End Zone Reinforcement for Pretensioned Concrete Girders
In this study, a literature review was conducted to establish the background of current specifications and to evaluate the applicability of various theories and methods for design of end zone reinforcement. Analytical methods reviewed in this paper include finite element analysis, strut- and-tie modeling, and the Gergely-Sozen equivalent beam method. Previous experimental work combined with work conducted as part of this study were used to correlate between various theoretical and experimental results. This paper illustrates that no single theoretical method adequately represents the complex behavior at the end of a pretensioned concrete member. A general semi-empirical design procedure is proposed here. It is based on theoretical behavior and experimental observation. Standard reinforcement details are given. The proposed procedure could result in reduction in the congestion of reinforcement while maintaining acceptable crack control at the member end. Application of the proposed procedure to highly pretensioned bridge girders is demonstrated.
DESIGN OF ANCHORAGE-ZONE REINFORCEMENT IN PRESTRESSED CONCRETE BEAMS
THE REPORT PRESENTS A SIMPLE METHOD FOR THE DESIGN OF TRANSVERSE REINFORCEMENT NEAR THE END ZONES OF PRESTRESSED CONCRETE BEAMS TO RESTRAIN ANCHORAGE ZONE CRACKS. THE METHOD IS CONFIRMED BY TEST RESULTS. THE DESIGN METHOD IS BASED ON THE ASSUMPTION THAT LONGITUDINAL CRACKS WILL FORM IN THE END ZONE. THE ANALYSIS OF THE EQUILIBRIUM OF THE CRACKED END ZONE YIELDED EXPRESSIONS FOR THE LOCATION OF THE CRACK AND THE MAGNITUDE OF THE UNBALANCED MOMENT WHICH CREATES THE TENSION FORCES IN THE TRANSVERSE STEEL. A SIMPLE PROCEDURE RESULTED FOR THE DESIGN OF STIRRUPS TO RESTRAIN THE CRACKS. ONE SERIES OF TESTS CONFIRMED THE PROPOSED METHOD AND PREDICTED THE LOCATION OF THE CRACK AND THE FORCES IN THE REINFORCEMENT. A SECOND SERIES OF TESTS RESULTED IN A FORCE-SLIP RELATIONSHIP THAT WAS USED TO DEVELOP AN EXPRESSION TO LIMIT THE WIDTH OF THE CRACK. THE INVESTIGATION BROUGHT OUT THE IMPORTANCE OF THE SPALLING STRESSES, TRANSVERSE TENSILE STRESSES AWAY FROM THE LINE OF THE LOAD, AND SHOWED THAT FOR ECCENTRIC PRESTRESSING FORCES THESE STRESSES ARE LARGER FOR RECTANGULAR THAN FOR I-SHAPED END BLOCKS. /BPR/
Design of a Ceiling Glass Installation Robot
Building materials and components are much larger and heavier than many industrial materials. Ceiling glass is a type of building material for interior finishing. The demand for larger ceiling glass has increased along with the number of high-rise buildings and an increased interest in interior design. The objective of the study is to introduce robotic technology for installing ceiling glass on construction site. Robotically installed ceiling glass is receiving special attention because of the difficulties in moving to high installation positions and handling fragile building materials. Below, we describe the design of a ceiling glass installation robot. After analyzing a target project, we establish a design concept for a proposed robot. Finally, we describe the detailed design of the robot.