From visible to cantilever staircases, this comprehensive guide provides innovative practices and professional advice on how to calculate, design, and build a concrete staircase.
A concrete staircase serves an essential function, connecting different levels of a building while also becoming a significant architectural element.
In this article, we will delve into the details of calculating, designing, and constructing concrete staircases, highlighting innovative practices and modern trends in the sector.
Designing reinforced concrete staircases
For the design of a reinforced concrete staircase, design details are essential to ensure that the staircase seamlessly fits the surrounding environment and the functional needs of the building. There are various aspects to consider, such as the ratio of rise and run, accessibility, and architectural appearance.
Let’s explore these aspects in more detail.
Rise and Run Ratio
The rise and run ratio is one of the fundamental principles in the design of reinforced concrete staircases. This ratio concerns the vertical distance (rise) between two consecutive steps and the depth (run) of each step. Properly defining this ratio is crucial to ensure that the staircase is safe, comfortable, and compliant with design standards.
To better understand the importance of this ratio, let’s look at the formulas and calculations involved:
Rise: Rise represents the vertical distance between two consecutive steps and is generally measured from the surface of one step to the surface of the next step. This value is essential for calculating the total number of steps in a staircase. The formula to calculate the total rise is as follows:
R = H/N
- R – rise of each step,
- H – total height of the plane on which the staircase must be built,
- N – the number of steps.
Run: Run represents the depth of the step and is measured from the front edge of one step to the front edge of the next step. The formula to calculate the total run is as follows:
R = L/N
- R – run of each step,
- L – the total length of the space available for the staircase,
- N – the number of steps.
Having defined what rise and run are, let’s look at the most commonly used formula for the rise and run ratio calculation. The formula is that of the architect François Blondel, dating back to the year 1675.
Based on his insight, it is deduced that the correct rise and run ratio should be:
2R + R = 62/64 cm
From this formula, it is deduced that the ideal rise is approximately 16 cm, while the ideal run is 30 cm.
Indeed, a staircase with an appropriate rise and run ratio will provide a comfortable experience for its users. A ratio that is too large would make the ascent tiring, while one that is too small might increase the risk of tripping. Designing a staircase with the right rise and run ratio requires a balance between aesthetic design and functionality.
The use of BIM software allows architects and engineers to simulate various combinations of rise and run to find the optimal one for the project. These tools calculate the height and depth of the steps accurately, taking into account all project specifications. This ensures that the staircase complies with safety regulations and aesthetic expectations.
Accessibility and Safety
The staircase must be designed to be accessible to all individuals, regardless of their physical abilities. This means that accessibility and safety guidelines must be considered. Staircases should have handrails to facilitate grip, non-slip steps, and adequate lighting. The width of the staircase is also crucial to allow smooth and safe passage for multiple individuals simultaneously.
Harmony with the Environment
A well-designed reinforced concrete staircase should seamlessly integrate into the surrounding environment and the overall building design. Architects must consider the material, color, and style of the staircase to ensure it harmoniously blends with the surrounding architecture. A well-designed staircase can become a prominent element in the overall building design.
Compliance with Building Regulations
Compliance with local and national building regulations is crucial in the design of reinforced concrete staircases. These regulations establish the minimum requirements for staircase safety and accessibility. Architects and engineers must be aware of these regulations and ensure that the project is in full compliance.
Materials and Construction Techniques
The choice of materials and construction techniques is another crucial aspect of the design of reinforced concrete staircases. The concrete used must be of high quality and adequately reinforced to ensure the strength and durability of the staircase over time. Structural design and the placement of reinforcements must be carefully studied to prevent structural failures or damage, as specified in the following paragraphs.
For more information on these aspects, I recommend reading the in-depth article “How to Design a Staircase: Criteria, Regulations, and Downloadable Examples.”
Types of Reinforced Concrete Staircases
One of the most important decisions in the design and construction of reinforced concrete staircases is the type choice. There are several types of staircases, each with specific characteristics suitable for different contexts and needs. In this section, we will explore the main types of reinforced concrete staircases, highlighting their peculiarities and advantages.
- Straight stairs – Straight stairs are the most common and straightforward to design and build. They feature steps arranged in a straight line, providing direct access from one point to another. These stairs are ideal for rectangular or square spaces and are widely used both indoors and outdoors.
- Spiral stairs – Spiral stairs are characterized by a circular or helical shape. They are often chosen to save space indoors or to create distinctive architectural elements outdoors.
- Cantilever stairs – Cantilever stairs feature a lateral supporting structure, creating the illusion that the steps float without visible supports. This modern and elegant design is often used in contemporary architecture and requires high-quality reinforced concrete and careful structural design.
- Fan stairs – Fan stairs open from a central point, expanding outward in a manner similar to the spokes of a wheel. This design is often used to create a visual impact and can be adapted to both indoor and outdoor spaces.
- Self-supporting stairs – Self-supporting stairs are designed not to require additional support, such as walls or columns, to support their structure. They are often used in modern architecture and require advanced structural engineering to ensure stability.
- Troweled concrete stairs – Troweled concrete stairs feature a smooth and uniform surface achieved by applying a layer of trowel or epoxy resin. This design gives them a contemporary look and an elegant finish.
- Modern reinforced concrete stairs – Modern reinforced concrete stairs follow contemporary architectural styles. They may feature innovative shapes, high-quality materials, and minimalist design. They are often used for advanced architectural projects.
- Prefabricated reinforced concrete stairs – Prefabricated stairs are manufactured in a factory and then transported to the construction site. They are available in various shapes and sizes, allowing for greater construction efficiency and shorter installation times. They are suitable for both indoor and outdoor use.
- Sloping slab stairs – Sloping slab stairs feature inclined steps and are often used in limited space areas. The structure requires careful design to ensure stability and safety.
- Knee-beam stairs – Knee-beam stairs incorporate a horizontal element that extends from the staircase’s structure, providing additional support and stability. They are often used in cantilever stairs or complex designs.
Structural calculation of reinforced concrete staircases
The structural calculation of reinforced concrete staircases is a fundamental process in the field of civil engineering and architecture. The accurate design of stairs requires a deep understanding of the forces, loads, and stresses acting on the structure. In this context, the structural design of a staircase can be divided into several key steps:
Design of the support section
In the first step of the structural calculation, you begin with the conditioned design of the most stressed support section. This section is crucial because it receives significant loads from the sloping slab and must be designed to withstand these loads. Data such as bending moment, section dimensions, and material characteristics are considered.
Design of the span section
In the second step, the focus is on designing the span section, which includes the steps and other structural elements. It is essential to define the reinforcement needed to ensure structural strength. Once again, data such as bending moment, section dimensions, and materials are considered.
Here, detailed evaluations of the designed sections are performed, comparing internal stresses with the material’s resistance capacity. This step is crucial to ensure that the staircase is safe and able to withstand the expected loads.
Calculation of resisting moment diagrams
This step involves determining how bending moments vary along the length of the staircase. Resisting moments must be calculated for each critical section of the staircase to ensure it can withstand stresses without failing.
To perform these calculations, specific formulas and structural design considerations are used. Regulations and safety factors are applied to ensure that the staircase meets safety standards and building codes. It is essential to consider both permanent and variable loads, as specified in the Technical Building Regulations.
The structural calculation of reinforced concrete staircases requires advanced knowledge of civil engineering and design practices. It is important to ensure that the staircase is structurally robust and can guarantee user safety.
Using BIM Software
Through BIM software for structural analysis, it is possible to create detailed virtual models of the staircase and consider all relevant factors. Some advanced BIM software has an integrated finite element solver, offering specific functionality for the structural calculation of stairs.
The main advantage of using a BIM software lies in the ability to simulate the structural behavior of the staircase in different situations, including maximum expected loads and dynamic loads. This simulation allows for design optimization and minimizes margin of error.
In conclusion, the calculation of a reinforced concrete staircase requires a thorough assessment of loads, adherence to project specifications, and the use of advanced software like BIM. Engineers must be able to apply the appropriate formulas to determine the strength and safety of the structure, ensuring that the staircase is both functional and aesthetically pleasing. Science and engineering come together to create reliable and durable reinforced concrete stairs.