TWO-STEP-STATE REINFORCEMENT ESTIMATION TECHNIQUE OF THE ELEMENTS OF RC FRAME BUILDINGS AND STRUCTURES UNDER SEISMIC LOADS USING PUSHOVER ANALYSIS CONCEPT. PART 1: RESEARCH OBJECTIVE, TECHNIQUE FRAMEWORK, RESEARCH INFORMATION BASE AND STRATEGY OF DETERMINING OF HINGE ZONES FEATURES

Abstract

Review of techniques considering the definitions of a Pushover curve concept of nonlinear
system under seismic loads is accomplished. A pattern of an applied two-step-state reinforcement
estimation technique of the elements of RC frame buildings and structures containing a theoretical
basis of the nonlinear static (Pushover) analysis concept is presented by the author. It is suggested to
determine longitudinal reinforcement according to daily loads and weak (frequent) earthquakes using
the Response Spectrum Method in Seismic Building Design Code SNiP II-7–81* (rev. 2000)
formulation (with Seismic-Force-Reduction Factor K1 equal to unity). And under strong (rare) seismic
loads the author offers to estimate the adequacy of the accepted hinge zones computational parameters
and sufficiency of their web reinforcement congestion. Meanwhile, any most suitable nonlinear
static procedure can be used. On a particular example, the need for a clear justification of consistency
of hinge zones design characteristics and their design parameters adopted at a conceptual
design stage is explained. It is explained that length of an RC member end intended for arranging
strengthened web reinforcement and a plasticity length of hinge zone may in fact have different values
for the same element. And that an evaluating method of the web reinforcement near frame rigid
(moment) joint of the research objects using only a shear force criterion is applicable solely for short
RC elements. The contribution of the Soviet scientific school (1936–1975) to development of estimation
concept of earthquake-resistance structures using a Pushover curve is noted by the author.