DETERMINATION OF THE BEARING CAPACITY OF REINFORCED CONCRETE COMPRESSION MEMBERS

TRAGLASTERMITTLUNG VON STAHLBETON-DRUCKGLIEDERN

THE OBJECTIVE OF THE WORK WAS THE DERIVATION OF PRINCIPLES FOR IMPROVING THE BUCKLING SAFETY SPECIFICATIONS IN REINFORCED CONCRETE CONSTRUCTION. THE PROGRAMME OF WORK IS DIVIDED INTO TWO PARTS: (1) CALCULATION OF THE BEARING CAPACITY OF REINFORCED CONCRETE COMPRESSION MEMBERS ON THE BASIS OF THE MOST REALISTIC MATERIAL COEFFICIENTS POSSIBLE. IN ORDER TO CALCULATE THE BEARING CAPACITIES OF REINFORCED CONCRETE SUPPORTS A COMPREHENSIVE COMPUTER PROGRAM WAS DEVELOPED FOR THE IBM 70 94 COMPUTER AT THE GERMAN COMPUTER CENTRE AT DARMSTADT. THIS PROGRAM ALLOWS THE BEARING CAPACITIES OF ANY REINFORCED CONCRETE SUPPORTS AND THEIR DEFLECTIONS AND TORSIONS TO BE CALCULATED. THE CHARACTERISTIC VALUES OF THE BENDING COMPRESSION ZONE WERE USED AS A DIRECT BASIS FOR THE STUDY OF REINFORCED CONCRETE SUPPORTS WITH A RECTANGULAR CROSS-SECTION, AND SIMILAR CHARACTERISTIC VALUES OF THE BENDING COMPRESSION ZONE HAD TO BE DERIVED FOR ANY OTHER CROSS-SECTION. MOREOVER A SPECIAL METHOD WAS DEVELOPED FOR CALCULATING CREEP DEFORMATIONS FOR ANY GIVEN BOUNDARY CONDITIONS. SURVEY OF THE THEORETICAL STUDIES CARRIED OUT: A) INFLUENCE OF CONCRETE IN THE TENSION ZONE BETWEEN THE CRACKS ON THE BENDING STIFFNESS OF REINFORCED CONCRETE CROSS-SECTIONS UNDER NORMAL STRESS; B) DRAWING UP OF 36 TABLES FOR BEARING CAPACITIES AND PERMISSIBLE LOADS ON RECTANGULAR REINFORCED CONCRETE SUPPORTS WITH THE RELEVANT DEFORMATIONS AND STRAINS ON THE COMPRESSED EDGE OF THE CROSS-SECTION; C) EXAMINATION OF THE CURRENTLY WELL-KNOWN TESTS ON REINFORCED CONCRETE SUPPORTS; D) PROPOSAL AND EXPLANATION OF AN APPROXIMATION METHOD FOR DESIGNING RECTANGULAR REINFORCED CONCRETE COMPRESSION MEMBERS; E) EXAMINATION OF THE INFLUENCE OF THE SHAPE OF THE CROSS-SECTION ON THE BEARING CAPACITY OF REINFORCED CONCRETE SUPPORTS, AND COMPARISON OF RECTANGULAR CROSS SECTIONS WITH CIRCULAR AND T-SHAPED CROSS-SECTIONS; F) INFLUENCE OF IMPERFECTIONS; INFLUENCE OF A CROSS-SECTIONAL SHAPE WHICH CONTINUALLY AND SUDDENLY ALTERS ALONG THE LENGTH OF THE CROSS-SECTION (THIS WORK IS BEING CONTINUED); G) AS A BASIS FOR CALCULATING THE SUPPORT DEFORMATIONS UNDER LONG-TERM LOADING, A SPECIAL METHOD OF DETERMINING THE INFLUENCE OF TIME ON THE STIFFNESS OF ANY GIVEN REINFORCED CONCRETE CROSS-SECTIONS WAS DERIVED. THE CALCULATION OF THE LONG-TERM SUPPORT DEFORMATIONS IS CURRENTLY BEING CONTINUED. (2) TESTS TO DETERMINE THE BEARING CAPACITIES OF REINFORCED CONCRETE SUPPORTS AND FRAMES UNDER SHORT-TERM AND LONG-TERM LOADING.