Impact of doubling heavy vehicles on bridge

1. Impact of doubling heavy vehicles on bridge Dr. Hua Zhao(a), Dr. Nasim Uddin(a), Rahul Kalyankar(a), Adel Elfayoumy(a), Dr. Ton-Lo Wang(b), Dr. Necati Catbas(c) a University of Alabama at Birmingham b Florida International University c University of Central Florida

2. Introduction • The use of heavy vehicles (18 wheelers) is the backbone of logistics and economic success, and national projections predict that freight shipments will double in the next ten years. • In 2007 in United States, 12.8 billion tons of freight was transported by trucks and it is expected to be 18.40 billion tons in 2040. As freight volumes shipped by truck in the United States continue to increase, the increase must be accommodated by increasing the number of trucks, increasing the weight of trucks, or both. • It is quite obvious that increasing the number of heavy vehicles or the weight of heavy vehicles is detrimental to bridge lifetime. The congestion problem due to increased number (i.e., doubling) of heavy vehicles thus must be attacked. Moreover, additional repetitive loading may cause fatigue cracking in these bridge superstructures and limit the service life of a bridge.

3. Introduction (Cont.) • One essential issue is then how to increase the load capacity of trucks. Today this is to a very large extent connected to the masses and dimensions, which are strictly regulated. The state of Alabama is designated “a focused state” for truck issues. • Consideration will be given to the congressionally proposed 97,000 lbs., six-axle configuration, as well as other configurations of heavy trucks in use in Canada, a NAFTA partner of USA. The state of Florida with major ports serving as hubs for surface transportation with heavy vehicles will benefit greatly from this research.

4. Problem statement • The useful life of highway bridge superstructures is directly affected by a truck’s gross weight, axle weights, and axle configuration and the damages occurred in the bridge deck and in the main superstructure elements. • The severity of damage is a function components of structures and construction materials used. Additionally, many of the older steel bridge girders are particularly prone to fatigue failures directly related to truck weight. • Bridge costs associated with increased truck weights are the result of the accelerated maintenance, rehabilitation, or replacement work that is required to keep structures at an acceptable level of service.

5. Objectives Investigate the effect of meeting increasing freight demands on bridges. compare the effect of heavier trucks to the effect of doubling the number of heavy vehicles under the present legal weight restrictions. Calculate the characteristic bridge traffic load effects bridges of different lengths. Characterize the traffic measured by WIM data in terms of its influence on characteristic bridge load effect Calculate the cost effect of increasing loads on bridges

6. Task-1 Investigate the impact of “proposed congressional legislation on increasing truck weight” and “doubling truck loads” on the types and degrees of damage to bridge components Data collection and Analysis Characteristics of typical trucks will be processed from acquired data. These characteristics include counts, number of axles, axle weight, axle spacing, and travelling speed. Also, multiple-presence cases will be synthesized: in lane, side by side in tandem, as well as side by side and behind. Identification of the Representative Vehicle Groups Based on the synthesized data, static analysis will be performed to determine the girders most sensitive to truck loads. Numerical models for different types of beam-girder bridges will also be developed. Numerical model of truck-bridge coupling vibration will be established by the finite element method. MATLAB programming will be developed to categorize the types of vehicles found in the running fleet into representative groups or types.

7. Task-1 (Cont.) Realistic Truck-Bridge System Simplified Truck-Bridge Model AL-Tri-axle AL 3S2 AL 3S3 Side and front View of Simplified Truck-Bridge Model Proposed 97 kip Trucks (97-S & 97-TRB)

8. Task-1 (Cont.) ALDOT 5Axle Calibration Truck (Left) Schematic (Right) Real Modeled of ALDOT 5Axle Truck and Bridge using LS-DYNA for B-WIM FEA

9. Task-1 (Cont.) TWHs for each month TWHs for entire year AWH for each month

10. Task-1 (Cont.)

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12. Task-1 (Cont.) The ALDOT certified truck has been calibrated. Measurement of Static Load and Axle Spacing of the truck has been done too. The ALDOT truck has been modeled using LS-DYNA for B-WIM Finite Element Analysis (FEA) to simulate the exact situation for a moving truck taking into consideration every single detail about the truck to be more accurate resembling the exact conditions. The collected data from the WIM stations have been analyzed to get most prevailing trucks (2-axles and 5-axles truck) and their frequencies in a specific rout for a certain period of year. Characterization is being preformed on the traffic measured by WIM data in terms of its influence on characteristic bridge load effect. Using the outputs of the FEA truck model with the analyzed WIM data a realistic truck with a realistic characteristic bridge traffic load effects will be modeled.

13. Task-1 (Cont.) c) Describe the types and degrees of damage to bridge components: The data and information required to estimate the network cost of the damages (in prestressed beams, steel girders, and bridge decks) caused by increases in truck weight will be identified; and costs will be estimated using algorithm (based on NCHRP 495) that predicts changes in truck-weight histograms and in fatigue-truck models caused by changes in legal and permit truck weight with a Alabama bridge case study. d) Impact-Cost Estimation: This task will use NCHRP 495 methodology to a specific scenario of truck weight limit change with a 20-year planning period (PP), for projecting to the future would be readily available. These parameters may include discount rate, traffic growth rate, and expected funding levels. Four cost-impact categories are covered in the methodology: Fatigue of existing steel bridges, Fatigue of existing RC decks, Deficiency due to overstress for existing bridges, and Deficiency due to overstress for new bridges.

14. Task-1 (Cont.)

15. Task-2 Investigate Truck Configurations to minimize the effect of weight increase: Specific configurations of heavy trucks, Specific configurations of heavy trucks, such as additional axles or long-combinations, will also be investigated to minimize the effect of a weight increase and reduce the impact to bridges. It will include first, comparison of the effect of heavier trucks to the effect of doubling the number of heavy vehicles under the present legal weight restrictions. This is to determine if allowing an increase in truck weight provides better or worse bridge durability and longevity compared to increasing the number of trucks to meet freight demands. Evaluate several different aspects on the masses and dimensions of trucks In terms of the logistic effects, there are a number of different ways to change masses and dimensions of the truck and the combination of trailers and other equipment. Load capacity for trucks can be counted in three different ways, depending on the kind of goods and industry segment. Trucks’ load capacity measured in number of pallets or volume are seldom fully loaded by weight. This is by then a potential for increased utilization of the trucks. By adding load area length, the used weight capacity can be increased.