A Report to the General Manager of the Dubbo City Council for Presentation to the Dubbo City - Coursework Example

THE DUBBO CITY REPORT by Student’s Name Course code and name Professor’s name University name City, State Date of submission Introduction Dubbo is an Exceptional Circumstance (EC) area that is characterised by extremely high amounts of rainfall. In particular the Macquarie River catchment was flooded in the year 2010, 2011 and 2012 leaving the timber bridge over Hyandra Creek damaged beyond repair. It was however salvaged to safe limits so as to allow cars and light commercial passage of up to ten tonnes into and out of the Dubbo area. The farmers in the area utilized this rains to their advantage in order to boost their produce especially in the animal husbandry. Farmers in the crop husbandry were adversely affected as water from the floods clogged the areas making their plant production rates and protein levels low. The National Rural Advisory Council bore witness of this turn of events especially with the inaccessibility of the area which had unfavourably affected the Dubbo economy from time to time. The fact that this is a tourist destination requires that access be maintained at its best to attract revenue to the Dubbo City Council. Further to the economies of scale, the Agricultural sector which is one of the flourishing sources of livelihoods in this area should be facilitated. Transporting of agricultural products from the Dubbo city to the allied markets is affected by lack of appropriate conditions to foster this sector. Reductions in the capacities of products that are ferried at one go has made the profits of the farmers to hit a historical low. Access to other basic facilities worries the local community if this issue goes unsolved for another coming rainy season. The National Rural Advisory council should re-declare the Dubbo City Council an EC area with the purpose of rehabilitating the area bridge to acceptable levels. This report is an effort to resolve the persistent conditions that are faced by the Dubbo community due to fluctuating availability of road transport caused by rains. The Roads Act 1993 The Roads Act 1993 No 33 is very categorical when it comes to building of roads and bridges for public use. The central authority is mandated to build bridges and tunnels wherever there are waters deemed to be navigable. This structure should not by any mean act as an obstruction to the natural resource as much as it is lawful. The local authority is also instructed to publish its intentions to build such structures as bridges within the local newspaper accessible by citizens. The proposal should be availed to the public in any other form possible other than print media for criticism. Any person within the authority’s boundaries is allowed to submit a counter-proposal in less than 28 days after which the authority may declare such submissions null and void. In case where such submissions are made by the larger public, the proposals are subject to possible amendments and implementation where sensible suggestions are made for instance. A person may reject a proposal due to the damages that are likely to be encountered by the implementation such a plan to build a bridge or a tunnel. This damage may not be personal but also a deviation from the doctrines that guide the environmental doctrines (Legislation, 2012). The decisions on the proposals made by the roads authority shall be based on a sound judgment of any submissions made to the authority at the time of tragedy. The authority’s decision must be submitted to the persons involved in the submission of any counteractive information towards such developments. This should include arguments that make sense in the event that the public submissions have been made for example obstruction of a major waterway. The proposal may be altered to accommodate the submissions made by the public towards a healthy and democratic relation as all the public stakeholders are part and parcel of national development. For the case of the Dubbo Bridge which is in question, the vessels under construction act does not apply since this is a seasonal river that is supposed to act as a waterway during the rainy seasons and floods from the Macquarie river catchment. The expulsion or obstruction of such features of economic importance as the boat building business a penalty shall be attracted in terms of a compensation which has to be thoroughly assessed (Legislation, 2012). There is need to use the shortened tendering process which involves the council to attend to this bridge as a matter of urgency. This means that the repairs of Macquarie River Bridge which is the sole connection point in Dubbo area should be dealt with within 7 days of tender publication or invitation as per Clause 171 of the local NSW laws to which the council also binds itself to. The decision to carry out tender shortening due to the exception that this disaster possesses is very clear thus it would not have any future impacts of how it was carried out. However it is suggested that the council contracts a contractor with whom it has cordial past working relationship and performance with the Dubbo County Council. This should be done in accordance to section 55 which allows for selective tendering of recognised contractors through a public advertisement. This may also be based on the integrity and innovativeness displayed by the contractors in ongoing works in order to give a fair judgement in the distribution of the council’s opportunities (Department of Premier and Cabinet, 2009). The Existing State of the Bridge The current state of this 4-span structure has deteriorated over time due to the damages from floods as shown in figure 1 above. These damages have been attributed by hydrodynamic loads, hydrostatic loads and impact loads on the structures. This water has been found the scour the base of the bridges foundation which is responsible of holding the entire bridge and the load. Luck has it that the Benolong Road Bridge has not been affected right from the base but rather its deck and the deck feature which offer support to the load. This has led to the innovation in order to render the bridge usable for quite a while based on the expenses that are likely to be incurred in case of an uncompetitive manner of consultation. The forces that affect the deck and its feature is more of hydrostatic with both lateral and vertical coefficients. The difference between these two forces causes an up thrust as water flows down the stream causing damage on the fastening points which are meant to hold the bridge parts together. In case of lateral forces, the damages emerge from the deflections in case the elements used are not strong enough. The interior and exterior forces on the foundation also seem to have incurred damages during the lateral pressures. This is because this force acts on immersing objects as in the case of the Dubbo bridge structure (Rogers, 2013). Figure 1: A graphic presentation of Hyandra creek floods. In cases whereby the materials used do not have the ability to withstand the floods the lateral forces get in and carry the destruction. It is therefore true to say that the situation in the case of Dubbo’s Hyandra creek bridge cannot withstand most of these forces and need to be restructured. The rapid drawdown of water also affects the ability of the bridge to withstand the as the base is mechanically swept away. Saturated soils below the bridge foundations are also likely to exceed the structural requirement of the bridge and end up deforming the alignment. The deck may have also been damaged by the buoyant force which acts upwards as timber is less dense than water. The bridge tends to float on water during the floods even when it is laced with other materials such as steel connectors. In this case, the flood water exceeded the weight of the bridge and overpowered it thereby washing it away of causing extreme and unrecoverable damages. Since the crawlspace foundation that is seen under the bridge, the vulnerability increase and thus have to be amended in a new design. The hydrodynamic load which also another cause of the turn of events as seen in this bridge. The hydrodynamic forces are dependent on the velocity of water flow and may have lead to collapse of some parts of the bridge. These physical forces are also aggravated by the nature of debris found in the area like in the area. Dubbo area contains stones and gravels that may have affected the timber texture and strength and ended up affected the ability of the bridge to withstand the heavy loads imposed to it. At some points, since the bridge acts as a barrier towards the high velocity flowing water it is likely to be forced of its position due to the combined forces. Testing of this bridge shall serve as an important factor for the choice of materials to be utilised in replacement to avoid rework after another bout of rains. The deterioration of the Hyandra timber bridge should be thoroughly investigated to offer a test report that is well positioned to solve the main durability problems over some years. The increase in traffic volume and the loads ferried via this bridge should also be looked into so as to make sure that the services are enhanced to the stakeholders. These situations make the timber bridges prone to damages by floods as they find them in a weak condition. Damage due to low strength material with a high stiffness coefficient is likely to incur more damages as opposed to the contrary where materials used are strong enough to last to the rainy period. In order to give a proper feedback to the roads committee of Dubbo city council proper assessment of the damages are necessary if they are coupled with integrity checks of the structure. In order to set the priorities high during the damage mitigation period it is the rate at which the damages are occurring should be quantified (Ritter, 1990). Figure 2: Floods ravaging the Hyandra area timber bridge The bridge assessment has to be carried out through physical destructive tests and non-destructive tests. The destructive tests which can be carried include the already visible damages and the analyzed effects in order to establish whether the bridge can be salvaged by the council. Static and dynamic load testing should also be carried out on the bridge on the context that the initial calibrated load is well documented. The council having invested in the measurement tools, this process should not be chaotic in its implementation as much as it poses complexity in identifying the critical areas. The ratio of the cost of testing to that of the bridge should be kept at the acceptable reasonable figure so as to minimize speculation from the stakeholders. The results obtained should then be well documented for the future use by the city roads maintenance committee to avoid time wastage and also help engage in speedy solution finding (Ritter, 1990). Testing Prior to carrying out any implementation, it is important to carry out strength testing of this aging structure. This is to determine the suitability or feasibility of these structural remnants for the sake of durability and structural replacement. In order to ensure public safety strategies and techniques that seek to provide safe structures to the public should be implemented. The constraints with regards to the economy, social and aesthetic vale should be put into consideration so as to provide a sound study. The economic constraints should not however be overseen as compared by the ability to achieve maximum safe load limits for the bridge to serve the community comfortably. The low value of the timber bridge bestows an easy decision making procedure since the material is relatively cheap. Furthermore, the span of the bridge in consideration is short compared to most bridges found in the Australian context (Crews, et al., 2004). This bridge should be imposed on medium span load testing of up to the required minimum of 10 tonnes. In this procedure, the involvement of a loaded truck as a design load is required to carry out the extent of the damages occurring to it. As much as this costing may be destructive to an extent, it is recommended since it offers the real state of the matter as opposed to the other methods. The Centre for Built Infrastructure Research has shown interest in the involvement of all load tests being carried out on bridges thus should be among the invited parties to conduct a feasibility study of the same. The safe load capacities may also be established through application of steel structures within the load tests so as to avoid damages to the original bridge as much as it may seem expensive to the parties involved. This might also extend the scope of testing although it is a mandatory procedure to carry out as per the roads and traffic authorities (Crews, et al., 2004). In addition to the load testing formula of establishing the suitability of the remaining structure, the Dubbo city council should facilitate the non-destructive evaluation. This is a cost effective analysis method that shall offer assessment to the structural conditions that the bridge subscribes to. The fundamentals of these tests require frequency checks to be imposed on the bridge deck so as to establish its material strengths such as stiffness. In order to carry out this procedure, the bridge girders are usually attached with accelerometers whose response to the natural frequency and vibration response are calibrated. The sledgehammer calibrator may be used in this exercise to guarantee accuracy of results in the unloaded conditions of this mid-span bridge. The extensive tests are carried out by hitting the extensive areas of the timber bridge based on reliability models used on the aging bridges across New South Wales. This method is also referred due to its simplicity and accuracy of the reports issued Crews et al. (2004) titled Testing and Assessment Procedures to Facilitate the Management of Timber Bridges Assets. Crews et al. (2004) further insists on this new method of bridge testing as a post requisite for the destructive method as it is supposed to give the rightful direction for the national roads infrastructure. The laboratory based testing method is used in the quantification process of materials to be used in the rehabilitation in an effort to counter future damages. The accuracy of data provided for material assessment is offered in comparison to the existing material in terms of strength. This is meant for the development of field system applications to measure the deflection characteristics and those established by the destructive method (Crews, et al., 2004). Figure 3: The non-destructive testing model (Crews, et al., 2004). Requirements to be met by the Rehabilitation The road classification method requires that bridges be designed from high quality materials that are durable in nature. Under the road transport association, the bridges form very important features of the roads. The fact that this road is registered under the roads act of 1993 as shown above there is increased demand for it to be in a good state due to its feeder properties to the Dubbo City Council. The loading demands therefore should be met as the road transport act argues in its gazetted regulations. The load demands have to adhere by the national heavy vehicle legislation but should not go too low than the recommended figure as this might affect the ability of traders to conduct businesses at will. This shall also provide the consistency of the timber bridge with all the others that are classified within its calibre (Bradford, 1999). The load of 10 tonnes as presently set by the council’s rehabilitation efforts cannot offer general access as prescribed the road transport act. The limits set to a single bridge should be 42.5 tonnes at the lowest instance – apart from cases of overloading and tolerance limits that are set for each set load for a bridge. It is further dictated that the loading requirements can further be determined to serve temporary purposes whenever it calls for. Such a case is when the Dubbo area gets flooded to an extent which the bridge is rendered impassable to vehicles. Whether or not tracks are using this route, the road shall have to be made fit to serve a multipurpose basis. The operational requirements set by the roads transport act should be treated with the relevance they deserve to avoid conflicts. In order to ensure efficiency is reached by the bridge should be redesigned so as to cater for a load of up to two interconnected mass trucks. This shall facilitate conformance to the Council of Australian Governments’ reform agenda to offer better road transport. Since the National Transport Commission has opted for an increment in the vehicle masses due to length, the need to use high strength materials is increasingly becoming needful. The proposed mass of 45.5 tonnes has to be catered for by this bridge considering that these are the newly proposed higher mass limits. Also, the Dubbo area is agriculturally oriented in terms of economy, a fact that shall require that all the basic points be considered in this rehabilitation. The regulated limit is often a dynamic figure that keeps being reviewed every other time the government legislations on roads act are amended. It is emerging that the highest limits for bridges is going to be raised to 65 tonnes which might eventually out phase the Dubbo Bridge. It is with this authority that the efforts to rehabilitate it should be focused on achieving the highest strength possible (Heritage Council of NSW, 2011). Modern times call for modern solutions. The fact that the council wants to maintain the national heritage is welcome although it could be a good idea to meet the modern standards on the upcoming bridge designs. This does not only cover the weight combination that can be carried but also the aesthetic value such a landmark shall be adding to the environment. The modern loads are found to be so uncertain in terms of dynamics and abnormal weights exerted by the massive trucks. The bridges do not possess a fail-safe mechanism as required by the road acts of 1993 and other basic requirements. Higher speeds and sudden braking add towards the stress incurred by the bridge which makes it have a reduced life span than the one that is actually planned for. These extreme forces should be combated through all means necessary including careful choice of materials to be applied. The use of iron material as traditionally used should be avoided as they are prone to sudden failure and their brittle nature further accelerates this fact. During the rainy season, these bridges are also prone corrosion which in turn weakens the connections between the materials making them fail unnecessarily. Iron bolts used in the connection should be replaced with timber locks or guarded properly to avoid the untimely breakdown of bridges due to floods. When corrosion attacks the bolts the bridge fails without a signal through high tension collapse (McCutcheon, et al., 1985) Based on the speed, frequency and weight it is evident that this bridge cannot withstand the modern conditions. With age the bridge has definitely advance in the degree of wear and tear due to the loading and environmental circumstances. The horizontal and vertical stresses that are supposed to be withstood by the bridge need structural evolution to be instilled. The structures therefore need modification to be undertaken without putting into much consideration the attributing aesthetic factors. The frequency of maintenance also has to be highly monitored to avoid the overhaul that is being experienced by the existing bridge. Reconstruction should be facilitated by all means of encouraging such maintenance services within the city councils so as to avoid the cost of reconstruction. This bridge is also expensive to maintain thus this is incomparable to any modern bridge in case the council would wish to replace it. The Hyandra Creek Bridge can be modified to meet the demands if the public committee on roads as long as it does not lose its ability to hold load suitably (Transportation Research Board, 2004). The roads act requires that material being used in the manufacture of bridge parts be affordable to the government involved whether local or central. The approval of timber bridges has been expedited to cater for reforms in the public transport sector considering this is a high income attraction area. The affordability in terms of the maintenance budget on the materials used should be considerate of all factors that contribute towards an ergonomic structure. The affordability budget should also conform to the roads and transport act of 1993 and other legislations that may be put in place with time. The affordability index should also be compared to the safety ratio in order to establish whether these materials meet the intended targets. In another case, it has been found out that a larger share of taxpayers’ money goes a long way to maintaining the bridges due to their lack of affordability in maintenance. In particular, the wooden bridge assets like the one under study consume up to 20% therefore dictating that the bridges’ operating budgets are unsafe (Heritage Council of NSW, 2011). The sustainability of the Hyandra Creek Bridge should be questioned since the expenses that might be incurred in the rehabilitation are likely to be high in terms of material choices to the council. In particular, the bridge maintenance cost during the period ranging from 2010 to 2011 has been on the rise. The value of maintenance has gone to an all-time high of $ 40 million from the low $25 million which is a real reflection on the changing state of affairs in road transport. As much as the Hyandra Creek Bridge might be upgraded, the overhaul cost has to be incurred every five years as it is already a convention. If a new modern bridge were to be introduced in the Hyandra Creek area, the initial cost would even be less than the expected cost of maintenance in the next ten years. Therefore, it is important for the council to upgrade to a new design of bridge that shall not be swept away (Heritage Council of NSW, 2011). The availability of the timber materials may also become an issue of contention in the implementation of the structural design revision. Since the timber is usually extracted from trees that range up to 200 years of age, it may be very hard to source the replacement in case of damages incurred during the floods. The fact that the council through the road transport act is supposed to procure timber from other countries might not be a wise idea as there are better alternatives to be involved. This solution shall only be short lived due to the nature of catastrophes’ unpredictability. In other areas, the availability of long grain timber is not guaranteed thus the end result might be pathetic in terms of quality. A long term solution cannot be developed from the imports neither can it be developed from planting trees today. It is therefore high time to change the design of the bridge (Heritage Council of NSW, 2011). Timber Replacement Once the timber to be utilized in the rehabilitation process has been identified, the rehabilitation process may kick off. Member replacement should be carried out in a manner that is supposed to cushion all the residual strength that should be taken care of. The fact that timber that has been spotted on the bridge is faulty drives the point that timber defects such as decay infections due to long time immersion in water should be acted upon accordingly. All the members adjacent to the cleared sections must be checked to prove that they do not have any defects related damages to judge on whether it is indeed logical for them to be maintained. The field treatment of holes and other available cuts should be done right in the field by use of products that allow easy application. These are the same chemical treatments that are applied when the bridge is still under regular usage (Johnson & Lumber, 1996). Wherever it is possible, the removal and replacement of defective timber should be done in part to save the costs. It is recommended that the infected pieces of timber be removed in order to avoid major problems that may result. In order to enhance the load carrying capacity, the sister elements rather known as the reinforcing elements should be added so as to provide the required strength. Moisture control procedures should be carried out fully in order to enhance bridge lifespan. The old material should be removed due to the age which comes with disadvantages such as permeability leaving the bridge heavy for no reason apparently. This may also inhibit decomposing bacteria if the timber is not well treated thereby posing as a danger to the bridge’s deck (Wagners CFT, 2013). The use of wood as a bridge construction material has been phased out in most parts of the globe in this era due to the nature and frequency of operations undertaken. The council needs to consider replacing this timber bridge by composite metal bridges which according to Matteis (2010) in Steel – Concrete Composite Bridges Sustainable Design Guide are considered to be of superior quality. The vulnerability of the composite materials towards natural catastrophes is minimal thus there would be no disruptions in case of future floods. The durability of metal composite bridges is also enhanced by the structural design to which the construction materials are easily adapted to. The composite bridges are also easy to maintain in comparison to the wooden bridges which require intensive care. Apart from maintenance and the lifecycle, the construction is comparatively easy unlike the aesthetic wooded bridges which are rampant in the Australian commonwealth. The availability of metal is easy compared to wood which at some point requires importation (de Matteis, et al. 2010). Safety Issue The safety of the employees working to see the successful completion of this bridge must also be guaranteed through a proper risk management. This should be done by the Dubbo City council through the contractors who shall be undertaking this rebuilding assignment as per building and construction regulations. These concerns are highlighted within the safe working at heights regulations that are documented by the Australian standards committees. The legislative framework which includes the occupation health and safety 2000/ 2001 and guidance on practice/ safety should be instilled during the construction phase of this project. Restraint of persons working from falling into the river is mandatory by provision of such working platforms as scaffolds and man lifts. Risks associated with falling objects should also be monitored by following the hierarchical controls that have been set in place by these important legislations. The contractor should adhere to OSHS regulations throughout the operations of the bridge’s reconstruction as part of the county council’s requirements. Vetting must also be done to ensure that this happens (Work Cover NSW, 2006). References List Bradford, . M. A., 1999. Mechanics of Structures and Materials: Proceedings of the 16th Australasian. Sidney: Taylor & Francis. Crews, K., Samali, B., Li, J. & Champion, C., 2004. Testing and Assessment Procedures to Facilitate the Management of Timber Bridges Assets. Centre for Built Infrastructure Research, University of Technology, Sydney. NSW Department of Premier and Cabinet., 2009. Tendering Guidelines for NSW Local Government. Sidney: Division of Local Government. Heritage Council of NSW, 2011. Timber Truss Road Bridges of NSW: review of Roads and Traffic Authority’s review of Roads and Traffic Authority’s, New South Wales: Timber Truss Bridges Committee. Johnson, K. A. & Lumber, W., 1996. Repair and Rehabilitation of Treated Timber Bridges, Bloomington: Wheeler Lumber, LLC. Legislation, 2012. Roads Act 1993 No 33. [Online] Available at: http://www.legislation.nsw.gov.au/fragview/inforce/act+33+1993+pt.6-div.2+0+N [Accessed 20 April 2013]. McCutcheon, W. J., Gutkowski, R. M. & Moody, R. C., 1985. Performance and Rehabilitation of Timber Bridges. s.l.:Wooden bridges. Ritter, M. A., 1990. Timber bridges: design, construction, inspection, and maintenance. Minnesota : U.S. Dept. of Agriculture, Forest Service, Engineering Staff. Rogers, C. D., 2013. Structural Damage due to Floods. [Online] Available at: http://www.rimkus.com/craig_rogers_article_in_claims_magazine [Accessed 19 April 2013]. Transportation Research Board, 2004. Cost-effective Practices for Off-system and Local Interest Bridges. Washington DC: Transportation Research Board. Wagners CFT, 2013. Our Products | Timber Bridge Rehabilitation | VIEW GALLERY. [Online] Available at: http://www.wagnerscft.com.au/products/timber [Accessed 26 April 2013]. Work Cover NSW. Safe Working at Heights. Construction Industry Reference Group, 2006. Read More

The local authority is also instructed to publish its intentions to build such structures as bridges within the local newspaper accessible by citizens. The proposal should be availed to the public in any other form possible other than print media for criticism. Any person within the authority’s boundaries is allowed to submit a counter-proposal in less than 28 days after which the authority may declare such submissions null and void. In case where such submissions are made by the larger public, the proposals are subject to possible amendments and implementation where sensible suggestions are made for instance.

A person may reject a proposal due to the damages that are likely to be encountered by the implementation such a plan to build a bridge or a tunnel. This damage may not be personal but also a deviation from the doctrines that guide the environmental doctrines (Legislation, 2012). The decisions on the proposals made by the roads authority shall be based on a sound judgment of any submissions made to the authority at the time of tragedy. The authority’s decision must be submitted to the persons involved in the submission of any counteractive information towards such developments.

This should include arguments that make sense in the event that the public submissions have been made for example obstruction of a major waterway. The proposal may be altered to accommodate the submissions made by the public towards a healthy and democratic relation as all the public stakeholders are part and parcel of national development. For the case of the Dubbo Bridge which is in question, the vessels under construction act does not apply since this is a seasonal river that is supposed to act as a waterway during the rainy seasons and floods from the Macquarie river catchment.

The expulsion or obstruction of such features of economic importance as the boat building business a penalty shall be attracted in terms of a compensation which has to be thoroughly assessed (Legislation, 2012). There is need to use the shortened tendering process which involves the council to attend to this bridge as a matter of urgency. This means that the repairs of Macquarie River Bridge which is the sole connection point in Dubbo area should be dealt with within 7 days of tender publication or invitation as per Clause 171 of the local NSW laws to which the council also binds itself to.

The decision to carry out tender shortening due to the exception that this disaster possesses is very clear thus it would not have any future impacts of how it was carried out. However it is suggested that the council contracts a contractor with whom it has cordial past working relationship and performance with the Dubbo County Council. This should be done in accordance to section 55 which allows for selective tendering of recognised contractors through a public advertisement. This may also be based on the integrity and innovativeness displayed by the contractors in ongoing works in order to give a fair judgement in the distribution of the council’s opportunities (Department of Premier and Cabinet, 2009).

The Existing State of the Bridge The current state of this 4-span structure has deteriorated over time due to the damages from floods as shown in figure 1 above. These damages have been attributed by hydrodynamic loads, hydrostatic loads and impact loads on the structures. This water has been found the scour the base of the bridges foundation which is responsible of holding the entire bridge and the load. Luck has it that the Benolong Road Bridge has not been affected right from the base but rather its deck and the deck feature which offer support to the load.

This has led to the innovation in order to render the bridge usable for quite a while based on the expenses that are likely to be incurred in case of an uncompetitive manner of consultation. The forces that affect the deck and its feature is more of hydrostatic with both lateral and vertical coefficients. The difference between these two forces causes an up thrust as water flows down the stream causing damage on the fastening points which are meant to hold the bridge parts together.

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