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FENET THEMATIC NETWORK COMPETITIVE AND SUSTAINABLE GROWTH (GROWTH) PROGRAMME Industry Sector RTD Thematic Area Date Civil Construction Durability and Life Extension 13 11 01 Application of Discrete/Finite Element Algorithms to the Analysis of Masonry Buildings and Bridges Carl Brookes Gifford Consulting Engineers, Southampton, UK Summary The presentation describes the application of discrete/finite element (DE) algorithms to the analysis of masonry buildings and bridges. Several illustrations will be given where these highly non-linear simulations are being used for structural assessment and in the design of strengthening schemes.

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FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Industry Sector RTD Thematic Area DateCivil Construction Durability and Life Extension 13 11 01

Application of Discrete/Finite Element Algorithms to the Analysis of Masonry Buildings and Bridges

Carl BrookesGifford Consulting Engineers, Southampton, UK

SummaryThe presentation describes the application of discrete/finite element (DE) algorithms to the analysis of masonry buildings and bridges. Several illustrations will be given where these highly non-linear simulations are being used for structural assessment and in the design of strengthening schemes.

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Introduction

Intoduction

• Discrete Element Technique Applied to Masonry• Ancient and modern

• Application to Masonry Arch Bridges• Static coded vehicle loads• Unstrengthened and strengthened conditions

• Application to Buildings - Seismic• In-plane behaviour of stone shear walls

– Earthquake loading– Existing and retrofitted structures

• Application to Buildings - Blast• Out-of-plane behaviour of brick/block walls

– Blast Loading– Existing and retrofitted structures

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Discrete Element analysis

A development of the distinct element technique, 1971Implemented by Rockfield Software Limited in ELFEN, current version 2001

Discrete modelled parts

Boundary interface models• To deal with contact, gaps, friction along perimeter edges

Adaptivity for evolving discrete parts• Required if fracturing takes place

Overall behavior is highly non-linear

Modelled parts are simple

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Discrete Element Simulation - Blocky2D seismic analysis to investigate in-plane behaviour of stone façade

Artificial horizontal ground motion 0.3g

Contours show principal compressive stresses with varying scale.

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Discrete Element Simulation - Brittle2D simple cyclic base shearing

Mesh adaptivity used to model fracturing process there after DE contact and interface laws apply.

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Application to Masonry Arch Bridges

Application to Masonry Arch Bridges• Static coded vehicle loads• Unstrengthened and strengthened conditions

Prediction and Verification• Study looking at past full scale tests of redundant bridges• Simulation of more recent laboratory models tested at TRL• Aim to concentrate on 2D behaviour (keep things as simple as possible)

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Torksey BridgeLincolnshire, 1986

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Spandrel Splitting from Barrel

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Arch starting to collapse

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Arch post failure

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Arch collapse

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Collapsefailure is not involving spandrel walls

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Torksey Bridge SimulationFirst discrete element simulation of arch in 1997

2D plain strain model. Ignores spandrel walls

Contours show principal stresses. Blue shows compression

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

TRL Unstrengthened ArchCarried out in 1997

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Barrel construction

Hand made bricks, radial mortar joints weak mortar, circumferential sand joints to represent ring

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

TRL Unstrengthened Test SimulationModel 18.elf, ELFEN v3.0.0b

2D plain strain model. Ignores spandrel walls.

Contours show principal compressive stresses. Blue shows highest compression.

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

TRL Unstrengthened Test Strength Prediction

Unstrengthened Arch Test with Simulation in Load Control(contact damping set to 0.5, Fc to 3.5 N/mm2)

-100000

-90000

-80000

-70000

-60000

-50000

-40000

-30000

-20000

-10000

0

-0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02Vertical Intrados Displacement [m]

Load

[N] 1/4 Point

2/4 Point3/4 Point1/4 TRL Test

Test Data

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Strengthening Masonry Bridges

Background in UK

• 40,000 Masonry arch bridges in UK (highways, railways, canals)• most are over 100 years old• many have inadequate strength

• Environmental deterioration• Increased live loading

• EC directive requires trunk roads to have 40 tonne rating Type of strengthening

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Formulation of Strengthening and Requirements

Requirements• minimal change to the bridges appearance• minimal impact on bridge users and existing services• provide an adequate increase in load carrying capacity• exhibit long term durability• exhibit a ductile failure mechanism• be cost effective

Internal strengtheningRetrofitted reinforcement (Cintec)

• stainless steel reinforcement bars• bond to masonry by patented grout and sock• precision drilling and setting out

Rigorously engineered design

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Mass or Reinforced Concrete Saddle

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Mass or Reinforced Concrete SaddleExcavation of fill prior to installation of concrete saddle

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Tangential ReinforcementRetrofitted using Cintec Anchors

tangential reinforcement installedfrom carriageway and, in certain circumstances, from below

The System

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Tangential ReinforcementMode of Behaviour

To prevent classic 4 hinge failure

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

TRL ARCHTEC TestFirst Test Carried out in 1998

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Modelled Cintec Anchors

Separate finite element meshShear coupling model for bondAxial formulation for elastic and non-linear

material behaviour

tension

compression

Axial stress

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Failure of Inner Ring

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Failure of Inner Ring

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Failure of Inner RingExposing Cintec Anchors

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Test After Inner Ring Collapse

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

TRL First ARCHTEC Strengthened SimulationModel 24.elf, ELFEN v3.2.52

2D plain strain model. Ignores spandrel walls.

Contours show principal compressive stresses. Blue shows highest compression.

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

First ARCHTEC Test Strength Predictions

TRL Test Strengthened in Load Control

-250000

-200000

-150000

-100000

-50000

0

-0.04 -0.03 -0.02 -0.01 0.00 0.01 0.02Vertical Intrados Displacement [m]

Load

[N]

1/4 Point2/4 Point3/4 PointTRL Test 1/4TRL Test 2/4TRL Test 3/4

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Comparison of TRL Laboratory Test Results

-250000

-200000

-150000

-100000

-50000

0

-0.03 -0.025 -0.02 -0.015 -0.01 -0.005 0

Intrados Displacement [m]

Load

Rea

ctio

n [N

/m]

UnstrengthenedFirst ArchtecSecond Archtec

44.8 Tonnes

41.5 Tonnes

20 Tonnes

Both Archtecarches more than double the capacity of the unstrengthenedarch

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

ConclusionsApplication to Masonry Arch Bridges

CONCLUSIONS

The performance of unstrengthened and strengthened arches can be simulated using the discrete element technique

• Compared with conventional methods DE assessments give best possible estimate of strength

Best possible live load assessments can be carried out.• Over 60 bridges have now been strengthened using DE based designs

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Application to Buildings – SeismicShear wall investigation

Application to Buildings - Seismic• In-plane behaviour of stone shear walls

• Earthquake loading – dynamic loads• Existing and retrofitted structures

Macro-block - weak mortar• Ancient masonry with very weak or no mortar

Brittle material - strong mortar• Ideally suited to model masonry where mortar and block strengths are similar

Sensitivity analysis• various retrofitted reinforcement arrangements

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Masonry shear wall details(all dimensions in mm)

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

General arrangement of idealised building

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Typical ashlar wall

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Unstrengthened simulation – 0.3g loading

Principal compressive stresses in N/m2

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Strengthening arrangements (13,19,20,21)

Horizontal, Vertical and diagonal Cintecanchors installed from the roof and at the corners

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Strengthened simulation – 0.3g loading

Principal compressive stresses in N/m2

Combined arrangement No. 21

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

ConclusionsApplication to Buildings – Seismic

CONCLUSIONS

Indications are that the overall performance of masonry acting compositely with retrofitted reinforcement can be predicted

• Predicted damage looks similar to that occurring in actual buildings• Verified for other masonry applications, static and high speed dynamic

Numerical modelling is valuable as a virtual test bench for strengthening• Currently strengthening of non-engineered buildings is often based on how

designs faired after Earthquakes• Full-scale testing is very expensive

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Application to Buildings – BlastOut-of-plane behaviour of brick/block walls

Application to buildings - Blast• Out-of-plane behaviour of brick/block walls

• Blast Loading• Existing and retrofitted structures

Very fast dynamic load• Load applied typically in 5ms• Strain rate in materials very important

Sensitivity analysis• Experimental test programme• various retrofitted reinforcement arrangements

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Strengthening to Resist Blast

Strengthened hollow concrete block wall subjected to severe blast load

Before – front view After – front view

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Strengthening to Resist Blast

Strengthened hollow concrete block wall subjected to severe blast load

Before – rear view After – rear view

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Strengthened Simulationdecoupled analysis, Elfen & Air3D

The wall was subjected to a blast load from 200kg TNT NEQ @ 12.5m; 534kPa, 1274kPa-ms (440lbs TNT NEQ @ 41ft; 77psi, 185psi-ms).

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Unstrengthened Simulationdecoupled analysis, Elfen & Air3D

The wall was subjected to a blast load from 200kg TNT NEQ @ 12.5m; 534kPa, 1274kPa-ms (440lbs TNT NEQ @ 41ft; 77psi, 185psi-ms).