Additional Connectors Research Articles

Traffic Analysis for Highway-to-Highway Interchanges on Automated Highway Systems: Congestion in Absence of Dedicated Ramps

Special connector ramps linking the automated lanes at automated highway–to–automated highway interchanges may be needed to enable continuous automated driving between two crossing highways. Although a typical cloverleaf configuration has only two levels and is more amenable for such additions, the sharp curvature of this design usually imposes constraints on traffic speed and flow. Because of these constraints, most highway–to–highway interchanges in urban areas have straighter lanes but tend to involve three or more levels. Building the additional connector ramps to accommodate eight high-speed turning movements at an area where the geometry is already complex could be difficult or costly. Therefore, proponents of automated highway systems (AHS) face a major dilemma. This dilemma is studied, including the impact of not providing automated connector ramps on the manual and AHS traffic on manual lanes at or near a highway-to-highway interchange. It is shown that, with a typical cloverleaf design, in the absence of the additional connector ramps, any moderate to heavy AHS-changing traffic could severely disturb the flow of through traffic, seriously exacerbate congestion, and possibly cause a traffic breakdown at the interchange area. These effects will most likely negate any mainline throughput benefits for which an AHS is designed.

Analysis of Built‐up Timber Columns Using Matrix Progression Method

Most available methods of predicting the buckling loads of layered and spaced timber columns are analytical methods. These are only suitable for columns with constant number and spacing of connectors in each joint of the columns. For added strength and for practical reasons, columns with additional connectors at the ends are more desirable. This usually requires the use of a numerical method for the prediction of their buckling loads. This paper presents a simple numerical method that can be used on microcomputers to predict the buckling loads of these columns. The method is based on the matrix progression technique. The slip modulus of the connectors adopted in the program is that of the Kuenzi beam on elastic foundation method. To verify the method, 89 layered and spaced timber columns were built and tested. The method was also compared with the Pleskov method.

A technique for measuring frequency response of pressure, volume, and flow transducers.

A device and methodology is presented for testing the frequency response of pressure, volume, or flow transducers. Also reported are responses of selected transducers of all three types over the range of 2--120 Hz. Several pressure transducers tested had good frequency response when connected to the test system with a minimum of interconnecting fittings; others did not. Use of additional connectors degraded the response as did the addition of air-filled catheters. The frequency response of the pneumotachometers tested were influenced largely by the response characteristics of the associated pressure transducer and interconnecting fittings. These results emphasize the need to test the response characteristics of any transducer with specific connectors and fittings that are to be used to make the actual measurements of pressure, volume, or flow.

Behavior of Wood-Concrete Composite Beams

Thirteen wood-concrete composite T-beams were fabricated and tested. Epoxy resin was used to bond the wood web to the concrete flange. By proper design, it was possible to stress the concrete in compression and the wood in tension as long as the bond between wood and concrete remained effective. It was found that the beams function as composite sections and carry substantial loads before failure. Four failure modes are identified: Sliding shear, beam shear, tensile wood failure and concrete compressive failure. Beams glued while the concrete was fresh performed at least as well as beams glued after the concrete had set. Longitudinal nails used as additional shear connectors substantially increase the horizontal shear resistance between wood and concrete. Reinforcing wood strips also increase the sliding shear resistance. The effect of other variables remain to be considered.