Precast, prestressed concrete panels (PCPs) and cast-in-place (CIP) concrete slabs are commonly used in Texas and elsewhere. Because PCPs are placed between bridge girders, and CIP concrete slabs are cast over the PCPs, PCPs act as formwork, cost and time for construction can be reduced. However, current designs may be further optimized if it can be shown that the reinforcement in the CIP deck can be reduced. Another issue involves cracking of PCP during fabrication and transportation to the site. The goal of this dissertation is to recommend changes to the CIP-PCP bridge decks that will lead to more cost-effective bridges. The first phase of the research is to suggest an optimized reinforcement layout for cast-in-place (CIP) slabs. Because the capacity of these decks is much greater than the design loads, a decrease in top-mat reinforcement will have minimal effect on the margin of capacity over design loads. Two options were selected, reduced deformed-bar reinforcement; and reduced welded-wire reinforcement. These two options are evaluated through restrained-shrinkage tests and field applications. The second phase of this dissertation is to reduce cracks in precast, prestressed concrete panels (PCPs) which occur during fabrication, handling, and transportation. Most cracks in PCPs are collinear (occur along the strands). They can be reduced in two ways. The first is to reduce initial prestress. The second is to place additional transverse reinforcement at edges. / text

Following development of rectangular prestressed, precast concrete panels (PCP) that could be used as stay-in-place formwork adjacent to expansion joints in bridge decks, the Texas Department of Transportation (TxDOT) initiated a research effort to investigate the use of PCP units at skewed expansion joints. The fabrication of trapezoidal PCP units was studied and the response of skewed panels with 45° and 30° skew angles was obtained. The panels were topped with a 4 in. thick cast-in-place (CIP) slab to complete the bridge deck. Specimens with 45° skew performed well under service and overload levels. The deck failed in diagonal shear at loads well over the design level loads. However, two 30° specimens failed prematurely by delamination between the topping slab and the PCP. The cause of the delamination was insufficient shear transfer capacity between the PCP and CIP topping slab. For the specimens tested at a square end, the failure mode was punching shear at high loads for all specimens. The surface condition of the PCP was specified to have a “broom finish” and the panel was to have a saturated surface dry (SSD) condition so that PCP units would not leach moisture from the CIP topping slab. Neither of these conditions was satisfied in the two panels that failed prematurely. Although the panels were specified to have a broom finish, the panel surface had regions that were quite smooth. The objective of this research project was to reinvestigate the response of 30° PCP at an expansion joint following specified procedures for finish and moisture conditions. One specimen was constructed with a rectangular panel placed between two 30° skewed panels. These panels had a much rougher surface texture than the previously tested panels that failed in delamination. The skewed ends of the specimen were subjected to monotonically increasing static loads at midspan of the panel ends. The panels failed in diagonal shear and the response of the tested specimen confirmed that the panel surface roughness, and not the skew angle, caused delamination with the previously tested specimens. While TxDOT does not currently specify a minimum panel surface roughness, a surface roughness of approximately 1/4 in. is required in some codes for developing composite action. In addition, wetting the panels to a SSD condition prior to placement of the topping slab further enhances shear transfer between the topping slab and the PCP. / text

PC panel strengthening technique was developed in M.E.T.U. Structural Mechanics Laboratory in order to respond the need of practical and efficient pre-quake seismic strengthening procedures applicable to RC framed structures. The idea behind the method is simply to convert the non-structural infills into load bearing structural elements by gluing PC panels over the existing infill wall surface. The remarkable advantages of the procedure is not only the considerable amount of seismic performance improvement but also the simplicity of application, very low levels of disturbance to the occupants and most importantly, the applicability during service. A number of PC panel application parameters were experimentally investigated by previous researchers. The success of PC panel method on seismic performance improvement of RC frames with different aspect ratios was experimentally investigated in the present study. Total of fifteen, 1:3 scaled, one-bay, two-storey RC frames were tested in three various aspect ratio series. Constant axial load was applied to the columns and reversed cyclic load was applied in the lateral direction. Hollow brick v infilled frame and cast-in-place RC infilled frame were the lower and upper bound reference specimens, respectively. Seismic performance indicators such as response envelope curves, lateral load carrying capacities, cumulative energy dissipations, initial stiffness indicators and ductility values clearly showed the effectiveness of PC panel application over different geometry of RC frames of concern. Moreover, PC panel application either with rectangular or with strip shaped PC panels provided seismic performance improvement to be almost equal to that of cast-in-place RC infill application for all series. Equivalent diagonal strut concept was followed in analytical studies to simulate the infills of RC frame openings. The required strut material properties were estimated from total of eighteen individual wall panel tests. The bond-slip effect, due to utilization low strength of concrete and plain rebars, was also investigated and introduced to the analytical frame models. Non-linear push over analysis was performed for all specimens in OpenSees computer software. The analytical results were compared with that of experimental response envelopes.

The importance of seismic rehabilitation became evident with 1992 Erzincan Earthquake, after which a large number of reinforced concrete buildings damaged in recent earthquakes required strengthening as well as repair. In the studies related to rehabilitation, it has been realized that inadequate lateral stiffness is one of the major causes of damage in reinforced concrete buildings. Recently, economical, structurally effective and practically applicable seismic retrofitting techniques are being developed in METU Structural Mechanics Laboratory to overcome these kinds of problems. The strengthening technique proposed in this thesis is on the basis of the principle of strengthening the existing hollow brick infill walls by using high strength precast concrete panels such that they act as cast-in-place concrete infills improving the lateral stiffness. Also, the technique would not require evacuation of the building and would be applicable without causing too much disturbance to the occupant. For this purpose, after two preliminary tests to verify the proper functioning of the newly developed test set-up, a total of fourteen one-bay two story reinforced concrete frames with hollow brick infill wall, two being unstrengthened reference frames, were tested under reversed cyclic lateral loading simulating earthquake loading. The specimens were strengthened by using six different types of precast concrete panels. Strength, stiffness, energy dissipation and story drift characteristics of the specimens were examined by evaluating the test results. Test results indicated that the proposed seismic strengthening technique can be very effective in improving the seismic performance of the reinforced concrete framed building structures commonly used in Turkey. In the analytical part of the study, hollow brick infill walls strengthened by using high strength precast concrete panels were modelled once by means of equivalent diagonal struts and once as monolithic walls having an equivalent thickness. The experimental results were compared with the analytical results of the two approaches mentioned. On the basis of the analytical work, practical recommendations were made for the design of such strengthening intervention to be executed in actual practice.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Precast concrete panels reveal an important architectural and structural function for constructions, and their use has grown in Brazil. Previous studies indicate the panels contribution in reducing efforts and displacements in the main structure, resulting in more economical structures. This work analyzes the panels interaction with the main structure via numerical analysis by using the ANSYS Software, under the effect of lateral actions. Two analyses of one-floor structures are developed: one is constituted of vertical panels connected to the beam and the other one is constituted of horizontal panels connected to the columns, using SOLID65, SOLID45, SHELL63, BEAM4, BEAM44, TARGE170, and CONTA173 finite elements. Results show the importance of the contribution of panels towards the stiffness of the main structure, promoting a reduction in the structure s displacements. Such stiffness causes stresses in the panels and in the connectors, being the latter the most critical. Quite often these stresses are not considered in the structural project. In the second analysis, with the horizontal panels connected to the columns via plate connection, results show that the precast panels contribution to the stiffness of the main structure is highly significant and it is affected by the eccentricity of the connection with occurrence critical stress in the connections and increases as the plate s thickness decreases. The use of plates with greater thickness results in less stress, but they transfer lateral bending to the precast panels. The thermal effect s consideration implies in such a greater tensions in the panels how much in the connections and greater efforts of lateral bending in the panels. The panels contribution may be considered a design strategy, due to the fact that they produce an effective material economy by means of the possibility of reduction of column dimensions. / Os painéis pré-moldados de concreto apresentam função arquitetônica e estrutural importante para as edificações, tendo o seu uso intensificado no Brasil. Estudos anteriores mostram a contribuição dos painéis em reduzir os esforços e deslocamentos da estrutura principal, resultando em estruturas mais econômicas. Este trabalho avalia a interação dos painéis com a estrutura principal por meio de análise numérica utilizando o software ANSYS (versão 9.0), sob o efeito das ações laterais. São desenvolvidas duas análises de estruturas de pavimento único (galpão), uma constituída por painéis verticais fixados na viga e outra por painéis horizontais fixados nos pilares, utilizando-se os elementos finitos SOLID65, SOLID45, SHELL63, BEAM4, BEAM44, TARGE170 E CONTA173. Os resultados obtidos mostram que os painéis contribuem no enrijecimento da estrutura principal, promovendo uma diminuição dos deslocamentos da estrutura. Verifica-se, também, que este enrijecimento ocasiona solicitações nos painéis e nas ligações, sendo estas as mais críticas e, muitas vezes, não são consideradas no projeto estrutural. Na segunda análise, com os painéis horizontais fixados nos pilares por meio de chapas metálicas de ligação, os resultados mostram que a contribuição dos painéis na rigidez da estrutura principal é afetada pelo valor da excentricidade da ligação, com a ocorrência de tensão crítica nas ligações, a qual aumenta com o decréscimo da espessura da chapa. O uso de chapas com espessura maior resulta em menores tensões, mas transferem flexão lateral aos painéis. A consideração do efeito térmico implica em maiores tensões tanto nos painéis quanto nas ligações e em maiores esforços de flexão lateral nos painéis. A contribuição dos painéis pode ser considerada numa estratégia de projeto, uma vez que resulta em economias de materiais por meio da possibilidade de redução da dimensão dos pilares. / Mestre em Engenharia Civil