A simple formula for calculating internal force
F internal force = f external force * (M internal force) / (M total)
simplified from actual model to mechanical model; Reasonable mechanical calculation methods and mechanical assumptions are selected in the mechanical model; Under the assumption of mechanics, through the theory of mechanics, combined with the particularity of materials, the reasonable material parameters are taken into the mechanical formula, and the internal force conforming to the characteristics of materials is obtained
load is a process of graal transfer from top to bottom. In this process, various theories and methods are used to calculate internal forces according to different structural forms of buildings
extended data:
at the intersection of the secondary beam and the main beam, cracks occur at the top of the secondary beam under the action of negative bending moment, and the concentrated load can only be transmitted to the abdomen of the main beam through the compression area of the secondary beam. This effect is in the range of 0.5-0.6 times of the beam height on both sides of the concentrated load acting point, which can cause diagonal cracks of main tensile failure. In order to prevent this kind of damage, additional transverse reinforcement is set on both sides of the main beam, and the concentrated load at the lower part of the beam or within the height range of the beam section should be borne by the additional transverse reinforcement (hanging reinforcement and stirrup). The additional transverse reinforcement shall be arranged within the length of S = 2h1 + 3B
the structure with horizontal thrust is called arch structure, which is divided into statically determinate arch (three hinged arch) and statically indeterminate arch (two hinged arch and no hinged arch)
taking the three hinged arch as an example, under the same span and vertical load, the arch has horizontal thrust, the beam does not, and the three hinged rigid frame (with the characteristics of arch) has horizontal support reaction (thrust)
take a look at the chapter three hinge arches.
2. Reasonable mechanical calculation methods and mechanical assumptions should be selected in the mechanical model
3. Under the assumption of mechanics, through the theory of mechanics, combined with the particularity of materials, the reasonable material parameters are taken into the mechanical formula, and the internal force conforming to the characteristics of materials is obtained.
The assumption of folded plate calculation: the transverse strain and shear strain in the plate plane are not considered, but only the axial force and shear force in the plate plane, as well as the transverse bending moment and shear force of the plate are considered. Each slab is regarded as a beam with rectangular section and analyzed according to the bending theory along the span direction. In the calculation, the distributed load is converted into the line load acting on the folding joint according to the equivalent method, and all the internal forces and displacements of the folding plate are calculated according to the analysis method of thin-walled space structure mechanics. The folded plate structure can also be calculated by the finite element method. The longitudinal and transverse strength and crack resistance of V-shaped folded plate are calculated according to rectangular section, with longitudinal and transverse reinforcement. The connection structure of folded plate should be strengthened properly. For multi wave continuous trough and V-shaped folded plates, horizontal braces or other measures should be set within 1-2 wave widths near the boundary to increase horizontal stiffness and resist wind load and horizontal seismic load (see seismic action)
MD = 4 * 4 * 4 / 8 = 8kn-m (QL2 / 8), one end is fixed, one end is hinged, symmetrical structure, symmetrical load, antisymmetric internal force on the symmetry axis is 0, which side of BD rod is asymmetric in tension, so MDA = MDC
antisymmetric, both sides are loaded 4kn / m, left side is down, right side is up
overall ∑ x = 0, RBX = 0,
lock D point, one end is fixed One end hinged
MDA = MDC = 8kn-m
d node bending moment distribution method, three members are distributed at one time, the distribution coefficient is 0.3, 0.3, 0.4 (EI is the same, 4I, 3I, 3I)
unbalanced moment MDA + MDC = 16kn-m
the section method is applicable to two cases: one is that all the members are parallel except one of them
the second is the intersection point of the cut rod except one
the node rule is applicable to the case that there are only two unknown forces at the node. And for any simple truss, the internal force of any member can be calculated by the node method.
the next step is to turn the problem into a cantilever beam acted by three external forces
because you have not provided other known conditions, you can not directly calculate them for you now.