Highway Engineering is a technical discipline branched from civil engineering involving planning, design, construction, operation and maintenance of roads, bridges and tunnels to ensure safe and effective transportation of people and goods. Highway engineering became prominent ahead of the second half of the 20th century after World War II. Road engineering standards continue to be improved. Road engineers must take into account future traffic flows, highway/intersection design, geometric design and alignment, highway pavement design and materials, structural design of pavement thickness, and pavement maintenance.
Video Highway engineering
History
The beginning of road construction can be determined in Roman times. With the technological advancement of the wagons pulled by two horses into a vehicle with the power equivalent of 100 horses, road construction must follow. The construction of modern highways did not begin until the late 19th century until the beginning of the 20th century.
The first study dedicated to highway engineering started in the UK with the introduction of the Transport Research Laboratory (TRL), in 1930. In the US, highway engineering became an important discipline with the passing of the Federal-Aid Highway Act of 1944, % of cities with populations of 50,000 or more. With the constant pressure of an increasingly large vehicle as time passes, improvements to the pavement are needed. With outdated technology, in 1958 the construction of the first toll road in Great Britain (Preston bypass) played a major role in the development of new pavement technologies.
The design policy standards used in the United States are usually based on the publication of the American Association of State Highway and Transport Officers as well as research published by the Transportation Research Institute, the Institute of Transportation Engineering, the Federal Highway Administration, and the Department of Transportation.
Maps Highway engineering
Planning and development
Road planning involves estimating current and future traffic volumes on the road network. Highway engineers seek to predict and analyze all possible civil effects of the road system. Some considerations are adverse effects on the environment, such as noise pollution, air pollution, water pollution, and other ecological impacts.
Financing
Developed countries are constantly confronted with the high maintenance costs of an aging transport highway. The growth of the motor vehicle industry and the accompanying economic growth has resulted in demand for safer, better performing, less dense roads. The growth of trade, educational, housing and defense institutions was largely derived from the government budget in the past, making public road financing a challenge.
The multipurpose characteristics of highways, economic environments, and technological advances in road pricing are constantly changing. Therefore, the approach to road financing, management, and maintenance is also constantly changing.
Environmental impact assessment
People's economic growth depends on building roads to improve mobility. However, roads planned, designed, constructed, and properly maintained can disrupt the social and economic characteristics of different community sizes. Common negative impacts on road construction include habitat destruction and biodiversity, air and water pollution, noise/vibration generators, destruction of natural landscape, and the destruction of social and cultural structures of people. Road infrastructure must be built and maintained with high quality and standards.
There are three main steps to integrate environmental considerations into planning, scheduling, construction, and maintenance of roads. This process is known as the Environmental Impact Analysis, or AMDAL, as it systematically deals with the following elements:
- Identify possible impacts on the natural and socio-economic environment
- Evaluate and quantify this impact
- Formulation of actions to avoid, mitigate, and compensate for anticipated impacts.
Highway security
The highway system generates the highest prices in human injuries and deaths, as nearly 50 million people are injured in traffic accidents each year, excluding 1.2 million deaths. Road traffic injury is the leading cause of accidental death in the first five decades of human life.
Safety management is a systematic process that seeks to reduce the occurrence and severity of traffic accidents. Human/machine interaction with road traffic systems is unstable and poses challenges for road safety management. The key to improving road system security is designing, constructing, and maintaining it to be much more tolerant of average human/machine interaction distances by road. Technological advances in road engineering have improved the design, construction, and maintenance methods used over the years. This progress has enabled newer road safety innovations.
By ensuring that all situations and opportunities are properly identified, considered, and implemented, they can be evaluated at every stage of highway planning, design, construction, maintenance and operation to improve the safety of our road system.
Design
The location, alignment, and shape of the most appropriate highway are selected during the design phase. The design of the highway involves consideration of three main factors (people, vehicles, and roads) and how these factors interact to provide safe highways. Human factors include reaction time for braking and steering, visual acuity for traffic signs and signals, and car-following behavior. Vehicle considerations include vehicle size and dynamics which are essential for determining maximum lane width and slope, and for design vehicle selection. Highway engineers design road geometry to ensure vehicle stability when negotiating curves and values ​​and to provide sufficient visibility to maneuver past the curves of a two-lane two-lane road.
Geometric design
Road and road transport engineers must meet many safety standards, services, and performance when designing roadways for the topography of a particular site. The geometric design of the highway mainly refers to the visible elements of the highway. Road engineers designing road geometry should also consider the environmental and social impacts of design on the surrounding infrastructure.
There are certain considerations that must be handled properly in the design process in order to successfully adjust the highway to the topography of the site and maintain its security. Some of these design considerations include:
- Design speed
- Design traffic volume
- Number of paths
- Service Level (LOS)
- Visibility Distance
- Alignment, super-elevation, and value
- Cross section
- Line width
- Horizontal and vertical restrictions
Highway operational performance can be seen through the driver's reaction to design considerations and interactions.
Materials
The materials used for road construction have evolved over time, dating back to the early days of the Roman Empire. Progress in methods that are characterized and applied to the pavement's structural design have accompanied progress in this material.
There are two main types of sidewalk surfaces - Portland cement concrete (PCC) and hot-mix asphalt (HMA). Below is a layer of material that provides structural support for pavement systems. The underlying surface may include an aggregate layer and subbase layer, or the treated base and subbase layer, as well as a natural or processed base subgrade. This treated coating can be treated with cement, treated with asphalt, or treated with lime for additional support.
Flexible sidewalk design
A flexible pavement, or asphalt, or asphalt usually consists of three or four layers. For four-tier flexible sidewalks, there are surface courses, basic courses, and subbase courses built on a compacted natural land subgrade. When building a flexible three-ply sidewalk, the subbase layer is not used and the base course is placed directly on the natural subgrade.
The surface layer of flexible pavement is constructed from hot-mix (HMA) asphalt. Unstabilized aggregates are commonly used for base lines; However, the basic course can also be stabilized with bitumen, Foamed Bitumen, & Roadstone Recycling & gt; Portland Cement, or other stabilizers. Subbases are generally constructed from local aggregate materials, while the topsoil is often stabilized with cement or lime.
With flexible pavement, the highest voltage occurs on the surface and the voltage decreases as the pavement depth increases. Therefore, high quality materials need to be used for surfaces, while lower quality materials can be used because of increased pavement depth. The term "flexible" is used because of the asphalt's ability to bend and damage slightly, then return to its original position because every traffic load is applied and removed. It is possible for this small deformation to be permanent, which can cause a shrink in the wheel track for a long time.
The service life of the flexible pavement is usually designed in the range of 20 to 30 years. The required thickness of each layer of flexible pavement varies greatly depending on the material used, the magnitude, the amount of repetition of the traffic load, the environmental conditions, and the desired service life of the pavement. Factors such as these are considered during the design process so that the sidewalks will take place for life designed without excessive distress.
Rigid pavement design
Rigid bridges are commonly used in building airports and major highways, such as those on interstate highway systems. In addition, they usually serve as heavy duty industrial floor plates, harbors and sidewalk ports, and park heavy vehicles or sidewalk terminals. Like flexible pavements, rigid road pavements are designed as all weather structures and durable to serve modern high-speed traffic. Offering high-quality riding surfaces for safe travel vehicles, they serve as a structural layer to distribute vehicle wheel loads in such a way that the induced voltage transmitted to subgrade ground is an acceptable quantity.
Portland cement concrete (PCC) is the most commonly used material in the construction of rigid pavement sheets. The reason for its popularity is due to availability and economy. Rigid pavements should be designed to bear the burden of frequent recurring traffic. A specially designed service life of rigid pavement is between 30 and 40 years, which runs about twice as long as the flexible pavement.
One of the major design considerations of rigid pavement is to reduce fatigue failure due to recurrent traffic pressures. Fatigue failure is common among major roads because a typical highway will experience millions of wheel carriers throughout its service life. In addition to design criteria such as traffic loads, tensile stress due to heat energy should also be considered. When pavement designs are running, many road engineers have noted that the pressure caused by heat on the rigid pavement can be as strong as that imposed by the wheel loading. Due to the relatively low tensile strength of the concrete, thermal stress is essential for rigid pavement design considerations.
Rigid rigidity is generally built in three layers - subgrade, base or subbase prepared, and concrete slabs. Concrete concrete is constructed according to the designed choice of plan dimensions for plate panels, directly affecting the intensity of thermal stresses occurring inside the sidewalk. In addition to plate panels, the temperature amplifier should be designed to control the crack behavior in the plates. Joint spacing is determined by the dimensions of the slab panel.
The three main types of concrete pavement commonly used are Jointed plain concrete pavement (JPCP), jointed reinforced concrete pavement (JRCP), and continental reinforced concrete pavements (CRCP). JPCP is built with a contractionary connection that directs the natural crack of the sidewalk. This sidewalk does not use reinforcing steel. JRCP is built with contraction and steel joints to control cracks from the sidewalk. High temperatures and moisture pressure inside the sidewalk create a crack, wherein the reinforcing steel holds tightly together. In transverse connections, a dowel rod is usually placed to help move the vehicle load through the crack. CRCP relies only on continuous reinforcing steel to withstand the transverse cracks of natural sidewalks together. Prestressed concrete sidewalks have also been used in the construction of highways; However, they are not as popular as the other three. The paired sidewalks allow for thinner slab thickness by partially or completely neutralizing thermal induced stresses or loads.
Flexible pavement overlay design
During flexible pavement service times, accumulated traffic loads may cause excessive rupting or cracking, inadequate driving quality, or inadequate skid resistance. These problems can be avoided by simply maintaining sidewalks, but the solution usually has excessive maintenance costs, or the sidewalks may have insufficient structural capacity for the projected traffic load.
Throughout the life of the highway, the level of serviceability is closely monitored and maintained. One common method used to maintain a highway service level is to place overlays on the sidewalk surface.
There are three common overlay types used on flexible pavements: asphalt concrete overlays, Portland cement concrete overlays, and very thin Portland cement concrete. The concrete layer in a conventional PCC layer is placed unaddressed over a flexible surface. The typical thickness of the ultra-thin PCC layer is 4 inches (10 cm) or less.
There are three main categories of flexible widening road design procedures:
- Component Analysis Design
- Deflection Based Design
Design of rigid pavement stretch
Toward the end of rigid pavement service life, a decision must be made to completely reconstruct the outdated pavement, or build an overlay layer. Considering overlays can be built on rigid pavements that have not reached the end of service life, it is often more economically attractive to apply overlay layers more often. The overlay thickness required for structural structural rigid pavements is much smaller than those that have reached the end of service life. Rigid and flexible overlays are both used for the rehabilitation of rigid pavements such as JPCP, JRCP, and CRCP.
There are three subcategories of rigid pavement overlay that are organized depending on the bonding conditions on the sidewalk overlay and the existing slab interface.
- Overlays are bound
- Unbounded expanse
- Partially bonded shear
Drainage system design
Designing for proper drainage of the highway system is critical to their success. Regardless of how well other aspects of the road are designed and built, adequate drainage is mandatory for roads to survive throughout its services. Excess water in the highway structure can certainly lead to premature failure, even if the failure is not a disaster.
Each road-specific drainage system is location-specific and can be very complicated. Depending on the geography of the region, many methods for proper drainage may not apply. Highway engineers must determine the situation in which a particular design process should be applied, usually a combination of several appropriate methods and materials to direct water away from the structure.
Erosion control is an important component in the design of road drainage systems. Surface drainage should be allowed for deposition to flow away from the structure. The highway should be designed with a slope or crown so that the runoff water will be directed to the shoulder of the road, to the gutter, and away from the location. Designing drainage systems requires predicted runoff and infiltration, open channel analysis, and culvert designs to direct surface water to the right location.
Construction, maintenance and management
Highway construction
Road construction is generally preceded by detailed surveys and basic soil preparations. Methods and technologies for building roadways have evolved over time and become more sophisticated. These technological advances have increased the level of expertise required to manage road construction projects. These skills vary from project to project, depending on factors such as the complexity and nature of the project, the contrast between new construction and reconstruction, and the differences between urban areas and rural area projects.
There are a number of road construction elements that can be broken down into technical and commercial elements of the system. Some examples of each are listed below:
- Technical Elements
- Materials
- Quality of material
- Installation techniques
- Traffic
- Commercial Elements
- Understanding the contract
- Environmental aspects
- The political aspect
- Legal aspects
- Public awareness
Typically, construction begins at the lowest elevation of the site, regardless of project type, and moves upwards. By reviewing the geotechnical specifications of the project, information is provided about:
- Existing land conditions
- Equipment required for excavation, smoothing, and transportation of materials to and from the site
- Property material to be excavated
- Drying needs are required for jobs under the class
- Closes the terms for excavation protection
- Quantity of water for compaction and dust control
Construction of subbase course
The subbase course is a layer designed for carefully selected materials that lie between the subgrade and the sidewalk lane. Subbase thicknesses are generally in the range of 4 to 16 inches, and are designed to withstand the required structural capacity of the sidewalk.
Common materials used for subbase of highways include gravel, crushed stone, or base soil stabilized with cement, fly ash, or lime. The permeable subbase course becomes more common because of its ability to drain infiltration water from the surface. They also prevent subsoil from reaching the sidewalk surface.
When the cost of local materials is too expensive or material needs to improve the structural bearing of the sub-base is not available, road engineers can increase the underlying soil's carrying capacity by mixing in Portland cement, foaming asphalt, or using stabilized polymeric soils such as cross-styrene acrylic polymers increasing the California Bearing Ratio from in-situ materials by a factor of 4-6.
Construction of base field
The base course is a section of the sidewalk located directly below the surface only. If there is a subbase course, a basic course is built right on this layer. If not, it is built directly on the ground ground. The typical base line thickness ranges from 4 to 6 inches and is governed by the underlying layer properties.
Heavy loads continue to be applied to the sidewalk surface, and the base layer absorbs most of this pressure. Generally, the base line is constructed with an untreated aggregate that is not treated like crushed stone, slag, or gravel. The base course material will have stability under construction traffic and good drainage characteristics.
The basic course materials are often treated with cement, asphalt, calcium chloride, sodium chloride, fly ash, or lime. This treatment provides enhanced support for heavy loads, the vulnerability of frost, and serves as a moisture barrier between the base and surface layers.
Surface Construction
There are two types of sidewalk surfaces most commonly used in highway construction: hot-mix asphalt and Portland cement concrete. This pavement surface surface provides a smooth and secure ride surface while simultaneously transfering heavy traffic loads through the various base courses and to the underlying subgrade ground.
Hot-mix asphalt (HMA) layer
Hot-mix asphalt surface courses are referred to as flexible pavements. The Superpave system was developed in the late 1980s and has offered changes to design approaches, mixed designs, specifications, and quality testing materials.
The development of effective and durable asphalt pavement requires experienced construction crews, committed to quality control and their work equipment.
Construction problems:
- Asphalt mixed segregation
- Layout
- Compaction
- Joint
A major coating is the low viscosity bitumen applied to the base course before laying the HMA surface course. This layer binds loose material, creating a cohesive layer between the base layer and the asphalt surface.
A tack coat is a low viscosity asphalt emulsion used to create bonds between existing pavement surfaces and new asphalt overlays. Tack coats are usually applied to adjacent sidewalks (curbs) to help bond HMA and concrete.
Concrete Portland cement (PCC)
The Portland cement concrete surface course is referred to as rigid pavement, or concrete pavement. There are three general classifications of plain jointed sidewalks, jointed plain, reinforced jointed, and continuously reinforced.
Traffic loads are transferred between sections when larger aggregates in the PCC blend interlock, or through load transfer devices in the transverse surface joints. The Dowel rod is used as a load transfer device for efficiently transfering load across transverse connections while maintaining horizontal and vertical alignment of joints. Tie-bars are defective steel bars placed along longitudinal connections to hold adjacent sidewalks in place.
Highway maintenance
The overall objective of road maintenance is to repair damage and preserve pavement structures and serviceability. Defects must be defined, understood, and recorded to create an appropriate treatment plan. Maintenance planning solves the optimization problem and can be predicted. In empirical predictive maintenance planning, data-driven methods provide more accurate results than mechanical models. Different defects between flexible and rigid pavement.
There are four main purposes of road maintenance:
- repair of functional sidewalks defects
- extend the functional and structural service life of the sidewalks
- maintain security and road signs
- keeps a backup of the road in acceptable condition
Through routine maintenance practices, the road system and all its components can be maintained to their original state, as they are built.
Project management
Project management involves organizing and structuring project activities from start to finish. Activities may include infrastructure development such as roads and bridges or large and small maintenance activities associated with the construction of such infrastructure. All projects and activities involved should be handled professionally and completed within deadlines and budgets. In addition, minimizing social and environmental impacts is critical to the success of project management.
See also
Highway and parkway
- Access-controlled highway
- Interstate Toll System
- Restricted access roads
- Parkway
- Strategic Highway Network
- TexSys - Texas Expert System for Hot-Mix Asphalt (HMA) selection based on TxDOT (2004).
Design and consideration
References
External links: road design standards
- Australia
- United Kingdom
- [1]
- United States (AASHTO)
- Arizona (USA)
- California (USA)
- Connecticut (USA)
- Kentucky (USA)
- New York (USA)
- New Jersey (USA)
- Texas (USA)
- Wisconsin (USA)
Further reading
- The Human Factor for Highway Engineers at Googlebooks
Source of the article : Wikipedia
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