What is the requirement of curves on the road? What are the different types of curves?

Civil Engineering - Interview Questions

The curves on roads are used to change the direction of the road and to provide a smooth transition between straight sections. They are important for road safety as they help drivers to maintain control of their vehicles, especially at high speeds.

1. Horizontal Curves

* Simple circular curve

* Compound Road Curves

* Reverse Curve

* Track transition curve

* Spiral curves

2. Vertical Curves

* Summit Curves

* Valley/ Sag Curve

Simple circular curve : It is a curve consisting of a single arc with a constant radius connecting the two tangents. It is a type of horizontal curve used most in common. A simple arc provided in the road or railway track to impose a curve between the two straight lines is the simple circular curve. The smaller is the degree of curve, the flatter is the curve and vice versa. The sharpness of a simple curve is also determined by radius R. Large radius are flat whereas small radius are sharp. A simple curve is normally represented by the length of its radius or by the degree of curve

Compound Road Curves : It is a curve made up of two or more circular arcs of successively shorter or longer radii, joined tangentially without reversal of curvature, and used on some railroad tracks and highways as an easement curve to provide a less abrupt transition from tangent to full curve or vice versa. Since their tangent lengths vary, compound curves fit the topography much better than simple curves.

Reverse Curve : A reverse curve is composed of two or more simple curves turning in opposite directions. Their points of intersection lie on opposite ends of a common tangent, and the PT of the first curve is coincident with the PC of the second. This point is called the point of reverse curvature (PRC). A reverse curve is composed of two arcs of equal or different radii bending or curving in opposite directions with common tangent at their junction, their centers being on opposite sides of the curve.

Track transition curve : A track transition curve, or spiral easement, is a mathematically-calculated curve on a section of highway, in which a straight section changes into a curve. It is designed to prevent sudden changes in lateral In plane (viewed from above), the start of the transition of the horizontal curve is at infinite radius, and at the end of the transition, it has the same radius as the curve itself and so forms a very broad spiral.

Spiral curves : Spiral curves are generally used to provide a gradual change in curvature from a straight section of road to a curved section. They assist the driver by providing a natural path to follow. Spiral curves also improve the appearance of circular curves by reducing the break in alignment perceived by drivers. The use of a spiral is about making the road or track follow the same form that the vehicle naturally takes. In a car, you don’t go directly from going straight to fully turning. There is a transition area where you slowly turn the steering wheel. On highways, the lanes are wide enough that you can drive a spiral just by moving from one side of the lane to the other.

Summit Curves : Summit curves are vertical curves with gradient upwards. Sight distance requirements for the safety is most important on summit curves. The stopping sight distance or absolute minimum sight distance should be provided on these curves and where overtaking is not prohibited, overtaking sight distance or intermediate sight distance should be provided as far as possible. When a fast moving vehicle travels along a summit curve, there is less discomfort to the passengers.

Valley/ Sag Curve : Valley curves or sag curves are vertical curves with convexity downwards. In valley curves, the centrifugal force will be acting downwards along with the weight of the vehicle, and hence impact to the vehicle will be more. This will result in jerking of the vehicle and cause discomfort to the passengers. Thus the most important design factors considered in valley curves are- impact-free movement of vehicles at design speed and availability of stopping sight distance under headlight of vehicles for night driving. The valley curve is made fully transitional by providing two similar transition curves of equal length.

Recently Updated Interview Questions in Civil Engineering

What are the advantages and disadvantages of using concrete as a building material?

Concrete is a widely used building material with several advantages and disadvantages. Its popularity stems from its versatility, strength, and durability. However, like any material, it has limitations and potential drawbacks. Here are the advantages and disadvantages of using concrete as a building material:

Advantages :

* Strength and Durability : Concrete is renowned for its high compressive strength, making it suitable for supporting heavy loads and resisting structural stresses. It can withstand a wide range of environmental conditions, including fire, wind, and moisture, without significant deterioration.

* Versatility : Concrete can be molded into various shapes and sizes to accommodate diverse architectural designs. It can be used for walls, slabs, columns, beams, and more, allowing for flexible construction possibilities.

* Longevity : Properly designed and maintained concrete structures can have a long service life, often exceeding 50 years or more. This longevity reduces the need for frequent repairs or replacements.

* Fire Resistance : Concrete is inherently fire-resistant and does not combust. It can provide valuable fire protection in buildings, helping to contain fires and limit their spread.

* Thermal Mass : Concrete's thermal mass properties allow it to absorb, store, and slowly release heat, contributing to energy efficiency in buildings. This can help regulate indoor temperatures and reduce heating and cooling costs.

* Sound Insulation : Concrete's density makes it an effective sound barrier, reducing the transmission of noise between rooms or from the exterior. It is commonly used in multi-unit residential and commercial buildings for this reason.

* Low Maintenance : Compared to some other materials, concrete requires relatively low maintenance. It does not rot or decay, and minor surface repairs are typically manageable.

Disadvantages :

* Weight : Concrete is heavy, which can pose challenges in certain applications. The weight of concrete structures may require more robust foundations and structural support systems, adding to construction costs.

* Cracking : Concrete is susceptible to cracking, especially if not properly designed, mixed, or cured. These cracks can compromise the structural integrity and aesthetics of a building. Control joints and reinforcement are used to mitigate cracking.

* Environmental Impact : The production of cement, a key component of concrete, generates a significant amount of carbon dioxide (CO2) emissions, contributing to environmental concerns. Efforts are being made to reduce the carbon footprint of concrete through alternative materials and manufacturing processes.

* Cost : High-quality concrete and skilled labor for formwork, pouring, and finishing can be expensive, particularly in comparison to some alternative building materials.

* Limited Insulation : Uninsulated concrete walls can have poor thermal insulation properties, which may necessitate additional insulation layers to meet modern energy efficiency standards.

* Curing Time : Concrete typically requires time to cure and reach its full strength. This can affect construction schedules, leading to longer project timelines.

* Aesthetics : Concrete is often considered less visually appealing than some other materials, although decorative finishes and treatments can enhance its appearance.

Metal and Steel Structures

Q1: What are the main types of steel used in construction?

A1: The main types of steel used in construction are carbon steel, alloy steel, stainless steel, and galvanized steel.

Q2: What are the advantages of using steel in building construction?

A2: Advantages of using steel in building construction include high strength-to-weight ratio, durability, speed of construction, adaptability, recyclability, and resistance to fire, pests, and rot.

Q3: What is the difference between hot-rolled and cold-formed steel sections?

A3: Hot-rolled steel sections are produced by heating steel to high temperatures and rolling it into the desired shape, while cold-formed steel sections are made by bending or rolling steel at room temperature without the need for heating.

Q4: What are the common types of connections used in steel structures?

A4: Common types of connections used in steel structures include bolted connections, welded connections, and riveted connections.

Q5: What factors affect the design of steel structures?

A5: Factors affecting the design of steel structures include the type and magnitude of loads, the material properties, the structural system and member sizes, the type of connections, the corrosion protection methods, and the applicable building codes and standards.