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Building Brilliance: Harnessing RAM Concept for Innovative Structural Design

Pietro Zini

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In the dynamic field of structural engineering, my journey as a lead structural engineer has been significantly impacted by the transformative power of software solutions such as RAM Concept. A powerful finite element method (FEM) application, it is mainly known for the design and analysis of post-tensioned and reinforced concrete floors and foundations.

In this blog post, I will delve into the more versatile applications of RAM Concept, specifically its role in the design of restrained retaining walls, the evaluation of pile foundation capacities for pool structures, and the seamless transfer of foundation designs from the RAM Structural System platform. It is important to note that while the design of retaining walls is not optimized in RAM Concept, the software can perform most of the analysis and design tasks.

This article highlights the exceptional versatility of RAM Concept, empowering structural engineers to optimize designs in ways that conventional structural software solutions cannot achieve. Unlike other technology that might provide basic foundation design capabilities, RAM Concept dives deeper into the intricacies of structural analysis and design. Its advanced algorithms and comprehensive features allow engineers to model complex interactions between different components of a structure, such as slabs, beams, columns, and walls, with precise detail. Other software often falls short when handling intricate design scenarios or specific structural configurations. They may lack the specialized capabilities necessary to accurately simulate real-world conditions, such as nonlinear behavior, dynamic loads, or unique material properties.

Utilization of RAM Concept in Retaining Wall Design

When discussing restrained retaining walls, one particular project that stands out in my past experience involved the design of a complex retaining wall system for a high-rise building. The task was formidable, demanding not only technical expertise, but also innovative thinking to ensure structural integrity. RAM Concept emerged as a game-changer. Its intuitive interface and powerful analysis features enabled us to model and analyze different scenarios efficiently. I vividly recall a critical juncture when we had to address potential stability issues arising from restraints tied back into the high-rise’s columns. Leveraging RAM Concept’s capabilities, we refined our designs, meticulously considering factors like restraint axial loads and load distribution, with unprecedented precision. Let’s dive into the details.

The design and concept were simple. We started by drawing the walls as slabs with the desired thickness, and we placed the line and point supports wherever the retaining wall had to be restrained. In my example shown in Fig.1 below, I used both types of supports–a line support to represent a wall return restraint on the right side, and a point support to represent a beam to support the wall on the left side. The bottom line support denotes the wall restraint provided by footings, which obviously should always be present. Notably, each type of restraint is assigned in all directions, providing essential data for calculating these members later.

Fig. 1 Line and point supports for retaining wall restraint

With this initial step complete, I could now assign the loads. RAM Concept does not include built-in earth retention loads (H); therefore, I needed to add them manually in the “Criteria > Loadings” tab, along with the corresponding load combinations in the “Criteria > Load Combos” tab per ASCE 7-16.  Additionally, it is important to note that RAM Concept assumes that gravity loads are in the downward Z direction. Therefore, I had to set all the self-dead load factors to zero and create my own self-weight loads. In this example, I did not account for any self-weight of the wall. However, if you intend to apply these loads, they should be applied at mid-slab depth; otherwise, the eccentricity will introduce a self-weight moment to the wall.

Fig. 2 Manual implementation of loading conditions

In this example, I’ve also manually added wind to account for the wind pressure applied on the small cantilever spanning above the restraints. Once this step is completed, I proceeded to draw the loads onto the model.

For earth retention, the loading condition typically involves a triangular distribution that increases with depth. Notably, RAM Concept offers a method to incorporate this loading condition that many may not be aware of.

To add this type of loading condition, you first need to manually calculate the maximum soil pressure at the heel. Then, this pressure should be added as an area load into the model, starting clockwise from the top left snap point, as illustrated in Fig. 3.

Fig. 3 Triangularly distributed area load

The design strips and mat reinforcement settings are standard procedures in concrete slab design. However, it’s essential to note that, in this case, the top reinforcement depth should adhere to the typical standard cover for concrete over soil in both mat and strip settings.

Fig. 4 3D element of the retaining wall structure

After running the model calculations, I performed typical slab checks, such as minimum and maximum moment diagrams, to assess wall reinforcement behavior and deflections. On top of this, I can also get the necessary data to calculate the restraint bodies. In this example, I accessed the standard reaction plans by clicking the manually created load combo in the “Load Combinations” menu tab to display all the acting forces on the placed restraints (Fig. 5). The forces at the bottom of the wall can be used for footing sliding checks, but based on my personal experience, the presence of a slab on grade typically is enough to safely brace the wall at the base.

Please be aware that RAM Concept does not account for movement on the z-axis or P-delta effects. Therefore, additional considerations will be necessary for cases involving lateral or heavy axial loads applied to the retaining wall.

Fig. 5 Standard reaction plan for factored load combination

Easy Pile Layout Design and Capacities with RAM Concept

Other capabilities of RAM Concept include evaluating pile foundation capacities for pool structures. These types of projects demand a meticulous approach that considers pile layout optimization due to constant modifications from ownership, and ensures the piles meet the required capacity standards, often determined by project specifications. In these instances, RAM Concept proved invaluable, providing insightful analysis that guided our decisions and ultimately ensured the foundation was structurally sound.

Below, I will further explore how RAM Concept offers a streamlined solution tailored to efficiently address such challenges in pile foundation design.

Let’s start with a typical slab of the desired thickness. For the pile foundation, place circular columns beneath the slab, ensuring their diameter matches that of the piles. I typically use construction lines during this design phase to assist in accurately placing the piles for optimal layout and structural integrity.

Fig. 6 Standard pool foundation and pile layout

In this type of design, we do not use specific loading or load combinations because the concrete walls and pool stairs are classified as dead load, while the water is considered live load unreducible. The software does not automatically calculate these loads, but they can easily be determined manually using the relative densities and pool dimensions. For pools, I like to leverage RAM Concept’s capability to overlay loads by adding them together once I know the typical step height. The software then processes this information to account for each concrete layer.

Fig. 7 Dead load plan

Similar to the previous retaining wall design, I won’t delve into the design strips and mat reinforcement since it follows a standard slab design procedure. However, it’s always essential to account for the typical reinforcement depth, considering both the concrete on soil and concrete on water reinforcement cover for both mat and strip settings.

In this instance, pile reactions will be considered part of the service design and will need to be plotted. In the menu tab on the left, access “Rule Set Design > Service Design > Status Plan.” Right-click on the plan and select “Plot.” Refer to Fig. 8 below for the plot settings.

Fig. 8 Plot settings for service reactions.

Once this process is completed, you can compare the Fz reaction with your pile capacities. If these values do not meet the required standards, you can easily return to the plot and adjust your pile layout accordingly. This approach can save you valuable time and effort, especially when dealing with more complex pile designs.

Typical Foundation Design Transfer from RAM Structural System to RAM Concept

I’m sure many of you are familiar with RAM Structural System and its ability to transfer mat foundation designs to RAM Concept. But did you know that you can further modify these designs into systems of strip and square footings within RAM Concept?

By doing so, you can easily adjust sizes based on transferred gravity and lateral loads. Let me demonstrate this powerful capability.

Since this is a discussion focused on RAM Concept, I won’t delve into the previous steps of the RAM Structural System model I created. As shown in Fig. 9 below, we have a basic structure with both gravity and lateral loads, along with a rectangular mat footing at the base.

Fig. 9 Ram Structural System 3D model.

After completing the typical design steps in RAM Concrete Analysis and Concrete Walls to properly transfer gravity and lateral loading onto our mat footing, open the design in RAM Concept. Upon opening, the design initially resembles a standard rectangular mat. However, by incorporating a slab opening, we can easily transform it into a rectangular strip footing system as in Fig. 10.

Fig. 10 Strip footing system

The eccentric appearance of the footings in Fig. 10 is due to drawing this model by hand without adhering to standard dimensions. To add square footings under columns, simply incorporate a drop cap of the desired size, ensuring its priority is set higher than other components on the plan for proper recognition. Next, standard foundation design procedures, including soil bearing design plans, should be implemented. An essential feature to highlight relates to lateral design, particularly with overturning moments. As you may know, these moments can generate significant uplifts or downward forces on shear wall footings. By leveraging the drop cap feature, you can strategically add square footings to shear wall edges to counteract these forces. (See Fig. 11.)

Fig. 11 Completed footing system design in RAM Concept

While these processes may initially seem time-consuming and labor-intensive, they are more efficient than you might expect. Given the dynamic nature of projects and the likelihood of changes, modifying existing design models with software like RAM Concept is far simpler than manually adjusting spreadsheets or performing hand calculations. These examples underscore the versatility of FEM software like RAM Concept, showcasing its applicability to a diverse range of design challenges beyond conventional concrete slab structures. I encourage you to explore the software’s niche applications and discover its potential in addressing other specialized engineering needs.

Links:

SWS Webinar Link

RAM Concept Blog (Qian) Link

STAAD Foundation Blog (Shyla) Link

Upcoming Webinar | Improving Canadian Structural Design – Leveraging the Latest Canadian Codes in STAAD and RAM Link

For all inquiries, you can contact Pietro Zini at pietro.zini@bentely.com or  LinkedIn.

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