Behavior of Precast Beam-Column Connection under Progressive Collapse Scenario

Abstract

Progressive collapse has been termed to describe the partial or total collapse of the structure due to the propagation of an initial failure of a relatively small portion of the structure or failure of vertical load carrying element i.e. column or load bear- ing wall, resulting into a chain reaction. Failure of major portion will results in to substantial loss of human lives and natural resources. Therefore it is very important to prevent this type of disproportionate collapse which is also known as progressive collapse. Progressive collapse of a structure can be prevented by use of horizontal

oor and vertical column and wall ties, continuity, ductility and redundancy to redis- tribute additional forces through an alternate load path. Now days, there is increasing trend towards construction of buildings using precast concrete during recent past. Durability, corrosion resistance, fire resistance, resis- tance to noise, quality control, accelerated curing and speedy construction work are a few advantages of precast concrete construction over conventional cast-in situ con- crete construction. The main concept of precast concrete construction is that all the components of structures are produced in controlled environment and it is be- ing transported to the site. At site such individual components are just connected by some means. Due to these advantages of precast concrete construction over con- ventional cast-in situ construction, use of precast technique all over the world has escalated. In precast concrete construction, connections are considered as the most critical links of the structure. It is also evident that major collapse of precast building occurred due to connection failure. Therefore it is very important to study the per- formance of connection between beam and column under progressive collapse scenario. In this study, behavior of monolithic and six different types of precast beam-column assemblages on progressive collapse resistance is investigated for G+5 reinforced con- crete building through experiments. A symmetric RC building having 4 bays in longi- tudinal direction and 3 bays in transverse direction having 4 m center-to-center span is considered. Progressive collapse resistance for beams are evaluated for removal of middle column from ground oor located on long side of plan as suggested by General Services Administration (GSA) guidelines. First oor level beams on either side of removed column are considered for study. Total seven specimens i.e. 1 monolithic specimen and 6 precast specimens, are tested to study the effect of behavior of progressive collapse for different types of connec- tions. Specimens are designed by considering gravity and seismic loading with ductile detailing. Each specimen contains two beam spans and one central removed column. End column having height of 900 mm and mid column having height of 200 mm above and below the top and bottom surface of the beam. 1=3rd scale models are casted for experimental study. In experimental study, the two end columns are fixed while the central column is freely suspended to simulate exact condition as in prototype building under progres- sive collapse scenario. The end columns of specimen are restrained vertically as well as in lateral direction by applying compressive loading at their ends and using a tri- angular frame respectively. Load is applied on the central column using hydraulic jack. De ection along both the beam span and central de ection of middle removed column is measured. Load displacement relationship, crack pattern and strain at six different location of each beam are measured.