Bauzeit und Baukosten für Stahlbetonarbeiten – Berechnungsmethoden und Anwendung

Construction Time and Cost of Reinforced Concrete Works – Calculation Methods and Application Construction time is of crucial importance when it comes to utilizing the production factors in an effective and efficient way. Construction periods that are too short usually result in higher cost, poorer quality and a larger number of disputes. This paper sets out to demonstrate the calculation of construction time whilst considering key construction management parameters. Beyond a simple, deterministic method, other options for calculation are shown that rely on probability calculus. The approaches described to determine construction time and cost are illustrated by a building project example. The deterministic method results in one value per each calculation process (calculation mode 1). In calculation mode 2, probability calculus is applied in a simple fashion. Both range and probability of occurrence can be considered for the relevant input variables. For the third calculation mode, the Monte‐Carlo method is applied using the @RISK software. For each of the parameters to be determined, this method shows a probability distribution.     

Bahnsteigerweiterung der U6 unter dem neuen Rathaus in München – Spritzbetonvortrieb mit Vereisung

Platform extension of the subway U6 below the historical town hall in Munich – shotcrete method combined with ground freezing. The construction of the new football stadium in Munich‐Fröttmaning made it necessary to extend the platform of the subway station U6 “Marienplatz” below the historical town hall of Munich. For this, two new tunnels for pedestrians were driven parallel to the existing subway tunnels. They were planned as shotcrete construction and driven under atmospheric conditions. The tunnels have a vertical distance of approx. 10 m to the foundation of the town hall. Artificial ground freezing was used to guarantee the stability and safety of the tunnel roof and to reduce the deformations. The freezing pipes were implemented in a smaller pilot tube lateral above the tunnels. Both the magnitude of the frost heave displacements and the settlements had to be predicted prior to undertake the construction. Therefore frost heave tests and FE‐computations were carried out. During the construction process these results were permanently compared to measurements in order to control and ensure tolerable deformations. In the following contribution the substantial computations and results of measurement relating to the ground deformations and to the lowering of groundwater are described. Furthermore the methods for the reduction of the frost heave are explained. A comparison of the methods of construction and calculation of the old tunnels and the new tunnels illustrates the developments in tunnel construction resulting from the shotcrete method.     

Simplified analysis of asymmetric high‐rise structures with cores

A simplified elastic hand‐method of analysis for asymmetric multi‐bent structures with cores subjected to horizontal loading is presented. The structures may consist of combinations of framed structures such as coupled walls, rigid frames and braced frames with planar and non‐planar shear walls. Results for structures that are uniform with height compare closely with results from stiffness matrix analyses. The method is developed from coupled‐wall deflection theory which is expressed in non‐dimensional structural parameters. It accounts for bending deformations in all individual members, axial deformations in the vertical members as well as torsion and warping in nonplanar walls. A closed solution of coupled differential equations for deflection and rotation gives the deflected shape along the height of the building from which all internal forces can be obtained. The proposed method of analysis offers a relatively simple and rapid means of comparing the deformations and internal forces of different stability systems for a proposed tall building in the preliminary stages of the design. The derivation of equations for analysis shown in this paper are for unisymmetric stability systems only, but the method is also applicable to general asymmetric structures with cores. Copyright © 2002 John Wiley & Sons, Ltd.     

An elastic stress–displacement solution for a lined tunnel at great depth

By using the complex potential theory proposed by Muskhelishvili, an elastic plane strain solution for stresses and displacements around a lined tunnel under in situ stresses is presented. The tunnel is assumed to be driven in a homogeneous and isotropic geomaterial, and the tunnel construction sequence is properly taken into consideration. Numerical analyses indicate that, in order to simultaneously meet the needs of structural strength and rigidity, the relative rigidity and thickness of liner should be in an appropriate range. Either too high or low values for these parameters are unfavorable for the structural stability. The variations of stresses in the geomaterial intensively rely on the relative rigidity and thickness of liner when the ratio between the distance of the point under investigation to the tunnel axis and the outer radius of the liner is in the range from 1 to 2. In addition, the present solutions contain previously known results as the special cases.     

Methodology for tunnel and portal support design in mixed limestone, schist and phyllite conditions: a case study in Turkey

The purpose of this study is to present a methodology for tunnel and support design in mixed limestone, schist and phyllite conditions through investigating two highway tunnel case studies that are located along the Antalya–Alanya Highway in southern Turkey. The main lithologies of the project area are regularly jointed, recrystallized limestone and the weak lithologies of the schist unit (i.e., pelitic schist, calc schist, graphitic phyllite and alternations of these lithologies). A detailed geological and geotechnical study was carried out in the project area, and the tunnel ground support types and categories were determined according to the Q-system, rock mass rating method and New Austrian Tunneling Method (NATM). The shear strength parameters and geomechanical properties of the rock masses were obtained by using the geological strength index (GSI). The deformation moduli and post-failure behavior of the rock masses have been determined. Slope stability analyses were performed at the portal, side or cut slope sections. Kinematic and limit equilibrium analyses incorporating the effects of water pressure were performed for the regularly jointed failed rock slopes. Circular failure analogy was used for the slope stability analyses of irregularly jointed, highly foliated lithologies. Slope support system recommendations were made. A back analysis on a failed slope was performed. The results of the back analysis compared well with the results obtained through the GSI method. The tunnel grounds were divided into sections according to their rock mass classes. The deformations and stress concentrations around each tunnel section were investigated and the interactions of the empirical support systems with the rock masses were analyzed by using the Phase² finite element software. The regularly jointed rock masses were modeled to be anisotropic and the irregularly jointed, highly foliated and very deformable soil-like lithologies were modeled to be isotropic in the tunnel finite element analyses.     

Zur Anwendung der Finite‐Elemente‐Methode bei Baugrubenwänden

Application of the Finite Element Method in design of excavation walls. During the last years the Finite Element Method (FEM) became a standard tool for geotechnical engineers. The FEM is above all suited to predict deformations in serviceability states on the basis of characteristic soil parameters. With the same calculation as for serviceability states the characteristic loads and effects for ultimate limit states can be determined. As can be shown the FEM comes to limitations when calculating resistances in connection with procedure 2, which is for ultimate limit state design obligatory according to German standards and codes. Therefore in most cases the classical design is more convenient.     

Appraising the methods accounting for 3D tunnelling effects in 2D plane strain FE analysis

Numerical analysis is widely used method in geotechnical engineering when calculating and predicting soil and rock behaviour under different loading and excavation conditions. For instance, simulation of tunnelling using 2D or 3D finite element (FE) analyses can often calculate any deformations and stress redistributions due to tunnelling operations without constructing real trial tunnels. Modelling the excavation process in 2D plane strain analysis, however, requires an approach that can consider 3D tunnelling effect as a result of volume loss. In addition, modelling shotcrete or similar support measures, using either beam elements, solid continuum elements or other special elements are needed to be adopted. Therefore, convergence-confinement, stiffness reduction, disk calculation and hypothetical modulus of elasticity (HME) soft lining approaches have been employed in the numerical analysis. Moreover, compatibility of each method with beam and solid continuum element models in 2D FE analysis was investigated. Thus, eight plane strain, non-linear FE analyses of tunnel construction in London Clay were performed and the results are presented and discussed in this article.     

Time‐dependent analysis of steel‐reinforced concrete structures

The time‐dependent behavior is a major consideration in the design and construction of tall buildings, especially in concrete and composite structural systems. To make an analysis of long‐term effect of steel‐reinforced concrete structures, the method of using master–slave constraint to deduce substructure element model of composite members was introduced, and the problem of co‐work between steel and concrete was solved. The creep calculation method of combined Age‐adjusted Effective Modulus Method (AEMM) and finite element method was adopted. Steel Reinforced Concrete Construction Modeling (SRCCM), a calculation program based on Visual C++ and ObjectARX, was developed for simulating the construction process of high‐rise composite structures. The use of the method is illustrated through one computation example of Shanghai Center Tower, which is a super high‐rise steel‐reinforced concrete structures. The method provides valuable information about time effects that may be used in designing new structures or in diagnosis existing structures. The results also indicate that the vertical shortening of Shanghai Center Tower between column and core‐tube is significant. Such differential length changes should be compensated during the construction process of high‐rise composite structures. Copyright © 2013 John Wiley & Sons, Ltd.     

Approximate analysis of high‐rise frames with flexible connections

An approximate hand method for estimating horizontal deflections in high‐rise steel frames with flexible beam–column connections subjected to horizontal loading is presented. The method is developed from the continuous medium theory for coupled walls which is expressed in non‐dimensional structural parameters. It accounts for bending deformations in all individual members as well as axial deformations in the vertical members and is more accurate for very tall structures. Additional deformations in the beam–column connections contributing to the overall frame deformations are also included in the analysis. This reduction in the frame stiffness requires the non‐dimensional structural parameters to be modified. A closed solution of the differential equation for the cantilevered structure yields a rapid assessment of the influence of different types of connection on the overall behaviour. Results for structures that are uniform with height compare closely with results from stiffness matrix analyses. Copyright © 2000 John Wiley & Sons, Ltd.     

Effects of different tunnel face advance excavation on the settlement by FEM

The excavation process for a tunnel changes in terms of its service requirements, ground conditions and the stability of surface buildings in urban areas. When a tunnel is excavated, there will be settlement, which may cause damage to surface structures. To control and limit the settlement caused by tunnelling operations, there have been many tunnelling techniques proposed. Thus, in this paper, a number of Finite Element Method analyses were conducted to investigate the effects of different patterns for advancing the tunnel face on the settlement. The Heathrow Express Trial tunnel was constructed in accordance with the principles of the New Austrian Tunnelling Method (NATM). The settlement measurements taken during its construction were used to validate the results from the analyses undertaken. Three different face advance techniques were used during the construction of the Heathrow Express Trial tunnel viz. Twin sidewall excavation (TS1), single sidewall excavation (TS2), and Crown, Bench and Invert excavation (TS3). As the trial work proved that TS2 produced the minimum settlement above tunnel centreline, only TS2 was subjected to the FEM analysis in this research. In order to simulate TS2 correctly three types of excavation models were devised and the results compared to field measurements of TS2. For the FEM analysis the Hypothetical Modulus of Elasticity (HME) soft lining approach was used and a practical method to estimate HME is proposed for when it is used for different face advance sequences. Results proved that when the excavation pattern was changed, the HME value was also changed and settlement over the tunnel centreline changed in terms of the face advance pattern adopted.     

Evaluation of behavior factor of tunnel‐form concrete building structures using Applied Technology Council 63 methodology

Tunnel‐form construction system is used for buildings made up of slabs and walls. This system has represented fast construction technique, low cost and time saving in the construction period. However, there are no special requirements for seismic design of this type of buildings, and some provisions of the concrete bearing wall system are used. None of the seismic codes addresses the R factor for tunnel‐form buildings directly, and some doubts remained about prediction of the fundamental period. Meanwhile the force‐based methods, which depended on R factor and fundamental period, are still used for seismic design of this type of buildings. There is a need for evaluating the R factor for tunnel‐form buildings. The methodology was developed by the Applied Technology Council (ATC) entitled ATC‐63 Project for quantifying building system performance and response parameters for use in seismic design. Here, this methodology is used to estimate more reliable R factor for tunnel‐form buildings. An experimental program was carried out to decrease the uncertainty of finite element modeling and using it as a part of the methodology. A database was created, and some analyses were performed. The results of analysis were summarized to propose more accurate R factor for tunnel‐form buildings. Copyright © 2011 John Wiley & Sons, Ltd.     

基于差异进化算法反演参数的隧道稳定性分析

在隧道和地下工程弹性问题的位移反分析中,当基本未知数多于三个时,在各参数可能的变化范围内找到一组使误差最小的最佳参数的优化反分析方法是当前岩土工程反分析研究的热点问题。论文结合一种新型的优化算法(差异进化算法),依托摩天岭1＃斜井隧道工程施工,跟踪施工进行了典型断面围岩位移监测,以现场量测位移作为基础信息求得了斜井隧道全局最优值的最佳力学参数组合。根据以上采用差异进化算法求得的反演参数,对摩天岭1#斜井隧道单层衬砌支护稳定性进行了三维数值模拟分析,分析表明,摩天岭1#斜井隧道III级围岩段喷15 cm厚钢纤维混凝土支护后,斜井隧道围岩最小应力明显降低,围岩位移明显减小,因此建议摩天岭1#斜井洞身段III级采用15 cm厚度的钢纤维喷射混凝土单层衬砌。以上研究直接指导了摩天岭隧道单层衬砌设计和施工。     

Analysis of flexural natural vibrations of thin‐walled box beams using higher order beam theory

In order to study the influence of high‐order shear deformations and shear lag on the dynamic characteristics of thin‐walled box beams (TWBBs), this paper takes the Hamilton principle as a basis to consider multiple factors such as high‐order shear deformations, shear lag, and cross section rotary inertia of the TWBBs. The vibration differential equations and natural boundary conditions of TWBBs are deduced. On the basis of eight examples of TWBBs with different boundary conditions and span–width ratios, analytical results of this paper are compared with those of the ANSYS finite element method. Both results are in good agreement with each other, and the validity of the calculation method is verified. The effects of higher order shear deformations and shear lag on natural vibration characteristics of TWBBs are analyzed. And some meaningful conclusions are drawn: This theory shows the capability to accurately describe both higher order deformations and shear lag; when the span–width ratio is small, neglecting higher order web deformations will produce a large calculation error; under the action of shear lag, the natural vibration frequency of TWBBs decreases greatly, which cannot be neglected; and both the high‐order shear deformations and shear lag effect increase with increasing mode order and increase with decreasing span–width ratio.     

Stochastic analysis for the uncertain temperature field of tunnel in cold regions

In cold regions, the temperature is important to determine the stability of tunnel construction. However, the conventional finite element methods for stability analysis are always deterministic, rather than taking stochastic parameters and conditions into account. In this paper, the boundary conditions are considered as stochastic processes and the rock properties are considered as random fields. A stochastic analysis for the uncertain temperature characteristics of tunnel is presented. The stochastic finite element formulae are obtained by Neumann stochastic finite element method (NSFEM), and the stochastic finite element program is compiled by Matrix Laboratory (MATLAB) software. Using our program, the random temperature fields of a tunnel in a cold region are obtained and analyzed. The results show that the temperature of a large quantity of frozen surrounding rock is stochastic, and it is bad for the thermal stability of actual tunnel engineering in cold regions. The distributions of mean temperature are the same and the distributions of standard deviation are similar for the two cases in this paper. The average standard deviation increases with time, which implies that the results of conventional deterministic analysis may be far from the true value. These results can improve our understanding of the random temperature field of tunnel and provide a theoretical basis for actual engineering design in cold regions.     

Geotechnical investigations and preliminary support design for the Geçilmez tunnel: A case study along the Black Sea coastal highway,Giresun, northern Turkey

This study encompasses geotechnical investigations, stability assessments and design of the preliminary support systems for the Geçilmez tunnel which is constructed in Giresun for the improvement of the highway along the Black Sea coast. During the study, a detailed geological map of the study area was prepared and the geotechnical characteristics of the rock masses were determined. The rock mass classification of the tunnel grounds was performed by utilizing the RMR method, Q system, NATM and the Geological Strength Index (GSI) classification which was followed by performing a geotechnical investigation along the tunnel grounds in order to obtain the geotechnical parameters for the stability analyses of the portals and of the tunnel. Lugeon (water pressure) tests were performed in order to determine the permeability of the rock mass along the tunnel. The appropriate geotechnical parameters were utilized in order to perform rock slope stability kinematic and limit equilibrium analyses at the portals of the tunnel. Empirical preliminary tunnel support systems according to the RMR method, Q-system and NATM were determined. The structurally controlled instabilities within the tunnel sections were identified and the required preliminary tunnel support systems were determined to overcome these instabilities. Regarding the structurally controlled rock failures along the probable weak zones and lineaments (i.e., inactive probable faults or shear zones) during tunneling, wedge stability analysis was utilized to determine the potential wedge failures that could possibly occur during tunneling and to apply the necessary support systems for stabilizing any wedge failure in the tunnel. The induced stress distributions and deformations in the rock mass surrounding the tunnel grounds was investigated and the interaction of the support systems with the rock mass was analyzed by using numerical (finite element) modeling. In the finite element analyses it was assumed that the rock mass behaved as a fractured rock mass since the tunnel grounds were moderate to highly jointed. The objective of the numerical modeling was to check the validity of the empirical preliminary tunnel support requirements and also to compare the results with those obtained through assuming structurally controlled failures during tunneling. The performance of the preliminary tunnel support was also validated on the basis of thrust–moment interaction analyses. The results of the structurally controlled failure analyses, numerical analyses and thrust–moment analyses were compared in an attempt to determine the preliminary tunnel support systems to stabilize the Geçilmez tunnel.     

浅埋偏压小净距隧道围岩压力分布与围岩控制

根据浅埋偏压小净距隧道受力特点,研究推导了考虑施工工序及地形坡度的浅埋偏压小净距隧道围岩压力计算公式。分析了考虑不同地形坡度及同一坡度不同埋深2种工况下地形坡度及埋深对围岩破裂范围、水平侧应力、拱顶压力的影响规律,并指出了浅埋偏压小净距隧道围岩压力在考虑地形坡度下与水平地表下分布规律的差异,建立了3DEC数值模型以对上述理论规律进行验证,结果表明,数值分析规律与理论推导计算规律相吻合。将理论计算公式应用于马嘴隧道出口浅埋段隧道稳定性计算,由计算所得围岩稳定性系数及现场隧道变形监测结果提出隧道围岩及地表稳定性处理措施。     

Erfahrungen mit dem Spannungs‐Verformungsverhalten von mit Geogittern bewehrten Stützkonstruktionen

Experiences with the tension deformation behaviour of retaining structures reinforced with geosynthetics. Since several decades the application of geosynthetic‐reinforced earth bodies successfully worked. The establishment of the retaining structures on strongly changing or small load‐carrying underground, with high live loads or large construction heights proved itself often as extremely economic and ecological alternative to classical building methods. In order to gain experiences with a new building method, frequently the so‐called observation method is used, which means the stress‐deformation behaviour becomes both while the construction and the first utilization phase of the building is determined by measuring techniques. From these results of measurement it becomes clear that also when high loaded the total deformations of the constructions are smaller than expected. From all the measured results the deformations of the geosynthetics are smaller than the analyzed values. The concept for the estimation of the deformations, used at present, seems far thereby from the actual behaviour of such constructions. The experiences of completed structures are presented and the results are discussed.     

ResCol‐Versuche zur Prüfung der dynamischen Langzeitstabilität von TA/TM‐Böden unter Eisenbahnverkehr

Application of resonant column tests for the investigation of the dynamic long‐term stability of clays under railway traffic. Some resonant column tests have been done on the clays, which were taken from the foundation zones of open cut in the new railway line Nuremberg–Ingolstadt (under construction). From the tests, basic dynamic parameters were determined for the evaluation of dynamic long‐term stability of railway foundation by using a new approach, which has been developed by using well‐known soil dynamic knowledge. With the help of the test results, the practical controlling criteria in regard to the long‐term dynamic stability have been derived for construction site. In the paper presented, the design criterion, the test results and their application in practice are described.     

Bestimmung des Einflusses von Karststrukturen auf die dauerhafte Stand‐ und Betriebssicherheit von Verkehrstunneln durch 3D‐Finite‐Element‐Modellierung

Determination of the influence of karst structures on the servicability and stability of traffic tunnels by 3D finite element modelling. Numerous tunnels are planned and constructed in karstified rock. Control of karst and rockfall problems signifies that permanent serviceability of the structure will be ensured. Rock models and failure mechanisms are developed in a next step and the influence of karst structures on the tunnel is investigated by numerical analyses. The basis for the treatment of this problem is provided by extensive site investigations. The geological/hydrogeological documentation supports the risk assessment defining the scope of the necessary additional site investigations in a second investigation phase. The paper primarily addresses the numerical analyses undertaken to verify the stability and serviceability of the Irlahüll Tunnel of the New Nuremberg–Ingolstadt Railway Line (Deutsche Bahn). The discussion shows the usefulness and purpose of complex numerical analysis methods to realistically model the complex load‐bearing and deformation behaviour of a tunnel in karst formations and thus to elaborate both economically optimized and permanently stable solutions.     

Creep and shrinkage analysis of reinforced concrete frames by history‐adjusted and shrinkage‐adjusted elasticity moduli

Consideration of the time‐dependent deformations due to creep and shrinkage is often necessary to ensure satisfactory behavior of complex concrete structures. The stresses and deformations of a reinforced concrete frame can be analyzed by the finite element method using time integration. However, as the full stress history prior to each time interval considered is necessary, with the increase in the number of time intervals used, the amount of computations increases dramatically. The concept of age‐adjusted elasticity modulus is further explored to develop new functions for efficient evaluation of time‐dependent behavior of concrete frames. The history‐adjusted elasticity modulus is devised so that stage construction can be modeled more accurately. Likewise, the shrinkage‐adjusted elasticity modulus is introduced to enable shrinkage analysis to be carried out using one single step. The methods can cope with frame structures built and loaded in several stages. Accurate results can be obtained by considering just a few large time intervals instead of those fine time steps used in time integration. Numerical examples are presented to demonstrate the usefulness of the new methods. Copyright © 2007 John Wiley & Sons, Ltd.