Showing papers on "Earthquake resistant structures published in 1969"

P-Δ and Axial Column Deformation in Aseismic Frames

Abstract: A study of the influence of P-Δ and axial deformation of columns on the response of unbraced multistory building frames subjected to strong earthquake motion is presented. The columns are assumed to behave elastically while the girders follow a nonlinear moment-curvature behavior defined by a Ramberg-Osgood function. The method of analysis is a step-by-step numerical procedure developed for use on a high-speed digital computer. The lateral response of the structure to a horizontal component of ground motion parallel to the plane of the frame is computed. Two 10- and 25-story frame models are analyzed for the El Centro, 1940, and the Taft, July, 1952, earthquakes. The results indicate that, for the type of structures considered, the P-Δ effect does not appear to have a significant influence on their inelastic response to strong earthquakes. But the axial deformation of columns may affect the response by as much as 10% to 20%.

Fatigue damage in seismic structures

Abstract: LOW-CYCLE FATIGUE DAMAGE FACTORS ARE COMPUTED FOR SINGLE- DEGREE-OF-FREEDOM SYSTEMS SUBJECTED TO ACCELEROGRAMS OF THE EL CENTRO EARTHQUAKE (NS COMPONENT) OF MAY 18, 1940, AND THE TAFT EARTHQUAKE (S69 DEGREE E COMPONENT) OF JULY 21, 1952. TWO INTERRELATED HYSTERESIS LOOPS, NAMELY, LOAD MAXIMUM STRAIN CURVE AND DEFLECTION-MAXIMUM STRAIN CURVE, ARE PROPOSED FOR COLUMNS WITH AN AVERAGE WIDE-FLANGE SECTION. THESE HYSTERESIS LOOPS ARE USED FOR FINDING THE TIME HISTORY OF MAXIMUM STRAINS IN THE SHEAR TYPE FRAME UNDER EARTHQUAKE LOADS. THE HISTORY OF PLASTIC STRAINS IS THEN USED TO COMPUTE THE CORRESPONDING CUMULATIVE DAMAGE FACTOR OF THE STRUCTURE. VARIABLES STUDIED INCLUDE FREQUENCY (IN THE ELASTIC RANGE) AND THE YIELD LOAD OF THE STRUCTURE. NUMERICAL RESULTS SHOW THAT (1) IT IS POSSIBLE FOR A STRUCTURE TO FAIL IN LOW-CYCLE FATIGUE UNDER SEISMIC LOADS, AND (2) THIS TYPE OF STRUCTURAL FAILURE CANNOT BE PREDICTED JUST BY STUDYING THE MAXIMUM STRUCTURAL DISPLACEMENTS OF THE STRUCTURE./ASCE/