Numerical simulation and control of welding distortion for double floor structure of high speed train

The welding heat source models and the plastic tension zone sizes of a typical weld joint involved in the double floor structure of high speed train under different welding parameters were calculated by a thermal-elastic-plastic FEM analysis based on SYSWELD code.Then,the welding distortion of floor structure was predicted using a linear elastic FEM and shrinkage method based on Weld Planner software.The effects of welding sequence,clamping configuration and reverse deformation on welding distortion of floor structure were examined numerically.The results indicate that the established elastic FEM model for floor structure is reliable for predicting the distribution of welding distortion in view of the good agreement between the calculated results and the measured distortion for real double floor structure.Compared with the welding sequence,the clamping configuration and the reverse deformation have a significant influence on the welding distortion of floor structure.In the case of30 mm reverse deformation,the maximum deformation can be reduced about 70%in comparison to an actual welding process.

Test and Analysis of the Sound Insulation Performance of Four Types of Timber Structure Floors under Jumping Excitation

To improve the impact sound insulation performance of building floors and meet the objective requirements for living comfort of residents,in this article,three kinds of elastic cushion materials,Portuguese cork board,BGL insulation sound insulation foam board,and EPP polypropylene plastic foam board,are applied to the sound insulation of a light frame wood floor structure of the same bedroom and compared to the ordinary floor.This study uses the transfer function method and transient excitation method to measure the sound insulation,damping ratio,and elastic modulus of materials,as well as the sound insulation of the floor under the jumping excitation method of daily behavior.Through comparative analysis,the results and factors of improving the sound insulation performance of the floor are obtained,according to which three types of elastic cushion materials and the floor covering composed of them have higher vibration and noise reduction performance.Among them,the overall sound insulation performance of BGL board floor is the highest,followed by EPP board and cork board floor,and ordinary OSB floor is the lowest.Under the jumping excitation method,three floating floors can improve the impact sound insulation performance of the middle and low-frequency bands.

Experimental study of low-temperature electrical radiant floor heating system

To evaluate the thermal performance of a low-temperature electrical radiant floor heating system,an experimental facility equipped with a constant temperature chamber and different specimen floors is designed and built.The heating cable is installed in the floor slab with a unit-rated power of 30 W/m.Twenty-four different schemes are worked out and tested,which include three kinds of composite floor structures and eight kinds of cable distances.The cable distances are 30,40,50,60,80,100,130,150 mm.The main affective factors of the thermal performance and their influencing regularity are discussed.The experimental results show that the system has good stability and reliability,and the ratio of the radiation heat-transfer rate to the gross heat-transfer rate is greater than 50%.When the floor structure and the cable distance are fixed,the gross heat-transfer rate of the upper floor surface has a maximum value at an optimal cable distance.Under the experimental conditions in this paper,the optimal cable distance is 50 mm.

Experimental study on the seismic performance of staggered slab-column joints

The low-cycle loading test of two staggered slab-column-boundary beam joints was carried out to study their seismic performance.The crack development,load-displacement relationship,displacement ductility,and energy dissipation performance of the staggered slab-column joints(SSCJ)were studied.Experimental results reveal that both specimens present short-column brittle shear failure.Furthermore,an obvious hysteretic curve pinching phenomenon occurred.Thus,it can be concluded that the seismic performance of the joints is insufficient.These results suggest that the anchorage of the longitudinal reinforcement of the slab in the joint’s core area should be improved,and attention should be paid to the short-column stirrup configuration of the SSCJ.These results can provide a research basis for the design of such joints in future applications.

Deflection test and modal analysis of lightweight timber floors

In order to meet the objective requirements of the safety and comfort of the modern lightweight timber floors,and strengthen the research on the coupling performance of the lightweight timber floors vibration characteristics and the building comfort,this article discusses the floor of a two-story prefabricated lightweight timber building demonstration house.In this paper,the floor structure of a two-story light-weight wooden house has been carried out on structural calculation modal and experimental modal,static uniform load and concentrated load deflection value testing.The evaluation of the deflection value of the floor structure,the mode shape,the coupling of the fundamental frequency mode parameters,and the vibration comfort were also studied.The results show that the fundamental frequency simulation value,one-way modal test value and two-way modal test value of the floor structure all meet the requirements of BS-6472(BS6472-1:2008).That is,the floor structure is not lower than 8 Hz design requirements,and meets the frequency of BS-6472(BS6472-1:2008).The weighted root mean square acceleration is lower than the requirement of 0.45 m/s^(2);the first three natural frequencies of the floor structure calculated by the finite element simulation are 16.413,31.847 and 48.921 Hz,and the fundamental frequency mode is the bending vibration in the length and width directions.The second order is the bending mode in the length direction,and the third order is the bending mode in the width direction.The fundamental frequency of the two-way modal test of the floor structure is the first-order bending mode in the X direction;and the second-order natural frequency is the second-order bending vibration shape in the X direction.when the uniform load is mainly the weight of floor own,the simulated maximum deflection value is 1.0658 mm;the simulation is performed according to the standard value of 0.566 kN/m for the uniform load of the floor design,and the simulation is the largest.The maximum deflection value of the simulated floor is 1.47383 mm at its midpoint,which meets the requirements of National Building Code of Canada-2015(NBCC).The maximum deflection limit of the light wood structure floor system is lower than 3 m and the maximum deflection limit is 2 mm;the six deflection value test lines simulated under a concentrated load of 1 kN all present a parabolic distribution and are symmetrical.The above results has engineering application value for promoting the research on the vibration characteristics of the fabricated lightweight timber floors structure and its optimization design.