# Реферат: Подбор допустимой нагрузки для балки

Задача 5.

Для заданної схеми балки (мал.іа)педібрати допустиме навантаження [q],         якщо [σ]=100 МПа.

Розв’язок.

1.<span Times New Roman"">     Визначаємо реакції опор балки(мал.іа):

<img src="/cache/referats/4573/image002.gif" v:shapes="_x0000_i1025">

<img src="/cache/referats/4573/image004.gif" v:shapes="_x0000_i1026">

<img src="/cache/referats/4573/image006.gif" v:shapes="_x0000_i1027">

<img src="/cache/referats/4573/image008.gif" v:shapes="_x0000_i1028">

2.<span Times New Roman"">

Будуємо епюри Q(мал. б) і М (мал. в)

а=2м          р

<img src="/cache/referats/4573/image009.gif" v:shapes="_x0000_s1083 _x0000_s1084 _x0000_s1085 _x0000_s1086 _x0000_s1087"><img src="/cache/referats/4573/image010.gif" v:shapes="_x0000_s1078 _x0000_s1079 _x0000_s1080 _x0000_s1081 _x0000_s1082"><img src="/cache/referats/4573/image012.gif" v:shapes="_x0000_s1077"><img src="/cache/referats/4573/image013.gif" v:shapes="_x0000_s1068 _x0000_s1066 _x0000_s1064 _x0000_s1065 _x0000_s1067"><img src="/cache/referats/4573/image014.gif" v:shapes="_x0000_s1061"><img src="/cache/referats/4573/image015.gif" v:shapes="_x0000_s1060"><img src="/cache/referats/4573/image017.gif" v:shapes="_x0000_s1059 _x0000_s1056 _x0000_s1057 _x0000_s1058"><img src="/cache/referats/4573/image018.gif" v:shapes="_x0000_s1054 _x0000_s1050 _x0000_s1053 _x0000_s1052"><img src="/cache/referats/4573/image019.gif" v:shapes="_x0000_s1046 _x0000_s1047 _x0000_s1048 _x0000_s1049"><img src="/cache/referats/4573/image020.gif" v:shapes="_x0000_s1045 _x0000_s1042 _x0000_s1043 _x0000_s1044"><img src="/cache/referats/4573/image021.gif" v:shapes="_x0000_s1041"><img src="/cache/referats/4573/image021.gif" v:shapes="_x0000_s1040"><img src="/cache/referats/4573/image022.gif" v:shapes="_x0000_s1039 _x0000_s1026 _x0000_s1030 _x0000_s1031 _x0000_s1032 _x0000_s1033 _x0000_s1034 _x0000_s1035 _x0000_s1036 _x0000_s1037 _x0000_s1038"><img src="/cache/referats/4573/image023.gif" v:shapes="_x0000_s1029"><img src="/cache/referats/4573/image024.gif" v:shapes="_x0000_s1028"><img src="/cache/referats/4573/image025.gif" v:shapes="_x0000_s1089">                                                                                 RA=0                           RB=2qa

M=2qa2           M=2qa2

q

<img src="/cache/referats/4573/image026.gif" v:shapes="_x0000_s1091">                Мал. а).

<img src="/cache/referats/4573/image027.gif" v:shapes="_x0000_s1027">                                                                          A                                          B

<img src="/cache/referats/4573/image028.gif" v:shapes="_x0000_s1051">

a                       2a

<img src="/cache/referats/4573/image029.gif" v:shapes="_x0000_s1062"><img src="/cache/referats/4573/image030.gif" v:shapes="_x0000_s1063">             Мал. б).                                                                                                       Епюра Q

0                  0

2qa

<img src="/cache/referats/4573/image031.gif" v:shapes="_x0000_s1125"><img src="/cache/referats/4573/image032.gif" v:shapes="_x0000_s1124">                                                                       2qa2

qa2

Мал.в).                                                                                                         ЕпюраМ

0

3.<span Times New Roman"">

Небезпечний переріз в якому Ммах=2qa2

4.<span Times New Roman"">

Визначаємо геометричніхарактеристики перерізу (мал. г)

Епюра σ

<img src="/cache/referats/4573/image033.gif" v:shapes="_x0000_s1118 _x0000_s1114 _x0000_s1115 _x0000_s1116 _x0000_s1117"><img src="/cache/referats/4573/image034.gif" v:shapes="_x0000_s1113 _x0000_s1111 _x0000_s1112"><img src="/cache/referats/4573/image036.gif" v:shapes="_x0000_s1110"><img src="/cache/referats/4573/image037.gif" v:shapes="_x0000_s1106"><img src="/cache/referats/4573/image038.gif" v:shapes="_x0000_s1105"><img src="/cache/referats/4573/image039.gif" v:shapes="_x0000_s1104"><img src="/cache/referats/4573/image040.gif" v:shapes="_x0000_s1103 _x0000_s1101 _x0000_s1097 _x0000_s1098 _x0000_s1099 _x0000_s1102">                                                 Y

50х50х5

C                н.л.  Z

Мал.г).

а).  осьовий момент перерізу           JZ=JZ└∙2=11,2∙2=22,4 (см4)

б).  Осьовий момент опору

<img src="/cache/referats/4573/image042.gif" v:shapes="_x0000_i1029">

5.<span Times New Roman"">

Записуємо умову міцності балкита знаходимо допустиме навантаження

<img src="/cache/referats/4573/image044.gif" v:shapes="_x0000_i1030">

<img src="/cache/referats/4573/image046.gif" v:shapes="_x0000_i1031">

[q]=0,24кН/м

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