A reinforced recycled block/aggregate concrete precast column and a construction method are provided. The reinforced recycled block/aggregate concrete precast column includes several first one-bar hoops, vertical reinforcement bars, several second one-bar hoops, a flexible hinge area, and recycled block/aggregate concrete; the first one-bar hoops and second one-bar hoops are each provided with an anchor end; the first one-bar hoops and second one-bar hoops are disposed in the flexible hinge area, and only the second one-bar hoops are disposed outside the flexible hinge area; the outer edge of each first one-bar hoop is flush with the outer surface of the reinforced recycled block/aggregate concrete precast column; and the interior of the reinforced recycled block/aggregate concrete precast column is filled with the recycled block/aggregate concrete, thereby greatly increasing the recycling rate of engineering waste, reducing shedding of a concrete protective layer in the flexible hinge area of the column.

A concrete construction (100) made by 3D concrete printing that contains: two or more layers (102, 106) of cementitious material extruded one above the other, and at least one elongated steel element (104) reinforcing at least one of the layers (102, 106). The elongated steel element (104) has an elastic and plastic elongation at break that exceeds 4%. The high elongation of the elongated steel element gives an increased ductility to the concrete structure (100).

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.

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.

The present disclosure discloses a Fiber Reinforced Polymer/Plastic (FRP) composite spiral stirrup confined concrete column and a compression design method. The FRP composite spiral stirrup includes an internal FRP spiral stirrup and an external FRP square stirrup. In the form of the FRP composite spiral stirrup, effective transverse stress transfer is established by effectively binding stirrups, which can give full play to the mechanical properties of the FRP bars, provide “dual confinement” for core concrete, and greatly improve the peak stress of the core concrete. Confining mechanisms of the FRP composite spiral stirrup to the concrete in different areas are analyzed, a confinement model and a bearing capacity calculation method for the FRP composite spiral stirrup confined concrete column are proposed, and a design method for the FRP composite spiral stirrup confined concrete column is proposed after an accurate calculation method for the bearing capacity is obtained.

The present disclosure discloses a Fiber Reinforced Polymer/Plastic (FRP) composite spiral stirrup confined concrete column and a compression design method. The FRP composite spiral stirrup includes an internal FRP spiral stirrup and an external FRP square stirrup. In the form of the FRP composite spiral stirrup, effective transverse stress transfer is established by effectively binding stirrups, which can give full play to the mechanical properties of the FRP bars, provide “dual confinement” for core concrete, and greatly improve the peak stress of the core concrete. Confining mechanisms of the FRP composite spiral stirrup to the concrete in different areas are analyzed, a confinement model and a bearing capacity calculation method for the FRP composite spiral stirrup confined concrete column are proposed, and a design method for the FRP composite spiral stirrup confined concrete column is proposed after an accurate calculation method for the bearing capacity is obtained.

A column reinforced with two reinforcement sleeves provides a low-cost, simpler method to form strong concrete columns for constructing buildings and other structures. The column includes a multi-axially braided reinforcement outer sleeve and an inner sleeve, which together provide sufficient structural support so that rebar can be eliminated from the column. Elimination of rebar saves cost and prevents the possibility of rebar oxidation which might otherwise undermine the structural integrity of the column and lead to catastrophic structural failure. The reinforcement sleeve is lightweight, easy to transport, and can be greatly reduced in size to facilitate transportation. The reinforcement sleeve and construction method can be utilized in many implementations and can be particularly useful for constructing buildings or other structures in geographic areas that are subject to earthquakes and/or corrosion, and where low cost is important.

A column reinforced with two reinforcement sleeves provides a low-cost, simpler method to form strong concrete columns for constructing buildings and other structures. The column includes a multi-axially braided reinforcement outer sleeve and an inner sleeve, which together provide sufficient structural support so that rebar can be eliminated from the column. Elimination of rebar saves cost and prevents the possibility of rebar oxidation which might otherwise undermine the structural integrity of the column and lead to catastrophic structural failure. The reinforcement sleeve is lightweight, easy to transport, and can be greatly reduced in size to facilitate transportation. The reinforcement sleeve and construction method can be utilized in many implementations and can be particularly useful for constructing buildings or other structures in geographic areas that are subject to earthquakes and/or corrosion, and where low cost is important.

A retrofitting method for a beam with an opening is disclosed. The retrofitting method provides a hoop cooperated with an inclined stirrup to form a reinforcement set. The hoop is used to enclose the opening; and the reinforcement set may be selectively adjusted according to the distance between the edge of opening and a column face. The retrofitting method and reinforcement set are not only suitable for openings located in the non-plastic hinge zone of the beam, but also suitable for the openings located in the plastic hinge zone.

A retrofitting method for a beam with an opening is disclosed. The retrofitting method provides a hoop cooperated with an inclined stirrup to form a reinforcement set. The hoop is used to enclose the opening; and the reinforcement set may be selectively adjusted according to the distance between the edge of opening and a column face. The retrofitting method and reinforcement set are not only suitable for openings located in the non-plastic hinge zone of the beam, but also suitable for the openings located in the plastic hinge zone.