Longitudinal Joints Research Articles

Deformational responses of operated shield tunnel to extreme surcharge: a case study

A field case of operated shield tunnel disrupted by unexpected extreme surcharge in Shanghai is reported in this paper. The deformational responses of segmental lining, in terms of convergences, settlements and joint open width, are highlighted. The surcharge caused by unexpected dumped soils with a maximum height of 7 m is six times larger than the design value of surcharge. Three hundred and sixty segmental lining rings of the operated metro shield tunnel below this surcharge are severely affected. The measured horizontal convergence to outer-diameter ratio (ΔD/Dout) ranges from 16.6 to 35.7‰, which is far beyond the averaged value for normal condition, i.e. 5.1‰. The trend of tunnel deformation (e.g. horizontal convergence and settlement) varying with surcharge level is found to be significantly non-linear. Correspondingly, the longitudinal joints are also severely disrupted and have large open widths. The rubber packer for joint near-tunnel springline loses its function of waterproof due to the release of 6 mm pre-compressive deformation. The majority of steel bolts of joint near-tunnel crown have passed yield state, while some are fractured. However, the circumferential joints are found to be in a sound workability.

Numerical simulation of soft longitudinal joints in concrete-faced rockfill dam

In the construction of high concrete-faced rockfill dams (CFRDs), soft filler is used in the longitudinal joints in order to avoid extrusion damage to the concrete face slab. In this paper, we consider the soft joint contact as an equivalent contact interface to avoid introducing conventional elements. Based on the introduction of a general transformation to obtain fully decoupled contact constraints, a new generalized node-to-segment formulation is developed to solve the multi-body contact problem in CFRDs. The high CFRD of Tianshengqiao-1 in China is numerically analyzed; the results show that soft joints can significantly reduce the axial stress of face slabs.

Reliability Analysis of Temperature Influence on Stresses in Rigid Pavement Made from Recycled Materials

Complex statistical and sensitivity analysis of principal stresses in concrete slabs of the real type of rigid pavement made from recycled materials is performed. The pavement is dominantly loaded by the temperature field acting on the upper and lower surface of concrete slabs. The computational model of the pavement is designed as a spatial (3D) model, is based on a nonlinear variant of the finite element method that respects the structural nonlinearity, enables to model different arrangement of joints, and the entire model can be loaded by thermal load. Four concrete slabs separated by transverse and longitudinal joints and the additional structural layers including soil to the depth of about 3 m are modeled. The thickness of individual layers, physical and mechanical properties of materials, characteristics of joints, and the temperature of the upper and lower surface of slabs are supposed to be random variables. The simulation technique Updated Latin Hypercube Sampling with 20 simulations is used for the reliability analysis. As results of statistical analysis, the estimates of basic statistics of the principal stresses σ1 and σ3 in 106 points on the upper and lower surface of slabs are obtained. For sensitivity analysis the sensitivity coefficient based on the Spearman rank correlation coefficient is used. As results of sensitivity analysis, the estimates of influence of random variability of individual input variables on the random variability of principal stresses σ1 and σ3 are obtained.

Use of Longitudinal Expansion Joints in Wide-Bridge Applications to Reduce Deck Cracking

AbstractIt is a very common practice to use longitudinal expansion joints to create dual-direction bridges in applications that would have otherwise resulted in bridges that are very wide. Unfortunately, the introduced longitudinal expansion joint can result in deterioration similar to that resulting from using transverse joints at bridge abutments and piers. The reason that longitudinal expansion joints are used in wide bridges is related to concerns about deck cracking resulting from constrained expansion and contraction. The main objective of this research was to evaluate the need for longitudinal expansion joints by assessing the relationship between bridge width (and other factors) and the propensity for deck cracking. To achieve this objective, an integral abutment bridge was selected to conduct live-load and thermal-load testing to provide field testing data for the calibration of a three-dimensional (3D) finite-element model (FEM) that would be used for a comprehensive parametric study. A combinat...

Slot stitching for longitudinal joint separation repairs

Lane separations at longitudinal joints not only allow water to infiltrate into layers under the concrete slabs and deteriorate slab support, but degrade load transfer efficiency (LTE) along longitudinal joints, resulting in an increase in load-related stresses in concrete slabs and poor performance of pavement. Slot stitching provides one of the more efficient methods to restore pavement structural capacity due to lane separations. In 2010, three slot stitching design configurations were implemented on US-75 in Sherman, Texas, which experienced lane separations as well as faulting along the longitudinal construction joint. After the dowel bars were installed, the ultra rapid repair method with the use of high early strength, low shrinkage, and low coefficient of thermal expansion (CoTE) backfill materials was utilized to minimize the traffic interruption and to restore the elevation. For measuring the effectiveness of the repair method, LTE at longitudinal joints was evaluated using Falling Weight Deflectometer (FWD). Testing results in this paper demonstrate the effect of slot stitching design, or more specifically the number of slot stitching in a slab and/or bar size, on improving LTE by providing before-and-after LTE measurements and detailed material information. In particular, the design configuration with 5 #8 bars (25.4-mm diameter) was the most cost-effective and efficient, with about 28% improvement in LTE after more than 4years of service. Moreover, three design configurations with the use of low-shrinkage, low-CoTE backfill materials were demonstrated to improve LTE substantially, with an average increase from 45% to 74%.

Immediate effects of modified landing pattern on a probabilistic tibial stress fracture model in runners

BackgroundTibial stress fracture is a common injury in runners. This condition has been associated with increased impact loading. Since vertical loading rates are related to the landing pattern, many heelstrike runners attempt to modify their footfalls for a lower risk of tibial stress fracture. Such effect of modified landing pattern remains unknown. This study examined the immediate effects of landing pattern modification on the probability of tibial stress fracture. MethodsFourteen experienced heelstrike runners ran on an instrumented treadmill and they were given augmented feedback for landing pattern switch. We measured their running kinematics and kinetics during different landing patterns. Ankle joint contact force and peak tibial strains were estimated using computational models. We used an established mathematical model to determine the effect of landing pattern on stress fracture probability. FindingsHeelstrike runners experienced greater impact loading immediately after landing pattern switch (P<0.004). There was an increase in the longitudinal ankle joint contact force when they landed with forefoot (P=0.003). However, there was no significant difference in both peak tibial strains and the risk of tibial stress fracture in runners with different landing patterns (P>0.986). InterpretationImmediate transitioning of the landing pattern in heelstrike runners may not offer timely protection against tibial stress fracture, despite a reduction of impact loading. Long-term effects of landing pattern switch remains unknown.

Clinical Presentation, Surgical Treatment, and Outcome in Radial Polydactyly.

Radial polydactyly or 'thumb duplication' is the most common congenital upper limb anomaly ('CULA') affecting the thumb. The clinical presentation is highly diverse, ranging from an extra thumb floating on a skin bridge to complicated thumb triplications with triphalangeal, deviating, and hypoplastic components. Radial polydactyly can be classified into one of 7 osseous presentations using the Wassel classification, with type IV (45%), type II (20%), and type VII (15%) occurring most frequently. When faced with a radial polydactyly case, hand surgeons specialised in congenital anomalies must weigh the preoperative functional potential and degree of hypoplasia of both thumbs in order to decide whether to resect one thumb and reconstruct the other ('resection and reconstruction'), excise a central part of both thumbs and unite the lateral tissues into one thumb ('the Bilhaut procedure'), transfer the better-developed distal tissues of one thumb onto the better-developed proximal tissues of the other ('on-top plasty'), or discard both severely hypoplastic thumbs and pollicise the index finger. Mere excision of the hypoplastic thumb is rarely indicated since it often requires subsequent revision surgery. Even after being treated by experienced surgeons, about 15% of patients with polydactyly will need additional procedures to correct residual and/or new problems such as deviation from the longitudinal axis and joint instability. Nevertheless, radial polydactyly patients usually achieve unimpaired everyday hand function postoperatively.

Sensitivity-to-change and validity of semi-automatic joint space width measurements in hand osteoarthritis: a follow-up study

To assess sensitivity-to-change and validity of longitudinal quantitative semi-automatic joint space width (JSW) measurements and to compare this method with semi-quantitative joint space narrowing (JSN) scoring in hand osteoarthritis (OA) patients. Baseline and 2-year follow-up radiographs of 56 hand OA patients (mean age 62 years, 86% women) were used. JSN was scored 0-3 using the Osteoarthritis Research Society International atlas and JSW was quantified in millimetres (mm) in the second to fifth distal, proximal interphalangeal and metacarpal joints (DIPJs, PIPJs, MCPJs). Sensitivity-to-change was evaluated by calculating Standardized Response Means (SRMs). Change in JSW or JSN above the Smallest Detectable Difference (SDD) defined progression on joint level. To assess construct validity, progressed joints were compared by cross-tabulation and by associating baseline ultrasound variables with progression (using generalized estimating equations, adjusting for age and sex). The JSW method detected statistically significant mean changes over 2.6 years (-0.027mm (95%CI -0.01; -0.04), -0.024mm (-0.01; -0.03), -0.021mm (-0.01; -0.03) for DIPJs, PIPJs, MCPJs, respectively). Sensitivity-to-change was low (SRMs: 0.174, 0.168, 0.211, respectively). 9.1% (121/1336) of joints progressed in JSW, but 3.6% (48/1336) widened. 83 (6.2%) joints progressed in JSW only, 36 (2.7%) in JSN only and 37 (2.8%) in both methods. Progression in JSW showed weaker associations with baseline inflammatory ultrasound features than progression in JSN. Assessment of progression in hand OA defined by JSW measurements is possible, but performs less well than progression defined by JSN scoring. Therefore, the value of JSW measurements in hand OA clinical trials remains questionable.

Specification Limits and Pay Adjustment for Longitudinal Joint Density of Asphalt Pavements: Case Study in New Jersey

This paper summarizes a case study on developing specification limits and pay adjustments for the longitudinal joint density of asphalt pavements. The existing joint density specifications used by various agencies first were reviewed for the minimum joint density requirements and the corresponding pay adjustments. Laboratory tests were conducted to measure air voids of field cores taken from selected field projects with the saturated surface dry method (AASHTO T 166) and the automatic vacuum-sealing method (AASHTO T 331). Permeability measurements were conducted with a falling-head permeability device. The air voids at the joint were found to be 1.5% to 2% greater than the air voids at the mats adjacent to the joint. For conditions specific to New Jersey, individual testing of the theoretical maximum density of the cores taken at the joint is recommended because of the existence of joint adhesive. The upper limits for air voids at the longitudinal joint are recommended to be 9% for stone matrix asphalt and 10% for hot-mix asphalt, on the basis of the permeability criterion of 150 × 10−5 cm/s reported in previous studies. Furthermore, alternative pay equations for air voids at the longitudinal joint were proposed, with different triggers for retest and for rejectable quality level. A SpecRisk analysis was conducted to confirm that the effective acceptable quality level coincided with the stated acceptable quality level and that the acceptance procedures properly awarded 100% payment at the stated acceptable quality level. The study led to a draft quality assurance specification for longitudinal joint density that was proposed for future implementation.

Effect of Boundary Conditions in Segmental Lining Model on its Sectional Force

Nowadays, underground construction becomes popular as the demand for infrastructure in urban areas increases. To develop underground space in an urban area, it is important to investigate ground surface settlement and damage to existing neighbouring structures. Consequently, 3D finite element method (FEM) continuum models have been developed. This paper introduces a 3D FEM continuum model, which can consider, longitudinal joints, circumferential joints, and nontension boundary between lining and ground, and examines the effect of boundary condition at the tunnel end and ground stiffness on the lining behavior (i.e., bending moment, axial force, normal effective earth pressure, and segment displacement) in the case of staggered building. As a result, it was found that the boundary condition at the tunnel end does not significantly affect the sectional force, except for the axial force in the case of soft soil; The two-ring model provides the safe side results from the viewpoint of segment design; and it can be adopted for segmental lining design and lining behavior simulation.

Joint Detailing Between Double Tee Bridge Girders for Improved Serviceability and Strength

Precast, prestressed double tee bridge girders are widely used for accelerated bridge construction on local roads in South Dakota. A common issue among double tee bridges in South Dakota is the rapid deterioration of longitudinal joints (shear keyways) between adjacent girders. Deteriorated joints allow moisture and deicing chemicals to reach the deck reinforcement, which leads to premature corrosion of reinforcing steel and spalling of concrete. The structural performance of conventional and proposed longitudinal joints between precast double tee bridge girders was examined experimentally under cyclic and monotonic loading. The proposed continuous joint with overlapping steel mesh reinforcement in a grouted shear keyway exhibited serviceability and strength performance characteristics substantially improved over those of the conventional grouted joint with discrete welded connections.

Visualization of Damages of the Main Pipelines Using Cyclic Hydro Testing

The fracture of the pipelines is often occurred in the vicinity of weld joints. It is important to consider the scattered damages in the bulk material and their effect on the mechanical properties. These damages could be visualized by hydro testing of long-term exploited pipes with following fractography investigation of the obtained fracture surfaces. The bulk damages of 10G2C1 steel after 45 years of operation on the pipeline were analyzed using mechanical characteristics of metal and fractography features of fracture. Strength and ductility characteristics, impact toughness of the exploited steel (as a base metal) and metal from different zones of longitudinal weld joint on the pipe were analyzed.

Static and fatigue experimental tests on a full scale fuselage panel and FEM analyses

A fatigue test on a full scale panel with complex loading condition and geometry configuration has been carried out using a triaxial test machine. The demonstrator is made up of two skins which are linked by a transversal butt-joint, parallel to the stringer direction. A fatigue load was applied in the direction normal to the longitudinal joint, while a constant load was applied in the longitudinal joint direction. The test panel was instrumented with strain gages and previously quasi-static tests were conducted to ensure a proper load transferring to the panel. In order to support the tests, geometric nonlinear shell finite element analyses were conducted to predict strain and stress distributions. The demonstrator broke up after about 177000 cycles. Subsequently, a finite element analysis (FEA) was carried out in order to correlate failure events; due to the biaxial nature of the fatigue loads, Sines criterion was used. The analysis was performed taking into account the different materials by which the panel is composed. The numerical results show a good correlation with experimental data, successfully predicting failure locations on the panel.

A Robust System for Longitudinal Knee Joint Edema and Blood Flow Assessment Based on Vector Bioimpedance Measurements.

We present a robust vector bioimpedance measurement system for longitudinal knee joint health assessment, capable of acquiring high resolution static (slowly varying over the course of hours to days) and dynamic (rapidly varying on the order of milli-seconds) bioresistance and bioreactance signals. Occupying an area of 78×90 mm(2) and consuming 0.25 W when supplied with ±5 V, the front-end achieves a dynamic range of 345 Ω and noise floor of 0.018 mΩrms (resistive) and 0.055 mΩrms (reactive) within a bandwidth of 0.1-20 Hz. A microcontroller allows real-time calibration to minimize errors due to environmental variability (e.g., temperature) that can be experienced outside of lab environments, and enables data storage on a micro secure digital card. The acquired signals are then processed using customized physiology-driven algorithms to extract musculoskeletal (edema) and cardiovascular (local blood volume pulse) features from the knee joint. In a feasibility study, we found statistically significant differences between the injured and contralateral static knee impedance measures for two subjects with recent unilateral knee injury compared to seven controls. Specifically, the impedance was lower for the injured knees, supporting the physiological expectations for increased edema and damaged cell membranes. In a second feasibility study, we demonstrate the sensitivity of the dynamic impedance measures with a cold-pressor test, with a 20 mΩ decrease in the pulsatile resistance associated with increased downstream peripheral vascular resistance. The proposed system will serve as a foundation for future efforts aimed at quantifying joint health status continuously during normal daily life.

Flexural Behavior and Strut-and-tie Model of Joints with headed bar details Connecting Precast Members

Summary This paper focuses on an investigation of an improved longitudinal joint with headed bar details connecting precast decked bulb tee girders for accelerated bridge construction. The testing study included two phases. In phase I, five beam specimens with various headed bar details and a continuous reinforced specimen were tested under flexure loadings. A headed bar detail with 152 mm lap length was recommended for further study. In phase II, two slabs connected by the selected joint were tested under flexure and flexure-shear loadings. Test results were evaluated based on structural behaviors including capacity, deflection, and failure mode. At last, a validated strut-and-tie model was developed to anticipate the capacity of the improved longitudinal joint. It shows that the proposed headed bar details can provide a continuous force transfer in the joint. The lap length interacting with the spacing of the headed bar is the most significant parameter of the improved joint details. To develop a full strength joint, the lap length should not be less than 152 mm and be designed by the strength requirement. The strut-and-tie model can provide a conservative strength anticipation of the joint and it is the lower bound of the ultimate capacity of the joint.

Estimation of Joint and Interface Parameters for the Finite Element Analysis of Jointed Concrete Pavement Using Structural Evaluation Results

Abstract In the analysis of jointed concrete pavement, it is necessary to appropriately model certain aspects of the pavement for accurate estimation of its structural responses. These include load transfer at joints (doweled and aggregate interlocked) and interface condition between slab and foundation. This paper presents a backcalculation method for estimating the joint parameters, both transverse and longitudinal, and the interface parameter along with the pavement layer moduli by using the results of structural evaluation of an in-service concrete pavement. The details of the structural evaluation using Falling Weight Deflectometer (FWD) and the two-stage backcalculation procedure using a three-dimensional finite element (FE) model for jointed concrete pavement are discussed. Modulus of dowel support and modulus of interlocking joints are the transverse and longitudinal joint parameters respectively and the coefficient of friction between concrete slab and foundation is the interface parameter considered for the analysis. These parameters are the useful inputs in modeling jointed concrete pavement using finite element method.

Microstructural investigations for laser welded joints of Ti–22Al–25Nb alloy sheets upon large deformation at elevated temperature

In order to provide reference for the gas forming of Ti–22Al–25Nb alloy tube blanks with a laser beam welded joint, microstructure and tensile deformation behavior of the alloy with a joint were investigated using uniaxial tensile tests at 990°C, with a tensile speed of 0.016mm/s. Both of the samples with a longitudinal joint and a transverse joint were applied in the tensile tests. The longitudinal joint samples showed a better high temperature deformability than the transverse joint ones, which partly attributed to the decrease of α2-phase grains along the β/B2-phase grain boundaries and more dynamic recovery and discontinuous dynamic recrystallization in the longitudinal joint. These results indicated that the laser welded joint could experience a large deformation at a proper temperature and strain rate, which was a potential method for the preparation of tube blanks for gas forming components.

EXPERIMENTAL EVALUATION OF MISALIGNED TIE BAR EFFECTS ON PCC PAVEMENT LONGITUDINAL JOINTS

Jointed Portland cement concrete (PCC) pavements are widely used for roadways construction. Inspection of PCC pavements revealed that it is common for tie bars across pavement longitudinal joints to be misaligned. A misaligned tie bar could inhibit the tie bars ability to provide load transfer across the joint and to prevent excessive joint opening. An experimental research study was performed to determine the effect of misaligned tie bars on the performance of pavement longitudinal joints. The experimental program consisted of testing 35 slab specimens that represented pavement sections with one tie bar placed across a joint. The test matrix included aligned tie bar configuration and four different misalignment configurations. Specimens with aligned tie bar configuration served as control specimens. The misaligned tie bar cases were vertical translation, vertical skew, longitudinal translation, and horizontal translation. For each misalignment configuration, four different misalignment magnitudes were investigated. The experimental results showed that tie bars with vertical translation, vertical skew, and longitudinal translation had negligible effects on the performance of the longitudinal joint. However, tie bars with horizontal skew resulted in reduced joint performance when compared to the aligned tie bar case.

Extensional fold-related fracturing in the Armeña rollover (Cotiella Massif, Southern Pyrenees)

The Cotiella Upper Cretaceous Basins in the central southern Pyrenees host an outstandingly exposed extensional fault system and related folds which developed by the extensional gravitational collapse of the post-rift carbonate platform above relic Upper Triassic salt at the southern margin of the Bay of Biscay-Pyrenean rift system.Among the Cotiella extensional structures, the Armena rollover involves more than 3 km of middle Coniacian to lower Santonian wedge-shaped syn-kinematic sediments which are overlying upper Albian to lower Coniacian pre-kinematic strata detached above an Upper Triassic salt layer. Although the rollover was partially inverted during the Pyrenean orogeny, its first order extensional architecture and the associated syn-extensional fracture pattern are well preserved.Both the hanging-wall and foot-wall of the NE-dipping Armena fault exposes two sets of bed-perpendicular joints which oriented about parallel (longitudinal) and perpendicular (transverse) to the fault, respectively. Spatial distribution and reactivation pattern of longitudinal joints indicate their early to syn-folding origin, where widespread longitudinal jointing occurred firstly as part of the regional extensional framework, affecting the entire rock volume with a rather constant density. Later, laterally decreasing fault-propagation rate caused the development of a hanging-wall syncline, preferentially developed at the lateral termination of the rollover.There, folding of strata above the slowly propagating fault's tip was ensured by development of further longitudinal joints that underwent shearing during the later stage of fault-propagation.

Development and study of deck joints in prefabricated concrete bulb-tee bridge girders: Conceptual design

Speed of construction, particularly for bridge replacement and repair projects, has become a critical issue to minimize disruption of traffic and commerce. A promising system for rapid construction is a precast bridge system using decked bulb tee prestressed concrete girders. This type of bridge includes manufacturing the bridge deck precast and pretensioned with the girder in the precast plant under controlled environment. Then, the precast girders are transported to the construction site, and placed over the abutments and piers beside each other with flanges of adjacent girders field connected. Load transfer between adjacent girders is provided by longitudinal joints parallel to traffic direction. This paper presents a new bridge deck slab flange-to-flange connection system for precast Deck Bulb Tee (DBT) girders. The objectives of this study were to develop moment-transferred and intermittent-bolted connections for DBT bridge girders in view of the ultimate strength of the connection system. Two types of moment-transferring connection and two types of intermittent-bolted connection were developed. The paper presents design procedure of the developed joints based on available design equations in North American design codes for bridges and structures as well as related design equations available in the literature. The developed joint was considered successful if the theoretical resistance satisfied the requirements specified in North American Bridge Codes. Comparison between the theoretical findings and the available experimental failure loaded of actual-size bridge deck specimens simulating the developed connection justified the proposed theoretical design procedure.