Structural Fire Safety Design

• Explain how the expression of a post-flashover fire temperature can be derived from thermal equilibrium and which parameters the fire curve depends on.
• List different design fires based on this model and explain the main differences between nominal fire curves and parametric fires.
• Calculate the fire characteristics (fuel load, thermal inertia, and opening factor) of any given compartment and derive the corresponding parametric fire curve.
• Predict how the variation of the fire characteristics affects the severity and duration of the fire and, in turn, the heating temperature and fire resistance of the structural elements.
• Calculate the reduction of the mechanical design load in fire condition and explain how the mechanical loads influence the critical temperature and the fire resistance of fire-exposed structural elements.
• Calculate the reduction of the mechanical properties of steel, concrete, and wood at high temperatures. Calculate the permanent reduction of mechanical properties of cold-worked and presstressed steel and of concrete when they are cooled down to 20 C after being exposed to high temperatures.
• Perform the design or verification of uninsulated and insulated steel elements subjected to a parametric or standard fire.
• Perform the verification of timber elements exposed to parametric or standard fire
• Perform the verification of concrete elemetnts subjected to a parametric or standard fire during and after the fire.
• Identify possible weaknesses in the structural fire response of a building elements and indicate measures to improve its fire resistance.

The course content is divided in 4 main parts, one general on the structural background and fire action (0.) and three related to the application of the fire action to the structural design of: 1. steel, 2. timber, 3. concrete.

0. BACKGROUND ON FIRE AND STRUCTURE (1st module)
Structural background: force, moment, reactions and cross-sectional forces. External and internal equilibrium equations. Stress, strain, elasticity (Hook’s law). Moment of inertia and modulus of resistance of the element cross-section.
Fire background: Meaning of flashover assumption in structural fire safety. Ventilation- and fuel-controlled conditions. Fire characteristics (Fuel load, ventilation factor, and thermal inertia), DK parametric fire, standard fire. Fire rating and resistance classes. Safety coefficients for load and mechanical properties in fire condition.

1. STEEL ELEMENT DESIGN (1st and 2nd module)
Thermal properties of steel. Section factor. Lumped heat capacity method for the heating temperature of uninsulated steel.
Insulating materials for fire protection of steel elements. Heating temperature of insulated steel under the assumption of thin insulation.
Degradation of strength and stiffness of hot-rolled steel. Elastic and plastic design. Calculation of load bearing capacity of unprotected and fire-protected steel elements (verification) for beams and columns. Calculation of the min insulation thickness to sustain the imposed mechanical loads in fire (design) for beams and columns.
Thermal expansion of steel, eigen-stresses and reduction of the capacity of columns with hindered thermal expansion.

2. TIMBER ELEMENT DESIGN (2nd module)
Timber as combustible material. Firestorms and city fires.
Timber as construction material. Charring of wood: charring temp. and charring rates. Degradation of timber mechanical properties.
Cross-section reduction method and strength reduction method. Calculation of the load bearing capacity of timber beams and columns for parametric and standard fire (verification).

3. CONCRETE ELEMENT DESIGN (3rd module)
Thermal properties of concrete. Type of concrete failures and examples of collapse. Hot and cold condition.
Concrete temp. for mono- and bi-directional heating. Symmetry lines and equivalent fully exposed section for temp. calculation at any given time and depth of any concrete cross-section.
Degradation of mech. properties of concrete and reinforcing steel. Permanent damage and residual strength. Damage factors (zone method) and use of CONFIRE.
Calculation of load bearing capacity (verification) of concrete beams and slabs in bending. Transient strain and axially loaded columns with no or little eccentricity.

Ground knowledge of mathematics (analysis of functions, trigonometry, integral and derivatives) and physics (force, moment, gravity, reactions, first and second moment of area, center of gravity, equilibrium equations).
Basics of structural mechanics (external and internal forces, elasticity, stresses, strain).

Lectures at DTU and remote-learning with e-mail support from teachers and possible Teams meeting.
Exercises (not graded) to be solved individually and in groups (2-4 students) and handed-in ca. weekly in DTU Learn during the remote-learning periods.

Minimum: 10, Maximum: 35.

Please be aware that this course has a minimum requirement for the number of participants needed, in order for it to be held. If these requirements are not met, then the course will not be held. Furthermore, there is a limited number of seats available. If there are too many applicants, a pool will be created for the remainder of the qualified applicants, and they will be selected at random. You will be informed 8 days before the start of the course, whether you have been allocated a spot.