Loads

In this worked example, we will work on a 2-story house to determine the seismic loads that are active on the building based on the seismic requirements of ASCE 7-16. If you'd prefer to learn by watching a video overview, check out this video.

1. Seismic Map Data

First, we identify the map data properties for our building. We can obtain the seismic map data from free tools such as the ASCE 7 Hazard Tool.

Assuming our project is located at 2951 E Grant Ave, Fresno, California, 93701, we can specify the standard we are using, risk category, site soil class, and desired load types into the tool.

Based on the report summary, we now enter the Short-Period Spectral Acceleration (S S), Long-Period Spectral Acceleration (S1), and Long-Period Transition Period (TL) onto the ClearCalcs Seismic Analysis Calculator. Note that the two figures above are taken from the ASCE 7 Hazard Tool, while below we jump back into ClearCalcs.

2. Key Building Properties

We now enter the key building properties based on the type of building we are designing for. Assuming the building is a 2-story building with 10 ft in height and 100,000 lbs (or, 100 kips) in seismic weight for each floor. We use light-frame (wood) walls sheathed with wood structural panels rated with shear resistance as our seismic force-resisting system.

3. Summary of Results

Once we have input all the necessary data into the Seismic Analysis Calculator, we can quickly glance at the summary of results we need for designing a house, such as the Design Short-Period Spectral Acceleration (SDS), Design Long-Period Spectral Acceleration (SD1), as well as the Seismic Design Category (SDC), which is a helpful parameter to determine which analysis you can use in a seismic calculation (e.g., the equivalent lateral force method).

The Seismic Analysis Calculator also generates the Seismic Base Shear (V) value for your design. Seismic Base Shear is the maximum experienced load based on the earthquake acceleration acting on a building. For example, based on our design, the total base shear value of 16.1 kip is distributed between the stories by 10.8 and 5.38 kip, respectively.

The diagram outlines how the lateral loads are acting on each level of the building, with the total base shear acting in the opposite direction.

Finally, the diagram also illustrates each level of the building with the associated height (10ft respectively) and the total height of the building, which is 20 ft. This is especially useful as ASCE 7-16 specifies building height limits for each seismic design category. For example, for our design with SDC D, the height limit is calculated here to be up to 65 ft.

This concludes our short tutorial on how to perform seismic analysis to ASCE 7-16.