Behaviour of a Moment Resisting Composite Steel and Concrete Joint Under Alternate Loading

The authors show the results of a study conducted on a joint connecting a concrete column to a composite steel concrete floor,subjected to tension on the beams as a result of the decomposition of sagging bending moment.The beam to column connection is achieved by means of headed studs welded to the beam and embedded in the concrete cast.Five different configurations have been tested at failure and the results are compared to formulae proposed in literature.Different degrees of ductility,reliability and strength have been obtained varying geometry and reinforcement ratio on the joints tested.

A general alternate loading technique and its applications in the inverse designs of centrifugal and mixed-flow pump impellers

For the inverse designs of centrifugal and mixed-flow pump impellers,clarifying the generation process of secondary flows and putting forward corresponding suppression measures is an important approach to improve the impeller performance.In this paper,to provide a better qualitative insight into the generation mechanism of secondary flows in the impeller,a simple kinematic equation is derived based on the ideal assumptions,which indicates that the potential rothalpy gradient(PRG)is the most important dynamic source that actively induces secondary vortical flows.Induced by the natural adverse PRG on the S1 and S2 stream surfaces,two typical secondary flows,H-S and P-S secondary flows,are clearly presented.To specially suppress these typical secondary flows,a general alternate loading technique(GALT)is proposed,aiming to adjust the real blade loadingδp to control the PRG features.At the blade fore part,theδp on the hub streamline should be slowly increased to avoid breakneck growth of the potential rothalpy to reduce adverse streamwise PRG on the S2 streamsurface.At the blade middle part,theδp should be moderately decreased to reduce adverse streamwise PRG on the S1 streamsurface.At the blade aft part,the difference in theδp between the shroud and hub streamlines should be decreased faster to control the exit uniformity.By applying the GALT to the impeller designs of three typical pump types in hydraulic engineering,the organizational effect of the PRG on fundamental flow structures is proven.The GALT can effectively control the PRG distributions and suppress the secondary flows,thereby widening the pump’s high-efficiency zone,improving flow uniformity and suppressing pressure fluctuations.Compared with the current Z-G method and the ALT,the GALT can meet the requirements of"de-experience"better,thereby enabling the designers to obtain good products explicitly and quickly.

Progressive Collapse Resistance of a New Staggered Story Isolated System

A new staggered isolated system developed from the mid-story isolated system is the new staggered story isolated system. There are not many studies on this structure currently. In this study, an 18-story new staggered story isolated system model is established using SAP2000. The dynamic nonlinear dynamic alternate method is used to analyze the structure against progressive collapse. Results show that the structure has good resistance to progressive collapse, and there is no progressive collapse under each working condition. The progressive collapse does not occur for the case of removing only one vertical structural member of the new staggered of isolated system. The side column has big influence on this isolated structures’ progressive collapse;the removal of vertical structural member of the isolation layer has less impact on the structure than the removal of the bottom vertical structural member. After the removing of the member, the internal force of the structure will be redistributed, and the axial force of the adjacent columns will change obviously, showing a trend of “near large and far small”.

Optimal Scheduling of Regional Integrated Energy Systems Considering Hybrid Demand Response

Flexible load can optimize the load curve,which is an important means to promote renewable energy consumption.The peculiarities of electricity,heat,cooling and gas loads are analyzed in this paper,considering the fuzzy degree of human perception for water temperature,and the characteristic model of hot water load is established.Considering the fuzzy degree of human perception of ambient temperature,the characteristic model of cooling load is established by using PMV and PPD index.Meanwhile,considering four combinations of cut load,translatable load,transferable load and alternative load,and considering the coupling relationship of composite parts,different response models of load are established respectively.With the minimum cost of the system,including operation and compensation costs as the objective function,the optimization scheduling model of the regional integrated energy system is established,and the Gurobi solver is used for simulation analysis to solve the optimal output and load response curve of each piece of equipment.The results show that the load curve can be optimized,the flexible regulation ability of the regional integrated energy system can be enhanced,the energy loss of the system can be reduced,and the wind power consumption ability of the system can be increased by considering the integrated demand response.

Evaluation of the dynamic sealing performance of cap rocks of underground gas storage under multi-cycle alternating loads

The static sealing of underground gas storage(UGS),including the integrity of cap rocks and the stability of faults,is analyzed from a macro perspective using a comprehensive geological evaluation method.Changes in pore structure,permeability,and mechanical strength of cap rocks under cyclic loads may impact the rock sealing integrity during the injection and recovery phases of UGS.In this work,the mechanical deformation and failure tests of rocks,as well as rock damage tests under alternating loads,are conducted to analyze the changes in the strength and permeability of rocks under multiple-cycle intense injection and recovery of UGS.Additionally,this study proposes an evaluation method for the dynamic sealing performance of UGS cap rocks under multi-cycle alternating loads.The findings suggest that the failure strength(70%)can be used as the critical value for rock failure,thus providing theoretical support for determining the upper limit of operating pressure and the number of injection-recovery cycles for the safe operation of a UGS system.

Investigation on a mitigation scheme to resist the progressive collapse of reinforced concrete buildings

This study presents the investigation of the approach which was presented by Thaer M.Saeed Alrudaini to provide the alternate load path to redistribute residual loads and preventing from the potential progressive collapse of RC buildings.It was proposed to transfer the residual loads upwards above the failed column of RC buildings by vertical cables hanged at the top to a hat steel braced frame seated on top of the building which in turn redistributes the residual loads to the adjacent columns.In this study a ten-storey regular structural building has been considered to investigate progressive collapse potential.Structural design is based on ACI 318-08 concrete building code for special RC frames and the nonlinear dynamic analysis is carried out using SAP2000 software,following UFC4-023-03 document.Nine independent failure scenarios are adopted in the investigation,including six external removal cases in different floors and three removal cases in the first floor.A new detail is proposed by using barrel and wedge to improve residual forces transfer to the cables after removal of the columns.Simulation results show that progressive collapse of building that resulted from potential failure of columns located in floors can be efficiently resisted by using this method.

Deep reinforcement learning-based critical element identification and demolition planning of frame structures

This paper proposes a framework for critical element identification and demolition planning of frame structures.Innovative quantitative indices considering the severity of the ultimate collapse scenario are proposed using reinforcement learning and graph embedding.The action is defined as removing an element,and the state is described by integrating the joint and element features into a comprehensive feature vector for each element.By establishing the policy network,the agent outputs the Q value for each action after observing the state.Through numerical examples,it is confirmed that the trained agent can provide an accurate estimation of the Q values,and handle problems with different action spaces owing to utilization of graph embedding.Besides,different behaviors can be learned by varying hyperparameters in the reward function.By comparing the proposed method and the conventional sensitivity index-based methods,it is demonstrated that the computational cost is considerably reduced because the reinforcement learning model is trained offline.Besides,it is proved that the Q values produced by the reinforcement learning agent can make up for the deficiencies of existing indices,and can be directly used as the quantitative index for the decision-making for determining the most expected collapse scenario,i.e.,the sequence of element removals.

Experimental investigations on triggering characteristic of TVS under DC and AC load

Triggered vacuum switches(TVSs)have fast growing applications in the field of power system and pulse power.The relation between triggering parameters of triggering system,such as triggering voltage and triggering power,between the triggering time delay and its scatter of TVS had been obtained through series of experiments.The result can be adopted as the steering for high-power controller design and application of TVS.A steepened high-voltage triggering pulse is introduced in the main high-voltage generating circuit.As a result,the triggering time delay and its scatter can be decreased remarkably.Synchronous switch technology is imported to control the triggering phase at the crest of applied voltage on TVS.The Triggering characteristic of TVS under alternating current(AC)and direct current(DC)load has been investigated emphatically.Given the identical triggering parameter of triggering system,DC condition is prior to AC on the triggering probability and stability markedly.Such conclusion can be drawn,for AC condition,TVS would require much for the triggering system.