An alternative analysis utilizing deflection, strain and curvature data from simply supported single-span three- and four-point bending tests is presented for determining the flexural modulus of a beam. The analysis is extended to beams with bolted end connections to determine their rotational stiffnesses. Analyses of tests on symmetrically loaded pultruded GFRP wide flange (WF) beams with bolted end connections formed from GFRP equal leg angles are shown to produce consistent and repeatable connection stiffnesses. The semi-rigid beam analysis is recast to quantify the reduction in serviceability limit loads with increasing beam slenderness. Deflection and load performance indices for symmetric four-point loading are derived and evaluated using the connection stiffness data. For each type of end connection, the reductions in mid-span deflection and increases in load, relative to simply supported end conditions, are quantified for a range of load spacing ratios.