A Boeing 737-4Y0, EI-CEU, was substantially damaged during landing at Denver, Colorado. There were no injuries to the 141 passengers, 4 cabin attendants, and two cockpit crewmembers aboard. Visual meteorological conditions prevailed. The airplane was being operated by MarkAir as flight 523, scheduled domestic passenger service from Kansas City, Missouri, to Denver, Colorado. According to the crew, the flight proceeded uneventfully and the approach briefing, radios, instruments, and speed bugs (Vref, 136 KIAS; target speed, 145 KIAS; Vref+15, 151 KIAS, based on a landing weight of 112,000 pounds) were set up for a planned landing on runway 17R. The first officer was flying the airplane. After the airplane had been positioned on the downwind leg, the crew was offered the option of landing on runway 16. This was accepted but when told they could expect a delay to that runway, they requested and were cleared for a visual approach to, and landing on, runway 17R. ATIS (automatic terminal information service) indicated the winds to be from 190 degrees at 18 knots. A surface weather observation in effect at the time indicated the winds were from 180 degrees at 19 knots. The first officer, who was flying the airplane, lined up with runway 17L and when the mistake was realized, they requested and were cleared to land on runway 17L. At 500 feet above ground level, the glide slope aural warning sounded and was cancelled because the radios had been tuned to the navaids serving the parallel runway. At 100 feet AGL, the GPWS (ground proximity warning system) sink rate warning sounded, and the first officer added power. At 50 feet AGL and over the runway threshold, airspeed deteriorated. The first officer applied additional power and the captain added maximum thrust and forward control yoke pressure. A hard landing was made. During its preflight inspection, the relief flight crew noticed damage to the airplane that included a compromised pressure vessel, a crushed tail skid, breaches in the skin with associated stringer damage, and a collapsed right main landing gear strut. The crew flying did not suspect any external damage to the aircraft until arriving at the gate and being told by ground personnel. The data from the airplane’s digital flight data recorder (DFDR) showed a vertical acceleration spiking at 3.64 g’s when the airplane contacted the runway. PROBABLE CAUSE: “Proper descent rate not maintained by the first officer, resulting in a hard landing. Factors were unfavorable wind conditions and the captain’s inadequate supervision of the first officer. “