Design of Cantilevered Overhead Sign Supports

2005 ◽  
Vol 1928 (1) ◽  
pp. 39-47
Author(s):  
Fouad H. Fouad ◽  
Elizabeth Calvert
Keyword(s):  
Traffic Signals ◽  
The United States ◽  
Support Structures ◽  
Fatigue Load ◽  
Fatigue Design ◽  
Previous Edition ◽  
Sign Support Structures ◽  
Design Calculations ◽  
Highway Signs ◽  
New Criteria

The AASHTO 2001 Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals include revised wind load provisions and new criteria for fatigue design. These provisions and criteria differ considerably from those in previous editions of the specifications, and their impact on the design of cantilevered overhead sign supports has not been fully studied. This study assesses the effect of these provisions and criteria on the design of cantilevered overhead sign support structures with the horizontal support composed of a four-chord truss. Wind and fatigue load design calculations of typical structures, located at sites across the United States, were performed with the design provisions of the 2001 supports specifications and compared with design in accordance with the previous edition of the specifications. The induced forces in the primary members of the cantilevered sign support structure were calculated, and corresponding member sizes and weights were estimated. The results of the study demonstrated the effect of the wind and fatigue load provisions on the design of cantilevered overhead sign support structures.

Mitigating Fatigue in Cantilevered Overhead Sign Structures

2015 ◽  
Vol 2522 (1) ◽  
pp. 18-26
Author(s):  
Mohamed S. Gallow ◽  
Fouad H. Fouad ◽  
Ian E. Hosch
Keyword(s):  
Structural Design ◽  
Endurance Limit ◽  
Time History ◽  
Traffic Signals ◽  
The United States ◽  
Wind Pressure ◽  
Wind Gusts ◽  
Power Spectral ◽  
Highway Signs ◽  
Fatigue Endurance

Cantilevered overhead sign structures (COSSs) are widely used across highways in the United States. Several cases of excessive vibrations and failures caused by fatigue wind loads from natural and truck-induced wind gusts have been reported. Not enough research has included the effect of making structural design modifications on the fatigue performance of COSSs. Under fatigue wind-induced loads, the dynamic characteristics (frequency and damping) of COSSs are important parameters affecting their structural behavior. When frequencies of wind load and the structure match, resonance may occur, causing excessive vibrations, depending on the frequency value. If accompanied fatigue stresses exceed the fatigue endurance limit, failure occurs after a certain number of loading cycles. The objective of this study was to investigate stiffness and mass distribution of COSSs to control the structural frequency, thus mitigating fatigue caused by wind-induced gusts. For this purpose, modifications in the members' shape, arrangement, size, and layout of structure were examined. Three layouts were compared: four-chord, two-chord, and monotube COSSs. These layouts were designed according to the 2013 AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals and modeled with SAP2000. Wind pressure power spectral density and time history loading functions were applied to these structures to simulate natural and truck-induced wind gusts, respectively. Results showed that the vertical mono-tube COSS design with curved end post had the least mass, but fatigue stresses were comparable with the four-chord COSS. The two-chord COSS design had the largest mass and exhibited the highest fatigue stresses.

Estimating fatigue design load for overhead steel sign support structures under truck-induced wind pressure

2016 ◽  
Vol 43 (3) ◽  
pp. 279-286 ◽  
Author(s):  
H.P. Hong ◽  
G.G. Zu ◽  
J.P.C. King
Keyword(s):  
Wind Pressure ◽  
Horizontal Wind ◽  
Wind Gust ◽  
Stress Range ◽  
Support Structures ◽  
Design Code ◽  
State Highway ◽  
Fatigue Design ◽  
Sign Support Structures ◽  
Natural Wind

Experimental results of the truck-induced wind gust pressure were used as the basis to develop the equivalent static truck-induced wind pressure for fatigue design in the American Association of State Highway and Transportation Officials (AASHTO). The development does not explicitly quantify the stress range distribution, nor does the development discuss the implied reliability. No recommendation is given to consider truck-induced pressure for fatigue design in the Canadian Highway Bridge Design Code (CHBDC). This study quantifies the stress range due to truck traffic, and calibrates the equivalent static truck-induced wind pressure for fatigue design of overhead steel sign support structures. The reliability-based calibration is focused on the CHBDC. For the vertical excitations, the calibrated pressure is less than 50% of that suggested in the AASHTO. For the horizontal excitations, the calibrated pressure can be greater or smaller than that for the site-dependent natural wind gusts. Therefore, the truck-induced horizontal wind pressure could govern the fatigue design for some sites.

Behavior of Monotube Highway Sign Support Structures

1988 ◽  
Vol 114 (12) ◽  
pp. 2755-2772
Author(s):  
Mohammad R. Ehsani ◽  
Reidar Bjorhovde
Keyword(s):  
Support Structures ◽  
Sign Support Structures

scholarly journals Microscopic Estimation of Freeway Vehicle Positions from the Behavior of Connected Vehicles

2020 ◽  
Author(s):  
Noah J. Goodall ◽  
Brian L. Smith ◽  
Byungkyu Brian Park
Keyword(s):  
Traffic Signals ◽  
The United States ◽  
Traffic Information ◽  
Connected Vehicles ◽  
Connected Vehicle ◽  
Travel Time Prediction ◽  
High Penetration ◽  
Initial Penetration ◽  
Car Following Model ◽  
Status Data

Given the current connected vehicles program in the United States, as well as other similar initiatives in vehicular networking, it is highly likely that vehicles will soon wirelessly transmit status data, such as speed and position, to nearby vehicles and infrastructure. This will drastically impact the way traffic is managed, allowing for more responsive traffic signals, better traffic information, and more accurate travel time prediction. Research suggests that to begin experiencing these benefits, at least 20% of vehicles must communicate, with benefits increasing with higher penetration rates. Because of bandwidth limitations and a possible slow deployment of the technology, only a portion of vehicles on the roadway will participate initially. Fortunately, the behavior of these communicating vehicles may be used to estimate the locations of nearby noncommunicating vehicles, thereby artificially augmenting the penetration rate and producing greater benefits. We propose an algorithm to predict the locations of individual noncommunicating vehicles based on the behaviors of nearby communicating vehicles by comparing a communicating vehicle's acceleration with its expected acceleration as predicted by a car-following model. Based on analysis from field data, the algorithm is able to predict the locations of 30% of vehicles with 9-m accuracy in the same lane, with only 10% of vehicles communicating. Similar improvements were found at other initial penetration rates of less than 80%. Because the algorithm relies on vehicle interactions, estimates were accurate only during or downstream of congestion. The proposed algorithm was merged with an existing ramp metering algorithm and was able to significantly improve its performance at low connected vehicle penetration rates and maintain performance at high penetration rates.

Seismic Design for Offshore Wind Farms – Lessons Learnt From the ACE Joint Industry Project

2021 ◽  
Author(s):  
Marcus Klose ◽  
Junkan Wang ◽  
Albert Ku
Keyword(s):  
Seismic Design ◽  
Wind Turbines ◽  
Wind Farms ◽  
The United States ◽  
Offshore Wind ◽  
Seismic Load ◽  
Support Structures ◽  
Offshore Wind Farms ◽  
Asian Pacific Region ◽  
The Impact

Abstract In the past, most of the offshore wind farms have been installed in European countries. In contrast to offshore wind projects in European waters, it became clear that the impact from earthquakes is expected to be one of the major design drivers for the wind turbines and their support structures in other areas of the world. This topic is of high importance in offshore markets in the Asian Pacific region like China, Taiwan, Japan, Korea as well as parts of the United States. So far, seismic design for wind turbines is not described in large details in existing wind energy standards while local as well as international offshore oil & gas standards do not consider the specifics of modern wind turbines. In 2019, DNV GL started a Joint Industry Project (JIP) called “ACE -Alleviating Cyclone and Earthquake challenges for wind farms”. Based on the project results, a Recommended Practice (RP) for seismic design of wind turbines and their support structures will be developed. It will supplement existing standards like DNVGL-ST-0126, DNVGL-ST-0437 and the IEC 61400 series. This paper addresses the area of seismic load calculation and the details of combining earthquake impact with other environmental loads. Different options of analysis, particularly time-domain simulations with integrated models or submodelling techniques using superelements will be presented. Seismic ground motions using a uniform profile or depth-varying input profile are discussed. Finally, the seismic load design return period is addressed.

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