# Solar Radiation Parameters for Assessing Temperature Distributions on Bridge Cross-Sections
## 7 Discussion  
The following discussions can be drawn based on the results and within the limitations of the research presented in this paper:  
1. The variation trends for all hourly solar radiation curves are similar, with the solar radiation appearing at about 6:00 a.m., reaching the maxima at about 12:00 p.m. and disappearing at about 6:00 p.m. The maximum measured global solar radiation for Ninghua (about 1100 W/m\({}^{2}\)) was the highest and the difference between maximum global solar radiation for different cities was about 100 W/m\({}^{2}\). The maximum measured diffuse solar radiation for Fu'an (about 250 W/m\({}^{2}\)) and the calculated beam solar radiation for Ninghua (about 900 W/m\({}^{2}\)) was the highest. The difference between the maximum diffuse or beam solar radiation for different cities were both about 150 W/m\({}^{2}\). 2. The linear regression of Angstrom-Page equation using the monthly time scale of data sample can predict the global solar radiation for different cities in Fujian. For the cities in Fujian that did not have actual data on sunshine duration, the empirical coefficients can be estimated using the available sunshine duration for the nearest city. 3. The Collares-Pereira and Rabl equation can estimate the hourly global solar radiation for different cities in Fujian based on the daily global solar radiation. The hourly beam solar radiation for different cities in Fujian can be predicted well using the Hottel equation. The hourly diffuse solar radiation for different cities in Fujian can be calculated by subtracting the hourly beam solar radiation from the corresponding hourly global solar radiation. 4. The maximum global solar radiation, beam solar radiation and diffuse solar radiation (for 21 June, the summer solstice) for 56 cities in Fujian were calculated. The maximum global solar radiation for Xiapu (about 1210 W/m\({}^{2}\)) is the highest and the maximum global solar radiation for Anxi (about 970 W/m\({}^{2}\)) is the lowest. The biggest difference among the global solar radiation maxima in different cities is about 240 W/m\({}^{2}\). The maximum beam solar radiation for Zhouning (about 909 W/m\({}^{2}\)) is the highest and the maximum beam solar radiation for Ningde (about 821 W/m\({}^{2}\)) is the lowest. The biggest difference among the beam solar radiation maxima in different cities is about 88 W/m\({}^{2}\). The maximum diffuse solar radiation for Xiapu (about 388 W/m\({}^{2}\)) is the highest and the maximum diffuse solar radiation for Dehua (about 102 W/m\({}^{2}\)) is the lowest. The biggest difference among the diffuse solar radiation maxima in different cities is about 286 W/m\({}^{2}\). 5. Comparisons of the measured and calculated temperature-time responses for the concrete box girder, side-by-side box girder and T-shaped girder with or without the consideration of solar radiation indicates that the influence of solar radiation should be considered in the analyses of the temperature distribution on the bridge girder cross-sections in summer. The accuracy of the solar radiation calculated using the estimation models can meet the engineering requirements. The highest calculated temperatures without the consideration of solar radiation were lower and had a time delay, especially for top flanges in the summertime. The vertical temperature variation when considering the effect of solar radiation was significantly larger than that without the consideration of solar radiation. The influence of solar radiation on the temperature distribution decreases as the distance from external surfaces. The influence of solar radiation on the temperature distribution of the bridge girder cross-sections is negligible in winter. 6. The solar radiation parameters for other cities and regions in China and elsewhere, as well as different bridge superstructure types, can be similarly developed based on more case studies to establish the relevant estimation models. This can serve as a prelude for future development of specifications related to temperature effects in bridge engineering.