# NL-STRESS *** Non Linear STRuctural Engineering System Solver ***

NL-STRESS is a computer program for elastic and non linear (plastic and stability) analysis of skeletal structures.

A full version is supplied as part of SCALE for both Windows and iPad versions. Both version also contain many SCALE proforma data generators, for easy cration of NL-STRESS data files. The Windows version also has a GUI (Graphical User Interface) which permits the engineer to draw the structure to be analysed on the screen. Each data generator builds a data file (.DAT) which contains page headings for the results file followed by: joint coordinates, member incidences, loading and other data.

NL-STRESS results are in calc-sheet format supported by 2D/3D plots of bending moments, shear forces or deflections on the screen or printer. Results may be restricted to a selection of members and/or joints.

# Simple Changes.

Engineers analyse a frame many times experimenting with changes to the section properties, support conditions etc.; it is important therefore that changing the data be simple. No matter which method of data preparation is used (including drawing the structure on the screen using the GUI), a text file of data is created written in the NL-STRESS language. The engineer may use his/her favourite editor to change the data, or run NL-STRESS and use the simple editor incorporated into the program.

# Stability Analysis.

Prepare the data as for elastic analysis and give the commands 'METHOD SWAY' and 'NUMBER OF SEGMENTS 6' and 'NUMBER OF INCREMENTS 20'; where the 6 tells the program to divide each member into six segments, and the 20 tells the program to apply the loading in 20 increments. (If the structure is triangulated with loading applied only at the joints then it will also be necessary to provide an initial bow to each member to induce buckling, and this may be done by including a percentage e.g. 0.1 following the number of segments.) Guyed masts and other tension structures can be handled by METHOD SWAY, worked examples are provided.

# Plastic Analysis.

It is simple to find the collapse load factor for any frame which has been analysed elastically, by changing METHOD ELASTIC to METHOD PLASTIC, giving NUMBER OF INCREMENTS 40, doubling the working load, and giving the yield stress following the constants command. If the analysis reports collapse after say 36 increments then the collapse load factor is 36/(40/2)=1.8 (assuming the working load has been doubled).

When section properties are specified by shape (e.g. ISECTION) and dimensions, NL-STRESS computes plastic section properties automatically, and applies the appropriate interaction formulae for the shape, thus saving the engineer much time. False mechanisms are prevented, 'unloaded' plastic hinges are recognised and taken into account.

# Additional Features.

Members may have springs at their ends; and any member may be specified as 'tension only' or 'compression only'. NL-STRESS will compute elastic stresses.

The keyword COLLECTION causes the displacements for all loadcases for each joint to be collected and printed as a group; similarly for member forces, member stresses and support reactions.

The keyword DIAGRAMS also collects the results of all loadcases together for each member but presents the information as a diagram showing the bending moment and shear force envelopes.

The keyword AREA tells NL-STRESS to spread a load over an area of a grid. The keyword SUMMARY makes NL-STRESS print a summary of joint, member and loading data.

LOADING DYNAMIC <g>, where <g> is the acceleration due to gravity e.g. 9.80665 m/sec2, tells NL-STRESS that the loading case is to be treated as a dynamic loading and the natural frequency computed by energy methods.

# NL-STRESS Benchmarks.

NL-STRESS benchmarks are examples of data files, which cover a wide range of engineering structures. Embedded in the data will be found part of the results of an NL-STRESS analysis so that the problem may be run and the results obtained compared to those embedded in the data; therefore the set of data files may be used as benchmarks against which the results obtained from running the problem on a computer can be compared. Any technical references are given in the benchmark examples. The filename extension is given as .BMK (short for BenchMarK) to distinguish the files from other NL-STRESS data files. To get pictures of the benchmark examples, run NL-STRESS.

# Timing Benchmarks.

bm01.bmk Plane frame with 27 joints, 38 members & 2 load cases

bm02.bmk Space frame with 66 joints, 99 members & 1 load case

# Department Of Transport - HECB Calibration Test Benchmarks.

dt01.bmk Plane truss with varying relative stiffness

dt02.bmk Plane frame with displaced supports

dt03.bmk Plane frame problem (2)

dt04.bmk Encastre segmental arch rib

dt05.bmk Grillage with applied displacements & elastic supports

dt06.bmk Grillage with shear deformation

dt07.bmk Skew deck of orthogonal grillage

dt08.bmk Circular-arc bow girder

dt09.bmk Space truss

dt10.bmk Space frame with varying stiffnesses & displaced supports

# Dynamical Behaviour Benchmarks.

dy01.bmk Ex. from Fig 3.2 from Dynamical Behaviour of Stuctures

dy02.bmk Ex. from Table 12.2 in Steel Designers' Manual

dy03.bmk Ex. from Table 12.2 in Steel Designers' Manual

dy04.bmk Nat. freq of beam with point loads, Dunkerley's method

dy05.bmk Nat. freq example 10.3-2 by Coates, Coutie & Kong

dy06.bmk Nat. freq example in Fig 4.8 by GB Warburton

dy07.bmk Nat. freq example problem 1 in Chapter 1 by Warburton

dy08.bmk Nat. freq example problem 7 in Chapter 15 by Ryder

dy09.bmk Nat. freq grid problem cl.12.15 Steel Designers' Manual

# Plane Grid Benchmarks.

gr01.bmk Bridge deck from C&CA manual

gr02.bmk Foundation raft

gr03.bmk Authentic bridge deck

gr04.bmk Curved balcony member from Design Ex. 6 BC842 by SCI.

gr05.bmk Member stresses for sections defined by props or geometry

# Plane Frame Benchmarks.

pf01.bmk Shear wall

pf02.bmk Box culvert

pf03.bmk Influence lines

pf04.bmk Natural frequency determination

pf05.bmk Prestressed continuous beam

pf06.bmk Shear deformation - Ex. 6.7-1 by Coates Coutie & Kong

pf07.bmk Member loads - Example 6.7-2 by Coates Coutie & Kong

pf08.bmk Symmetry - Example 6.10-1 by Coates Coutie & Kong

pf09.bmk REPEAT-UNTIL-ENDREPEAT - Problem 6.1 by Coates et al.

pf10.bmk Looping across tables - Pr. 6.2 Coates Coutie & Kong

pf11.bmk Springs at supports - Pr. 7.18 by Coates Coutie & Kong

pf12.bmk Applied moments - Problem 8.5 by Coates Coutie & Kong

pf13.bmk DIAGRAMS example - Pr. 6.14 by Coates Coutie & Kong

pf14.bmk Propping force - Problem 6.16 by Coates Coutie & Kong

pf15.bmk Member distortions - Pr. 4.15 by Coates Coutie & Kong

pf16.bmk Temperature, self weights, length coefficients example

pf17.bmk Curved member, Design example 6 Job BCC 842 by SCI

pf18.bmk Temperature gradient, ex. from GIT-ICES STRUDL-II manual

pf19.bmk Stresses for sections defined by properties or geometry

pf20.bmk Member properties given by: AS other member properties

# Plastic Analysis Benchmarks.

pl01.bmk Single bay portal frame

pl02.bmk Two storey frame

pl03.bmk Plastic grillage

pl04.bmk Elastic-plastic analysis of compression members

pl05.bmk Reversing plastic hinge example

pl06.bmk Example 1.1 from Constrado publication 'Plastic Design'

pl07.bmk Example 1.2 from 'Plastic Design'

pl08.bmk Example 2.1 from 'Plastic Design'

pl09.bmk Example 2.3 from 'Plastic Design'

pl10.bmk Example 4.4 from 'Plastic Design'

pl11.bmk Example 4.7 from 'Plastic Design'

pl12.bmk Example 6.2 from 'Plastic Design'

pl13.bmk Test order of formation of plastic hinges

pl14.bmk Portal frame with out of plane loading

pl15.bmk Space frame - ring beam supported on RHS columns

pl16.bmk Example 14.6-1 from Coates Coutie and Kong

pl17.bmk Example 14.6-4 from Coates Coutie and Kong

pl18.bmk Example 14.6-5 from Coates Coutie and Kong

pl19.bmk Example 14.7-1 from Coates Coutie and Kong

pl20.bmk Example 14.7-2 from Coates Coutie and Kong

pl21.bmk Example 14.8-1 from Coates Coutie and Kong

# Plane Truss Benchmarks.

pt01.bmk Computer Methods in Solid Mech. by Gennaro: Example 20

pt02.bmk Computer Methods in Solid Mech. by Gennaro: Example 22

pt03.bmk Computer Methods in Solid Mech. Chapter 4 Problem 1

pt04.bmk Computer Methods in Solid Mech. Chapter 4 Problem 4

pt05.bmk Computer Methods in Solid Mech. Chapter 4 Problem 13

pt06.bmk Computer Methods in Solid Mech. by Gennaro: Example 31

pt07.bmk Computer Methods in Solid Mech. by Gennaro: Example 32

pt08.bmk Computer Methods in Solid Mech. by Gennaro: Example 33

pt09.bmk Computer Methods in Solid Mech. by Gennaro: Example 34

pt10.bmk Analysis of Indeterminate Structures Grassie: Ex. 4.10

# Space Frame Benchmarks.

sf01.bmk Cantilever stair

sf02.bmk Guide dolphin

sf03.bmk Example in Fig 3-8 from William Weaver

sf04.bmk Example in Fig 3-9 from William Weaver

sf05.bmk Example from UCC symposium Nov 1972

sf06.bmk Tapered beams example - equivalent to rect. section

sf07.bmk Cant. beam subjected to standard loadings from S.D.M.

sf08.bmk S.S. beam subjected to standard loadings from S.D.M.

sf09.bmk Built-in beam subject to standard loadings from S.D.M.

sf10.bmk Ring beam on T columns to show need for BETA angle

sf11.bmk Curved balcony member for SCI design example 6

sf13.bmk Member distortions for cantilever or built-in beam

sf14.bmk Temperature gradient, ex. from GIT-ICES STRUDL-II manual

sf15.bmk Stresses for sections defined by properties or geometry

# Sway Frame Benchmarks.

sw01.bmk Column with axial load (Euler buckling problem)

sw02.bmk Column with axial load and lateral load

sw03.bmk Guyed mast analysis

sw04.bmk Two storey frame

sw05.bmk Lateral displacement of tip of end loaded cantilever

sw06.bmk Suspension bridge with three pinned stiffening girder

sw07.bmk Comparison between member end springs & pseudo springs

sw08.bmk Modelling imperfections by parabolic bow

sw09.bmk Example 9.11-1 from Coates Coutie & Kong

sw10.bmk Problem 9.1 from Coates Coutie & Kong

sw11.bmk Problem 9.2 from Coates Coutie & Kong

sw12.bmk Problem 9.8 from Coates Coutie & Kong

sw13.bmk Problem 9.9 from Coates Coutie & Kong

sw14.bmk Problem 9.10 from Coates Coutie & Kong

sw15.bmk Problem 9.11 from Coates Coutie & Kong

sw16.bmk Problem 9.12 from Coates Coutie & Kong

sw17.bmk Two way net subjected to symmetrical loading

sw18.bmk Two way net subjected to unsymmetrical loading

sw19.bmk Hyperbolic paraboloid net

sw20.bmk Stable and unstable post-buckling behaviour

sw21.bmk Snap through - Problem 9.8-1 from Coates Coutie & Kong