Research On Influence Surfaces, Enveloping Surfaces And Simplified Calculation Of Local Stresses Of Orthotropic Deck In Steel Box Girder For Highway Suspension Bridge

(1) In accordance with mechanical behavior of orthotropic deck, as well as problems and difficulties produced in the bridge use process, investigation and research were done on such issues of orthotropic deck in steel box girder at home and abroad, as evolutions of structure details, as vehicle load, constructional detail requirements and relevant rules in the specifications, and as typical structural design in practice. On the other hand, all these efforts were done for the standards setting of Guidelines for Design of Highway Suspension Bridge.(2) Aiming at the problem that it’s difficult to calculate the accurate stresses of orthotropic deck in steel box gird for highway suspension bridge, the concept of "local stresses of orthotropic deck" based on spatial structure calculation was put forward including transverse stress and longitudinal stresses of deck and longitudinal stress of rib. The local stresses contain connotations of the orthotropic deck structure system (system Ⅱ) stress and the deck plate system (system Ⅲ) stress in traditional calculation. It would become convenient to superpose overall stresses of the main structure members system of bridge (system Ⅰ) and above local stresses. Then the total stresses of orthotropic deck could be calculated directly by this way.(3) According to the survey of basic dimensions of orthotropic deck in steel box girder for highway suspension bridge, typical structural was selected, and spatial structure beam segment model was built using cell elements. After applying140kN axle load of the back wheel in the standard class Ⅰ highway vehicle load given in our national code,1806load cases were calculated in the3typical load models. Then the influence lines were researched on such orthotropic deck’s local stresses as transverse and longitudinal stresses of deck and longitudinal stress of rib. Influence regulations of load longitudinal position on local stresses were analyzed.(4) Taking more disadvantageous load model and adding602load cases for the30kN axle load of the front wheel in the standard vehicle load, such stress histograms under the action of the standard class Ⅰ highway vehicle load were drawn in the manner of superposition method using above influence lines of local stresses. By means of extracting and organizing maximal and minimum local stresses of every point, enveloping lines were researched for the positions of outside wheel of the heavy traffic lane and inside wheel of the fast traffic lane. Then the part of the structure where produced the most disadvantageous local stress and the corresponding longitudinal location of the vehicle load were explored.(5) Based on the typical structure of orthotropic deck in steel box girder of highway suspension bridge selected, longitudinal and transverse acting ranges of vehicle load were confirmed in allusion to the4regions near hanger and mid-span of heavy traffic lane and fast traffic lane. After23668load cases calculated, influence surfaces of the local stresses as transverse and longitudinal stresses of deck and longitudinal stress of rib were researched. Then further effects of the load plane position on orthotropic deck’s local stresses were analyzed.(6) By means of extracting and organizing the data of about370million deck’s local stresses of all load cases in the4regions, the enveloping surfaces were researched of such6kinds of local stresses as the maximal transverse tensile stress and transverse compressive stress in deck, maximal longitudinal tensile stress and longitudinal compressive stress in deck, and maximal longitudinal tensile stress and longitudinal compressive stress in rib. Furthermore, distribution regulation of local stresses and the critical structural details were discovered.(7) Then sensitivity analysis was done for orthotropic deck’s local stresses in steel box girder of highway suspension bridge. Selecting3type parameters of structure, load and calculating model, totally11items, the influences of these parameters to local stresses were researched. After choosing such6important parameters as deck thickness, rib thickness, girder height, diaphragm distance, the number of diaphragm internodes between two adjacent suspenders and pavement thickness,158400load cases were analyzed according to totally3600parameter combinations and7200calculating models. Furthermore, the influences of multi-parameter to local stresses were researched. For every structure of various parameter combinations, the most disadvantageous local stresses, and relevant parts of structure and position of load were confirmed.(8) Based on regression analysis of large number of calculated data, a simplified calculated method was put forward to gain such6kinds of local stresses of orthotropic deck in steel box girder of highway suspension bridge, as the maximal transverse tensile stress and transverse compressive stress in deck, maximal longitudinal tensile stress and longitudinal compressive stress in deck, and maximal longitudinal tensile stress and longitudinal compressive stress in rib. A unified and relatively simplified formula was deducted. Every reference value of local stress and simplified coefficient was calculated, and further tables and curves were drawn for all the coefficients. Error analysis was done for calculated values from the simplified formula. Taking the Haicang Suspension Bridge over East Channel, the South Suspension Branch of Runyang Yangtze Bridge and Taizhou Yangtze Bridge as the example, verification of the simplified calculated method was carried out.