The stability bracing behavior of trusses was investigated using experimental testing and computational modeling. The laboratory experiments were conducted on twin trusses fabricated with W4x13 sections for the chord and web members. Spans of 48 and 72 feet were used in the tests that included both lateral load tests and buckling tests. Most of the tests were done on the regular (Howe) truss, except the lateral stiffness tests which were also done on the inverted (Pratt) truss. Computational models were developed using the three-dimensional finite element program, ANSYS, which were validated using the laboratory test data. A variety of models were used to simulate both as-built and idealized truss models. The experiments demonstrated that the buckling capacity of the truss with torsional bracing largely depended on the brace stiffness and the number of intermediate braces. Similar behavior was observed in the truss with lateral bracing. The tests results demonstrated that cross sectional distortion dramatically reduces the effectiveness of the torsional braces. The experiments provided valuable data for validating the finite element models that were used to conduct parametric studies on torsional bracing of truss systems. The results from the parametric studies were used to develop stiffness requirements for torsional bracing of trusses. / text

In current bridge practice, all tension members in a truss bridge are identified as fracture critical members which implies that a collapse is expected to occur once a member of this type fails. However, there are several examples which show that bridges have remained standing and shown little distress even after a fracture critical member was completely damaged. Due to the high inspection cost for fracture critical members, it would be beneficial to remove fracture critical designation from some tension members. This could be achieved via considering system redundancy. Since there is no clear guidance in existing codified provisions for assessing system redundancy, this research is undertaken to develop simplified analysis techniques to evaluate system redundancy in truss bridges. The proposed system redundancy analysis in this research starts with the identification of the most critical main truss members whose failure may significantly affect the system redundancy. The system redundancy is then measured by the remaining load capacity of a damaged bridge after losing one of the critical members. The bridge load capacity is checked using 3D models with nonlinear features that can capture the progression of yielding and buckling in a bridge system. The modeling techniques are validated through the case studies of the I-35W Bridge and one test span of the Milton-Madison Bridge. Reasonable correlations are demonstrated between the models and the measured data for these two bridges both in an undamaged and in a damaged state. The feasibility of the proposed methodology for system redundancy evaluation is examined by applying the methodology blindly to two other simple truss bridges. The application shows that the proposed methodology can efficiently measure the system redundancy. To improve the system redundancy, this research also proposes sample retrofit strategies for the four example bridges. / Ph. D.

Railroad bridges are the most important connection parts of railroad networks. These bridges are exposed to heavier train loads compared to highway bridges as well as various detrimental ambient conditions during their life span. The railroad bridges in Turkey are mostly constructed during the late Ottoman and first periods of the Turkish Republic / therefore, they are generally close to about 100 years of age / their inspection and maintenance works are essential. Structural health monitoring (SHM) techniques are widely used around the world in order to increase the effectiveness of the inspection and maintenance works and also evaluate structural reliability. Application of SHM methods on railway bridges by static and dynamic measurements over short and long durations give important structural information about bridge members&rsquo / load level and overall bridge structure in terms of vibration frequencies, deflections, etc. Structural Reliability analysis provides further information about the safety of a structural system and becomes even more efficient when combined with the SHM studies. In this study, computer modeling and SHM techniques are used for identifying structural condition of a steel truss railroad bridge in Usak, Turkey, which is composed of six spans with 30 m length each. The first two spans of the bridge were rebuilt about 50 years ago, which had construction plans and are selected as pilot case for SHM and evaluation studies in this thesis. Natural frequencies are obtained by using 4 accelerometers and a dynamic data acquisition system (DAS). Furthermore, mid span vertical deflection member strains and bridge accelerations are obtained using a DAS permanently left on site and then compared with the computer model analyses results. SHM system is programmed for triggering by the rail load sensors developed at METU and an LVDT to collect mid span deflection high speed data from all sensors during train passage. The DAS is also programmed to collect slow speed data (once at every 15 minutes) for determination of average ambient conditions such as temperature and humidity and all bridge sensors during long term monitoring. Structural capacity and reliability indices for stress levels of bridge members are determined for the measured and simulated train loads to determine structural condition of bridge members and connections. Earthquake analyses and design checks for bridge members are also conducted within the scope of this study.

A three-phase numerical study was undertaken to address some design issues related with special truss moment frames (STMFs). In the first phase, the design approaches for distribution of shear strength among stories were examined. Multistory STMFs sized based on elastic and inelastic behavior were evaluated from a performance point of view. A set of time history analysis was conducted to investigate performance parameters such as the interstory drift ratio and the plastic rotation at chord member ends. The results of the analysis reveal that the maximum interstory drifts are not significantly influenced by the adopted design philosophy while considerable differences are observed for plastic rotations. In the second phase, the expected shear strength at vierendeel openings was studied through three dimensional finite element modeling. The results from finite element analysis reveal that the expected shear strength formulation presented in the AISC Seismic Provisions for Structural Steel Buildings is overly conservative. Based on the analysis results, an expected shear strength formula was developed and is presented herein. In the third phase, the effects of the load share and slenderness of X-diagonals in the special segment on the performance of the system were evaluated. Lateral drift, curvature at chord member ends, axial strain at X-diagonals and base shear were the investigated parameters obtained from a set of time history analysis. The results illustrate that as the load share of X-diagonals increases, the deformations decreases. Moreover, the slenderness of X-diagonals is not significantly effective on the system performance.

Under the direction of the Federal Highway Administration the Long Term Bridge Performance Program (LTBP) selected Minnesota Bridge number 5718 as a pilot bridge for evaluation. This program focuses on the monitoring of bridges for a 20-year period to understand the structural behavior over time due to the various loads and weathering. In monitoring this bridge a better understanding can be acquired for the maintenance issues related to the nation's deteriorating bridge infrastructure. Bridge Number 5718, which is located just outside of Sandstone Minnesota, is a steel truss bridge that spans the Kettle River. Constant monitoring of the bridge along with periodic testing of the bridge will allow for the collection of data over a 20-year period. The focus of this work is to establish a baseline for the bridges characteristics through nondestructive dynamic testing. Later tests will be compared to these results and changes can then be tracked. In order to perform the required testing, two electromagnetic shakers were used to produce the excitation. The bridge was also outfitted with an array of velocity transducers to allow for the response to be recorded. The data was then used to extract the resonant frequencies, mode shapes, and damping ratios. A modal assurance criterion was also performed to solidify the findings. These parameters define the structural identity of the bridge. Through performing these tests the database that is being collected under the Long Term Bridge Performance Program will be used to better the overall health and safety of the nation's bridges.

Baigiamajame darbe projektuojamas logistikos centras „AUTOARENA“, kuris bus statomas Išradėjų g. 6, Šiauliuose. Pastatą sudaro trys pagrindinės funkcinės zonos: garažų, sandėlio ir administracinių patalpų. Pastato bendras plotas 2135,8 m2. Pastatas priskiriamas prie ypatingos paskirties statinių. Architektūrinėje dalyje pateikti bendri statinio rodikliai, techniniai-tūriniai sprendimai bei rekomendacijos. Konstrukcinėje dalyje pateikti 4 konstrukcijų skaičiavimai pagal standartus LST bei techninius Reglamentus STR. Technologinėje dalyje pateikti medžiagų žiniaraščiai bei savaeigio krano parinkimas. Prieduose pateikta šilumos laidumo koeficientų skaičiavimas, konstrukcinės dalies skaičiavimo kompiuterine programa, „Robot Structural Analysis Professional 2011“, ataskaitos bei lokalinė objekto sąmata, kuri suskaičiuota „ProsSama5g“ programa. / In this final work designed logistic center „AUTOARENA“, which will be build in Išradėjų st. 6, Šiauliai. The building consists of 3 main function zone: garages, store and office space. The total area of building 2135,8 m2. The building is assigned to special purpose buildings group. The architectural part presents general indicators of the structure, technical-content solutions and recommendations. Structural part consist 4 structures calculations in accordance with standards LST and technical Regalement STR. The technological part to provide material sheets and self-propelled crane selection. Annexes contain heat transfer coefficient calculation, design calculation of a computer program, "Robot Structural Analysis Professional 2011, localized estimate of building which calculated with “ProsSama5g” program.

Bakalaurinio baigiamajame darbe projektuojamas vieno aukšto ypatingas statinys – logistikos centras „Logista“. Pastatas projektuojamas Šiaulių miesto pramoniniame rajone, Aerouosto gatvėje. Bendras sklypo plotas 6831,68 m2, užstatymo plotas 1539,49 m2. / In this final work is designed one-story special building – logistic centre „Logista“. Building is designed in industrail district of Šiauliai, Aerouosto street. Overall area is 6831,68 m2, built-up area 1539,49 m2.

The subject of the diploma thesis is an architectural study of a velodrome in Brno Komárov. It is an indoor cycling track which is still missing in the Czech Republic. The whole site of the Hněvkovského sports complex in Komárov was elaborated within the architectural study. The aim of the proposal was to attract a wide range of visitors to the site, so not only buildings for sports were designed. But also two sets of buildings as a modular construction from containers providing premises for rent. The construction of the velodrome was deign as a combination of monolithic reinforced concrete and steel truss structure. The cladding is design from insulated panel system.

The new built showroom and carservice, with two floors, a pent roof and an aluminium systems for facades. It is situated near the centre of Ostrava.

The thesis deals with the variant design of the steel structure of single-track railway bridge on the line Tišnov – Nové Město na Moravě. The task is bridging the local road by a bridge structure with one field. Length of the bridge is 40 m.