Interactive Design of Steel Roof System on Microcomputers

Interactive Design of Steel Roof System on Microcomputers.

ABSTRACT

FORTRAN programs are presented for the design of a Howe  steel  roof  system in accordance with BS5950 (1985) at a constant reliability level. The concept of the design was built upon the First-Order Reliability  Method  (FORM) and System Reliability (SYSREL).

The reliability indices of components making the truss system were observed  to vary as the dead/live load ratio increases. The overall safety index of the system is lower than the safety indices of the individual  components  and  joints.

The reliability program developed iteratively selects optimum sectional properties which offer a target reliability level when inherent uncertainties in the design variables are systematically considered.

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TABLE OF CONTENTS

Certification     i

Dedication    ii

Acknowledgement          iii

Abstract    v

Contents           vi

List of tables   x

List of figures         xii

Notations      xiii

Chapter  1 INTRODUCTION

• STRUCTURAL STEEL 1
• ROOF SYSTEMS 1
• RELIABILITY APPROACH 3
• PROBLEM STATEMENT AND JUSTIFICATION 4
• RESEARCH AIM AND OBJECTIVE 4
• SCOPE OF RESEARCH 5
• METHODOLOGY 5

Chapter  2 LITERATURE REVIEW

• STRUCTURAL SYSTEM 6
• SYSTEM RELIABILITY 7
• THE BASIC RELIABILITY PROBLEM 8
• RELIABILITY ANALYSIS 10
• FORMULATION OF RELIABILITY-BASED DESIGN 11

Chapter  3 FUNDAMENTALS OF FORM AND SYSREL

• RELIABILITY ASSESSMENT 14
• PROBABILITY THEORY 15
  • Variance and Standard Deviation 15
  • Co-variance and Correlation 15
• THE TRANSFORMATION OR FIRST-ORDER RELIABILITY METHOD 16
  • Simple Transformation 16
  • Transformation of non-normal basic variables 17
• DETERMINATION OF RELIABILITY INDEX 17
• INTRODUCTION TO FIRST-ORDER RELIABILITY METHOD 20
• COMPONENTAL FIRST-ORDER PROBABILITY ESTIMATES 21
• INTRODUCTION TO SYSREL 22
  • Theoretical Background 22
  • Minimal cut-set representation 23
  • Formation of minimal cut-set 23

Chapter  4 ANALYSIS, DESIGN AND RELIABILITY ESTIMATES

• LOAD, ANALYSIS AND MEMBER FORCES 25
• DESIGN OF TRUSS MEMBERS AND JOINTS 31
• RELIABILITY ESTIMATE 33
  • Component Reliability Analysis 33
    • Limit State Equation 34
    • Statistical characters of relevant design parameters 37
    • Componental Reliability Analysis 39
  • System Reliability Analysis 43
    • Fault-tree Analysis 43
    • Input Data to CUTALG 43
    • Input Data to SYSREL 48
    • SYSREL Analysis Result 48
  • TARGET SAFETY INDEX 49

Chapter  5 SAFETY DESIGN PROGRAM

• GENERAL 50
• PROGRAM FLOW CHART 51
• DESIGN CRITERION 51
• PROGRAM DESCRIPTION 53
  • FORM5 53
  • SYSREL/CUTALG 53
• PROGRAM STRUCTURE 54
  • PROGRAM RELOTOP 54
  • PROGRAM RELOBOP 55
  • PROGRAM RELOSTRUT 55
  • PROGRAM RELOWELD 55
• PROGRAM STATEMENT 55
• PROGRAM RESULT 55
• COMPARISON OF RESULTS AND DISCUSSION 56

Chapter  6 CONCLUSION  AND RECOMMENDATION

• CONCLUSION 62
• RECOMMENDATION 62

REFERENCES      64

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INTRODUCTION

1.1 STRUCTURAL STEEL

Structural steel products are manufactured to conform to  BS4360 (1990): Weldable structural steels. Steel is composed of about 98% Iron with the main alloying elements; carbon, silicon and manganese.

It is produced in strength grades 43, 50 and 55. The  important  properties are strength, ductility, impact resistance and weldability. The most common members used in structures are single and  double  angles, tees, channels and structural hollow sections. I, H, Compound and built–up members are used in heavy trusses, certainly hot – rolled sections.

1.2 ROOF SYSTEMS

 Roof systems are structures comprising several member components or elements connected by joints to form a series of triangles, commonly known as ‘ trusses’.

In  other words, trusses are framed elements resisting in-plane loading  by axial forces either in tension or compression in the individual members. The elements are typically assumed to be joined at their intersections with pinned connections so that all loads and reactions occur only at these joints.

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REFERENCES

ANG, A.H–S, (1974), Risk Reliability and Safety Analysis in Engineering Design, Structural and Geotechnical Mechanics, Prentice – Hall Inc., Eaglewood Cliffs, New Jersey.

ANG, A.H–S, (1973), Structural Risk Analysis and Reliability-Based Design, Journal of the structural division, ASCE Vol. 100, No. ST9, pp 1891-1910.

BENNETT, R.M. AND ANG, A.H-S (1983), Investigation of Methods for Structural Systems Reliability,  Structural research series  No.  510, University of Illiniois, Urbana.

BROWN, C.B., (1960), Concepts of Structural Safety, Journal of the structural division, ASCE Vol. , No. ST12, pp 39-59.

BS 4360: (1990), Specification for weldable structural steel, Her majesty’s stationery office, London.

BS 5950: (1985), Structural use of Steelwork in Building, Part 2: Specification for materials fabrication and erection: Hot-rolled section, Her majesty’s stationery office, London.

StudentsandScholarship Team.