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1.
The World Trade Center collapse has brought attention to progressive collapse of tall buildings and the study of possible countermeasures. From the viewpoint of energy transfer, this analysis explains why the collapse could not stop by itself once began. By introducing a design parameter called collapse stability index that controls design against progressive collapse, it is found that conventional design of a tall building usually leads to an inherently unstable structure in the event of a progressive collapse. In a subsequent feasibility study in this paper, a heavy-duty metal-based honeycomb energy absorbing structure is proposed. Using a finite element analysis, it is demonstrated that the structure is capable of absorbing potential energy released in a tall building collapse. The added energy absorbing devices will only occupy a small percentage of the total floor space. By properly designing and installing such devices, a progressive collapse, should it happen in a tall building, may be arrested within a few floors, and hence, the building is inherently stable to the progressive collapse. The theory is also elaborated with the example of the World Trade Center collapse.  相似文献
2.
Centrifuge Modeling of Ship Impact Loads on Bridge Pile Foundations   总被引:1,自引:0,他引:1  
Bridges that cross navigable waterways may be affected by accidental ship impacts. To better characterize ship impact loads on bridge pier structures, a comprehensive centrifuge model test program involving 48 ship impact tests was performed on a 2×3 pile group and a 3×3 pile group founded in saturated silty sand. These model tests simulated groups of 2-m-diameter by 31.5-m-long pipe piles. The effects of three factors related to the ship (tonnage, speed, and bow structure) and two factors related to the bridge pier structure (superstructure mass and pile-group size) were investigated through these impact tests. The characteristics of the ship impact load were identified and the mechanism of the ship-bridge collision was analyzed. The test results show that the ship impact load was highly dependent on the ship bow structure and the ship impact speed. The test results were compared with other published data and the AASHTO loads. An empirical equation was suggested to relate the ship impact load to the five influencing factors.  相似文献
3.
针对济钢炉外精炼系统-VD自动测温取样枪装置的液压系统调试过程中存在的"有杆腔工作顺利,无杆腔工作卡死"问题,进行系统原理分析,认为液控单向阀阀芯阻力大是主要原因。通过重新选型,避免了设备存在的隐患。  相似文献
4.
张维国 《山东冶金》2000,21(4):39-41
对JK型提升机卷筒筒壳损伤原因进行分析,发现焊缝不规则造成应力集中、冲击载体作用频繁、连接板边缘处应力集中、补木无法保护筒壳、筒壳受力变形是筒壳产生裂纹的主要原因。为此,对支撑板重新设计,达到修复目的。  相似文献
5.
A primary means of demonstrating the feasibility and effectiveness of fiber-reinforced polymer (FRP) composite bridge materials is via in situ bridge load testing. For this study, the prescribed or assumed design factors for each of the study bridges were compared to those exhibited by the performance of the bridge. Specifically, the wheel load distribution factors and impact factors as defined by AASHTO were considered in order to assess the load transfer and distribution in structures utilizing FRP panels. The in situ testing configurations for the study bridges are outlined, including the truck and instrumentation placement to obtain the desired information. Furthermore, comparisons were drawn between the design values for deflection and those experienced by the structures during testing. It was found that although the deflections exhibited by the bridges were well within the design limits, further research is needed to be able to prescribe bridge design factors for FRP panels.  相似文献
6.
The paper presents an experimental study of the actual dynamic effects for a preselected typical highway bridge. Knowledge of the dynamic impact factors is important for accurate determination of the ultimate load capacity and performance assessment of constructed bridges. Static and dynamic field tests were performed on a two-lane concrete highway bridge built in 1999 on U.S. 90 in northwest Florida. During the tests, one or two fully loaded trucks crossed over the bridge, which was instrumented with strain gauges, accelerometers, and displacement transducers. A wooden plank was placed across the lanes for some runs to trigger extensive dynamic vibration and to simulate poor road surface conditions. Data collected from the tests were used for comprehensive assessment of the bridge under dynamic loading. Impact factors obtained from the tests with higher speeds were found larger than corresponding values recommended by bridge codes. Analysis revealed that stiff vehicle suspension, road surface imperfection, and “bouncing” of the truck loading contributed to the high impact factors. Experimental data were also used for validation of the finite-element models developed for the vehicle–bridge system.  相似文献
7.
In this paper, the higher-order shear deformation theory is used to study the response of graphite/epoxy laminated composite nonprismatic folded plates subjected to impact loads. A finite-element model of the theory is also developed. The modified Hertzian contact law incorporated within the Newton–Raphson method is used to calculate the contact force between the impactor and the laminated plate. For time integration, the Newmark direct integration was adopted. Numerical results are presented to demonstrate the effects of span-to-thickness ratio, fiber angle, stacking sequence, and crank angle on the response of laminated plate subjected to impact. It is demonstrated that the results obtained from the present investigation compare well with those reported in the open literature.  相似文献
8.
Laminated architectural glass has proven to be well suited for use in glazing systems that must resist wind-borne debris impacts. When the inner glass ply in a laminated window unit remains unbroken after wind-borne debris impacts on the outer glass ply, the integrity of the building envelope is preserved. A mechanics-based analytical model is developed to predict the cumulative probability of inner glass ply breakage in laminated architectural glass subjected to simulated wind-borne debris impacts on the outer glass ply. A nonlinear dynamic finite-element analysis is employed to compute stresses in each layer of the laminate due to impact. Based on the cumulative damage theory, the two-parameter Weibull distribution is used to characterize the cumulative probability of inner glass ply breakage. The analytical predictive model is calibrated using available experimental data on material parameters. Cumulative probabilities of inner glass ply breakage predicted by the analytical model are in agreement with the corresponding experimental data.  相似文献
9.
All long‐duration spacecraft are susceptible to high‐speed impacts by meteoroids and pieces of orbiting space debris. Damage to critical spacecraft systems caused by such impacts can lead to spacecraft failure and loss of life. In order to develop adequate protection against penetration for crew compartments and other critical spacecraft systems, an aerospace design engineer must possess a full understanding of the penetration mechanics involved in the hypervelocity impact loading of a variety of structural components. This paper describes the results of an experimental investigation of the penetration phenomena associated with oblique hypervelocity projectile impact of aluminum dual‐wall structures. Equations that quantitatively describe these phenomena are obtained through a regression of hypervelocity impact test data. These equations characterize observed penetration phenomena as functions of the geometric and material properties of the impacted structure and the diameter, obliquity, and velocity of the impacting projectile. A review of the test data shows that oblique hypervelocity impact penetration phenomena are strongly dependent on impact obliquity and therefore can differ significantly from those associated with normal high‐speed impacts. It is concluded that the possibility of non‐normal impacts and their effects on structural integrity must be considered in the design of any structure that is to be exposed to the hazardous meteoroid and space debris environment.  相似文献
10.
济钢中板厂由于料坯增大对上料台冲击载荷增加,使上料台损坏频繁。通过采用由12个M30铰制孔螺栓连接定位的装配形式、主轴由45^#钢改为42CrMo等措施,延长了上料升降系统的使用寿命,彻底消除了设备隐患,降低了设备停机时间和对设备的维护强度,节约了维修费用。  相似文献
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