CIVIL YAAR

Let Us Know   Member which are subjected to direct tension are called tension member ( or tie - member ). Tension members are used in fabrication of steel roof trusses and bridge trusses etc . When tension members are subjected to direct tension, the stress distribution on the steel section is uniform but when the loads are eccentric, then additional moments are developed in the member . Hence, the stress distribution is non - uniform in eccentrically loaded tie members . Tension member are selected depending upon the magnitude and type of stress carried by them . Various members used as tie members are : single angle section, double angle sections, roads, flats, eye bars, T - sections and built up section etc . Net sectional area of a tension members plays a vital role in the design . Net sectional area may be defined as the gross area of the members less deduction for holes .   Note : - Holes ( made for rivets ) reduces the resisting capacity of the members at the section .

                                                                                           Click here to get these notes here ►   Permissible (Allowable) stresses in tension.              The permissible stress in axial tension  on the net effective area of the section shall not exceed 0.6 times the minimum yield stress of steel . The permissible stress in axial tension for steel conforming to IS: 226-1975 are given in below:-                          Table 1.  Allowable stresses in Axial Tension.                             (For steel confirming to IS: 226-1975) S. No. Form of rolled steel section of Tension Member Diameter/Thickness Value of N/mm2       1. Plates, flats, angles, beams, channels, and tee-section Upto and including 20mm Above 20mm and ≤ 40mm > 40mm 150 144 138       2. Bars (square, round, and hexagonal ) Upto and including 20mm    > 20 mm 150 144   ►   Strength (Load carrying capacity) of a tension member.                The tensile strength (or load carrying ca

tension member is defined as a structural member sublected to tensile force. Tension member is also called as tie. The term tie is  commonly used for tension member in the roof truss. When a tension member is subjected to direct tension, the stress distribution on the section is uniform. But additional bending moments are induced in the member when the load on tension member is eccentric (member is subjected to combined stress i.e direct tension and bending). *Types of Tension Member:- Single rolled steel structural member and plates. Built-up-member. Rods and bars.                          1. S ingle rolled steel structural member and plates.                                     The single structural shapes like angle and tee-sectional are normally used as tension members. The angle sections are considerably more rigid then the rods and bars. Single angle sections are widely used as tension members in light roof trusses, bracing members(stiffners) in plate girders etc.         2.   Bui

ताकबंदी (shoring ):-                                   संरचनाओं की दीवारों व स्तम्भो की नीँव के लिए भूमि को गहरा खोदना पड़ता हैं नीव की गहराई के अनुसार यह गहराई एक मीटर से कई मीटर तक हो सकती हैं।  सीवर प्रणाली में यह गहराई 3 -10 मीटर  तक गहरी चली जाती हैं।                          द्रढ़  मृदा (Hard Soil) में यह गहराई स्थिर रह सकती हैं परन्तु नर्म व ढीली  मृदा में खाई की पार्श्व फलक के सीधी खड़ी  नहीं रह सकती और ढह कर खाई को पाट देती हैं।  जिसके परिणाम स्वरुप निर्माण कार्य रुक जाता हैं और कभी कभी गंभीर दुर्घटनाएं भी हो जातें हैं।  अतः सामान्य तथा ढीली मृदा  में  1.5    (2 मीटर  PWD के अनुसार )   मीटर की गहराई से निचे जाने पर खाइयों की तख्ताबंदी करना आवश्यक हैं।  कठोर तथा ढीली मृदा  में 2 से 2.5 मीटर से निचे, सुरक्षा की दृष्टि से तख्ताबन्दी अवश्य कर  देनी  चाहिए।  ताकबंदी एक इमारत, पोत, संरचना या तट के साथ खाई को सहारा देने की प्रक्रिया है (ढलान) जब ढहने का खतरा होता है या मरम्मत या परिवर्तन के दौरान। ताकबंदी तट से आता है, एक लकड़ी या धातु का प्रोप। ताकबंदी ऊर्ध्वाधर, कोण, या क्षैतिज हो सकत