Wood structure and steel structure are the building structure forms that the country vigorously develops and promotes at present. When choosing building materials, do you prefer steel or wood? Which of these two structures has better fire resistance?

Wood structure is one of the earliest architectural structures in the history of human civilization. More than three thousand years ago, China, Egypt and Greece respectively appeared the earliest wooden frame system. This kind of structure is widely used for its excellent performance and aesthetic value.

For light wood parts that need to reach a certain fire resistance limit as required by the code, the fire prevention method is mainly to non-combustible or non-combustible treatment of combustible wood parts covering materials to block the direct contact between the flame and the wood parts. One of the traditional ways to do this is to add thermal insulation between the wooden keels and cover them with drywall. In practical projects, different levels of insulation materials and gypsum board can be selected to make light wood parts reach different fire resistance limit time. The test proves that the fire resistance limit time of light wood wall and wood floor can reach 0.75h~2h.

According to the current "Wood structure design Standard" GB50005-2017 national standard, large cross-section components are often used to achieve the corresponding fire resistance limit. The size of the section should be in accordance with the combustion performance and fire resistance requirements of the component, so as to ensure that the section of the wood structure during fire can still meet the bearing capacity design requirements after deducting the effective carbonization layer thickness calculated by burning at a nominal linear carbonization rate of 38mm/h.

There should be systematic and perfect measures for fire prevention of modern wood structure buildings. In addition to requiring wood structural members to meet the corresponding fire resistance requirements, the following factors should also be considered:

Automatic sprinkler system, fire alarm system, building fire extinguisher, hydrant fire extinguishing system and other reasonable and complete active fire fighting measures are configured for wood structure buildings with different functions.

Meet the requirements of fire spacing between wood structures and between wood structures and other buildings;

The setting conditions and requirements of safety evacuation facilities for building personnel in case of fire;

The concealed space of the building must be separated by fire;

Adequate fire protection measures should be considered for pipelines and electrical lines.

Steel structure is mainly made of steel structure, is one of the main building structures. Steel is characterized by high strength, light weight and high stiffness, so it is particularly suitable for building large-span, ultra-high and super-heavy buildings.

Although the steel itself is non-combustible, the material properties of the steel are greatly affected by temperature. At 250℃, the impact toughness of steel decreases. When the temperature exceeds 300℃, the yield point and ultimate strength decrease significantly. In the actual fire, the critical temperature of steel structure losing static equilibrium stability is about 500℃ under the condition of constant load. The general fire temperature will reach 800℃ ~ 1000℃; In addition, the steel structure conducts heat quickly, and it is easy to rise the temperature of the full section at high temperatures, and plastic deformation quickly occurs, resulting in local damage, and eventually the overall collapse failure.

According to the different fire prevention principles in steel structure, the fire prevention measures can be divided into thermal and water cooling methods. By spraying fire-resistant materials or external refractory materials on the outside of the steel, the steel can form or have a thermal insulation protective layer to improve the fire resistance of the steel. Large specific heat capacity of water can absorb a lot of heat; When the fire occurs, water film can be formed on the surface of the steel structure by arranging the spray system on the upper part of the steel structure; The water film absorbs heat and evaporates to delay the steel reaching the critical temperature at which the stability of static equilibrium is lost. In addition, water containing rust inhibitor and antifreeze can be filled into the hollow steel structure to absorb heat through the circulation of water in the steel structure to keep the steel at a low temperature in the fire to avoid high temperature failure.