April 5, 2018

Seismic Load Consideration for Retaining Walls

RISAFoundation has the capability to consider seismic loading for retaining walls.

Retaining Wall Earthquake Loading1 300x240 2x

The Mononobe-Okabe formulation has been implemented. Though direct input of the maximum pressure at the top of the wall can also be defined to create the inverted triangular loading.

For details on the Coulomb calculations and the variation due to the Seed & Whitman adjustments please check out the Wall Footings – Design topic in the RISAFoundation help file.

RISA Help File

Tags: RISAFoundation, New, Retaining Walls

December 16, 2015 | RISA-3D, RISAFloor, Concrete, RISAFoundation, New

Concrete Design per ACI 318-14 Concrete Code now Available

The new ACI 318-14 code has been implemented into RISA-3D v14, RISAFloor v10, and RISAFoundation v8. To select this code for your design, simply choose them from the Codes tab of the Model Settings: One of the main changes for the 2014 ACI code is a change to the minimum flexural reinforcement for elevated slabs (RISAFloor ES) and mat slabs (RISAFoundation). Please see ACI 318-14 Sections 7.6.1 and 8.6.1 (and Chapter 13’s references to Chapter 7 and Chapter 8) for more information…

November 14, 2024 | Featured, Structural Engineering

Engineering Resilence: Lessons from Fall Hurricane Season

As structural engineers, the fall hurricane season presents unique challenges that push the boundaries of design. Hurricanes Helene and Milton, both from 2024, stand out for their rapid intensification and the vast areas they impacted. With Helene sweeping across Florida’s Big Bend and Milton ranking among the most intense Atlantic hurricanes in history, it’s clear that structural resilience is more important than ever. Here’s how engineers can dive into the technical details of hurricane-resistant design and take valuable lessons from these storms. 1. Wind Loads and Lateral Resistance Hurricanes like Helene and Milton bring with them fierce winds, often reaching over 140 mph, causing massive lateral forces on structures. Wind load analysis is one of the most important aspects of hurricane design, particularly for tall buildings and long-span structures. Engineers use software like RISA-3D to model these forces and design the structure's lateral load-resisting system (LLRS), which might include shear walls, braced frames, or moment frames. For example, in Helene’s path, structures with poorly designed lateral systems were more vulnerable to wind-related failures. By analyzing factors like gust effects and torsional irregularities, engineers can identify weak points and ensure a building’s frame and cladding systems remain intact under extreme wind…

April 7, 2020 | RISA-3D, Concrete, New, Shear Walls

Understanding Out-of-Plane Shear Capacity of Concrete Wall Panels

When designing concrete shear walls for lateral loading, RISA-3D includes design checks for both in-plane and out-of-plane shear. In the condition where a concrete wall is under both axial tension and out-of-plane shear, the out-of-plane shear limit state for a specific region within the concrete wall detailed report includes the details shown below: This limit state may cause users to ask the question: “why is the a phi*Vns term listed when no out-of-plane shear reinforcement is present?” The answer is that when calculating the out-of-plane shear capacity of the concrete wall, RISA-3D considers Shear Friction developed at the crack interface. ACI 318 code defines shear friction as the shear transfer across any given plane, such as an existing or potential crack, an interface between dissimilar materials, or an interface between two concretes cast at different times. In this case, the existing/potential cracks condition applies. When axial tension and out-of-plane shear are applied to the concrete wall, cracks will form across the wall thickness as explained by the simplified force diagram shown below: The shear sliding at the crack generates tensile forces Fs in rebar. In return, these tensile forces, Fs cause compression forces, Fc at the concrete crack interface. The…