Brief Analysis of Calculation and Calculation of Simply Supported Tied Steel Tubular Concrete Arch Bridge Ma Zhiming, Zhou Sisi, Sun Shulin, Gao Chengyun (Tianjin 3rd Survey and Design Institute, Tianjin 300142) (Tianjin Development Zone Corporation Municipal Corporation) Introduction of Rainbow Bridge Analysis and Scientific Experiment What to consider.
The Rainbow Bridge is located in the Beitang Bay of Bohai Sea where the Waiting Canal and Yongding Xinhe meet. It is connected to the Beitang Town Water Production Road in the south and the Hanbei Highway in the north. The 1215.69m approaching bridge has a double-span bridge with a bridge deck width of 27m and a south approach bridge of 11 holes. 25m, the north approach bridge is 14 holes and 25m, both are post-tensioned prestressed hollow slab beams. The transition between the main bridge and the approach bridge has a 50m prestressed concrete box girder. Due to the influence of flow ice and landscape requirements, the main bridge is used for 3 <168m (calculated span: 160m) simply supported down-steel CFST arch bridge with an arch height of 32m and a span ratio of 1:5. The arch axis is catenary with an arch axis of 1.5 and two holes per hole in the main bridge. Main arch rib, each arch rib is composed of two D1500mm<16mm steel pipes and two webs (16mm) welded into a dumbbell-shaped cross section with a section height of 3.75m and a transverse center distance of 19m for the two arch ribs. It is one of the key projects in Tianjin and is also a key scientific research project in Tianjin. It aims to solve the problem of using large-span arch bridges in soft soil foundations in coastal areas. The bridge adopts the rigid support of the simple support of the arch and the pier. The arch structure was adopted for the first time in China.
The calculation span spans 160m, which is also the maximum span of the domestic steel tube arch bridge. The bridge was started in August 1996. It was completed in November 1998. The overall layout of the main bridge is completed. See the analysis and calculation of the concrete-filled steel tubular arch structure using the finite element method. According to the plane mechanics model and the space mechanics model established by the specific requirements of structural stress, the static and dynamic analysis unit types are mainly composed of rod element beam unit, plate element and boundary element. The linear structure analysis adopts SAP84 developed by Peking University. Structural calculation analysis program, nonlinear analysis uses the ADINA structural calculation analysis program developed by the Massachusetts Institute of Technology, and also uses the bridge-specific finite element program for analysis and calculation. The main calculations are as follows: 1.1 Linear static structure calculation is mainly based on various Different calculation conditions, such as the effect of constant-load live-load wind, temperature, seismic force on the bridge structure and the calculation of the combined design conditions. Because the tie-pipe steel arch is an external static structure, the overall rise (fall) temperature of the structure Only cause the bridge structure to be uniformly deformed, and no stress is generated in the arch rib section, so the temperature force is calculated. The main consideration is the influence of local temperature field stress, that is, the arch foot and the tie rod are calculated according to the 10*c temperature difference. The arch foot section is calculated along the beam direction according to the exponential curve temperature mode. The influence of wind vibration is considered in the wind calculation. 1.2 Nonlinear static Force structure calculation The nonlinearity of arch bridge structure mainly refers to geometric nonlinearity. The influence of material nonlinearity can generally be ignored. According to the introduction, geometric nonlinearity has great influence on the arch structure during construction. For this reason, ADINA is used in the design. The linear structure analysis program calculates the displacement and internal force of the arch rib control section of each main bridge during construction. Through linear and nonlinear comparison calculation, the geometric nonlinearity of the bridge has a great influence on the vertical displacement of the arch rib, while the arch rib is affected. The influence of the axial force of the section is small, and the influence of the bending moment is also large. 1.3 The important factor of the space stability calculation system design. The steel arch is separated by the arch and the pier, and the stability is more prominent. See, the arch span is 32m high, and the vertical stiffness of the arch rib is much larger than the lateral stiffness. Therefore, the stability problem of the underline tie bar arch is mainly considering the out-of-plane of the arch rib. Stability problem 1.4 Dynamic characteristics The self-vibration characteristics of the bridge span are an important indicator for measuring the performance of the bridge. In the railway bridge verification specification, the limits of the vertical and horizontal natural frequencies of the bridge are specified. At present, when the natural vibration frequency of domestic highway bridges is not clearly defined, it is still desirable that the main bridge structure has a large rigidity, that is, the natural vibration frequency is high.
Since the main bridge adopts the simple-supported tie-bar steel pipe arch structure, it determines that the natural vibration frequency is not as high as the beam bridge height. Therefore, in the structural direction, sufficient attention should be paid to the flat joint position and connection mode of the arch bridge and the rigidity of the end beam. And compare and select, as far as possible, the natural vibration frequency of the arch bridge is improved. 1.5 Seismic force calculation The bridge is calculated by the seismic spectrum analysis using the response spectrum theory in the 8 degree seismic zone. The calculation results show that the bridge structure except the arch In addition to the large horizontal reaction force, the internal force generated by the arch rib section subjected to seismic loads is small, and the design is not controlled.
1.6 Construction process Computation of the whole bridge construction stage calculation, using a calculation model, a total of more than 30 construction stages, calculate the displacement and internal force of each stage of the arch rib. Since the concrete in the steel pipe is poured in the specified order, the arch rib section is different in each construction stage, and the dead load is continuously increasing. The final stiffness of the arch rib section is the sum of the corresponding section stiffnesses at each construction stage, in order to facilitate computer processing, The steel pipe is equivalent to the concrete section according to the principle of equal stiffness, and the dumbbell-shaped arch rib section is equivalent to the rectangular section with the same stiffness. 2 Test 2.1 Arch-foot photoelastic model test arch is in a three-direction stress state, the force is very complicated, construction In the process, the tie Rods are continuously tensioned at the arches for stress adjustment. Therefore, in addition to the finite element local calculation analysis of the plane and space of the arches, the photoelastic model test of the arch plane and space is also carried out. The stress distribution and the main stress trace of the arch are provided as the basis for the design. Considering the arch size and load, and the volume of the oven used for “freezing†stress, the ratio of the planar and spatial photoelastic test model to the actual structure is selected. The models are 1:125 and 1:100 respectively. The model simulates the effect of 8 tie rod cables in the arch. The space stability problem is for i. The arch bridge is a loading condition of the two groups of the most unfavorable work brothers who control the arch design. The overall model test system of the 2.2-bar arch model is based on the layered infusion of steel pipe arch ribs during the construction phase. In the overall model, the main section stress, joint displacement and tie rod axial force of the corresponding stage are measured, and the vibration characteristics of the model are also determined. The purpose of the model test is to verify the calculation method, the construction process and the safety evaluation after the bridge. Considering the materials made by the model, the concrete infusion process, the loading scheme and the test method, the ratio of the selected model is 1:202.3 large tonnage static test pile test. There are 40 Y150cm long 56m holes under the main pier cap of the bridge. Perfusion, each design limit bearing capacity is 15 000kN, which is the longest and most bearing capacity of the Tianjin area at that time. According to the requirements of the design specifications, the test pile static test must be carried out using the slow maintenance load method. The reaction force of the root anchor, two reaction steel beams and two secondary beams is applied to the top by the high-pressure oil pump in parallel with four 500t synchronous jacks. The test is carried out according to the procedures and judgment methods specified in the specification. According to the main soil layer, the pre-embedded string type steel bar is divided into sections, and the axial force transmission change process of the body is measured. Then the limit or maximum frictional resistance of the soil is calculated by the axial force, and a pressure box is buried at the bottom to measure End resistance.
2.4 Large tonnage-based dynamic test The high-strain dynamic test requires a large hammering energy impact head to make the head high-strain and produce a certain penetration degree. The stress and acceleration signals near the top are collected by the sensor of the analysis system. The data of the analysis of the origin stress and ultimate bearing capacity can be matured in China. It is a kind of non-destructive dynamic testing method widely used in China. It is a large-tonnage high-strain dynamic test for domestic large-tonnage strains. The high strain power test of the bridge has accumulated valuable information for the large tonnage test in Tianjin. The high-strain dynamic test is based on the mutual movement with the soil. Only when the lateral and tipping soil resistance is fully exerted, the accurate bearing capacity can be obtained. The bridge dynamic test hammer weight is 13t, and the penetration degree is 2mm2.5. Due to the constraint of the steel pipe on the concrete, the core concrete will be subjected to the triaxial pressure, so that the compressive strength toughness and deformation ability of the concrete can be greatly improved. However, due to the influence of materials and processes on the concrete inside the steel pipe, defects such as debonding often occur. , empty, etc. There is no good method for the detection of concrete in steel pipes. Although China has formulated the "Method for Ultrasonic Measurement of Concrete and Reinforced Concrete". However, there are no regulations for the detection of concrete-filled steel tubes. In particular, the ultrasonic testing of the arched steel box concrete of the Rainbow Bridge is more difficult. The ultrasonic testing of the bridge is used to evaluate the strength of the concrete, and the monitoring of the concrete is carried out by the expert 2.6. The arch adopts external static setting, internal statically-determined structural system, and the arch rib thrust is fully supported by the tie rod. At different construction stages, the internal tension is continuously tensioned and the internal force is adjusted. The construction is difficult and requires high construction technology. . In order to ensure the construction safety and engineering quality of the bridge, in accordance with the provisions of the Ministry of Communications on the construction monitoring of large-span bridges, the internal force, deformation and tie-tension of the arch ribs shall be monitored during construction, and the monitoring data shall be analyzed in time. Adjust the construction plan and loading sequence, coordinate the relationship between the arch rib and the bridge load and the tie tension of the tie rod, and guide the tie rod tension so that the arch rib is in the best stress state.
2.7 tie-bar arch bridge static and dynamic load test The bridge adopts the bottom-supported simply-supported steel-tube concrete arch bridge. The span of the bridge is large and the structure is novel. In order to verify the working performance of the bridge structure, verify the correctness of the design theory and ensure the reliability of the bridge operation. The bridge provides a full bridge static and dynamic load test for the bridge completion acceptance and future bridge maintenance and repair. The test is based on the "long-span concrete bridge test method" and "road bridge and culvert design specification" and relevant design requirements of the Ministry of Communications, including static load section stress, deflection, fulcrum displacement and angular dynamic load stress, dynamic load deflection. The static vibration test of the vibration response of the bridge and the natural vibration characteristics of the bridge are loaded according to the requirements of the measuring point. The dynamic load test is divided into the driving test, the jumping test and the pulsation test.
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