Behavior of new types of flange connectors of precast double‐tees

Abstract

Double-tees are often used as roof and floor systems in commercial buildings and parking garages, and they are often joined with mechanical connectors to form a floor system. The properties of flange-type connectors directly affects the in-plane behavior of double-tee diaphragms; however, most of them have been developed through field experience with undependable capacities, despite such connectors having been extensively applied in practice. Five new types of connectors were constructed, and a total of 15 connector tests were conducted under a variety of loading conditions with both monotonic and cyclic reversing in-plane shear. The load-deformation relationship, stiffness, energy consumption capacity, and shear capacity of the five new types of mechanical connectors were obtained. The results show that the seismic performance of new types of mechanical connectors deviated from each other by large margins, and they are satisfactory for vertical loading. The test results also show that the pre-toppings can effectively improve the strength and deformation capacity for all kinds of connectors.depth of double-tee flanges, experimental research, flange-type connectors, loading patterns, prestressed double-tees | INTRODUCTIONPrecast concrete double-tees are commonly used to form floor and roof diaphragms for parking garages, commercial and industrial buildings, as shown in Figure 1. [1] It is common practice to use discretely spaced mechanical flange-to-flange connectors to join adjacent double-tees. These flange connectors not only facilitate the equalizing of camber between adjacent precast units but also provide a transfer of gravity loads and lateral forces between units. [2][3][4][5] In some existing building codes, double-tees can also be overlain with a reinforced, cast-in-place topping slab to form a composite floor system, rather than using mechanical connectors. However, the damage incurred by buildings with topped double-tee diaphragms (but without mechanical connectors) during the 1994 Northridge earthquake cast doubts on the ability of these systems to perform adequately during a strong earthquake. [6][7][8][9] Subsequent analytical studies have also shown the potential weakness of the topped diaphragm system and have further emphasized the importance of the mechanical connectors between precast double-tees. [10][11][12] Mechanical connectors generally require less labor and are faster to install; therefore, they would be preferable to topping slabs in seismic regions if they could provide similar or better strength and ductility. [13][14][15][16] While the flange connectors of double-tee members have been extensively used for many years in precast, prestressed concrete construction, shear behavior of the connectors has not been extensively investigated, especially for pretopped connectors subjected to the combination of both in-plane shear and out-of-plane shear. [17][18][19][20][21][22][23][24][25][26] Cao, Naito, and Ren carried out a series of research on pretopped and topped systems with seven types ...

Predicting capacity models and seismic fragility estimation for precast parking structures based on machine learning techniques

“…The floor‐to‐floor connectors were thought of as having the following initial shear stiffness values k s‐f‐f (kN/m): almost no connectors ( k s‐f‐f = 10), bolt connectors 39 ( k s‐f‐f = 3500), plate bar connectors (PB‐130) 40 ( k s‐f‐f = 10,000), H‐plate bar connectors 41 ( k s‐f‐f = 35,000), bent wing connectors 42 ( k s‐f‐f = 10 5 ), novel bearing‐shear connectors 43 ( k s‐f‐f = 10 6 ) and rigid connectors ( k s‐f‐f = 10 10 ).…”

“…For the floor‐to‐wall/beam connectors, the initial shear/tensile stiffness values k f‐w (kN/m) shown below were taken into account: REF connectors 46 ( k f‐w = 2500), BS connectors 41 ( k f‐w = 9000), Plate‐Bar connectors 40 ( k f‐w = 65,000), Y‐type connectors 47 ( k f‐w = 10 6 ) and rigid connectors ( k f‐w = 10 10 ).…”

Diaphragm effectiveness of multistory precast parking structures with floor‐to‐floor mechanical connectors

“…The following values of elastic shear stiffness are considered for floor‐to‐floor connectors k s‐f‐f (kN/m): k s‐f‐f = 10, almost no connectors; k s‐f‐f = 3500, order of magnitude for elastic stiffness of Bolt connectors 25 ; k s‐f‐f = 10,000, order of magnitude for elastic stiffness of Plate Bar connectors (PB‐130) 26 ; k s‐f‐f = 35,000, order of magnitude for elastic stiffness of H‐Plate Bar connectors 25 ; k s‐f‐f = 10 5 , order of magnitude for elastic stiffness of Bent Wing connectors 27 ; k s‐f‐f = 10 6 , order of magnitude for elastic stiffness of Novel Bearing‐Shear connectors 28 ; k s‐f‐f = 10 10 , order of magnitude for rigid connectors, such as welded connectors. …”