Straight Deck Research Articles

Seismic performance of highway bridges considering sacrificial abutment: a case study in Afghanistan

The effect of skewness on the sacrificial seat-type abutment and abutment interaction with the skew deck is quite well known. Unlike the simplified approach, this study focuses on the effect of skewness on the seating width of seat-type abutment by providing a rigorous deck model in the analysis while the sacrificial seat-type abutment interacts with the straight deck. This effect is investigated by comparing the seismic performance of two case study bridges, the bridge with elastomeric bearing pad as a bearing mechanism, namely the conventional bridge and the bridge with lead rubber bearing, as an isolated bridge. Realistic seismic response behaviors of these bridges were simulated by nonlinear 3D models. The models are capable of simulating the flexural yielding of piers, the bilinear behavior of isolation bearings, the elastic perfect plastic behavior of elastomeric bearings of the conventional bridge and the other important nonlinear behaviors of these structures. The results highlight the effectiveness of isolation bearing on seismic performance of the isolated bridge, and it was revealed that in the early pounding frequencies, passive forces on the sacrificial backwall springs are uniformly distributed. Whereas for the last pounding frequencies, the passive forces on the backwall are not uniform anymore, this implies that the increase in the pounding frequency leads to an increase in the possibility of deck rotation in the straight deck. Moreover, the result confirms that the earthquake energy absorbed by the fusing backwall could significantly lead to a reduction in dissipation energy by the pier. These results suggest recommendations to improve the seismic performance of the conventional bridge system in the country.

Prediction of the backwater level due to bridge constriction in waterways

AbstractThis article proposes a mathematical method to calculate the backwater level at bridge constrictions for compound channels. Such a model is necessary, as many of the previously developed simple formulas yield inaccurate results. Parametric studies on a single‐opening semicircular arch, single‐opening semielliptical arch and single‐opening straight deck bridge were also conducted using the commercial software HEC‐RAS to investigate the influences of different factors on backwater level. The results indicated that the Froude number, opening ratio, discharge and roughness coefficient impact the backwater level considerably. Hence, a simple mathematical method was developed based on these parameters and validated using experimental data in a symmetrical two‐stage channel with different roughness coefficients for different types of bridge models. The results obtained using the proposed formula corresponded well with the experimental data and the results obtained using the energy method, which is accurate and the most commonly used method to calculate backwater level.

Testing the feasibility of using a conveyor belt to load weanling and nursery pigs for transportation.

Transportation is known to be a multi-faceted stressor, with the process of loading being one of the most significant factors impacting the stress to which animals are exposed. This project was designed to determine if using a conveyor to load pigs into the top deck of a simulated straight deck trailer could lower the stress to which pigs and handlers are exposed. Pigs were assigned to either a Control group that were herded up a stationary conveyor ramp into a top deck trailer (2.5 m above the ground); or Conveyor group which were herded onto a mobile conveyor into a top deck trailer. The conveyor was 7.6 m long, 0.9 m wide and rose to 2.5 m high at a 16° slope, and moved 11.3 m/min. Two age groups were tested; Weanling pigs which were moved in groups of 20 (n = 14 groups/treatment) and Nursery pigs which were moved in groups of 10 (n = 15 groups/treatment). Behavior was recorded during loading, including slips and falls, vocalizations, assists, and time to load. Heart rate of 2 sentinel pigs/group and the handler were recorded during loading, and body temperature of the handler after loading. Pigs were held in the simulated trailer for 30 min while heart rate was recorded. After which, they were unloaded and held in a holding pen for an additional 30 min while heart rate was recorded. There were no treatment differences for slips or falls (P < 0.90). Vocalizations were too few to analyze. Both Weanling (2.8 ± 0.7) and Nursery (1.6 ± 0.5) Conveyor pigs needed to be assisted onto the conveyor more than Weanling (1.2 ± 0.4) and Nursery (0.3 ± 0.1) Control pigs (P < 0.06). There was no difference in total loading time between the treatments for any age group (P < 0.15), with Weanling and Nursery pigs loading in 50 to 45 s, respectively. There were no treatment differences for heart rate variability measures (P > 0.10). However, loading increased heart rate of Nursery pigs (204.9 ± 5.7 bpm, P < 0.005), but not Weanling pigs (172.1 ± 9.0 bpm). Nursery pigs had a greater ratio of low frequency to high frequency power during loading (P < 0.02) compared to other phases of the procedure in both Control and Conveyor groups. Heart rate (93.9 ± 1.9 bpm) and body temperature (31.1 ± 0.3°C, eye temperature) of the handler was not affected by treatment (P < 0.26). Based on behavior and physiology, the pigs had similar experiences in both treatments. This study shows that it is feasible to use a conveyor to load pigs, but it may not be advantageous.

Understanding Calatrava’s bridges: A conceptual approach to the ‘La Devesa-type’ footbridges

As a recent result of the modern structural mastery of developed societies, many designers concerned with aesthetics, most of them with low technical training, but with hardly any technical restriction to their creative freedom, have begun to collaborate with structural engineers. They play an increasingly important role in design teams, which are now interdisciplinary, mainly for short and medium-span bridges located in urban environments, where aesthetic quality may be a desired, or even the primary, objective. This paper is focused on understanding the complex structural behaviour of one of the most frequently built types of bridges born from this collaboration: the bridge composed of a straight deck supported by an eccentric inclined arch attached to its edge. This type of bridge was pioneered by the well-known Spanish engineer and architect Santiago Calatrava, who designed the ‘La Devesa’ footbridge.The study is carried out gradually. Firstly, the ‘classical’ arch bridge (with a vertical arch attached to the axis of the deck by means of a set of vertical hangers) is studied and taken as a reference. Then, the effect of moving laterally the vertical arch as far as the edge is described and analysed. After that, and keeping the arch attached to the edge of the deck, the effect of rotating the arch about a longitudinal axis is analysed. Finally, the effect of stiffening the hangers is discussed. The paper finishes by presenting some considerations about the structural response of these bridges and recommendations about their most suitable structural configuration.

Using Pinochle to motivate the restricted combinations with repetitions problem

A standard example used in introductory combinatoric courses is to count the number of five-card poker hands possible from a straight deck of 52 distinct cards. A more interesting problem is to count the number of distinct hands possible from a Pinochle deck in which there are multiple, but obviously limited, copies of each type of card (two copies for single-deck, four for double deck). This problem is more interesting because our only concern is to count the number of distinguishable hands that can be dealt. In this note, under various scenarios, we will discuss two combinatoric techniques for counting these hands; namely, the inclusion–exclusion principle and generating functions. We will then show that these Pinochle examples motivate a general counting formula for what are called ‘regular’ combinations by Riordan. Finally, we prove the correctness of this formula using generating functions.

Bridge afflux analysis through arched bridge constrictions using artificial intelligence methods

Although many studies have been carried out for estimating the afflux through modern straight deck bridge constrictions, little attention has been given to medieval arched bridge constrictions. Hydraulic Research Wallingford in the UK (Brown, P.M., 1988. Afflux at arch bridges. Report SR 182. Wallingford, UK: HR Wallingford) recently published a major coverage of both experimental and field afflux data obtained from arched bridge constrictions. The report pointed out that the present day formulas developed for estimating the bridge afflux are inadequate to apply to ancient arched structures. Therefore, this study aimed at developing new afflux methods for arched bridge constrictions using multi-layer perceptrons (MLP) neural networks, radial basis function-based neural networks (RBNN), generalised regression neural networks (GRNN) and adaptive neuro-fuzzy inference system (ANFIS) model. Multiple linear and multiple nonlinear regression analyses were also used for comparison purposes. Mean square errors, mean absolute errors, mean absolute relative errors, average of individual ratios between predicted and actual values, and determination coefficients were used as comparison criteria for the evaluation of model performances. The test results showed that MLP, RBNN, GRNN, and ANFIS models gave reasonable accuracy when applied to both the field and experimental data collected by Hydraulic Research Wallingford.

A simple formula for estimating backwater at bridge constrictions

The past experimental studies to investigate the backwater effects due to bridge constrictions have been mostly performed in setups of single rectangular channels with fairly smooth surfaces. Therefore, there is a need to investigate more realistic cross-sectional shapes and roughness conditions. The most obvious case is to consider bridges in natural channels with floodplains. This paper reports the findings of model testing of arch and straight deck bridge constrictions in a compound channel flume with both smooth and roughened surfaces. Four different types of bridge models, namely single opening semicircular, multiple opening semicircular, single opening elliptic, and straight deck models with and without piers, were used in the testing program. An attempt was made to develop a simple formula for estimating bridge backwater as a function of Froude number and opening ratio.Key words: bridge backwater, hydraulic model testing, open channel flow, flood control.

Let's Deal from a Straight Deck

The Delegates Assembly, held on May 12 during the annual convention of the International Reading Association, passed the following resolution on learning disabilities, altered only slightly from the text proposed by the IRA Resolutions Committee.