EFFECT OF VEHICLE QUALITY AND SPEED ON THE IMPACT CHARACTERISTICS OF AN OVERPASS BRIDGE PIER

To study the impact of the mechanical characteristics of heavy trucks on piers under different masses and speeds, a new equivalent simplified model of heavy trucks is proposed in this paper. The reliability of the calculation model is verified by studying the pier of the G1011 Ha-Tong high-speed K302+095 separated overpass, which was subjected to impact by a heavy truck. A finite element model of a heavy truck and a pier is established using the finite element software ABAQUS, and the influence of heavy truck load and impact speed on the impact force and pier stress is analysed. Results show that the peak of impact force increases with the increase in the mass and impact speed of heavy trucks. The high-stress area of the pier is concentrated in the root and the impact position, and an inclined through-crack is formed at 45° with the pier axis. The results also reveal the influence law of the quality of heavy trucks and impact speed on the impact force and stress of the pier and provide a new theoretical basis for the anti-collision design of piers and the limitation of current specifications on the high-speed impact of heavy trucks on piers

PERFORMANCE ANALYSIS OF HIGH STEEL TUBE LATTICE SUPPORT SYSTEM IN TYPHOON AREA

Research on safety of high steel tube lattice support systems in typhoon areas is still in the preliminary stage. The purpose of this paper is to study the overall buckling and overturning stability of the high steel tube lattice support systems in typhoon area. By constructing the spatial finite element model of the high steel tube lattice support system via MIDAS Civil, the optimal design of the steel tube lattice support system is carried out through the analysis of the main influencing parameters. The stability of steel pipe lattice support system is calculated theoretically, and the optimal design of steel pipe lattice support system is studied by finite element numerical method in Typhoon area. The calculation results show that Critical buckling load coefficient increases with the increase in diameter of the steel tube when the δ/d ratio of steel pipe structure is fixed. The critical load factor of the six-limb support system is slightly larger than that of the four-limb support system. When the transverse space of the support system is from 5 m to 7 m, stability increases rapidly. The best stability of the support system is obtained when the transverse space is approximately 7 m. The diagonal brace can significantly improve the stability of the steel tube lattice falsework

Experimental study on real bridge before and after simple-supporting to continuous reinforced concrete hollow slab

This article studies a concrete hollow slab simply supported-continuous actual engineering project in a certain city. Before the reinforcement of the bridge, there were cracks and exposed rebars, etc. In order to ensure the safe operation of the bridge, a reinforcement method of simply supported-continuous was adopted, prestressed steel strands are used to convert the simple-supported structure into a continuous structure, thereby improving the structural load-bearing capacity and overall integrity. Through conducting comparative analysis of load tests on a bridge before and after reinforcement, this article studies the improvement effect of the simply-supported-to-continuous reinforcement method on the bearing capacity of the bridge. A finite element model of the bridge was established, and comparative analysis was carried out before and after the reinforcement of the bridge. The bearing capacity and work performance of the bridge structure were evaluated. The research shows that the simply supported-continuous reinforcement method has a good improvement effect on the load-bearing capacity of the concrete hollow slab and can be used to improve the insufficient load-bearing capacity of the concrete hollow slab bridge in the city

ANALYSIS AND OPTIMIZATION OF WIND RESISTANCE PARAMETERS FOR LATTICE-TYPE HIGH-MODULUS SUPPORTS BASED ON THE OPTIMAL CRITERIA METHOD

Lattice high-molded support can generally be used for cast-in-place support for bridges, but for more than 50 meters of lattice high support, due to the wind, load and other factors, due to the support length and slenderness of the relatively large, relatively light and flexible structure and other characteristics of the role of the wind load is very sensitive. When the lattice high-molded stent construction is used in the typhoon area, it is easy to be damaged by the typhoon, and the structural design of the lattice high-molded stent and the construction of that technology are facing great challenges. In this paper, based on the new construction of a special bridge in Fujian, finite element analysis of four-legged and six-legged lattice bracing is carried out by ANSYS, and the effects of steel pipe diameter, number of columns, longitudinal and transversal spacing of bracing, and diagonal bracing structural parameters on structural performance are analyzed by using the coefficients of buckling stability and the coefficients of critical loading. The results of the study show that the main design variable for displacement sensitivity is the diameter of vertical rod; the main design variable for stress sensitivity is the diameter of diagonal rod; the main design variable for overall stability sensitivity is the diameter of diagonal rod; and the main design variable for overall stability sensitivity of total volume is the diameter of diagonal rod. And the optimal wind resistance parameters are: 4 lattice high-braced columns are selected, the section length should be controlled within 15m, and the total height should not be more than 70m, and the spacing of the columns is controlled between 7m and 8m. This study proposes a set of optimized design process method for wind-resistant lattice structure under the constraints of stiffness, strength and critical load factor, which improves the economy and ensures the reasonableness of the design, and can be used for the design of high-modular lattice bracket in typhoon area

Synchronization of Chaotic Neural Networks with Leakage Delay and Mixed Time-Varying Delays via Sampled-Data Control

This paper investigates the synchronization problem for neural networks with leakage delay and both discrete and distributed time-varying delays under sampled-data control. By employing the Lyapunov functional method and using the matrix inequality techniques, a delay-dependent LMIs criterion is given to ensure that the master systems and the slave systems are synchronous. An example with simulations is given to show the effectiveness of the proposed criterion

ANALYSIS OF CONTACT FRICTION BEHAVIOR IN THE BENDING PROCESS OF SEMI-PARALLEL STEEL WIRE CABLE

In the bending process of semi-parallel steel wire cable, with the increase of the lateral displacement of the bending, the interaction between the steel wires in the cable is remarkable and the mechanical behavior is complicated. In order to study the mechanical behavior of the contact friction between the inner steel wires in the process of cable bending, this paper uses the 37-φ7 semi-parallel steel wire as the research object, and uses the ANSYS to set up the finite element model of the cable bending, and verifies the correctness of the refined finite element model by bending test data. Based on the refined finite element model of the test data verification, the variation rule of the contact friction between the inner steel wires in the semi-parallel steel wire of different boundary conditions in the bending process is studied, and the axial sliding behavior of the steel wires in the cable bending process is analyzed. The results show that the bending and mechanical properties of the semi-parallel steel wire cable can be calculated more accurately by considering the refined finite element model of the contact friction, and the amount of deformation between the steel wires during the bending process of the semi-parallel steel wire cable can be calculated. The contact pressure and the contact friction stress are non-linear with the increase of the lateral displacement of the bending, and there is a maximum value for the contact friction stress for the pre-tension semi-parallel wire cable, and the maximum position of the axial accumulated slip amount between the steel wires is located at the bending cable section of the calculated span of 1/4 or 3/4 times

FIELD TEST ON THE COOPERATION OF NSM STRENGTHENING AND EXTERNAL TENDON RETROFITTING TECHNIQUE

In this paper, post-tension and steel plate near-surface mounted (NSM) strengthening systems are proposed to strengthen deteriorated and cracked large box girder rigid frame bridge without altering appearance and dimension of the bridge. The reinforcement method mainly improves the bearing capacity through external prestressed tendons, and bonding steel plate can enhance the shear resistance of the bridge. The main purpose is to study the structural mechanical properties before and after the reinforcement of rigid frame bridges. Take a 540m rigid frame box girder bridge as an example. The static load test of the bridge before and after reinforcement is carried out. The deflection and strain of the middle cross section of the span are measured in the static test. A finite element analysis model was also developed and verified static loading test data. The results show that structural bearing capacity and performance of the bridge were enhanced with the post-tension and NSM strengthening systems cooperatively

Study on Temperature Force Control Mechanism of CRTSⅡ Slab Track: Control Conditions of Temperature Cracking

Diseases such as track slab arching and joint concrete crushing of China Railway Track System (CRTS)II slab track were caused by huge temperature force, which seriously threatens driving safety of trains. In this study, a longitudinal weak connection scheme of CRTSII slab track was proposed to adjust the temperature force in track slab and reduce diseases of longitudinal continuous track slab. This paper focuses on the cracking characteristics of the longitudinal heterogeneous concrete composite structure. The equation which was originally developed to calculate crack width and structure stress under temperature loads, was put forward to consider deformation difference of different elastic modulus. The influence law of various parameters was analyzed. The reinforcement stress and crack width of CRTSII slab track after longitudinal connection weakening were calculated, and the reasonable limit value of tensile force of connection reinforcement and the minimum value of bond resistance of reinforcement in joint position were obtained. The result shows that, in order to reduce the bond resistance between the joint material and the reinforcement, the elastic modulus of the elastic material should be less than 5000 MPa; in order to ensure that the reinforcement does not produce large stress, the elastic modulus of the joint should be greater than 1000 MPa

Target control of complex networks

Controlling large natural and technological networks is an outstanding challenge. It is typically neither feasible nor necessary to control the entire network, prompting us to explore target control: the efficient control of a preselected subset of nodes. We show that the structural controllability approach used for full control overestimates the minimum number of driver nodes needed for target control. Here we develop an alternate ‘k-walk’ theory for directed tree networks, and we rigorously prove that one node can control a set of target nodes if the path length to each target node is unique. For more general cases, we develop a greedy algorithm to approximate the minimum set of driver nodes sufficient for target control. We find that degree heterogeneous networks are target controllable with higher efficiency than homogeneous networks and that the structure of many real-world networks are suitable for efficient target control