Advanced interface for ExposureConditions HT

This section details the input parameters associated with the humidity and temperature boundary conditions (Figures 24 and 25). Boundary conditions must be defined for the different sequences of time. The equations for boundary conditions (temperature and humidity) are based on the same type of sine function as for the ionic species. The previously defined sequences for the ionic species are used for the temperature and humidity boundary conditions.

Figure 24. Boundary Conditions window for temperature

Figure 25. Boundary Conditions window for humidity

The main difference from the ionic species is that the user must select either Dirichlet or Cauchy boundary conditions. The Dirichlet type, which is the default type for the ionic species, consists of directly imposing a value at x=0 and/or x=L. The Cauchy boundary condition consists of an exchange term at the surface of the material expressed as:

Where qs is the flux at the surface, h is the exchange coefficient term, and is the average value of the variable u (temperature or humidity) in the environment. The difference from the Dirichlet condition is that the user must provide a value for the exchange coefficient. Typical values of h for temperature are 5.0 W/m2 for light wind conditions and 40.0 W/m2 for strong wind conditions. In the case of humidity, values range from 1x10-8 m/s for light wind conditions to 1x10-7 m/s for strong wind conditions. The parameter is expressed as:

which is similar to the expression for ionic species.

It is strongly advised to use Cauchy boundary conditions for humidity and temperature. From a physical standpoint, they correspond more closely to real life situations. As an added benefit, they tend to improve convergence of the numerical algorithm.

The following example illustrates how to enter the temperature and humidity condition parameters in the case of a parking slab exposed to deicing salts (Figure 24 and Figure 25). It is assumed that average annual temperature is 4°C with a 16°C amplitude applied at x=0. The temperature boundary condition applied at x=L assumes an average annual temperature of 4°C with a 16°C amplitude. The salt is applied between 245 and 305 days when the temperature reaches its lowest values. The relative humidity is constant at 60% on both sides of the slab, except during the winter (between 245 and 305 days) when the top surface is covered with a salt solution (100% RH) and the bottom surface is at 60% RH.

In order to maintain continuous temperature over the three temperature sequences, check “on” the button “Same Sequences”. Identical parameters are automatically entered at both x=0 and x=L for all sequences. Otherwise, check “off”.

Exposure conditions (Temperature and humidity) information

Local exposure conditions can be found using the following link:

http://www.weatherbase.com

Weatherbase.com is suggested because it offers complete temperature information and relative humidity data.

Data are available for anywhere in the world. Simply select a region, country, state, and then select a city. Data are available in metric or U.S. units. The data to use with STADIUM® are the average temperature and relative humidity. The amplitudes are also available since data for each month of the year are given. The relative humidity can be determined by calculating the average of the morning and evening values. In order to show relative humidity data, select all data from the tab menu.