Multi-energy CT (MECT) enabled by energy-resolved photon-counting-detector CT (PCD-CT) is promising for materialspecific imaging with multiple contrast agents. However, non-idealities of the PCD such as pulse pileup, K-edge escape, and charge sharing may degrade the spectral performance. To perform MECT, an alternative approach was proposed by extending a "Twin Beam" design to a dual-source CT scanner with energy-integrating-detector (EID) by operating one or both sources in the "Twin Beam" mode to acquire three (triple-beam configuration) or four (quadruple-beam configuration) distinct X-ray beam measurements. Previous computer simulation studies demonstrated that the image quality and dose efficiency of the triple-beam configuration were comparable to that in PCD-CT for a three-material decomposition task involving iodine, bismuth, and water. The purpose of this work is to experimentally validate the proposed triple-beam MECT technique in comparison with PCD-CT. To mimic the dual-source triple-beam acquisition, two separate scans, one at 80 kV and the other at 120 kV operated in the "Twin Beam" mode, were performed on a single-source CT scanner. Two potential clinical applications of MECT for multiple contrast agents were investigated: iodine/gadolinium for biphasic liver imaging and iodine/bismuth for small bowel imaging. The results indicate that the imaging performance of the EID-based MECT may be comparable to that on the current PCD-CT platform for both the iodine/gadolinium and the iodine/bismuth material decomposition tasks.