In this paper, typical rail bridges on various New Jersey rail lines were reviewed to investigate the impact of the increased railcar weight on the bridges. Based on the field inspections, a number of critical bridges on New Jersey’s rail lines were selected and load-rated based on the current American Railway Engineering and Maintenance-of-Way Association (AREMA) specifications as well as the team analytical studies. Two-Dimensional (2D) dynamic models and field instrumentation and testing were adopted for the more accurate assessment of these bridges and to develop a refined methodology for evaluating and load-rating railroad bridges. The field study included instrumentation and testing under live loads (moving freight and passenger railcars). The steel bridge is simulated as a Bernoulli-Euler beam and the moving train is modeled using rigid-body dynamics method. Modal superposition method is adopted to compute the dynamic interaction of the train-bridge system. The dynamic model was validated with results from the field tests. Using this model, the impact factor for a typical steel plate girder bridge for different speeds of the train was determined. The results show that the present AREMA code has a tendency to overestimate the impact factor for these bridges at normal operating speed.

Articular cartilage covers the articulating bones within synovial joints. It provides a bearing surface with low friction and wear properties. Although cartilage can function effectively for decades, it has limited ability to repair itself. Damage to articular cartilage is linked to degenerative diseases like Osteoarthritis (OA), which is a leading cause of disability in the United States. While severe cases of OA may be treated with a total joint replacement, tissue engineered (TE) cartilage is now emerging as a potential alternative treatment. TE constructs must function in the highly loaded environment of diarthrodial joints for many years. We have been investigating the mechanical behavior of tissue-engineered cartilage under combined compression and shear. Previous studies showed failure of TE cartilage under combined cyclic shear and static compressive loads, while native cartilage remained intact. Subsequent investigations identified a cell rich (matrix deficient) region in the middle layer of TE cartilage, which is sandwiched between matrix rich outer layers with lower cellularity. The objectives of this study are to determine the mechanical behavior of TE articular cartilage throughout its depth under static compressive and shear deformation. Failure under shear deformation, and the relationship between failure and the previously identified matrix deficient and matrix rich regions are of particular interest.

Guided waves are being considered as a tool for detection of defects in plate-like structures for aerospace, civil and mechanical applications, to a large degree because of their ability to travel relatively long distances with low attenuation. When a guided wave encounters a defect, a scattered field is generated that is related to the characteristics of the defect. The far field scattering behavior can be described by a scattering matrix, which describes the amplitude and phase of the scattered signal as a function of the incident and scattered angles. Because of the mode and frequency dependence of guided waves interacting with defects, the scattering matrix is typically defined for specific guided wave modes (incident and scattered) at a designated frequency. Prior work has utilized finite element modeling or wave field scanning to estimate scattering matrices either numerically or experimentally, which may be inconvenient because of computational or experimental issues. Here we propose a methodology to estimate a scattering matrix based on limited experimental data recorded from a spatially distributed transducer array. Baseline subtraction is first used to obtain changes in received signals resulting from the introduction of the scatterer. The differenced signals are then processed to provide a limited number of scattering matrix data points corresponding to incident and scattered angles for specific transducer pairs. The radial basis function interpolation is applied to these points to estimate the scattering matrix. Result from a glued-on steel file is presented to evaluate the efficacy of the proposed method. The method is also applicable to the fatigue cracks caused by loads.

Impairment of the anterior cruciate ligament (ACL) is a common injury causing rotational instability of the knee joint. It is difficult to directly evaluate ACL-deficient patients in internal/external rotations due to risk of further injury. The aim of this study was to evaluate standing target matching’s ability to challenge ACL-deficient patients in internal/external rotational moments. We hypothesized ACL injured subjects would exhibit larger external rotation moments during knee extension when compared to healthy subjects. Ten subjects participated in this study; four (2 males, 2 females) had no history of knee injury and six (3 males, 3 females) sustained ACL rupture within 6 months prior to testing. All subjects were regular participants (> 50 hrs/year) in level I and II sports. Standing target matching required subjects to position the cursor on a target consisting of two concentric circles using anterior/posterior and medial/lateral shear forces and internal/external rotation moments. The limb controlling the cursor was coined the mobilizer. The limb not controlling the cursor but still maintaining stability for the subject was coined the stabilizer. External rotation, negative transverse knee moment, of the stabilizing limb during knee extension was observed to be higher in ACL-d subjects when compared to healthy subjects. We believe that the standing target matching protocol is effectively challenging ACL deficient subjects in internal and external rotations in a safe manner. The ACL deficient limb is exhibiting higher external rotation moments during knee extension as a preventative measure in the absence of the passive restraint provided by the ACL.