Structural damages associated with buckling of longitudinal reinforcing steel and crushing of concrete induce strength and stiffness degradation in reinforced concrete (RC) beams and columns. This paper presents a numerical investigation on earthquake-induced damages and collapse of typical high-rise RC buildings model incorporating strength degradation (SD) effects. In a simple finite-element analysis program with the generalized stress fiber discretization, hysteretic constitutive models primarily dominate the inelastic behavior. Buckling of reinforcing steel and crushing of confined concrete are taken into accounted to the stress-strain relationship of fiber elements. The SD effect in components with small hoop ratio tends to amplify the seismic responses high-rise RC moment-resisting frames when the intensity of ground motions exceeds the design level. Buckling of steel rebar and crushing of concrete should be fully considered together with the P-Δ effect for collapse simulations. KEYWORDS component degradation, confinement effect, dynamic analysis, reinforced concrete, seismic collapse, tall buildings 1 | INTRODUCTIONIn the past decades, severe damages were largely observed in reinforced concrete (RC) moment frame structures during devastating earthquakes, such as the 1994 Northridge earthquake, [1] the 1995 Hyogoken-Nanbu earthquake, [2] the 2011 off the Pacific Coast of Tohoku earthquake, [3] and 2014 Ludian earthquake. [4] The ground motions generated in subduction zones or soft soil layers are characterized by long-period component, [5] which induces a resonance effect with high-rise RC moment frames vulnerable to seismic excitations. The primary challenge that should be solved is that the degrading constitutive model has to capture local failures in RC components. For the existing high-rise RC buildings under strong Nomenclature: C, effective length of hoops/stirrups (mm); D, depth of reinforced concrete section (mm); D c , width of hoop/stirrup reinforcement (mm); d c , depth of hoop/stirrup reinforcement (mm); E c , elastic modulus of concrete; E s , elastic modulus of steel; E s,∞ , modulus of steel corresponding to infinite strain; F c , nominal compressive strength of concrete cylinder; f ′ c , compressive strength of plain concrete (N/mm 2 ); f ′ cc , compressive strength of confined concrete (N/mm 2 ); n, axial force ratio (n = N/N y ); p w , sectional hoop/stirrup ratio of hoop/stirrup reinforcement; R, radian of the G-M-P backbone curve around the yielding point; R A , area of concentrated fiber element for reinforcing steel; S, longitudinal spacing of hoop/stirrup reinforcement (mm); V, ratio of elastic modulus to tangent modulus; W, confinement factor controlled by the effective radial stress; X, Y, normalized stress and strain with respect to maximum point of concrete; σ bu , critical buckling stress of steel rebar in uniaxial compression; σ hs , yield strength of hoop/stirrup reinforcement (N/mm 2 ); σ r , ε r , residual compressive stress and strain of reinforcing steel; σ re , effective r...