Seismic Design Requirements for Steel Frame Structure Buildings

Steel structures constructed in seismic zones must meet the following design requirements:

1. For seismic fortification levels of 7 or higher, horizontal bracing should be installed around the perimeter sections of the truss within its support plane.

Theoretical calculations indicate that horizontal bracing enhances the truss's lateral seismic performance. For perimeter-supported trusses, three types of chord member configurations exist for the bracing plane:

(1) Orthogonal-orthogonal type: Diagonal members are installed within the peripheral grid to form a closed system.

(2) Orthogonal-oblique type: Horizontal members are arranged along the boundary to form a closed system.

(3) Triaxial type: The support plane itself is composed of geometrically stable triangles, thus requiring no additional bracing.

2. The slenderness ratio of members within the peripheral 2–3 grid zones shall not exceed 180. This is because the chord members along the perimeter of the space frame experience relatively small internal forces under static loads. However, under seismic loads, the dynamic-to-static force ratio (i.e., the ratio of seismic effects to static effects) for perimeter members is often greater than 1, frequently causing a change in the sign of internal forces. Therefore, regardless of whether the member is subjected to compression or tension, its allowable slenderness ratio shall be determined based on compression conditions.

3. For roof systems with purlin systems, purlins must be securely connected to the space frame and have sufficient support length. If welded, the weld length shall not be less than 60 mm. For roof systems without purlin systems, reinforced concrete roof panels must be securely three-point welded to the space frame, with a minimum bearing length of 80 mm. This prevents roof materials from collapsing and damaging the space frame during earthquakes.

4. The drainage slope of space frame roofs should preferably be achieved through variable height or overall arching of the entire frame. Numerous methods exist for creating drainage slopes in space frame roofs. Previously, domestic practices often involved adding small columns at upper chord nodes to form slopes, concentrating roof mass at column tops—a practice detrimental to seismic performance. Therefore, it is specified that variable height or overall arching of the space frame should be adopted instead. This approach brings roof mass closer to the upper chord nodes, enhancing seismic resistance.

评论

发表评论

此博客中的热门博文

ROOFING CONSTRUCTION TECHNOLOGY OF SADDLE-SHAPED OVERHANGING STEEL STRUCTURE RETICULATED SHELL SKIRT BUILDING OF HANGZHOU GATE SUPER HIGH-RISE BUILDING

图片
  Hangzhou Century Center, which is the tallest building under construction in Hangzhou and the tallest twin tower building in the Hangzhou Bay area, is known as the gate of Hangzhou. The wings of the two towers of Hangzhou Gate, together with the surrounding Olympic Sports Center, natatorium, International Expo Center, as well as the civic center, international Convention center, and grand Theater on the other side of the Qian River, form a "seven-star bright" urban picture. The Gate of Hangzhou is like a cloud floating in the seven stars, with a strong sense of design and visual impact.   The main body of Hangzhou Gate is composed of symmetrical 63-story east and west towers, with a building height of 302.6m and a total construction area of about 532,500 square meters. The east and west towers are connected by steel arch Bridges on the 1st to 6th floors above ground. The maximum span of the bridge is 85m at the north and south ends, the minimum span is 55m in the middle...
阅读全文

Current status of steel structure industry

图片
At present, with the rapid economic development and the acceleration of urbanization, new building materials and construction technologies are gradually becoming the mainstream of the construction industry. Among them, as a new, environmentally friendly, energy-saving and efficient construction method, steel structure buildings have received more and more attention. According to the "Steel Structure Market Development Trend Forecast" report published by Academia Sinica, it is expected that the steel structure construction market will continue to maintain a good development trend in the next few years. The report pointed out that since the construction industry is a large energy consumer, green and low-carbon development has become an important trend in this industry. Steel structures and prefabricated buildings are increasingly recognized and popularized in the industry due to their advantages of being more environmentally friendly, energy-saving, and efficient. LF is profess...
阅读全文

What is the difference between a girder, rafter, and purlin in steel structures?

图片
  In steel structures , girders, rafters, and purlins are all structural components that play different roles in supporting the building's load and providing stability. Here's a breakdown of each: 1. Girder:     - A girder is a large horizontal beam that supports other beams or loads across an open space, such as a roof or floor.     - Girders are typically placed perpendicular to the beams they support and are designed to carry heavy loads over long spans.     - In steel construction, girders are often used in building frames and bridges to distribute loads from the beams to the columns or supports. 2. Rafter:     - A rafter is a sloped structural member that supports the roof covering and transfers its load to the walls or other supporting elements.     - Rafters are commonly used in roof framing to provide structural support and to create the pitched shape of the roof.     - In steel constr...
阅读全文