Institute for Infrastructure Engineering

Past literature suggests that the irrigation using recycled water over long period of time can lead to accumulation of salt in the soil. In this study, an assessment framework is proposed to evaluate the salinity sources that can have significant impact on the vadose zone salinity when recycled water is used for irrigating sporting ovals. The framework is constructed with a probabilistic expert system, namely, Bayesian Belief Network (BBN). The BBN model analyses the exposure pathways of salt arising from households to its final destination, i.e., accumulation in the soil via the recycled water irrigation. The salt transport modelling indicated a general trend of increase in both total dissolved solids (TDS) and Na þ concentration in the root zone for a simulation period of 1277 days. The BBN analyses indicated that the wastewater stream from washing machines was the major salt source influencing soil salinity, closely followed by the wastewater stream from toilets. Results show that by reducing TDS load by 50% from washing machine alone, reduces the TDS concentration in soil by about 9% and this can be increased to 19% by reducing the TDS loads from both washing machine and toilet water, simultaneously. The study highlighted that any strategies that help in the reduction of salt in the wastewater stream from washing machine will be beneficial in managing the soil salinity as a result of recycled water use for irrigation. Thus, the proposed framework can help to develop recycled water irrigation schemes which are sustainable over the long-run.

This paper reports on a numerical attempt toward developing a nonlinear finite element (FE) modelling approach to predict the inelastic behaviour of reinforced concrete (RC) beam-column connections retrofitted using externally bonded fibre reinforced polymer (FRP) composites. The reliability of the modelling approach and analysis results is verified against a series of experimental tests conducted in the current study and available in the literature. These tests implemented two retrofitting schemes including web- and flange-bonded configurations; commonly used for retrofitting of the beam-column joints. The retrofitting method in all adopted experimental tests is aimed at relocating the plastic hinges away from the column face further into the beam. The FE results are compared with the experimental findings in terms of load-displacement curves, failure modes, and plastic hinge locations. A good agreement is observed between the FE results and experimental observations. It is concluded that the proposed FE analysis can be reliably used as a cost-effective tool to predict the elastic and inelastic behaviour of FRP retrofitted RC beam-column connection and to investigate the effect of parameters that are beyond the scope of the experimental tests.
Keywords: Nonlinear FE analysis, RC beam-column connection, FRP, Plastic hinge, Strengthening

Post-Earthquake Fire (PEF) can lead to the collapse of buildings that are partially damaged in a prior earthquake that occurred
immediately before the fire. The majority of standards and codes for the design of structures against earthquake ignore the possibility
of PEF and thus buildings designed with those codes fail prematurely when subjected to PEF. A sequential analysis based on
FEMA356 is performed here on the Immediate Occupancy (IO), corresponding to a structure designed as school occupancy, and Life
Safety (LS) performance levels, corresponding to a structure designed as reside ntial occupancy, of two steel moment resisting
frames. These frames are first subjected to an earthquake load with the PGA of 0.35g. This is followed by a fire analysis, using both
the ISO834 model and the Natural fire model. The time it takes for the structure weakened by the earthquake to collapse under fire is
then calculated. As a point of reference, fire only analyses are also performed for the undamaged structures. The results show that
earthquake weakened structures are more vulnerable to fire than undamaged structures. The results also show that both fire resistance
and PEF resistance of the frame designed as school are more than the frame designed as residential. Whilst the investigation is for a
certain class of structures (steel moment resisting frames, 5 stories), the results confirm the need for the incorporation of PEF in the
process of analysis and design and provides some quantitative measures on the level of associated effects.

Post-earthquake fire (PEF) is considered one of the most high risk and complicated
problems affecting buildings in urban areas and can cause even more damage
than the earthquake itself. However, most standards and codes ignore the
implications of PEF and so buildings are not normally designed with PEF in
mind. What is needed is for PEF factors to be routinely scrutinized and codified
as part of the design process. A systematic application is presented as a means
of mitigating the risk of PEF in urban buildings. This covers both existing buildings,
in terms of retrofit solutions, and those yet to be designed, where a PEF
factor is proposed. To ensure the mitigation strategy meets the defined criteria, a
minimum time is defined – the safety guaranteed time target – where the safety
of the inhabitants in a building is guaranteed.

Post-earthquake fire (PEF) presents a risky situation to buildings that have been partially damaged in a prior
earthquake, particularly in urban areas.Asmost standards ignore the possibility of fire after earthquake, buildings
are not adequately designed for that possibility and thus PEF is a high-risk load needed to be scrutinized further,
codified and become part of a routine design. An investigation based on sequential analysis inspired by FEMA356
is performed here on a two story RC frame, at the Life Safety performance level and designed to the ACI 318-08
code, after it has been subjected to a spectral PGA of 0.35 g. The results showthat structures previously damaged
by the earthquake and exposed to PEF are considerablymore vulnerable than the structures,which have not been
damaged previously. A method of strengthening using Carbon Fiber Reinforced Polymer (CFRP) wraps is
introduced in order to relocate plastic hinges away from the column faces towards the beams. This method
increases the structural load carrying capacity, and thus reduces the potential damage from a potential
earthquake, improving the fire resistance. The results show a considerable improvement in the PEF resistance
of the frame.

The useofcold-formedsteel(CFS)frameshasgrownextensivelyinrecentyears,particularlyinthe
earthquake-proneregions.However,thebehavioroflateralresistingsystemsinCFSstructuresunder
seismic loadshasnotbeenscrutinizedindetail.Towardsthis,anexperimentalinvestigationhasbeen
conducted oncoldformedsteelframessheathedbythingalvanizedsteelplates,theresultsofwhichare
presentedhere.Theexperimentsinvolve24full-scalesteelplatedwallstestedundercyclicloadingwith
different configurations ofstudsandscrews.Ofparticularinterestwerethespecimens'maximumlateral
load capacityandtheload-deformationbehavioraswellasarationalestimationoftheseismicresponse
modification factor, R. Thestudyalsoevaluatesthefailuremodesofthesystems.Themainfactors
contributing totheductileresponseoftheseshearwallsarealsodiscussedinordertosuggest
improvementssothatthewallsrespondplasticallywithasignificant driftandwithoutanyriskof
brittle failure.

Post earthquake fire (PEF) can lead to the collapse of buildings that are partially damaged in a
prior ground-motion that occurred immediately before the fire. The majority of standards and codes for the
design of structures against earthquake ignore the possibility of PEF and thus buildings designed with those
codes could be too weak when subjected to a fire after an earthquake. An investigation based on sequential
analysis inspired by FEMA356 is performed here on the Life-Safety performance level of structures
designed to the ACI 318-08 code after they are subjected to two different earthquake levels with PGA of
0.35 g and 0.25 g. This is followed by a four-hour fire analysis of the weakened structure, from which the
time it takes for the weakened structure to collapse is calculated. As a benchmark, the fire analysis is also
performed for undamaged structure and before occurrence of earthquake. The results show that the
vulnerability of structures increases dramatically when a previously damaged structure is exposed to PEF.
The results also show the damaging effects of post earthquake fire are exacerbated when initiated from
second and third floor. Whilst the investigation is for a certain class of structures (regular building,
intermediate reinforced structure, 3 stories), the results confirm the need for the incorporation of post
earthquake fire in the process of analysis and design and provides some quantitative measures on the level of
associated effects.

External application of fiber-reinforced polymers (FRPs) for the seismic retrofit/repair of reinforced concrete (RC) beam–column
joints has been extensively investigated in the last decade. However, the majority of the suggested FRP schemes follow the application of the
composite sheets on the webs of the beam and the joint core which would be impeded in real three-dimensional structures due to the presence
of cross beams and slabs. In addition, upgrading code-compliant RC joints using a practical FRP scheme needs to be scrutinized in detail. A
desirable retrofitting scheme for this type of joints may follow the application of composite sheets on the top and bottom sides (flanges) of the
beam and columns aimed at increasing the flexural strength of beam–column joints. However, the major issue of concern for a flange-bonded
FRP is providing adequate development length from the critical section to transfer the FRP tensile forces from beam to columns and vice
versa. To overcome this concern, a novel anchorage system for flange-bonded carbon FRP (CFRP) is developed in this study and its efficiency
is evaluated through a comprehensive experimental program. In total, nine small-scale (1=2.85) beam–column test specimens, including two
control specimens, one damaged specimen, and six retrofitted specimens were considered. Both monotonic and cyclic loading regimes were
implemented to estimate, albeit approximately, the seismic responses of the test specimens. The load-carrying capacity, initial stiffness,
displacement ductility, and dissipated energy of beam–column joint subassemblies are compared before and after the application of the
CFRP retrofits. The results showed a remarkable improvement in the load-carrying capacity and elastic stiffness of CFRP-retrofitted
specimens, thus confirming the efficiency of the suggested anchorage system. In addition, and subject to specific circumstances, the
plastic hinge can also be relocated away from the beam–column interface

Wind loads are very important in the design of tall buildings as often the load combinations containing the
wind load govern the design. As for reliability, however, because of the higher inherent uncertainty in the
wind load in comparison to the gravity load, safety indices decrease as the ratio of wind load to gravity
load increases. The safety indices in RC columns depend on the nominal wind to gravity load ratios. Due
to the interaction between bending moment and axial force, a single ratio cannot be defi ned, because the
eccentricity is not similar for wind and gravity loads. In this paper, the ratio of wind to gravity loads is
considered separately for axial force and bending moments. Unlike conventional approach, here it is
assumed that the wind and gravity loads’ eccentricities are not equal, and the fi nal load eccentricity used
in either the design or the reliability analysis is a function of applied loads. The results demonstrate that
the sensitivity of RC columns’ safety indices to bending moment ratios is higher than that of axial force
ratios. Furthermore, the variation of RC columns’ safety indices with a low rebar percentage is very different
from RC columns with high rebar percentages. Copyright © 2010 John Wiley & Sons, Ltd.

level of performance of the Federal Emergency Management Agency (FEMA) 356 code by exposing it
to post-earthquake fire (PEF). The fire curve is accounted for using the natural fire method, and the fire is
subjected to the floors vertically in three different scenarios: (a) fire initiated from the first floor, (b) fire initiated
from the fourth floor and (c) fire initiated from the seventh floor. A delay of 5minutes and 25minutes are considered
for spreading the fire between the floors. To make a comparison between the results, a concurrent fire is
also considered for the fire analysis. The results indicate that the PEF resistance of the frame exposed to the
concurrent fire and the 5 minutes delay is much lower than that with a delay of 25 minutes. The results also
show that subjecting the frame to a delayed fire of 25 minutes leads to the collapse of the frame during
cooling phase, whereas in the other scenarios, the frame collapses during heating phase. As a result, more
considerations need to be implemented in the codes on top of that for the PEF itself and that is the appropriate
rate of spread of fire between floors

A differential model is presented to show the behavior of general hysteretic systems considering all relevant structural characteristics,
including pinching, stiffness degradation, load deterioration, and sliding. This model is generated based on Mostaghel’s model, which
already includes all of these characteristics except sliding. Thus, an attempt is made to develop the model to also cover sliding. A single-degreeof-
freedom system is used to develop the hysteretic model by writing a system of ordinary differential equations. The proposed model captures
the key features of the hysteretic cycles of any structure using some measurable system parameters through tests. A few examples of bilinear
systems excited by harmonic loads are provided to show that the descriptions of the force-displacement performance of general hysteretic
systems are realistic

Relocation of nonlinear inelastic hinges away from the column faces towards the beams using externally bonded carbon fibre reinforced polymer (CFRP) is suggested as a promising method for retrofitting of reinforced concrete (RC) joints. This approach would also prevent the formation of undesirable brittle joint failure. In order to investigate the effects of this type of retrofit in the seismic performance of RC buildings, a numerical investigation pertaining to strengthening of an 8-storey intermediate RC frame using CFRP was conducted. The retrofit strategy focused on the relocation of the plastic-prone region away from the column faces and out into the beams. To pursue this objective, composite sheets were applied at the top and bottom sides of the plastic hinge regions of beams increasing the bending moment resistance. The additional flexural stiffness generated by the composite materials at the beam to column connections is calculated by a comparison of the moment-rotation of CFRP retrofitted and original joints obtained from the finite element analysis. A rigorous seismic assessment of the retrofitted frame was implemented using the nonlinear pushover procedure and the capacity spectrum approach. The analysis results indicate that a rehabilitation design as described combined with the strong-column weak-beam design philosophy would improve the seismic performance of structures significantly.

The effectiveness of fibre reinforced polymers (FRPs) in retrofitting/repairing of the reinforced concrete (RC) components has been studied in the past to great detail. However, the seismic performance of RC structures retrofitted using FRP composites is yet to be scrutinized in terms of lateral resistance, ductility, and failure mechanism. This is of high importance if the retrofitted structures are to withstand higher seismic ground motions than they were designed for and/or pulse-type ground motions. In a comparative study, this paper reports on the results of an investigation into the flexural strengthening of RC buildings using glass/carbon fibre reinforced polymers (GFRP/CFRP). An 8-storey code-compliant RC building was considered as the case study to represent the medium-rise structures. With a slight intervention in the lateral displacement ductility and provision of the weak-beam strong-column design philosophy, the strengthening design strategy is aimed at increasing the lateral resistance. For this purpose, composite sheets are designed to be applied at the two end regions of all beams and columns on a practical flange-bonded scheme. The nonlinear pushover analysis with lumped plasticity approach was implemented in order to compare the seismic response of the original structure with the GFRP/CFRP retrofitted structures. Following validation of the adopted models, the force-deformation curves of the nonlinear plastic hinges are determined in a rigorous approach considering the material inelastic behaviour, reinforcement details, and dimensions of the members. While the nonlinear results confirm a significant increase in the lateral load carrying capacity using both composite materials, the CFRP improvement was as much as twice of the GFRP. However, the latter provides higher ductility.

Detailed investigation of the lateral performance of K-braced cold-formed steel structures and their response
modification coefficients, R factor, are presented in this paper. A total of 12 full-scale 2.4×2.4 m specimens of
different configurations are considered, and the responses investigated under a standard cyclic loading regime.
Of particular interest are the specimens' maximum lateral load capacity and deformation behavior as
well as a rational estimation of the seismic response modification factor. The study also looks at the failure
modes of the system and investigates the main factors contributing to the ductile response of the CFS walls
in order to suggest improvements so that the shear steel walls respond plastically with a significant drift
and without any risk of brittle failure, such as connection failure or stud buckling. A discussion on the calculated
response factors in comparison to those suggested in the relevant codes of practice is also presented.

In a strong earthquake, an RC column develops plastic deformations in regions often defined
as plastic hinge regions. The formation of a plastic hinge in an RC column in these regions depends
on the characteristics of the earthquakes as well as on the column details. Recordings from recent
earthquakes have demonstrated that ground motions in near field to a rupturing fault can contain a
large energy. This energy can cause considerable damage during an earthquake. Therefore, many recently
designed and constructed buildings may require strengthening in order to perform well when subjected
to near-fault earthquakes. Fiber Reinforced Polymers are considered to be a viable strengthening method
due to their relatively easy and quick installation. In this paper, 1350 inelastic time-history analyses
have been performed to predict the nonlinear behavior of FRP strengthened RC columns under both
far-fault and near-fault earthquakes. The effects of axial load, height-depth ratio and the amount of
longitudinal reinforcement, as well as different characteristics of earthquakes, are evaluated and the
results are compared with the corresponding experimental data. Based on the results, simple expressions
are proposed that can be used to estimate plastic hinge length of FRP strengthened RC columns subjected
to both far- and near-fault earthquakes.

Experimentalinvestigationswereconductedtoevaluatethelateralseismiccharacteristicsoflight-
weightknee-bracedcold-formedsteelstructures.Inall,fourfull-scale2.42.4 m2 specimenswith
differentconfigurationsweretestedunderastandardcyclicloadingregime.Thispaperfocusesonthe
specimens’maximumlateralloadcapacityanddeformationbehaviorandprovidesarationalestimate
of theseismicresponsemodificationfactor, R, ofknee-bracedwalls.Thestudyalsolooksatthefailure
modes ofthesystemandinvestigatesthemainfactorscontributingtotheductileresponseofCFSwalls.
That isinordertosuggestimprovementssothattheshearsteelwallsrespondplasticallywitha
significantdriftandwithoutanyriskofbrittlefailure,suchasconnectionfailureorstudbuckling.
A discussiononthecalculatedresponsefactorsincomparisontothosesuggestedintherelevantcodes
of practiceisalsopresented.