Study on Model Experiment of Prestressed Concrete Skewed Box Girder with Transversely Segmental Construction

he　prestressed　concrete　skewed　box　girder　with　transversely　segmental　construction　was　brought　out　on　the　basis　of　the　need　in　the　engineering,both　model　experiments　and　FE　analysis　of　the　presented　construction　and　the　beam　box　with　integral　construction　were　carried　out　With　the　analysis　of　the　obtained　data　by　mathematical　statistics,comparison　of　table　and　graph,and　the　corresponding　FE　analysis,the　difference　of　mechanical　performances　of　both　constructions　was　analyzed　under　various　experimental　loading　cases　The　results show　that　(1)　the　deflection　of　the　presented　construction　is　about　53%　larger　than　that　of　the　beam　box　with　integral　construction,the　longitudinal　strain　is　135%　larger　than　that　of　the　latter,and　the　longitudinal　strain　of　the　cast　concrete　is　59％　as　large　as　that　of　the　same　area　at　the　beam　box　with　integral　construction　before　concrete　cracking;　(2)　there　exists　stress　redistribution　in　the　cross-section　of　presented　construction,which　can　restrain　the　tensional　distortion　of　the　wet?joint,and　the　value　of　the　stress　cannot　be　computed　by　the　current　FE　program     

Experimental Research on Fatigue Behavior of Reinforced Concrete Reams Strengthened with HPFL under Overloading Conditions

In　order　to　study　the　fatigue　behavior　of　RC　beams　strengthened　with　High　Performance　Ferrocement　Laminates　(HPFL)　under　overloading　conditions,static　and　fatigue　experiments　were　conducted　on　two　control　beams　and　nine　strengthened　beams　The　failure　mode,fatigue　life,deflection　and　material　strain　under　overloading　conditions　were　analyzed　The　result　shows　that　(1)　fatigue　failure　of　the　beams　subjected　to　overload　starts　with　steel　rupture　at　the　bottom　and　the　fatigue　life　is　only　between　327　000　and　668　000　while　fatigue　 life　of　strengthened　beams　is　greater　than　two　million　times　in　case　of　not　overload ing;　(2)　compared　with　the　control　specimen,the　fatigue　life　of　strengthened　beams　is　obvio usly　extended　and　increased　with　the　increase　of　steel　mesh　consumption;　(3)　after　the　same　number　of　cycles,the　deflections,the　strains　of　concrete　and　steels　of　four　strengthened　beams　are　lower　than　those　of　the　control　specimen　Debonding　at　the　interface　of　HPFL　and　concrete　is　not　observed　because　of　shear　pins　planted　at　the　end　of　the　beams     

Research on Heat Transfer Model of Asphalt Pavements Subjected to Microwave Heating Recycling

In　order　to　assess　temperature　field　in　microwave　heating　for　recycling　asphalt　pavements,a　2D　mathematic　heat　transfer　model　was　developed　based　on　Fourier　heat　transfer　theory　The　microwave　internal　heat?generation　was　researched　by　using　surface　field　of　pyramidal　horn　replacing　approximate　radiation　field　In　addition,the　boundary　conditions　were　built　and　normalization　processing　was　implemented　The　control　volume　based　finite　differential　method　(CV-BDM)　was　used　to　establish　the　implicit　discrete　scheme　of　the　conservation equations,and　the　numerical　value　simulation　was　employed　By　continuous　or　intermittent　 radiation　heating　technique,a　microwave　heating　experimental　system　at　2　145　GHz　was　carried　out　to　investigate　temperature　variation　characteristics　of　asphalt　pavements　along　with　heating　time　The　result　shows　that　(1)　the　increase　of　temperature　of　asphalt　mixture　during　microwave　heating　is　obviously　nonlinear,the　temperature　rises　slowly　in　the　initial　stage　of　the　heating　but　increases　rapidly　in　the　late　heating　period;　(2)　the　temperature　distribution　is　non-uniform　that　the　temperature　in　central　area　of　the　surface　is　higher　while　it　is　lower　on　edge;　(3)　the　uniformity　of　temperature　within　asphalt　mixtures　can　be　improved　by　using　intermittent　heating　technique,and　the　heating　time　must　be　reasonable　The　simulation　results　are　in　preferable　agreement　with　the　experiment     

Research Progress and Prospect on Dynamic Response of SFT Structures(悬浮隧道结构动力响应研究进展与展望)

Construction of submerged floating tunnel （SFT） is one of the major solutions for fjord crossing projects and deep sea crossing projects in the future. Aimed to solve the key problems in SFT construction, the authors present an overview on the progress of the researches made in China and other countries in recent years on cross section of SFT, dynamic response of SFT segment structure, vortex induced vibration of anchor cable, testing technique and applicability of SFT, summarize the critical problems in the dynamic response research of SFT structures and make prospect on the trend of further SFT research. Conclusions are drawn as follow: (1) In the aspect of cross section design, SFT with ear shaped or elliptical cross section has good stability in the complex environment of flowing water, with factors comprehensively considered, such as cross section of SFT segment structures, buoyancy weight ratio and layout. (2) In the aspect of dynamic response of structures and anchor cables, the current research methods are mainly based on theoretical derivation and numerical simulation, and poorly rely on model based testing technique; therefore, it is necessary to perform model tests under combined loads from the environment, traffic and SFT, for mutual check between the theoretical analysis and numerical model. (3) In the aspect of applicability, it is necessary to build small SFT in feasible water conditions to make research on the physical SFT in the static waters, to identify problems and to lay a foundation technically for building large SFTs in the complex sea conditions.