The system and method for connecting a square concrete-filled steel tubular column to a reinforced concrete footing includes a short steel pipe partially embedded in the footing, the pipe having a top end having flanges extending radially therefrom, the top end extending into a cavity in the footing having an elliptical top opening and circular base, the flanges extending above the base. An elliptical base plate is welded to the bottom of the tubular steel column, the base plate having a circular opening defined therein and a plurality of spaced flange slots depending therefrom. The bottom end of the column is lowered into the cavity, the elliptical base plate passing through the elliptical opening in the cavity, and the column is rotated 90° to interlock the flanges with the flange slots. The cavity is filled with concrete grout, and the square or rectangular steel column is filled with concrete.

A double-steel tube concrete beam-column joint with internal FRP bar connectors is provided. The double-steel tube concrete beam-column joint includes double-steel tube columns, I-beams, a joint connector, an internal support member and external ring plates. Each double-steel tube column includes an internal steel tube and an external steel tube. The joint connector includes an internal connecting tube and an external connecting sleeve which are both circular steel tubes. The internal support member is a columnar structure and has two ends regularly formed with bolt holes in a circumferential direction. Each external ring plate comprises a horizontal portion and an annular portion perpendicular to the horizontal portion. Upper and lower double-steel tube columns are connected through the joint connector and the internal support member, the two ends of the internal support member are inserted into an upper internal steel tube and a lower internal steel tube, respectively.

The invention provides a method for quantitative analysis of cavity zone of the top of the concrete-filled steel tube, comprising the following steps: By substitution of the determined inner radius of the steel tube, the thickness of the tube wall and the propagation speed of the ultrasonic wave in the steel tube, the propagation speed of the ultrasonic wave in the concrete, and the starting time of the first wave when the ultrasonic wave propagating between the top and the bottom of the concrete-filled steel tube into the calculation model of the cavity height of the top of the concrete-filled steel tube, to obtain the cavity height of the top of the concrete-filled steel tube; the calculation model of the cavity height is:

[00001]$t=\left(\frac{x_1+\sqrt{d^2+2x_2\left(d+r\right)}}{v_s}+\frac{\sqrt{4r^2+d^2+4\mathrm{rd}-2rh-2\mathrm{hd}}-\sqrt{d^2+2x_2\left(d+r\right)}}{v_c}\right);$

wherein, x.sub.1 and x.sub.2 are both calculation variables, and their values are:

[00002]$ x 1 = d 2 + 2 ⁢ h ⁢ d + 2 ⁢ r ⁢ h h + d .Math. arcsin ⁡ ( h + d d 2< Three-dimensional lightweight steel framing system formed by bi-directional continuous double beams 20210131104 · 2021-05-06 · Ying Chun Hsieh The present invention discloses a three-dimensional lightweight steel framing system formed by bi-directional continuous double beams. The three-dimensional lightweight steel framing system comprises beams, purlins, columns, wall bodies, floor slabs and lateral resistant mechanism comprises of diagonal support or bracing, wherein the beams are continuous double beams, and the continuous double beams are formed by combination of identical or different continuous single beams, and the continuous single beams are respectively arranged at the both sides of the columns, and the single beams are kept continuous at the junctions with the columns. The three-dimensional lightweight steel framing system simplifies the production of the lightweight steel member, and simplifies the on-site assembly by using bolts and nuts. System and method for connecting a square concrete-filled steel tubular column to a reinforced concrete footing 10954662 · 2021-03-23 · King Saud University · Husain Abbas, Nadeem A. Siddiqui, Baha M. A. Khateeb, Tarek H. Almusallam, Yousef A. Al-Salloum The system and method for connecting a square concrete-filled steel tubular column to a reinforced concrete footing includes a short steel pipe partially embedded in the footing, the pipe having a top end having flanges extending radially therefrom, the top end extending into a cavity in the footing having an elliptical top opening and circular base, the flanges extending above the base. An elliptical base plate is welded to the bottom of the tubular steel column, the base plate having a circular opening defined therein and a plurality of spaced flange slots depending therefrom. The bottom end of the column is lowered into the cavity, the elliptical base plate passing through the elliptical opening in the cavity, and the column is rotated 90 to interlock the flanges with the flange slots. The cavity is filled with concrete grout, and the square or rectangular steel column is filled with concrete. CONCRETE FILLABLE STEEL JOIST 20210017765 · 2021-01-21 · INVENT TO BUILD INC. · Michael R. STRICKLAND A concrete fillable steel joist includes a generally U-shaped member and a top chord. The generally U-shaped member has spaced apart webs and a bottom chord. The top chord is operably attached to the U-shaped member. The top chord has a plurality of spaced apart top chord holes. The U-shaped member and the top chord define a volume that is fillable with concrete when opposed ends of the U-shaped member have joist ends operably attached thereto. The joist ends may be a pair of end plates. Alternatively, the joist ends may be structural members. A concrete fillable steel joist system includes a plurality of spaced apart concrete fillable steel joists, and metal decking. The metal decking is operably attached between the spaced apart steel joists. The concrete fillable steel joist and the metal decking are configured to receive concrete. CALCULATION METHOD OF ULTIMATE MOMENT RESISTANCE AND MOMENT-ROTATION CURVE FOR STEEL BEAM TO CONCRETE-FILLED STEEL TUBE COLUMN CONNECTIONS WITH BIDIRECTIONAL BOLTS 20200408626 · 2020-12-31 · Yonghui AN, Guojie ZHOU, Jinping OU The invention discloses a calculation method of ultimate moment resistance and moment-rotation relation for steel beam to concrete-filled steel tube column connections with bidirectional bolts, wherein the calculation method as follows: calculate ultimate moment resistance values of the connection for different failure modes, i.e. yielding of the endplate or T-stub in bending, failure of bolts in tension, failure of column in transverse compression, failure of panel zone in shear, and yielding of the steel beam in bending; the smallest one in the five ultimate moment resistance values is taken as the ultimate moment resistance of the connection; obtain the initial rotational stiffness of the connection by the test, simulation or theoretical calculation; then, the moment-rotation curve of the connection is obtained by substituting the initial rotational stiffness and the ultimate moment resistance into the proposed exponential model for the moment-rotation relation. Assemblable structural column joint connection using fiber-reinforced concrete filled round double steel tubes and mounting method thereof 10851537 · 2020-12-01 · Zhang; Chunwei · Chunwei Zhang, Li Sun An assemblable structural column joint connection using fiber-reinforced concrete filled round double steel tubes, including an outer high-strength round steel tube, an inner high-strength round steel tube and a round separation plate. The wedge-shaped teeth are provided at two sides of the outer and inner high-strength steel tubes, and wedge-shaped teeth spaced are uniformly distributed along circumferences of the inner and outer high-strength round steel tubes. The round separation plate includes a round plate provided with a central through-hole, and vertical separation walls are provided with on upper and lower surfaces of the round plate. The vertical separation walls are provided with wedge-shaped sliding grooves matching the wedge-shaped teeth. The inner and outer high-strength round steel tubes are fixedly connected to the round separation plate by matching the wedge-shaped teeth with the wedge-shaped sliding grooves. Structural element 10829934 · 2020-11-10 · Andries Auret Louw Disclosed is a structural element including of interlocked resilient sheet material components, with each sheet operatively forming a component by being shaped to provide an elongate base with two opposing edges from which a first extension and a second extension respectively extend, with the second extension extending further from the base than the first extension, with the first and second extensions being provided with complimentary interlocking means operatively enabling the extensions of one sheet material component to be interlocked with the extensions of another sheet material component; with the extensions of four sheet components being interlocked, each at a right angle with at least one extension of another one of the sheet components, operatively for four sheet components to provide the structural element with an elongate open-ended core with a plurality of elongate open-ended ribs spaced around the core with each rib being longitudinally aligned with the core. Lattice tower 10760293 · 2020-09-01 · SECCIONAL BRASIL S/A · Paulo Emmanuel de Abreu, Odilon Antonio Camargo do Amarante This invention relates to lattice tower for actuate under high load conditions, more particularly to lattice towers utilized for wind turbines and other applications comprising three metallic legs arranged in a triangular configuration around a vertical axis of the lattice tower, wherein each metallic leg has a closed cross-section profile, a distance between the center of metallic legs in a bottom portion of the tower is greater than 4 meters, an angle of inclination of a central longitudinal axis of each metallic leg in relation to the vertical axis of the tower is between 1.7 degree and +1.7 degrees, and the height of the lattice tower is greater than 60 meters, a plurality of bracing members and auxiliary bracing members and a support platform disposed at a top portion of the tower. $