibited by FRC prisms tested under high concentrated loads, whose data were selected from the literature.

Bending Performance of the Steel Longitudinal Joint for Quasi-Rectangular Pipe-Jacking Tunnels

Pipe jacking is a special tunneling method for installing underground pipelines or tunnels with the minimum surface disruption. Longitudinal pipe-to-pipe joints are important for tunnels with the pipe-jacking technique. The longitudinal joint generally adopts the socket type, that is, a bell-and-spigot joint, designed for use with gaskets work well for jacking. The joints should have sufficient bearing surfaces to transmit the required axial thrust and have the ability to resist lateral forces from ground movements during tunnel construction and operation. This paper focuses on the mechanical performance of the longitudinal joint of the superlarge cross section quasi-rectangular pipe-jacking tunnel under the action of local bending moments caused by lateral forces. A full-scale ultimate bending test of the local joint specimen was carried out to study its bearing mechanism, ultimate bearing capacity, and failure mode. Numerical simulations were then employed to analyze the performance of the joint specimen and were verified by the experimental results. The damage evolution process and bearing mechanism changes of the joint specimen were analyzed by numerical simulations. The results show that the bell part contributes much more to the bending of the joint than the spigot part. The bolt contributes little to the bearing capacity and stiffness of the joint but plays a role in positioning the pipe to pipe in the installation. The bending failure of the joint is characterized by weld fractures between the longitudinal rib and its flange next to the V-groove weld at the bottom of the bell part. The V-groove weld connecting the bottom of the spigot part and the bell part primarily affects the bending capacity of the joint.

Experimental investigation of seismic performance of shield tunnel under near-field ground motion

The near-field ground motion is one of the challenges to underground structure in soft soil site. In order to study seismic performance of shield tunnel under near-field ground motion, a series of large-scale shaking table tests are conducted. A refined tunnel lining is developed to capture the extension/closure response of joints. The difference of seismic response of shield tunnel under near field ground and far field ground motion is compared and analyzed. The findings show that compared with far-field ground motion, the acceleration response of segmental lining, cross-sectional deformation, extension/closure of longitudinal joints, dynamic normal earth pressure, and strain on segmental lining are increased obviously under the action of near-field ground motion. The near-field ground motion significantly stimulates the response of the tunnel structure in a wider low frequency range. The adverse effect of near-field ground motion on shield tunnel in soft soil site is significantly greater than that of far-field ground motion.

Influence of Longitudinal Joint Setting and Synchronous Cooling Zone on High Altitude Region’s Dam Construction

The crack problem in mass concrete is a difficult problem to thoroughly solve, especially for the crack of dam construction in high-altitude regions. High altitude regions have the fundamental features of a dry climate and strong solar radiation. When dam construction is performed under these special climate conditions, temperature control and crack prevention become more difficult problems. Based on the high altitude region’s dam construction conditions, the existing temperature control measures were optimized by combining the three-dimensional finite element method. The synchronous cooling zone’s temperature control technique is adopted to lower the temperature gradient in the dam’s height direction, coordinate the deformation of the upper and lower layers, and reduce mutual constraints between the upper and lower layers to further reduce the temperature stress. Calculation results show that the adoption of synchronous cooling zones and the set of longitudinal joints can effectively reduce mutual constraints, increase the safety factor, and prevent cracks. This method can be considered an important reference to dam projects in high-altitude regions.

Analytical approach for segmental tunnels considering nonlinear longitudinal joints in soft soils

As a discontinuous ring structure, joints are the weakness of a tunnel lining, which have a significant influence on the tunnel deformations and internal forces. Since the deformations at the joints are discontinuous, joint behaviors are treated as nonlinear rotational springs. Besides, the tunnel-soil interactions are modelled as a series of radial and circumferential nonlinear Winker springs. Thereafter, an analytical approach based on the beam-spring model is proposed. The reliability of this method is verified with three cases available in the literatures. It indicates that the proposed method is reasonable to estimate the tunnel deformations. Furthermore, parametric studies are carried out to reveal the influence of the coefficient of earth pressure at-rest, the soil stiffness and local surcharge loadings on the tunnel responses. It has been shown that increasing the coefficient of earth pressure and soil stiffness is beneficial for reducing tunnel convergences. Under the earth pressures, cracks are most likely to appear at the crown, waist, and bottom of the tunnel. For the metro tunnel in Shanghai, when the relative local surcharge loading is larger than 0.3 (the corresponding convergence is about 14‰D, D is the tunnel external diameter), joints subjected to the negative moment are susceptible to reaching the ultimate state.

Experimental study on deformational resilience of longitudinal joint in shield tunnel lining

Resilience is a functional attribute of shield tunnels to ensure continued serviceability. From the performance-based perspective, the concept of deformational resilience is proposed and defined as the ability to resist deformation development (robustness) and the ability to recover from pre-existing deformation (recoverability). This work aims to measure the deformational resilience of shield tunnel lining structure, targeting at its most vulnerable part—longitudinal joint. For this purpose, a series of full-scale tests are carried out to perform 1) the failure process to simulate external surcharge loads, 2) the recovery process to simulate the effects of unloading and tunnel bilateral soil grouting, and 3) the cyclic loading process to simulate incremental cycling loading and unloading conditions. The assessment of deformational resilience is based on joint opening from the tests and related structural energy analysis. The test results demonstrate that the capability of tunnel longitudinal joint to resist deformation deteriorates with increasing overload level, and the recovery efficiency of joint opening presents nonlinear degradation with the increase of pre-existing deformation. The deformational resilience of longitudinal joint revealed in this research can facilitate the selection of appropriate timing and optimal design of technical parameters related to recovery measures for over-deformed shield tunnels.

Reinforcement Analysis of an Old Multi-Beam Box Girder Based on a New Embedded Steel Plate (ESP) Strengthening Method.

Multi-beam box girder bridges have been applied widely throughout the world for many years. However, the cracking of longitudinal joints between the box girders always leads to reflective cracking of the bridge decks during the service period and thus finally affects the safety and durability of the actual bridges. An embedded steel plate (ESP) strengthening method was presented by introducing carbon-A/-B glue to reinforce the longitudinal joints of old multi-beam box girder bridges for this problem. In order to evaluate the feasibility of the proposed method for actual bridges, an old multi-beam box girder bridge was reinforced, and structural parameters including strain, frequency, and deflection were obtained by adopting field tests before and after strengthening. In addition, the corresponding finite element (FE) model of the background bridge was also set up using ANASYS 18.0 to analyze the strengthening process. Analysis results of the actual bridge and FE model indicate that structural stiffness and load lateral transferring performance between the box girders were enhanced after ESP strengthening. Therefore, this proposed strengthening method can be used to improve the mechanical performance of multi-beam box girder bridges and provide reference for such bridge reinforcement.

Effect of erosion void on segmental tunnel lining: 2D numerical investigation

The effects of erosion voids on the performance and safety of linings and longitudinal joints in the transverse tunnel section are investigated using the plane strain finite element method in this study. Erosion voids located at the shoulder, springline, haunch, and invert of the tunnel are considered. First, the effectiveness of the numerical model is examined by comparing the internal forces under full contact conditions against the results from previous studies. Then, a parametric study is conducted to investigate the effect of erosion voids on the internal forces of longitudinal joints and tunnel deformations in the transverse section. The sensitivities of burial depth, earth pressure coefficient, and rotation stiffness ratio of longitudinal joints on the response of segmental linings under the presence of erosion voids are also analyzed. The results show that erosion voids at the shoulder and springline of the tunnel can intensify the ovalisation of the tunnel, whereas the voids at haunch and invert can lead to remarkable settlement of the lining circle. Finally, the opening and deterioration of structural integrity of the longitudinal joints are assessed, and a simplified method for the evaluation of joint safety is introduced, which can provide insight into how the joint integrity is jeopardized under the presence of erosion voids.

Experimental Validation of a Double-Deck Track-Bridge System under Railway Traffic

This article describes the experimental and numerical evaluation of the dynamic behaviour of the Cascalheira bridge, located on the Northern Line of the Portuguese railway network. The bridge has a short span formed by two filler-beam half-decks, each one accommodating a railway track. The study includes the development of a finite element numerical model in ANSYS® software, as well as in situ dynamic characterization tests of the structure, namely ambient vibration tests, for the estimation of natural frequencies, modes shapes and damping coefficients, and a dynamic test under railway traffic, particularly for the passage of the Alfa Pendular train. The damping coefficients’ estimation was performed based on the Prony method, which proved effective in situations where the classical methods (e.g., decrement logarithm) tend to fail, particularly in the case of mode shapes with closed natural frequencies, as typically happens with the first vertical bending and torsion modes. The updating of the numerical model of the bridge was carried out using an iterative methodology based on a genetic algorithm, allowing an upgrade of the agreement between the numerical and experimental modal parameters. Particular attention was given to the characterization of the ballast degradation over the longitudinal joint between the two half-decks, given its influence in the global dynamic behavior of this type of double-deck bridges. Finally, the validation of the numerical model was performed by comparing the acceleration response of the structure under traffic actions, by means of numerical dynamic analyses considering vehicle-bridge interaction and including track irregularities, with the ones obtained by the dynamic test under traffic actions. The results of the calibrated numerical model showed a better agreement with the experimental results based on the accelerations evaluated in several measurement points located in both half-decks. In the validation process the vertical stiffness of the supports, as well as the degradation of the ballast located over the longitudinal joint between half-decks, was demonstrated to be relevant for the accuracy and effectiveness of the numerical models.

P129 Quantification of longitudinal joint and cartilaginous changes within ankles with haemophilia joint degeneration using MRI imaging

Abstract Background/Aims Haemophilia is an X-linked recessive genetic disorder characterised by episodes of spontaneous and traumatic intra-articular bleeding. 90% of bleeds are of musculoskeletal origin, with the ankle being most affected joint. Recurrent bleeding results in haemosiderin accumulation, linked to progressive, end-stage ankle haemarthropathy in adolescent and adult patients. Magnetic Resonance Imaging (MRI) is gold-standard for the evaluation of early soft tissue and cartilage changes in ankles with haemarthropathy. This study utilised MRI sequences to quantify longitudinal changes within the ankle joint, via changes in cartilage thickness (CT), subchondral thickness (ST) and joint space width (JS) over time. Methods Clinical T1 Sagittal MRI scans of HJD ankles were selected (N = 5). Each patient had a minimum of two MRI scans available, at least one year apart, to allow for comparison of longitudinal changes. All images were identity coded but fully anonymised. The earliest available and most recent MRI scan were measured in three slices (medial, lateral and middle slice) and at different points along the joint space (anterior, middle and posterior). Measurements taken were cartilage thickness on the talar dome (CT) and the distance between the subchondral bone of the tibial plafond and talar dome (ST). The joint space width (JS) was then determined by subtracting CT from ST. Results Chondral thickness measurements showed most reduction, particularly at the antero-lateral aspect (-0.4mm) compared to the antero-medial and middle sections, with -0.24mm and -0.34mm (Table 1). ST and JS reduction was predominantly seen in the anterior joint, with most reduction in antero-lateral joint (-1.13mm). The posterior joint showed minimal reduction in the postero-medial and middle sections, with the posterior-lateral joint space width increasing (0.2mm). Subchondral thickness and joint space measurements were variable and did not demonstrate linear change over time. Conclusion A systematic longitudinal decrease in cartilage thickness was seen in the antero-lateral and antero-medial aspect of the ankle joint. The antero-lateral aspect of the ankle showed the greatest reduction in joint space and cartilage thickness. This suggests that this area of the joint is likely to provide the best early indications of haemarthropathy when using MRI as a diagnostic tool. Disclosure M. Schaper: None. M. Sharrock: None. R.A. Wilkins: None. A.C. Redmond: None.

A comparative investigation between the beam spring method and the modified routine method in special‐section shield tunnels: A case study for quasi‐rectangular tunnels

AbstractThe modified routine modelling (MRM) and the beam spring modelling (BSM) are two of the classical design methods for circular shield tunnels, but a comparison between their applications in special‐section shield tunnels (SSSTs) has not yet been conducted. In this study, these two methods are investigated and compared specifically for the case of quasi‐rectangular shield tunnels (QRSTs). While the MRM gives acceptable results for axial force values, some critical bending moments in joint sections and segment sections can be overestimated or underestimated, not giving accurate values for design. It is demonstrated that the MRM cannot precisely predict the degree of bending moment transfer and convergence deformations of the studied SSST, and should only be used in preliminary design. On the other hand, deeper insights into the mechanical behaviour of the QRST lining structure can be gained through the analysis of the BSM. The staggered assembly pattern results in a bending moment transfer between rings and the relatively stiff area sustains the transferred moment from its neighbouring less stiff areas. For most of the longitudinal joints, 20% to 40% of bending moment is redistributed to its neighbouring segments. The transfer increases the non‐symmetric distribution of bending moments in the two halves of a QRST lining ring. This characteristic does not exist in a traditional circular shield tunnel but needs due attention to the types of shield tunnels with two compartments in one tube. Finally, the influences of different parameters related to the assumed pressures and soil reactions are discussed.

An analysis model accounting for time-dependent shear lag effects in assembled composite bridge decks

The concrete deck of steel-concrete composite bridges made via prefabricated construction consists of precast slabs and construction joints between the slabs. When the age difference between the longitudinal joint concrete and precast slab concrete (new-old concrete) across a beam section is considered, the time-dependent characteristic of the assembled deck is different from that of the whole prefabricated deck. Based on the virtual work principle, differential equations were established to analyse the influence of the time-dependent characteristics of new-old concrete across a beam section on the shear lag effect of the composite beams. The analysis of examples showed that the proposed model was more accurate than the traditional model, which ignores the concrete age difference across a beam section, especially when analysing the long-term stress of joint concrete. The long-term stress of the joint concrete obtained by the proposed model decreased faster than that obtained by the traditional model with time, which increased the non-uniformity of the distribution of stress along the concrete flange. Overall, the proposed model could reasonably forecast the long-term performance of composite beams with assembled decks, which is beneficial to the life-cycle design and service behaviour analysis of composite bridges.

Beyond Performative Compliance: Local Forms of Resistance to Anti-FGM Campaigns in Ethiopia

Abstract The Afar region, one of the hot spots of female genital mutilation (FGM) in Ethiopia and the Horn of Africa, has attracted several international and local anti-FGM campaigns including the longitudinal global UNFPA-UNICEF joint initiative. The region is often praised as a showcase for the acclaimed social norm change brought by intervention projects. Religious leaders and traditional birth attendants (TBAs) were among the key local actors targeted as agents of change and norm mediators. The declaration passed by the religious leaders outlawing FGM, and the numerous community public declarations made all applauded the success in social norm change. Such accounts are often in tune with a narrative of linear progress of norms whereby global norms of gender equality successfully diffuse to local settings. The discourse pronouncing the diffusion of global norms often overshadows the norm contestations and resistance happening at the grassroots level. Based on an ethnographic study conducted in the Afar region, this contribution examines the different aspects of norm contestation and resistance happening at the grassroots level throwing light onto the resurgence of FGM in the region where the practice continued beyond the observational gaze of the government and other stakeholders. Furthermore, the article discusses the discursive strategies that the local community adopted ranging from performative compliance, negotiation for a milder form of the practice to devising alternative ways and platforms for performing FGM. The article critically reflects on the direct and subtle forms of resistance, the framing of the debate and the interplay of several factors that undermined the efficiency of the interventions.