Hai Long Zhao

Research on Compressive Stress - Strain Relationship of Fiber Reinforced Concrete

The marked brittleness of concrete could be overcome by the addition of fibers. This paper experimentally investigated the mechanical properties and constitutive relationship of different fiber reinforced concrete. It is shown from the results that the compressive strength and peak strain of concrete with fiber have little improvement, but the ultimate strain, deformation capacity, toughness and energy dissipation capacity are improved greatly. The damage constitutive model recommended by the emendatory code for design of concrete structure (appendix C) (GB50010-2002) is applied for calculations and analyses according to the test results. The damage constitutive model and non-elastic constitutive model of different fiber reinforced concrete are established based on the test results. It is indicated from the analyses that the constitutive models established in this paper are in accordance with the characteristic of the fiber reinforced concrete in loading process. The damage constitutive model in appendix C in code could be applied directly in some low precision calculation and engineering application.

Analysis on Mechanical Properties of the Integral Jacking-Up of an Ancient Building

The underpinning plate is the main load-bearing structure in the integral jacking-up process of ancient building. The deformation and mechanical properties of the underpinning plate have impact on the stability and the safety of the whole integral jacking-up process. The deformation and mechanical properties of the underpinning plate in the loading stage and after the partial unloading stage are analyzed with ANSYS in the integral jacking-up process of a certain ancient building. It is shown that the deflection of the prestressed underpinning beam satisfies the requirement of the design code in the loading stage and after the partial unloading stage, the concrete at the bottom of the underpinning edge beam will not crack in the loading stage and the concrete at the bottom of the underpinning edge beam will crack after the partial unloading stage.

Seismic Performance of Prestressed Reinforced Concrete Piles Reinforced with Nonprestressed Reinforcements

The main purpose of this paper is to study the seismic performance of prestressed reinforced concrete pile (PRC pile) reinforced with nonprestressed reinforcements. Two prestressed high strength concrete piles (PHC piles) and two PRC piles were tested. The variables studied in this research are the prestressed reinforcements ratio and nonprestressed reinforcements ratio. The piles subjected to low-cycle loading were presented in this paper, including the hysteretic performance, stiffness degradation curves, coefficient of equivalent viscous damping and skeleton-frame curves. It is shown that the failure modes of all specimens are bending damage from the test and PRC piles have good energy-absorbing hysteretic behavior.

Optimization of Top Steel-Tube Truss Construction Platform of Silo and Fitting of Curve Equation

The influence of length of chord and depth of truss on displacement and bearing capacity of truss construction platform was evaluated based on the results of the finite element analysis on eight different diameters of the top steel-tube truss construction platform of silo. The bearing capacity increases with increasing of depth of truss. The bearing capacity increases with decreasing of length of chord. The maximal displacement increases with increasing of the diameter in the same joint loads, and the displacement curve of model fits better.

The Strength and Deformation Analysis on the Top Steel-Tube Truss Supporting System of Silo

The influence of diameters and loads on the displacement of truss supporting system is evaluated based on the results of the finite element analysis on the steel-tube truss supporting system of silo. The vertical displacement increases with the increasing of the load. The displacement increases with the increasing of the diameter in the same loads. The maximal displacement appears in the intermediate position of the truss, and the displacements of symmetric nodes are similar under the symmetric loads. The member yields before 30m of truss supporting system reaches the allowable deflection.

Analysis on Flexural Bearing Capacity and Ductility of NHC Pile

The flexural behavior of non-holomorphic circular pile and cylindrical pile is respectively evaluated based on the results of finite element analysis with ABAQUS. It is presented that the ultimate bearing capacities of non-holomorphic circular pile and cylindrical pile have little difference. The displacement ductility ratio of non-holomorphic circular pile lies between 3.38 and 3.64, indicating that the NHC pile has better ductility.

Progressive Collapse Resistance of RC Structures with Tension Cables

In this study, three tie force models of a 10-storey concrete frame structure were prepared to investigate the effects of these methods on the resistance of frame structures against progressive collapse. Four cases of different first-storey column removed were considered using nonlinear static analysis method and their performances were compared with each other. From the nonlinear static analysis, the tie force methods in DoD 2005 and DoD 2009 cannot improve progressive collapse resistance of the structure because horizontal cables dont play a full role. X-type tension cables provide alternative load paths after loss of a single column, and improve progressive collapse resistance of the structure. The X-type tie force model remained in stable condition after sudden removal of a corner column, an exterior column, or an interior column in the first storey.

Push-over Analysis on the Failure Mechanism of Reinforced Concrete Frame Structure

A reinforced concrete frame model was designed by PKPM software and then a push-over analysis is performed in this paper. Values of plastic hinges were calculated by Section Builder software, which based on constitutive relations of material and the section forms, then the data was written into corresponding components in the model to carry out push-over analysis. The plastic hinges first appeared at the ends of beams in the first story ,spread to the second story and the ends of columns in the first story. At last plastic hinges spread to the top story. The story drift and interstory displacement rotation of the model in different cases tended to decrease as structural height increase. It can be demonstrated that failure mechanism satisfies the design requirements of strong column weak beam.

Seismic Analysis on RC Frame Strengthened with CFRP

A nonlinear finite element method is used to analyze the dynamic property of a five-storey reinforced concrete (RC) frame structure with and without carbon fiber reinforced plastic (CFRP). When the frame strengthened by CFRP, seismic performance of that is improved better than the frame without CFRP. The inter-story displacement angles of the frames with and without CFRP satisfy the seismic requirements from the results of earthquake transient analyses, when the frame is exposed to the frequent and rare earthquake.

Research on Judging Key Components for Collapse of Space Structures

The key components of space steel frame structures which included 1-5 story respectively were judged by using energy method. It was shown in the results that besides interior and corner columns, adjacent side columns in low buildings should be paid attention to in analyzing progressive collapse. The approach of utilizing story as weight to modify importance factor of space frame structure was also proposed, and the modified importance factor complied better with collapse resistant characteristics of real buildings.