195 2000 Nehrp Recommended Provisions 1951 Overview

The 2000 NEHRP Recommended Provisions for Seismic Regulation for Buildings and Other Structures (NEHRP Provisions) represents the current state of the art in prescriptive, as opposed to performance-based, provisions for seismic-resistant design. Its provisions form the basis for earthquake design specifications contained in the 2001 edition of ASCE-7, Minimum Design Loads for Buildings and other Structures, either through reference or direct incorporation, the seismic regulations in the 2003 edition of the International Building Code, and also the 2002 edition of the NFPA 5000 Building Code (NFPA, n.d.). As such, it will form the basis for most earthquake-resistant design in the United States, as well as other nations that base their codes on U.S. practices, throughout much of the first decade of the twenty-first century.

TABLE 19.1 NEHRP 2000 Plan Structural Irregularities

1: Torsional irregularity — when diaphragms are not flexible

Torisonal irregularity exists (1a) when the maximum story drift, computed including accidental torsion, at one end of the structure transverse to an axis is more than 1.2 times the average of the story drift at the two ends of the structure. (1b) Extreme torisonal irregularity exists when ratio >1.4

I S2 > 1.2(V S2)12 Extreme: S2 > 1.4(Sj + S2)/2

I S2 > 1.2(V S2)12 Extreme: S2 > 1.4(Sj + S2)/2

2: Re-entrant corners

Plan configurations of a structure and its lateral-force-resisting system contain re-entrant corners where both projections of the structure beyond a re-entrant corner are greater than 15% of the plan dimension of the structure in the given direction

0 0

Post a comment