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A new bridge had been under construction beside the older Barkadahan Bridge. Instead of expanding the existing bridge, the proponents decided to build another bridge likely so as to reduce disturbance of traffic along the already congested first bridge. This is the same strategy for the bridge across the Pasig River in Nagpayong/Napindan that will reduce the potential bottleneck for when C-6’s expansion is completed. Unfortunately, the bridges don’t seem to include provisions for exclusive bicycle lanes that are clearly incorporated along much of C-6.
I took this photo as we were in queue at the approach to the intersection of Highway 2000 and the Manggagan Floodway’s East Bank Road. The new bridge can be seen here bearing eastbound traffic. The alignment at the intersection has not been addressed and so requires through traffic to basically swerve towards the entry to Highway 2000.
Here’s the intersection and the newly opened bridge. Note the vehicles coming towards my position as they follow a trajectory from the bridge to the narrow exit leg of Highway 2000.
Instead of a single lane along each direction, the two bridges now allow for at least 2 lanes of traffic either way. I say at least because a case can be made for 3 lanes to be indicated (there are no lane markings yet). The issue here though is that there is significant truck traffic crossing the bridge and two trucks traveling beside each other easily occupies the entire bridge. Thus, maybe a wide two lanes can be designated for both bridges with an opportunistic third lane forming depending on the traffic.
Last May, we went to a zoo in Rodriguez (formerly Montalban), Rizal. Using Waze for directions to the zoo, the app took us to a submersible bridge across the wide Marikina River from the main highway (M.H. Del Pilar) to the mainly residential area where the zoo was located. Following are photos of the submersible bridge and the newer more conventional bridge located a little further down the highway.
Submersible bridge connecting Barangay San Rafael with Barangay San Isidro
The “all-weather” bridge as seen from the submersible
There are many bridges like this submersible one across the country. Many were built as weirs or dams that could be used as bridges when the water level allowed it but could let water pass above it during wetter days. Incidentally, there’s one along a popular alternative route between Quezon City and Marikina in Tumana. That bridge can be impassable during times of heavy rains.
The need for basic transport infrastructure cannot be emphasized more when we see photos or reports on makeshift bridges and very rough roads that many people use for travel between their homes and the places where they work, attend school or to go to markets to sell or purchase items like food. Many people living in rural areas continue to be in poverty because they lack the infrastructure required for them to be productive. Nevermind that most wealth and productivity is in urban areas. Are we encouraging people who don’t have to be in cities to flock to the cities? And who will be left in the farms? To fish? To produce the food that is so vital for everyone? This is actually a delicate system that hangs in the balance if we cannot support rural development as well as we have urban development.
A hanging bridge in Tarlac is basically the only way for people to travel across this river, which swells during the wet season. The span is suspended from two columns at either ends of the bridge where there are makeshift stairs for people to climb unto and off the bridge.
Another view, this time from one end of the hanging bridge shows a crude structure made out of steel cable, reinforcing bars and whatever wood they could use as planks and hand rails. It looks flimsy but they make do with it out of need. We learned that in times when the bridge was destroyed by typhoons, they would rebuild it with little help from the government.
The term “buwis buhay” comes to mind every time I look at these photos and others I have taken of rural roads in Tarlac and other parts of the country. People, especially children and those working hard to care for their families, should not have to risk lives or limbs just so they could go to work or school. Farmers and fishermen should be provided efficient access to markets so as to encourage them to continue in their contribution to food production. And perhaps we should think twice about building expensive white elephants for vainglorious attempts at mega structures especially when we still have a lot to accomplish in basic transport infrastructure.
I am always amused whenever I read or hear news about big bridge projects being proposed by politicians in the Philippines. There is no lack of interest in these types of projects considering the many islands comprising the country. However, at this time and with the urgent demand for other transport infrastructure like access roads (farm to market, tourism, etc.), public transport systems, airports and ports, bridge projects of the “mega”-scale can be considered more as follies than smart investments.
Among the projects I have heard or read about are bridges connecting:
- Cebu and Bohol
- Cebu and Negros (Negros Oriental)
- Panay (Iloilo) and Negros (Negros Occidental)
- Panay (Iloilo), Guimaras and Negros (Negros Occidental)
- Batangas and Mindoro
There is also a bridge proposed to cross the Pangil Bay in Mindanao that has been part of many conversations pertaining to development in Northern Mindanao. These bridges are entirely different in terms of scale and traffic from, say, the proposed third bridge connecting Cebu and Mactan Islands or even the more basic bridges that should have been built many years ago in order for people in rural areas to have direct and safe access to schools, hospitals and workplaces. We see so many images and viral videos of children crossing swollen rivers using make-shift foot bridges, boating or even just walking or swimming across the rivers. Shouldn’t our leaders prioritize these instead of mega bridge projects?
I still have the same questions as before for the proponents of these bridges:
- Are these bridges economically and financially viable?
- What would be the traffic for these bridges?
- Would the money spent for any of these bridges be better allocated for other infrastructure projects in their constituencies?
The first and second questions are often easily answered but it can be argued that traffic forecasts and estimated benefits can be drastically and dramatically increased just so a project is justified. The third one is usually the testy question that, when combined with the first two could be very difficult to answer and explain. Many cities and provinces in the country lack basic transport infrastructure as well as infra for social services (e.g., schools, health centers, hospitals, etc.). And even with health centers, hospitals and schools being built, their facilities and human resources are often less than satisfactory or adequate for the people they are supposed to serve and benefit. These should be on the top of priorities rather than mega bridge projects whose potential benefits will take years, if ever, to actually realize.
Following is a Position Paper prepared by the Institute of Civil Engineering and the National Center for Transportation Studies to clarify some issues pertaining to truck overloading. The position paper was presented to the Technical Working Group under the House of Representatives Committee on Transportation, which is handling the issue.
This position paper was crafted to clarify some issues pertaining to truck overloading and the implementation of the national law (R.A. 8794) from a technical standpoint, and based on an independent assessment of the concerns put forward recently.
Among the issues raised were on the maximum axle load of 13.5 tons, the computed maximum gross vehicle weight (GVW), and the implications of their enforcement on the transport of goods and the trucking industry.
In the absence of extensive data from measurements on actual roads and bridges in the Philippines, reference is frequently made to tests and studies by the American Association of State Highway and Transportation Officials (AASHTO), which are adopted by many other countries.
2. Maximum axle load
For benchmarking purposes, an 8.2-ton axle is referred to as the equivalent single axle load or ESAL. One (1) ESAL is equivalent to a damage potential of 1.0 based on road tests conducted by AASHTO. Damage potential increases very rapidly as the axle load increases. The maximum axle load of 13.5 tons is equivalent to 60 times the damaging potential of an ESAL or 8.2-ton axle load.
The designation of a 13.5-ton maximum already takes into consideration the practice of overloading. (Note that the original maximum single axle load was 8.0 or 8.2 tons.) The 13.5 tons is based on studies conducted by the DPWH back in the 1990s (Philippine Axle Load Study or PALS), which determined the maximum single axle load that may be allowed without compromising the integrity of structures such as bridges. The study measured the weights of trucks throughout the country to establish typical weights for different types of trucks.
For tandem axles, a different maximum load is prescribed due to established findings by AASHTO that two closely spaced axles have a much greater combined damaging potential than two single axles that are far apart. To keep the damaging potential in check, AASHTO has established that in the case of tandem axles, each axle in the tandem should have a maximum load that is 20% less than the maximum allowed for single axles. Thus, the maximum axle load for tandem axles in the Philippines is 10.8 tons, for a total of 21.6 tons for the tandem.
A similar process of reduction is applied to tridem axles and so on, where the damaging potential changes as a function of the proximity of the axles to each other.
3. Maximum gross vehicle weight
The maximum gross vehicle weight (GVW) computation is partly based on the maximum single axle load. Thus, it is clear that a higher maximum single axle load leads to higher maximum GVW.
The GVW is computed based on the optimum distribution of loads for different types of vehicles. This optimum distribution considers the maximum allowable axle loads as discussed above (AASHTO, 1987) as well as the loading characteristics of bridges, for example as as detailed in the AASHTO LRFD Bridge Design Specifications (2004).
Further, the optimum loads also take into account the stability of the vehicle as it travels along highways and bridges.
The experience in the U.S. where a compromise was reached between government and the private sector concerning maximum GVW is possible because the weights are based on a maximum single axle load of 9.1 tons and the optimum distribution of load for different types of trucks.
4. Consequences of overloaded vehicles
In the previous sections, the impacts of overloading on road infrastructure such as pavements and bridges were taken into consideration. Overloaded vehicles, particularly trucks, can have detrimental effects on highway safety and traffic operations, too.
Highway safety and traffic operations
Overloading would particularly have impacts on the following handling and stability aspects for trucks, affecting safety in highways:
- Rollover threshold
- Steering sensitivity
- Low-speed off-tracking
- High-speed off-tracking
Meanwhile, impacts on traffic operations include:
- Speed on upgrades
- Expressway/highway merging, weaving, and lane changing
- Downhill operations
- Intersection operations
- Traction ability
- Longitudinal barriers
The above factors have been analyzed and are the subject of a special report by the Transportation Research Board of the U.S. (TRB, 1990). It has been established, for example, that involvement in fatal road crashes increases as the GVW range increases. Also, it has been established that increased truck weights lead to greater reductions in speed and difficulties in merging, weaving and lane changing, and require greater sight distances for safe stopping.
Modification of trucks
The modification of trucks here pertains to the addition of at least one axle with the objective of increasing the GVW while also decreasing the loads of the axles, in order to comply with maximum axle limits.
Any modifications on trucks, especially the addition of axles, should comply with traffic safety standards including those pertaining to handling and stability. Thus, modified trucks should comply with the specifications of the manufacturer or with established standards, if any, for the modification in question.
Any modifications should also be subject to inspections. Problems will arise if there are no standards. In such cases, the manufacturer or experts in the industry should be consulted. The LTO should defer to the recommendations and disapprove any modifications that are not complying with standards or recommendations by qualified persons especially the manufacturer.
In the absence of comprehensive studies on such modifications, data on road crashes or breakdowns (e.g., flat tires, broken axles) need to be collected in order to establish their frequency, determine how serious these tend to be, and ascertain what the crashes or breakdowns are attributed to. This would require detailed information on crashes and breakdowns over a period of, say, 2 to 5 years for statistical significance.
5. Conclusions and Recommendations
The 13.5 tons designated as the maximum single axle load in the Philippines already incorporated the practice of overloading and thus becomes non-negotiable considering that the DPWH has already taken into consideration the maximum loads that can be withstood by highway structures especially bridges in the country. This maximum single axle load is notably higher than the allowance in the US and most other countries.
The following are recommended for further consideration:
- State the allowable maximum axle loads in terms of single axle, tandem axles, tridem axles and so on, in order not to create confusion on the interpretation of the allowable maximum loads.
- Establish standards, type approval system, and monitoring system for truck modifications, in order to ascertain compliance with safety and stability standards.
- Conduct studies on actual axle loads and GVWs on a more regular basis, say every 5 years, by the DPWH, in order to establish a database from which allowable maximum axle loads and GVWs may be updated in aid of legislation.
- Conduct impact assessments.
The U.S. Department of Transportation (2000) recommendations that may be relevant in the impact assessments include:
- Infrastructure costs – including implications on road pavements, bridges and geometrics
- Safety impacts – including crash/accident rates, public perception, vehicle stability and control, and vehicle comparisons
- Traffic operations – impacts on road capacity and speeds
- Energy and environment – impacts on fuel consumption and vehicle emissions
- Shipper costs – impacts on cost of transporting goods
Impact assessments are essential in order to establish directions for determining the benefits and costs attributed to various scenarios that are currently being discussed at the TWG level. Such benefits and costs will serve as inputs in aid of legislation to improve on the provisions of R.A. 8794 and its Implementing Rules and Regulations.
Design standards particularly for road pavements and bridges in the Philippines are mainly based on AASHTO standards and specifications. The AASHTO standards and specifications are based on AASHTO design vehicles along with their prescribed weight/load distributions. It follows, therefore, that anyone adopting the AASHTO design standards and specifications like the DPWH should also adopt the AASHTO design vehicle specifications. Otherwise, the application of standards and specifications for design will be flawed, resulting in sub-standard infrastructure.
As a general rule, if the Philippines is to adopt a different set of load distributions, maximum axle loads, and gross vehicle weights for its trucks, the country should likewise develop or revise its design standards and specifications to match local experience or setting. This would require comprehensive studies to be led by civil engineering experts in the Philippines and patterned after similar studies conducted elsewhere including the United States.
AASHTO (1987) Guide for Maximum Dimensions and Weights of Motor Vehicles and for the Operation of Non-Divisible Load Oversize and Overweight Vehicles, Washington, D.C.
AASHTO (2004) LRFD Bridge Design Specifications, 3rd Edition, Washington, D.C.
Department of Transportation, U.S. (2000) Comprehensive Truck Size and Weight Study, Federal Highway Administration, Washington, D.C.
Transportation Research Board (2007) Legal Truck Loads and AASHTO Legal Loads for Posting, NCHRP Report 575, National Cooperative Highway Research Program, Washington, D.C.
York, J. and Maze, T.H. (1996) Applicability of Performance-Based Standards for U.S. Truck Size and Weight Regulations, Semisequicentennial Transportation Conference Proceedings, May 1996, Iowa State University Institute for Transportation.