Shear strength of reinforced and prestressed concrete beams with lightweight aggregate concrete
Abstract
Normal-strength lightweight aggregate concrete (NSLWC) has been used in place of normal-strength normal-weight concrete (NSNWC) in building applications to decrease dead load and reduce member dimensions. Recently, bridge engineers and researchers have sought to implement the use of both NSLWC and high-strength lightweight aggregate concrete (HSLWC) for the same reasons. The shear strength of LWC beams is of particular concern. LWC has a lower tensile strength than normal-weight concrete (NWC) and hence a lower inclined concrete cracking load. Also, the behaviors of different lightweight aggregates vary significantly and must be individually evaluated. The objectives of this study were to study the effect of sand-lightweight aggregate concrete (SLWC) on the shear strength of reinforced and prestressed concrete beams and to evaluate design methods for the shear strength of SLWC beams. In order to achieve the objectives of the study, an experimental program comprising a reinforced concrete series and a prestressed concrete series was conducted. The effects of aggregate type, concrete compressive strength, and reinforcement details on the shear strength were studied in the reinforced concrete series. The variables in the prestressed concrete series included concrete compressive strength and amount of transverse reinforcement. After testing the beams, the measured shear capacity of each beam was compared with the shear capacity computed using the procedures outlined in the AASHTO LRFD and the ACI 318-95/AASHTO. Both the AASHTO LRFD General Method and the ACI 318-95/AASHTO Simplified Method provided conservative estimates of the shear strength for the twelve reinforced concrete specimens and for the four prestressed concrete specimens. Based on the results of the tests, the minimum amount of transverse reinforcement prescribed by the AASHTO LRFD and ACI 318-95 was not adequate for the high-strength prestressed concrete beams made with sand-lightweight aggregate concrete. Based on the test results and an evaluation of the design methods, it is recommended that designers use the ACI 318-95 method of beam design for shear.
Degree
Ph.D.
Advisors
Ramirez, Purdue University.
Subject Area
Civil engineering
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