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51.
在丹阳北二环大桥斜拉索施工中,总结多座跨径小于150m的斜拉桥斜拉索施工技术,针对此前大型斜拉索施工技术进行了优化改进,特别是斜拉索的展索、挂索及张拉技术。 相似文献
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通过对我国现有铁路货车制动系统进行分析,并与国外先进制动系统对比,得出我国货车制动系统存在检修周期短、关键零部件可靠性不高的问题。同时,根据目前存在的问题,简要论述提高我国货车制动系统可靠性的方法。 相似文献
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A simple formulation for predicting the ultimate strength of ships 总被引:11,自引:0,他引:11
The aim of this study is to derive a simple analytical formula for predicting the ultimate collapse strength of a single- and double-hull ship under a vertical bending moment, and also to characterize the accuracy and applicability for earlier approximate formulations. It is known that a ship hull will reach the overall collapse state if both collapse of the compression flange and yielding of the tension flange occur. Side shells in the vicinity of the compression and the tension flanges will often fail also, but the material around the final neutral axis will remain in the elastic state. Based on this observation, a credible distribution of longitudinal stresses around the hull section at the overall collapse state is assumed, and an explicit analytical equation for calculating the hull ultimate strength is obtained. A comparison between the derived formula and existing expressions is made for largescale box girder models, a one-third-scale frigate hull model, and full-scale ship hulls.List of symbols
A
B
total sectional area of outer bottom
-
A
B
total sectional area of inner bottom
-
A
D
total sectional area of deck
-
A
S
half-sectional area of all sides (including longitudinal bulkheads and inner sides)
-
a
s
sectional area of a longitudinal stiffener with effective plating
-
b
breadth of plate between longitudinal stiffeners
-
D
hull depth
-
D
B
height of double bottom
-
E
Young's modulus
-
g
neutral axis position above the base line in the sagging condition or below the deck in the hogging condition
-
H
depth of hull section in linear elastic state
-
I
s
moment of inertia of a longitudinal stiffener with effective plating
-
l
length of a longitudinal stiffener between transverse beams
-
M
E
elastic bending moment
-
M
p
fully plastic bending moment of hull section
-
M
u
ultimate bending moment capacity of hull section
-
M
uh
,M
us
ultimate bending moment in hogging or sagging conditions
-
r
radius of gyration of a longitudinal stiffener with effective plating [=(I
s
/a
s
)1/2]
-
t
plate thickness
-
Z
elastic section modulus at the compression flange
-
Z
B
,Z
D
elastic section modulus at bottom or deck
-
slenderness ratio of plate between stiffeners [= (b/t)(y/E)1/2]
-
slenderness ratio of a longitudinal stiffener with effective plating [=(l/r)(y/E)1/2]
-
y
yield strength of the material
-
yB
,
yB
,
yD
yield strength of outer bottom, inner bottom
-
yS
deck, or side
-
u
ultimate buckling strength of the compression flange
-
uB
,
uB
,
uD
ultimate buckling strength of outer bottom
-
uS
inner bottom, deck, or side 相似文献
57.
K. J. Spyrou 《Journal of Marine Science and Technology》1995,1(1):24-36
The behavior of a ship encountering large regular waves from astern at low frequency is the object of investigation, with a parallel study of surf-riding and periodic motion paterns. First, the theoretical analysis of surf-riding is extended from purely following to quartering seas. Steady-state continuation is used to identify all possible surf-riding states for one wavelength. Examination of stability indicates the existence of stable and unstable states and predicts a new type of oscillatory surf-riding. Global analysis is also applied to determine the areas of state space which lead to surf-riding for a given ship and wave conditions. In the case of overtaking waves, the large rudder-yaw-surge oscillations of the vessel are examined, showing the mechanism and conditions responsible for loss of controllability at certain vessel headings.List of symbols
c
wave celerity (m/s)
-
C(p)
roll damping moment (Ntm)
-
g
acceleration of gravity (m/s2)
-
GM
metacentric height (m)
-
H
wave height (m)
-
I
x
,I
z
roll and yaw ship moments of inertia (kg m2)
-
k
wave number (m–1)
-
K
H
,K
W
,K
R
hull reaction, wave, rudder, and propeller
-
K
p
forces in the roll direction (Ntm)
-
m
ship mass (kg)
-
n
propeller rate of rotation (rpm)
-
N
H
,N
W
,N
R
hull reaction, wave, rudder, and propeller
-
N
P
moments in the yaw direction (Ntm)
-
p
roll angular velocity (rad/s)
-
r
rate-of-turn (rad/s)
-
R(,x)
restoring moment (Ntm)
-
Res(u)
ship resistance (Nt)
-
t
time (s)
-
u
surge velocity (m/s)
-
U
vessel speed (m/s)
-
v
sway velocity (m/s)
-
W
ship weight (Nt)
-
x
longitudinal position of the ship measured from the wave system (m)
-
x
G
,z
G
longitudinal and vertical center of gravity (m)
-
x
S
longitudinal position of a ship section (S), in the ship-fixed system (m)
-
X
H
,X
W
,X
R
hull reaction, wave, rudder, and propeller
-
X
P
forces in the surge direction (Nt)
-
y
transverse position of the ship, measured from the wave system (m)
-
Y
H
,Y
W
,Y
R
hull reaction, wave, rudder, and propeller
-
Y
p
forces in the sway direction (Nt)
-
z
Y
vertical position of the point of action of the lateral reaction force during turn (m)
-
z
W
vertical position of the point of action of the lateral wave force (m)
Greek symbols
angle of drift (rad)
-
rudder angle (rad)
-
wavelength (m)
-
position of the ship in the earth-fixed system (m)
-
water density (kg/m3)
-
angle of heel (rad)
-
heading angle (rad)
-
e
frequency of encounter (rad/s)
Hydrodynamic coefficients
K
roll added mass
-
N
v
,N
r
yaw acceleration coefficients
-
N
v
N
r
N
rr
N
rrv
,N
vvr
yaw velocity coefficients K. Spyrou: Ship behavior in quartering waves
-
X
u
surge acceleration coefficient
-
X
u
X
vr
surge velocity coefficients
-
Y
v
,Y
r
sway acceleration coefficients
-
Y
v
,Y
r
,Y
vv
,Y
rr
,Y
vr
sway velocity coefficients
European Union-nominated Fellow of the Science and Technology Agency of Japan, Visiting Researcher, National Research Institute of Fisheries Engineering of Japan 相似文献
58.
遗传算法在五连杆悬架优化中的应用 总被引:5,自引:0,他引:5
针对五连杆悬架的特点,运用多体系统动力学的理论建立了悬架的运动学分析模型,基于遗传算法开发了优化器的核心单元,并解决了它们之间的通讯和协调问题以实现在车轮上下跳动过程中车轮外倾角的运动学特性变化量与目标值之间的偏差最小作为优化设计的目标,说明了遗传算法在五连杆悬架优化中的应用。应用这种优化体系对某型轿车五连杆悬架进行了实例优化分析。 相似文献
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