Design Of Underground Structures Research Articles

Soil-Structure Interaction Effects on Seismic Response of multi-story Buildings on Raft Foundation

The investigation on the energy transfer mechanism from soils to buildings during earthquakes is critical for the design of earthquake resistant structures and for upgrading existing structures. Thus the need for research into Soil-Structure Interaction (SSI) problems is greater than ever. Moreover, recent studies show that the effects of SSI may be detrimental to the seismic response of structure and neglecting SSI in analysis may lead to un-conservative design. Despite this, the conventional design procedure usually involves assumption of fixity at the base of foundation neglecting the flexibility of the foundation, the compressibility of soil mass and consequently the effect of foundation settlement on further redistribution of bending moment and shear force demands. Hence the soil-structure interaction analysis of multi-story buildings is the main focus of this study; the effects of SSI are analyzed for typical multi-story building resting on raft foundation. Three methods of analysis are used for seismic demands evaluation of the target moment resistant frame buildings: equivalent static load (ESL); response spectrum (RS) methods and nonlinear time history (TH) analysis with suit of nine time history records. Three-dimensional FEM model is constructed to analyze the effects of different soil conditions and number of stories on the vibration characteristics and seismic response demands of building structures. Numerical results obtained using soil structure interaction model conditions are compared to those corresponding to fixed-base support conditions. The peak responses of story shear, story moment, story displacement, story drift, moments at beam ends, as well as force of inner columns are analyzed. The analysis results of different approaches are used to evaluate the advantages, limitations, and ease of application of each approach for seismic analysis.

Comprehensive seismic hazard assessment of Tripura and Mizoram states

Northeast India is one of the most highly seismically active regions in the world with more than seven earthquakes on an average per year of magnitude 5.0 and above. Reliable seismic hazard assessment could provide the necessary design inputs for earthquake resistant design of structures in this region. In this study, deterministic as well as probabilistic methods have been attempted for seismic hazard assessment of Tripura and Mizoram states at bedrock level condition. An updated earthquake catalogue was collected from various national and international seismological agencies for the period from 1731 to 2011. The homogenization, declustering and data completeness analysis of events have been carried out before hazard evaluation. Seismicity parameters have been estimated using G–R relationship for each source zone. Based on the seismicity, tectonic features and fault rupture mechanism, this region was divided into six major subzones. Region specific correlations were used for magnitude conversion for homogenization of earthquake size. Ground motion equations (Atkinson and Boore 2003; Gupta 2010) were validated with the observed PGA (peak ground acceleration) values before use in the hazard evaluation. In this study, the hazard is estimated using linear sources, identified in and around the study area. Results are presented in the form of PGA using both DSHA (deterministic seismic hazard analysis) and PSHA (probabilistic seismic hazard analysis) with 2 and 10% probability of exceedance in 50 years, and spectral acceleration (T = 0. 2 s, 1.0 s) for both the states (2% probability of exceedance in 50 years). The results are important to provide inputs for planning risk reduction strategies, for developing risk acceptance criteria and financial analysis for possible damages in the study area with a comprehensive analysis and higher resolution hazard mapping.

Extreme response of reinforced concrete buildings through fiber force-based finite element analysis

Recent events showed that buildings designed according to conventional codes are not necessarily able to resist man-made extreme events such as impact or explosions. In the past, safety against disproportionate collapse of key elements has been increased by non-structural protective measures such as barriers, sacrificial elements and limitation or control of public access. Codified procedures emerged in the last decade asking for resistant structural design methodologies to inhibit failure incidents acting on structural components performance.This paper presents an open access procedure using a fiber-based model in order to reproduce the progressive collapse of reinforced concrete (RC) buildings subjected to blast loading in an urban environment that leads to the loss of one or more bearing elements. Member removal in this fashion represents an event that happens when extreme situations or abnormal loads destroy the member itself. Two- and three-dimensional models of frame structures have been created and compared using three different numerical tools: an open source program such as OpenSees and two different commercial codes, SeismoStruct and Ls-Dyna. The first two are more classical fiber-based software, while the last one is a well-established general purpose finite element (FE) package. Removal of critical elements is assumed to occur in the building studied and a special purpose routine has been developed, within OpenSees and SeismoStruct, to create a fiber model capable of simulating overall structural response due to their failure. In this computational routine, one or more vertical members are instantaneously removed from the model and the ability of the building to successfully absorb member loss is investigated. The results obtained have been compared and validated by using the transient dynamic FE program Ls-Dyna.The numerical and modeling outcome of this research on progressive collapse behavior of RC buildings may be immediately applied to the design, vulnerability assessment and strengthening of different structural typologies ranging from residential frames to strategic and military facilities.

Interaction Mechanism between Two Large Rock Caverns

Long-term stability of geotechnical structures is critical to any engineering design. Design of underground structures is initially planned using empirical approaches based on the rock mass–classification system. This design is mainly based on limited data obtained from boreholes and surface geological mapping. However, this design needs to be continuously updated based on the information gathered as the excavation work progresses. Over the last few years, geotechnical monitoring has emerged as a major engineering tool for engineers to review and update their existing design configuration based on the actual behavior of excavated rock mass. This paper presents a case study of the interaction of two large unlined rock caverns that were excavated using a drill-and-blast technique with a heading-down benching approach. The mechanical response of the two caverns was numerically modeled and studied in terms of the stress-deformation behavior of the excavated caverns and rock support installed, taking into account the actual sequence of heading and benching followed during parallel excavation activity at one of the construction sites. It was observed from the analysis that the crown/wall junction is sensitive to displacements under both good and fair rock-mass conditions. Limited comparative study was also carried out between the measured and calculated displacements; this showed encouraging results. Progressive buildup of forces in the rock bolts and development of the stresses in pillars were also studied as part of the interaction response of two caverns.

Influence of high strain-rates on the dynamic flexural material properties of spruce–pine–fir wood studs

The influence of high strain-rate loading on the flexural response of typical light-frame wood construction has been investigated. A total of 30 stud grade 38 mm × 140 mm × 2440 mm (2″ × 6″ × 8′) spruce–pine–fir (S–P–F) lumber specimens were tested within a range of low and high strain-rates between 6 × 10−6 s−1 and 0.4 s−1. A single-degree-of-freedom iterative solution procedure was used to compute the high strain-rate modulus of rupture (MOR) and modulus of elasticity (MOE). The MOR was statistically enhanced by high strain-rates, while the MOE and strain at rupture were not. Since equilibrium of the dynamic stress–strain relationship requires that one or both of the MOE and strain at rupture must be sensitive to strain-rate effects, the lack of observed rate enhancement on these material properties was attributed to large scatter within a small sample set. Based on the results, material dynamic increase factors and a stress–strain relationship suitable for blast resistant design of timber structures were also proposed.

Monitoring Instrumentation in Underground Structures

Nowadays underground structures are very important. Based on observations of engineering; properties during geotechnical construction are an integral part of the design of underground structures. This research presents instrumentation as a tool to assist with these measurement observations, determine the need for modifications to loading or support arrangement. Also apart from above construction control, instrumentation is also indispensable for site investigation, design verification and safety of the structure. Instrumentation used in the construction of tunnels and subways can be implemented in three stagesbefore, during operation and during operation are examined. Metro Railway Tunnels are constructed in populated area and have a more comprehensive instrumentation and monitoring program that additionally includes monitoring of ground conditions, underground water levels, tilt and settlement of nearby buildings or other structures of interest in the vicinity of the tunnel alignment. Instrumentation monitoring for metro railway tunnels includes monitoring of the structures under construction together with the ground, buildings and other facilities within the predicted zone of influence. Furthermore, instrumentation and subway tunnels in and around them increase accuracy of the different layers of the earth and excavation of the surrounding structures and make safety and accuracy. This paper presents the features of sophisticated instrumentation available today for geotechnical monitoring. A wide range of sophistic have been described with their applications ted electronic and mechanical instrumentation with different instrumentation schemes used to meet the requirements of different types of structures.

Dynamic Site Characterization and Correlation of Shear Wave Velocity with Standard Penetration Test ‘N’ Values for the City of Agartala, Tripura State, India

Seismic site characterization is the basic requirement for seismic microzonation and site response studies of an area. Site characterization helps to gauge the average dynamic properties of soil deposits and thus helps to evaluate the surface level response. This paper presents a seismic site characterization of Agartala city, the capital of Tripura state, in the northeast of India. Seismically, Agartala city is situated in the Bengal Basin zone which is classified as a highly active seismic zone, assigned by Indian seismic code BIS-1893, Indian Standard Criteria for Earthquake Resistant Design of Structures, Part-1 General Provisions and Buildings. According to the Bureau of Indian Standards, New Delhi (2002), it is the highest seismic level (zone-V) in the country. The city is very close to the Sylhet fault (Bangladesh) where two major earthquakes (M w > 7) have occurred in the past and affected severely this city and the whole of northeast India. In order to perform site response evaluation, a series of geophysical tests at 27 locations were conducted using the multichannel analysis of surface waves (MASW) technique, which is an advanced method for obtaining shear wave velocity (V s) profiles from in situ measurements. Similarly, standard penetration test (SPT-N) bore log data sets have been obtained from the Urban Development Department, Govt. of Tripura. In the collected data sets, out of 50 bore logs, 27 were selected which are close to the MASW test locations and used for further study. Both the data sets (V s profiles with depth and SPT-N bore log profiles) have been used to calculate the average shear wave velocity (V s30) and average SPT-N values for the upper 30 m depth of the subsurface soil profiles. These were used for site classification of the study area recommended by the National Earthquake Hazard Reduction Program (NEHRP) manual. The average V s30 and SPT-N classified the study area as seismic site class D and E categories, indicating that the city is susceptible to site effects and liquefaction. Further, the different data set combinations between V s and SPT-N (corrected and uncorrected) values have been used to develop site-specific correlation equations by statistical regression, as ‘V s’ is a function of SPT-N value (corrected and uncorrected), considered with or without depth. However, after considering the data set pairs, a probabilistic approach has also been presented to develop a correlation using a quantile–quantile (Q–Q) plot. A comparison has also been made with the well known published correlations (for all soils) available in the literature. The present correlations closely agree with the other equations, but, comparatively, the correlation of shear wave velocity with the variation of depth and uncorrected SPT-N values provides a more suitable predicting model. Also the Q–Q plot agrees with all the other equations. In the absence of in situ measurements, the present correlations could be used to measure V s profiles of the study area for site response studies.

주방식 지하공간의 구조적 안정성 평가개념 정립에 관한 연구

본 연구에서는 주방식 지하구조물의 안정성 검토방안을 마련하기 위해 암주와 천장부의 거동을 수치해석 방법으로 검토하였다. 또한, 기존 자원개발 분야에서 고려하는 주방식 공법의 설계 개념과는 달라져야 하는, 공간 확보차원에서의 합리적인 주방식 공법의 설계 절차 및 개념을 제시하였다. 주어진 지반 조건에서 암주의 형상비와 천장부의 길이에 따른 수치해석을 수행하였으며 초기 이완이 시작되는 시점에서의 파괴유형과 위치 변화를 검토하였다. 해석결과, 천장부 폭과 암주 폭과의 비(w/s)와 파괴시점의 상재하중간의 관계는 선형관계를 보였으며, 천장부 폭과 암주 폭의 비가 주방식 채광 설계에서는 매우 중요한 설계인자로 다루어지는 암주의 폭과 높이 비(w/H)보다 구조물의 안정성 확보차원에서는 더욱 민감한 설계인자인 것으로 나타났다. 이는, 암주의 안정성 만을 확보하는 차원에서 수행되는 주방식 채광 설계법과는 달리, 암주부와 함께 구조물 천장부 및 어깨부의 안정성까지도 함께 고려하여 지하구조물의 안정성을 확보할 수 있는 구조물 설계가 되어야 함을 의미한다. 또한, 지하구조물의 형상에 따라 초기 이완대가 발생하는 위치와 전단 또는 인장파괴 등 파괴유형도 다르게 나타나, 주방식 지하구조물에 대한 설계는 상재하중에 따른 천장부와 암주의 안정성을 연계하여 수행하는 것이 필요하다. In this study, in order to evaluate stability of the room-and-pillar underground structure, a series of preliminary numerical analyses were performed. Design concept and procedure of an underground structure for obtaining a space are proposed, which should be different from structural design for the room-and-pillar in mine. With assumed material properties, a series of numerical analyses were performed by varying size ratios of room and pillar and then the failure modes and location at yielding initiation were investigated. From the results, relationship between the ratio of pillar width to the roof span (w/s) and overburden pressure at failure initiation shows a relatively linear relation, and the effect of w/s on structural stability is much more critical than the ratio of pillar width and height (w/H) which is a crucial parameter in design of the room-and-pillar mining. It means that roof tensile failure and shear failure at shoulder and pillar are necessary to be considered together for confirming overall structural stability of the room-and-pillar structure, rather than considering the pillar stability only in mining. Failure modes and location at failure initiation were varied with respect to the ratio of room and pillar widths. Therefore, it is necessary to simultaneously consider stability of both roof span and pillar for design of underground structure by the room-and-pillar method.

In-structure shock of underground structures: A revisit with experimental investigation

In-structure shock of underground structures subjected to ground shocks is investigated, both theoretically and experimentally. In the theoretical prediction, the ground shock is simplified to a triangular pulse with a rise time. It is found that the acceleration time history of the structure when the rise time of the ground shock is considered is significantly different from that when it is neglected. A small scale test is designed and conducted to validate the theoretical prediction. The comparison of the measured and predicted acceleration time histories suggests that the theoretical prediction with ground shock rise time considered is more reasonable. Further, shock response spectra for the equipment attached to the underground structure are established and a case study indicates that in-structure shock level of the devices predicted by the model with ground shock rise time is higher than that predicted without consideration of the ground shock rise time. It is shown that the present assessment of in-structure shock is reasonably accurate and it can be used for a preliminary design of underground structures where in-structure shock is concerned.

Performance and protection approach of single-layer reticulated dome subjected to blast loading

The elaborate finite element model of Kiewitt-8 single-layer reticulated dome with span of 40m subjected to eccentric blast loading was established and all the process from the detonation of the explosive charge to the demolition of reticulated dome structure was reproduced. The blast performance of reticulated dome was numerically studied and two approaches to improve the blast resistant capacity of reticulated dome were discussed. Response types of reticulated dome under eccentric blast loadings were defined. Partially reinforcement of reticulated dome is found to be an effective and economical way to improve its blast resistant capacity compared with fully reinforced reticulated dome. The pre-designed openings on the wall to release blast loading were studied, which provided some guidance on the blast resistant design of such structures.

Seismic microzonation of Chania, Crete (Greece) based on SASW measurements and non-linear site response analyses

Following a brief overview of past applications of, and more recent advances on seismic microzonation, the results of a seismic microzonation study for the city of Chania, Greece, are presented. The study was based on Vs vs. depth profiles obtained at 19 sites of the urban area by performing SASW measurements. The spatial distribution of Vs values was utilized in estimating Vs30 values, depth to bedrock and the fundamental ground period variation across the area of the city as well as for conducting 1-D finite element non-linear inelastic site response analyses. The input earthquake excitations employed in the response analyses were based on the results of an available seismic hazard study for the Chania Area. The results of analyses were utilized for establishing the spatial distribution of rock motion amplification, the expected ground motions and spectral values in the area of the city. Contour maps providing values of the expected ground motion in the urban area are given which may become a practical tool in assessing the seismic risk and expected damage in the Chania area. The maps can also be used in the design of new earthquake resistant structures or the seismic retrofitting of existing ones. Finally, the results were utilized to demonstrate the inadequacy of using Vs,30 values for classifying the soil conditions in the Chania area.

Analysis of Mechanics Characteristics of Prestressed Steel Column in High Temperature (Fire) Condition

According to the requirements of fire scientific theory and the fire resistance design of structures, and combined with the practical engineering and based on the building damage situations that may occur, this paper analyzes the characteristics of mechanical behavior of prestressed steel column in high temperature condition (fire). It puts forward that how to consider the effects of high temperature parameters and prestressed loss on the structural bearing capacity in prestressing steel column design, and may provide reference values for the fire resistance design of steel structures.

Elaborate Failure Model and Seismic Response Analysis for Multi-Story Masonry Building with R. C. Frames on Ground Floor

Framed-Ground Floor Structure for short which has serious seismic damage and high collapsed rate, is the unreasonable structure system. The experiences is 1. The shear wall can be increased to improve stiffness of weak layer. And designer should try to arrange the walls equably. 2. In order to avoid stiffness mutation, stiffness ratio between ground frame and transition layer can be adjusted. 3. Collapse resistant design of Framed-Ground Floor Structures should be emphasized. Then seismic response analysis is conducted by ANSYS. And the seismic response is little, and strength damage or stable damage do not occur for the little acceleration peak. Along with the increasing acceleration peak, The bigger horizontal displacement leads to damage of Framed-Ground Floor Structures. Moreover, the damage is in advance as the increasing acceleration peak.

Investigation of Wave Field Stress Method in Seismic Analysis of Underground Structures

It is indicated by many earthquake damage surveys that the seismic design of underground structures is a key issue for underground caverns. However, methods regarding seismic design of underground caverns have not been covered by current national codes. The wave field stress method is a kind of method in which the additional stress induced by earthquake is calculated based on the dynamic features of structures. Based on the earthquake damage survey of the underground cavern at Yingxiuwan hydropower plant after Wenchuan earthquake, the wave field method is used to analyze the structural response under earthquake impact. After comparing calcluation results to field findings, it is discovered that they are basically in good agreement. Therefore, it is concluded that the wave filed stress method can be adopted to assist the seismic design of underground structures during the preliminary design phase of project.

Statistical characteristics of sustained wind environment for a long-span bridge based on long-term field measurement data

The fluctuating wind induced vibration is one of the most important factors which has been taken into account in the design of long-span bridge due to the low stiffness and low natural frequency. Field measurement characteristics of sustained wind on structure site can provide accurate wind load parameters for wind field simulation and structural wind resistance design. As a suspension bridge with 1490 m main span, the Runyang Suspension Bridge (RSB) has high sensitivity to fluctuating wind. The simultaneous and continuously wind environment field measurement both in mid-span and on tower top is executed from 2005 up to now by the structural health monitoring system installed on this bridge. Based on the recorded data, the wind characteristic parameters, including mean wind speed, wind direction, the turbulence intensity, the gust factors, the turbulence integral length, power spectrum and spatial correlation, are analyzed in detail and the coherence functions of those parameters are evaluated using statistical method in this paper. The results indicate that, the turbulence component of sustain wind is larger than extremely strong winds although its mean wind speed is smaller; the correlation between turbulence parameters is obvious; the power spectrum is special and not accord with the Simiu spectrum and von Karman spectrum. Results obtained in this study can be used to evaluate the long term reliability of the Runyang Suspension Bridge and provide reference values for wind resistant design of other structures in this region.

Simulation of strong ground motion due to great earthquake in the central seismic gap region of Uttarakhand Himalaya

Uttarakhand Himalaya in India lies in the central seismic gap region identified by Khattri and Tyagi (Tectonophysics 96:281–297, 1983). Most of the area in Uttarakhand state has been placed under zone V (the highest seismic zone) and zone IV (second highest seismic zone) of the seismic hazard map published by Bureau of Indian standard, Govt. of India (BIS in Indian standards code of practice for earthquake resistant Design of Structures, Indian Standards Institution, New Delhi, 2002). Some of the thrust/faults in the region manifest evidence of neotectonics and recurrent seismicity (Valdiya and Pant in Indian Nat Sci Acad 112–117, 1986; Valdiya in Geodynamics of NW Himalaya Gondwana Research Group Memoir 1999; Thakur in Curr Sci 86(II):1544–1560, 2004; Paul et al. in Seismotectonic implications of data recorded by DTSN in the Kumaon region of Himalaya 2004). On the basis of strain accumulation, Bilham et al. (Science 293:1442–1444, 2001) suggested a future magnitude of M ≥ 8 in this region. Therefore, a great earthquake along main central thrust in the central seismic gap region has been modeled using semi-empirical technique of Joshi and Mohan (J Seismol 12:35–51, 2008). For modeling great earthquake, the shear wave quality factor \( Q_{\beta } \left( f \right) = 30f^{1.45} \) (Joshi et al. in J Earthq Technol 47(1):508, 2010) has been used for Pithoragarh region of Kumaon Himalaya. The strong-motion parameters [peak ground acceleration (PGA), spectral acceleration, and normalized spectral acceleration] are computed at five stations (Sobla, Didihat, Munsiari, Dharchula, and Pithoragarh) in Uttarakhand Himalaya. The maximum PGA of the order of “2g” is computed due to scenario great earthquake in the region at Sobla station. Such type of study is quite helpful for seismic-resistant designs of the buildings in earthquake-prone areas and is essentially required in Uttarakhand Himalaya.

Investigation of Soil Arching with Centrifuge Tests

AbstractThe classic experiment of a yielding trapdoor in (two-dimensional) plane strain beneath a granular mass is revisited, this time in the high-gravity environment of a geotechnical centrifuge. High-speed acquisition of load and displacement data makes it possible to examine the arching behavior of geomaterials. Results indicate the formation above the trapdoor of a physical arch, which evolves from an initially curved configuration to a triangular shape and ultimately to a prismatic sliding mass with vertical sides. Simple expressions for the reduced load caused by arching are proposed. Predictions using these expressions compare favorably with test measurements, paving the way for potential application to the design of underground structures.

Seismic analysis of the rock mass classification in the Q-system

Empirical, numerical and analytical methods are regarded as different tools for design of tunnel. Empirical methods have been established based on the experience resulted from different projects. Based on the recorded information, underground structures enjoy a higher level of safety against dynamic waves compared to surface structures. Previously, the seismic design of underground structures has received less attention than that of surface structures, while designing underground structures without considering seismic loads would result in an unsafe structure. In rock mass classification, despite considering various parameters for designing underground structures, the seismic parameter has been disregarded or has been expressed in a very general manner. Taking into account the seismic effect in rock mass classification is a relatively new topic which has been addressed in this paper. Moreover, it has been attempted to investigate the seismic effect in the Q-system using numerical analysis. The results obtained from numerical simulations are compared and counterbalanced with the results of Q-system. After comparing and analyzing the results, a relationship has been proposed for the effects of seismic behavior in Q-system. The solved examples give reasonable and acceptable results.

Performance of N-Z systems in the mitigation of underground blast induced vibration of structures

Control of structural vibration due to wind and earthquake forces has been extensively researched. However, studies on vibration control of structures against underground blasts are limited. It is thereby important to study the usefulness of established vibration control technologies in the blast resistant design of structures. In the present work, an attempt is made to study the effectiveness of the New-Zealand (N-Z) type base isolator (BI) in mitigating structural vibration effects due to blast induced ground motion (BIGM). The BIGM is modeled by an exponentially decaying function representative of a typical rock blast, and the isolator by a bilinear model. The influence of the various BI parameters on its performance is examined in the time domain by considering a single-degree-of-freedom structural model and a realistic five-story building. Numerical studies reveal that the N-Z base isolation system is highly effective in reducing both the underground blast induced structural acceleration as well as the displacement. It is noted that the peak displacement and permanent deformation of the BI may be crucial design criteria. These may, however, be restricted by selecting a proper combination of the BI parameters without significantly compromising the response reductions obtained by it.

Strong motion simulation at Abu Zenima city, Gulf of Suez, Egypt

Earthquake hazard assessments are an important task for the design of earthquake resistant structures and insurance industry. Such assessments get more importance when the site of interest is located near an active earthquake zone. Such situation is present for the location of Abu Zenima city. The city is characterized by the presence of industrial and Maritime platform in addition to other Oil production facilities. These industrial facilities motivated the present work.The simulated earthquake ground motion time histories are conducted using stochastic technique. The magnitude used for simulation is obtained using both probabilistic and deterministic approaches. An analysis using both approaches shows that moderate earthquakes in the vicinity of the site could have the largest effects on the area. Thus an earthquake of magnitude 4.5 at a distance of 21km is chosen as design earthquake.The simulated ground motions are presented in terms of acceleration, velocity, and displacement time histories. In addition the response spectra are also presented that may be used for engineering purposes.