I assume you use data binding to fill the RadChart with data. By default, there is a single ChartSeries in the Series collection, whose name you set. When data binding occurs, all ChartSeries are cleared and new ones are added. To successfuly change the series name, please, move the code
myChart.Series(0).Name = "Construction Time"
right after the Data Binding.
In case that solution does not solve your problem, please, provide more information about the way you fill data in the RadChart.
the Telerik team