Christchurch Town Hall Complex: Post-Earthquake Ground Improvement, Structural Repair, and Seismic Retrofit

2020 ◽  
pp. 145-172
Author(s):  
Gareth Morris ◽  
Mark Browne ◽  
Kirsti Murahidy ◽  
Mike Jacka
Keyword(s):  
Structural Damage ◽  
Soil Stabilization ◽  
Ground Improvement ◽  
Time History ◽  
Seismic Retrofit ◽  
Lateral Spreading ◽  
Town Hall ◽  
Structural Repair ◽  
Ground Deformations ◽  
Primary Focus

<p>The Christchurch Town Hall (CTH) complex contains six reinforced concrete buildings constructed circa 1970 in Christchurch, New Zealand (NZ). The complex is used for performing arts and entertainment, with an Auditorium that is internationally recognized for its acoustics. It is listed as a Grade-1 heritage building due to its cultural and historical significance. Unfortunately, the CTH foundation system was not originally designed to accommodate liquefaction-induced differential settlement and lateral spreading effects, as highlighted by the 2010–2011 Canterbury earthquake sequence. Although the most extreme ground motions exceeded the NZS 1170.5 code-defined 1/2500 year earthquake loads, the CTH structures performed remarkably well for a design that pre-dated modern seismic codes. Most of the observed structural damage was a result of the differential ground deformations, rather than in response to inertial forces. The post-earthquake observations and signs of distress are presented herein. The primary focus of this paper is to describe two major features of the seismic retrofit project (initiated in 2013) which were required to upgrade the CTH complex to meet 100% of current NZS 1170.5 seismic loadings. Firstly, the upgrade required extensive ground improvement and a new reinforce concrete mat slab to mitigate the impacts future ground deformations. Soil stabilization was provided by a cellular arrangement of jet-grout columns, a relatively new technique to NZ at the time. The new mat slab (typically 600-900 mm) was constructed over the stabilized soils. Secondly, upgrading the superstructure had many constraints that were overcome via a performance-based design approach, using non-linear time-history analysis. Recognizing the heritage significance, the superstructure “resurrection” as a modern building was hidden within the original skin minimized disruption of heritage fabric. Retrofit solutions were targeted, which also minimized the overall works. The 2015–2019 construction phase is briefly discussed within, including jet-grout procedures and sequencing considerations.</p>

North Torrey Pines Bridge Seismic Retrofit: Part I, Seismic Hazard and Geotechnical Design

2015 ◽  
Vol 31 (4) ◽  
pp. 2195-2210 ◽  
Author(s):  
James R. Gingery ◽  
Kevin W. Franke ◽  
Jorge F. Meneses ◽  
Zia Zafir
Keyword(s):  
Seismic Hazard ◽  
Seismic Performance ◽  
Site Response ◽  
Hazard Analysis ◽  
Ground Improvement ◽  
Time History ◽  
Seismic Retrofit ◽  
The North ◽  
Development Site ◽  
Geotechnical Design

This paper and its companion ( Johnson et al. 2015 ) summarize the design assumptions, processes, and analytical methods that were employed in the seismic retrofit of an historic bridge. The North Torrey Pines Road Bridge in Del Mar, California, was built in 1933 and is eligible for listing in the National Register of Historic Places. The bridge had been classified as structurally and seismically deficient and functionally obsolete. A seismic retrofit project was performed to improve the seismic performance of the bridge while preserving its aesthetic and historic character. This paper describes the geotechnical and seismic hazard aspects of the retrofit project, which included deterministic and probabilistic seismic hazard analysis, earthquake time-history development, site-response analyses, evaluation of liquefaction triggering and its consequences, seismic slope displacement evaluations, and soil-structure interaction analyses. Geotechnical retrofit measures, including ground improvement and new abutment foundations, were developed and tailored to improving seismic performance to levels that were compatible with the seismic design criteria. The information presented in these two papers provides a case history that can serve as a point of reference for practicing engineers facing similar challenges.

Damage-Involved Structural Pounding in Bridges under Seismic Excitation

2017 ◽  
Vol 754 ◽  
pp. 309-312 ◽  
Author(s):  
Robert Jankowski
Keyword(s):  
Structural Damage ◽  
Structural Model ◽  
Viscoelastic Model ◽  
Time History ◽  
Seismic Wave Propagation ◽  
Seismic Excitation ◽  
Lumped Mass ◽  
Positive Role ◽  
Contact Points ◽  
Elevated Bridge

During severe earthquakes, pounding between adjacent superstructure segments of highway elevated bridges was often observed. It is usually caused by the seismic wave propagation effect and may lead to significant damage. The aim of the present paper is to show the results of the numerical analysis focused on damage-involved pounding between neighbouring decks of an elevated bridge under seismic excitation. The analysis was carried out using a lumped mass structural model with every deck element discretized as a SDOF system. Pounding was simulated by the use of impact elements which become active when contact is detected. The linear viscoelastic model of collision was applied allowing for dissipation of energy due to damage at the contact points of colliding deck elements. The results show that pounding may substantially modify the behaviour of the analysed elevated bridge. It may increase the structural response or play a positive role, and the response depends on pattern of collisions between deck elements. The results also indicate that a number of impacts for a small in-between gap size is large, whereas the value of peak pounding force is low. On the other hand, the pounding force time history for large gap values shows only a few collisions, but the value of peak pounding force is substantially large, what may intensify structural damage.

Nonlinear Structural Damage Detection Based on Adaptive Volterra Filter Model

2018 ◽  
Vol 18 (02) ◽  
pp. 1871003 ◽  
Author(s):  
J. Prawin ◽  
A. Rama Mohan Rao
Keyword(s):  
Damage Detection ◽  
Structural Damage ◽  
Linear Models ◽  
Time History ◽  
Diagnostic Techniques ◽  
Filter Model ◽  
Volterra Filter ◽  
Damage Indices ◽  
Before And After ◽  
Nonlinear Time History

The majority of the existing damage diagnostic techniques are based on linear models. Changes in the state of the dynamics of these models, before and after damage in the structure based on the vibration measurements, are popularly used as damage indicators. However, the system may initially behave linearly and subsequently exhibit nonlinearity due to the incipience of damage. Breathing cracks that exhibit bilinear behavior are one such example of the damage induced due to nonlinearity. Further many real world structures even in their undamaged state are nonlinear. Hence, in this paper, we present a nonlinear damage detection technique based on the adaptive Volterra filter using the nonlinear time history response. Three damage indices based on the adaptive Volterra filter are proposed and their sensitiveness to damage and noise is assessed through two numerically simulated examples. Numerical investigations demonstrate the effectiveness of the adaptive Volterra filter model to detect damage in nonlinear structures even with measurement noise.

Systematic approach to assessing the applicability of fly-ash-based geopolymer for clay stabilization

2020 ◽  
Vol 57 (9) ◽  
pp. 1356-1368 ◽  
Author(s):  
Hayder H. Abdullah ◽  
Mohamed A. Shahin ◽  
Megan L. Walske ◽  
Ali Karrech
Keyword(s):  
Fly Ash ◽  
Systematic Approach ◽  
Soil Stabilization ◽  
Ground Improvement ◽  
Experimental Program ◽  
Attractive Alternative ◽  
Chemical Additives ◽  
Soil Mineralogy ◽  
Problematic Soils ◽  
Ph Level

Traditional soil stabilization by chemical additives such as cement and lime is a well-established technique for ground improvement of problematic soils. However, with the advantage of lower carbon emission and energy consumption, fly-ash-based geopolymer has recently become an attractive alternative to traditional stabilizers. Nevertheless, the literature lacks systemic approaches that assist engineers to apply this promising binder for soil stabilization, including the proper dosages required for an effective treatment. This paper introduces a systematic approach to assess the applicability of fly-ash-based geopolymer for stabilization of clay soils, through a comprehensive experimental program where engineered and natural clays were examined and evaluated, including soil compaction, plasticity, compressive strength, durability, pH level, and impact of pulverization. The results revealed several factors that influence the level of enhancement of geopolymer-treated clays, including the soil mineralogy, plasticity–activity properties, geopolymer concentration, curing time, and pulverization.

scholarly journals Geotechnical properties of reinforced clayey soil using nylons carry’s bags by products

2018 ◽  
Vol 162 ◽  
pp. 01020 ◽  
Author(s):  
Nahla Salim ◽  
Kawther Al-Soudany ◽  
Nora Jajjawi
Keyword(s):  
Soil Stabilization ◽  
Clayey Soil ◽  
Ground Improvement ◽  
Soft Soil ◽  
Liquid Limit ◽  
Waste Material ◽  
Industrial Wastes ◽  
Dry Density ◽  
Maximum Dry Density ◽  
Replacement Technique

All structures built on soft soil may experience uncontrollable settlement and critical bearing capacity. This may not meet the design requirements for the geotechnical engineer. Soil stabilization is the change of these undesirable properties in order to meet the requirements. Traditional methods of stabilizing or through in-situ ground improvement such as compaction or replacement technique is usually costly. Now a safe and economic disposal of industrial wastes and development of economically feasible ground improvement techniques are the important challenges being faced by the engineering community. This work focuses on improving the soft soil brought from Baghdad by utilizing the local waste material for stabilization of soil, such as by using “Nylon carry bag’s by product” with the different percentage and corresponding to 1 %, 3% and 5% (the portion of stabilizer matters to soil net weight) of dried soil. The results indicated that as Nylon’s fiber content increases, the liquid limit decreases while the plastic limit increases, so the plasticity index decreases. Furthermore, the maximum dry density decreases while, the optimum moisture content increases as the Nylon’s fiber percentage increases. The compression index (decreases as the Nylon’s fiber increases and provides a maximum of 43% reduction by adding 5% nylon waste material. In addition, the results indicated that, the undrained shear strength increases as the nylon fiber increases.

Seismic Isolation Retrofitting of Typical Multi-Span Steel Girder Bridges in New York State

2020 ◽  
Vol 2674 (8) ◽  
pp. 785-798 ◽  
Author(s):  
Dongming Feng ◽  
Fangyin Zhang
Keyword(s):  
New York ◽  
Seismic Isolation ◽  
Ground Motions ◽  
Limit State ◽  
New York State ◽  
Time History ◽  
Seismic Retrofit ◽  
Structural Members ◽  
York State ◽  
Simply Supported

Many of the existing multi-span simply supported bridges in New York State, U.S., are susceptible to earthquake damage and need to be retrofitted to reduce their seismic risk. In this study, seismic retrofit of a five-span simply supported bridge with typical high-type fixed and expansion steel rocker bearings is conducted. A refined three-dimensional (3D) finite element model of the bridge is developed in ANSYS by considering foundation impedances. Multi-support time history analyses have been implemented in the seismic retrofit design for two levels of ground motions: 1,000- and 2,500-year return period earthquakes. The site-specific ground motions with consideration of the spatial variation are generated based on the geotechnical information. Seismic retrofit by replacing existing steel bearings with lead-rubber bearing (LRB) isolators has been adopted. The parameters of the isolators are determined by considering factors such as the seismic performance and translational resistance during normal service. The vulnerability of structural members and seismic retrofit effectiveness are quantified by the demand-to-capacity (D/C) ratio for the combined demands at the extreme limit state. The analyses show that after seismic isolation retrofit the pervasive vulnerabilities in pier columns and cap beams are eliminated. Comparing with strengthening the vunerable structural members, seismic isolation is proved a cost-effective retrofit solution. The overall seismic isolation design and analysis procedures presented in this study can help guide future seismic retrofit of similar types of bridges.

Viscoelastic Coupling Dampers for Enhanced Multiple Seismic Hazard Level Performance of High-Rise Buildings

2018 ◽  
Vol 34 (4) ◽  
pp. 1847-1867 ◽  
Author(s):  
Renée MacKay-Lyons ◽  
Constantin Christopoulos ◽  
Michael Montgomery
Keyword(s):  
Seismic Hazard ◽  
Structural Damage ◽  
Time History ◽  
Coupled System ◽  
Nonlinear Time History Analysis ◽  
Coupling Beams ◽  
Restoring Force ◽  
High Rise ◽  
Amplitude Maximum ◽  
Hazard Level

Viscoelastic coupling dampers (VCDs) are installed in lieu of traditional reinforced concrete (RC) coupling beams in high-rise buildings to provide distributed supplemental damping for all dynamic loading conditions without affecting the architectural layout. When distributed effectively over the height of the building, VCDs provide viscous damping in all lateral modes of vibration and an elastic restoring force that enhances the lateral stiffness of the coupled system. In this paper, a first extensive numerical case study is carried out to compare the seismic performance of a conventional coupled shear wall high-rise building to a high damping alternate of the same design in which VCDs replace all diagonal RC beams in the core to enhance its seismic resilience. The added damping from VCDs is intended to reduce the peak responses under low amplitude earthquakes, but for larger amplitude maximum credible earthquakes, the peak responses are similar; however, structural damage is greatly reduced. Three seismic hazard levels were investigated, and the results indicate that the use of VCDs reduces peak floor accelerations, story drifts, and story shears over all seismic intensities. Nonlinear time-history analysis results also highlighted the improved resilience of the VCD structure at the maximum credible seismic hazard level where the use of VCDs eliminated all damage to coupling beams that would otherwise require repair over most of the height of the building.

scholarly journals Liquefaction and Related Ground Failure from July 2019 Ridgecrest Earthquake Sequence

2020 ◽  
Vol 110 (4) ◽  
pp. 1549-1566 ◽  
Author(s):  
Paolo Zimmaro ◽  
Chukwuebuka C. Nweke ◽  
Janis L. Hernandez ◽  
Kenneth S. Hudson ◽  
Martin B. Hudson ◽  
...  
Keyword(s):  
Lateral Spreading ◽  
Earthquake Sequence ◽  
Ground Failure ◽  
Liquefaction Susceptibility ◽  
Ground Deformations ◽  
Us Military ◽  
Liquefaction Hazard ◽  
Frame Buildings ◽  
Sand Boils ◽  
Wood Frame

ABSTRACT The 2019 Ridgecrest earthquake sequence produced a 4 July M 6.5 foreshock and a 5 July M 7.1 mainshock, along with 23 events with magnitudes greater than 4.5 in the 24 hr period following the mainshock. The epicenters of the two principal events were located in the Indian Wells Valley, northwest of Searles Valley near the towns of Ridgecrest, Trona, and Argus. We describe observed liquefaction manifestations including sand boils, fissures, and lateral spreading features, as well as proximate non-ground failure zones that resulted from the sequence. Expanding upon results initially presented in a report of the Geotechnical Extreme Events Reconnaissance Association, we synthesize results of field mapping, aerial imagery, and inferences of ground deformations from Synthetic Aperture Radar-based damage proxy maps (DPMs). We document incidents of liquefaction, settlement, and lateral spreading in the Naval Air Weapons Station China Lake US military base and compare locations of these observations to pre- and postevent mapping of liquefaction hazards. We describe liquefaction and ground-failure features in Trona and Argus, which produced lateral deformations and impacts on several single-story masonry and wood frame buildings. Detailed maps showing zones with and without ground failure are provided for these towns, along with mapped ground deformations along transects. Finally, we describe incidents of massive liquefaction with related ground failures and proximate areas of similar geologic origin without ground failure in the Searles Lakebed. Observations in this region are consistent with surface change predicted by the DPM. In the same region, geospatial liquefaction hazard maps are effective at identifying broad percentages of land with liquefaction-related damage. We anticipate that data presented in this article will be useful for future liquefaction susceptibility, triggering, and consequence studies being undertaken as part of the Next Generation Liquefaction project.

scholarly journals Fragility Assessment of a Container Crane under Seismic Excitation Considering Uplift and Derailment Behavior

2019 ◽  
Vol 9 (21) ◽  
pp. 4660
Author(s):  
Quang Huy Tran ◽  
Jungwon Huh ◽  
Nhu Son Doan ◽  
Van Ha Mac ◽  
Jin-Hee Ahn
Keyword(s):  
Structural Damage ◽  
Seismic Vulnerability ◽  
Fragility Curves ◽  
Three Dimensional ◽  
Time History ◽  
Element Model ◽  
Seismic Excitation ◽  
Damage State ◽  
Limit States ◽  
Container Crane

While the container crane is an important part of daily port operations, it has received little attention in comparison with other infrastructures such as buildings and bridges. Crane collapses owing to earthquakes affect the operation of the port and indirectly impact the economy. This study proposes fragility analyses for various damage levels of a container crane, thus enabling the port owner and partners to better understand the seismic vulnerability presented by container cranes. A large number of nonlinear time-history analyses were applied for a three-dimensional (3D) finite element model to quantify the vulnerability of a Korean case-study container crane considering the uplift and derailment behavior. The uncertainty of the demand and capacity of the crane structures were also considered through random variables, i.e., the elastic modulus of members, ground motion profile, and intensity. The results analyzed in the case of the Korean container crane indicated the probability of exceeding the first uplift with or without derailment before the crane reached the structure’s limit states. This implies that under low seismic excitation, the crane may be derailed without any structural damage. However, when the crane reaches the minor damage state, this condition is always coupled with a certain probability of uplift with or without derailment. Furthermore, this study proposes fragility curves developed for different structural periods to enable port stakeholders to assess the risk of their container crane.

Shear Strength of BC-Soil Admixed with Lime and Bio-Enzyme

2019 ◽  
Vol 969 ◽  
pp. 327-334
Author(s):  
C. Jairaj ◽  
M.T. Prathap Kumar ◽  
H. Muralidhara
Keyword(s):  
Shear Strength ◽  
Soil Stabilization ◽  
Morphological Changes ◽  
Ground Improvement ◽  
High Strength ◽  
Sem Analysis ◽  
Dry Density ◽  
Test Results ◽  
Maximum Dry Density ◽  
Lime Content

This BC Soil are expansive in nature and are problematic because of low shear strength and high compressibility. Review of literatures have proven that addition of lime imparts high strength with a corresponding reduction in swell of BC soils. In addition, Bio-enzymes have also been found to play a key role as activators in improving the characteristics of clayey soils such as BC soil. Development and use of non-traditional ground improvement techniques such as bio-enzymes in combination with lime for soil stabilization helps to reduce the cost and the detrimental effects on the soil environment. In the present study lime and bio-enzymes were used as soil stabilizing agents. Compaction test results on BC soil admixed with different percent of lime indicated that 3% addition lime gives higher maximum dry density of 17kN/m3 with OMC of 21% compare to other addition of lime percentages. Keeping 3% of lime as optimum lime content(OLC), BC Soil was admixed with different dosages of Bio-enzymes 25ml/m3, 50ml/m3, 100 ml/m3,150ml/m3, and 200ml/m3 along with OLC was tested for compaction and unconfined compressive strength(UCC). Further UCC test was carried out for different curing period of 0, 7, 15, 30, and 60 Days to analyse the long term effect of BC soil admixed with bio-enzymes with and without lime content. Morphological and chemical analysis was done by using XRD and SEM analysis, from all the test results it was found that 3%OLC + 75ml/m3 of bio-enzymes for 7 day of curing gives higher UCC of 450 kPa. From the SEM it was found that better bond between particles found to develop in bio-enzyme+ lime admixed BC soil in comparison with lime alone admixed BC soil. XRD studies indicated morphological changes in crystallinity and structure of stabilized BC soil in comparison to BC soil alone.

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