Changes for page Seismic analysis

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edited by IwonaBudny
on 2018/09/06 14:36
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 ... ... @@ -109,15 +109,48 @@ 109 109 110 110 ---- 111 111 112 -= 2. Input data = 112 += Input data = 113 113 114 114 Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum. 115 115 116 116 (% id="HSub-paragraph-2" %) 117 -== Dynamic calculations == 117 +== Dynamic calculations and Mass definitions == 118 118 119 +(% style="text-align: justify;" %) 120 +[[image:1536237300428-654.png||height="27" width="66"]] To calculate the seismic effect it is necessary to know the vibration shapes and corresponding periods, except the static method (lateral force method: linear force distribution). Therefore a dynamic calculation should be done before performing seismic calculation, which gives sufficient vibration shapes of the structure. To perform the dynamic calculation, it is necessary to define mass distribution which can be defined in Load tab as concentrated mass or load case-mass conversion. 121 + 122 +According to EC8 3.2.4(2), mass distribution should be made in the following way: 123 + 124 +(% class="mark" %)ΣG,,k,,, ,,j,,"" + ""Σψ,,E, i,,Q,,k, i ,, 125 + 126 +where: 127 + 128 +* ψ,,E, i,, is the combination coefficient for variable action i (see EC8 4.2.4), it shall be computed from the following expression: 129 + 130 +(% class="mark" %)ψ,,E, i ,,= ϕ ψ^^2, ^^i 131 + 132 +The recommended values for ϕ are listed in EC8 Table 4.2. 133 + 134 +The above formula means that mass conversation is made from all dead load without any factor, also masses in gravity direction temporary loads with reduced value. 135 + 136 + 119 119 == Design spectrum == 120 120 139 +(% style="text-align: justify;" %) 140 +[[image:1536237268175-179.png||height="23" width="26"]] The program contains EC8 and NS3491-12 predefined design spectra or the user can define its own spectra if necessary. The vertical spectrum is necessary when the vertical affect taken into account. 141 + 142 + 143 +**EC8 design spectrum** 144 + 145 +The code gives the horizontal and vertical spectra and although the value of variables is prescribed, they can be modified if necessary. 146 + 147 +[[image:1536237376815-771.png||height="247" width="315"]] 148 + 149 +Data of horizontal design spectra: 150 + 151 + 152 + 153 + 121 121 ---- 122 122 123 123 = 3. Calculations parameters and calculations steps =