Approach
Reliable structural design is an integral part of every qualified building. At XIA Structural Engineers, we have always asked ourselves to customize a reasonable and reliable structural plan for each project with scientific and rigorous methods, an attitude of being unafraid of challenges, and the spirit of craftsmanship for excellence.
After completing hundreds of projects, we have further refined our structural design process. For different building types, we consciously adjust and improve the entry angle of the scheme design. Below are some of our design ideas for high-end custom homes and apartment buildings.
Type 1: Custom Homes
In such projects, priority is given to the usability of the building, such as level and uniform surfaces, the firmness of the floor, and the sense of safety in extreme events such as earthquakes. While construction cost is not the first priority, we can pay special attention to specific locations to effectively improve the performance of the building.
Listed below are some frequently asked questions, and we care about much more than that.
Issue 1: Uneven Floor Surfaces.
Introduction:
In high-end custom homes, long-span beams and joists are often encountered. In this case, the floor will deflect and cause problems such as Hardwood flooring misalignments, Nailing squeaks Discomfort and Floor vibrations.
Figures 1 and 2 show typical scenarios for wood frame floors in plan and perspective views.
1. Without engineering optimization, the beam will deflect first.
2. The end of the joist connected to the beam is deflected together with the beam.
3. The joist itself also deflects, resulting in a combined deflection of the beam and joist deflection.
4. You will have the final deflection shape in the profile view (Figure 3).
Minimum Code:
For a 20 ft span of the beam and 20 ft span joists hanging on the beam, the total allowable deflection by the code is 20ft/180/2 + 20ft/180 = 1.6".
Our Approach:
At XIA Structural Engineers, we are committed to minimizing floor distortion.
We consider the Combined Deflection very carefully on a case-by-case basis.
For the beam, we browse and select the beam with the minimum deflection, or use Camber for GLB and Steel beams to offset the deflection.
Our goal is to control the max deflection on the floor within 1/4"(Figure. 4).
Issue 2: Window vibration during a wind gust.
Introduction:
A wind Gust is a sudden, brief increase in wind speed.
When you have a big, tall window, it is attached to the king studs on both sides. When the king studs are tall, they are comparably more flimsy.
During a wind gust, the window can shake, making people feel uncomfortable or even unsafe.
Code Minimum:
The code doesn't specify the problem.
Our approach:
We design the king studs strongly and detailed the connection between the king studs and the roof framing. Strong king studs ensure robustness and almost completely eliminate vibration, which gives large windows a solid feeling.
Issue 3: Story drift(deformation) during an earthquake
Introduction:
California Building Code limits the earthquake drift to 0.02 times the story height H. For high-end residential projects, the lobby area is often over 12 feet or two stories high.
Code Minimum:
Assuming the ceiling is 20 feet high, the allowable drift is 20ft x 0.02 = 0.4 ft. This is sure to shatter expensive windows and damage ceilings and architectural components.
Our approach:
We paid particular attention to making the lateral resistance system stiffer in these locations. By limiting seismic deformation to the manufacturer's limits, we can reduce most damage to architectural components.
Type 2: Apartment Buildings
Introduction:
In such projects, the priority is the speed of construction and the economics of construction. Since apartment buildings always have repetitive layouts, what we do in one place is repeated many times. We take value engineering very seriously because one change affects the entire building.
We design and experiment with various ways to lay out the framing in order to find the best solution for the economical use of the materials and faster construction.
Our Approach:
Below, A, B, and C are comparison framings for typical apartment buildings.
Layout A:
Very efficient except that there is only one beam, where most of the joists are.
Layout B:
The joists in this layout are repetitive along the long direction, but the joist and beam are hanger connections, which are more time-consuming for construction. In addition, this layout requires more beams and posts which will result in high material costs.
Layout C:
This is the most straightforward layout but is limited by the span of the joist. If the span is long, heavier joists or more expensive TJI joists are needed. This layout is the fastest for construction.
