Materials Approach to Improving Asphalt Pavement Longitudinal Joint Performance

Many states are looking for methods to improve longitudinal joint performance of their asphalt pavements, since these joints often fail before the rest of the surface. With their inherently lower density, longitudinal joints fail by cracking, raveling, and potholing because of the intrusion of air and water. Because of their longitudinal joint issues, and after trying several less-than-successful traditional solutions, Illinois Department of Transportation (IDOT) developed a concept to seal the longitudinal joint region, but from the bottom up. Test sections were constructed in 2001 through 2003 to determine how a newly developed material, called longitudinal joint sealant (LJS), would improve joint performance. LJS is a highly polymer-modified asphalt cement with fillers and is placed at the location of a longitudinal joint before paving. As mix is paved over it, the LJS melts and migrates up into voids in the low-density mix, making the mix impermeable to moisture while sealing the longitudinal joint itself. The IDOT test pavements were evaluated after 12 years and found to have longitudinal joints that exhibited significantly better performance than the control joint sections and were in similar or better condition than the rest of the pavement. Laboratory testing of cores showed decreased permeability and increased crack resistance of mix near joints with LJS as compared with similar mix without LJS. The life extension of the joint area is approximately 3–5 years, and the benefit is calculated to be three to five times the initial cost.

Preliminary Design for Segmental Joint of Precast Tunnel Liner

Responses of the segmental tunnel liner to external forces are primarily dependent on complicated interactions among construction process, soil structural interactions, segmental (longitudinal) joint characteristic etc. However, most proposed liner’s design procedures and recommendations are basically empirical and experience based, especially when the roles of tunnel joint are concerned. In the present study, a preliminary design calculation for the segmental joint with consideration of three practical conditions was proposed. The method adopts two main assumptions; the stiffness reduction factor and simplified pre-stressed concrete blocks, so that the flexural capacity of the segmental joint and its interactions to the main reinforced concrete segment body can be designated. Calculation examples are given for three most probable cases, namely, 1) the unbolted joint without joint opening, 2) the bolted joint without joint opening and 3) the unbolted segmental joint with allowing joint opening. Based on these calculations, the required compressive strength of concrete, thickness of liner, steel reinforcement, bolts and number of segments of the liner could be specified. The proposed method could well provide an engineer a tool to determine the initial joint configuration and its interaction to the overall tunnel lining.

Prototype Experimental Investigation of the Failure Mechanism and Crack Propagation of Segment Lining for Staggered Jointed Assembly

In order to ascertain the failure characteristics of a segment structure with distributed mortises and tenons, one should be aware of the rules of key parameters and the development of cracks during the failure process. In this paper, based on the Foguan-Guangcheng Intercity Railway Tunnel Project, a prototype test of the structure of a segment with a staggered joint assembly was performed to study the local mechanical characteristics of the segment lining of the vault. The main conclusions were as follows: (1) The failure process in the test was classified as large eccentric compression failure, and the bearing capacity limit was M = 1993 kN m. (2) The overall displacement distribution of the segment structure was funnel-shaped, and the failure process was divided into three stages, that is, the elastic stage, the elastoplastic stage, and the plastic stage. Thus, it is recommended that the index of the single-point displacement limit of this tunnel be reduced appropriately to be between 1.5 and 1.8%. (3) The change rule of the longitudinal joint opening of the segment can be divided into three stages, that is, slow increase, accelerated increase, and sharp increase. For normal use, the limit of the opening of the longitudinal joint is set at 3 mm. (4) The width of the structural crack and the vertical displacement of the control section can be used as the safety evaluation index of this project. When either a large increase in the width of the crack occurs or the displacement specified above is reached, it can be considered that the structure is about to fail, and immediate protective measures must be taken.

Penalized longitudinal mixed models with latent group structure, with an application in neurodegenerative diseases

SummaryLarge-scale longitudinal data are often heterogeneous, spanning latent subgroups such as disease subtypes. In this paper, we present an approach called longitudinal joint cluster regression (LJCR) for penalized mixed modelling in the latent group setting. LJCR captures latent group structure via a mixture model that includes both the multivariate distribution of the covariates and a regression model for the response. The longitudinal dynamics of each individual are modeled using a random effect intercept and slope model. Inference is done via a profile likelihood approach that can handle high-dimensional covariates via ridge penalization. LJCR is motivated by questions in neurodegenerative disease research, where latent subgroups may reflect heterogeneity with respect to disease presentation, progression and diverse subject-specific factors. We study the performance of LJCR in the context of two longitudinal datasets: a simulation study and a study of amyotrophic lateral sclerosis (ALS). LJCR allows prediction of progression as well as identification of subgroups and subgroup-specific model parameters.

Analysis of Longitudinal Timber Beam Joints Loaded with Simple Bending

The joints in timber structures are often the decisive factor in determining the load-bearing capacity, rigidity, sustainability, and durability of timber structures. Compared with the fasteners used for steel and concrete structures, fasteners for timber structures generally have a lower load-bearing capacity and rigidity, with the exception of glued joints. Glued joints in timber structures constitute a diverse group of rigid joints which are distinguished by sudden failure when the joint’s load-bearing capacity is reached. In this contribution, the load-bearing capacity of a longitudinal joint for a beam under simple flexural stress is analyzed using glued, double-sided splices. Joints with double-sided splices and connecting screws were also tested to compare the load-bearing capacity and rigidity. A third series of tests was carried out on joints made using glued double-sided splices augmented with screws. The aim of this combined joint was to ensure greater ductility after the load-bearing capacity of the glued splice joint had been reached.

Full-Scale Evaluation of an Innovative Joint Design between Adjacent Box Beams

The longitudinal joints on adjacent precast, prestressed box beams used in bridge construction are vulnerable to cracking. These cracks provide a direct path for water and deleterious agents to enter the structural system, causing corrosion of the embedded steel bars and tendons. To avoid significant maintenance costs, safety concerns, or both, an innovative longitudinal joint between two adjacent box beams was designed in the current study. This joint is 6½ in. wide with roughened surfaces, filled with shrinkage compensating concrete and reinforced by steel bars. The joint was evaluated on a small-scale basis and satisfactory performance was obtained in resisting early-age cracks. In the current paper, the joint design is further evaluated through experiments on a 31 ft long specimen during the joint’s early age, and when it is subjected to multiple levels of cyclic loads. A finite element (FE) model that is capable of simulating the early-age concrete hardening was also developed and validated against the experimental data. The early-age, time-dependent stress development in the joint and at the interface of the joint and box beam was investigated using the FE model. Based on the results of laboratory tests and FE simulations, the innovative joint was found to remain crack free without the utilization of a shear key or transverse post-tensioning. The “compression-dominate” joint created by the expansive joint material and transverse reinforcing bars across the interface is expected to address the issues associated with early age, while ensuring the long-term durability and performance of box-beam bridges.

Trajectory of body mass and skeletal muscle indices and disease progression in metastatic colorectal cancer patients

ABSTRACT Background Knowledge of the evolution of BMI and skeletal muscle index (SMI) measurements during advanced cancer and their relationships with disease progression (PD) is relevant to improve the timing of interventions that may improve cachexia-associated outcomes. Objectives We investigated BMI and SMI trajectories and their associations with PD in metastatic colorectal cancer (mCRC) patients during consecutive palliative systemic regimens. Methods In a secondary analysis of the primary CAIRO3 trial, we included 533 mCRC patients with BMI measurements repeated every 3 wk and 95 randomly selected patients with SMI measurements repeated every 9 wk. We studied 2 periods: p1, during first-line maintenance capecitabine + bevacizumab or observation until the first progression of disease (PD1); and p2, during capecitabine + oxaliplatin + bevacizumab or another reintroduction treatment from PD1 until the second progression of disease (PD2). BMI and SMI trajectories were modeled separately throughout both periods, and joint longitudinal-survival modeling was used to investigate the relationships between slopes in BMI and SMI with PD at 9 and 3 wk pre-PD. A multivariate longitudinal joint model was used to investigate the association between the BMI trajectory and PD at time of PD, independent of SMI. Results During p1, the slopes in BMI and SMI were associated with early PD1 [HRs for 9-wk BMI: 1.54 (95% CI: 1.33, 1.76); 9-wk SMI: 1.38 (95% CI: 0.87, 1.89), NS; 3-wk BMI: 1.74 (95% CI: 1.48, 1.99); 3-wk SMI: 2.65 (95% CI: 1.97, 3.32)]. During p2, only the slope in SMI was related to PD2 [9-wk BMI: 1.09 (95%: CI: 0.73, 1.45), NS; 9-wk SMI: 1.64 (95% CI: 1.25, 2.04); 3-wk BMI: 1.17 (95% CI: 0.77, 1.57); 3-wk SMI: 1.11 (95% CI: 0.70, 1.53)]. In models mutually adjusting for BMI and SMI, SMI was associated with PD in p1 [p1 ( n = 95), HR BMI: 1.32 (95% CI: 0.74, 2.39), NS; p1, HR SMI: 1.50 (95% CI: 1.04, 2.14); p2 ( n = 50), BMI: 0.98 (95% CI: 0.55, 1.75), NS; p2, HR SMI: 1.11 (95% CI: 0.61, 2.05), NS]. Conclusions In mCRC patients during palliative systemic treatment, SMI losses, irrespective of BMI losses, may be a marker for the early initiation of cachexia interventions.