The Great Trigonometric Survey: Charting the Unseen Borders of the Indian Subcontinent

The Great Trigonometric Survey stands as a monumental project initiated with the objective of conducting a meticulous survey across the entire Indian subcontinent. Its inception dates back to 1802 when British army officer William Lambton undertook the project under the East India Company's auspices. Under the leadership of his successor, George Everest, the project was eventually completed, with Andrew Scott Waugh successfully concluding it in 1871.

Among the survey's numerous achievements were the delineation of British territories in India and the measurement of the heights of Himalayan giants like Everest, K2, and Kanchenjunga. The survey also had a significant scientific impact, being responsible for one of the first accurate measurements of a section of a meridian, contributing to the development of principles underlying isostasy.

Especially in the Himalayas, local surveyors employed for the task, often referred to as "pandits," played a crucial role. Among them were the notable brothers Nain Singh Rawat and Krishna Singh Rawat.

From its establishment in the 1600s to the beginning of the 19th century, the British East India Company expanded its dominion across the entire Indian subcontinent. With the acquisition of new territories, the Company appointed several explorers and cartographers, notably James Rennell, to provide maps and information, but the lack of accurate measurements was apparent. In 1800, following the victory over Tipu Sultan, William Lambton, a foot soldier with surveying experience, proposed a solution—a trigonometric survey using a series of triangles, initially through the newly acquired areas in Mysore and eventually spanning the entire subcontinent.

The Great Trigonometric Survey officially commenced on April 10, 1802, near Madras, with the measurement of a baseline. Lambton chose flat plains, with St. Thomas Mount to the north and Perumbauk Hill to the south. The baseline was 7.5 miles (12.1 km) long. Lieutenant Col. Colin Mackenzie was dispatched to find elevated points in the western mountains to connect the coastal points of Tellicherry and Cannanore. The selected high peaks were Mount Delly and Tadiandamol. The distance from coast to coast was 360 miles (580 km), and the survey line was completed in 1806.

Due to the challenging terrain, the surveyors did not triangulate the entire country but instead created a network of triangles running north-south and east-west, forming a "gridiron" due to the surveyed boundary lines. At times, surveying parties consisted of as many as 700 individuals.

The project, initially estimated to take about five years, extended for nearly 70 years due to the Indian Rebellion of 1857 and the eventual end of Company rule in India. Because of the surveyed land's border complexities, instead of creating a triangle, surveyors established "triangulation chains" from north-south and east-west. This approach facilitated the clear identification of most of the country's borders and contributed to the development of the principles of isostasy.

In 1875, recognizing the need for consolidation, a restructuring occurred, integrating the Great Trigonometrical, Topographical, and Revenue Surveys under the Survey of India. The significant impact of the Great Trigonometric Survey on geographical mapping and scientific progress in India is evident even today.

Key Instruments Used:

1. Baseline Measurement:

   • The baseline was measured using a chain in 1802, near Madras.
   • The baseline was 7.5 miles long.

2. Survey Towers:

   • Survey towers, like those used by George Everest, were established to support instruments.
   • Instruments were positioned to maintain accuracy.

3. Theodolites and Telescopes:

   • The survey employed theodolites for precise angle measurements.
   • A zenith sector telescope was used for measuring vertical angles.

4. Triangulation Chains:

   • Triangulation chains were formed, consisting of interconnected triangles.
   • These chains formed a "gridiron" pattern across the surveyed area.

5. Astronomical Observations:

   • Astronomical observations, especially using the Pole Star, were crucial for determining latitudes.
   • The survey aimed for accuracy, considering the potential impact of the apparent motion of the Pole Star.

The legacy of the Great Trigonometric Survey endures through the accurate maps, scientific advancements, and the foundation it provided for subsequent surveying endeavors in India. Its contribution to the fields of geodesy and cartography has left an indelible mark on the scientific history of the Indian subcontinent.

Method of RCC design

 Method of RCC design

Aim of Design

 As per IS 456-2000, the aim of design is the achievement of an acceptable probability that structures being designed will perform satisfactorily during their intended life. With an appropriate degree of safety, they should sustain all the loads and deformations of normal construction and use and have adequate durability and adequate resistance to the effects of misuse and fire. 

Method of RCC design
A reinforced concrete structure should be designed to satisfy the following criteria

i) Adequate safety, in items stiffness and durability 

ii) Reasonable economy. 

The following design methods are used for the design of RCC Structures. 

a) The working stress method (WSM)

 b) The ultimate load method (ULM) 

c) The limit state method (LSM) 

Working Stress Method (WSM) This method is based on linear elastic theory or the classical elastic theory. This method ensured adequate safety by suitably restricting the stress in the materials (i.e. concrete and steel) induced by the expected working leads on the structures. The assumption of linear elastic behaviour considered justifiable since the specified permissible stresses are kept well below the ultimate strength of the material. The ratio of yield stress of the steel reinforcement or the cube strength of the concrete to the corresponding permissible or working stress is usually called factor of safety. The WSM uses a factor of safety of about 3 with respect to the cube strength of concrete and a factor of safety of about 1.8 with respect to the yield strength of steel.

 Ultimate load method (ULM) The method is based on the ultimate strength of reinforced concrete at ultimate load is obtained by enhancing the service load by some factor called as load factor for giving a desired margin of safety .Hence the method is also referred to as the load factor method or the ultimate strength method. In the ULM, stress condition at the state of in pending collapse of the structure is analysed, thus using, the non-linear stress – strain curves of concrete and steel. The safely measure in the design is obtained by the use of proper load factor. The satisfactory strength performance at ultimate loads does not guarantee satisfactory strength performance at ultimate loads does not guarantee satisfactory serviceability performance at normal service loads. 

 Limit state method (LSM) Limit states are the acceptable limits for the safety and serviceability requirements of the structure before failure occurs. The design of structures by this method will thus ensure that they will not reach limit states and will not become unfit for the use for which they are intended. It is worth mentioning that structures will not just fail or collapse by violating (exceeding) the limit states. Failure, therefore, implies that clearly defined limit states of structural usefulness has been exceeded.

 Limit state are two types i) Limit state of collapse ii) Limit state of serviceability.

 Limit states of collapse-  The limit state of collapse of the structure or part of the structure could be assessed from rupture of one or more critical sections and from bucking due to elastic bending, shear, torsion and axial loads at every section shall not be less than the appropriate value at that section produced by the probable most unfavourable combination of loads on the structure using the appropriate factor of safely. 

Limit state of serviceability-   Limit state of serviceability deals with deflection and crocking of structures under service loads, durability under working environment during their anticipated exposure conditions during service, stability of structures as a whole, fire resistance etc.

References -IS 456 (2000): Plain and Reinforced Concrete - Code of Practice [CED 2: Cement and Concrete] July 2000 IS. 456 : 2000 (R••fflrmed2005) Indian Standard PLAIN AND REINFORCED CONCRETE ­ CODE OF PRACTICE (Fourth Revision) 

स्ट्रक्चरल इंजिनिअर्सचे महत्त्व

स्ट्रक्चरल इंजिनिअरिंग: सुरक्षित आणि स्थिर बांधकामाची गरज

स्ट्रक्चरल इंजिनिअर्स हे अभियंता क्षेत्रातील महत्त्वाचे घटक आहेत. इमारती, पूल, बोगदे आणि मोठ्या बांधकाम प्रकल्पांच्या उभारणीसाठी त्यांचे योगदान अत्यंत महत्त्वाचे आहे. आधुनिक युगात, स्ट्रक्चरल इंजिनिअर्सची भूमिका केवळ मजबूती व सुरक्षितता पुरवणे इतकीच मर्यादित नाही, तर त्यांनी नवनवीन तंत्रज्ञानाचा वापर करून, पर्यावरणस्नेही व कार्यक्षम संरचना विकसित करण्याकडे लक्ष केंद्रित केले आहे.

स्ट्रक्चरल इंजिनिअर्सचे महत्त्व

• सुरक्षा आणि स्थिरता: इमारती, पूल किंवा इतर संरचना भूकंप, वादळ आणि नैसर्गिक आपत्तींना तोंड देऊ शकतील अशी सुनिश्चित करणे.

• नवनवीन डिझाईन्स: संरचनांची सौंदर्यपूर्णता आणि कार्यक्षमता वाढवण्यासाठी आधुनिक डिझाईन्सचा अवलंब करणे.

• इको-फ्रेंडली तंत्रज्ञान: पर्यावरणपूरक साहित्य आणि ऊर्जेची बचत करणाऱ्या डिझाईन्स वापरणे.

• आर्थिक नियोजन: मजबूत व सुरक्षित संरचना कमी खर्चात कशा उभारता येतील याचे नियोजन करणे.

बांधकामांमधील समस्या आणि स्ट्रक्चरल इंजिनिअर्सची भूमिका

आजच्या काळात, अनेक ठिकाणी स्ट्रक्चरल इंजिनिअर्सशिवाय इमारती उभारल्या जातात, ज्यामुळे धोके वाढतात.

• पाया कमजोर ठेवणे: अनेक कंत्राटदार आणि मालक मातीचे परीक्षण न करता बांधकाम करतात, ज्यामुळे भविष्यात इमारती कोसळण्याचा धोका वाढतो.

• अयोग्य साहित्याचा वापर: गुणवत्तेची तडजोड केल्याने संरचना कमकुवत होतात.

• अनियोजित विस्तार: मंजूर केलेल्या प्लॅनपेक्षा जास्त मजले जोडल्याने इमारतींची स्थिरता कमी होते.

शहरीकरण आणि स्ट्रक्चरल इंजिनिअर्सचे महत्त्व

शहरीकरणामुळे जमिनीच्या किंमती वाढल्या आहेत, त्यामुळे बांधकाम व्यावसायिक उंच इमारती बांधण्यावर भर देतात. परंतु योग्य अभियांत्रिकीशिवाय या इमारती सुरक्षित ठरत नाहीत. स्ट्रक्चरल इंजिनिअर्सच्या मार्गदर्शनाखाली बांधलेल्या इमारती अधिक सुरक्षित आणि टिकाऊ असतात.

स्ट्रक्चरल इंजिनिअर्सच्या भूमिका विविध क्षेत्रांमध्ये

• उच्च इमारती आणि गगनचुंबी टोरे: उंच इमारतींच्या डिझाईन आणि संरचनेत त्यांचे योगदान महत्त्वाचे असते.

• सेतू आणि पूल बांधणी: ट्रॅफिक लोड आणि नैसर्गिक आपत्तींच्या दृष्टीने पूल आणि सेतूंचे संरचनात्मक नियोजन.

• सैन्य आणि औद्योगिक संरचना: सैन्य तळ, अणुऊर्जा केंद्रे, आणि मोठ्या उद्योगांसाठी विशेष संरचना डिझाईन करणे.

• पर्यावरणपूरक आणि आपत्ती-निवारक संरचना: भूकंपरोधक आणि हरित इमारतींची रचना करणे.

भविष्यातील संधी आणि सुधारणा

• नवीन तंत्रज्ञानाचा अवलंब: आर्टिफिशियल इंटेलिजन्स, बिग डेटा आणि BIM (Building Information Modeling) चा वापर.

• स्मार्ट सिटी आणि इन्फ्रास्ट्रक्चर: आधुनिक शहरांमध्ये तंत्रज्ञानाधारित संरचना विकसित करणे.

• सतत संशोधन आणि नावीन्य: नवीन बांधकाम साहित्य आणि तंत्रज्ञान विकसित करणे.

स्ट्रक्चरल इंजिनिअर्सच्या मदतीनेच बांधकाम अधिक सुरक्षित आणि कार्यक्षम होऊ शकते. त्यामुळे, शहरीकरणाच्या वेगवान वाढीमध्ये आणि भविष्यातील बांधकाम क्षेत्रात त्यांची भूमिका अत्यंत महत्त्वाची ठरणार आहे.

अपेक्षित बदल

• बांधकामात स्ट्रक्चरल इंजिनिअर्सचा समावेश सक्तीचा करावा.

• सरकारी नियमानुसार सर्व संरचनांची तपासणी व्हावी.

• संरचनांच्या गुणवत्तेवर तडजोड टाळावी.

स्ट्रक्चरल इंजिनिअरिंग ही केवळ एक नोकरी नसून, ती समाजाच्या सुरक्षिततेशी निगडीत जबाबदारी आहे. योग्य नियोजन, काटेकोर निरीक्षण, आणि प्रगत तंत्रज्ञानाचा वापर केल्यास बांधकाम क्षेत्र अधिक प्रगत आणि टिकाऊ बनू शकते.