Papers by Keyword: Load Combination

Abstract: In this paper, differences by using selected three typical specifications—DL/T 5141-2001 (Chinese), ASCE No.79 in the version of 1993(American) and ASCE No.79 in the version of 2012 (American)—in structural design of exposed steel penstock were explored. A practical example about exposed penstock laid on ground applied in hydropower station was also used to analyze specifications clearly. The result shows that the main differences between Chinese and American specifications are allowable stress and load combination. The former is direct factor of calculating exposed penstock shell thickness. Therefore, ASCE No.79 (2012) designs the minimum wall thickness, followed by DL/T 5141-2001 and the last is ASCE No.79 (1993), which is correspondingly contrary to sort by allowable stress. Basically, ASCE No.79 (2012) defines lower safety coefficient for exposed penstock, which is identical with authoritative rules of pressure vessels in the U.S.A and EU. The safety of DL/T 5141-2001 has been proved via rich engineering experience and this specification is recommended for Chinese projects. Besides, ASCE No.79 (2012) is recommended.

Abstract: When more than one loads act on a structure,the combination of stochastic loads is generally considered in the design of the structure,Based on the theoretical derivation and numerical calculation analysis to the process of two common loads in Poisson square wave and Poisson impulse this paper presents the combination method of loads.i.e. The maximum intensity function of load combination is expressed by the cumulative distribution function in the limit state design. In addition,the result calculated during the limit state design is compared with those calculated by Turkstra and Monte Carlo methods and the analytical results show that the method proposed in this paper is feasible in the calculation of load combination.

Abstract: Offshore jacket platforms under complicated and changeful ocean environments are subjected to various stochastic actions such as actions of wave, current, wind, ice, earthquake and their combinations. This paper presented the approach to calibrate of the reliability of the offshore jacket platform, and suggested all kinds of associated load cases. The combination of loads were mainly investigated. As an example, the reliability of offshore jacket platform of QK18-1 in Bohai Bay was verified. The result shows that the reliability of the offshore jacket platform related to 25-year reference period is between 2.7 and 3.39, which is close to the conclusion of some existing researches. This method would be used more widely for the design of offshore jacket platforms.

Abstract: In structure design, for expressions with partial safety factors, partial safety factors and nominal value of loads are calculated based on the presupposition that the design reference period is 50 years. When the design reference period is not 50 years, it would cause unclear reliability of building structure by using expressions with partial safety factors following correlative codes yet. It may lead to hidden dangers in that way. In order to derive expressions with partial safety factors suitable for any design reference period, two useful methods are shown in this paper, modification of partial safety factors and modification of importance factor of structures. From results of analysis, we get the conclusions that it can assure the reliability index of the expression using the method of modification of partial safety factors, and the method of modification of importance factor of structures is very simple, but cannot assure the reliability index of the expression.

Abstract: Using large structure analysis software, the stress and displacement are calculated for Shuangji River rectangle aqueduct structure during construction and operation periods. The 19 different load combination cases are considered. The variation rule of mechanics behavior is obtained for concrete material during different load combination period. The simulation results show that the conventional method simulating prestress can lead to stress concentration in the point the force is acted on. It is a relatively good simulation method to add a steel plate to the area where the prestressed strands are acted on. In this way, the local stress concentration can be reduced. When use pseudo-static method for calculation of the seismic load, the load case considering the seismic load is a control load case. The Shuangji River aqueduct can meet the requirement of intensity and rigidity during construction and operation periods.

Abstract: The loads and load combination in ballastless track design was briefly introduced. The influence of cracks to the track slab flexural stiffness was studied. According to the mechanical characteristic of ballastless track, the structural coefficient was proposed and put to use in the amendment of different load effect on track slab. The prerequisite of the combination of moment and tensile force was discussed. Take the track slab in bi-block ballastless track for example, the reinforcement in segmental slab and continuous slab was calculated respectively. The results show the reinforcement ratio will substantially reduce when the structural coefficient was considered in the design. In general circumstance, the thermal force in continuous track slab will cause relatively large cracks, in which condition the bending effects cannot be added. The reinforcement in segmental track slab was controlled by train loads, while that in continuous track slab was controlled by thermal force.